Spectral Flow Cytometry

Figure 1: Schematic of the particles in the fluid flow and interaction region of the laser within the flow cell. A key and continuing goal in the development of flow cytometry techniques is the ability to measure ever more parameters for each particle under test. Work carried out by Prof John Nolan’s group at La Jolla Bioengineering Institute, and reported recently by Watson et. al.[1] in Cytometry A,outlines the development and operation of a Raman Spectral Flow Cytometer (RSFC), which is perhaps the most radical and challenging approach to current efforts in spectral flow cytometry.In their ‘proof of principle’ system, they bring together Raman spectroscopy, via surface enhanced Raman (SERS),and conventional flow cytometry, by substituting a dispersive-optic spectrograph with multichannel detector (CCD), in place of the traditional mirrors/beam splitters, filters and photomultipliers (PMT) of conventional flow cytometers. They demonstrate a system of sufficient sensitivity to acquire and analyze SERS spectra with good spectral resolution from samples consisting of nanoparticle SERS tags bound to microspheres. The functionality and power of the system is illustrated using two analytical methods, virtual bandpass filtering and principal component analysis (PCA), to distinguish between the different Raman species within their test samples.