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Biological tissue is complex substance which characterization demands combination of several spectroscopic techniques. Spectroscopy enables real-time label-free chemical and structural evaluation of samples for medical diagnostics in situ and in vivo. Fiber-optic probes provide flexible, sterilizable, and compact solutions for simultaneously analyzing tissue samples with several spectroscopic modalities. Modern fiber spectroscopy seamlessly covers entire wavelength range from 0.3µm with silica fibers to 20µm with chalcogenide, silver halide PIR fibers, and hollow glass waveguides. Here we present our latest achievements in developing multispectral compact fiber-optic probes for biomedical applications. We focused on combining all four key spectroscopic modalities (NIR, MIR, Raman, and Fluorescence) in single fiber probe tip. In preliminary studies of clinical bio-samples, combination of NIR diffuse reflection or MIR absorption spectroscopy with fluorescence spectroscopy gives synergy effect in differentiation of diseased and normal tissues. In our Raman experiments, we evaluate primary signals together with fluorescence background, which helps enhance analysis accuracy. Combined with advanced chemometrics data analysis, this concept enables the development of customized spectral fiber sensors based only on several wavelengths, hence their simple design, small size, high speed, and cost savings. It is possible to make rapid measurements directly in the operation theater by using tiny (<200 µm OD) but robust monofiber disposable Raman needle probes. Our recent experiments have shown the possibility of combining mid-IR ATR absorption and Raman spectroscopy in one compact fiber-optic probe. These advances turn fiber-optic multispectral probes into universal tools for any biomedical application requiring analysis of complex tissue.
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