Raman Activated Cell Counting for Profiling Carbon Dioxide Fixing Microorganisms

M. Liu, P. Ashok, K. Dholakia, and W. E. Huang

Journal of Physical Chemistry A 116(25), 6560-6563 (2012)

doi: 10.1021/jp212619n

Raman microspectroscopy is a label-free and nondestructive technique to measure the intrinsic chemical profile of single cells. The naturally weak Raman signals hampered the application of Raman spectroscopy for high-throughput measurements. Nearly all photosynthetic microorganisms contain carotenoids that are active molecules for resonance Raman at a 532 nm excitation wavelength. Hence, the acquisition time for a single photosynthetic microorganism can be as short as 1 ms. The carotenoid bands in Raman spectra of photosynthetic microorganisms utilizing 13CO2 shifted when compared to the spectra of cells utilizing 12CO2. Here, a mixture of 12C- and 13C-cyanobacterial cells were counted using a microfluidic-device-based Raman-activated cell counting procedure to prove the concept that Raman spectroscopy can be used as a high-throughput method to profile a cell population.