Hydrogels are hydrophilic, porous, swollen polymers with properties (mechanical) that depend upon environmental and fabrication conditions. Devices with topographical nanostructures, such as arrays of nanopillars less then 1000 nm tall, have historically been difficult to fabricate on hydrogels. The relationship between shape and stability remains elusive and a point of research interest.<br/> <br/>In this study, a biocompatible chitosan hydrogel was fabricated with nanopillar arrays having periodicities of 300 - 500 nm. Chitosan is a derivative of chitin, the second most abundant polysaccharide in nature. We studied the effect of crosslinking and nanopattern surface area to maintain geometric stability and mechanical integrity on chitosan films. We avoid using common harsh cytotoxic crosslinkers -- instead utilizing crosslinkers such as tripolyphosphate (TPP) and genipin. TPP is a physical, ionic crosslinker; while genipin is a chemical crosslinker derived from gardenia flower. <br/> <br/>While dry, the nanopillars have a defined shape and are mechanically robust, but when wet become swollen, altering the characteristics of the films. We found the water content was strongly dependent on both the crosslinker and nanopillar geometry. Simply measuring the equilibrium swelling and changing nanopillar periodicity from 300 nm to 500 nm shows a 25% increase in water content. In this presentation, we report on results to determine whether this change is due to crosslink density, surface area, or crosslink type using mechanical testing,  AFM, UV-Vis, and DSC.

Investigating physico-chemical properties of dynamically crosslinked nanopatterned hydrogels

2019 Fall National Meeting

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