Improving Hydrophobicity of Collagen with Silica Nanoparticles: Probing a Noncovalent Approach.

Collagen-based materials have a wide range of applications in wound care, tendon repair, cartilage repair, etc. Improving certain properties such as hydrophobicity can diversify the application areas. In this work, we investigated the noncovalent interactions of suitably functionalized silica nanoparticles with collagen for the possibility of improving hydrophobicity. Functionalization on silica nanoparticles was achieved via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) or "click" reaction using surface grafting methods. Furthermore, we synthesized two different silica nanoparticles (SiNPs) functionalized with the fluorine-containing substrate or only with an aryl moiety (silica-g-4EMB and silica-g-ETFMB) for comparison. The functionalized SiNPs immobilized along with the model system trans-4-hydroxy-l-proline (HPA) (usually present in abundant quantities in collagen) have been probed using nuclear magnetic resonance (NMR) spin relaxation to appreciate the influence of SiNPs on HPA. Furthermore, we effectively utilized a saturated transfer difference (STD) NMR experiment to measure the interaction parameters between judiciously functionalized silica nanoparticles and substrates of interest. In essence, such a detailed study on noncovalent interactions employing an arsenal of experimental approaches facilitated the immobilization of suitably functionalized silica nanoparticles to collagen and leather (where collagen is a major constituent), leading to improvements in hydrophobicity.

Functionalization of Bacterial Cellulose and Related Surfaces Using a Facile Coupling Reaction by Thermoresponsive Catalyst.

Recently, bacterial cellulose and related materials attracted significant attention for applications such as leather-like materials, wound healing materials, etc., due to their abundance in pure form and excellent biocompatibility. Chemical modification of bacterial cellulose further helps to improve specific properties for practical utility and economic viability. However, in most cases, chemical modification of cellulose materials involves harsh experimental conditions such as higher temperatures or organic solvents, which may destroy the 3-dimensional network of bacterial cellulose, thereby altering its characteristic properties. Hence, in this work, we have adopted the Suzuki coupling methodology, which is relatively unexplored for chemically modifying cellulose materials. As the Suzuki coupling reaction is tolerable against air and water, modification can be done under mild conditions so that the covalently modified cellulose materials remain intact without destroying their 3-dimensional form. We performed Suzuki coupling reactions on cellulose surfaces using a recently developed thermoresponsive catalyst consisting of poly(N-isopropylacrylamide) (PNIPAM)-tagged N-heterocyclic carbene (NHC)-based palladium(II) complex. The thermoresponsive nature of the catalyst particularly helped to perform reactions in a water medium under mild conditions considering the biological nature of the substrates, where separation of the catalyst can be easily achieved by tuning temperature. The boronic acid derivatives have been chosen to alter the wettability behavior of bacterial cellulose. Bacterial cellulose (BC) obtained from fermentation on a lab scale using a cellulose-producing bacterium called Gluconacetobacter kombuchae (MTCC 6913) under Hestrin-Schramm (HS) medium, or kombucha-derived bacterial cellulose (KBC) obtained from kombucha available in the market or cotton-cellulose (CC) was chosen for the surface functionalization to find the methodology's diversity. Movie files in the Supporting Information and figures in the manuscript demonstrated the utility of the methodology for fluorescent labeling of bacterial cellulose and related materials. Finally, contact angle analysis of the surfaces showed the hydrophobic natures of some functionalized BC-based materials, which are important for the practical use of biomaterials in wet climatic conditions.

Bacterial cellulose: A promising biopolymer with interesting properties and applications.

The ever-increasing demands for materials with desirable properties led to the development of materials that impose unfavorable influences on the environment and the ecosystem. Developing a low-cost, durable, and eco-friendly functional material with biological origins has become necessary to avoid these consequences. Bacterial cellulose generated by bacteria dispenses excellent structural and functional properties and satisfies these requirements. BC and BC-derived materials are essential in developing pure and environmentally safe functional materials. This review offers a detailed understanding of the biosynthesis of BC, properties, various functionalization methods, and applicability in biomedical, water treatment, food storage, energy conversion, and energy storage applications.