Defining the interactions between proteins and surfactants for nanoparticle surface imprinting through miniemulsion polymerization

Molecular imprinting has been considered one of the most promising techniques for the preparation of synthetic receptors. In spite of the ease of the conventional imprinting methodology and its associated success with the imprinting of small molecules, the approach has its limititation for the-imprinting of protein macromolecules. This is primarily due to the limited diffusion associated with the bulkiness of the template macromolecules and the incompatibility between the fragile protein template and the imprinting conditions. To resolve these issues for the successful imprinting of proteins, miniemulsion polymerization has been employed for preparing protein surface-imprinted nanoparticles. Ribonuclease A (RNase A), bovine serum albumin (BSA), and lysozyme (Lys) were used as the template proteins while methylmethacrylate and ethylene glycol dimethacrylate were the functional and cross-linking monomers, respectively, to produce particles with sizes of about 40 nm. The RNase A surface-imprinted nanoparlicles displayed favorable molecular selectivity and rebinding kinetics even in an aqueous medium. However, such a molecular recognition property was not observed for the BSA- and Lys-imprinted nanoparticles. By studying the template protein - surfactant interaction using circular dichroism, it was found that a certain degree of interaction between the template protein and the micelles is required to maintain the proteins at the particle surface. It was also found that such an interaction should not be too extensive to cause a significant conformational change, or denaturation, in the proteins to ensure the recognition of proteins in their native states. This study therefore defines the important parameters required for the successful application of a simple miniemulsion polymerization strategy for protein-surface imprinting.