Label-free surface-enhanced Raman spectroscopy detection of absorption manner of lysozyme based on nanodots arrays

Lysozyme plays an important role in the innate immune system of animal or human body, thus, it is vital to detect it using a high sensitivity and efficiency approach in clinic. Nanostructure-based Surface-enhanced Raman scattering (SERS) substrate is often employed to detect biomolecules. In this study, a nanodots array structure, which was utilized as a micro-nano hybrid SERS substrate, was fabricated using second-scan scratching strategy with AFM-probe. The dependence of the nanodots structure on the machining parameters such as applied normal loads and scratching angles were investigated. The effects of the nanostructure feature sizes and the Au film thickness on the measured SERS spectra that tested using Rhodamine 6G (R6G) were studied. In addition, different drying temperatures and concentrations of NaNO 3 solution were used to study the absorption manner of lysozyme on an Ag substrate. The SERS spectra of a binary protein mixture, which includes lysozyme and insulin, were also investigated based on the fabricated nanostructures. Results showed that the substrates fabricated using AFM nanomachining approach may promote the SERS application in biologic field.