Effect of magnetite-cellulose material performance as immobilization support of Streptomyces sp. cholesterol oxidase on the enzyme storage time and usage repeatability for biosensor application

The latest development of cholesterol level detectors is currently leading to biosensing technology using the cholesterol oxidase (CHOx) enzyme. To optimize the performance of enzymes and obtain high specificity, immobilization techniques with material support are required. Cellulose is one of the most versatile biopolymers abundantly available in nature with attractive traits for biomedical purposes. The cellulose is combined with magnetite material, which is an inorganic metal oxide with high paramagnetic properties. The work was aimed to study the application of the magnetite-cellulose hybrid as a supporting material for immobilization of the CHOx. Magnetite was synthesized and combined with hydrolyzed cellulose, and CHOx was immobilized to the material by physical adsorption. The immobilized enzyme was evident by the appearance of the N-H functional group at a wavelength of 1634.34 cm−1 and a C-O-C bond at a wavenumber of 1057.67 cm−1, with an SEM image indicating a rougher and denser surface without any hollow gaps compared to unused material. The activity assay results revealed that the storage stability of CHOx was enhanced after immobilization, the immobilized enzyme retained ∼10% of the residual activity after 4 cycles of use, and the optimal concentration of CHOx used during immobilization were 2 mg/10mL.