Electrostatic Read Out for Label-Free Assays Based on Kelvin Force Principle

Abstract

Detection methods and analytical devices have drawn increasing attention in recent years due to their direct impact on early detection, monitoring and diagnosis of disease in medical research. In this work, we describe a simple but so far unrecognized label-free method for surface-bound analyte detection, which could be applicable to a wide range of substances. In this respect, the feasibility and practical aspects of a micrometer-scale, poly-l-lysine-based, solid-phase assay for label-free analyte detection with electrostatic read-out are investigated. Micropatterned poly-l-lysine layers were produced using soft-lithography on mica and their electrostatic surface potential was determined using Kelvin-probe Force Microscopy. Ribose, a natural sugar, was used as analyte. Upon exposure to ribose, the surface potential changed from positive to negative in a reversible manner. We report for the first time the use of an electrostatic principle for assay read-out. This purely physical effect could be used to develop label-and marker-free assays for sugars, various other substances or, possibly, biosensors.

Growth, morphology and molecular orientation of controlled Indigo thin films on silica surfaces

“…The quality of AFM images was initially hampered by unstable tip-sample interaction along the scanning path, possibly due to residual electrostatic charges or inhomogeneous surface adhesion. As reported elsewhere, 41 stable and reproducible AFM images were obtained by immersing the films in deionized water for 30 min.…”