Application of Raman spectroscopy to study the inactivation process of bacterial microorganisms

Raman spectroscopy (RS) is one of the promising approaches for structural and functional studies of various biological objects, including bacterial microorganisms. Both traditional biochemical tests and genetic methods which require expensive reagents, consumables and are time-consuming are used for bacterial analysis. Spectroscopic methods are positioned as noninvasive, highly sensitive, and requiring minimal sample preparation. In this work we investigated the possibility of using the RS method using optical sensors based on gold anisotropic nanoparticles. The applicability of the method was demonstrated by studying the effect of a broad-spectrum cephalosporin antibiotic and an extract of Viburnum opulus L (VO) on Escherichia coli (E. Coli) colonies. The studies were performed by Raman spectroscopy using a Virsa spectrometer (Renishaw). Raman signal amplification was carried out using two original optical sensors proposed by the authors. To create sensors, we used a chemical method of depositing gold nanostars on APTES-modified quartz glasses and a physical method for creating sensors based on anodizing titanium surfaces. The results of the study showed the high sensitivity and information content of the proposed method. The possibility of using the RS method for studying the inactivation of bacterial microorganisms is shown. Spectral Raman bands of E. Coli were determined and identified before and after exposure to VO extract and antibiotic as a control. A decrease in the intensity of spectral modes corresponding to amino acids and purine metabolites was found in the average Raman spectrum of E. Coli after exposure to VO extract. For the first time, a study of the antimicrobial effect of an aqueous extract of VO fruits was carried out by the method of Raman scattering. It has been shown that the use of plant extracts, including VO fruit extracts, to inactivate the vital activity of bacterial colonies is a promising approach to the search for new alternative antibacterial agents. The results obtained are in good agreement with the already known scientific studies and confirm the effectiveness of the proposed method

Prospects for Raman spectroscopy in cardiology

Raman spectroscopy (RS) is a promising diagnostic method with high informative value and sensitivity. In addition, it is non-destructive and minimally invasive, and also requires minimal sample preparation, which opens up wide prospects for in vitro and in vivo use. There are some perspectives for this method in future cardiology practice. RS may allow to identify previously studied markers of cardiovascular disease, as well as to search for new ones. It is a sensitive method for the detection and biochemical assessment of early-stage atherosclerotic lesions and can be used in vivo. Of great interest is the possibility of using the RS to control the amount of eluted substance from drug-eluting stents to assess clinical efficacy. Study of platelet membranes using the RS technique revealed structural changes in patients with hypertension. This method makes it possible to assess myocardial viability in the border zone after myocardial infarction, and the obtained results correlate with the intraoperative data. More details about the prospects of using the RS will be described in the review

Photoluminescence properties of silica-based mesoporous materials similar to those of nanoscale silicon

Photoluminescence (PL) from composites of 7- and 15-nm sized silica nanoparticles (SNs) and mesoporous silicas (MSs) induced by 266- (4.66-) and 532-nm (2.33-eV) laser light has been studied at room temperature. The multiband PL from MSs in the range of 1.0-2.1 eV is evidenced to originate from isolated bulk and surface non-bridging oxygens (NBOs) and from NBOs combined with variously placed 1-nm sized pore wall oxygen vacancies (OVs). The nature and diversity of NBO light-emitters are confirmed by ab initio calculations. The PL from SNs exhibits only a short wavelength part of the bands (1.5-2.1 eV) originated from isolated bulk and surface NBOs. This fact indicates that the highly OV-bearing structures occur only in extremely thin ($\sim 1$ nm) silica layers. The similarity of spectroscopic properties of silica-based nanoscale materials to those of surface-oxidized silicon nanocrystals and porous silicon, containing silica-passivating layers of the same width, is discussed