Chemical microsensor arrays using biorecognition molecules and cells in micropatterned hydrogels

In an effort to develop chemical sensor arrays to detect gaseous analytes, we present a new approach for the microfabrication of biosensor arrays based upon poly(ethylene glycol) diacrylate (PEG-DA) hydrogels patterned photolithographically on inorganic and plastic substrates. Individual microstructures of dimensions 5 to 600 micrometers with aspect ratios as high as 1.4 were created. In the former case as many as 400 elements were generated in a 1 mm square pattern. The resultant hydrogel patterns were hydrated for as long as three weeks without considerable delamination or deformation of the elements. The chemistry of these hydrogels allowed us to immobilized biomolecules with little loss of activity and permitted the control of mass transfer into the gels by changing the mesh size of the polymer network. Fluorophore labeled biorecognition molecules were encapsulated in these microstructures and detection of various analytes achieved by measuring, using a CCD camera, changes in fluorescence that occurred when analytes partition into the gels and bind to the recognition molecules. These microstructures were also used to encapsulate living cells and were integrated with microfluidic devices to create cell-based sensing devices.