The fabrication of 3D hydrogel microarrays for DNA analytics that allow simple visual signal readout for on-site applications is described. A convenient one-step polymerization of the hydrogel including in situ capture oligonucleotide immobilization is accomplished by using N,N'-dimethylacrylamide/polyethylene glycol (PEG1900 )-bisacrylamide monomers. The implementation of an acylphosphine-oxide photoinitiator even allows polymerization at daylight, whereas other approaches require exposure with light in the UV-range. This minimizes the risk of UV-caused DNA damages within the capture DNA-strand that could adversely affect the subsequent hybridization step. The porous network of these gel segments allows DNA as well as protein penetration. Thus, the successful in-gel DNA hybridization is monitored by the deposition of silver nanoparticles. These metal particles allow naked eye signal readout.

A timesaving and convenient method for bacterial detection based on one-step, one-tube deoxyribonucleic acid (DNA) hybridization on hydrogel array while target gene amplification is described. The hydrogel array is generated by a fast one-pot synthesis, where N,N'-dimethylacrylamide/polyethyleneglycol(PEG1900 )-bisacrylamide mixture polymerizes via radical photoinitiation by visible light within 20 min concomitant with in situ capture probe immobilization. These DNA-functionalized hydrogel droplets arrayed on a planar glass surface are placed in the polymerase chain reaction (PCR) mixture during the thermal amplification cycles. The bacterial cells can be implemented in a direct PCR reaction, omitting the need for prior template DNA extraction. The resulting fluorescence signal is immediately detectable after the end of the PCR (1 h) following one short washing step by microscopy. Therefore a valid signal can be reached within 1.5 h including 10 min for pipetting and placement of the tubes and chips. The performance of this novel hydrogel DNA array was successfully proven with varying cell numbers down to a limit of 10(1) Escherichia coli cells.