Classification of the Binding Events between Streptavidin and Biotin-Decorated Activated Vapour Silanized (Avs) Atomic Force Microscopy Tips

Abstract

AFM tips were functionalized using the activated vapour silanization (AVS) process and its application in affinity atomic force microscopy was assessed by characterizing the interaction between biotin and streptavidin as model system. AVS-functionalized tips can be easily decorated with sensor molecules following well-established cross-linking chemistries as shown by covalently binding biotin molecules to the amine groups of the AFM tip. Force-distance (F-d) curves were recorded to measure the interaction between the biotin-decorated tips and a substrate covered with covalently bound streptavidin. F-d curves were initially recorded with a pristine streptavidin coating and, subsequently, new F-d curves were obtained after blocking the streptavidin binding sites with biotin-albumin. The F-d curves were classified from the intensity of the adhesion force and the number of interaction events (peaks) observed in each curve. It is shown that single molecular biotin-streptavidin interaction events are recorded consistently and no degradation evidence was observed in any of the functionalized tips during the whole two-step experiment.

Keywords: Affinity atomic force microscopy, AFM, streptavidin, biotin, functionalization