Study On The Catechol-titanium(?) Coordination Material And Their Applications For Enzyme Immobilization

Molecular hybrid materials, one or two components at molecular level, integrate the physical and chemical characters of both organic and inorganic materials. Benefiting form this advantage, molecular hybrid materials have become hot issue and research frontier in many areas including enzyme egineering. In this study, taking full advantage of the metal-organic coordination interaction, hibrid nanoparticles and microcapsules were synthesized at mild condition. These two kinds of carriors were used for enzyme immobilazition. The details of this study were summarized as follows:A facile approach is proposed to prepare dopamine/titania hybrid nanoparticles(DTHNPs), which are synthesized via directly blending titanium(?) bis(ammonium lactato) dihydroxide(Ti-BALDH) and dopamine aqueous solution. The amino group in dopamine is mainly in charge of inducing the hydrolysis and condensation of titanium precursor to form titania, and the catechol group in dopamine acts as an organic ligand to form titanium(?)-catecholate coordination. These DTHNPs were characterized by tranmission electron miscroscopy(TEM), scanning electron microscopy(SEM), X-ray diffraction(XRD), and X-ray photoelectron spectroscopy(XPS). The morphology of DTHNPs is changed from slightly cottonshaped aggregates to monodisperse nanoparticles with the increase of dopamine concentration. As a model enzyme, catalase(CAT) is entrapped in the DTHNPs during the nanoparticle preparation process. Surprisingly, the entrapment efficiency of CAT can be high up to nearly 100%, and no enzyme leakage could be detected. Moreover, immobilized CAT possesses 90% the catalytic activity of free enzyme.An ultrathin, hybrid microcapsule is prepared though coordination-enabled one-step assembly of tannic acid(TA) and titanium(?) bis(ammonium lactate) dihydroxide(Ti-BALDH) upon a hard-templating method. Briefly, the PSS-doped CaCO3 microspheres with a diameter of 5-8 ?m were synthesized and utilized as the sacrificial templates. Then, TA-Ti? coatings were formed on the surface of the PSS-doped CaCO3 templates through soaking in TA and Ti-BALDH aqueous solutions under mild conditions. After removing the template by EDTA treatment, the TA-Ti? microcapsules with a capsule wall thickness of 15±3 nm were obtained. The strong coordination bond between polyphenol and Ti? conferred the TA-Ti? microcapsules high structural stability in the range of p H values 3.0-11.0. Accordingly, the enzyme-immobilized TA-Ti? microcapsules exhibited superior pH and thermal stabilities. This study discloses the formation of TA-Ti? microcapsules that are suitable for use as supports in catalysis due to their extensive pH and thermal stabilities.