Raman and infra-red microspectroscopy: towards quantitative evaluation for clinical research by ratiometric analysis.
Biomolecular structure elucidation is one of the major techniques for studying the basic processes of life. These processes get modulated, hindered or altered due to various causes like diseases, which is why biomolecular analysis and imaging play an important role in diagnosis, treatment prognosis and monitoring. Vibrational spectroscopy (IR and Raman), which is a molecular bond specific technique, can assist the researcher in chemical structure interpretation. Based on the combination with microscopy, vibrational microspectroscopy is currently emerging as an important tool for biomedical research, with a spatial resolution at the cellular and sub-cellular level. These techniques offer various advantages, enabling label-free, biomolecular fingerprinting in the native state. However, the complexity involved in deciphering the required information from a spectrum hampered their entry into the clinic. Today with the advent of automated algorithms, vibrational microspectroscopy excels in the field of spectropathology. However, researchers should be aware of how quantification based on absolute band intensities may be affected by instrumental parameters, sample thickness, water content, substrate backgrounds and other possible artefacts. In this review these practical issues and their effects on the quantification of biomolecules will be discussed in detail. In many cases ratiometric analysis can help to circumvent these problems and enable the quantitative study of biological samples, including ratiometric imaging in 1D, 2D and 3D. We provide an extensive overview from the recent scientific literature on IR and Raman band ratios used for studying biological systems and for disease diagnosis and treatment prognosis.
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560 012, India. umapathy@ipc.iisc.ernet.in.
Srividya
S
Kumar
Centre for Biosystems Science and Engineering, Indian Institute of Science, Bangalore-560012, India.
Taru
T
Verma
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560 012, India. umapathy@ipc.iisc.ernet.in.
Ria
R
Mukherjee
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560 012, India. umapathy@ipc.iisc.ernet.in.
Freek
F
Ariese
Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560 012, India.
Kumaravel
K
Somasundaram
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560 012, India. umapathy@ipc.iisc.ernet.in and Department of Instrumentation and Applied Physics, Indian Institute of Science, Bengaluru 560 012, India.
Siva
S
Umapathy
D035843:Biomedical Research; D019411:Clinical Laboratory Techniques; D003952:Diagnostic Imaging; D006801:Humans; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*