www.advhealthmat.de
www.MaterialsViews.com
FULL PAPER
Highly Potent Bactericidal Activity of Porous Metal-Organic
Frameworks
Wenjuan Zhuang, Daqiang Yuan, Jian-Rong Li, Zhiping Luo, Hong-Cai Zhou,*
Sajid Bashir, and Jingbo Liu*
Recent outbreaks of bacterial infection leading to human fatalities have been a
motivational force for us to develop antibacterial agents with high potency and
long-term stability. A novel cobalt (Co) based metal-organic framework (MOF)
was tested and shown to be highly effective at inactivating model microorganisms. Gram-negative bacteria, Escherichia coli (strains DH5alpha and XL1Blue) were selected to determine the antibacterial activities of the Co MOF.
In this MOF, the Co serves as a central element and an octa-topic carboxylate
ligand, tetrakis [(3,5-dicarboxyphenyl)-oxamethyl] methane (TDM8−) serves as
a bridging linker. X-ray crystallographic studies indicate that Co-TDM crystallizes in tetragonal space group P4 21m with a porous 3D framework.
The potency of the Co-TDM disinfectant was evaluated using a minimal bactericidal concentration (MBC) benchmark and was determined to be
10–15 ppm within a short incubation time period (<60 min). Compared with
previous work using silver nanoparticles and silver-modified TiO2 nanocomposites over the same time period, the MBC and effectiveness of Co-TDM
are superior. Electron microscopy images indicate that the Co-TDM displayed
distinctive grain boundaries and well-developed reticulates. The Co active
sites rapidly catalyzed the lipid peroxidation, causing rupture of the bacterial
membrane followed by inactivation, with 100% recycling and high persistence
(>4 weeks). This MOF-based approach may lead to a new paradigm for MOF applications in diverse biological fields due to their inherent porous structure, tunable
surface functional groups, and adjustable metal coordination environments.
Dr. H.-C. Zhou
Chemistry Department
Texas A&M University
College Station, TX 77843, USA
E-mail: zhou@chem.tamu.edu
Dr. W. Zhuang
Chemistry Department
Texas A&M University
College Station, TX 77843, USA
Dr. D. Yuan
State Key Laboratory of Structure Chemistry
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Fuzhou, 350002, P.R. China, and Chemistry Department
Texas A&M University
College Station, TX, 77843, USA
Dr. J.-R. Li
Chemistry Department
Texas A&M University
College Station, TX 77843, USA
1. Introduction
The recent outbreak of a fatal strain of
enterohemorrhagic Escherlia coli (E. Coli) in
Lower Saxony, Germany in May and June
of 2011 has demonstrated the importance
of clean water and the strategies involved
in purification and disinfection. Traditionally, disinfection treatments have utilized
numerous chemical agents,[1] such as the
use of phenol[2] and ethanol, mainly for
disinfection of hands[3] and surfaces,[4] and
sodium hypochlorite (bleach)[5] for potable
water disinfection. The main drawback of
chemical disinfectants is product breakdown[6] and lack of long-term stability.[7]
This has led to the development of ozone
treatment[8] and the use of ultraviolet or
gamma irradiation,[9] which are easier to
apply, but still gave rise to by-products,
some of which are toxic.[10,11]
Apart from chemical disinfectants or
irradiation/ozone treatment, the use of
silver metal has recently drawn increased
attention.[12] Silver is effective but expensive, therefore its use is limited in the
disinfection of water.[13] It has re-emerged
as the principal disinfection agent against
Dr. Z. Luo
Microscopy and Imaging Center and
Materials Science and Engineering Program
Texas A&M University
2257 TAMU, College Station, TX 77843, USA
Dr. S. Bashir
Chemical Biology Research Group
Texas A&M University-Kingsville
MSC 161, Kingsville, TX
78363 and Advanced Light Source Division
Lawrence Berkeley National Laboratory, USA
Dr. J. Liu
Chemistry Department
Texas A&M University
College Station, 77843, and Texas A&M University-Kingsville
Kingsville, TX, 78363
E-mail: jingbo.liu@tamuk.edu and Advanced Light Source Division,
Lawrence Berkeley National Laboratory, USA; E-mail: jlliu@lbl.gov
DOI: 10.1002/adhm.201100043
Adv. Healthcare Mater. 2012, 1, 225–238
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
225
www.advhealthmat.de
www.MaterialsViews.com
FULL PAPER
Gram-negative/Gram-positive microbes, particularly when
coated onto a core of titania (TiO2).[14] This technique has permitted economically viable use of silver, keeping costs down
due to the use of silver/titania nanoparticles, which afford
high surface area, low dosage and long-term stability.[15] In this
study, metal-organic frameworks (MOFs), which also contain
structured metal atoms similar to Ag/TiO2 nanoparticles, were
shown to inactivate E. coli effectively. MOFs have been widely
explored in applications such as small molecule capture, drug
delivery, imaging, and catalysis, but have rarely been studied
as a disinfectant. The putative mechanism for inactivation,
with potential for high potency and long-term stability, is via
rupture of the lipid membrane, causing cell death. These MOF
materials are crystalline compounds in which metal ions or
clusters are coordinated to organic ligands forming an interconnected pore system.[16] The difficulty of designing and preparing solid-state materials with pre-designated structures for
specific applications once posed a great challenge in materials
science. After two decades of exploration, it is now routine to
design and control a MOF structure precisely via tuning of the
inorganic and organic components, which are readily available
thanks to the power of organic synthesis.[17] One salient feature
of MOFs is their crystallinity, which allows facile determination of their crystal structures, facilitating adjustments to the
original design. Via this powerful strategy, various molecular
architectures (polygonal rings, polyhedral cages, and polymeric
structures) can be pre-designed and their fixed geometry and
cooperative stability can be tuned via modification of ligands.[18]
Through functionalization of the organic linkers, MOFs can be
designed to suit their end applications.[19] Although significant
amount of research on porous MOFs has been reported, most
of these materials are based on di-topic,[20] tri-topic,[21] tetratopic,[22] or hexa-topic[23] carboxylate ligands. In this research,
an octa-topic[24] carboxylate ligand has been conceived and prepared. Applications of MOFs are highly diversified[25] due to the
unique nature of their tunable porosity, high surface area and
structural diversity,[26] and include shape/size/enantio-selective
catalysis[27] and gas storage and separation for next generation
alternative energy solutions.[28] Nanoscale metal-organic frameworks for biomedical imaging and drug delivery have recently
been reported by Lin and co-workers.[29] Application of bimetallic MOFs in an emerging concept called “theragnostics”
has been investigated by Liu and Palakurthi.[30] Bactericidal
activity of copper MOFs has also been recently observed.[31] The
overarching goal of this research focuses on the development
and application of new materials for the betterment of public
health, exemplified by use of MOFs as disinfectants in drinking
water. Here, the antimicrobial activity of the MOF is measured, using the minimum bacterial concentration (MBC) as a
standard benchmark to determine efficacy of the disinfectant.
The unique porous structure, multifunctioning radicals, and
tunable properties, as discussed above for novel MOFs, contribute to its bactericidal efficacy against E. coli, which is compared against literature values for other class of disinfectants.
In this paper, a new Co-based metal-organic framework (CoTDM) was synthesized using an octa-topic carboxylate ligand,
tetrakis[(3,5-dicarboxyphenyl)-oxamethyl] methane acid (abbreviated as H8TDM) applying a facile hydro-solvothermal method.
The Co-TDM was demonstrated as a viable disinfectant with
high potency (10–15 ppm) toward inactivation of the Gram-negative bacteria, E. Coli, specifically the DH5alpha and XL1-Blue
strains. Structural characterization of the grown single crystals
was performed using instrumental techniques including X-ray
crystallography and transmission and scanning electron microscopy (T/SEM). The main results reported in this work focus on:
(a) Synthesis of the novel Co-TDM MOF via a bottom-up hydrosolvothermal method with optimized fabrication parameters;
(b) Analysis of textural and crystalline structure and elemental
composition using microscopic and spectroscopic techniques;
and (c) Application of Co-TDM as a potent bacterial disinfectant.
The originality of this work is two-fold: 1) fabrication of a novel
Co-based MOF with octa-topic ligands, and 2) documented ultralow minimal bactericidal concentration (MBC) against Gram-negative microbes with high efficacy and persistence. This approach
to using specific metal centers bound within an organic framework for disinfection of microbes provides a potential new method
to mitigate bacterial contamination in food and water, which represents a severe threat to public health and disease control.
2. Results and Discussion
2.1. Fabrication Optimization
The
tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane
acid
(H8TDM) ligand (Figure 1a) was synthesized in two steps (substitution and hydrolysis), following a similar procedure to that
Figure 1. Fabrication of Co-TDM via a bottom-up solvothermal method and its biological application to inactivating bacteria, a) Molecular structure of
the ligand tetrakis [(3,5-dicarboxyphenyl)oxamethyl] methane acid, H8TDM; b) TEM images of intact E. coli (left-side), schematic of interaction between
bacteria and Co-TDM (middle), and damaged E. coli (right-side).
226
wileyonlinelibrary.com
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
2.2. Crystalline Structure of Co-TDM
The structure of [Co4(H2O)2(TDM)(H2O)8] was determined by
X-ray crystallography, and was found as the tetragonal space
group P 4 21m (a = 20.078(4) Å, c = 11.252 (2) Å). The Co-TDM
adopts a distorted dimeric μ2-H2O-centered basic carboxylate
cluster [Co2(H2O)(O2CR)4(H2O)4] (Figure 2) as its secondary
FULL PAPER
previously reported.[32] Briefly, the generation process of Co-TDM
through a hydro-solvothermal approach aims to produce welldefined and highly crystallized coordinative compounds. This
octa-topic TDM8− ligand serves as the organic linker coordinating
with the Co central element. A mixture composed of dimethylformamide (DMF) with a small portion of de-ionized water was
used, which acted as both solvent and stabilizing agent. Pink crystals with a molecular formula of [Co4(H2O)2(TDM)(H2O)8] were
formed. The nucleation of Co-TDM crystal units was believed
to be promoted when the solvent molecules were evaporated
from the solution. This rapid nucleation favors the formation of
Co-TDM with controllable size and monodispersity, as shown
in the electron microscopy analyses. Because a complex can be
formed between the ligand anions (TDM8−) and cobalt metal cations (Co2+), the central particle growth is inhibited indefinitely
and can be terminated at a designated size. The TDM8− ligand
regulates the size and stability of Co-TDM crystals.
The liquid phase of the hydro-solvothermal fabrication is a
key step in the synthesis process, as it allows for more rapid
diffusion of reactants (by many orders of magnitude) than in
the solid phase. Due to the fast kinetics of the nucleation reaction, the synthesis can be performed at lower temperatures
(85°C) than are commonly used, with shorter treatment times
(24 h) and at ambient atmospheric pressure. The complex
formed from the metal ions and the functional groups of the
ligands via coordinated covalent bonds allow the important tunable porosity and geometry of the single crystals to be obtained
through control of the molecular size. We speculate that the
metal cation, Co2+, acts as a chemically active site to catalyze the
peroxidation of lipid membrane, weakening the membrane and
leading to lysis and inactivation of the microbe(Figure 1b).
Figure 3. a) The 3-dimensional framework of a Co-TDM single crystal
and the dumbbell-shaped open channels in the c direction, Co-centers
(magenta) are shown in their polyhedral geometries; b) Schematic
representation of the topology of Co-TDM, in which the [Co2(H2O)
(O2CR)4(H2O)4] SBUs act as four-connected nodes (magenta) and quaternary carbon atoms of TDM8− act as eight-connected nodes (green).
building unit (SBU). The coordination geometry of each cobalt
is octahedral. Every TDM8− is connected to eight cobalt centers,
acting as an octa-topic ligand (Figure 2). The pairs of Co2 clusters are bridged by the carboxylate groups from two different
TDM8− ligands and one μ2-H2O molecule to form a 3-dimensional porous framework (Figure 3a). Along the c axis, there
exist dumpbell-shaped open channels of 11 × 6 Å. To obtain an
in-depth understanding of the Co-TDM structure, topological
analysis was performed by defining [Co2(H2O)(O2CR)4(H2O)4]
SBUs as four-connected nodes and the quaternary carbon
atoms of TDM8− as eight-connected nodes. An unusual (4, 8)connected scu type net[33] was formed with a Schläfli symbol[34]
of {416.612}{44.62} (Figure 3b).[32]
2.3. Morphological Structure of Co-TDM and Bacteria
Both high-resolution transmission and scanning electron
microscopy (TEM and SEM) were employed to study the fine
structure of the crystals and their effect on bacterial membrane
integrity. The microscopy results indicated that the bacteria
were heavily damaged upon addition of the Co single crystals to
the cell culture media.
2.3.1. Transmission Electron Microscopic Analyses
of Co-TDM and Bacteria
Figure 2. The connection mode of the TDM8− anion and cobalt cations
displaying polyhedral geometry; Co-TDM crystallizes in tetragonal space
group P 4 21m with a porous 3D framework; hydrogen atoms are not
shown for simplification; the inset shows the dimeric μ2-H2O-centered
basic carboxylate cluster [Co2(H2O)(O2CR)4(H2O)4] (carbon, grey; oxygen,
red; cobalt, magenta).
Adv. Healthcare Mater. 2012, 1, 225–238
To understand the morphological changes in the bacteria upon
using Co-TDM as a disinfectant, a high-resolution transmission electron microscope equipped with X-ray energy dispersive
spectroscopy (EDS or EDAX) and electron energy loss spectroscopy (EELS) analytical tools was employed (Figures 4a–d). The
results (Figure 4a: intact DH5α) indicate that intact bacteria
have a distinctive outer membrane and well-defined flagella,
suggesting that the E. coli cell structure was well-preserved even
under high vacuum and subjected to the high energy electron
beam. E. coli co-incubated with Co-TDM lost their cellular cohesion (Figure 4a: damaged DH5α), with their outer membranes
being heavily damaged or destroyed. TEM morphological
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
227
www.advhealthmat.de
FULL PAPER
www.MaterialsViews.com
Figure 4. TEM morphological and EDS elemental composition analyses of intact and damaged E. coli: a) cell structure comparison of intact and damaged DH5α; b) cell structure comparison of intact and damaged XL1-Blue; c) EDS elemental analyses of destroyed DH5α cells, demonstrating leakage
of K and other elements present in E. coli cells. d) EDS elemental analyses of destroyed XL1-Blue cells (spots highlight the similar elemental distribution, showing the multi-atomic elements distribution inside and outside of the cell wall randomly). Inset in c,d) the dimeric cobalt cluster [Co2(H2O)
(O2CR)4(H2O)4] of Co-TDM used to inactivate the two strains of bacteria.
analyses also showed that the integrity of the XL1-Blue strain
control (Figure 4b: intact XL1-Blue) was similarly maintained
under high-energy electron beams and high vacuum, but the
treated XL1-blue bacteria (Figure 4b: damaged XL1-Blue) could
barely maintain their cell walls.
The above figures (Figure 4a and Figure 4b) indicates extensive blebbing (disintegration) of the membrane, condensation
of the nuclear material (region 2) and membrane lysis into the
extracellular matrix (region 3), however there is no indication
of incorporation into the cytoplasm (region 1), suggesting the
mode of reaction was through interaction with the outer wall/
membrane. Similar effects were observed for both strains; the
degree of damage for the XL1-Blue (LacIq strain) appeared to
be more extensive under the same treatment conditions.
These two strains of E. coli (DH5alpha and XL1-Blue) were
treated using ultralow doses of Co-TDM (10–15 ppm). Since
there is a high utilization of the Co active sites, larger quantities,
228
wileyonlinelibrary.com
as would be required for chemical disinfectants (as demonstrated in a previous study) were not necessary.[35] Co-TDM is
very effective due to its large reactive surface area and unique
chemical reactivity, which can inactivate bacteria with only a
short co-incubation period (<60 min) and with long-term efficacy. It also was found that Co-TDM was very stable even under
high energy electron beams. The tetragonal structure of the
Co-TDM single crystals was very well maintained and no structural collapse was observed.
The full utilization of Co at the surface of the samples
enhanced the bactericidal effects. Copper was detected and
attributed to use of Cu-grids to support the Co-TDM samples in
the TEM study. Upon incubation with Co-TDM, the elements
inside and outside (Figure 4c and Figure 4d) the E. coli cell
structure consisted of cations: sodium, potassium, calcium (Ca);
and anions: nitrogen, sulfur, phosphorus, chlorine. K leakage is
known to occur upon disruption of cellular respiration,[35] and
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
2.3.2. EELS Elemental Mapping of the Intact
and Damaged Bacteria
FULL PAPER
is thus an indicator of membrane damage. The other heteroatoms are found in proteins (DNA building blocks), indicating
inactivation through rupturing of the bacterial membrane; it
has been shown that Co interacts strongly with membranes
containing glycerophosphoryl moieties.[36] Membrane lysis
results in the release of the bacteria’s contents into surrounding
media, leading to the cell death. These observations correspond
with the TEM morphological images (Figure 4b), suggesting
that membrane damage of E. coli upon addition of the Co-TDM
crystals is the major cause of inactivation. The mode of action
appears to be six-fold and will be discussed in Section 2.6.
To understand the extent of damage to the E. coli cell wall, the
elemental composition was mapped using EELS (Figure 5a and
Figure 5b). The leakage of cations and anions towards the surface can be readily visualized through EELS results. The elemental map of the intact bacteria clearly depicts multi-atomic
elements distributed within the cell membrane (Figure 5a); no
leakage was detected. Upon addition of Co-TDM, the integrity
of the bacteria has failed; the heavy damage to the cell wall is
Figure 5. EELS elemental mapping analyses. a) E. coli DH5α and XL1-Blue controls, showing selected elements from the intact DH5α: multi-atomic
elements are evenly distributed inside the cell membrane, no leakage detected. b) Destroyed DH5α and XL1-Blue cells post Co-TDM inoculation (Note:
data for DH5α were selected for illustration: the membrane structure was completely destroyed, resulting in lysis and expulsion of nuclear and cytoplasmic components), showing selected elements from the damaged DH5α; the multi-atomic elements are randomly distributed inside and outside
of cell membrane (note that no distinguishable membrane remains).
Adv. Healthcare Mater. 2012, 1, 225–238
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
229
www.advhealthmat.de
www.MaterialsViews.com
FULL PAPER
seen from the random distribution of the elements throughout
the media (Figure 5b, selected elements (K, Na, N, and Cl)
shown as indicators of membrane collapse). Evidently, the
Co-TDM directly interacts with the cell wall of E. coli, causing
severe cellular damage. At complete disintegration, it is impossible to distinguish the boundary of bacteria and the incubation media, indicating complete collapse of the cell wall and
depolorization of the membrane. It is hypothesized that the
inducer (e.g. the chemical oxidant, antibiotic or transition metal
oxide nanoparticle or in our case the Co-TDM) can cause ion
channel formation resulting in depolarization of the cell membrane. This depolarization would result in monovalent ion
transport across the membrane and increased acidity, which
has been observed in the literature.[37] Furthermore, since
the pH difference (across the cell membrane) is partially sustained by the H+ pump, if the pumps were active, addition of
the inducer would not lead to an immediate drop in the difference in potential across the cell membrane (Δp). This sustained pH difference can be attributed to an increase in the
concentration difference of protons across the cell membrane
(Δ pH). In other words, the inhibitory effects of the inducer can
be partially offset by increased output of the H+ pump, keeping
the Δ pH values high to compensate for membrane depolarization until the concentration of the inducer becomes inhibitory.
Two phenomenological events would then be expected: a) a pHdependence of the inducer. Assuming the inducer is cobalt, it
has been shown that inhibition/stimulation toward lipid peroxidation (and presumably therefore membrane depolarization) is
pH-dependent;[38] and b) concentration-dependence, such that
above certain thresholds the difference in the membrane pH
(Δ pH) is insufficient to maintain membrane polarization. This
concentration dependence was also observed in our study (data
not shown) and other studies with cobalt salts and could also
partly explain the “blebbing” observed in the TEM images of
E. coli inhibited with Co-TDM. What is unequivocal is that the
Co-TDM leads to membrane depolarization and transport of
inorganic monovalent cations, cytotoxicity, and cellular inactivation. The mode of inactivation may involve several integrated
steps summarized and discussed in Section 2.6 (see Figure 8).
The mode of inactivation may involve in several steps such as:
i) weakening of the cell wall, ii) through lipid peroxidation; (ii)
cross-linking of protein-to-DNA leading to inhibition of certain DNA repair mechanisms; iv) disruption of ion transport
via membrane insertion; v) cation uptake in preference to Fe2+
resulting in disruption of scaffold-bound clusters and ironsulfur enzymes resulting in destabilization of iron homeostasis
by degrading the iron-sulfur cluster/sulfur mobilization (ISC/
SUF) regulatory pathways resulting in toxicity and inactivation; and vi) disruption of the membrane potential difference
through membrane insertion or formation of ion channels. Any
metal center capable of disruption of the iron balance, such as
Co2+, Ag+ or Cu+, would presumably be toxic, which recently
was demonstrated for copper.[39]
2.3.3. Scanning Electron Microscopy Analyses of Co-TDM
The surface morphology of the Co-TDM (Figures 6a–Figure 6d)
indicated that well-defined and highly crystalline metal-organic
frameworks were formed. The crystals displayed distinctive
230
wileyonlinelibrary.com
cubic geometry, with the areas averaging approximately 2.8 ×
2.5 × 1.2 μm3. These domains provided a significant advantage for peroxidation of the bacterial cell membrane when the
E. coli were treated using the Co-TDM. From the images (in
Figure 6a to Figure 6c), it can be seen that the single crystals
are highly stable under electron beam conditions. In general,
the grain boundary of the Co-TDM can also be easily distinguished, which favors peroxidation of the cell membrane, since
at the bulk level, we believe peroxidation may occur from these
boundaries. The EDS analyses indicated the Co cation metal
occurred at approximately Lα 0.776 keV and Kα 6.929 keV
(Figure 6d), respectively. In tandem with the X-ray analysis, the
highly crystalline and well-defined MOFs are also inherently
pure in formulation, which was confirmed by the EDS data. It
was also seen that the Co-TDM is highly porous and Co element
occupied a specific location within the frameworks, according
to the EDS mapping results. This ensures good reproducibility
and low deviance in the operability of the Co-TDM measurement when used as disinfectants, since each crystal provides
ultrahigh surface area and high active sites for peroxidation of
the membrane at the molecular level. The Co-TDM derived by
one-step hydro-solvothermal syntheses under mild conditions
displayed a high purity crystalline fraction. The synthetic reproducibility with high product purity/structure is essential to evaluating the dependence of proposed applications on the tunable
structure on MOFs.
2.4. Effectiveness of Bactericidal Performance of Co-TDM
To evaluate the bactericidal activity using Co-TDM, two commercially available strains of E. coli (DH5alpha and XL1-Blue)
were used as model microorganisms. The methodology has
previously been described.[40] Briefly, in control experiments,
the antibacterial activity of pure ligands and Co(NO3)2 showed
little or no antibacterial activity towards E. coli cells; zero or near
zero percent of E. coli cells were inactivated at concentrations
of 0.01-0.015 mg/mL (10-15 ppm). The antibacterial efficacy of
Co-TDM was assessed by incubating E. coli for different time
windows (Figure 7a and Figure 7b). Every hour, the absorbance
of E. coli was collected by ultraviolet-visible scan (300–800 nm)
and optical density (UV-Vis; OD600 nm) spectroscopy modes and
compared to that with no bacteria (blank). It was found the
absorbance was negligible, suggesting no growth of bacteria
under these operational conditions; indicating Co-TDM exhibits
highly efficient antibacterial performance, reducing the population to zero or near-zero. The minimal bactericidal concentration (MBC) ranging from 0.5–0.75 mg/50 mL (10–15 ppm)
with rapid inactivation of E coli was achieved shorter incubation
time than 1 hr. A possible reason for this phenomenon is that
Co-TDM has unique structure with octa-topic ligand, which
serve as the reservoir for the metal ions when interact with
the bacteria cell membrane. The large porosity, unique chemical reactivity, and high utilization of Co surface element also
contribute to the high potency of antibacterial activities of the
Co-TDM. The extent of Co2+ exposed to MOF motif’s surface
increases and thus, the interaction probability between Co and
the bacteria cell wall increases. Herein, the MOF moiety enables to achieve rapid antibacterial effectiveness. Additionally, the
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
FULL PAPER
Figure 6. SEM morphological and elemental analyses of Co-TDM crystals. a) Images of Co-TDM crystals with well-distinguished boundaries under low
magnification; b) Co-TDM crystals under high magnification showing the surface morphology with well-defined boundaries, allowing large amounts
of Co active sites; c) A single crystal to demonstrate the distinctive reticulate; d) EDS elemental analyses of the Co-TDM (principle emission at La line,
0.776 keV and Kα at 6.929 keV)
Co-TDM prepared using two solvents showed similar results,
suggesting the nature of solvents have negligible effects on the
bactericidal activity.
2.5. Comparison of Bactericidal Performance Using Co-TDM
and Other Materials
To evaluate the antimicrobial efficacy of the Co-TDM, a series
of experiments were implemented using commonly used
chemical disinfectant, silver nanoparticles, and nanocomposite
Ag-doped titania (TiO2). From the comparison (Figure 7c), it
Adv. Healthcare Mater. 2012, 1, 225–238
can be concluded that the Co-TDM displayed an intermediate
MBC (10–15 ppm) within a short treatment period (less than
60 min), while the Ag nanoparticles required a long incubation
time (>2 h, <10 ppm) with significant long-term stability.[41]
The Ag-TiO2 nanocomposite also displayed long-term but slow
antibacterial effects (<<10 ppm, 2 h) with the smallest MBC.[42]
On the other hand, previously documented chemical treatments (hypochlorite and phenol) exhibit instantaneous disinfection, which decreased with time with hypochlorite due to
oxidation.[35] It is critical to point out that both Co-TDM and
nanomaterials showed persistent antibacterial performance
under various treatment conditions; whereas, hypochlorite
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
231
www.advhealthmat.de
FULL PAPER
www.MaterialsViews.com
Figure 7. Efficacy evaluation of Co-TDM as a disinfectant to inactivate E. coli. a) Absorbance as a function of wavelength: DH5α was selected (XL1-blue
shows essentially equivalent data, data not shown); b) the absorbance as a function of treatment time: DH5 α was selected (XL1-blue shows essentially
equivalent data, data not shown). c) Comparison of bactericidal performance using Co-TDM, nanomaterials, and commonly used chemical disinfectants. Note all other comparative data was unused replicate data from a previous study.[40]
232
wileyonlinelibrary.com
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
2.6. Mechanistic Study of Bactericidal Activity
Our current and previous studies on antibacterial activity using
a series of materials suggested that an integrated mechanism
is applicable for bacteria inactivation, although the membrane
damage of E. coli upon addition of the biocidal agents is the
major cause. The synergetic effect of antimicrobial action was
observed and appeared to be six-fold, (1) Diffusion-directed
lipid-oxidation, (2) Direct interaction; (3) Reaction-oxygen species generation, (4) Cation transport interruption, (5) Chelation
effects, and (6) Membrane depolarization (Figure 8). (see Section 2.3.2.).
(1)Diffusion-directed lipid-oxidation: In this mechanism of bactericidal activity using Co-TDM, the diffusion of the MOF
motifs in the media will be a dominant step, along a chemical gradient 90 degrees to the plane of the cell wall within
5-4500 seconds, depending on the particle size and diffusion coefficient. The distance between the initial particles
and cell wall can be described by the following equation:
Adv. Healthcare Mater. 2012, 1, 225–238
FULL PAPER
did not exhibit long-term persistence. From the comparison
results (Supporting Information, table 2), it can be concluded
that the Co-TDM showed a rapid bactericidal effect with 100%
recycling of the engineered composite. The nanoparticles also
have significant effects over the long term. Although chemical
disinfectants have been commonly used over the last century[43]
as the “first wave” and provide almost instantaneous efficacy
against bacteria, their short-term stability limits their long-term
effectiveness. These short-comings have been addressed with
new engineered nanoparticles/composites as the “second wave”
of putative disinfectants,[44] focusing on nanoparticles either as
biofilms, sols or coatings as 1D/2D structures. Other 3D arrays
in the form of structured lattices or zeolite-like frameworks were
also shown to be partially effective as antibacterial agents with
MBCs in the range of 500–1000 ppm (Supporting Information,
Table 2).[45] The use of 3D structured arrays has recently been
updated through use of metal-organic frameworks for a variety
of applications[46] including the first application as a potential
disinfectant by the Liu group[40] and described in this study
as octa-topic carboxylic substituted frameworks. The measured MBC of 15 ppm (current study) is an order of magnitude
lower than use of organoboron framework (MBCs of 307 ppm,
Supporting Information Table 1) as an alternative approach to
engineered nanoparticles. The advantages of supramolecular
heterocyclics are the same as observed with structured nanoparticles, with the additional benefits of size selectivity as observed
with other macrocyclics such as cyclodextrins,[47] crown ethers,
and cryptands;[48] systems with the tunability of metal ion as
a redox centre, affinity probe or other optical, physical parameter. This approach has several advantages, namely utilization
of cobalt as the divalent cation, since divalent cobalt, unlike
atomic cobalt, is toxic to microbes, presumably through one of
the six mechanisms described previously, including possible
competition with iron cations and inhibition of de novo ironsulfur protein synthesis through inhibition of critical enzymes
and shutting down of critical metabolic pathways.
Figure 8. The mechanistic study of bactericidal activities using Co-TDM
single crystals as disinfectants: six steps synergistically contribute to the
bactericidal efficacy (details of lipid peroxide are described in 2.6 Mechanistic study of bactericidal activity; sample DNA structures obtained from
www.pdb.org).
x2 = 2Dt (1)
where x is the average value of the distance between the initial
particles and cell wall, 100 < x <300 μm, which is estimated
from experimental data; D is the diffusion coefficient, 1 ×
105 (cm2/s) for Co2+,[49] and t is the diffusion time, (s).
In the above equation, electrodynamic forces are ignored.
Aggregation of nanoparticles allows hydrophobic clusters to
permeate the lipid-bilayer either through ion channels (see (5)),
or by increased permeation in the lipid bilayer after lipid peroxidation.[50] The Co-TDM used as bactericidal agent created an
acidic atmosphere, which serves as homogeneous catalyst to
enhance the peroxidation of the lipid, causing cell death.
(2)Direct interaction: The phospholipid membrane structure
can be stabilized by cations (Ca2+ and Mg2+)[51] via ion binding between the anionic residues existing in the lipid head
groups and cations in the nutrient media. The phosphate
group (PO43−) is generally considered to be the preferred
cation binding site.[52] With introduction of Co-TDM, direction interaction can occur between the cobalt ion (Co2+) and
anion in (such as PO43−) at certain sugar residues; concurrently, the carboxylic (-COOH) group in the Co-TDM will
bind with Ca2+ or Mg 2+. Both interactions will lead to the
formation of Co3(PO4)2, which result in pro-oxidative stress
through generation of a reactive oxygen species (ROS, also
see mechanism (3)[53]) on the cell membrane. ROS-induced
stress and mechanical damage on the cell wall by the nanoparticles can then result in the weakening of the wall and lysis.
The observed changes of membrane structure from TEM
(Figure 4) and EELS (Figure 5) analyses are indicative of damage to the cytoplasmic membrane when bacterial populations
were treated with bactericidal agent, Co-TDM.
(3)Generation of reaction-oxygen species: It has previously
been demonstrated that Co2+ ions are capable of generating reaction-oxygen species (ROS).[52] Metal-assisted radical
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
233
FULL PAPER
www.advhealthmat.de
www.MaterialsViews.com
formation principally hydroxyl radicals (·OH) formation can
cause modifications to deoxyribonucleic acid (DNA), leading
to four distinct processes under the category of ROS-induced
damage; namely (3a/b) unzipping of the macromolecule; (3c)
enhanced lipid peroxidation and (3d) disruption of ion homeostasis. This ·OH formation will also result in (3c) alterations
to calcium (Ca2+) and thiol (SH) balance[53] and (3a) inhibition of DNA repair through cross-linking resulting in DNA
unzipping and fragmentation (which was observed in our
study).[54] In another study, it was demonstrated that cobalt
(in conjugation with iron) had a stimulatory effect on lipid
peroxidation in fatty acid micelles and phospholipid (phosphatidylethaolamine) liposomes, respectively,[55] noting that
similar fatty acids are found in the lipopolysaccharides layer
external to the peptidoglycan layer of Gram negative E. coli.[56]
This stimulatory effect was not observed in our study indicating that inhibition/stimulation may be concentration dependant and above threshold are inhibitory, as was observed
for membrane depolarization (also see §2.3.2 EELS Elemental
Mapping of the Intact and Damaged Bacteria).
intermediates.[63] Co-TDM toxicity is related to decreased iron
metabolism viz-a-via the [Fe-S] cluster assembly, which are
chelated by scaffold proteins involved in iron-sulfur protein
cluster biosynthesis, resulting in inactivation of related ironsulfur enzymes (ferrichrome reductase, aconitase, and tRNA
methylthio-transferase) leading to inhibition of certain critical proteins and toxicity.[64] Therefore, any metal nanoparticle system or chemical agents which can putatively interact
with the ISC/SUF system and cause oxidation of the cluster
proteins to the apoprotein form could be inhibitory. Recently,
it was shown that hydrogen peroxide also disrupt Isc by oxidizing [Fe-S] clusters assembled on/from the IscU scaffold,
the exception being the class of microbes, which are able to
switch over to another independent SUF pathway triggered
by OxyR regulon are not H2O2-sensitive due to another enzyme (isopropylmalate isomerase) being able to repair the
oxidative damage caused by H2O2 and also activate incipient Fe-S enzymes.[65] Hypothetically, therefore the Co-TDM
would be inhibitory in the former case but not the latter, unless isopropylmalate isomerase were also to be oxidized.
(4)Interruption of cation transport: Alternatively, Co-TDM interaction with the phospholipid layer affecting transport of
cations through the membrane would also led to a disruption of cation storage and membrane homeostasis resulting
in cytotoxicity and inactivation. Recently, lariant ethers with
varying dialkyl chains were shown to be toxic to E. coli, B.
subtilis, and S. Cerevisiae through interaction with the lipid
layer compared to bulk phases and carrier transport resulting
in toxicity.[57]
(6)Membrane depolarization: For Gram-negative microbes, inactivation is through membrane depolarization induction resulting in transport of monovalent cations such as K+ across
the cytoplasmic membrane of E. coli, but not divalent cations,
which was observed in our study. The source of this depolarization was not determined in the current study, but has been
postulated in the literature to occur between interactions with
the cytoplasmic membrane.[66] This interaction between the
inducer agent (e.g. nanoparticle) and membrane would result in the formation of ion channels, between the inner and
outer cell membrane,[67] similar to channels formed by induction of E. coli with inducers such as colicins.[68]
We further speculate that the Co-TDM motif would also be effective against Gram-positive microbes such as Staphylococcus
aureus, since those microbes have lipoteichoic acid in their
peptidoglycan layer,[58] which can serve as chelating agents.
This chelating agent may serve as a mechanism to inhibition potential lipid peroxidation akin to how lipid peroxidation can be minimized using ethylenediaminetetraacetic acid
(EDTA).[59] It was also shown that in the presence of cobalt,
the inhibitory effects of EDTA against lipid peroxidation
disappeared. It is plausible to speculate that any protective
effects of lipoteichoic acid could be negated by Co-TDM,
resulting in membrane damage through lipid peroxidation
as one potential mechanism for inactivation for both Gramnegative/positive microbes.[60]
(5)Chelation Effects: Intriguingly, chelation of metals is one
general mechanism whereby microbes exhibit tolerance to
certain metals, which ordinarily would be toxic. In E. coli,
for example the rcnA gene encodes for a membrane-bound
polypeptide facilitation nickel/cobalt efflux,[61] resulting in
competition between cobalt/iron for iron uptake at proteins,
which utilize iron as a co-factor. One class are iron-sulfur proteins, which in E. coli contain at least three separate [Fe-S]
cluster biosynthesis systems (genes names ISC, SUF enzymes named IscS, SufSE,)[62] with cysteine supplying the
atomic sulfur catalyzed by cysteine desulfurase in conjugation
with certain structural proteins. These proteins provide a variety of ancillary functions such as cluster assembly/access to
cluster precursors of [Fe-S] or iron chaperone or iron-carrier
234
wileyonlinelibrary.com
3. Conclusions
A Metal-organic framework, Co-TDM was composed of a unique
octa-topic carboxylate ligand and bimeric μ2-H2O-centered basic
carboxylate cluster [Co2(H2O)(O2CR)4(H2O)4]. The electron
microscopic images indicated that the Co-TDM was highly
crystallized and displayed distinctive grain boundaries and welldeveloped reticulates, allowing for rapid bacteria inactivation
with high potency. The rupture of the bacteria membrane led to
the cell death, determined by the EDS elemental mapping. Low
MBC (10–15 ppm) and rapid effectiveness of Co-TDM at inactivating Gram-negative bacteria E. Coli provide a new avenue for
MOFs applications in the biological realm.
4. Experimental Section
4.1. Materials Preparation
All chemicals, solvents, and reagents were obtained from VWR
International, (West Chester, PA) or Sigma-Aldrich (St. Louis,
MO) unless otherwise specified. Double-distilled, filtered
ultrapure water was used (Ultraopure™, Barnstead, Dubuque,
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
4.2. X-ray Crystallography
Single-crystal X-ray data for Co-TDM were collected using beamline 15-ID-B at the Advanced Photon Source, Argonne National
Laboratory. A Bruker Smart Apex II diffractometer equipped
with a low temperature device and synchronous X-ray energy
(λ = 0.41328 Å, silicon monochromated) and a wide arrayed
CCD (charge coupled device) detector were used to identify
the crystalline structure in high resolution. Due to an insertion
device in the beamline, an undulated narrow beam provided
the highest theoretical sensitivity as opposed to the use of traditional single-crystal X-ray diffraction measurements. Adsorption corrections were applied using the SADABS routine. The
structure was solved by direct methods and refined by fullmatrix least-squares on F2 with anisotropic displacement using
the SHELXTL software package.[69] Non-hydrogen atoms were
refined with anisotropic displacement parameters during the
final cycles. Hydrogen atoms connected to carbons were calculated in ideal positions with isotropic displacement parameters.
The diffused electron densities resulting from these residual
solvent molecules were removed from the dataset using the
SQUEEZE routine of PLATON and refined further using the
data generated.[70] The contents of the solvent region are not
represented in the unit cell contents in the crystal data. Crystallographic data (excluding structure factors) for the structure(s)
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC-835378. Copies of the data can be obtained free of charge
from www.ccdc.cam.ac.uk/data_request/cif.
4.3. Electron Nanostructural Characterization
A FEI Tecnai G2-F20 transmission electron microscope (FEI
Company, Hillsboro, OR) equipped with X-ray energy dispersive spectrometer (EDS) capabilities was employed to obtain
nanostructure information and crystalline phase data about the
colloid-derived nanoparticles. The instrument was operated in
TEM mode to obtain the high resolution images of Ag-NPs,
as well as scanning TEM (STEM) mode to obtain Z-contrast
STEM images using a high-angle annular dark-field (HAADF)
detector. The STEM mode utilizes a nanoscale electron beam
to analyze the chemical composition of the intact and damaged
bacterial cell structures. In both modes, the magnifications
were calibrated using commercial cross-line grating replica and
SiC lattice images.[71] The spherical aberration coefficient and
Adv. Healthcare Mater. 2012, 1, 225–238
resolution were approximately 2.0 mm and 0.27 nm, respectively. A probe size of 1 nm was used for EDS and STEM, at
150 mm camera length for the HAADF detector to collect for
Rutherford scattered electrons. Although a simplification, the
collected image contrast is related to the atomic number (Z)
squared, with elements with higher Z giving brighter contrast.
The FEI Tecnai G2-F20 microscope was also equipped with a
Gatan Imaging Filter (GIF) for electron energy loss spectroscopy (EELS). EELS was used to conduct the elemental mapping
to determine the composition distribution. The elemental distribution mapping was made using a standard three window
procedure, and the specific energy edges to image elements
were listed as follows: 401 eV (N K), 284 eV (C K), 200 eV
(Cl L2,3), 132 eV (P L2,3), 346 (Ca L3), 294 eV (K L3), 165 eV
(S L2,3), and 367 eV (Ag M4,5).
The surface morphology and texture of the Co-TDM materials were examined using a JEOL 6701F field emission scanning electron microscope (JEOL Ltd., Plano, TX). The surface
morphology and texture of the Co-TDM were also examined
by a Quanta 600 FEG field emission scanning electron microscope (FEI Company, Hillsboro, OR). FESEM is capable of generating and collecting high-resolution and low-vacuum images.
The instrument was equipped with a field emission gun and a
Schottky emitter. The voltage was controlled at 5 or 15 kV and
beam current at 100 nA. The chamber pressure and gun pressure were controlled to 3.5 × 10−5 Torr and 3.0 × 10−9 Torr for
high resolution. A thin layer (4.0 nm) of gold (Au) metal was
sputtered onto the sample surface to improve conductivity.
FULL PAPER
IA, referred to as distilled water), was used where water-based
solvents were necessary. All solvents were reagent or high performance liquid chromatography (HPLC) grade.
Single crystals with the formula [Co4(H2O)2(TDM)(H2O)8]
(abbreviated as Co-TDM) were prepared by mixing the ligand
H8TDM (0.05 g, 6.3 × 10−5 mol) with Co(NO3)2·6H2O (0.15 g,
5.2 × 10−4 mol). To adjust the acidity of solution, 20 drops of
2m HNO3 was added and N,N-dimethylformamide (DMF,
18 mL) was used as solvent. The solution was then sealed in a
20 mL vial and placed in an oven at 85 °C, where temperature
was maintained for 24 h.
4.4. Bactericidal Activity Evaluation
The bactericidal activity assays were performed using Escherichia
coli (E. coli; two commercially available strains, DH5alpha (Invitrogen, Grand Island, NY) and XL1-Blue, (Stratagene, Santa
Clara, CA were used) as the model organism. E. coli (5.0 mL)
were cultured in Difco™ nutrient lysogeny broth (LB, Miller
Luria-Bertani, Becton-Dickinson, Franklin Lakes, NJ) in an
incubator shaker (Innova® 43, Incubator Shaker Series, New
Brunswick Scientific, NJ) at 37 °C for 24 h. The cultured E. coli
were then diluted to 50 mL, into which the Co-TDM (0.50–
0.75 mg) were introduced to evaluate the bactericidal activities. After the treatment, an aliquot (0.5 mL) was collected and
tested using ultra-violet visible spectroscopy (Lambda 35 ultraviolet-visible (UV-Vis) spectrophotometer (PerkinElmer, Fremont, CA)) to identify the absorbance every hour in scan mode
between 300-800 nm with a slit width of 5 nm, scan rate of
1 nm/min and fixed optical density mode at 600 nm. Control
experiments were performed under identical conditions in the
absence of the Co-TDM, disinfectant (e.g microbes in LB). In
this study, we defined no growth of E. coli cells as indicating
full bactericidal activity and growth as indicating partial or no
bactericidal activity. These were compared to values previously
determined from studies with Ag, AgTiO2, and chemical disinfectant (phenol, sodium hypochlorite). Our previous experience
in determining number of colon forming units (CFU) per milliliter for E. coli using dilute samples (abs < 0.6) approximates to
1 OD unit corresponding to 109 bacteria per ml, therefore OD600
is an excellent implicit comparative technique in assessing
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
235
www.advhealthmat.de
www.MaterialsViews.com
FULL PAPER
bacterial viability, whereas plate dilution and counting of colonies is explicit and more accurate where the bacterial growth
phase in not known or new strains are used for the first time.
Supporting Information
Supporting Information is available from the Wiley Online Library or
from the author.
Acknowledgements
The US Department of Energy (DOE), the Office of Science (DOE
DE-SC0001015, DE-FC36-07GO17033, and DE-AR0000073), and the
National Science Foundation (NSF CBET-0930079 and NSF CBET0821370), are acknowledged for their financial support. Dr. J. Ying
from the National Natural Toxins Research Center at TAMUK is also
acknowledged for allowing us to conduct the bioassay. Dr. R. PerezBallestero, K. Chamakura are thanked for sharing unused MBC values
from a previous study (TAMUK), and the Microscopy and Imaging
Center and Materials Science and Engineering Program at TAMU and
the Departments of Chemistry at TAMU and TAMUK are acknowledged
for their technical support. The microcrystal diffraction of Co-TDM
was carried out with the assistance of Yu-Sheng Chen at the Advanced
Photon Source on beamline 15-ID-B at ChemMatCARS Sector 15,
which is principally supported by the National Science Foundation/
Department of Energy under grant number NSF/CHE-0822838. Use of
the Advanced Photon Source was supported by the U. S. Department of
Energy, Office of Science, Office of Basic Energy Sciences, under Contract
No. DE-AC02-06CH11357.
Received: December 12, 2011
Revised: January 23, 2012
Published online: March 21, 2012
[1] R. A. Minear, G. L. Amy, in Water Disinfection and Natural Organic
Matter: Characterization and Control, Vol. 649 (Eds: R. A. Minear,
G. L. Amy), American Chemical Society, Washington, D.C, USA
1996, Ch.1.
[2] J. Snow, Br. J. Anaesth. 1955, 27, 42.
[3] H. Chick, J. Hyg (Lond). 1910, 10, 237.
[4] Cooper, E. A, Biochem. J. 1912, 6, 362.
[5] W. W. Scott, K. E. Birkhaug, Ann. Surg. 1931, 93, 587.
[6] W. R Moorer, Int. J. Dent. Hyg. 2003, 1, 138.
[7] A. H. Walters, Ir. J. Med. Sci. 1948, 94, 273.
[8] a) L. Friberg, Acta Pathol. Microbiol. Scand. 1956, 38, 135;
b) L. Friberg, Acta Pathol. Microbiol. Scand. 1957, 40, 67.
[9] a) R. Sommer, W. Pribil, S. Appelt, P. Gehringer, H. Eschweiler,
H. Leth, A. Cabaj, T. Haider, Water Res. 2001, 35, 3109; b) A. D. Venosa,
C. W. B.Chambers, Appl. Microbiol. 1973, 25, 735.
[10] G. P. Vincent, J. D Macmahon, J. F. Synan, Am. J. Public Health
Nations Health. 1946, 36, 1035.
[11] a) M. Kristensen, K. Skadhauge, Acta Pathol. Microbiol. Scand. 1957,
40, 216; b) A. P. Black, J. B. Lackey, E. W. Lackey, Am. J. Public Health
Nations Health. 1959, 49, 1060.
[12] S. S. Block, in Disinfection, sterilization, and preservation (Ed:
S. S. Block), Lippincott Williams & Wilkins, Philadelphia, PA, USA
2001, Ch.1.
[13] W. K. Jung, H. C. Koo, K. W. Kim, S. Shin, S. H. Kim, Y. H. Park,
Appl. Environ. Microbiol. 2008, 74, 2171.
[14] H. Y. Song, K. K. Ko, L. H. Oh, B. T. Lee, Eur. Cells Mater. 2006, 11,
58.
236
wileyonlinelibrary.com
[15] J. Tian, K. K. Y. Wong, C. M. Ho, C. N. Lok, W. Y. Yu, C. M. Che,
J. F. Chiu, P. K. H. Tam, ChemMedChem 2007, 2, 129.
[16] a) O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi,
J. Kim, Nature 2003, 423, 705; b) S. Kitagawa, R. Kitaura, S. Noro,
Angew. Chem. Int. Ed. 2004, 43, 2334; c) J. J. Perry, J. A. Perman,
M. J. Zaworotko, Chem. Soc. Rev. 2009, 38, 1400; d) J. Rowsell,
O. M. Yaghi, Micro- and Mesoporous Mater. 2004,73, 3.
[17] a) D. L. Caulder, K. N. Raymond, Acc. Chem. Res. 1999, 32, 975;
b) S. Leininger, B. Olenyuk, P. Stang, Chem. Rev. 2000, 100, 853;
c) P. H.Dinolfo, J. T. Hupp, Chem. Mater. 2001, 13, 3113;
d) N. C. Gianneschi, M. S. Maser, C. A. Mirkin, Acc. Chem.
Res. 2005, 38, 825; e) M. A. Pitt, D. W. Johnson, Chem. Soc. Rev.
2007, 36, 1441; f) S. J. Lee, W. Lin, Acc. Chem. Res. 2008,
41, 521.
[18] a) J. R.Nitschke, J.-M. Lehn, Proc. Natl Acad. Sci. USA 2003,
100, 11970; b) R.W. Larsen, J. Am. Chem. Soc. 2008, 130, 11246;
c) S. Sato, Y. Ishido, M. Fujita, J. Am. Chem. Soc. 2009, 131, 6064;
d) Z. Lu, C. B. Knobler, H. Furukawa, B. Wang, G. Liu, O. M. Yaghi,
J. Am. Chem. Soc. 2009, 131, 12532; e) P. D. Frischmann, S. Guieu,
R. Tabeshi, M. J. MacLachlan, J. Am. Chem. Soc. 2010, 132, 7668;
f) B. H. Northrop, Y.-R. Zheng, K.-W. Chi, P. J. Stang, Acc. Chem.
Res. 2009, 42, 1554.
[19] a) T. Murase, S. Horiuchi, M. Fujita, J. Am. Chem. Soc. 2010, 132,
2866; b) K. Suzuki, S. Sato, M. Fujita, Nature Chem. 2010, 2, 25;
c) S. J. Lee, S.-H. Cho, K. L. Mulfort, D. M Tiede, J. T. Hupp,
S. T. Nguyen, J. Am. Chem. Soc. 2008, 130, 16828; d) C. J. Brown,
R. G. Bergman, K. N. Raymond, J. Am. Chem. Soc. 2009, 131, 17530;
e) T. S. Koblenz, J. Wassenaar, J. N. H. Reek, Chem. Soc. Rev. 2008,
37, 247.
[20] a) G. Férey, C. Mellot-Draznieks, C. Serre, F. Millange, J. Dutour,
S. Surblé, I. Margiolaki, Science 2005, 309, 2040; b) H. K. Chae,
D. Y. Siberio-Pérez, J. Kim, Y. B. Go, M. Eddaoudi, A. J. Matzger,
M. O’Keeffe, O. M. Yaghi, Nature 2004, 427, 523.
[21] a) W. J. Zhuang, S. Q. Ma, X. S. Wang, D. Q. Yuan, J. R. Li, D. Zhao,
H. C. Zhou, Chem. Commun. 2010, 46, 5223; b) L. Ma, W. Lin, J.
Am. Chem. Soc. 2008, 130, 13834; c) M. Eddaoudi, D. B. Moler,
H. L. Li, B. L. Chen, T. M. Reineke, M. O’Keeffe, O. M. Yaghi, Acc.
Chem. Res. 2001, 34, 319.
[22] a) D. Q. Yuan, D. Zhao, D. F. Sun, H. C. Zhou, Angew. Chem. Int.
Ed. 2010, 49, 5357; b) D. Zhao, D. Q. Yuan, D. F. Sun, H. C. Zhou,
J. Am. Chem. Soc. 2009, 131, 9186.
[23] a) A. G. Wong-Foy, A. J. Matzger, O. M. Yaghi, J. Am. Chem. Soc.
2006, 128, 3494; b) M. Dincă, A. Dailly, Y. Liu, C. M. Brown,
D. A. Neumann, J. R. Long, J. Am. Chem. Soc. 2006, 128,
16876.
[24] L. Q. Ma, D. J. Mihalcik, W. B. Lin, J. Am. Chem. Soc. 2009, 131,
4610.
[25] a) A. Bhan, E. Iglesia, Acc. Chem. Res. 2008, 41, 559; b) J. S. Seo,
D. Whang, H. Lee, S. I. Jun, J. Oh, Y. J. Jeon, K. Kim, Nature 2000,
404, 982; c) G. Li, W. B. Yu, Y. Cui, J. Am. Chem. Soc. 2008, 130,
4582.
[26] a) S. Noro, S. Kitagawa, M. Kondo, K. Seki, Angew. Chem. Int.
Ed. 2000, 39, 2082; b) X. Lin, I. Telepeni, A. J. Blake, A. Dailly,
C. M. Brown, J. M. Simmons, M. Zoppi, G. S. Walker, K. M. Thomas,
T. J. Mays, P. Hubberstey, N. R. Champness, M. Schroder, J. Am.
Chem. Soc. 2009, 131, 2159.
[27] a) H. Furukawa, N. Ko, Y. B. Go, N. Aratani, S. B. Choi, E. Choi,
A. O. Yazaydin, R. Q. Snurr, M. O’Keeffe, J. Kim, O. M. Yaghi, Science 2010, 329, 424; b) L. Q. Ma, D. J. Mihalcik, W. B. Lin, J. Am.
Chem. Soc. 2009, 131, 4610.
[28] a) A. Rit, T. Pape, F. E. Hahn, J. Am. Chem. Soc. 2010, 132, 4572;
b) B. Birkmann, R. Fröhlich, F. E. Hahn, Chem. Eur. J. 2009, 15, 9325;
c) T. Liu, Y. Liu, W. Xuan, Y. Cui, Angew. Chem. Int. Ed. 2010, 49,
4121.
[29] J. D. Rocca, D. Liu, W. Lin, Acc. Chem. Res. 2011, 44,957.
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238
www.advhealthmat.de
www.MaterialsViews.com
Adv. Healthcare Mater. 2012, 1, 225–238
[58] S. Morein, A.-S. Andersson, L. Rilfors, G. Lindblom, J. Biol. Chem.
1996, 27, 6801.
[59] D. B. Wilson, A. Okabe, J. Bacteriol. 1982, 152, 1091.
[60] C. R. Woese, Microbiol. Rev. 1987, 51, 221.
[61] K. Kilinc, R. Rouhani, Biochem. Biophys. Acta 1992, 1125, 189.
[62] J. M. C. Gutteridge, FEBS Lett. 1983, 157, 37.
[63] A. Rodrigue, G. Effantin, M. A. Mandrand-Berthelot, J. Bacteriol.
2005, 187, 2912.
[64] a) F. Barras, L. Loiseau, B. Py, Adv. Microb. Physiol. 2005, 50, 41;
b) D. C. Johnson, D. R.Dean, A. D. Smith, M. K. Johnson, Annu. Rev.
Biochem. 2005, 74, 247; c) L. Loiseau, S. Ollagnier-de Choudens,
D. Lascoux, E. Forest, M. Fontecave, F. Barras, J. Biol. Chem. 2005,
280, 26760; d) P. J. Kiley, H. Beinert, Curr. Opin. Microbiol. 2003, 6,
181.
[65] a) S. Ollagnier-de-Choudens, Y. Sanakis, M. Fontecave, M. J. Biol.
Inorg. Chem. 2004, 9, 828; b) S. Ollagnier-de-Choudens, L. Nachin,
Y. Sanakis, L. Loiseau, F. Barras, M. Fontecave, J. Biol. Chem.
2003, 278, 17993; c) J. N. Agar, C. Krebs, J. Frazzon, B. H. Huynh,
D. R. Dean, M. K. Johnson, Biochemistry 2000, 39, 7856; d) C. Krebs,
J. N. Agar, A. D. Smith, J. Frazzon, D. R. Dean, B. H. Huynh,
M. K. Johnson, Biochemistry, 2001, 49, 14069; e) H. Ding, R. J. Clark,
Biochem. J. 2004, 379, 433; f) S. Ollagnier-de-Choudens, T. Mattioli,
Y. Takahashi, M. Fontecave, J. Biol. Chem. 2001, 276, 22604;
g) R. Balasubramanian, G. Shen, D. A. Bryant, J. H. Golbeck, J. Bacteriol. 2006, 188, 3182.
[66] C. Ranquet, S. Ollagnier-de-Choudens, L. Loiseau, F. Barras,
M. Fontecave, J. Biol. Chem. 2007, 282, 30442.
[67] a) S. Jang J. A. Imlay, Mol. Microbiol. 2010, 78, 1448; b) F. W. Outten,
O. Djaman, G. Storz, Mol. Microbiol. 2004, 52, 861; c) O. Djaman,
F. W. Outten, J. A. Imlay, J. Biol. Chem. 2004, 279, 44590;
d) U. Tokumoto, S. Kitamura, K. Fukuyama, Y. Takahashi, J. Biochem.
2004, 136, 199; e) M. Fontecave, S .O. Choudens, B. Py, F. Barras,
J. Biol. Inorg. Chem. 2005, 10, 713; f) G. Storz, L. A. Tartaglia, J.
Nutr. 1992, 122, 627; g) M. F. Christman, G. Storz, B. N. Ames,
Proc. Natl. Acad. Sci. U S A. 1989, 86, 3484.
[68] a) B. Labedan, L. Letellier, Proc. Natl. Acad. Sci. USA 1981, 78,
215; b) L. Letellier, B. Labedan, J. Bacteriol. 1984, 157, 789;
c) J. A. Fee, Mol. Microbiol. 1991, 5, 2599.
[69] M. E. Bayer, in Bacterial Outer Membranes Biogenesis and Functions,
(Ed: M. Inouye), John Wiley & Sons, Chichester, UK 1982, Ch. 6.
[70] W. A. Cramer, J. R. Dankert, J. Uratani, Biochem. Biophys. Acta 1983,
737, 17.
[71] G. M. Sheldrick, Acta Cryst 1990, A46, 467.
[72] a) P. V. D. Sluis, A. L. Spek, Acta Cryst. 1990, A46, 194; b) S. Ma,
D. Sun, J. M. Simmons, C. D. Collier, D. Yuan, H.-C. Zhou, J. Am.
Chem. Soc. 2008, 130, 1012.
[73] Z. P. Luo, Acta Materialia 2006, 54, 47.
[74] S. Lenaghan, C. Sundermann, J. Eukaryot. Microbiol. 2005, 52, 7S.
[75] M. Nirmala, A. Anukaliani, Physica B: Cond. Matt. 2011, 406, 911.
[76] K. Delgado, R. Quijada, R. Palma, H. Palza, Lett. Appl. Microbiol.
2011, 53, 50.
[77] H. Palza, S. Gutiérrez, K. Delgado, O.Salazar, V. Fuenzalida,
J. I. Avila, G. Figueroa, R. Quijada, Macromol. Rapid Commun. 2010,
31, 563.
[78] A. Lipovsky, A. Gedanken, Y. Nitzan, R. Lubart, Lasers Surg. Med.
2011, 43, 236.
[79] T. Jin, J. B. Gurtler, J. Appl. Microbiol. 2011, 110, 704.
[80] B. Aydin Sevinç, L. Hanley, J. Biomed. Mater. Res. B. Appl. Biomater.
2010, 94, 22.
[81] Y. Liu, L. He, A. Mustapha, H. Li, Z.Q. Hu, M. Lin, J. Appl. Microbiol.
2009, 107, 1193.
[82] M. A. Syed, U. Manzoor, I. Shah, S. H. Bukhari, New Microbiol.
2010, 33, 329.
[83] J. Song, H. Kong, J. Jang, Colloids Surf B: Biointerfaces 2011, 82,
651.
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
wileyonlinelibrary.com
FULL PAPER
[30] I. Medina-Ramirez, M. Gonzalez-Garcia, S. Palakurthi, J. Liu, in
Green Chemistry, (Ed: A. Luiz), InTech Publishers, Rijeka, Croatia,
2011, Ch.1.
[31] K. Wang, Z. Geng, Y. Yin, X. Ma, Z. Wang, CrystEngComm 2011, 13,
5100.
[32] A. Rajca, R. Padhmkumar, D. J. Smithhisler, S. R. Desai, C. R. Ross,
J. J. Stezowski, J Org Chem 1994, 59, 7701.
[33] a) O. Delgado-Friedrichs, M. O’Keeffe, O. M. Yaghi, Acta Crystallogr. A 2006, 62, 350; b) O. Delgado-Friedrichs, M. O’Keeffe,
O. M. Yaghi, PCCP 2007, 9, 1035; c) C. Borel, M. Hakansson,
L. Ohrstrom, CrystEngComm 2006, 8, 666; d) C. Tan, S. Yang,
N. R. Champness, X. Lin, A. J. Blake, W. Lewis, M. Schroder, Chem.
Commun. 2011, 47, 4487; e) L. Ma, D. J. Mihalcik, W. Lin, J. Am.
Chem. Soc. 2009, 131, 4610.
[34] V. A. Blatov, IUCr CompComm Newsletter 2006, 7, 4.
[35] K. Chamakura, R. Perez-Ballestero, Z. Luo, S. Bashir, J. Liu, Colloids
Surf. B: Biointerfaces 2011, 84, 88.
[36] A. C. MCLaughlin, C. Grathwohl, R. E. Richards, J. Mag. Res. 1969,
31, 283.
[37] a) E. L. Baldwin, J. A. Byl, N. Osheroff, Biochemistry 2004, 43, 728;
b) E. Kopera, T. Schwerdtle, A. Hartwig, W. Bal, Chem. Res. Toxicol.
2004, 17, 1452; c) C. P. Moorhouse, B. Halliweil, M. Grootveld,
J.M.C. Gutteridge, Biochim. Biophys. Acta, 1985, 843, 261.
[38] K. Kilinc, R. Rouhani, Biochem. Biophys. Acta, 1992, 1125, 189.
[39] S. Chillappagari, A. Seubert, H. Trip, O. P. Kuipers, M. A. Marahiel,
M. Miethke, J. Bacteriol. 2010, 192, 2512.
[40] K. Chamakura, R. Perez-Ballestereo, S. Bashir, Z. Luo, J. Liu, MRS
Fall 2010, Boston December 02 2010, private communications at
discussion session.
[41] X. Pan, I. Medina-Ramirez, R. Mernaugh, J. Liu, Colloids Surf B: Biointerfaces 2010, 77, 82.
[42] I. Medina-Ramirez, Z. Luo, S. Bashir, R Mernaugh, J. L. Liu, Dalton
Trans. 2011, 40, 1047.
[43] D. J. Weber, W. A. Rutala, Infect. Control Hosp. Epidemiol. 2006, 27,
1107.
[44] S. Bashir, K. Chanakura, R. Perez-Ballestero, Z. Luo, J. Liu, Int. J.
Green Nanotechnol. 2011, 3, 118.
[45] M. Melník, A. Auderová, M. HoĹko, lnorg. Chim. Acta 1982, 67, 117.
[46] A. C. McKinlay, R. E. Morris, P. Horcajada, G. Férey, R. Gref,
P. Couvreur, C. Serre, Angew Chem. Int. Ed. 2010, 49, 6260.
[47] E. M. Martin Del Valle, Process Biochem. 2004, 39, 1033.
[48] M. G. Voronkov, V. I. Knutov, O. N. Shevko, Chem. Heterocycl.
Compd. 1990, 26, 1077.
[49] A. C. F. Ribeiro, V. M. M. Lobo, J. J. S. Natividade, Chem Eng Data
2002, 47, 539.
[50] A. C. F. Ribeiro, V. M. M. Lobo, H. D. Burrows, A. J. M. Valente,
A. J. F. N. Sobral, A.M.Amado, C. I. A. V. Santos, M. A. Esteso,
J. Mol Liq. 2009, 146, 69.
[51] S. P. Denyer, G. S. A. B. StewartInt. Biodeterior Biodegrad 1998, 41,
161; P. N. Hoffmann, J. E. Death, D. Coates, in Disinfectants: Their
Use and Evaluation of Effectiveness (Eds: C. H. Collins, M. C. Allwood,
S. F. Bloomfield, A. Fox), Academic Press, London 1981, Ch.3.
[52] G. Cevc, D. Marsh, in Phospholipid Bilayers. Physical Principles and
Models, Vol. 5 (Ed: G. Cevc), Wiley-Interscience, New York 1987,
Ch. 11.
[53] C. P. Moorhouse, B. Halliweil, M. Grootveld, J. M. C. Gutteridge,
Biochim. Biophys. Acta 1985, 843, 261.
[54] M. D. Pulido, A. R. Parrish, Mutat. Res. 2003, 533, 227.
[55] a) M. Valko, H. Morris, M. T. Cronin, Curr. Med. Chem. 2005, 12,
1161; b) J. Q. Jarvis, E. Hammond, R. Meier, C. Robinson, J. Occup.
Med. 1992, 34, 620.
[56] a) E. L. Baldwin, J. A. Byl, N. Osheroff, Biochemistry 2004, 43,728;
b) E. Kopera, T. Schwerdtle, A. Hartwig, W. Bal, Chem. Res. Toxicol.
2004, 17, 1452.
[57] K. Kilinc, R. Rouhani, Biochem. Biophys. Acta 1992, 1125, 189.
237
FULL PAPER
www.advhealthmat.de
www.MaterialsViews.com
[84] H. Park, H. J. Park, J. A. Kim, S. H. Lee, J. H. Kim, Y. Yoon,
T. H. Park, J. Microbiol.Methods 2011, 84, 41.
[85] a) L. R. Martinez, G. Han, M. Chacko, M. R. Mihu, M. Jacobson,
P. Gialanella, A. J. Friedman J. D. Nosanchuk, J. M. Friedman,
J. Invest. Dermatol. 2009, 129, 2463; b) E. M. Hetrick, J. H. Shin,
H. S. Paul, M. H. Schoenfisch, Biomaterials. 2009, 30, 2782;
c) E. M. Hetrick, J. H. Shin, N. A. Stasko, C. B. Johnson,
D. A. Wespe, E. Holmuhamedov, M. H. Schoenfisch, ACS Nano
2008, 2, 235.
238
wileyonlinelibrary.com
[86] a) B. K. Sunkara, R. D. Misra, Acta Biomater. 2008, 4, 273; b) S. Rana,
J. Rawat, M. M. Sorensson, R. D. Misra, Acta Biomater. 2006, 2,
421.
[87] V. Zelenák, K. Györyová, D. Mlynarcík, Metal Based Drugs 2002, 8,
269.
[88] M. Melník, A. Auderová, M. HoĹko, lnorg. Chim. Acta 1982, 67,
117.
[89] Y. Liu, X. Xu, Q. Xia, G. Yuan, Q. He, Y. Cui, CrystEngComm 2011,
46, 2608.
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Healthcare Mater. 2012, 1, 225–238