(J-373) Single-Cell Fluidic Force Spectroscopy Reveals Nano-topography Controls Neural Adhesion Force to Flexible Implant Substrates

Introduction:: The efficacy and life of the neural prosthesis rely heavily on neuron-artificial substrate interactions. The interaction between cells and nanostructured substrates has shown great promise in advancing high-fidelity electrogenic cell interfaces. This is, in large part, due to the unique topography on a scale comparable to that of proteins and lipids.


Materials and Methods:: In this work, we investigated the impact of nanotopography of flexible neural implant substrate on neuron-substrate interactions. To that end, we developed a precise oxygen plasma etching process that allows control over a range of nanotopography of polyimide (PI) surfaces -a common polymer used for neural interface applications. This enabled us to investigate the initial adhesion behavior of SH-SY5Y human neuroblastoma cells and human astrocytes (NHA) on nano-roughened PI (rPI). In addition, using high-sensitivity FluidFM-based single-cell force spectroscopy (SCFS), we mapped the prominent adhesion profiles of SH-SY5Y cells to rPI with different levels of nanoroughness.


Results, Conclusions, and Discussions:: Oxygen dry etching induced a diverse range of nano-topographical features on PI surfaces, achieving roughness levels of up to 25 nm, while avoiding any chemical modifications of the surface. Initial adhesion of SH-SY5Y neuroblastoma cells and NHA showed an increase of SH-SY5Y cells adhesion on nano-roughened rPI surfaces compared to smooth ones with a reduction in NHA adhesion, especially at 15 nm roughness. SCFS revealed that SH-SY5Y cells exhibit a 2.5-fold increase in prominent adhesion forces (150-164 nN) when grown on rPI compared to smooth surfaces (60-107 nN). More importantly, the cells showed stiffening without cell area flattening on top of nano-roughened PI surfaces due to an increase in the real effective surface area; this will potentially reduce the gap between the neurons and artificial substrates leading to lower power requirements for stimulation and higher fidelity recordings. Overall, our results provide novel biomechanical insights into the impact of nano-topography on neuron/glia adhesion to flexible polymer surfaces which can possibly guide neural implant surface design.


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