Functionalization of nanopipettes for the detection of biomolecules

Ana Ramirez, Robert Lazenby

Florida State University

The detection of biomolecules is essential for the comprehension of molecular processes in living organisms and to provide medical diagnoses in clinical settings. The functionalization of nanopipettes offers an alternative solution to detect small biomolecules at low concentrations, while improving the temporal resolution and, potentially the spatial resolution if paired with an imaging technique. Nanopipette tips can be functionalized with aptamers (or antibodies), in which sequences are selected that bind to specific target molecules. The emerging interest in this field had led to studies where successful aptamer functionalized nanopipettes have detected biomolecules such as thrombin and serotonin. In this study, we used a multistep chemical modification process to attach aptamers to nanopipettes that can detect various analytes, including adenosine triphosphate, dopamine, and serotonin in phosphate buffered saline solution. Aptamer-target analyte recognition results in a signal change that is either due to ion current rectification (ICR) effects or blocking of the nanopipette tip. We measured the ion current induced by an applied voltage between two electrodes in solution; one inside the nanopipette and the other in the external bathing solution. A rectification coefficient was used to monitor the fabrication process of the sensing nanopipettes, obtained by recording cyclic voltammograms after each modification step. By pairing a successfully fabricated, functionalized nanopipette with scanning ion conductance microscopy (SICM), we aim to detect target biomolecules on a localized surface with high spatial resolution.