Characterization of Dendritic Polyglycerol Amine Layers as Coatings for Improved Neural Cell Growth Surfaces

Surfaces coated with the hyperbranched dendritic polyglycerol amine, dPGA, a nonprotein macromolecular biomimetic of polylysine, have been shown to provide enhanced support for stable long-term culture of embryonic rat neocortical neurons and human neurons derived from induced pluripotent stem cells (iPSCs). Here, we investigate the physical properties of surface-adsorbed dPGA to understand how it provides better support for cell attachment, survival, and growth. High-molecular-weight dPGA (MW 550 kDa) with ∼30% amine functionalization was deposited on silicon wafers from PBS (pH 7.4) solutions to measure the layer thickness and density by ellipsometry and surface roughness and texture by atomic force microscopy (AFM). Colloidal silica (dia ∼ 100 nm) was used as a substrate to measure surface charge (zeta potential), adsorbed amounts by thermal gravimetric analysis (TGA), and molecular mobility by solid-state NMR spectroscopy. We found that the dPGA film properties were dependent on the immersion time in the dPGA coating solution as well as the storage conditions of dPGA solutions. Upon immobilization, dPGA retains a globular but flattened shape. Chain mobility is reduced but the adsorbed dPGA still can be considered a highly flexible polymer that rearranges to present a higher density of positive surface charges as compared to dPGA in solution. Coated surfaces prepared with different deposition times were tested for the capacity to support cells in culture.