Porous Organosilica Nanoparticles Enable UV Blocking and Two-Photon Fluorescence Imaging

Abstract

Porous organosilica nanoparticles (PONs) are promising hybrid materials for a wide range of advanced applications, particularly in biomedical imaging, therapeutic delivery systems, and UV protection, due to their tunable organic-inorganic frameworks. However, integrating specific organic groups within PONs' structure, bearing function-enabling characteristics, remains challenging. Here we report the synthesis of novel PONs incorporating organic groups with UV-blocking and intrinsic anti-Stokes fluorescence capabilities, suitable for deep tissue imaging. The novel materials are prepared via co-condensation of a UV-absorbing triazine-based organosilane precursor with biphenyl-bridged silanes, yielding nanoparticles exhibiting broad UV protection (SPF ~26) and strong anti-Stokes fluorescence upon continuous wave and femtosecond laser excitation above 700 nm. Spectroscopic analysis revealed distinct excitation mechanisms: hot-band absorption under continuous wave and two-photon excitation fluorescence (TPEF) under pulsed irradiation. The nanoparticles demonstrated high biocompatibility toward human skin cells and enabled effective two-photon imaging of glioblastoma cells, showing timedependent cellular uptake. These multifunctional PONs combine UV shielding and advanced imaging capabilities, offering potential for applications in skin protection and nanomedicine, particularly for simultaneous imaging and therapeutic delivery.