Design of cationic cellulose nanocrystals for potential biomedical applications

R. Sunasee, U.D. Hemraz, J. Burdick, Y. Boluk, K. Ckless
State University of New York at Plattsburgh,
United States

Keywords: cellulose nanocrystals, surface modification, characterization, cytotoxicity, biomedical application

Summary:

Cellulose nanocrystals (CNCs) have emerged as a new class of renewable biomaterial for various applications due to their remarkable properties and commercialization prospect. The relative low density, expected low cost, non-toxic character, nanoscale dimensions, high aspect ratios, large surface area, thermal properties and high modulus of elasticity make CNCs attractive nanomaterials that recently prompted the industrial production of CNCs in North America. In addition, the presence of numerous hydroxyl groups on the surface of CNCs allows covalent surface grafting for the design of novel cellulosic nanomaterials. While previous works have focused mainly on the use of CNCs as reinforcing agents in nanocomposites, there has been an emerging interest in using modified CNCs for biomedical applications due to their nanoscale dimensions, biodegradability, large surface area and biocompatibility. Herein, we report the synthesis, characterization and cytotoxicity studies of novel cationic surface modified CNC derivatives. The negative surface of CNC was rendered positive after grafting with cationic polymers such as poly(2-aminoethylmethacrylate) and poly(N-(2-aminoethylmethacrylamide)) via surface-initiated living radical polymerization method (Figure below). The resulting modified CNCs were characterized for their chemical and morphological features using a combination of analytical (Elemental analysis, TGA), spectroscopic (FT-IR, XPS) and microscopic (SEM) techniques. Cationic nature of the modified CNCs was further confirmed by gold deposition on the surface of CNCs as evidenced by SEM. Their cytotoxicity effects were evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay in two cell lines such as mouse macrophages (J774.A1) and human breast cancer (MCF7). This colorimetric assay is based on the conversion of MTT into formazan crystals (blue) by living cells, indicating mitochondrial activity, which is related to the number of viable cells. We found that only one of the modified CNCs caused significant decreased in J774.A1 cell viability (50%), at the highest concentration tested (100 µg/mL). However this concentration is well above of what would be applicable for biomedical purposes. MCF7 cells were not affected by any of the modified CNCs at any concentration. Overall, our results indicated that the modified cationic CNCs are non-toxic at physiological concentrations and thus offer great promises as novel platforms for use in a variety of bio-inspired applications.