Peng Zhang

Heterojunction nanozymes offer unique advantages, including interface charge regulation, multivalent-state cycling, defect engineering, and enhanced field responses. These merits overcome the bottlenecks of single-component nanozymes, such as low catalytic activity, poor stability, and limited functionality. They have shown great potential for applications in biomedical, environmental governance, and food detection fields. This article provides a systematic review of the latest research progress on heterojunction nanozymes. First, heterojunction nanozymes are classified by their diverse enzyme−mimetic activities (e.g., oxidase (OXD), catalase (CAT), peroxidase (POD)), followed by a systematic overview of their material components, key active centers, and representative synthetic strategies. We next discuss the charge-separation and directional-transfer mechanisms of type I, II, S, Z, and Schottky heterojunctions, and reveal how multivalent-state cycling, interface defects, external-field responses, and microenvironment activation regulate catalytic performance. Finally, we summarize their applications in biosensing, disease treatment, antibacterial therapy, pollutant degradation and detection, and food-contaminant analysis. We also discuss the remaining challenges and future directions, including interface precision design, mechanism elucidation, biosafety, and large-scale production. This article aims to provide comprehensive reference for the rational design and application expansion of high-performance multifunctional heterojunction nanozymes.

Metal−organic framework (MOF)-based nanozymes have emerged as promising alternatives to natural enzymes for catalytic sensing due to their tunable porous architectures and abundant active sites. Nevertheless, the practical implementation of pristine Co-MOF nanozymes is severely hindered by intrinsic catalytic activity attenuation, poor structural stability, and unavoidable aggregation issues. In this work, a triple synergistic interface engineering strategy is proposed to fabricate high-performance and recyclable composite nanozymes via Prussian blue (PB) modification, polyvinyl alcohol (PVA) aerogel immobilization, and DNAzyme functionalization. The introduction of PB with self-amplifying catalytic behavior effectively optimizes the redox reaction kinetics of the Co-MOF, significantly boosting its peroxidase-like catalytic activity and structural durability. The three-dimensional porous PVA aerogel serves as a versatile supporting matrix, which not only uniformly disperses PB-modified Co-MOF nanocomposites to eliminate particle aggregation and catalyst waste but also endows the composite with excellent recoverability and cyclic usability. Furthermore, the integration of the hemin/G-quadruplex DNAzyme constructs a multilevel catalytic interface, which synergistically enhances the catalytic efficiency and environmental adaptability of the aerogel-based nanozyme system. Benefiting from the structural superiority and multi-component synergistic catalysis, the optimized DNAzyme@PB/Co-MOF PVA aerogel sensing platform achieves sensitive, stable, and visual detection of the total antioxidant capacity. This work systematically explores the mechanisms of multi-scale composite nanozymes, providing a feasible and universal strategy for the rational design and fabrication of high-stability, high-efficiency, and recyclable MOF-based functional catalytic materials for advanced sensing applications.

Thermally responsive structural transitions in flexible metal–organic frameworks (FMOFs) play a vital role in gas separation, energy storage, and sensing. Unlike pressure or guest adsorption, temperature governs phase stability by modulating the balance between enthalpic and entropic contributions. This review establishes a unified free-energy landscape (FEL) framework to rationalize thermally induced breathing across diverse FMOF systems. Key structural degrees of freedom, including ligand conformational flexibility, metal–ligand (M-L) bond dynamics, and framework topology, are evaluated for their roles in shaping the FEL. A thermodynamic phase diagram with enthalpy change (ΔH) and entropy change (ΔS) as axes partitions FMOFs into four characteristic regimes: closed-pore dominant, open-pore dominant, bistable, and hysteresis-governed. The topology of the FEL—encompassing the depth and connectivity of its minima and the kinetic barriers (ΔG‡) between them—determines whether breathing is abrupt, continuous, or stepwise. Regulation strategies including ligand functionalization, metal substitution, defect engineering, and nanoconfinement are interpreted as systematic movements on the ΔH-ΔS diagram. This review provides a mechanistic foundation and a predictive roadmap for designing thermally responsive FMOFs with tailored transition temperatures, hysteresis width, and breathing amplitude.

Cell‐ and microorganisms‐based therapeutics are promising strategies for treating various diseases, yet their clinical translation faces some obstacles such as poor patient compliance and instability. Microneedles (MNs) have gained much attention due to their characteristics of minimally invasive nature, high efficiency, and good compliance. However, traditional MNs face limitations in delivering living cells and microorganisms. Ice MNs, fabricated under low‐temperature conditions, represent innovative delivery platforms that helps maintain the activity of cells and microorganisms. This review aimed to explore recent progress in delivering living cells and microorganisms using ice MNs. In this review, the preparation methods, materials, and advantages of ice MNs are first summarized. Then, the application of conventional MNs and ice MNs in the field of biomedicine is reviewed. In this section, the application of conventional MNs in the delivery of living microorganisms and cells is first described. We further discuss the application of ice MNs in tumors, inflammatory diseases, bacterial infections, vaccine delivery, and hair regeneration in detail. Finally, the challenges and prospects of ice MNs are outlined. It is expected that the integration of ice MNs with living cells and microorganisms holds great promise for significant breakthroughs in future clinical applications.

Microneedles (MNs) have attracted considerable attention as an innovative physical enhancement technology for transdermal drug delivery. In recent years, the incorporation of functional materials such as metals, carbon‐based materials, and intrinsically conductive polymers (ICPs) has endowed MNs with excellent electrical properties. This advancement marks a significant functional evolution, transforming MNs from passive drug carriers into actively controllable and multifunctional biomedical platforms. The primary advantage of conductive MNs lies in their capacity to penetrate the stratum corneum and establish a high‐quality electrical interface directly with subcutaneous tissues. This capability not only enhances the signal‐to‐noise ratio of bioelectrical signal acquisition, thereby improving signal fidelity in applications such as physiological monitoring and neural repair, but also enables actively controlled drug release. This review systematically summarizes key research progress in conductive MNs, with emphasis on the types of conductive materials employed and their respective advantages and limitations, strategies for imparting conductivity, corresponding microfabrication techniques, and cutting‐edge applications in drug delivery, electrophysiological monitoring, and electrical stimulation therapy. Finally, the challenges associated with clinical translation and future development prospects are discussed, aiming to provide valuable insights for the design and development of novel conductive MNs systems.