(275d) Functionalization of Nanostructured ZnO Surfaces with Selective Linker Molecules Towards Biomolecule Detection

In this study, the influence of surface functionalization on charge transfer in nanostructured zinc oxide (ZnO) surface was investigated. Sensing sites with tailored surfaces offer novel immobilization strategies for selective functionalization and specific interaction of protein biomolecules, which can lead to enhancement in specific output signal response and hence selectivity. Functionalization of nanostructured ZnO surfaces were evaluated using two organic molecules with thiol and phosphonic acid functional groups. Dithiobis(succinimidyl propionate) (DSP) and 11-Aminoundecylphosphonic acid (AUPA) covalently link to ZnO providing NHS binding sites for controlled immobilization of antibody. Fluorescence intensity measurements with varying concentrations of DSP and AUPA labeled with Rhodamine B were performed, to identify the amount of functionalization. We observed saturation in fluorescence intensity with increasing concentration of linker molecules. Such modified ZnO surfaces were characterized using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and electrically using electrochemical impedance spectroscopy (EIS) and Mott-Schottky (MS) analysis. XPS spectra revealed selective binding of thiol to zinc interstitials and phosphonic to oxygen vacancies on nanostructured ZnO. To demonstrate the potential of functionalized surfaces for biomolecule detection, cardiac troponin-T, a protein biomarker specific for acute myocardial infarction was chosen. The influence of selective functionalization on charge transfer and perturbations at ZnO electrode-electrolyte interfaces due to biomolecular binding was studied using EIS and MS analysis. Our results demonstrate that leveraging zinc interstitials increases the sensitivity of biomolecule detection over larger dynamic range and detection limit at 10 fg/mL.