Publication Title: In Situ Monitoring of Aptamer–Protein Binding on a ZnO Surface Using Spectroscopic Ellipsometry
Real-world applications of Moorfield products in science
In-situ monitoring of Aptamer-Protein binding
Paper Abstract
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.
How Moorfield products helped:
Nominally 80 nm ZnO films were deposited onto silicon substrates using our nanoPVD-S10A benchtop thin film deposition system by RF magnetron sputtering. The deposition process started with cleaning the Si substrates (SSP, 1–10 ohm-cm), cut into pieces with 2 × 4 cm2 dimensions. The Si substrates were cleaned with acetone, IPA, and ethanol for 5 min each then rinsed with DI water and dried with nitrogen gas. The substrates were placed in a sputter chamber with a ZnO target of 99.99% purity, and the chamber was evacuated until an initial pressure of 4.3 × 10−7 mBar. The conditions for the plasma during deposition were an Ar gas flow: 3.5 sccm, RF power of 52 watt, resulting in a growth rate of 0.025 nm/s at ambient temperature.
Open Access publication details:
Alshammari, A., van Zalinge, H. and Sandall, I. (2023) ‘In Situ Monitoring of Aptamer–Protein Binding on a ZnO Surface Using Spectroscopic Ellipsometry’, Sensors, 23(14), p. 6353. Available at: https://doi.org/10.3390/s23146353.