Construction Of Biomimetic Enzyme Based On Porphyrins And Their Application In Biosensing And Pollutants Removal

As one kind of porphyrin compounds, hemin is the active center of horse radish peroxidase. Hematin is the hydroxylated form of hemin. The two possess activity like that of naturally occurring enzymes. However, hematin and hemin still suffer from the limitations of lower activity compared to natural enzymes, which results from the lack of a suitable environment for the biomimetic catalysis. Hence, purpose of this study is to prepare hematin or hemin-based artificial enzymes with high activity through connecting hematin or hemin by chemical modification. The artificial enzymes not only can realize the detection of trace hydrogen peroxide and catechol, but also have special removal properties for pollutants.The first kind of bionic enzymatic preparation was based on hematin, which adopted a novel nano-composite of conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and 1-pyrenebutanoic acid (PBA) through π-π stacking, as well as hematin association with PBA through coordinate bonds of Zr4+ and carboxylic acid group. The new-fashioned biosensor is easy to prepare, and the PEDOT film enhanced the electron transfer process of hematin. The stability and high sensitivity of the material is established by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and current-time (I-T).The second kind of bionic enzymatic preparation was based on hemin. PEI-coated gold nanoparticles (PEI-AuNPs) were synthesized using PEI as a reducing agent and stabilizer simultaneously. Many amino-groups of PEI could form amido bond with hemin, so that hemin was connected with PEI-AuNPs, and thus nanoparticles decorated with hemin were obtained (PEI-AuNPs-Hemin). AuNPs has property of biocompatibility and good electronic conductivity, which can enhance the catalytic efficiency of PEI-AuNPs-Hemin. The as-prepared nanocomposite exhibited intrinsic peroxidase-like catalytic activities and strong adsorption properties toward methyl orange (MO). PEI-AuNPs-Hemin biosensor presented a good performance for H2O2, with a detection limit of 0.245 nmol·L-1 and a high sensitivity of 0.347 mA·mM-1·cm-2. The unique characteristics of the PEI-AuNPs-Hemin nanomaterial displayed high efficiency as a pollutant absorbent and depicted promising applications for the fabrication of high-performance bio-electronic devices in the future.