Nanoscale observation of local bound charges of patterned protein arrays by scanning force microscopy

Abstract

A protein patterned surface using micro-contact printing methods has been investigated by scanning force microscopy. Electrostatic force microscopy (EFM) was utilized for imaging the topography and detecting the electrical properties such as the local bound charge distribution of the patterned proteins. It was found that the patterned IgG proteins are arranged down to 1 µm, and the 90° rotation of patterned anti-IgG proteins was successfully undertaken. Through the estimation of the effective areas, it was possible to determine the local bound charges of patterned proteins which have opposite electrostatic force behaviors. Moreover, we studied the binding probability between IgG and anti-IgG in a 1 µm(2) MIMIC system by topographic and electrostatic signals for applicable label-free detections. We showed that the patterned proteins can be used for immunoassay of proteins on the functional substrate, and that they can also be used for bioelectronics device application, indicating distinct advantages with regard to accuracy and a label-free detection.

Rational Design of Multilayer Collagen Nanosheets with Compositional and Structural Control

“…Different charge states on a substrate can be distinguished on the basis of the potential difference with respect to the bias on the tip. This method has been employed in lifted mode to map surface charge within protein and peptide assemblies based on variation of the phase and amplitude response of an AC signal to the surface from the conductive tip. Using a positive scanning tip bias, oppositely charged substrates appear as dark images on a lighter background in EFM amplitude mode and as light images on a darker background in EFM phase mode.…”