Nanofiber-laden hydrogel as a dynamic 3D cell culture platform

Abstract

Hydrogels are a popular choice as a cell culture platform for various biomedical applications. However, it is still a significant challenge to control their physicochemical and mechanical properties, while closely emulating the native cellular microenvironment. Native extracellular matrix (ECM) is a highly heterogeneous mix of collagen fibrils and proteoglycans and other ECM proteins. However, most conventional hydrogels are developed by crosslinking gel-forming monomers and macromers only at a molecular level. As a result, hydrogels with controllable mechanical properties often suffer from diminished permeability, which often critically hinders sufficient cellular activities in 3D. Herein, an innovative strategy of incorporating bioactive nanofibers within hydrogel is presented in order to more closely mimic natural ECM. First, nanofibers consisting of hydrophilic and photocrosslinkable gelatin and conductive polymer are developed by electrospinning. Then these continuous nanofibers are cut into micrometer-lengths, and chemically crosslinked to render aqueous stable and dispersible. These dispersible hybrid nanofiber (dhNF) as heteroscale reinforcing elements are infused into hydrogels. The resulting 'heteroscale' dhNF-infused hydrogels, consisting of molecular and nanofibrous polymeric network, show significant improvement on both mechanical strength and electrical conductivity by dhNF concentration as well as conductive polymer content in dhNF, without significantly affecting the permeability necessary for cellular maneuverability. These properties not only directly help improve the viability and proliferation of encapsulated cells, but also more effectively relayed external electrical stimulation mediated by enhanced conductivity.