| Abstract [eng] |
Surface-enhanced Raman spectroscopy (SERS) is one of the most sensitive vibrational spectroscopic method for in situ studies of biological systems in aqueous solutions. SERS provides the opportunity to study the structure and functions of the smallest structural parts of biological organisms and find their interrelations. However, large enhancement can be provided only by roughened surfaces and nanoparticles of Ag, Au or Cu metals. Consequently, Tian et al. suggested a novel SERS technique named ‘‘shell-isolated nanoparticle-enhanced Raman spectroscopy’’ (SHINERS). The method is based on enhancement of Raman signal by strong electromagnetic field provided by gold core nanoparticles surrounded by a few nanometer thick inert silica shell (Au@SiO2). The shell prevents chemical and electrical contacts among plasmonic core and probe substrate, analyst or environment. The main aim of this work: to synthesize the Au@SiO2 nanoparticles and apply them to probe the function and structure of self-assembled monolayers; to investigate the structure of yeast cells by surface-enhanced Raman spectroscopy using Au@SiO2 nanoparticles. The main results and conclusions. Yeasts Metschnikowia spp. are capable to produce a red pigment when iron (III) ions present in the growth media. They are potential biocontrol agents against various pathogenic microorganisms. In this work synthesized spherical gold nanoparticles with 46 ± 6 nm core size and SiO2 shell of ~ 3 nm thickness. In the process of the experiment shell-isolated nanoparticles were applied for studies of self-assembled monolayers and the structure and function of monolayers was determined. Synthesized Au@SiO2 nanoparticles allowed to obtain significantly enhanced SHINERS spectra of Metschnikowia spp. compared to the Raman spectra. Based on the results, the yeast cell wall and its functional elements (proteins, lipids, amino acids) were identified. It has been determined that spectra, when used Au@SiO2 NPs in combination with yeast cells, demonstrate the repeatability, vibrational bands do not change, there are no additional bands due to chemical interactions with nanoparticles. Amino acids, C-N, amide vibrations indicate the bioactivity of the living cell. Consequently, SHINERS technique allow to collect molecular level information from yeast for a better understanding of their cell wall biochemical structures. |
