Quantitation of acute monocytic leukemia cells spiked in control monocytes using surface-enhanced Raman spectroscopy

Surface enhanced Raman spectroscopy (SERS) was used to quantify leukemia cells spiked in control cells. The novelty consists of preparing cell lysates by ultrasound sonication and mixing with silver nanoparticles which allow reproducible interaction of intracellular constituents and nanoparticles. SERS spectra of these mixtures give accurate information about intracellular molecules, mainly proteins and nucleic acids, for qualitative analysis and cell identification. Here, samples from acute monocytic leukemia cell line, THP-1, and control monocytes from three donors served as in vitro model system for leukemia. For quantitative analysis, seven mixtures containing different percentile amounts of leukemia lysates and lysates from control monocytes were prepared ranging from 0% to 100% and SERS spectra were measured. More intense spectral contributions of proteins relative to nucleic acids correlated with the larger cytoplasm to nuclei ratio of leukemia cells than control monocytes. Experimental SERS spectra were fitted by non-negative least square (NNLS) algorithm to calculate percentile amounts of each cell type and to determine their contributions to the mixtures. Even small amount (5 µl) of leukemia cells was detected in a mixture with control monocytes (360 µl) which represent 10% of leukemia cells considering their twofold larger diameter and eightfold larger volume. As this value is well below the threshold of 20% blast cells for leukemia diagnosis, this approach is very promising for both qualitative and quantitative analysis of human cell mixtures. This study demonstrates the potential of SERS and NNLS fitting as a rapid method for diagnosis of acute monocytic leukemia in human blood or bone marrow samples because only a single spectrum is required.