Biological processes on the cellular scale are mediated to a great extent by interactions between car-bohydrate ligands and their receptors, e.g. cell-cell communication, pathogen invasion, or cell development. If presented on a “smart” polymer scaffold, such as soft switchable hydrogel particles, these interactions could be used to specifically target pathogens to enable new antibiotic strategies or other medical applications. As scaffolds we use thermoresponsive glycopolymers, based on poly N-isopropylacrylamide (PNIPAM) and poly (oligo(ethylene glycol)) (PEG) both decorated with mannose units exhibiting a volume phase transition temperature (VPTT) in a biologically applicable range. Using single cell force spectroscopy (SCFS) we study the interaction between bacteria and the microgels below and above the VPTT. We found that the adhesion of E.coli bacteria increases towards the collapsed particle layer which can be attributed to the increasing of mannose density on the individual particle surface (Figure 1). As the microgels present several ways of adjustment e.g. monomer, elasticity, and ligand density they can be tuned to function as a “capture and release” system to specifically select and cultivate carbohydrate binding cells.

Figure 1: An illustration of mannose-functionalized microgel layers and proposed change of <i>E.coli</i> binding upon varying the temperature below (left) and above (right) the LCST. Above the LCST polymer-polymer contacts are formed, water is expelled, and the microgel hydrodynamic radius decreases by a factor of 1.5-3. This leads to an overall increase of the mannose density, a smoother microgel surface and possibly also to a surface enrichment of mannose units increasing specific binding to the bacterial receptor FimH.

Figure 1: An illustration of mannose-functionalized microgel layers and proposed change of E.coli binding upon varying the temperature below (left) and above (right) the LCST. Above the LCST polymer-polymer contacts are formed, water is expelled, and the microgel hydrodynamic radius decreases by a factor of 1.5-3. This leads to an overall increase of the mannose density, a smoother microgel surface and possibly also to a surface enrichment of mannose units increasing specific binding to the bacterial receptor FimH.

Tanja Paul

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