Fig. 4: Miniaturized Raman system used for biomedical Raman microscopy applications.

a Image from the CMOS sensor of the SERS signal of BPE; the zoomed region shows that the spectrum is compressed into one row on the sensor, b illustration of the cross slit design of miniaturized Raman spectrometer that is capable for confocal measurements, c optomechanical design of miniaturized Raman microscope based on miniaturized Raman spectrometer, d Raman microscopy image of polystyrene beads at the size of 1 µm obtained with Zeiss objective 100×, NA = 0.95, e depth scan by our miniaturized Raman microscope (equipped with Zeiss objective 100×, NA = 0.95) through the surface of SERS substrate with BPE analyte at concentration 100 µM, f axial (black curve) and lateral intensity distribution of Raman signal as a function of sample displacement (dotted white lines in (d, e) indicate areas used for plotted axial and lateral intensity profiles); data demonstrate diffraction-limited spatial resolution, g SERS maps of MTX deposited on silver coated NP SERS substrates at concentration of 25 µM, h, i photographs demonstrating the process of analyte deposition, j SERS spectra of MTX at different concentrations (0–75 µM) obtained after the averaging of SERS signals collected by mapping of the SERS chip, k, I result of PLS calibration for MTX quantification, m Raman spectra of different bacteria obtained after the averaging of the Raman signal from Raman maps, n photograph of miniaturized Raman microscope during Raman mapping of bacteria samples on CaF2 cover glass, o CMOS image of the measurement process of bacteria demonstrating sharp focusing of Raman signal in vertical dimension of the sensor under a laser excitation wavelength of 785 nm, p microscopy image of bacteria deposited on CaF2 cover glass with areas selected for Raman mapping of bacteria (areas 1–3) and Raman mapping of cover glass background (areas 4), q confusion matrix of bacteria identification built as a result of machine learning data analysis of Raman maps of bacteria. E. coli 25: Escherichia coli strain ATCC 25922; E. coli 35: Escherichia coli strain ATCC 35218; MSSE: methicillin-sensitive Staphylococcus epidermidis strain ATCC 14990; MRSE: methicillin-resistant Staphylococcus epidermidis strain ATCC 35984; S. lugdunensis: Staphylococcus lugdunensis; S. homolyticus: Staphylococcus homolyticus.