Fig. 5: Wrapping of neuronal processes in vitro.

A Exemplary optical images of cultured rat hippocampal neurons and 6 µm by 6 µm pDR1M platforms before and after rolling with the depicted light stimulus (no polarization, 8 mW mm⁻², 6 s). B Exemplary colored optical images at higher magnification of the neurons (blue) and 6 µm by 6 µm pDR1M platforms (red) before and after rolling with the depicted light stimulus (no polarization, 8 mW mm⁻², 6 s). C Colored SEM images of neurons (blue) with the pDR1M wrapped structures (red). The images on the right show how the layer can conform to various curvatures and even delicately wrap sub-0.5 µm processes, as revealed in the magnified inset. D Biocompatibility tests of 16-day-old hippocampal rat neurons cultured with the pDR1M platforms. (i) MTT assays—Control: cells without platforms, 4(2): cells incubated with the platforms for 4 days (2 days post-illumination), 6(4): cells incubated with the platforms for 6 days (4 days post-illumination), 9(7): cells incubated with the platforms for 9 days (7 days post-illumination), 9-flat: cells incubated with the platforms for 9 days and without illumination, 9(7)-2x: cells incubated with double the concentration of the platforms (1889 ± 222 per mm² instead of 953 ± 109 per mm²) for 9 days (7 days post-illumination). All absorbance values display the mean ± standard deviation of at least three replicas for each condition. The background values are obtained from the cell media supplemented with the platforms, while the difference (=cells – background) represents the amount of absorbance due to the metabolic activity of the cells. (ii) Viability imaging overview of a 37-day-old rat hippocampal neurons cultured for 27 days (26 days after illumination) with the pDR1M platforms. Top: a dense region, bottom: sparse neurons. Green: live cells stained with a cell viability indicator (FITC filter set), red: cell membrane stain (TRITC filter set). E) Colored SEM images of a neuron (blue) with several 6 µm by 6 µm pDR1M platforms (red).