IDBR: Development of a time-gated Raman/fluorescence micro-spectroscopy instrument for biological applications

University Of California-Davis, Davis CA

Investigators

Abstract

Raman spectroscopy is the inelastic scattering of photons by molecular bonds, and therefore enables chemically-specific measurements within a sample without the use of external labels. This unique characteristic gives Raman-based techniques the potential to be used in a variety of biological research applications. However, many of the chemical components within the biological material are fluorescent, acting as a background and thus severely limiting the use of Raman spectroscopy for these applications. Although there have been attempts to reduce this background, only an optical time-gated approach can be sufficiently effective. Since the Raman signal occurs almost instantaneously with the excitation light while the fluorescence is delayed by several nanoseconds, lasers with pulses in the range of several picoseconds can be used for his purpose. A time gate that opens only for the duration of the Raman signal and closes before the background fluorescence is produced can be built by using a nonlinear medium and highpower laser pulses. This combination allows for the measurement of Raman spectra in the presence of a strong fluorescence background and opens up new potential applications of Raman spectroscopy for biological research such as (i) non-invasive characterization of the chemical composition of the endogenous fluorophores in bacteria, cells and tissues, (ii) understanding cellular processes and diseases such as cancer, vascular or neurodegenerative diseases by using natural markers, (iii) developing new probes that can be used both as fluorescence and Raman labels, (iv) noninvasive medical sensors for blood analytes such as glucose sensors for diabetes treatment. This technique will have a significant impact on related fields such as analytical chemistry, biomedicine, pharmacology, forensics, food safety, agriculture, biofuel research, environmental monitoring, and bio-defense.Outreach will involve students and educators at all levels, from middle school to postdoctoral, as well as representatives and participants from the biotechnology industry.Further information can be requested from the PI.