Facile Use of Cationic Hydrogel Particles for Surface Modification of Planar Substrates Toward Multifunctional Neural Permissive Surfaces: An in Vitro Investigation.

Synthetic materials such as silicon have been commonly used for neural interfacing applications but are intrinsically noninteractive with neurons. Here, a facile approach has been developed to integrate both chemical and topographical cues to impart neural permissiveness for such materials. The approach simply exploits the basic phenomenon of electrostatically driven adsorption of colloidal particles onto a solid material and applies it to a cationic hydrogel particle system that we have developed recently based on "click" reaction of epoxide and amine. The particle adsorption process can be tuned by varying the adsorption time and the concentration of the original colloidal suspension, both of which directly control the surface densities of the adsorbed hydrogel particles. Using the PC12 cell line and primary cortical neurons derived from chick embryo, we demonstrate that the particle-adsorbed surface readily supports robust cell adhesion and differentiation. Although the extent of neural permissiveness exhibited by such particle-adsorbed surface was comparable to the cationic polyethylenimine-coated control surface, the adsorbed hydrogel particles offer a unique reservoir function to the modified surface that is unparalleled by the control. The successful loading of hydrophobic dye of nile red to the surface adsorbed hydrogel particles indicates that the modified surface not only provides physical support of neurons, but also can be explored in the future to exert localized therapeutic actions favorable for neural interfacing.