Cellulose, Chitosan, and Keratin Composite Materials. Controlled Drug Release

A method was developed in which cellulose (CEL) and/or chitosan (CS) were added to keratin (KER) to enable [CEL/CS+KER] composites to have better mechanical strength and wider utilization. Butylmethylimmidazolium chloride ([BMIm+Cl–]), an ionic liquid, was used as the sole solvent, and because the [BMIm+Cl–] used was recovered, the method is green and recyclable. Fourier transform infrared spectroscopy results confirm that KER, CS, and CEL remain chemically intact in the composites. Tensile strength results expectedly show that adding CEL or CS into KER substantially increases the mechanical strength of the composites. We found that CEL, CS, and KER can encapsulate drugs such as ciprofloxacin (CPX) and then release the drug either as a single or as two- or three-component composites. Interestingly, release rates of CPX by CEL and CS either as a single or as [CEL+CS] composite are faster and independent of concentration of CS and CEL. Conversely, the release rate by KER is much slower, and when incorporated into CEL, CS, or CEL+CS, it substantially slows the rate as well. Furthermore, the reducing rate was found to correlate with the concentration of KER in the composites. KER, a protein, is known to have secondary structure, whereas CEL and CS exist only in random form. This makes KER structurally denser than CEL and CS; hence, KER releases the drug slower than CEL and CS. The results clearly indicate that drug release can be controlled and adjusted at any rate by judiciously selecting the concentration of KER in the composites. Furthermore, the fact that the [CEL+CS+KER] composite has combined properties of its components, namely, superior mechanical strength (CEL), hemostasis and bactericide (CS), and controlled drug release (KER), indicates that this novel composite can be used in ways which hitherto were not possible, e.g., as a high-performance bandage to treat chronic and ulcerous wounds

Facile Synthesis, Characterization, and Antimicrobial Activity of Cellulose-Chitosan-Hydroxyapatite Composite Material: A Potential Material for Bone Tissue Engineering

Hydroxyapatite (HAp) is often used as a bone-implant material because it is biocompatible and osteoconductive. However, HAp possesses poor rheological properties and it is inactive against disease-causing microbes. To improve these properties, we developed a green method to synthesize multifunctional composites containing: (1) cellulose (CEL) to impart mechanical strength; (2) chitosan (CS) to induce antibacterial activity thereby maintaining a microbe-free wound site; and (3) HAp. In this method, CS and CEL were co-dissolved in an ionic liquid (IL) and then regenerated from water. HAp was subsequently formed in situ by alternately soaking [CEL+CS] composites in aqueous solutions of CaCl2 and Na2HPO4. At least 88% of IL used was recovered for reuse by distilling the aqueous washings of [CEL+CS]. The composites were characterized using FTIR, XRD, and SEM. These composites retained the desirable properties of their constituents. For example, the tensile strength of the composites was enhanced 1.9 times by increasing CEL loading from 20% to 80%. Incorporating CS in the composites resulted in composites which inhibited the growth of both Gram positive (MRSA, S. aureus and VRE) and Gram negative (E. coli and P. aeruginosa) bacteria. These findings highlight the potential use of [CEL+CS+HAp] composites as scaffolds in bone tissue engineering

Synergistic Adsorption of Heavy Metal Ions and Organic Pollutants by Supramolecular Polysaccharide Composite Materials from Cellulose, Chitosan and Crown Ether

We have developed a simple one-step method to synthesize novel supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS) and benzo-15-crown 5 (B15C5). Butylmethylimidazolium chloride [BMIm+Cl−], an ionic liquid (IL), was used as a sole solvent for dissolution and preparation of the composites. Since majority of [BMIm+Cl−] used was recovered for reuse, the method is recyclable. The [CEL/CS + B15C5] composites obtained retain properties of their components, namely superior mechanical strength (from CEL), excellent adsorption capability for heavy metal ions and organic pollutants (from B15C5 and CS). More importantly, the [CEL/CS + B15C5] composites exhibit truly supramolecular properties. By itself CS, CEL and B15C5 can effectively adsorb Cd2+, Zn2+ and 2,4,5-trichlorophenol. However, adsorption capability of the composite was substantially and synergistically enhanced by adding B15C5 to either CEL and/or CS. That is, the adsorption capacity (qe values) for Cd2+ and Zn2+ by [CS + B15C5], [CEL + B15C5] and [CEL + CS + B15C5] composites are much higher than combined qe values of individual CS, CEL and B15C5 composites. It seems that B15C5 synergistically interact with CS (or CEL) to form more stable complexes with Cd2+ (or Zn2+), and as a consequence, the [CS + B15C5] (or the [CEL + B15C5]) composite can adsorb relatively larger amount Cd2+ (or Zn2+). Moreover, the pollutants adsorbed on the composites can be quantitatively desorbed to enable the [CS + CEL + B15C5] composites to be reused with similar adsorption efficiency

Cellulose-Chitosan-Keratin Composite Materials: Synthesis, Immunological and Antibacterial Properties

Novel composites were synthesized from keratin (KER), cellulose (CEL) and chitosan (CS). The method is recyclable because majority (\u3e88%) of [BMIm+Cl-], an ionic liquid (IL), used as the sole solvent, was recovered for reuse. Experimentally, it was confirmed that unique properties of each component remain intact in the composites, namely bactericide (from KER and CS) and anti-inflammatory property (from KER). Specifically, the composites were examined for their anti-inflammatory influence on macrophages. The cells were imaged and immunophenotyped to determine the quantity using the macrophage marker CD11b. The 75:25 [KER+CS] composite was found to have the least amount of CD11b macrophages compared to other composites. Bactericidal assays indicated that all composites, except the 25:75 [KER+CS], substantially reduce the growth of organisms such as vancomycin resistant Enterococcus (VRE) and Eschericia coli. The results clearly indicate that the composites possess all properties needed for effective use as a wound dressin

Supramolecular Biopolymeric Composite Materials: Green Synthesis, Characterization and Applications

Macrocycles, such as crown ethers (CRs) and resorcinarenes (RESs), exhibit selective complexation of heavy metal ions and organic pollutants respectively. Consequently, they have been investigated for their suitability in adsorbing these aqueous pollutants. However, they are difficult to handle and recycle for reuse because, by themselves, they can only be fabricated in powder form. To alleviate this challenge, we developed a method to encapsulate these macrocycles into film-forming polysaccharides--cellulose (CEL) and chitosan (CS). This was achieved by using a green and recyclable solvent, an ionic liquid, to dissolve both macrocycles and polysaccharides and regenerate corresponding composites in water. Resultant composites were characterized by FTIR, UV-Visible, X-ray powder diffraction and scanning electron microscopy. These polysaccharides are attractive because they are naturally abundant, biodegradable and biocompatible. The composites retained desirable properties of their individual constituents, namely superior mechanical strength (from CEL), excellent adsorption capability for cadmium and zinc ions (from CRs and CS) and organic solutes (from RESs and CS). Specifically, increasing the concentration of CEL from 50% to 90% in [CEL+CR] resulted in almost 2X increase in tensile strength. Adding 40% benzo 15-crown-5 ether (B15C5) to CS led to a 4X enhancement in the amount of cadmium ions adsorbed by [CS+B15C5]. Interestingly, RES-based composites exhibited selectivity amongst dinitrobenzene (DNB) isomers. For example, one g of [CEL+RES] adsorbed more 1,2-DNB (5.37±0.05 mol L-1) than 1,3-DNB (4.52±0.03 mol L-1) and 1,4-DNB (2.74±0.04 mol L-1). These results help to extend the potential applications of supramolecular composites in water remediation. We also successfully synthesized hydroxyapatite (HAp) in situ by alternately soaking [CEL+CS] composite films in calcium and phosphate salt solutions. These composites will be expected to be osteoconductive (due to HAp), thereby necessitating their use in bone tissue engineering. In another related study, we developed a simple, one step process to encapsulate an antibiotic, ciprofloxacin (CPX) in composites containing various proportional concentrations of CEL, CS, and keratin (KER). KER was found to slow down the release of CPX from the composites. These results clearly indicate that the release of CPX can be controlled by judicious adjustment of the concentrations of KER in the composites

Cellulose, Chitosan and Keratin Composite Materials: Facile and Recyclable Synthesis, Conformation and Properties

A method was developed in which cellulose (CEL) and/or chitosan (CS) were added to keratin (KER) to enable [CEL/CS+KER] composites formed to have better mechanical strength and wider utilization. Butylmethylimmidazolium chloride ([BMIm⁺Cl^–]), an ionic liquid, was used as the sole solvent, and because the majority of [BMIm⁺Cl^–] used (at least 88%) was recovered, the method is green and recyclable. FTIR, XRD, ¹³C CP-MAS NMR and SEM results confirm that KER, CS and CEL remain chemically intact and distributed homogeneously in the composites. We successfully demonstrate that the widely used method based on the deconvolution of the FTIR bands of amide bonds to determine secondary structure of proteins is relatively subjective as the conformation obtained is strongly dependent on the choice of parameters selected for curve fitting. A new method, based on the partial least squares regression analysis (PLSR) of the amide bands, was developed, and proven to be objective and can provide more accurate information. Results obtained with this method agree well with those by XRD, namely they indicate that although KER retains its second structure when incorporated into the [CEL+CS] composites, it has relatively lower α-helix, higher β-turn and random form compared to that of the KER in native wool. It seems that during dissolution by [BMIm⁺Cl^–], the inter- and intramolecular forces in KER were broken thereby destroying its secondary structure. During regeneration, these interactions were reestablished to reform partially the secondary structure. However, in the presence of either CEL or CS, the chains seem to prefer the extended form thereby hindering reformation of the α-helix. Consequently, the KER in these matrices may adopt structures with lower content of α-helix and higher β-sheet. As anticipated, results of tensile strength and TGA confirm that adding CEL or CS into KER substantially increase the mechanical strength and thermal stability of the [CS/CEL+KER] composites

Cellulose-Chitosan-Keratin Composite Materials: Synthesis, Immunological and Antibacterial Properties

We have developed a simple and recyclable method to synthesize novel biocompatible composites from cellulose (CEL), chitosan (CS) and keratin (KER). Butylmethylimidazolium chloride [BMIm+Cl-], an ionic liquid (IL), was used as a sole solvent for dissolution and preparation of the composites. Since majority of [BMIm+Cl-] used (&gt;88%) was recovered for reuse, the method is recyclable. Various spectroscopic and imaging techniques including powder X-ray diffraction (XRD), FT-IR, near-IR, 13C CP MAS –NMR, and scanning electron microscope were used to monitor the dissolution process, to characterize the composites and to confirm that CEL, CS and KER were successfully regenerated by the method. The [CEL-CS+KER] composites obtained retain properties of their components, namely superior mechanical strength (from CEL), excellent antimicrobial activity (from CS), superior adsorption capability for organic pollutants (from CS) and ability to controlled delivery of drug (from KER). For example, the composites can effectively adsorb various endocrine disruptors including polychlorophenols and bisphenol A, and toxin such as microcystins. The composites were found to substantially reduce growth of Escherichia coli (ATCC 8739), Staphylococcus aureus (ATCC 25923), methicillin resistant S. aureus (ATCC 33591) and vancomycin resistant Enterococcus faecalis (ATCC 51299). The composites are non-toxic to fibroblasts; i.e., fibroblasts were found to grow and proliferate in the presence of the composites. Antibiotic such as ciproprofloxacin can be encapsulated into the composite and kinetic its release can be controlled by judiciously adjusting composition of the composites.</jats:p