Determination of the Catalytic Activity of a Peroxidase-like Nanozyme and Differences among Layered Double Hydroxides with Different Anions and Cations

Abstract

Nanomaterials with enzyme-like activity, namely, nanozymes, have been widely used as substitutes for natural enzymes, and they show excellent potential for application in many fields, such as biotechnology, environmental chemistry, and medicine. Layered double hydroxides (LDHs) are inorganic nanomaterials with adjustable compositions, simple preparation methods, and low costs and are some of the most promising candidate materials for the preparation of nanozymes. Here, we studied the syntheses and peroxidase-like activities of LDHs with four anions and four cations. First, LDHs prepared by the coprecipitation-hydrothermal method adopted hexagonal lamellar structures with good dispersion and uniform particle sizes. The Lambert-Beer law showed that the prepared LDHs exhibited good enzymatic activity. Later, the K_m and V_max values of the LDHs with different anionic/cationic materials intercalated into their structures were compared. Under the optimum conditions, the V_max of Mg₂Al-NO₃-LDH was 7.35 × 10^-2, which is 2-4 times higher than that of the LDHs containing other anions; the V_max values of NiFe-LDH and FeAl-LDH were 0.152 and 0.284, respectively, which are 10 times higher than those of the LDHs with other cations. Importantly, according to kinetic analyses of the enzymatic reactions, the effects of Fe²⁺ and Fe³⁺ on the LDH enzyme activity were greater than those of the intercalated anions. This study showed that NiFe-LDH and FeAl-LDH with high catalytic activities are candidate materials for peroxidase simulations, which may provide new strategies for the application of LDHs in biosensors, antioxidants, biotechnology, and other nanozyme applications.