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

Abstract

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.

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

“…[30][31][32]35 As shown in Scheme 1, washed wool was dissolved in BMIm + Cl -at 120 °C. Once dissolved, the solution temperature was reduced to 90 °C before CEL was added to the KER solution.…”

“…As expected, the blue spectrum of [CEL+KER] is similar to those previously observed for the [CEL+KER] composites, namely, bands at 1700-1600 and 1550 cm -1 are due to C═O stretch (amide I) and C-N stretch (amide II) vibrations and those at 1300-1200 cm -1 are from the in-phase combination of the N-H bend and C-N stretch vibrations (amide III). [30][31][32][36][37][38] Major bands between 1200 and 900 cm -1 are due to sugar ring deformations of the CEL. [30][31][32][36][37][38] The fact that the green spectrum of the [CEL+KER+Ag 0 NPs] composite is relatively similar to the blue spectrum of the [CEL+KER] composite seems to indicate that there may not be strong interaction between the Ag 0 NPs and CEL and KER in the composite.…”

“…[30][31][32][36][37][38] Major bands between 1200 and 900 cm -1 are due to sugar ring deformations of the CEL. [30][31][32][36][37][38] The fact that the green spectrum of the [CEL+KER+Ag 0 NPs] composite is relatively similar to the blue spectrum of the [CEL+KER] composite seems to indicate that there may not be strong interaction between the Ag 0 NPs and CEL and KER in the composite. However, careful inspection of the spectra revealed that there are indeed minor differences in the amide bands at around 1700-1600 and 1550 cm -1 between the two spectra.…”

“…[29][30][31][32][33][34][35] Spectroscopy [Fourier transform infrared (FTIR), near-infrared (NIR), and cross-polarization magic angle spinning (CP-MAS) 13 C NMR] results indicate that there was no chemical alteration in the structures of CEL and KER. [29][30][31][32][33][34][35] While there may be some changes in the molecular weights of CEL and KER, by accessed by following the link in the citation at the bottom of the page. Vol 8, No.…”

“…31,35 The [CEL+KER] composites obtained were found to retain unique properties of their components, namely, superior mechanical strength from CEL and controlled release of drugs by KER. [29][30][31][32][33][34][35] The information presented clearly indicates that it is possible to use NPs from changing size and morphology as well as undergoing coagulation, they can, therefore, fully retain the unique property of the AgNPs for repeated use without any complication of the reducing activity and not fully recover after each use. With these two composites, we will be able to finally address the important question that, to date, still remains unanswered, namely, the antimicrobial activity of AgNPs due to either Ag + or Ag 0 or both, and if both forms are active, which NPs have higher activity.…”