# Effect of Particle Size and Surface Charge on Nanoparticles Diffusion in the Brain White Matter

## TL;DR

This study explores how nanoparticle size and surface charge affect their movement in the brain, offering insights for better drug delivery.

## Contribution

A new modeling framework combines geometric and particle tracing models to study nanoparticle diffusion in brain white matter.

## Key findings

- Negatively charged nanoparticles show increased diffusion with size until a threshold is reached.
- Nanoparticles with a Zeta potential less negative than -10 mV diffuse similarly in brain tissue and interstitial fluid.

## Abstract

Brain disorders have become a serious problem for healthcare worldwide. Nanoparticle-based drugs are one of the emerging therapies and have shown great promise to treat brain diseases. Modifications on particle size and surface charge are two efficient ways to increase the transport efficiency of nanoparticles through brain-blood barrier; however, partly due to the high complexity of brain microstructure and limited visibility of Nanoparticles (NPs), our understanding of how these two modifications can affect the transport of NPs in the brain is insufficient.

In this study, a framework, which contains a stochastic geometric model of brain white matter (WM) and a mathematical particle tracing model, was developed to investigate the relationship between particle size/surface charge of the NPs and their effective diffusion coefficients (D) in WM.

The predictive capabilities of this method have been validated using published experimental tests. For negatively charged NPs, both particle size and surface charge are positively correlated with D before reaching a size threshold. When Zeta potential (Zp) is less negative than -10 mV, the difference between NPs’ D in WM and pure interstitial fluid (IF) is limited.

A deeper understanding on the relationships between particle size/surface charge of NPs and their D in WM has been obtained. The results from this study and the developed modelling framework provide important tools for the development of nano-drugs and nano-carriers to cure brain diseases.