Supramolecular Composite Materials from Cellulose, Chitosan, and Cyclodextrin: Facile Preparation and Their Selective Inclusion Complex Formation with Endocrine Disruptors

We have successfully developed a simple one-step method of preparing high-performance supramolecular polysaccharide composites from cellulose (CEL), chitosan (CS), and (2,3,6-tri-O-acetyl)-α-, β-, and γ-cyclodextrin (α-, β-, and γ-TCD). In this method, [BMIm+Cl–], an ionic liquid (IL), was used as a solvent to dissolve and prepare the composites. Because a majority (\u3e88%) of the IL used was recovered for reuse, the method is recyclable. XRD, FT-IR, NIR, and SEM were used to monitor the dissolution process and to confirm that the polysaccharides were regenerated without any chemical modifications. It was found that unique properties of each component including superior mechanical properties (from CEL), excellent adsorption for pollutants and toxins (from CS), and size/structure selectivity through inclusion complex formation (from TCDs) remain intact in the composites. Specifically, the results from kinetics and adsorption isotherms show that whereas CS-based composites can effectively adsorb the endocrine disruptors (polychlrophenols, bisphenol A), their adsorption is independent of the size and structure of the analytes. Conversely, the adsorption by γ-TCD-based composites exhibits a strong dependence on the size and structure of the analytes. For example, whereas all three TCD-based composites (i.e., α-, β-, and γ-TCD) can effectively adsorb 2-, 3-, and 4-chlorophenol, only the γ-TCD-based composite can adsorb analytes with bulky groups including 3,4-dichloro- and 2,4,5-trichlorophenol. Furthermore, the equilibrium sorption capacities for the analytes with bulky groups by the γ-TCD-based composite are much higher than those by CS-based composites. Together, these results indicate that the γ-TCD-based composite with its relatively larger cavity size can readily form inclusion complexes with analytes with bulky groups, and through inclusion complex formation, it can strongly adsorb many more analytes and has a size/structure selectivity compared to that of CS-based composites that can adsorb the analyte only by surface adsorption

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, 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

Recyclable Synthesis, Characterization, and Antimicrobial Activity of Chitosan-based Polysaccharide Composite Materials

We have successfully developed a simple and totally recyclable method to synthesize novel, biocompatible, and biodegradable composite materials from cellulose (CEL) and chitosan (CS). In this method, [BMIm+Cl−], an ionic liquid (IL), was used as a green solvent to dissolve and synthesize the [CEL+CS] composites. Since, the IL can be removed from the composites by washing them with water, and recovered by distilling the washed solution, the method is totally recyclable. Spectroscopic and imaging techniques including XRD, FTIR, NIR, and SEM were used to monitor the dissolution, to characterize and to confirm that CEL and CS were successfully regenerated. More importantly, we have successfully demonstrated that [CEL+CS] composite is particularly suited for many applications including antimicrobial property. This is because the composites have combined advantages of their components, namely superior chemical and mechanical stability (from CEL) and bactericide (from CS). Results of tensile strength measurements clearly indicate that adding CEL into CS substantially increase its tensile strength. Up to 5× increase in tensile strength can be achieved by adding 80% of CEL into CS. Results of in vitro antibacterial assays confirm that CS retains its antibacterial property in the composite. More importantly, the composites reported here can inhibit growth of wider range of bacteria than other CS-based materials prepared by conventional methods; that is over 24 h period, the composites substantially inhibited growth of bacteria such as MRSA, VRE, S. aureus, E. coli. These are bacteria that are often found to have the highest morbidity and mortality associated with wound infections. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013

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

Polysaccharide Ecocomposite Materials: Materials: Synthesis, Characterization and Application for Removal of Pollutants and Bacteria

A novel, simple and totally recyclable method has been developed for the synthesis of nontoxic, biocompatible and biodegradable composite materials from cellulose and chitosan. In this method, [BMIm+Cl-], an ionic liquid (IL), was used as a solvent to dissolve and synthesize the [CEL+CS] composite materials. Since the IL can be removed from the materials by washing them with water, and recovered from the washed solution, the method is totally recyclable. XRD, FTIR, NIR and SEM were used to characterize the materials and to confirm that CEL and CS were successfully regenerated by the method without any chemical transformation. More importantly, we have successfully demonstrated that [CEL+CS] material can serve as an effective adsorbent for removal of various endocrine disruptors including polychlorophenols and bisphenol A. This is because the composites have combined advantages of their components, namely superior chemical stability and mechanical stability (from CEL) and excellent adsorption capability for pollutants (from CS)

Chiral Ionic Liquids: Synthesis, Properties, and Enantiomeric Recognition

We have synthesized a series of structurally novel chiral ionic liquids which have a either chiral cation, chiral anion, or both. Cations are an imidazolium group, while anions are based on a borate ion with spiral structure and chiral substituents. Both (or all) stereoisomeric forms of each compound in the series can be readily synthesized in optically pure form by a simple one-step process from commercially available reagents. In addition to the ease of preparation, most of the chiral ILs in this series are liquid at room temperature with a solid to liquid transformation temperature as low as −70 °C and have relatively high thermal stability (up to at least 300 °C). Circular dichroism and X-ray crystallographic results confirm that the reaction to form the chiral spiral borate anion is stereospecific, namely, only one of two possible spiral stereoisomers was formed. Results of NMR studies including 1H{15N} heteronuclear single quantum coherence (HSQC) show that these chiral ILs exhibit intramolecular as well as intermolecular enantiomeric recognition. Intramolecularly, the chiral anion of an IL was found to exhibit chiral recognition toward the cation. Specifically, for a chiral IL composing with a chiral anion and a racemic cation, enantiomeric recognition of the chiral anion toward both enantiomers of the cation lead to pronounced differences in the NMR bands of the cation enantiomers. The chiral recognition was found to be dependent on solvent dielectric constant, concentration, and structure of the ILs. Stronger enantiomeric recognition was found in solvent with relatively lower dielectric constants (CDCl3 compared to CD3CN) and at higher concentration of ILs. Also, stronger chiral recognition was found for anions with a relatively larger substituent group (e.g., chiral anion with a phenylmethyl group exhibits stronger chiral recognition compared to that with a phenyl group, and an anion with an isobutyl group has the weakest chiral recognition). Chiral anions were also found to exhibit intermolecular chiral recognition. Enantiomeric discrimination was found for a chiral IL composed of a chiral anion and achiral cation toward another chiral molecule such as a quinine derivative

One-Pot Synthesis of Biocompatible Silver Nanoparticle Composites from Cellulose and Keratin: Characterization and Antimicrobial Activity

A novel, simple method was developed to synthesize biocompatible composites containing 50% cellulose (CEL) and 50% keratin (KER) and silver in the form of either ionic (Ag+) or Ag0 nanoparticles (Ag+NPs or Ag0NPs). In this method, butylmethylimmidazolium chloride ([BMIm+Cl–]), a simple ionic liquid, was used as the sole solvent and silver chloride was added to the [BMIm+Cl–] solution of [CEL+KER] during the dissolution process. The silver in the composites can be maintained as ionic silver (Ag+) or completely converted to metallic silver (Ag0) by reducing it with NaBH4. The results of spectroscopy [Fourier transform infrared and X-ray diffraction (XRD)] and imaging [scanning electron microscopy (SEM)] measurements confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. Powder XRD and SEM results show that the silver in the [CEL+KER+Ag+] and [CEL+KER+Ag0] composites is homogeneously distributed throughout the composites in either Ag+ (in the form of AgClNPs) or Ag0NPs form with sizes of 27 ± 2 or 9 ± 1 nm, respectively. Both composites were found to exhibit excellent antibacterial activity against many bacteria including Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, methicillin-resistant S. aureus (MRSA), and vancomycin-resistant Enterococus faecalis (VRE). The antibacterial activity of both composites increases with the Ag+ or Ag0 content in the composites. More importantly, for the same bacteria and the same silver content, the [CEL+KER+AgClNPs] composite is relatively more toxic than [CEL+KER+Ag0NPs] composite. Experimental results confirm that there was hardly any Ag0NPs release from the [CEL+KER+Ag0NPs] composite, and hence its antimicrobial activity and biocompatibility is due not to any released Ag0NPs but rather entirely to the Ag0NPs embedded in the composite. Both AgClNPs and Ag0NPs were found to be toxic to human fibroblasts at higher concentration (\u3e0.72 mmol), and for the same silver content, the [CEL+KER+AgClNPs] composite is relatively more toxic than the [CEL+KER+Ag0NPs] composite. As expected, by lowering the Ag0NPs concentration to 0.48 mmol or less, the [CEL+KER+Ag0NPs] composite can be made biocompatible while still retaining its antimicrobial activity against bacteria such as E. coli, S. aureus, P. aeruginosa, MRSA, and VRE. These results, together with our previous finding that [CEL+KER] composites can be used for the controlled delivery of drugs such as ciprofloxacin, clearly indicate that the [CEL+KER+Ag0NPs] composite possesses all of the required properties for it to be successfully used as a high-performance dressing to treat chronic ulcerous infected wounds

Synthesis, Structure and Antimicrobial Property of Green Composites from Cellulose, Wool, Hair and Chicken Feather

Novel composites between cellulose (CEL) and keratin (KER) from three different sources (wool, hair and chicken feather) were successfully synthesized in a simple one-step process in which butylmethylimidazolium chloride (BMIm+Cl−), an ionic liquid, was used as the sole solvent. The method is green and recyclable because [BMIm+Cl−] used was recovered for reuse. Spectroscopy (FTIR, XRD) and imaging (SEM) results confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. KER retains some of its secondary structure in the composites. Interestingly, the minor differences in the structure of KER in wool, hair and feather produced pronounced differences in the conformation of their corresponding composites with wool has the highest α-helix content and feather has the lowest content. These results correlate well with mechanical and antimicrobial properties of the composites. Specifically, adding CEL into KER substantially improves mechanical strength of [CEL + KER] composites made from all three different sources, wool, hair and chicken feathers i.e., [CEL + wool], [CEL + hair] and [CEL + feather]. Since mechanical strength is due to CEL, and CEL has only random structure, [CEL + feather] has, expectedly, the strongest mechanical property because feather has the lowest content of α-helix. Conversely, [CEL + wool] composite has the weakest mechanical strength because wool has the highest α-helix content. All three composites exhibit antibacterial activity against methicillin resistant Staphylococcus aureus (MRSA). The antibacterial property is due not to CEL but to the protein and strongly depends on the type of the keratin, namely, the bactericidal effect is strongest for feather and weakest for wool. These results together with our previous finding that [CEL + KER] composites can control release of drug such as ciprofloxacin clearly indicate that these composites can potentially be used as wound dressing

Biocompatible Copper Oxide Nanoparticle Composites from Cellulose and Chitosan: Facile Synthesis, Unique Structure, and Antimicrobial Activity

Copper in various forms has been known to have bactericidal activity. Challenges to its application include preventing mobilization of the copper, to both extend activity and avoid toxicity, and bioincompatibility of many candidate substrates for copper immobilization. Using a simple ionic liquid, butylmethylimmidazolium chloride as the solvent, we developed a facile and green method to synthesize biocompatible composites containing copper oxide nanoparticles (CuONPs) from cellulose (CEL) and chitosan (CS) or CEL and keratin (KER). Spectroscopy and imaging results indicate that CEL, CS, and KER remained chemically intact and were homogeneously distributed in the composites with CuONPs with size of 22 ± 1 nm. Electron paramagnetic resonance (EPR) suggests that some 25% of the EPR-detectable Cu(II) is present as a monomeric species, chemically anchored to the substrate by two or more nitrogen atoms, and, further, adopts a unique spatially oriented conformation when incorporated into the [CEL + CS] composite but not in the [CEL + KER] composite. The remaining 75% of EPR-detectable Cu(II) exhibited extensive spin–spin interactions, consistent with Cu(II) aggregates and Cu(II) on the surface of CuONPs. At higher levels of added copper (\u3e59 nmol/mg), the additional copper was EPR-silent, suggesting an additional phase in larger CuONPs, in which S \u3e 0 spin states are either thermally inaccessible or very fast-relaxing. These data suggest that Cu(II) initially binds substrate via nitrogen atoms, from which CuONPs develop through aggregation of copper. The composites exhibited excellent antimicrobial activity against a wide range of bacteria and fungi, including methicillin-resistant Staphylococcus aureus; vancomycin-resistant Enterococcus; and highly resistant Escherichia coli, Streptococcus agalactiae, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Candida albicans. Expectedly, the antibacterial activity was found to be correlated with the CuONPs content in the composites. More importantly, at CuONP concentration of 35 nmol/mg or lower, bactericidal activity of the composite was complemented by its biocompatibility with human fibroblasts