Blocked bacteria escape by ATRP grafting of a PMMA shell on PVA microparticles

This paper reports on the preparation and characterization of living composites consisting of poly(vinylalcohol) (PVA) hydrogel microparticles with living bacteria and a shell of poly(methyl methacrylate) (PMMA). The grafting of the PMMA shell is accomplished in the presence of living bacteria by surface polymerization of PMMA using atom transfer radical polymerization (ATRP). The PMMA shell prevents the uncontrolled bacterial escape from the hydrogel microparticles, which otherwise marks a major problem of these composites. The encapsulation of microparticles with living bacteria by PMMA retards bacteria escape upon contact to water for >20 d. The functionality of the PMMA shell is proven both by the release of fluorescein in buffer and an altered release time of bacteria in buffer solution. The escape of immobilized bacteria from hydrogel microparticles is prevented by water stable core-shell composites. Therefore, a surface initiated ATRP of MMA at room temperature is employed to obtain a hydrophobic PMMA shell. However, the viability of the immobilized bacteria is demonstrated afterwards. The core-shell architecture is examined by the copolymerization of FMA and MMA and by TEM.