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. 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

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