The goal of this research is to develop a method for separating bacterial pathogens from liquids using non-toxic biopolymer nanoparticles at low concentrations. The rapid formation of large bacteria clusters facilitates separation. Chitosan and chitosan-coated alginate nanoparticles are produced by ionic gelation methods under mild, room-temperature conditions. Chitosan and alginate are edible, biocompatible polymers, and are frequently used in food applications.

Chitosan and chitosan-coated alginate nanoparticles with different surface charges were mixed with dilute Escherichia coli PBS solutions and the bacteria-nanoparticle interactions were observed by phase contrast and fluorescence microscopy. We study how the interactions depend on particle zeta potential (range from -32 to 50 mV), particle concentration and bacterial concentration. We observe rapid aggregation and restricted microbial motion when bacteria interact with nanoparticles that have a highly positive zeta potential, contrasting with the negative bacterial surface charge. Results will be presented on the cluster size and formation process.