Raman Spectroscopy and Its Modifications Applied to Biological and Medical Research

Abstract

Nowadays, there is an interest in biomedical and nanobiotechnological studies, such as studies on carotenoids as antioxidants and studies on molecular markers for cardiovascular, endocrine, and oncological diseases. Moreover, interest in industrial production of microalgal biomass for biofuels and bioproducts has stimulated studies on microalgal physiology and mechanisms of synthesis and accumulation of valuable biomolecules in algal cells. Biomolecules such as neutral lipids and carotenoids are being actively explored by the biotechnology community. Raman spectroscopy (RS) has become an important tool for researchers to understand biological processes at the cellular level in medicine and biotechnology. This review provides a brief analysis of existing studies on the application of RS for investigation of biological, medical, analytical, photosynthetic, and algal research, particularly to understand how the technique can be used for lipids, carotenoids, and cellular research. First, the review article shows the main applications of the modified Raman spectroscopy in medicine and biotechnology. Research works in the field of medicine and biotechnology are analysed in terms of showing the common connections of some studies as caretenoids and lipids. Second, this article summarises some of the recent advances in Raman microspectroscopy applications in areas related to microalgal detection. Strategies based on Raman spectroscopy provide potential for biochemical-composition analysis and imaging of living microalgal cells, in situ and in vivo. Finally, current approaches used in the papers presented show the advantages, perspectives, and other essential specifics of the method applied to plants and other species/objects.

Keywords: Raman spectroscopy; Surface-enhanced Raman Spectroscopy; carotenoids; lipid droplets; microalgae.

Figure 1

Application of RS in different research.

Figure 2

Energy transition of Rayleigh and Raman scattering.

Figure 3

“Family tree” of the RS. The relatively simple RS is the root of the complex surface-enhanced, resonance-enhanced time—and spatially-resolved techniques. Abbreviations: SERS,  Surface-enhanced Raman Spectroscopy; CARS, coherent anti-Stokes Raman spectroscopy; RRS, resonance-enhanced Raman scattering; SORS, spatially offset Raman spectroscopy. Modified from Buckley and Ryder [9].

Figure 4

Schematic view of biomedical RS application. Adapted from Desroches et al. [37].

Figure 5

A schematic of the experimental set-up of a typical Raman spectrometer and schematic showing applicability of RS to different aspects of algae.

Figure 6

Raman spectra of various lipid molecules of Botryococcus braunii [23].

Figure 7

The schematic view in lipid characterisation of microalgae. Bioprospecting of C. reinhardtii is performed to generate algal samples with lipid content. The mutagens are sorted by FACS based on the fluorescence of a dye to select cells with high lipid content. The selected cells and mutants are then screened using CRM. This method allows for rapid characterisation of lipids. The spectra yield depends on the number of C=C bonds and the length of the hydrocarbon chains of the lipid molecules. This workflow enables rapid characterisation of cells for molecular traits that are important for the production of biodiesel. Modified from Sharma et al [18].

Figure 8

The Raman spectrum of carotenoid [132], chlorophyll [129], and triglyceride and the mean spectra acquired for starved C. sorokiniana and starved N. oleoabundans in the wavenumber regions of 750–1750 cm⁻¹ and 2450–3150 cm⁻¹. Modified from Shutova et al. [134].