Magnetically and biologically active bead-patterned hydrogels

We present a new approach to the direct patterning of biologically and magnetically active microbeads in nonbiofouling polymer scaffolds for use in microfluidic devices. Briefly, the process involves treatment of a glass substrate, conformal contact bonding of a PDMS microchannel on the substrate, filling of the channel with beads and prepolymer solution, and UV-initiated photopolymerization of a mask-defined pattern using a standard inverted microscope. This versatile and simple method allows for the rapid fabrication of dispersed or packed bead patterns in poly(ethylene glycol) (PEG) hydrogels that are covalently linked to glass surfaces. By exploiting the relative opacity of the microbeads used, we are able to create both partially exposed and fully encapsulated bead patterns. To demonstrate the utility of this new technology, we separated magnetic bead-bound B lymphocytes from T lymphocytes on a PEG-encapsulated magnetic filtration platform and also captured B cells directly on patterned, protein-decorated beads in a flow-through microfluidic device. Beyond cell sorting, the accurate patterning of industrially standardized, chemically diverse microbeads may have significant implications for microchip-based analyte detection.