Electrodeposition of a biopolymeric hydrogel in track-etched micropores

Electrodeposition within the pores of track etched polycarbonate membranes (TEPCMs) has been used to convert ions and small molecules into 1D micro- and nanoparticles with controlled sizes, compositions and functional properties. Here, we report that the stimuli-responsive aminopolysaccharide chitosan can be triggered to self-assemble into a hydrogel network within the micropores (3-8 mm) of TEPCMs. The putative mechanism for chitosan electrodeposition involves the field-guided migration of cationic chitosan chains into the pores followed by a sol-gel transition induced by chitosan's localized neutralization within the pore due to the high pH generated by cathodic electrolysis reactions. Chitosan migration and gelation within the pores was demonstrated by dissolving the TECPM template after electrodeposition and analyzing the released microgel particles. These findings are fundamentally interesting because they demonstrate that polymer solutions above their overlap concentrations (i.e., semi-dilute solutions) can be transported into and triggered to assemble within confined micropores. In addition, the extension of template-electrodeposition to biocompatible hydrogels should enable the fabrication of biofunctionalized membranes and microparticles for a broad range of applications in food, biotechnology and medicine.