Tuning neuron adhesion and neurite guiding using functionalized AuNPs and backfill chemistry
The adhesion of neurons depends on the interplay between attractive as well as repellant cues in the cell membrane and adhesion ligands in their cellular environment. In this study, an easy and versatile strategy is presented to control the density of cell binding sites embedded in a cell repulsive environment attached to a solid surface. Gold nanoparticles modified by positively charged aminoalkyl thiols are used as artificial neuron adhesion ligands. The density of the nanoparticles and their environment is varied by applying either no backfill, poly(ethylene glycol)-silane, or octyltrichlorosilane backfill. By this means the chemical composition of both cell attractive adhesion ligands and surrounding repellant cues is tuned on the nanometer scale. Primary rat cortical neurons are cultured on these particle modified surfaces. The viability and neuritogenesis of neurons is investigated as a function of particle density and background composition. A strong dependence of neuron viability on both averaged particle density and backfill composition is found in particular for intermediate particle packing. At high particle densities, the kind of backfill does not affect the cell viability but influences the development of neurites. This knowledge is used to enhance the guiding efficiency of neuron adhesion to more than 90% on nanopatterned surfaces.