Protein Crystallization and Biosensor Applications of Hydrogel-Based Molecularly Imprinted Polymers

We have characterized the imprinting capability of a family of acrylamide polymer-based molecularly imprinted polymers (MIPs) for bovine hemoglobin (BHb) and trypsin (Tryp) using spectrophotometric and quartz crystal microbalance (QCM) sensor techniques. Bulk gel characterization on acrylamide (AA), N-hydroxymethylacrylamide (NHMA), and N-isopropylacrylamide (NiPAM) gave varied selectivities when compared with nonimprinted polymers. We have also harnessed the ability of the MIPs to facilitate protein crystallization as a means of evaluating their selectivity for cognate and noncognate proteins. Crystallization trials indicated improved crystal formation in the order NiPAM < AA < NHMA. QCM studies of thin film MIPs confirm this trend with N-hydroxymethyl acrylamide MIPs exhibiting best discrimination between MIP and NIP and also cognate/noncognate protein loading. Equivalent results for acrylamide MIPs suggested that the cavities were equally selective for both proteins, while N-isopropylacrylamide MIPs were not selective for either cognate BHb or noncognate BSA. All BHb MIP-QCM sensors based on AA, NHMA, or NiPAM were essentially nonresponsive to smaller, proteins. Protein crystallization studies validated the hydrophilic efficacy of MIPS indicated in the QCM studies.