Surface Functionalization-Dependent Physicochemical Interactions between Nanoparticles and the Biofilm EPS Matrix

The contribution of the biofilm extracellular polymeric substance (EPS) matrix to reduced antimicrobial susceptibility in biofilms is widely recognised.  As such, directly targeting the EPS matrix is a promising biofilm control strategy that allows for efficient disruption of the matrix to allow an increase in susceptibility to antibiofilm agents. To this end, engineered nanoparticles (NPs) have received considerable attention. However, the fundamental understanding of the physicochemical interactions occurring between NPs and the EPS matrix has not yet been fully elucidated. An insight into the underlying mechanisms involved when a NP interacts with molecules in the EPS matrix will aid in the design of more efficient systems for biofilm control. The use of highly specific fluorescent probes in confocal laser scanning microscopy (CLSM) to illustrate the spatial distribution of EPS macromolecules within the biofilm is demonstrated. Three-dimensional (3D) colocalization analysis was used to assess the affinity of differently functionalized silica NPs (SiNPs) for specific EPS macromolecules from Pseudomonas fluorescens biofilms. Results show that both the charge and surface functional groups of SiNPs dramatically affect the extent to which SiNPs interact and localize with EPS macromolecules, including proteins, polysaccharides, and DNA. This research not only develops an innovative strategy for biofilm-nanoparticle interaction studies but also provides a platform on which to build more efficient NP systems for biofilm control.