Anomalous diffusion of nanoparticles in the spatially heterogeneous biofilm environment

Bart Coppens; Tom E R Belpaire; Jiří Pešek; Hans P Steenackers; Herman Ramon; Bart Smeets

doi:10.1016/j.isci.2023.106861

Anomalous diffusion of nanoparticles in the spatially heterogeneous biofilm environment

iScience. 2023 May 13;26(6):106861. doi: 10.1016/j.isci.2023.106861. eCollection 2023 Jun 16.

Authors

Bart Coppens¹, Tom E R Belpaire¹, Jiří Pešek², Hans P Steenackers³, Herman Ramon¹, Bart Smeets¹

Affiliations

¹ Division of Mechatronics, Biostatistics, and Sensors, KU Leuven, 3001 Leuven, Belgium.
² Team SIMBIOTX, Inria Saclay, 91120 Palaiseau, France.
³ Centre for Microbial and Plant Genetics, KU Leuven, 3001 Leuven, Belgium.

Abstract

Biofilms contain extracellular polymeric substances (EPS) that provide structural support and restrict penetration of antimicrobial treatment. To overcome limited penetration, functionalized nanoparticles (NPs) have been suggested as carriers for antimicrobial delivery. Using microscopy, we evaluate the diffusion of nanoparticles in function of the structure of Salmonella biofilms. We observe anomalous diffusion and heterogeneous mobility of NPs resulting in distinct NPs distribution that depended on biofilm structure. Through Brownian dynamics modeling with spatially varying viscosity around bacteria, we demonstrated that spatial gradients in diffusivity generate viscous sinks that trap NPs near bacteria. This model replicates the characteristic diffusion signature and vertical distribution of NPs in the biofilm. From a treatment perspective, our work indicates that both biofilm structure and the level of EPS can impact NP drug delivery, where low levels of EPS might benefit delivery by immobilizing NPs closer to bacteria and higher levels hamper delivery due to shielding effects.

Keywords: Nanoparticles; Nanoscience; Nanotechnology.