Application of LIBS technology for the biotissue diagnosis
Laser-induced breakdown spectroscopy (LIBS) is a technology for fast remote chemical analysis based on the excitation of plasma on the surface of a sample by a short laser pulse and the study of its spectral composition. The accuracy of LIBS allows to quantitatively characterize the elemental composition with high spatial and temporal resolution, as well as detect substances at their relatively low concentration – from 2 ppm . LIBS analysis compares favorably with many other analysis technologies: it is sensitive to elements with a low atomic number and it is sensitive to trace concentrations of materials. LIBS analysis can be an effective, remote, and safe method for diagnosing biotissue conditions and a wide range of diseases, including the diagnosis of onychomycosis . Early rapid diagnosis and treatment of onychomycosis are very important. If treatment is not done on time, the infection can progress penetrating deeper into the nail and destroying it. Using the LIBS technology, it is possible to identify various types of fungi and bacteria. LIBS analysis of vegetables and fruits can be used to identify the amino acid composition of fruits, mechanical damage, infectious diseases, etc . The main goal of this work was to estimate the possibility of using the eye-safe radiation of Q-switched Yb,Er:Glass laser for LIBS detection of the nail region affected by onychomycosis and determining the state of vegetables and fruits.
For in vitro nail diagnostics, one healthy nail sample and one human onychomycotic nail sample obtained from the same volunteer were used to avoid the influence of physiological, genetic, and other factors when comparing the spectra obtained for a healthy and diseased nail. In the study of the condition of fruits and vegetables one potato tuber and one apple were involved. LIBS analysis of potato and apple samples was taken from the light-yellow area (normal standard color) and from the darkened area. Pulp and peel of these fruits were analyzed. Plasma was excited on the surface of samples by pulses of compact passively Q‑switched Yb,Er: Glass-laser (Nela Ltd., Russia) with a wavelength of 1540 nm. The laser pulse energy was E=2.40 ± 0.05 mJ, the pulse duration was τ = 8 ns (FWHM). The emission spectra of laser-induced plasma were recorded using a "USB-2000" (OceanOptics, Inc., USA) fiber-optic spectrometer with spectral resolution of 1.5 nm. Pilot eye-safe LIBS detection of biological tissue condition was performed. The difference was found in the LIBS spectra of a healthy and onychomycosis-affected nail plate. The spectrum of onychomycotic nail contained unique lines additional to characteristic spectral lines of healthy nails. The difference was found in the LIBS spectra of normal and darkened pulp, as well as apple and potato peel. According to the spectra, it was found that apple and potatoes have a different set of micro- and macroelements. In addition, it was found that the lines of the darkened fruit pulp have a higher intensity than the normal pulp. Based on the data obtained, an original method and apparatus for the early rapid diagnosis of biotissues condition can be developed.
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