Room-Temperature-Stabilized Alpha Tin Nanocrystals for In Vivo Toxicology Evaluation and Photothermal Therapy Corroborated by FFT Modeling

Herein, we unveil a remarkable finding for synthesizing room-temperature-stable, nontoxic, ultrasmall free-standing diamond cubic tin nanocrystals (α-Sn) with beta forms in the aqueous phase, avoiding conventional approaches that typically use toxic elements or large reactive substrates (Si/InSb) to stabilize α-Sn above 13 °C. Herein, for the first time, we demonstrate the successful synthesis of free-standing alpha tin with extraordinary stability up to 80 °C and in the aqueous phase at room temperature, which was supported by powder X-ray diffraction and X-ray photoelectron spectroscopy characterization methods. This synthetic approach eliminates the need to use hazardous materials, bulky substrates, and elevated temperatures, offering a safer, low-cost, and more sustainable alternative. Prepared α-Sn is characterized by extraordinary NIR absorption and a photothermal efficiency of 42.4%, making it a promising photothermal agent for cancer treatment upon shining low-power (0.5 W) 980 nm NIR light using a CW laser. Using fast Fourier transform weighted bright-field imaging, a mathematical model that foretells the behavior of live malignant cells before and after photothermal treatment has been constructed. Additionally, in vivo studies in rats backed by biochemical and histopathological analyses demonstrated no adverse effects on the vital organs of Wister rats. The unusual biocompatibility of the prepared α-Sn nanocrystals is demonstrated by a low hemolysis index (3.28 ± 0.53%) of the blood, which is far below the permissible limits of 5%. Current research unveils the strong potential of free-standing alpha-tin not only in the area of nanomedicine but also in other domains.