In Situ Monitoring of Aptamer-Protein Binding on a ZnO Surface Using Spectroscopic Ellipsometry

The dissolution of zinc oxide is investigated using spectroscopic ellipsometry to investigate its suitability as a platform for biosensing applications. The results indicate that once the ZnO surface has been functionalised, it is suitably protected, and no significant dissolving of the ZnO occurs. The binding kinetics of the SARS-CoV-2 spike protein on aptamer-functionalised zinc oxide surfaces are subsequently investigated. Values are extracted for the refractive index and associated optical constants for both the aptamer layer used and the protein itself. It is shown that upon an initial exposure to the protein, a rapid fluctuation in the surface density is observed. After around 20 min, this effect stabilises, and a fixed increase in the surface density is observed, which itself increases as the concentration of the protein is increased. This technique and setup are demonstrated to have a limit-of-detection down to 1 nanomole (nM) and display a linear response to concentrations up to 100 nM.

Automated summary

The dissolution behavior of zinc oxide is investigated using spectroscopic ellipsometry to assess its suitability as a biosensing platform. The results show that functionalized zinc oxide surfaces are well-protected and do not dissolve significantly. The binding kinetics of the SARS-CoV-2 spike protein on aptamer-functionalized zinc oxide surfaces are studied, revealing fluctuation in surface density upon initial exposure and a stable increase in density with increasing protein concentration. The technique and setup demonstrate a limit-of-detection of 1 nanomole (nM) and a linear response up to 100 nM.