Cell identification by Raman spectroscopy has evolved to be an attractive complement to established optical techniques.
Raman activated cell sorting (RACS) offers prospects to complement the widely applied fluorescence activated cell
sorting. RACS can be realized by combination with optical traps and microfluidic devices. The progress of RACS is
reported for a cellular model system that can be found in peripheral blood of tumor patients. Lymphocytes and
erythrocytes were extracted from blood samples. Breast carcinoma derived tumor cells (MCF-7, BT-20) and acute
myeloid leukemia cells (OCI-AML3) were grown in cell cultures. First, Raman images were collected from dried cells
on calcium fluoride slides. Support vector machines (SVM) classified 99.7% of the spectra to the correct cell type.
Second, a 785 nm laser was used for optical trapping of single cells in aqueous buffer and for excitation of the Raman
spectrum. SVM distinguished 1210 spectra of tumor and normal cells with a sensitivity of >99.7% and a specificity of
>99.5%. Third, a microfluidic glass chip was designed to inject single cells, modify the flow speed, accommodate fibers
of an optical trap and sort single cells after Raman based identification with 514 nm for excitation. Forth, the
microfluidic chip was fabricated by quartz which improved cell identification results with 785 nm excitation. Here,
partial least squares discriminant analysis gave classification rates of 98%. Finally, a Raman-on-chip approach was
developed that integrates fibers for trapping, Raman excitation and signal detection in a single compact unit.