Siegert Electronic (Germany)

A generally applicable strategy to obtain mechanically robust hydrogels for the incorporation and containment of functional reporter bacteria for the microarray and microparticle-based detection and signaling of N-acyl homoserine lactone autoinducers (3OC12 HSL) at relevant concentrations is reported. For reinforcing hydrogels of 1,4-bi(phenylalanine-diglycol)-benzene (PDB), a hybrid hydrogel is formed by the combination of PDB self-assembly with Ca2+ mediated alginate crosslinking. The different assembly mechanisms are shown not to interfere with each other and despite the more than four-fold increased moduli of the hydrogels, diffusion of autoinducers into the gels remains efficient and Escherichia coli pLuxR-green fluorescent protein (GFP) reporter bacteria are proliferating. Templating affords reporter bacteria-loaded hydrogels with controllable shape and size. Upon exposure to 3OC12 HSL, the embedded bacteria exhibit an up to 12 ± 3 times increase in fluorescence intensity due to autoinducer-triggered GFP expression. This approach can serve as a potentially generally applicable strategy to sensitively detect bacteria via their secreted autoinducers.

Thecombination of supramolecular hydrogels formed by low molecularweight gelator self-assembly via noncovalent interactions within ascaffold derived from polyethylene glycol (PEG) affords an interestingapproach to immobilize fully functional, isolated reporter bacteriain novel microwell arrays. The PEG-based scaffold serves as a stabilizingelement and provides physical support for the self-assembly of theC2-phenyl-derived gelator on the micrometer scale. Supramolecularhydrogel microwell arrays with various shapes and sizes were usedto isolate single or small numbers of Escherichia coli TOP10 pTetR-LasR-pLuxR-GFP. In the presence of the autoinducer N-(3-oxododecanoyl) homoserine lactone, the entrapped E. coli in the hydrogel microwell arrays showed anincreased GFP expression. The shape and size of microwell arrays didnot influence the fluorescence intensity and the projected size ofthe bacteria markedly, while the population density of seeded bacteriaaffected the number of bacteria expressing GFP per well. The hydrogelmicrowell arrays can be further used to investigate quorum sensing,reflecting communication in inter- and intraspecies bacterial communitiesfor biology applications in the field of biosensors. In the future,these self-assembled hydrogel microwell arrays can also be used asa substrate to detect bacteria via secreted autoinducers.