Amphiphilic Photoluminescent Porous Silicon Nanoparticles as Effective Agents for Ultrasound-Amplified Cancer Therapy

This study investigates the use of photoluminescent amphiphilic porous silicon nanoparticles (αϕ-pSiNPs) as effective ultrasound (US) amplifiers for cancer sonodynamic theranostics. αϕ-pSiNPs were synthesized via a novel top-down approach involving porous silicon (pSi) films electrochemical etching, borate oxidation, and hydrophobic coating with octadecylsilane (C18), resulting in milling into nanoparticles with hydrophilic exteriors and hydrophobic interiors. These properties promote gas trapping and cavitation nucleation, significantly lowering the US cavitation threshold and resulting in selective destruction of cancer cells in the presence of nanoparticles. Efficient internalization of αϕ-pSiNPs in cell cytoplasm was demonstrated by their intrinsic photoluminescence, activated by partial oxidation of mesoporous silicon films in borate solutions, which resulted in quantum confinement of excitons in 2-5 nm Si quantum dots/wires. Combined with US exposure above the cavitation threshold, αϕ-pSiNPs caused a significant decrease in cell viability through mechanical stretching and microflows generated by oscillating microbubbles. Meanwhile, αϕ-pSiNPs exhibit high biocompatibility up to concentrations of 1 mg/mL without US activation. Their photoluminescent properties facilitate bioimaging, while their US contrast capabilities may enhance both imaging and therapy. The dual functionality of αϕ-pSiNPs supports a theranostic approach, enabling simultaneous diagnostics and treatment with a single agent. This study underscores the potential of αϕ-pSiNPs in sonodynamic therapy and bioimaging, offering a promising strategy for effective and safe anticancer therapy.