Lectin and E. coli Binding to Carbohydrate-Functionalized Oligo(ethylene glycol)-Based Microgels: Effect of Elastic Modulus, Crosslinker and Carbohydrate Density

Abstract

The synthesis of carbohydrate-functionalized biocompatible poly(oligo(ethylene glycol) methacrylate microgels and the analysis of the specific binding to concanavalin A (ConA) and Escherichia coli (E. coli) is shown. By using different crosslinkers, the microgels’ size, density and elastic modulus were varied. Given similar mannose (Man) functionalization degrees, the softer microgels show increased ConA uptake, possibly due to increased ConA diffusion in the less dense microgel network. Furthermore, although the microgels did not form clusters with E. coli in solution, surfaces coated with mannose-functionalized microgels are shown to bind the bacteria whereas galactose (Gal) and unfunctionalized microgels show no binding. While ConA binding depends on the overall microgels’ density and Man functionalization degree, E. coli binding to microgels’ surfaces appears to be largely unresponsive to changes of these parameters, indicating a rather promiscuous surface recognition and sufficiently strong anchoring to few surface-exposed Man units. Overall, these results indicate that carbohydrate-functionalized biocompatible oligo(ethylene glycol)-based microgels are able to immobilize carbohydrate binding pathogens specifically and that the binding of free lectins can be controlled by the network density.

Elastic modulus distribution in poly(N-isopopylacrylamide) and oligo(ethylene glycol methacrylate)-based microgels studied by AFM

“…Micro and nanoparticles composed of stimuli responsive polymers paved the way toward several promising applications, such as triggered drug delivery systems, [1][2][3][4][5] materials with advanced optical properties, 6,7 or bioactive coatings that are capable of responding to environmental parameters. [8][9][10][11][12][13] A very prominent type of responsive microparticles are thermosensitive microgels composed of polymers with a lower critical solution temperature (LCST). 14 When increasing the temperature above the LCST, the swollen microgels collapse due to the formation of polymer-polymer contacts and the partial removal of the hydration layer surrounding the polymer chains.…”

Specific Binding of Ligand-Functionalized Thermoresponsive Microgels: Effect of Architecture, Ligand Density, and Hydrophobicity

“…To obtain Man-functionalized microgels, the monomer N -ethylacrylamide-α- d -mannopyranoside (ManEAm) was added along with monomers constituting the LCST polymer backbone. The microgel architecture was varied by conducting the synthesis in the presence and absence of a dedicated crosslinker. ,, Without crosslinker, the P­(NIPAM) and P­(MEO 2 MA- co -OEGMA) networks are formed by chain transfer reactions, which leads to soft microgels with a low crosslinking degree . For P­(NIPAM), such self-crosslinked microgels show a homogeneous distribution of polymer segments .…”

“…E. coli express the Man-binding receptor FimH at their fimbriae, which enables their attachment to cells. ,,,, Here, we studied the E. coli-microgel aggregation via optical microscopy and visual inspection as a measure of specific microgel interactions (Figure ).…”

“…binding receptor FimH at their fimbriae, which enables their attachment to cells. 14,16,29,30,40 Here, we studied the E. colimicrogel aggregation via optical microscopy and visual inspection as a measure of specific microgel interactions (Figure 2). To study the effect of microgel collapse and the concurrent increase in Man density in the network, the experiments were conducted below and above the VPTT, at 20 and 37 °C.…”

“…For example, previous work on Man-decorated microgels showed selective binding and clustering of Escherichia coli above the VPTT, but a release of the bacteria was not possible below the VPTT. 15,29,30 We suggest that an increased shift in ligand density upon crossing the VPTT via reduced crosslinking could solve this problem. 16,31,32 Therefore, E. coli binding to Man presenting microgels with-and without a dedicated crosslinker (selfcrosslinked) will be compared here.…”