(225b) Chemorepellent-Loaded Polymeric Nanocarriers for Biofilm Inhibition

Drug-resistant bacterial biofilms cause deadly infections and contaminate industrial food and drinking water systems. Widespread use of antimicrobial treatments has accelerated the emergence of drug-resistant bacteria. As a result, there is an urgent demand for novel technologies to target biofilm formation of specific pathogens.

Our approach exploits chemotaxis, the directed movement of bacteria in a chemical gradient, to control the critical initial step of biofilm formation: bacteria transport to a surface. Inducing chemotaxis requires non-toxic concentrations of chemorepellents, and this is advantageous to reduce selective pressures that cause resistance. However, the competitive dynamics between bacteria transport and chemorepellent release rates for efficient biofilm control are not well characterized. These dynamics were investigated with polymeric nanocarriers (NCs) that allowed for tunable chemorepellent loadings and release rates.

Nickel-loaded polymeric nanocarriers (NCs) were designed to localize a chemorepellent nickel (Ni²⁺) gradient to interfere with transport and subsequent attachment of Escherichia coli. NCs were formulated with Flash Nanoprecipitation to encapsulate Ni²⁺ into block co-polymers for polymeric NCs of controlled size and nickel loadings. Dynamic light scattering characterized the nanoparticles to be monodisperse and 100 nm in size. From an ICP-OES Ni²⁺ release study, we found the Ni²⁺ NCs have a rapid and pH-dependent Ni²⁺ release profile, with increased Ni²⁺ release at acidic pH. The Ni²⁺ concentrations released are within the sub-lethal range for E. coli.

In our biofilm assay, the Ni²⁺ gradient was localized by coating the Ni²⁺ NCs on a glass-bottom well plate, where E. coli HCB1 biofilms were grown and imaged with confocal microscopy. Ni²⁺ NCs significantly reduced the total E. coli biomass compared to the control case of NCs without Ni²⁺. Equivalent aqueous Ni²⁺ concentrations did not impact E. coli growth. A chemical-in-plug assay with Ni²⁺ NCs revealed that E. coli exhibits a chemorepellent response to Ni²⁺ NCs. These assays indicate that rapid Ni²⁺ release from Ni²⁺ NCs induces the non-toxic chemorepellent mechanism that prevents E. coli adhesion to the glass surface.

Future work aims to tune NC nickel loading and nickel release rates to develop the required dynamic criteria of chemorepellent treatments for effective biofilm inhibition. As microbes respond to specific chemorepellent compounds, this criteria will be useful to design chemorepellent treatments that target the transport and subsequent biofilm formation of specific pathogens.