Today the most important problem of a transplantation is a rejection of healing skin tissue. The reason of a skin rejection is a high level of inflammation reaction and a slow rate of neoangeoginesis. A lot of methods exist for imaging of tissue healing extent, unfortunately, all of them have some drawbacks. Laser induced fluorescence is a non-invasive method which provides ambulatory and fast diagnosis. The concept was created and optimal parameters of spectral device were selected based on the experiment results. The non-invasive spectral device will allow determining a state of a healing skin and rate of skin tissue engraftment or rejection by its spectroscopic properties analysis using aluminum phthalocyanine nanoparticles (nAlPc). These nanoparticles are spectroscopically sensitive to inflammation reactions and begin to fluoresce while interacting with immune cells in inflamed tissue. The operation principle of developed device based on analysis of diffuse reflected light from a skin area. The device consists of the six red laser diodes. The red range laser irradiation allows dedicating autofluorescence of biological tissue components such as lipopigments, porphyrins. The fluorescence intensity of exogenous fluorophores helps identifying the degree of transplant engraftment because it is correlate with the inflammatory reactions intensity in a skin. End users will be burn centers, medicine facilities for monitoring of a postoperative sutures engraftment. It can also be used at home to assess the healing of small wounds.
The study of bioimaging with controlled depth using upconversion nanoparticles under near-infrared excitation was performed in this work. Monte Carlo simulation was performed to determine optimal distance between the fiber - source of laser radiation, and the receiving fiber for obtaining the signal from maximal depth in biological tissue. Also theoretical modeling of the spatial distribution of diffusely scattered radiation inside the tissue depending on wavelength is presented. Penetration depth for wavelengths corresponding to the upconversion luminescence was calculated.<p> </p> Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with rare earth ions. Measurements were performed using NaGdF<sub>4</sub> nanoparticles doped with Yb<sup>3+</sup>, Er<sup>3+</sup> and Tm<sup>3+</sup> rare earth ions, which demonstrated several luminescence bands from the blue (475nm) to the near-infrared (800 nm) regions of the spectrum under 980 nm excitation. The different penetration depth of various wavelengths in biotissue allows us to estimate the depth from which the signal was obtained using luminescence intensity ratio (LIR). Due to non-linearity of upconversion process, pumping power dependences of luminescence intensity was taken into account. The number of involved photons for each spectral band was estimated and intensity ratio of emission bands was calculated. Based on calculations and experimental measurements, the theoretical and experimental luminescence intensity ratio for different depths was estimated. The experimental study was performed on biological tissue phantoms containing Lipofundin® with red blood cells and has shown good agreement with calculations. The use of theoretically calculated LIR allows us to solve the inverse problem and estimate the depth from which the signal was obtained.
The development of express method for assessing the state of skin graft by the spectroscopic properties of tissue components involved in the healing of the affected skin or healing of skin grafts was carried out in present work. The proposed method for assessing the state of the skin by the spectroscopic properties of tissue components (using photosensitizers, fluorescent dyes (methylene blue and IcG) and nanophotosensitizers aluminum phthalocyanine nanoparticles (NP-AlPc) applied locally) will evaluate the physiological condition of the skin and assess the degree and rate of engraftment or rejection while also controlling several biochemical and physiological parameters in the entire graft, or the whole area of the skin lesions. Such parameters include the oxygenation of hemoglobin in the tissue microvasculature; the blood supply level; blood flow and lymph flow; assessment of intracellular metabolism; assessment of the cellular respiration type (aerobic/anaerobic).To assess the extent of inflammation the spectrally sensitive to biological environment nanoparticles of aluminum phthalocyanine (NP-AlPc) were also used.