Dopamine-based molecularly imprinted polymers for the recognition of biomacromolecules

Abstract

Compared to natural antibodies or receptors, molecularly imprinted polymers (MIPs) have shown advantages of easy preparation, low cost, high stability and reusability. MIPs have been widely used in the fields of separation, chemical sensing, drug delivery and biocatalysis. The development of new imprinting methods such as surface imprinting, epitope imprinting, post-imprinting modification have promoted the synthesis and application of MIPs against biomacromolecules. Despite of the success, it remains a challenge to prepare MIPs with high affinity and specificity to the target proteins because the options of water-soluble monomers are very limited and the protein’s conformation is liable to change during the polymerization reaction. The majority of protein imprinting studies employ the five most common monomers: acrylamide (AAm), methacrylic acid (MAA), aminophenylboronic acid (APBA), acrylic acid (AA), and N-isopropylacrylamide (NiPAAm) and the two frequently used crosslinkers, methylenebisacrylamide (MBA) and ethylene glycol dimethacrylate (EGDMA) for preparation of protein imprinted polymers. In recent years, dopamine (DA) has been frequently used for surface modification as it can self-polymerize in alkaline medium at room temperature and generate polydopamine (pDA) films that can adhere onto almost all inorganic and organic surfaces with good biocompatibility. Thus, DA emerged as an appropriate monomer as well as a crosslinker for various imprinting reactions. In this review, we highlighted the recent advances in design and fabrication of DA-based MIPs for various biomacromolecules, including proteins, glycoproteins, bacteria or virus, with focus on protein imprinted polymers. First, we briefly introduced the DA self-polymerization reaction and the reported mechanisms for pDA formation. It is generally accepted that the initial driving force for the formation of pDA is the oxidation of DA to DA-indole by dissolved oxygen in an alkaline solution. Then, we summarized the recent work that employs common protein such as human/bovine serum albumin (HSA/BSA), lysozyme (Lyz), hemoglobin, trypsin and immunoglobulin (IgG) as the imprinting templates. These MIPs were mainly used for separation and purification of the template proteins. We also introduced the combination of protein imprinting with quartz crystal microbalance (QCM), cyclic voltammetry (CV), surface plasmon resonance (SPR) and mass spectroscopy (MS) for recognition and detection of the target proteins. In the following part, we summarized the strategies developed for imprinting of glycoproteins, most of which took advantage of boron affinity reaction or lectin-sugar interaction to improve the affinity and selectivity of the resultant MIPs. Then, we introduced recent work on imprinting of microorganisms such as viruses and bacteria, in which surface imprinting technique and potential analysis or chemiluminescence (ECL) technique are combined to construct biosensors that can selectively detect target species with high sensitivity. In addition, we also introduced the synthesis of a bio-inspired virus imprinted polymer and its application for prevention of viral infections. The techniques which were used for characterizing the properties of the MIP materials, e.g., adsorption capacity, imprinting factor and selectivity, as well as the proposed theoretical model were also mentioned in the review. Finally, we discussed current challenges and possible solutions for using DA as a monomer to prepare MIPs for biomacromolecules. We believe that the interactions between the intermediate products during dopamine polymerization and the template proteins deserve further investigation, as it may provide more possibilities to modulate the binding properties of the obtained MIPs.