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Attaching Single Biomolecules Selectively to the Apex of AFM Tips for Measuring Specific Interactions

Department of Chemistry & Center for Materials Chemistry, University of Houston, Houston, Texas 77204-5003

Correspondence: Address reprint requests and inquiries to Chengzhi Cai, Tel.: 713-743-2710; Fax: 713-743-2709; E-mail: cai{at}uh.edu.

We present a general approach for preparing well-defined AFM tips for probing single target molecules. We demonstrated that carboxylic acid groups could be generated by electrochemical oxidation selectively at the apex of an AFM tip that is coated with a monolayer of oligo(ethylene glycol) derivatives for resisting nonspecific interactions. These carboxylic acid groups were used as handles to tether only one ligand molecule, such as biotin, to the tip apex for measurement of specific interactions with biomolecules.