Dual-Mechanism Driven Type-II FeS2/Co3S4 Heterointerface Nanozymes Overcoming Near-Physiological pH Constraints for Precision Xanthine Biosensing

The development of nanozymes exhibiting high peroxidase-like activity under near-physiological pH conditions remains a critical challenge for practical biosensing applications. In this study, a Type II FeS2/Co3S4 heterostructure nanozyme exhibiting superior peroxidase-mimetic activity under near-physiological conditions is demonstrated, effectively overcoming the pH limitations of conventional nanozymes. The enhanced catalytic performance stems from two synergistic mechanisms: electrostatic attraction between the negatively charged heterostructure surface (ζ = -7.2 mV at pH 7.0) and positively charged substrate TMB enhancing substrate preconcentration, coupled with accelerated electron transfer at the FeS2/Co3S4 heterointerface. Density functional theory (DFT) calculations indicate a reduced energy barrier (3.76 eV) for hydroxyl radical (•OH) generation and a stronger H2O2 adsorption energy (1.002 eV) compared to single-component systems. Cytotoxicity evaluation using human umbilical vein endothelial cells (HUVECs) demonstrates excellent biocompatibility. Based on these favorable characteristics, a dual range colorimetric biosensor for xanthine detection has been successfully developed, which exhibits a wide linear response in both low concentration range (0.2-7 μM) and high concentration range (7-100 μM), with a detection limit of 58 nM and high selectivity for interfering substances.