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

Abstract

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 3dimensional 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.

Synthesis and Catalytic Studies of Thermoresponsive Copper (I) Complex towards Click Reactions

“…Though the deconvolution of C1s and O1s signals fails to provide concrete proof of the success of the click reaction, N1s deconvolution spectra can prove the functionalization (Supporting Information, Figure S22C and D). Thus, after the click reaction, the peak intensity at 399.6 eV increased drastically due to the combined contribution of nitrogens from the collagen (R‐ N H 2 ) and the nitrogen from the triazole ring [65] . However, the controlled material did not observe such an increment in the peak intensity (at 399.7 eV).…”

“…Thus, after the click reaction, the peak intensity at 399.6 eV increased drastically due to the combined contribution of nitrogens from the collagen (R-NH 2 ) and the nitrogen from the triazole ring. [65] However, the controlled material did not observe such an increment in the peak intensity (at 399.7 eV). Thus, N1s deconvoluted spectrum can support the chemical functionalization of the collagen through click reaction in the presence of the catalyst.…”

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

“…Various instances of using alkoxysilanes for functionalizing different surfaces like silica nanoparticles have been reported in the literature. − Although, in many cases, a single alkoxysilane molecule with desired functionality at the other end is used for the functionalization of silica nanoparticles, it is often challenging to synthesize a molecule with an anchoring group at one end and a specific functionality at the other end. An alternative approach relies on postfunctionalization, where a facile reaction can be performed on the end functional group of preformed SAM on nanoparticles to incorporate the critical functional group. , For example, esterification reactions, coupling reactions, etc have been applied to perform diverse reactions on SAM of various nanoparticles and other surfaces. Some of those reactions lack good efficacy for quantitative functionalization .…”

“…An alternative approach relies on postfunctionalization, where a facile reaction can be performed on the end functional group of preformed SAM on nanoparticles to incorporate the critical functional group. 36,37 For example, esterification reactions, coupling reactions, 38 etc have been applied to perform diverse reactions on SAM of various nanoparticles and other surfaces. Some of those reactions lack good efficacy for quantitative functionalization.…”