Cost-effective gold platform for SERS spectroscopy of macromolecules and biopolymers.

It is known that optical signals from biopolymers and macromolecules in Raman surface-enhanced spectroscopy (SERS) and surface enhanced infra-red absorption (SEIRA) spectroscopy is not easy to get due to many cites of interaction of the molecules with a substrate. Mechanism of SERS enhancement is usually explained by local fields near metal or graphite-type surface (electromagnetic mechanism) and increasing of polarizability of the molecules deposited on the surface (chemical mechanism). Recently appeared another types of mechanism connected with optical-mechanical coupling description for molecules at the substrate type of resonator cavities [1]. As SERS substrate we proposed to use a thin gold foil deposited on glass cover by special way to clear up the protein structure after its post-translational modification and compare with traditional SERS and Raman substrate. A droplet of 1 μl of 5 μM protein (human enzyme CYP4F11 before and under modification by 4-hydroxynonenal, toxic lipoperoxidation product) was used in our experiment. Previously it was impossible to register a signal from the same amount of protein on any other substrates. In the experiment we estimated the signal increase by 10 times or slightly more in comparison with quartz substrate. The surface of the foil appears to be quite heterogeneous (sharp protrusions, cavities and holes). Therefore, all three mechanisms possible contribute to the spectrum enhancement. A more accurate assessment of their contribution requires special research. Acknowledgement: Application to Call for a Department of Life Sciences and Systems Biology with D.D. No. 49/2022 of 05/25/2022 – Scholarship No. 23 of 05/25/2022 as part of the project: “The study of human CYP4F enzyme activity under malaria inhibitory factors” and Institute of Low-Temperature Physics and Structural Studies of PAN and Vitalii Boiko for Raman measurement. [1] Mikołaj K. Schmidt, Ruben Esteban, Felix Benz, Jeremy J. Baumberg and Javier Aizpurua, Faraday Discuss., 2017, 205, 31