A Closer Look at the Impact of Molecular Imprinting on Adsorption Capacity and Selectivity for Protein Templates

Molecularly imprinted polymers (MIPs) are often investigated as lower cost, more environmentally robust alternatives to natural recognitive biomolecules, such as antibodies. When synthesized on the surface of nanomaterial supports, MIPs are capable of quick and effective binding of macromolecular templates when compared to traditional bulk-imprinted polymers. We have developed a method for imprinting proteins on biodegradable nanoparticle supports and have used these materials to investigate the impact of molecular imprinting on adsorption capacity and selectivity for lysozyme, the template protein. The imprinting process increased the adsorption capacity of the polymer for the template, lysozyme, with the MIPs being able to bind up to 83.5% of their dry weight as compared to 55.7% for nonimprinted polymers (NIPs). In noncompetitive binding experiments, where proteins were independently incubated with MIPs, the difference between adsorption capacity for lysozyme and proteins with much lower isoelectric points (pI < 8.0) was statistically significant. However, there was no statistical difference between adsorption capacity for lysozyme and other high-isoelectric point proteins, suggesting that MIPs are semiselective for this class of proteins. In competitive binding experiments, both MIPs and NIPs preferentially bound lysozyme over other high-isoelectric point proteins. This result demonstrated that imprinting alone could not account for the observed selectivity for lysozyme. Analysis of the solvent accessible surface area of lysozyme and its high-isoelectric point competitors revealed why lysozyme is an exceptional binder to the polymer system used in this work, with or without imprinting.