In Situ Enzyme Encapsulation in Conductive Layered Double Hydroxides with Enhanced Activity and Stability for a Portable Electrochemical Sensor.

Enzyme immobilization represents a critical approach to address enzyme instability and limited recyclability in practical biocatalytic systems. However, simultaneously improving enzyme stability and catalytic activity remains a major bottleneck, restricting the broader implementation of immobilized enzymes. Herein, we report a mild in situ encapsulation strategy using layered double hydroxides (LDHs) as a structurally tailored host matrix for enzyme confinement. Benefiting from the hydrophilic and layered structure of MgAl-LDH, the HRP@MgAl-LDH composite preserved the native conformation of encapsulated HRP while delivering exceptional structural stability. The MgAl-LDH not only created a biocompatible microenvironment that sustained high enzymatic activity but also acted as a protective scaffold to enhance stability and reusability. Electrochemical characterization revealed that HRP@MgAl-LDH promoted rapid and efficient electron transfer between the enzyme active sites and the electrode surface, enabling faster reaction kinetics relative to free HRP and conventionally immobilized enzyme systems. Leveraging these favorable structural and electrochemical properties, we fabricated a portable electrochemical sensor for the sensitive detection of H2O2 in human urine. The sensor exhibited a wide linear detection range (50 pM-250 μM) and a low detection limit of 36.96 pM, along with rapid response, strong anti-interference performance, portability, and low cost. This LDH-based in situ encapsulation strategy effectively balanced the often-competing demands of high enzymatic activity and long-term stability, overcoming key limitations of traditional encapsulation methods. This work offered a promising high conductive material-based strategy for the development of practical point-of-care devices for H2O2 detection in complex biological samples.