Surface-Engineered Starch Magnetic Microparticles for Highly Effective Separation of a Broad Range of Bacteria

Polymeric magnetic particles (PMPs) have become a powerful tool for the separation and concentration of microorganisms from a heterogeneous liquid matrix. The functionalization of PMPs with polycationic polymers, such as chitosan, provides an effective means of capturing a broad spectrum of pathogenic bacteria through the intrinsic nature of chitosan interacting with the surface components of bacteria. Here, we report a fairly simple approach for the preparation of starch magnetic microparticles (SMMPs) through molecular rearrangement of short-chain glucans (SCGs) produced by enzymatic debranching of waxy maize starch. The surfaces of SMMPs were readily functionalized with chitosan through electrostatic interaction and hydrogen bonding. The chitosan-functionalized SMMPs (CS@SMMPs) showed high capture efficiency (>90%) for both Gram-positive and Gram-negative bacteria. To further investigate the mechanisms of chitosan-bacteria interaction, we employed model bacteria with different surface compositions. The outer-core lipopolysaccharides as well as the surface charge of bacteria were found to be important for the specific interactions of chitosan to bacteria. The biocompatible paramagnetic materials developed in this study would be promising in removing or separating bacteria from contaminated water for hygienic purposes or subsequent biochemical analysis of certain pathogenic bacteria present in the sample.