Via zinc(II) protoporphyrin to the synthesis of poly(ZnPP-MAA-EGDMA) for the imprinting and selective binding of bilirubin

Poly(zinc protoporphyrin-methacrylic acid-ethyl glycol dimethylacrylate) (poly(ZnPP-MAA-EGDMA)) imprinted with α-bilirubin can cause spectroscopic change in wavelength and absorption intensity due to the metal–ion coordination between ZnPP and bilirubin. The fluorescent imprinted polymer was able to selectively bind α-bilirubin. The corresponding imprinted polymer monolith was synthesized by using the functional monomer, methacrylic acid and the fluorescent monomer, zinc(II) protoporphyrin. Although the imprinted polymers (MIPs) using methacrylic acid, protoporphyrin, or zinc(II) protoporphyrin alone as the only functional monomer could bind bilirubin, the imprinting effects were all comparably inferior to the imprinted poly(ZnPP-MAA-EGDMA). Therefore, it revealed that via the combined utilization of ZnPP and MAA for the fluorescent and functional effect, the MIPs thus prepared were then able to create the highly selective cavities. The optimal condition for the heated polymerization of the imprinted poly(ZnPP-MAA-EGDMA) was found to be 60 °C for 6 h. The imprinting factor of 3.069 could be achieved from the fluorescent imprinted polymer by comparing the binding results obtained from the MIP and the NIP (non-imprinted polymer). The imprinting factor obtained from bilirubin/biliverdin mixture solution was reduced to 2.111 because of the presence of biliverdin. The selectivity toward bilirubin of 2.269 from the bilirubin/biliverdin mixture was obtained. Therefore, to utilize ZnPP for the preparation of the imprinted materials confirmed the selective binding and detection of bilirubin via the fluorescent approach.