ИСТИНА

Silicon is material of high biocompatibility, bioavailability, biodegradability and low toxicity [1]. For biomedical applications it would be better to employ silicon nanoparticles (SiNP) of spherical shape, with their size being less than 150 nm. Photothermotherapy (PTT) techniques are based on using inorganic nanomaterials as a thermal coupling agents for a biological sample. Nanoparticles injected in a tissue play the role of additional elastic scattering and absorption centers. As a result stable and localized heating more than 40°C can be achieved [2]. We developed a two-stage technique to obtain suspensions of SiNP in concentrations that are desirable for hyperthermia method. The first stage is the electrochemical etching of crystalline silicon wafers in order to obtain a layer of porous silicon (PS). The second stage is picosecond laser ablation of PS in ethanol or liquid nitrogen and SiNP formation as the result. Lower ablation threshold in PS results in higher yield of SiNP than ablation of crystalline silicon Atomic-force microscopy of obtained samples demonstrated formation of the SiNP with the size ranges of 5–100 nm and 7–60 nm for ablation in ethanol and liquid nitrogen, respectively. Relatively small sizes of the produced nanoparticles indicate low efficiency of agglomeration of the ablation products into nanoparticles in the used buffer environments. Scanning electron microscopy inspection indicated that all types of fabricated Si-NPs have a smooth surface, without noticeable surface roughness, and a shape close to spherical. We used Monte Carlo simulation method to obtain initial thermal distribution as a result of light absorption from continuous laser source. Then we solved time-dependent heat equation through MATLAB Partial Differential Equation Toolbox. The simulation of heat maps was performed for a sample tissue with suspensions of SiNP taking into account the particles size distribution obtained previously in experiment. This work was supported by Russian Science Foundation (grant №19-12-00192) REFERENCES: [1] M.Yu. Kirillin, E.A. Sergeeva et al., Laser Physics (251), P. 075604 (2015) [2] C. Hong, J. Lee et. al., Nanoscale research letters (6) 321 (2011)