Imobilização da enzima glicose-oxidase em nanopartículas de ferrita de cobalto.

Abstract

The immobilization of enzymes has been presented as a promising strategy in processes aimed at separation, recovery and reuse of these biomolecules. Due to the need to develop materials compatible with these characteristics, this work aims to synthesize and functionalize magnetic nanoparticles (MNPs) of the type cobalt ferrite (CoFe2O4), and to use them in the immobilization of the glucose oxidase enzyme (GOD), to be applied as biosensors. The MNPs were prepared by combustion reaction using iron and cobalt metal nitrates as precursors and urea as fuel, silanized by the stöber method with the organosilane tetraethylorthosilicate (TEOS), and functionalized with 3-aminopropyltriethoxysilane (APTES); the CoFe2O4 and CoFe2O4@SiO2NH2 MNPs were characterized by X-ray diffraction (XRD), granulometric distribution (Horiba), scanning electron microscopy (SEM), physical nitrogen adsorption (BET method), Fourier transform infrared spectroscopy (FTIR), thermogravimetric measurements (TG/DTG) and magnetization measurements (ZFC/FC). The results showed reproducibility of the synthesis by combustion reactions, CoFe2O4 manometric particles between 21nm and 25nm, crystallinity around 60%, composition of 83.95% of cobalt ferrite and 16.05% of hematite, surface area of 16.64m2/g, zeta potential of -49.2mV, loss of 2.52% in mass after thermogravimetric analysis, and characteristic magnetization of hard type materials; after coating with TEOS and APTES, the MNPs showed 3.7% increase in particle size, 21.7% surface area reduction, zeta potential of -0.2mV, mass loss of 12.55%, and remaining magnetization (31.9%) and coercivity (12.8%), maintaining a good magnetic response. By the immobilization results of the GOD, it was verified that the activation with a concentration of 2% of glutaraldehyde, presented better adsorptive capacity result of GOD in the NPMs (0.048 mgAdsb/mgAdsv). The proposed pseudo-first order model predicted the immobilization behavior satisfactorily to low concentrations; by the adsorption isotherm, it was found that the initial GOD concentration of 1mg / mL provided the highest adsorbed enzymatic load per gram of NPMs (0.048 mgAdsb/mgAdsv); the GOD immobilized in the CoFe2O4@SiO2NH2 NPMs showed enzymatic activity of 34.3U/g, and after 5 cycles of reuse, the activity decreased to 1/3 of the initial, remaining constant after 2 consecutive cycles.