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“Fluorescence guidance is a method of choice for rapid pre-screening of white blood cells in blood smears on glass before O-PTIR spectra can be collected… I think it’s time for more advanced technique and optical photothermal infrared spectroscopy can be part of this.” – Dr. Christoph Krafft, Leibniz Institute of Photonic Technology
The authors address a critical gap in hematological diagnostics where current automated blood count methods fail in 10-25% of cases, requiring time-consuming manual microscopy analysis using century-old staining protocols pioneered by Paul Ehrlich. Dr. Krafft from the Leibniz Institute of Photonic Technology demonstrates how fluorescence-guided O-PTIR spectroscopy can modernize blood cell analysis by providing rapid, label-free chemical identification of white blood cell subtypes on standard glass slides.
The research team reports successful differentiation of leukemia cell lines using O-PTIR, with second derivative analysis revealing over 25 distinct spectral bands from four different cell lines (THP1, Jurkat, Raji, and HL60) in aqueous buffer. The authors demonstrate that O-PTIR imaging at discrete wavenumbers (1090 cm⁻¹ for nucleic acids, 1550 cm⁻¹ for proteins, 1745 cm⁻¹ for lipids) provides cell-specific variations that enable robust differentiation. Importantly, they show superior spatial resolution compared to traditional FTIR, with O-PTIR resolving individual red blood cells and fine cellular structures that cannot be detected with conventional IR microscopy’s ~10 micrometer resolution.
Dr. Krafft’s team successfully implemented fluorescence pre-screening to identify white blood cells with inherent contrast in blue and green channels, completing fluorescence imaging in less than one second. The authors report that hierarchical cluster analysis of 241 O-PTIR spectra from blood smears yielded four distinct cell populations correlating well with flow cytometry standards: 10% monocytes, 37% lymphocytes, and 53% granulocytes. They demonstrate that spectral markers including elevated CH2 bands and amide band shoulders distinguish granulocytes from other cell types, with biochemical explanations linking these differences to cytoplasm-to-nucleus ratios.
The research establishes fluorescence-guided O-PTIR as a transformative approach for clinical hematology, combining rapid cell identification with detailed chemical characterization. The authors conclude this method represents a significant advancement toward automated spectroscopic analysis of blood disorders, infections, and leukemia, positioning O-PTIR to replace manual microscopy workflows while maintaining compatibility with standard laboratory glass substrates.
