Fabrics based on cotton containing
b-cyclodextrins provide the basis for drug delivery
systems, and polyaminocarboxylic acids (PACAs)
provide the new crosslinker
R.N.B.M
1
Table of Contents
Introduction: .................................................................................................................................................. 3
Pharmacological mechanisms for drug release: .................................................................................................. 4
Immediate release ....................................................................................................................................... 4
Triggered or delayed release......................................................................................................................... 4
Extended release ......................................................................................................................................... 4
Diffusion controlled release systems……………………………………………… ... .......................................................... 4
Characteristics and applications of cyclodextrin-based drug release systems: ........................................................ 5
Characterization methods of Cyclodextrin/Volatile Inclusion Complexes: ........................................................... 6
Spectroscopic Methods - UV-Visible Spectroscopy…………………………………. ...................................................... 8
Cyclodextrins in medical textiles: ...................................................................................................................... 9
Grafting of Cyclodextrins onto Textile Substrates:............................................................................................. 11
Novel approach for fixation of b-cyclodextrin on cotton fabrics: ......................................................................... 13
Fixation of b-CD onto cotton using PACAs:.................................................................................................... 14
Measurement methods: ................................................................................................................................ 15
Quantitative determination of β-cyclodextrin on the textile fabrics: ................................................................ 15
Qualitative determination of β-cyclodextrin on the cotton fabrics ................................................................... 15
Host–guest complexation of fixed b-cyclodextrin on cotton fabric with organic volatile gases ............................ 15
Results and discussion ................................................................................................................................... 16
Quantitative determination of β-cyclodextrin on the textile fabrics: ................................................................ 16
Qualitative determination of β-cyclodextrin on the cotton fabrics: .................................................................. 16
The effect of catalyst concentration (sodium hypophosphite): ........................................................................ 17
Host–guest complexation of fixed β-cyclodextrin on cotton fabric with organic volatile gases: ........................... 18
Conclusion ................................................................................................................................................... 20
Future trends ............................................................................................................................................... 20
References ................................................................................................................................................... 21
2
Introduction:
What are the benefits of exploring and developing textile materials for drug delivery systems?
In many cases, drug delivery methods like pills or injections aren't problematic, however, there may be other
scenarios where other delivery systems may be better.
As an example, tablets, pills, and capsules are forms of oral delivery systems where the drug is absorbed in the
stomach or intestines. Some drugs lose their activity when metabolised, so they cannot fulfill their purpose. Due to
this, relatively high doses may be necessary to achieve the desired effect, which may result in adverse or toxic
effects. When drugs are delivered through the skin, they bypass the liver, allowing lower dosages.
Furthermore, one can imagine situations where oral administration may not be appropriate or practical, e.g., in the
case of children, people with swallowing difficulties, or those with dementia. For these situations, transdermal and
in-vivo drug delivery systems can be beneficial
Furthermore, when medication is required for a long period of time, such a delivery system can possibly be
preferable to daily injections or pills. Compared to conventional drug delivery systems, advanced drug delivery
systems can provide several advantages in terms of safety and effectiveness by reducing dosage and dosing
frequency.
The design of prolonged drug dosage systems requires consideration of drug properties, pharmacological demands,
and reliability, while also keeping in mind that not all drugs work with such systems.
The textile materials combine a variety of materials and structures and are extremely versatile. There are a variety of
chemical, physical, and physical-chemical characteristics that are related to the properties and functionality of
textiles on micro-, nano-, meso-, and macroscopic scales.
There have been a variety of delivery methods developed over the years. One of the most popular is transdermal
patches. They are generally made up of multilayer systems, in which, in addition to an ointment or other drugcontaining substance, a membrane serves as a regulatory system.
Various factors, including biocompatibility, biostability, and biodegradability, are important in the development and
design of advanced textile antimicrobial drug delivery systems. Further, the release system should have the
capability of delivering the required amount of drug efficiently, precisely, and for a defined period of time
(controllability: dosage control, rate control, and time control), unlike conventional delivery systems.
A reactive derivative of cyclodextrin or a crosslinking agent can be used to fix CDs to textiles. The purpose of this
study is to examine the use of polyaminocarboxylic acids (PACAs) as novel crosslinking agents for the fixation of βCD on cotton fabrics.
Polyaminocarboxylic acids (PACAs) provide multiple benefits for cotton fabrics, including easy care, biostatic, fire
retardant, and improved dyeability.
3
Pharmacological mechanisms for drug release:
In general, textile drug delivery systems are characterized by three types of release:
Immediate release - Drugs in immediate release formulations are available in a relatively short period of time. In
order to achieve the desired effect, often a relatively high concentration is required, which is why the dosage is quite
frequent. In situations where immediate action is needed, this form of release is necessary.
Triggered or delayed release - In trigger and time-delayed release systems, drugs are released based on a
(external) trigger or stimulus. Depending on the design and the materials used, the release can be immediate or
slow. In delayed release systems, erosion, degradation, and dissolution are, apart from the matrix, determined by
factors such as pH, temperature, ionic strength, and even light. Drug dosages can be controlled autonomously by
triggered release systems over an extended period of time, allowing for precise dosage levels or more complicated
dosage patterns.
Extended release - As opposed to immediate release, extended release allows drugs to remain available at lower
concentration and for a longer period of time. Long-term release systems deliver the drug slowly over a long period
of time, either hours, days, or even years, resulting in fewer doses per day. In extended release systems, different
mechanisms are used to control the rate, such as diffusion, decomplexation, dissolution, ion exchange, erosion, and
degradation:
Diffusion controlled release systems incorporate the drugs directly into the polymer matrix of textile
fibers, hollow fibres, or fibres containing (micro)encapsulated drugs. The release rate of the drug depends on
the concentration gradient and diffusion coefficient in the polymer material. Fabrics containing cyclodextrins
serve as examples of controlled release systems that are decomplexation controlled. Drugs can be
incorporated into host molecules that are bound to textile fibres using decomplexation-controlled systems.
4
Characteristics and applications of cyclodextrin-based drug release systems:
Cyclodextrins are cyclic oligosaccharides, which form complexes with different organic substances such as drugs,
odors, and etc. Due to the ability for cyclodextrins (CDs) to form complexes with a variety of long-chain aliphatic or
aromatic molecules, like drugs, pesticides, hormones, detergents, fragrances, and vitamin B, makes them the most
attractive alternative. Some of the main reasons are:
1. Cyclodextrins are semi-natural as they are synthesized enzymatically (by Amylase) from strarch, a renewable
substrate.
2. Over the last decade, cyclodextrins have become widely available (over ten thousand tons per year).
Production has increased, reducing the price significantly.
3. cyclodextrins are considered safe from a toxicological perspective, and they are approved as food additives.
The most common cyclodextrins are α-, β-, and ɣ-cyclodextrin, which consist of six, seven or eight glucopyranose
units respectively. Because the units cannot freely rotate, cyclodextrins are not perfectly cylindrical, but conical. As a
result of sterical factors, smaller cyclodextrins do not exist. Despite the fact that more units of cyclodextrin exist,
they are not cylindrically shaped. The cavity is collapsed, which reduces the actual volume of the structure.
Some physicochemical properties of cyclodextrins
Based on the concept of size, CD complexation thermodynamics can be understood. In other words, the sizing and
shape of the included molecule, as well as critical factors in the van der Waals interaction, can be analyzed. The
smaller cavity diameter of a-CD compared to b-CD, combined with the van der Waals forces dependent on molecule
distance, means that the forces imposed by the complexation of extended chain molecules will be higher for a-CD
than for b-CD.
5
It is critical that the guest molecule is suitable to belong within the cavity, which can be integral or partial, in order to
form a complex with the CD (host molecule). A complexation doesn't form a covalent chemical bond between
molecules, nor is the compound enclosed within the macromolecular structure, which makes it a unique model for
models of compound release.
The selection of the correct CD for the possible formation of a complex is very important. It is easier to form stable
complexes with a-CD and b-CD for small molecules due to their size compatibility with the guest molecules. When
the guest molecule is too small, gCD becomes unfavorable because of the larger cavity. Process of inclusion complex
formation of drug and cyclodextrin:
Characterization methods of Cyclodextrin/Volatile Inclusion Complexes:
One of the most important features of CDs is the formation of inclusion complexes between the guests and CDs. For
quantitative analysis of the binding strength between the CD and guest, it is fundamental to determine the
formation constant (Kf) (also called stability or binding constant) of each inclusion complex.
Kf values are determined primarily by answering two types of questions:
1. Considering the encapsulation in absolute terms, the first question is: can a CD encapsulate a guest?
2. The second question is a comparative question, that is, what is the binding strength? Which inclusion
complex is most stable?
There are many ways to characterize inclusion complexes in solutions, and a lot of progress has been made in the
development of analytical methodologies, but few of these approaches could be applied to CD/volatile inclusion
complexes. Volatile compounds have low aqueous solubility mainly due to their low solubility in water.
Generally, the methods used can be divided into three groups:
6
•
Spectroscopic methods: UV-Visible (UV-Vis) spectroscopy, fluorescence spectroscopy and nuclear magnetic
resonance spectroscopy (NMR)
•
chromatographic methods: static headspace coupled to the gas chromatography (SH-GC) and highperformance liquid chromatography (HPLC)
•
calorimetric methods: isothermal titration calorimetry (ITC) and solubility studies. Lately, a new Total Organic
Carbon (TOC) method was also developed.
In order to characterize an inclusion complex, the initial step is to determine its stoichiometry and formation
constant (Kf). Based on literature studies, it appears that most of the inclusion complexes have a 1:1 (CD:guest)
stoichiometry:
All the inclusion complexes described in this review possess a 1:1 stoichiometry. In this case, the Kf could be
expressed as:
𝐾𝑓 =
𝐶𝐷
𝐶𝐷
𝐶𝐷
[ ]
[ ]
[ ]
[𝑖𝑛𝑐𝑙𝑢𝑠𝑖𝑜𝑛 𝑐𝑜𝑚𝑝𝑙𝑒𝑥𝑒]
𝐺
𝐺
𝐺
=
=
=
𝐶𝐷
𝐶𝐷
[𝐻𝑜𝑠𝑡] ∙ [𝐺𝑢𝑒𝑠𝑡]
[𝐶𝐷] ∙ [𝐺]
𝐶𝐷
𝐶𝐷
𝐶𝐷 2
([𝐶𝐷] 𝑇 − [ ]) ∙ ([𝐺] 𝑇 − [ ])
[𝐶𝐷] 𝑇 ∙ [𝐺] 𝑇 − [𝐶𝐷] 𝑇 ∙ [ ] − [ ] ∙ [𝐺] 𝑇 + [ ]
𝐺
𝐺
𝐺
𝐺
𝐺
•
[𝐺] − 𝑓𝑟𝑒𝑒 𝑔𝑢𝑒𝑠𝑡 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
•
[𝐺] 𝑇 − 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑔𝑢𝑒𝑠𝑡 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
•
[𝐶𝐷] 𝑇 − 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝐶𝐷 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
•
[𝐶𝐷] − 𝑓𝑟𝑒𝑒 𝐶𝐷𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛
7
Spectroscopic Methods - UV-Visible Spectroscopy
UV-Visible spectroscopy is commonly used for determining Kf using direct titration (a constant concentration of a
species (titrate) and increasing amounts of another species (titrant)).
A component of the complex (generally the CD) is gradually added to a fixed concentration of another component
(the guest). At the same time, the absorbance peak of the guest is monitored. There is no absorption from the CD.
The analysis is therefore simplified. In order to calculate the Kf value, the experimental results (absorbance values)
are compared and fitted to binding models. For determining Kf, many researchers still use outdated linear regression
methods -These include Benesi-Hildebrand, Scott and Scatchard plots:
Summary of the equations of linear regression methods:
The slope and intercept of these plots are used to determine a Kf value.
Formation constant (Kf, M-1) values of CD/volatile guest inclusion complexes determined by UV-Visible spectroscopy:
Guest
Fluorobenzene
structure
Method
β - CD
Benesi-Hildebrand
91
Benesi-Hildebrand
214
Benesi-Hildebrand
196
spectral displacement
2620
Toluene
Chlorobenzene
Carvacrol
When cyclodextrins (host) react with guest molecules, a stable complex may be produced with a high equilibrium
constant (Kf); for example, β-CD forms a very stable inclusion complex with Carvacrol 2620 [M-1].
8
Cyclodextrins in medical textiles:
In most studies involving cyclodextrin-textile delivery systems, β-cyclodextrins are used. Cyclodextrin molecules have
a cavity or interior that is rather hydrophobic, whereas the outer surface is hydrophilic. This hydrophobic interior is
mainly responsible for complex formation.
The CDs of the medical textiles can either be placed inside the body, on specific devices, or in direct contact with the
outside of the dermis. On the surface of the body, they take the form of:
i.
Pajamas consisting of an antiallergenic T-shirt and trousers
ii.
Knitted items with antipsoriatic properties: socks, elbow pads, knee pads; antimycotic underwear
iii.
Other undergarments that are antibacterial, anti-infectious, etc.
In addition to their main purpose of protecting and isolating the body from the environment, the textiles above also
have a direct therapeutic action, and are usually applied to the dermis. The terms "antiallergic" or "antipsoriasis"
refer to textiles that contain a drug or active ingredient (for example, plant extracts) for an antiallergic, antipsoriasis
treatment, the drug being released in response to a skin stimulus, such as sweating, friction, and skin enzymes.
In textiles, the fibrous polymers have a different reactivity than macromolecular compounds due to:
i.
High catenary orientation
ii.
Molecular organization at the supramolecular level
iii.
Free energy at the surface is high
It is possible, theoretically, to form temporary drug collectors on textile surfaces using:
i.
Hydrogels
ii.
Matrix systems
iii.
Polymer drug conjugates
iv.
CDs grafted on the textile fabric
v.
Multilayer systems
Most commonly, CDs are grafted onto textile supports, which are widely applicable in other fields as well.
9
Due to CD's bioadaptability and multi-functional properties, drug molecules have improved unwanted properties
when administered orally, rectal, nasally, ocularly, transdermally, and dermally. The hydrophobic characteristics of
CD-complexes allow them to deliver the drug only through an aqueous diffusion layer. Lipophilic barriers like stratum
corneum do not allow these complexes to penetrate the drug. Therefore, CDs play a very important role in the
pharmaceutical industry. This diagram illustrates how inclusion complexes are formed between the drug and CD and
how it is then absorbed by the body:
Using cyclodextrin as a functionalizer for finished cotton textiles:
Fiber
Effect
Antimicrobial
cotton
Fragrance, Antimicrobial
Nocturnal regulation of sleep and antioxidant properties
Insect repellent
10
Active Molecule
Octenidine dihydrochloride
Triclosan
Miconazole nitrate
Phenolic compounds
Silver
Essential Oils
Melatonin
Cypermethrin and Prallethrin
Grafting of Cyclodextrins onto Textile Substrates:
By complexing active ingredients with CDs, in numerous cases, their physicochemical properties are enhanced, their
release is controlled, their bioavailability is maintained, shelf life is extended, storage conditions are improved,
environmental toxicity is reduced, chemical stability is increased, oxidation is prevented, and resistance to bacteria is
favorable.
Incorporating active ingredients allows textile materials to perform specific functions, which can differ depending on
the application, such as medicine, cosmetics, and engineering. Reactive derivatives or suitable crosslinking agents
are used to fix CDs to textiles covalently. CDs are covalently fixed to textiles through the use of reactive derivatives
or suitable crosslinkers.
In order to integrate these active molecules into a textile substrate, CDs must be fixed in the fiber. CDs can be fixed
permanently into textile fibers through different methods, and sometimes cyclodextrins need to be modified to
allow them to be incorporated into the fabric as a first step.
Choosing the right method for fixing CDs into a textile substrate largely depends on the type of fiber and the
cyclodextrins' reactivity to the final application.
CD derivatives are grafted onto fibrous polymers by forming a bridge between the nucleophilic groups of the
polymers and CDs. The reaction conditions to graft CD onto a textile fabric are discussed in the following:
1. Reaction with epichlorohydrin (EPCL) - EPCL reacts with CD in alkaline medium at temperatures up to 60°C. In
limited amounts of water, hydrogels are generated, forming drug release systems
2. Reaction of monochlorotriazinyl-beta-cyclodextrin (MCT beta CD) with cellulose - The MCT beta CD exhibits
reactivity towards cellulose. Grafting on cellulose is a second-order nucleophilic substitution reaction
3. Esterification with polycarboxylic acids - Initially the polycarboxilic acids 1,2,3,4-BTCA, CTR and PAA were
tested for esterification with CDs. Polymer networks adhering well to polyester were obtained. This reaction
was used on polyester support to produce a multi-layered coating of drugs, for example an antibiotic using
MeCD, and to increase the amount of drug complexes. In this context, polycarboxylic acids serve as grafting
agents (crosslinking, grafting reagents). As well as the reagents presented, other CD grafting agents, such as:
divinyl sulfone, ethylene glycol diglycidyl ether, and polyethylene glycol, are also used.
4. Reaction with itaconic anhydride (Ianh) - The reaction with itaconic anhydride (Ianh) produces a derivative of
CD itaconate (CID) that can then be grafted onto cellulose. In the presence of sodium hypophosphite,
itaconic acid (IAC) is converted into Ianh. Nitric acid (1%) and ceric ammonium nitrate are then used to
create free radicals on the cotton fabric. Cotton is dried, then treated with CID, and then dried and cured
5. Reaction with acryloyl derivatives - CD dissolved in DMF is mixed by stirring with TEA and reacts with acryloyl
chloride dissolved in DMF, forming a derivative of acryloyl ester. The compound is then grafted onto a
polyamide-66 using (NH4)2S2O8 as promoter
11
Grafting of Cyclodextrins onto Textile Substrates:
Modification
Reaction with
epichlorohydrin (EPCL)
Reaction with itaconic
anhydride (Ianh)
Reaction of monochlorotriazinyl-betacyclodextrin (MCT beta CD) with cellulose
12
Reaction with acryloyl
derivatives
Novel approach for fixation of b-cyclodextrin on cotton fabrics:
Permanent fixation of cyclodextrins onto fibers is an interesting possibility of chemical modification of textile
materials. Such modifications are useful to prepare medical, personal care and home textiles. CDs are covalently
fixed onto textiles using reactive derivatives. Another approach for the covalent fixation the CDs on textiles is the use
of crosslinking agents.
The most conventional crosslinking agents for permanent fixation of CDs onto textiles are N-methylol compounds,
such as dimethylol urea and polycarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acids (BTCA) and citric acid Direct connection of the b-CD to the textile fiber via crosslinking:
In particular, CDs can be fixed onto cotton, wool, and polyester fabrics by use of polycarboxylic acids and their
combinations with salts of weak acids such as sodium hypophosphite (NaH2PO2):
A polyaminocarboxylic acid (PACAs) as a crosslinking agent for the fixation of b-CD onto cotton fabric has been
found to have multifunctional effects, including easy care, biostatic properties, flame retardance, and improved
dyeability.
In addition to formaldehyde-free durable press finishing agents, PACAs can also be easily synthesized based on
carboxylation of linear polyvinylamine with bromoacetic acid (under alkaline conditions).
Polyaminocarboxylic acids (b) are synthesized by carboxylating linear polyvinylamine (a) by bromoacetic acid under
alkaline conditions
13
Fixation of b-CD onto cotton using PACAs:
For the fixation of b-CD onto cotton using PACAs two methods have been applied:
1. stepwise fixation
2. simultaneous fixation
Moreover, polyaminocarboxylic acids (PACAs) with different degrees of substitution (DS: 9.1, 48.7 and 94.2 %) were synthesized and used for both fixation methods in
order to determine whether fixed β-CD molecules on finished cotton depend on how many carboxylic groups are present.
Stepwise fixation
Preparation of PACAs
finished samples were
immersed in a solution of
b-CD and sodium
hypophosphite
stirred for 5 min at room
temperature
were padded in a
laboratory padding dried
at 80C for 10 min and
cured at 160C for 5 min
rinsed for 5 min with
distilled water (40C)
dried at room
temperature,
conditioned (24 h, 20C,
65 % humidity)
Weighed
The fixation of cyclodextrin onto cotton fabric using PACAs is presented schematically:
14
Simultaneous fixation
PACA and b-CD were
employed on cotton
samples simultaneously
Each cotton fabric was
immersed in a solution
consisting of PACA+ bCD + sodium
hypophosphite
they were padded, dried
and cured in the same
way as described in
Stepwise fixation
Measurement methods:
The following measurements were performed after β-CD was fixed onto cotton using PACAs:
1. Quantitative determination of β-cyclodextrin on the textile fabrics
2. Qualitative determination of β-cyclodextrin on the cotton fabrics
3. Host–guest complexation of fixed b-cyclodextrin on cotton fabric with organic volatile gases
Quantitative determination of β-cyclodextrin on the textile fabrics:
In order to determine the overall amount of CD fixed on cotton textile, gravimetric weight measurements are taken
before and after the completion of PACA and CD. The relative weight increase (Wrel) of the treated samples was
measured by the following equation:
%𝑊𝑟𝑒𝑙 = 100 ∙ (
𝑊𝑓 − 𝑊𝑖
)
𝑊𝑖
stepwise fixation
simultaneous fixation
𝑊𝑖 → cotton sample finished only with PACA
𝑊𝑓 → identical sample after the additional
fixation of β-CD
𝑊𝑖 → fixation of β-CD and PACA only gives the sum of the fixed PACA
and b-CD and PACA with the weight of the cotton sample
𝑊𝑓 → identical sample after treatment with PACA and β-CD
Qualitative determination of β-cyclodextrin on the cotton fabrics
The presence of the b-cyclodextrin molecules on the cotton samples simultaneously finished with b-CD and PACA
was qualitatively determined using phenolphthalein. The color of alkaline solution of phenolphthalein is carmine red
and changes to colorless in the presence of b-cyclodextrin.
Host–guest complexation of fixed b-cyclodextrin on cotton fabric with organic volatile gases
β-CD molecules fixed on cotton fabrics (the cotton fabric finished simultaneously) with guest molecules were
investigated on their ability to complex in gas phase with toluene molecules:
PACA (DS 48.7 %)
and b-CD (4 %
w/v)
cotton finished
just with PACA
(DS 48.7 %)
subjected to toluene,
cyclohexene,
cyclohexene- 1-one
and chlorobenzene in
a desiccator for 12
days, at ambient
untreated cotton
fabric (original
sample)
Measuring complexation with
organic volatile compounds
15
reflective absorbance (directly
on the fabrics) using UV– VisSpectroscopy
Results and discussion
Quantitative determination of β-cyclodextrin on the textile fabrics:
The carboxylic groups of PACA of finished cotton react with the hydroxyl groups of b-CD. On the fabric, the amount
of fixed b-CD molecules depends on how many carboxylic groups there are on the cotton. Consequently, the
carboxylic groups present in the lowest amounts (9.1%) lead to the lowest fixation yield of b-CD.
Relative weight increase (Wrel) after fixation of b-CD on the samples finished with PACAs of different DS values:
Stepwise fixation
Simultaneous fixation
DS- 94.2%
DS- 48.7%
DS- 9.1. %
Qualitative determination of β-cyclodextrin on the cotton fabrics:
Phenolphthalein can be used to qualitatively determine CD presence - The color of phenolphthalein, which is
carmine red in the absence of CD molecules, changes to colorless when CD molecules are present:
Phenolphthalein
absence
of CD molecules
carmine red
Phenolphthalein
CD molecules
are present
colorless
In addition to color change, the speed at which phenolphthalein changes color in samples is important: with higher
contents of b-CD, it is expected to be faster. A specific concentration of b-CD and PACA resulted in the following
change in color from carmine red to colorless:
𝑃𝐴𝐶𝐴 (𝐷𝑆 94.2%) > 𝑃𝐴𝐶𝐴 (𝐷𝑆 48.7%) > 𝑃𝐴𝐶𝐴 (𝐷𝑆 9.1%)
In other words, by increasing the degree of substitution (DS) in PACA, higher amounts of b-CD have been fixed on
the cotton textile.
16
The effect of catalyst concentration (sodium hypophosphite):
Fixation efficiency may be affected by the concentration of catalyst (sodium hypophosphite): salts of weak acids,
such as sodium hypophosphite (SHPI), can act as catalysts for the esterification reaction. sodium hypophosphite
(NaH2PO2) serves as a catalyst for esterification reactions between PACA and cotton, and between PACA and CD.
The influence of catalyst concentration (sodium hypophosphite) on indirect fixation and direct fixation of b-CD on
cotton fabric:
PACAs of different degrees of substitution were grafted with b-CD (4 % w/v) at a given concentration (5 % w/v) using
sodium hypophosphite.
Stepwise fixation
Simultaneous fixation
DS- 94.2%
DS- 48.7%
DS- 9.1. %
These graphs allow us to draw and analyze the following conclusions:
1. Increasing the amount of sodium hypophosphite increases fixation yield.
2. A plateau occurs at concentrations greater than 60 g/l.
3. Adding catalyst to PACA with a low DS value (9.1 and 48.7%) leads to a slight increase in fixation yield,
whereas in the case of PACA with a DS value of 94.2 %, the fixation yield grows sharply.
17
Host–guest complexation of fixed β-cyclodextrin on cotton fabric with organic volatile gases:
Using cyclohexene, cyclohexene-1-one, chlorobenzene, toluene as guest molecules in gas phase, the complexation of
b-CD molecules fixed on cotton fabrics was investigated.
guest molecules
cyclohexene-1-one (or 2cyclohexen-1-one)
Toluene
Chlorobenzene
Cyclohexene
structure
polar or nonpolar
nonpolar
nonpolar
Average Molecular
Weight [g/mol]
96.129
92.1384
There is a large electronegative
difference between carbon and
chlorine, which makes it polar.
nonpolar
112.56
82.143
due to the host–guest properties of cyclodextrin molecules and the specific orientation of the guest molecules, they
are able to incorporate guest molecules based on size and hydrophobicity. Inclusion complexes do not break or form
covalent bonds during formation. When first molecules get into the lipophilic cavity of CD, they are immediately
replaced by the more favored guest molecule, which is less polar than the first molecules.
In the gas phase, cyclodextrin can form stable inclusion complexes with volatile organic compounds. The 240-243 nm
peak in the UV-Vis spectra of cotton finished with PACA and b-CD can be explained by the complexation between
toluene and fixed b-CD on the cotton fabric. There is no evidence for these signals in the spectrum of the original
cotton, the cotton which was only finished with PACA, and also with PACA and b-CD. Similar results were observed
for other volatile organic molecules the blanks exposed to the gases did not exhibit a peak in UV-spectroscopy.
Reflective absorbance of cotton samples after 12 days of exposure to toluene gas:
toluene gas
after 12 days of exposure to
cotton fabric finished simultaneously with PACA (DS 48.7 %) and bCD (4 % w/v)
cotton finished just with PACA (DS 48.7 %)
untreated cotton fabric (original sample)
240-243 nm peak - complexation of toluene
with the fixed b-CD on the cotton fabric
18
In the cotton fabric treated simultaneously with PACA (DS 48.7%) and b-CD (4 % w/v) the signals increase with time
due to complexation from the gas phase of cyclohexene, cyclohexene-1-one, chlorobenzene, and toluene.
cotton fabric treated simultaneously with PACA (DS
48.7%) and b-CD (4 % w/v)
gas phase of
cyclohexene-1-one
Toluene
Chlorobenzene
Cyclohexene
after 12 days of exposure
The signal increases and reaches a maximum value, which indicates that the complex has been formed. These
absorbances can be used to determine the amount of cyclodextrin present on cotton.
The rate of complex formation in the experimental conditions is mainly determined by diffusion processes in the gas
phase of the examined substances.
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Conclusion
When tests were performed to determine the change in reflective absorbance with time, these reflectances allowed
calculation of the amount of cyclodextrin attached to cotton. Molecular extinction coefficients of the different
complexes formed are unknown. In order to get information about the absorption of complexes in this environment,
further experiments are necessary.
The polyaminocarboxylic acids (PACAs) provide a multi-functional finish to cotton textiles such as ease of care and
flame retardancy. As well, they can also be used as anchor molecules to fix cyclodextrins on cotton. The fixation yield
of PACA varies with the number of carboxylic groups. By using PACA as crosslinking agents, cyclodextrins can be
easily fixed to cotton textiles.
Future trends
For textile drug delivery systems to meet pharmaceutical needs, special production facilities and adequate
environmental and safety measures are necessary. Suitable minimal application techniques, such as nozzles or digital
finishing technology, are capable of meeting these demands and of increasing efficiency and competitiveness. It will
then be possible to introduce the technology into the textile industry. In addition to using these technologies in
advanced drug textile delivery systems, cyclodextrins bearing textiles or fibres may also be used for environmental
protection, separation technology, and functional textiles like sensors, antibacterial and antifungal textiles (hygienic
textiles) or textiles that release fragrances and adsorb unwanted odours.
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References
1. A novel approach for fixation of b-cyclodextrin on cotton fabrics, Vahid Ameri Dehabadi Hans-Ju¨rgen
Buschmann Jochen Stefan Gutmann - 26 August 2013 / Accepted: 9 October 2013
2. The Role of _-Cyclodextrin in the Textile Industry—Review, Marina Isidori, Margherita Lavorgna and Rosa
Iacovino, 30 June 2020; Accepted: 8 August 2020; Published: 9 August 2020
3. Applications of cyclodextrins in medical textiles — review, Cezar-Doru Radu , Oana Parteni , Lacramioara
Ochiuz -2016 Elsevier B.V. All rights reserved
4. Smart textiles for medicine and healthcare, Edited by L. Van Langenhove - First published 2007, Woodhead
Publishing Limited and CRC Press LLC © 2007, Woodhead Publishing Limited
5. Characterization of Cyclodextrin/Volatile Inclusion Complexes: A Review, Miriana Kfoury , David Landy and
Sophie Fourmentin - 30 April 2018; Accepted: 15 May 2018; Published: 17 May 2018
6. Cyclodextrins: Structural, Chemical, and Physical Properties, and Applications, Benjamin Gabriel Poulson 1 ,
Qana A. Alsulami 2 , Abeer Sharfalddin 2 , Emam. F. El Agammy 3, Fouzi Mouffouk 4 , Abdul-Hamid Emwas 5 ,
Lukasz Jaremko 6 and Mariusz Jaremko - Published: 28 December 2021
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