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The aim of the study was to develop a diagnostic method for the quantitative determination of the main components of cartilage tissue of various types based on multivariate IR spectral analysis and verification of data using classical chemical analysis., Materials and Methods: Cartilages of the nasal septum, knee joint, rib, and nucleus pulposus of the intervertebral disc, as well as trypsinized and defective cartilage samples, were examined as samples. The IR spectra of the cartilage samples, as well as calibration mixtures of collagen and chondroitin sulfate, were obtained. The IR spectra were collected using the attenuated total reflectance techniques, and their processing was performed using the TQ Analyst software and the principal component regression calibration technique. Based on calibration dependence, the K sp coefficient was determined as the ratio of the mass fractions of collagen and chondroitin sulfate. Its value was compared with the value of K chem , equal to the ratio of the mass fractions of collagen and chondroitin sulfate, obtained using the classical chemical analysis of these substances., Results: The IR spectra of cartilage tissues are a superposition of the IR spectra of collagen and chondroitin sulfate and qualitatively reflect their composition. A change in the ratio between the relative intensities of the characteristic bands of compounds in the IR spectrum is obvious only with a significant change in the content of these compounds in cartilage. This change occurs after trypsinization, when K sp increases from 0.88±0.05 ( K chem ~0.8) to 4.55. The use of a calibration model with a complete analysis of the cartilage IR spectrum made it possible to determine the difference in the ratio of the main components in the matrix of different samples in the absence of obvious changes in the IR spectra. Thus, a statistically significant decrease in the content of chondroitin sulfate in degraded articular cartilage ( K sp =4.4±1.8; K chem ~5.5) was shown compared with intact samples ( K sp =2.8±1.1; K chem ~2.6)., Conclusion: IR spectrometric express analysis of cartilage tissue employing the principal component regression method allows a correct determination of the ratio of the main components in the cartilage matrix, those of collagen and glycosaminoglycans. The proposed technique includes one measurement, does not require prolonged and laborious sample preparation, does not require long, multi-stage and laborious chemical manipulations to determine each of the components, and makes it possible to determine the features and changes in the composition for a large set of samples of cartilage tissue of different types. In future, this approach can be used for non-invasive diagnostics of cartilage tissue., Competing Interests: No conflicts of interest are declared.

The aim of the study was to design a construct based on a nasal septal cartilage plate providing required cell differentiation in different layers to replace a deep osteochondral defect and develop an algorithm of chemical and physical effect sequence to create non-immunogenic two-layer porous structure with requisite elasto-mechanical properties., Materials and Methods: The plates derived from porcine nasal septal hyaline cartilage covered by perichondrium were multi-stage treated including freezing, equilibrating in a hypotonic saline solution (type I specimens); trypsinization, point IR-laser effect, re-trypsinization (type II specimens); a stabilizing effect of crosslinking agents - glyceraldehyde/ribose in an acidic medium - washing (type III specimens).For all type specimens:there were established stability parameters (collagen denaturation temperature using a thermal analysis; and Young's modulus using a mechanical analysis);there were determined morphological characteristics using light and polarization microscopy with classical staining and nonlinear optical microscopy in second-harmonic generation mode., Results: Thermal, mechanical, and morphological properties in type I specimens slightly differed from those of the initial nasoseptal system. A considerable part of cells had destroyed membranes.In type II specimens, thermal stability of collagen frame was significantly lower; Young's modulus decreased more than fourfold compared to type I specimens. Collagen structure of hyaline cartilage appeared to be disarranged, although the morphological differences of the hyaline part and perichondrium preserved. The construct matrix was almost completely decellularized. Successive exposure to laser radiation and trypsin resulted in the formation of partial holes in the matrix, ~100 μm in diameter.In type III specimens, both the thermal stability of the collagen frame and Young's modulus (E) increased. Glyceraldehyde was more effective than ribose, E having reached the value typical for intact hyaline cartilage. Collagen fibers in type III specimens were thicker than in type I and II specimens. The morphological differences of the hyaline part and perichondrium and partial holes were preserved., Conclusion: Due to sequential treatment by salts, trypsin, IR-laser radiation, and nontoxic crosslinking agents, nasal septal cartilage plate forms porous acellular construction consisting of two layers formed by type I (from perichondrium) and type II (from hyaline part) collagen fibers. In the present construction, stability, mechanical properties, and size of the partial holes can be assigned for cell colonization. It enables to use the construction to replace articular cartilage defects., Competing Interests: Conflicts of interest. The authors have no conflicts of interest related to the present study.

Speckle-contrast monitoring of laser-mediated tissue modification is examined for the specific case of delivery of speckle-modulated light from the tissue to detector (CCD camera) with a fiber-optic element (bundle). The influence of the transfer properties of a bundle-based optical system on the decorrelation rate of detected dynamic speckles is analyzed. Compared with the widely used method on the base of speckle-contrast analysis in the image plane, the considered technique is characterized by a more pronounced correlation between variations of the contrast of time-averaged speckle patterns and changes in the temperature of the modified tissue. The possibility of characterization of the modification kinetics (in particular, by the evaluation of the characteristic activation energy) using the developed speckle technique is demonstrated.