Three-Step Depletion Strategy of Glutathione: Tunable Metal-Organic-Framework-Engineered Nanozymes for Driving Oxidative/Nitrative Stress to Maximize Ferroptosis Therapy.

Ferroptosis is a novel type of nonapoptotic programmed cell death involving the accumulation of lipid peroxidation (LPO) to a lethal threshold. Herein, we propose tunable zeolitic imidazolate framework (ZIFs)-engineered biodegradable nanozymes for ferroptosis mediated by both reactive oxygen species (ROS) and nitrogen species (RNS). l-Arginine is utilized as an exogenous nitric oxide donor and loaded into hollow ZIFs@MnO2 artificial nanozymes, which are formed by etching ZIFs with potassium permanganate and simultaneously generating a MnO2 shell in situ. The constructed nanozymes with multienzyme-like activities including peroxidase, oxidase, and catalase can release satisfactory ROS and RNS through a cascade reaction, consequently promoting the accumulation of LPO. Furthermore, it can improve the efficiency of ferroptosis through a three-step strategy of glutathione (GSH) depletion; that is, the outer MnO2 layer consumes GSH under slightly acidic conditions and RNS downregulates SLC7A11 and glutathione reductase, thus directly inhibiting GSH biosynthesis and indirectly preventing GSH regeneration.

Designed Synthesis of Compartmented Bienzyme Biocatalysts Based on Core-Shell Zeolitic Imidazole Framework Nanostructures.

For complex cascade biocatalysis, multienzyme compartmentalization helps to optimize substrate transport channels and promote the orderly and tunable progress of step reactions. Herein, a simple and general synthesis strategy is proposed for the construction of a multienzyme biocatalyst by compartmentalizing glucose oxidase and horseradish peroxidase (GOx and HRP) within core-shell zeolite imidazole frameworks (ZIF)-8@ZIF-8 nanostructures. Owing to the combined effects of biomimetic mineralization and the fine regulation of the ZIF-8 growth process, the uniform shell encloses the seed (core) surface by epitaxial growth, and the bienzyme system is accurately localized in a controlled manner. The versatility of this strategy is also reflected in ZIF-67. Meanwhile, with the ability to covalently bind divalent metal ions, lithocholic acid (LCA) is used as a competitive ligand to improve the pore structure of the ZIF from a single micropore to a hierarchical micro/mesopore network, which greatly increases mass transfer efficiency. Furthermore, the multienzyme cascade reaction is exemplified by the oxidation of o-phenylenediamine (OPD). The findings show that the bienzyme assembly strategy significantly affects the biocatalytic efficiency mainly by influencing the utilization efficiency of the intermediate (Hydrogen peroxide, H2 O2 ) between the step reactions. This study sheds new light on facile synthetic routes to constructing in vitro multienzyme biocatalysts.

Anti-inflammatory and anti-biotic drug metronidazole loaded ZIF-90 nanoparticles as a pH responsive drug delivery system for improved pediatric sepsis management.

Sepsis is a life-threatening disease caused by the dis-functioning of the immune response to pathogenic infections. Despite, the discovery of modern therapeutics and treatments of sepsis are lacking due to the resistance of pathogens. Metronidazole is an antibiotic commonly used to treat bacterial infections, but usage is limited and challenging by a short half-life period. In this research work, fabricate a pH-responsive drug delivery system for controlled release of metronidazole targeted molecules. We exemplified that, the encapsulation of hydrophilic metronidazole drug within a hydrophobic ZIF-90 framework can be enhanced the pH-responsive drug release under acidic conditions. The ZIF-90 frameworks only decompose in under acidic solutions, they are highly stable in physiological conditions. The pH-responsive protonation mechanism of ZIF-90 frameworks promotes the quick release of metronidazole within cells. The antimicrobial proficiency of zinc and metronidazole will expose a synergistic effect in ROS-mediated bacterial inhibition and auto-immunity boosting of normal cells. In vitro, antibacterial activity results revealed that the MI@ZIF-90 nano drug delivery system effectively eradicated human infectious pathogens at the lowest concentrations. In anti-fungal activity, studies show excellent growth inhibition against human pathogenic fungi Aspergillus fumigatus and Candida albicans. Finally, the PBMC cytocompatibility study concludes, that the fabricated MI@ZIF-90 drug delivery system is non-toxic to biomedical applications. The overall research findings highlight the design of a smart drug delivery system for sepsis treatment. In future it will be an efficient, low-cost, and biocompatible pharmaceutics for pediatric sepsis management processes.

Recent Progress on the Synthesis and Modified Strategies of Zeolitic-Imidazole Framework-67 Towards Electrocatalytic Oxygen Evolution Reaction.

As a class of metal-organic framework, the zeolitic-imidazole framework-67 is constructed from bridging cobalt ions and 2-methylimidazole. The high content of abundant active cobalt species, uniform structure, ultrahigh porosity, and large surface area show the potential for multiple catalytic applications, especially electrocatalytic oxygen evolution reaction (OER). The design and synthetic strategies of catalyst-based ZIF-67 that approach the maximized catalytic performance are still challenging in further development. Herein, the current progress strategy on the structural design, synthetic route, and functionalization of electrocatalysts based on ZIF-67 to boost the catalytic performance of OER is reviewed. Besides, the structurally designed catalyst from various fabricated strategies corresponding to enhancing catalytic activity is discussed. The emphasized review for understanding design and synthetic structure with catalytic performance could guide researchers in further developing catalyst-based ZIF-67 for improving the efficient electrocatalytic OER.

A ratiometric fluorescent sensor for the detection of phosphate.

Over the past few years, ratiometric fluorescent nanoprobes have garnered substantial interest because of their self-calibration characteristics. This research developed a ratiometric fluorescent sensor to detect phosphate. Through encapsulating luminescent materials, gold nanoclusters (AuNCs) and carbon dots (CDs) into a zeolitic imidazolate framework-8 (ZIF-8), the fluorescence signal of AuNCs was enhanced, while that of CDs was suppressed. After phosphate was added, it could decompose ZIF-8, and AuNCs and CDs were released, which weakened the fluorescence signal of the AuNCs while restoring that of the CDs. Thereby, this makes CDs/AuNCs@ZIF-8 a potential fluorescent sensor for phosphate determination. The ratiometric sensor had facile synthesis, good selectivity, and a low detection limit. Therefore, this sensor was an effective tool for the detection of phosphate.

Facile synthesis of Cu/Co-ZIF nanoarrays for non-enzymatic glucose detection.

Cu/Co-ZIF nanoflake arrays on carbon cloth are fabricated by controlling the introducing of Cu2+ions during the growth of Co-ZIF. The Cu/Co-ZIF-20 electrode prepared with 20 mM Cu2+possesses large electrochemically active surface area and bimetallic active sites, which can be revealed by cyclic voltammetry tests. The amperometrici-tmeasurements demonstrate that the Cu/Co-ZIF-20 electrode displays a wide linear range from 0.05 mM to 6.0 mM, and a high sensitivity of 1.03 mA mM-1cm-2. Good selectivity, repeatability and practical applicability indicate its promising application in enzyme-free glucose sensing.

ZIF-Based Nanoparticles Combine X-Ray-Induced Nitrosative Stress with Autophagy Management for Hypoxic Prostate Cancer Therapy.

Although reactive oxygen species (ROS)-mediated tumor treatments are predominant in clinical applications, ROS-induced protective autophagy promotes cell survival, especially in hypoxic tumors. Herein, X-ray triggered nitrite (NO2- ) is used for hypoxic prostate cancer therapy by inhibiting autophagy and inducing nitrosative stress based on an electrophilic zeolitic imidazole framework (ZIF-82-PVP). After internalization of pH-responsive ZIF-82-PVP nanoparticles, electrophilic ligands and Zn2+ are delivered into cancer cells. Electrophilic ligands can not only consume GSH under hypoxia but also capture low-energy electrons derived from X-rays to generate NO2- , which inhibits autophagy and further elevates lethal nitrosative stress levels. In addition, dissociated Zn2+ specifically limits the migration and invasion of prostate cancer cells through ion interference. In vitro and in vivo results indicate that ZIF-82-PVP nanoparticles under X-ray irradiation can effectively promote the apoptosis of hypoxic prostate cancer cells. Overall, this nitrosative stress-mediated tumor therapy strategy provides a novel approach targeting hypoxic tumors.

Atomically Dispersed Single Co Sites in Zeolitic Imidazole Frameworks Promoting High-Efficiency Visible-Light-Driven Hydrogen Production.

As photocatalysis technology could transform renewable and clean solar energy into green hydrogen (H2 ) energy through solar water splitting, it is regarded as the "Holy Grail" in chemistry field in the 21st century. Unfortunately, the bottleneck of this technique still lies in the exploration of highly active, cost-effective, and robust photocatalysts. This work reports the design and synthesis of a novel zeolitic imidazole framework (ZIF) coupled Zn0.8 Cd0.2 S hetero-structured photocatalyst for high-performance visible-light-induced H2 production. State-of-the-art characterizations and theoretical computations disclose that the interfacial electronic interaction between ZIF and Zn0.8 Cd0.2 S, the high distribution of Zn0.8 Cd0.2 S on ZIF, and the atomically dispersed coordinately unsaturated Co sites in ZIF synergistically arouse the significantly improved visible-light photocatalytic H2 production performance.

ZIF-8 Degrades in Cell Media, Serum, and Some-But Not All-Common Laboratory Buffers.

The emergence of drug delivery using water stable metal-organic frameworks has elicited a lot of interest in their biocompatibility. However, few studies have been conducted on their stability in common buffers, cell media, and blood proteins. For these studies, single crystal ZIF-8 approximately 1 um in diameter were synthesized, incubated with common laboratory buffers, cell media, and serum, and then characterized by PXRD, IR, DLS, and SEM. Time-resolved SEM and PXRD demonstrate that buffers containing phosphate and bicarbonate alter the appearance and composition of ZIF-8; however, cargo inside the ZIF-8 does not appear to leak out, in most of these buffers, even when the ZIF-8 itself is displaced by phosphates. On the other hand, blood proteins in serum dissolve ZIF-8, causing trapped biomolecules to escape. The study presented here suggests that ZIF-8 can undergo dramatic surface chemistry changes that may affect the interpretation of cellular uptake and cargo release data. On the other hand, it provides a rational explanation as to how ZIF-8 neatly dissolves in vivo.

Self-assembled magnetic nanoparticle supported zeolitic imidazolate framework-8: An efficient adsorbent for the enrichment of triazine herbicides from fruit, vegetables, and water.

Zeolitic imidazolate frameworks have positive surface charges and high adsorption capabilities. In this work, zeolitic imidazolate frameworks-8 and negatively charged magnetic nanoparticles were self-assembled by electrostatic attraction under sonication. The extraction performance of the synthesized hybrid material was evaluated by using it as a magnetic adsorbent for the enrichment of triazine herbicides in various sample matrices prior to analysis using ultrafast liquid chromatography. The main parameters, that is, extraction time, adsorbent dosage, salt concentration, and desorption conditions, were evaluated. Under the optimum conditions, good linear responses from 2.5 to 200 ng/mL for atrazine (simazine) and 1 to 200 ng/mL for prometryn (ametryn), with correlation coefficients (R2 ) higher than 0.9992 were obtained. The detection limits of the method (S/N = 3) were 0.18-0.72 ng/mL. The proposed method was successfully used to determine triazine herbicides in six samples, namely, apple, pear, strawberry, pakchoi, lettuce, and water. The amounts of simazine in all the fruit and vegetable samples were 10.8-25.2 ng/mL. The recoveries of all the analytes were 88.0-101.9%, with relative standard deviations of less than 8.8%.

Enhancing Hydrogen Sulfide Detection at Room Temperature Using ZIF-67-Chitosan Membrane.

Developing new materials for energy and environment-related applications is a critical research field. In this context, organic and metal-organic framework (MOF) materials are a promising solution for sensing hazardous gases and saving energy. Herein, a flexible membrane of the zeolitic imidazole framework (ZIF-67) mixed with a conductivity-controlled chitosan polymer was fabricated for detecting hydrogen sulfide (H2S) gas at room temperature (RT). The developed sensing device remarkably enhances the detection signal of 15 ppm of H2S gas at RT (23 °C). The response recorded is significantly higher than previously reported values. The optimization of the membrane doping percentage achieved exemplary results with respect to long-term stability, repeatability, and selectivity of the target gas among an array of several gases. The fabricated gas sensor has a fast response and a recovery time of 39 s and 142 s, respectively, for 15 ppm of H2S gas at RT. While the developed sensing device operates at RT and uses low bias voltage (0.5 V), the requirement for an additional heating element has been eliminated and the necessity for external energy is minimized. These novel features of the developed sensing device could be utilized for the real-time detection of harmful gases for a healthy and clean environment.

Self-templated pseudomorphic transformation of ZIF into layered double hydroxides for improved supercapacitive performance.

Zeolitic imidazole frameworks (ZIFs) have been researched as excellent templates for synthesizing functional materials to be used in various fields. However, direct adoption of ZIFs as electrode material shows dissatisfactory electrochemical performance due to their limited exposed electroactive sites, poor chemical stability and sluggish charging dynamics. Herein, we demonstrate in situ transformation of ZnCo-ZIF frameworks decorated on ZnCo nanorod array (ZnCo-NA) into three-dimensional (3D) spatially distributed ZnCo-LDH/ZnCo-NA heterostructure. Owing to this unique structure that can provide abundant electroactive sites and ion transport paths in all directions, the resulting ZnCo-LDH/ZnCo-NA electrode exhibits an improved supercapacitive performance with a high capacity of 15.76 F cm-2 (1576 F g-1, 788 C g-1) at 20 mA cm-2 (2 A g-1), and maintains the capacity of 13.855 F cm-2 (1385.5 F g-1, 692.75 C g-1) at 150 mA cm-2 (15 A g-1), showing a high rate capability of 87.9%. A coin cell asymmetric supercapacitor (aSC) is assembled by employing ZnCo-LDH/ZnCo-NA as cathode and active carbon as anode, which exhibits an energy density of 21.3 Wh kg-1 and superb cycling performance with capacitance retention of 88.1% after 5000 cycles. More importantly, such a simple in-situ pseudomorphic transformation of ZIF templates into novel class LDH materials demonstrates a new generation of bimetallic heterostructure for applications in energy-related fields and beyond.

Facile Fabrication of Methyl Gallate Encapsulated Folate ZIF-L Nanoframeworks as a pH Responsive Drug Delivery System for Anti-Biofilm and Anticancer Therapy.

Zeolitic imidazole frameworks are emerging materials and have been considered an efficient platform for biomedical applications. The present study highlights the simple fabrication of methyl gallate encapsulated folate-ZIF-L nanoframeworks (MG@Folate ZIF-L) by a simple synthesis. The nanoframeworks were characterized by different sophisticated instruments. In addition, the drug-releasing mechanism was evidenced by in vitro releasing kinetics at various pH conditions. The anti-biofilm potential confirmed by the biofilm architectural deformations against human infectious pathogens MRSA and N7 clinical strains. Furthermore, anticancer efficacy assessed against A549 lung cancer cells. The result reveals that the MG@Folate ZIF-L exposed a superior cytotoxic effect due to the pH-responsive and receptor-based drug-releasing mechanism. Based on the unique physicochemical and biological characteristics of nanoframeworks, it has overcome the problems of undesired side effects and uncontrolled drug release of existing drug delivery systems. Finally, the in vitro toxicity effect of MG@Folate ZIF-L was tested against the Artemia salina (A. salina) model organism, and the results show enhanced biocompatibility. Overall, the study suggested that the novel MG@Folate ZIF-L nanoframeworks is a suitable material for biomedical applications. It will be very helpful to the future design for targeted drug delivery systems.

Enhanced DNA nuclease activity of Momordica charantia lectin by biomimetic mineralization as hybrid copper phosphate nanoflowers and as zeolitic imidazole frameworks.

Biomimetic mineralization of enzymes for enhanced stability and activity is an important area of research due to its potential applications. Inorganic materials with enzymes coated and or embedded in them, viz., protein-inorganic hybrid nanomaterials with distinctive morphology and surface characteristics are promising candidates for exploring their elevated enzymatic activity. In this work, we have developed two different types of protein inorganic nanohybrid materials using a 120 kDa lectin purified from bitter gourd seeds (Momordica charantia lectin, MCL), and (i) copper phosphate nanoflowers to result in a protein - inorganic nano hybrid material CuPNF_MCL and (ii) encapsulating the protein in zeolitic imidazole framework, ZIF8_MCL. While CuPNF_MCL showed floral morphology, the ZIF8_MCL mostly showed hexapod morphology as noticed from the microscopy data. Both the nanomaterials showed a distinctive trend of decrease in size with increase in the protein concentration used during the preparation. The nanoflowers also showed an increase in the tightness of the packing of petals with increase in the protein concentration. Powder X-Ray diffraction studies confirmed the crystallinity of the inorganic frameworks. The Fourier Transform infrared spectroscopy studies coupled with confocal imaging of the fluorophore tagged MCL embedded hybrids confirmed the presence of the protein. The MCL protein was examined for its ability to cleave DNA, i.e., nuclease activity using pBR322, wherein the form I plasmid is completely transformed into the form II / III at 2 mg/mL concentration of the protein. However, both the hybrids showed a superior nuclease activity as compared to the protein, wherein the CuPNF_MCL showed a threefold greater nuclease activity as compared to the ZIF8_MCL. The greater nuclease activity of CuPNF_MCL is attributable to its mesoporous nature with higher pore size and pore volume as compared to that in case of ZIF8_MCL, which is microporous in nature. Thus, in this paper, we have purified a nuclease like lectin from bitter gourd seeds and improved its nuclease property by converting it into inorganic hybrid nanomaterial of two types wherein higher activity was observed in the material having better porosity and surface area characteristics.

Electrochemical sensing platform for naphthol isomers based on in situ growth of ZIF-8 on reduced graphene oxide by a reaction-diffusion technique.

Enhancing the dispersibility and conductivity is an effective solution to develop the application zeolitic imidazole frameworks (ZIF) in the electrochemical field. This work thus employs a novel reaction-diffusion framework (RDF) technique for the in situ growth of ZIF-8 crystals on graphene oxide (GO@ZIF-8) matrixes. In detail, the outer electrolyte of 2-methyl imidazole naturally diffuses into the inner agar gel matrix containing Zn2+ cations and GO nanosheets. The long reaction-diffusion makes the growth of ZIF-8 crystals controllable in a vertical gradient. After thermal treatment, the title product of ZIF-8 in situ grown on reduced graphene oxide (rGO@ZIF-8) is obtained and thus exhibits good dispersibility, high conductivity, large surface area, and more catalytic sites. The glassy carbon electrode (GCE) was modified by casting the rGO@ZIF-8 suspension. The obtained rGO@ZIF-8/GCE displays excellent catalytic activity toward naphthol (NAP) isomers. Under the optimal conditions, the amperometric currents of 1-NAP and 2-NAP demonstrate the good linear relationship in wide ranges of 0.05-12 µM and 0.02-15 µM, respectively. Their limits of detection are as low as 15 and 17 nM, respectively. The fabricated modified electrode exhibits excellent selectivity, stability, and reproducibility. The sensor is also utilized to detect NAP molecules in real water samples and indicates good accuracy and reliability.

Pressure-induced amorphous zeolitic imidazole frameworks with reduced toxicity and increased tumor accumulation improves therapeutic efficacy In vivo.

Zeolitic Imidazole Frameworks (ZIFs) are widely applied in nanomedicine for their high drug loading, suitable pore size, pH-responsive drug release, and so on. However, fast drug release during circulation, unexpected toxicity to mice major organs, undesirable long-term accumulation in the lung and even death currently hinder their in vivo biomedical applications. Herein, we report an amorphous ZIF-8 (aZIF-8) with high loading of 5-Fu through pressure-induced amorphization. This nano-system avoids early drug release during circulation and provides tumor microenvironment-responsive drug release with improved in vitro cell viability, and survival rate in in vivo evaluations as compared to ZIF-8. Furthermore, aZIF-8 shows longer blood circulation and lower lung accumulation than ZIF-8 at same injected doses. Less drug release during circulation, longer blood circulation, and better biocompatibility of aZIF-8/5-Fu significantly improves its therapeutic efficacy in ECA-109 tumor-bearing mouse, and result in 100% survival rate over 50 days after treatment. Therefore, aZIF-8 with favorable biocompatibility and long blood circulation is expected to be a promising nano-system for efficacious cancer therapy in vivo.

Electrochemical sensing for naphthol isomers based on the in situ growth of zeolitic imidazole framework-67 on ultrathin CoAl layered double hydroxide nanosheets by a reaction-diffusion technique.

It is established that ultrathin layered double hydroxide nanosheets (LDHNS) and zeolitic imidazole frameworks (ZIF) are desirable electrochemical sensing modifiers owing to their large surface area and abundant catalytic sites. Integration of them is thus an effective solution to maximize their electrocatalytic activity. Herein, a novel reaction-diffusion framework (RDF) technique is applied for the in situ growth of ZIF-67 on ultrathin CoAl-LDHNS (CoAl-LDHNS@ZIF-67). In a confined space of the agar gel matrix of RDF, the coordination reaction between organic ligands and CoAl-LDHNS without an additional Co2+ source achieves the controllable growth of ZIF-67 crystals through a long vertical diffusion. The prepared composite comprises both CoAl-LDHNS and ZIF-67 components with a certain ratio and provides a large surface area and amply catalytic sites, thus realizing a rapid transfer of electron and mass. The CoAl-LDHNS@ZIF-67 modified electrode is employed for the simultaneous detection of naphthol isomers by differential pulse voltammetry. Naphthol isomers display anodic reactions with a wide peak potential difference, allowing their simultaneous detection feasible. Voltammetric responses of α-naphthol and ß-naphthol follow good linearity against the concentration in a wide range from 0.3 to 150 µM with limits of detection of 54 and 82 nM, respectively. The proposed sensor also demonstrates excellent selectivity, stability, reproducibility, and practicability for the simultaneous detection of naphthol isomers.

Strategy for Encapsulation of CdS Quantum Dots into Zeolitic Imidazole Frameworks for Photocatalytic Activity.

Encapsulating CdS quantum dots (QDs) into zeolitic imidazole framework-8 (ZIF-8) can offer several advantages for photocatalysis. Various types of capping agents have been used to encapsulate QDs into ZIF-8 nanopores. An effective method for encapsulating CdS QDs into ZIF-8 is to use 2-mercaptoimidazole as the capping agent. This is because 2-mercaptoimidazole is similar to the imidazolate ligands of ZIFs and can used for capping active species with simultaneous encapsulation during the crystal growth of ZIF-8. Compared to other widely used capping agents such as polyvinylpyrrolidone (PVP), using 2-mercaptoimidazole for encapsulating CdS QDs into ZIF-8 revealed photocatalytic effects along with the molecular sieving effect when using differently sized molecular redox mediators such as methyl viologen (MV2+) and diquat (DQ2+).

A Zeolitic-Imidazole Frameworks-Derived Interconnected Macroporous Carbon Matrix for Efficient Oxygen Electrocatalysis in Rechargeable Zinc-Air Batteries.

Nanostructures derived from zeolitic-imidazole frameworks (ZIFs) gain much interest in bifunctional oxygen electrocatalysis. However, they are not satisfied well for long-life rechargeable zinc-air batteries due to the limited single particle morphology. Herein, the preparation of an interconnected macroporous carbon matrix with a well-defined 3D architecture by the pyrolysis of silica templated ZIF-67 assemblies is reported. The matrix catalyst assembled zinc-air battery exhibits a high power density of 221.1 mW cm-2 as well as excellent stability during 500 discharging/charging cycles, surpassing that of a commercial Pt/C assembled battery. The synergistic effect from the interconnected macroporous structure together with abundant cobalt-nitrogen-carbon active sites justify the excellent electrocatalytic activity and battery performance. Considering the advanced nanostructures and performance, the as-synthesized hybrid would be promising for rechargeable zinc-air batteries and other energy technologies. This work may also provide significant concept in the view of electrocatalysis design for long-life battery.

CuO-ZnO heterojunction derived from Cu2+-doped ZIF-8: A new photoelectric material for ultrasensitive PEC immunoassay of CA125 with near-zero background noise.

By direct calcination of Cu2+-doped ZIF-8 in oxygen atmosphere, a new photoelectric material, CuO-ZnO heterojunction, was prepared. The morphology and structure were investigated in detail by several methods, such as scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption method and X-ray diffraction. Under visible light irradiation, CuO-ZnO heterojunction exhibits excellent PEC behavior in aqueous media with the presence of ascorbic acid (AA) and dissolved oxygen at -0.3 V. Taking the CA125-antibody functionalized CuO-ZnO heterojunction (CuO-ZnO-Ab2) as a signal source, a novel photoelectrochemical (PEC) immunosensing platform was developed for ultrasensitive assay of CA125. Because of the target-induced introduction of photoelectric material to the sensing platform, the proposed PEC immunosensor has excellent performance for CA125 assay: near-zero background noise, wide linear response range (1 × 10-5 U/mL to 100 U/mL) and low detection limit (3.16 × 10-6 U/mL). The developed CuO-ZnO heterojunction and the related PEC sensing platform may have promising applications in ultrasensitive and highly accurate monitoring of various proteins in bioanalysis and disease diagnosis.