# The Impact of Silicon Nanoparticle Porosity on Their Ability to Sensitize Low-Intensity Medical Ultrasound

## TL;DR

Porous silicon nanoparticles can enhance ultrasound-based cancer treatment by reducing cell viability without significant toxicity.

## Contribution

The study demonstrates that porosity in silicon nanoparticles is crucial for their effectiveness as sonosensitizers in sonodynamic therapy.

## Key findings

- Porous silicon nanoparticles have nanocrystals of ~4 nm and 15 nm pores, while non-porous ones have 10–50 nm dense nanocrystals.
- Porous nanoparticles combined with low-intensity ultrasound significantly reduced Hep2 cell viability, unlike non-porous ones.
- The effect is linked to cell membrane destruction and possible apoptosis activation without inherent nanoparticle toxicity.

## Abstract

This study investigates the role of porosity in silicon nanoparticles’ ability to act as sonosensitizers for sonodynamic therapy of malignant tumors.

Structural analysis showed that porous nanoparticles are composed of nanocrystals approximately 4 nm in size and contain 15 nm pores, whereas non-porous nanoparticles have a dense structure with nanocrystals ranging from 10 to 50 nm. Porous nanoparticles exhibit pronounced photoluminescent properties, associated with quantum confinement effects in their small nanocrystals.

The cytotoxicity of the nanoparticles was investigated in vitro using Hep2 cells. The results showed that both porous and non-porous nanoparticles in the studied concentration range (2–500 μg/ml) are non-toxic. Low-intensity ultrasound (0.88 MHz, <1 W) also does not have a toxic effect on the cells. However, the combined use of porous nanoparticles and ultrasound led to a significant decrease in cell viability, which was not observed when non-porous nanoparticles were used. This effect is associated with mechanical destruction of the cell membranes, as well as the potential activation of additional cell death mechanisms, such as apoptosis.

The results highlight the importance of porosity as a key factor determining the effectiveness of silicon nanoparticles as sonosensitizers. The high efficiency, low toxicity, and unique structural properties of porous nanoparticles make them a promising material for further research and development of targeted, non-invasive treatments for malignant tumors in the context of sonodynamic therapy.