Cellulose Nanofiber Alignment Using Evaporation-Induced Droplet-Casting, and Cell Alignment on Aligned Nanocellulose Surfaces.

This work investigates droplet-evaporated cellulose nanofiber (CNF) alignment and cell responses on CNF surfaces. Surfaces of unmodified (u-), anionic (a-), and cationic (c-) CNFs were fabricated using an evaporation-induced droplet-casting method and characterized in terms of degree of orientation. Circular variance (CV) values obtained using Cytospectre software to analyze the degree of orientation from AFM images showed a significantly higher degree of orientation on c- and u-CNF surfaces (average CV 0.27 and 0.24, respectively) compared to a-CNF surfaces (average CV 0.76). Quantitative analysis of surface roughness plots obtained from AFM images confirmed the difference between the direction of alignment versus the direction perpendicular to alignment. AFM images as well as observations during droplet evaporation indicated c-CNF alignment parallel to a dry-boundary line during droplet evaporation. Fibroblasts were cultured on the u-, a-, and c-CNF surfaces with or without a fibronectin (FN) coating for 48 h, and the cell response was evaluated in terms of cell viability, proliferation, morphology, and degree of orientation. Cell viability and proliferation were comparable to that on a control surface on the a-CNF and c-CNF surfaces. Although an FN coating slightly enhanced cell growth on the studied surfaces, uncoated a-CNF and c-CNF surfaces were able to support cell growth as well. The results showed cell orientation on aligned c-CNF surfaces, a finding that could be further utilized when guiding the growth of cells. We also showed that the alignment direction of c-CNFs and thus the cell orientation direction can be controlled with a contact-dispensing technique.