Novel polymer substrates for SFM investigations of living cells, biological membranes, and proteins.

Extended studies were performed to prepare substrates for scanning force microscopy of biological samples with a surface roughness below 1 nm rms over an area of 500 x 500 nm2. The substrate smoothness and the lack of tip obscuring material are indispensable in order to visualize detailed structures of membrane surfaces, particularly when scanning the lamellipodia of mechanically sensitive goldfish glial cells where peripheral lamellipodia are only 20-30 nm in thickness. Appropriate substrates are poly(vinyl phenyl ketone) or furan polymers with corrugations of 0.3 and 0.15 nm rms, respectively, to which the growth-promoting protein laminin adsorbs directly with an acceptably increased roughness. Cells show normal growth behavior on these substrates and stick to the substrates in a stable fashion during several scans. Thus details of the membrane's surface may be resolved and are not obscured by the substrate texture. The uncoated furan polymer substrates are suitable for immobilization of membrane preparations such as purified membrane fragments containing bacteriorhodopsin or Na, K-ATPase and protein preparations such as antibodies.