Supporting informations
Glycine-functionalized Fe3O4@TiO2:Er3+,Yb3+ Nanocarrier for
Microwave-triggered Controllable Drug Release and Study on
Mechanism of Loading/Release Process Using Microcalorimetry
Hongxia Peng, Bin Cui*, Weiwei Zhao, Yingsai Wang, Zhuguo Chang, Yaoyu Wang
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of
Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, School of
Chemistry & Materials Science, Northwest University, Xi’an 710069, PR China
Experimental section
Materials and Characterization
All the chemical reagents used in this experiment were of analytical grade and
were used without further purification. Ferric chloride hexahydrate (FeCl3·6H2O,
purity 99%), sodium acetate (CH3COONa, purity >99.0%), ethylenediamine (C2H8N2,
purity ≥98.0%), Ethylene glycol (purity 96.0%) were purchased from the Shanghai
Chemical Reagent Factory (Shanghai, China). Tetrabutyl titanate (C16H36O4Ti) and
isopropyl alcohol ((CH3)2CHOH, purity 99%) were purchased from National Reagent
Corporation (Shanghai, China). Glycine was purchased from the Shanghai Chemical
Reagent Factory (Shanghai, China). Etoposide (VP-16) was purchased from the
Jiangsu Hengrui Medicine Factory. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) was purchased from the Sigma Chemical Company. A
human breast cancer cell line (MCF-7) was purchased from the Key GEN
Biotechnology Company (Nanjing, China). Deionized water was used in all of the
experiments.
X-ray diffraction (XRD) patterns of the samples were measured using an AXS
D8 Advance Diffractometer (Bruker, Bremen, Germany) with Cu Kα radiation (λ =
0.15406 nm) at 40 kV and 40 mA. The morphologies and structures of the as-prepared
samples were inspected using a JEM 2010 transmission electron microscope.
Room-temperature Fourier-transform infrared (FT-IR) spectra of the samples,
mounted on KBr discs, were recorded using a Perkin-Elmer (Waltham, MA, USA)
100 S spectrometer. Ultraviolet–visible light (UV–vis) spectral adsorption values
were measured using a UV-1800 spectrophotometer (Shimadzu, Kyoto, Japan). The
up-conversion emission spectra of the samples were recorded with a Hitachi (Tokyo,
Japan) F-4500 fluorescence spectrometer. An adjustable laser diode (980 nm, 2 W)
was used as the excitation source. Magnetization measurements were performed at
300 K using an MPMS-XL-7 superconducting quantum interference device (SQUID)
magnetometer.
Drug release under microwave stimulation was controlled using an HBS-C
medical microwave apparatus (Human Biosystems Inc., Palo Alto, CA, USA), at a
working frequency of 2450±30 MHz and a microwave power of 0 to 150 W. The
thermodynamics of the drug loading and release system were measured using an
RD496-2000
Calvet
microcalorimeter
(Mianyang CAEP
Thermal
Analysis
Instrument Company, Mianyang, China). The microcalorimeter was calibrated using
the Joule effect, and its sensitivity was 64.28±0.04 uV/mW at 298.15 K. Absorbance
of MTT by treated cells in the MTT assay was measured using an RT-6000
microplate reader (Rayto Life and Analytical Sciences Co. Ltd., Shenzhen, China).
The electromagnetic parameters of the Fe3O4@TiO2:Er3+,Yb3+ nanoparticles were
measured using a N5230A vector network analyzer (Agilent Technologies, Santa
Clara, CA, USA) with the transmission and reflection mode in the 2 to 18 GHz band.
All the measurements were performed at room temperature.
Synthesis of the Fe3O4nanocomposites
Amino-functional magnetic Fe3O4 nanoparticles were prepared by the solvothermal
method [17]. Briefly, FeCl3·6H2O (1.0 g) was dissolved in ethylene glycol (30 ml)
to form a clear solution, followed by the addition of NaAc (2.0 g) and
ethylenediamine (6.5 g). The mixture was stirred vigorously for 30 min and then
sealed in a teflon-lined stainless-steel autoclave (50mL capacity). The autoclave was
heated to and maintained at 200 ◦C for 6 h, and then cooled to room temperature
naturally. The black products were washed several times with ethanol and finally
dried at 60 ◦C for 6 h. Then, the amino-functional Fe3O4 nanoparticles were obtained.
Supplemental figures
Figure S1 shows the XRD patterns of the Fe3O4, TiO2:Er3+,Yb3+ and
Fe3O4@TiO2: Er3+, Yb3+ nanoparticles. Figure S1 (curves a) shows that the magnetite
cores were well indexed to the cubic spinel structure of Fe3O4 JCPDS (No. 65-3107),
with good crystallinity. Figure S1 (curves b) shows that the diffraction peaks can be
readily indexed to the rutile type TiO2 nanostructure according to the standard JCPDS
(No. 21-1272). In the case of Fe3O4@TiO2:Er3+,Yb3+ (Figure S1 curves c), not only
show the characteristic diffraction peaks of cubic spinel Fe3O4, but there were also
3+
3+
obvious diffraction peaks indexed to the anatase phase of TiO502:Er
(PDF of phx10Fe3O4TiO
point,Yb
AA Smoothing
###
21-1272), which suggested the successful crystallization of TiO2:Er3+,Yb3+ on the
20 point AA Smoothing of Smoothed19_Sm
surface of the Fe3O4 nanoparticles. In addition, we detected no peaks
of other phases,
###
indicating that no reaction occurred between the core and the shell during the
synthesis process.
 Fe3O4
 TiO2
Intensity (a.u.)



(c)







(b)
(a)
10
Figure S1
20
30
40
50
2-theta (degree)
60
70
80
XRD patterns of the samples: (a) Fe3O4, (b) TiO2:Er3+,Yb3+ and (c)
Fe3O4@TiO2:Er3+,Yb3+
To investigate the hydrodynamic sizes and stability of magnetic nanocarriers,
the dried magnetic nanocarriers were redispersed in physiological saline to make
aqueous dispersions, and hydrodynamic sizes of nanocarriers were determined by
dynamic light scattering (DLS). The zeta potential of Fe3O4@TiO2:Er3+,Yb3+ and
Fe3O4@TiO2:Er3+,Yb3+-Glycine
is
shown
in
Figure
S2.
The
Fe3O4@TiO2:Er3+,Yb3+-Glycine nanocarriers have been proposed to have excellent
stability at pH 7 and to provide negative charge at the surface that can be used to
attach other biomolecules. The dispersion of nanocarriers in aqueous solution mainly
depends on the particle surface zeta potential, the particles have certain zeta potential
which produces electrostatic repulsion between particles. It will have a better
dispersion and dispersion stability when its absolute value is higher. For
Fe3O4@TiO2:Er3+,Yb3+-Glycine, owing to its several intrinsic properties, the Glycine
not only provides –NH2 but also gives them excellent water solubility, long time
stability against aggregation and biocompatibility.
The hydrodynamic sizes of nanocarriers at pH 5, pH 6 and pH 7 and mean
particle sizes measured by TEM are reported in Table 1. It was observed from DLS
analysis that the hydrodynamic size was only slightly altered in different pH values
leading to suspensions with a wider pH range of stability. The hydrodynamic size of
the nanocarriers is gradually decreased with decreasing pH value, and the
hydrodynamic sizes obtained from the DLS method were larger than the actual size of
the nanocarriers obtained with TEM results, which can be attributed to the presence of
few aggregates due to a lack of charge at this pH and the hydrophobic capping effect
of nanocarrier nuclei when dispersed in aqueous media
40
30
Zeta potential (mv)
20
10
0
-10
-20
3+
3+
Fe3O4@TiO2:Er ,Yb -Glycine
3+
3+
Fe3O4@TiO2:Er ,Yb
-30
-40
2
3
4
5
6
7
8
9
10
11
pH
Figure S 2. Zeta potential of (a) Fe3O4 and (b) Fe3O4@TiO2:Er3+,Yb3+-Glycine
Table 1. Experimental Results on Mean Particle Sizes Measured by TEM,
Hydrodynamic Sizes at pH 5, pH 6 and pH 7 by DLS.
Sample
mean particle
size by TEM
(nm)
hydrodynamic
size at pH 5
(nm)
hydrodynamic
size at pH 6
(nm)
hydrodynamic
size at pH 7
(nm)
49.6
50.6
51.8
52.2
50.8
50.1
51.4
51.8
Fe3O4@TiO2:Er3+,
Yb3+
Fe3O4@TiO2:Er3+,
Yb3+- Glycine
To investigate the up-conversion luminescent properties of Fe3O4@TiO2: Er3+,
Yb3+, Fe3O4@TiO2:Er3+,Yb3+-Glycine and Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16
nanocomposites, the up-conversion luminescent spectra was recorded at room
temperature. Figure S3 shows that the green emission band centered at 500~560 nm is
attributed to the 4S3/2→4I15/2 electronic transition of the Er3+ ions. The 660 nm red
emission is ascribed to the 4F9/2 → 4I15/2 transition of Er3+ ions [25]. Here, the role of
Yb3+ is sensitizer. The sensitization of Yb3+ ions can improve the conversion
efficiency of Er3+ ions significantly. This is because Yb3+ ions have large absorption
cross section near a wavelength of 980 nm and they can transfer the excitation energy
to the Er3+ ions nearby through resonance. The decreased up-conversion emission of
Fe3O4@TiO2:Er3+,Yb3+-Glycine (curves b) and Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16
(curves c) nanocomposites could be caused by introduced reactive amino groups and
drug at their surfaces, and leading to energy loss on the nanoparticles surface and
cause fluorescence quenching by the introduced organic groups [27]. Although the
up-conversion luminescent intensity of the Fe3O4@TiO2:Er3+,Yb3+-Glycine and
Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16 nanocomposites decreased, the up-conversion
luminescent emission intensity was still strong enough to permit bio-imaging [28].
ex=980 nm
4
4
F9/2 - I15/2
Intensity/a.u.
a
b
c
4
4
S3/2 - I15/2
450
500
550
600
650
700
Wavelength/nm
Figure S3 Upconversion emission spectra of (a) Fe3O4@TiO2:Er3+,Yb3+ , (b) Fe3O4@
TiO2:Er3+,Yb3+-Gly and (c) Fe3O4@TiO2:Er3+,Yb3+-Gly-(VP-16)
Magnetic measurements showed that pure Fe3O4, Fe3O4@TiO2:Er3+,Yb3+,
Fe3O4@TiO2:Er3+,Yb3+-Glycine
and
Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16
had
magnetization saturation values of 71.9, 41.2, 31.3 and 26.7 emu/g, respectively
(Figure S3). It is noteworthy that the Fe3O4@TiO2:Er3+,Yb3+-Glycine and
Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16 retains strong magnetization, indicating its
suitability for targeting and separation as a drug carrier. The saturation magnetization
of
Fe3O4@TiO2:Er3+,Yb3+-Glycine
and
Fe3O4@TiO2:Er3+,Yb3+-Glycine-VP16
nanocomposites occurred at 31.3 and 26.7 emu/g, which is smaller than that of the
Fe3O4@TiO2:Er3+,Yb3+ nanoparticles. This is likely due to the decreased proportion
of Fe3O4 in the nanocomposites. The magnetization was still strong enough to permit
targeting and bio-separation. Moreover, the Fe3O4@TiO2: Er3+, Yb3+-Glycine-VP16
nanocomposites show fast response to the external magnet and can be readily
re-dispersion occurred quickly with a slight shaking once the magnetic field was
removed (Figure S4, inset). These results show that the nanocomposites possess
excellent magnetic responsivity and redispersibility, which is important in terms of
their practical manipulation [28].
100
60
60
-1
M (emu g )
40
M (emu g-1)
80
40
a
20
b
c
d
0
a
b
c
d
-20
-40
20
-60
-200 -150 -100 -50
0
50 100 150 200
H (Oe)
0
-20
-40
-60
-80
-100
-10000
-5000
0
5000
10000
H (Oe)
Figure S4 Hysteresis Loops of (a) Fe3O4, (b) Fe3O4@TiO2:Er3+,Yb3+, (c)Fe3O4@TiO2:
Er3+,Yb3+-Gly and (d) Fe3O4@TiO2:Er3+,Yb3+-Gly-(VP-16)
O
O
O
H
OH
O
H
O
O
O
H
O
HO
OH
O
O
Figure S5 Anticancer Drug Etoposide (VP-16)