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Biomimic nanozymes coassembled by peptides or proteins and small active molecules provide an effective strategy to design attractive nanozymes. Although some promising nanozymes have been reported, rational regulation for higher catalytic activity of biomimic nanozymes remains challenging. Hence, we proposed a novel biomimic nanozyme by encapsulating the coassembly of hemin/bovine serum albumin (BSA) in zeolite imidazolate frameworks (ZIF-8) to achieve controllable tailoring of peroxidase-like activity via the confinement effect. The assembly of Hemin@BSA was inspired by the structure of horseradish peroxidase (HRP), in which hemin served as the active cofactor surrounded by BSA as a blocking pocket to construct a favorable hydrophobic space for substrate enrichment. Benefiting from the confinement effect, ZIF-8 with a porous intracavity was identified as the ideal outer layer for Hemin@BSA to accelerate substrate transport and achieve internal circulation of peroxidase-like catalysis, significantly enhancing its peroxidase-like activity. Especially, the precise encapsulation of Hemin@BSA in ZIF-8 could also prevent it from decomposition in harsh environments by rapid crystallization around Hemin@BSA to form a protective shell. Based on the improved peroxidase-like activity of Hemin@BSA@ZIF-8, several applications were successfully performed for the sensitive detection of small molecules including H

Acute myocardial infarction (AMI)-related microRNAs (miRNAs) in circulating blood have been proved as promising biomarkers for AMI diagnosis. The detection of these miRNAs at ultralow levels usually requires nucleic acid amplification strategies to improve the sensitivity at the cost of time. Given that the first hour after an AMI attack is the golden time for saving AMI patients' lives, shortening the time of ultrasensitive miRNA analysis is of great significance for clinical AMI diagnosis. Toward this goal, here we present a direct electrochemiluminescence (ECL) sensing strategy for fast and ultrasensitive miRNA detection, circumventing the time-consuming signal amplification steps. Target miRNAs are directly hybridized with two probe strands that are attached to a covalently hemin-modified spherical nucleic acid enzyme (SNAzyme) and a truncated triangular pyramid DNA nanoplatform on the electrode, respectively. Both of them improve the ECL signal and meanwhile reduce the background, thereby remarkably promoting the detection sensitivity of target miRNAs. It enables the rapid detection of an AMI-related miRNA (miR-499) at 10 aM in human serum within 30 min using the SNAzyme-catalyzed luminol-H

Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag+) causes serious harm to organisms after bioaccumulation and biomagnification, posing urgent demand for the rapid, efficient, and simply operated Ag+ detection techniques. In this work, a fast, portable, and label-free Ag+ detection sensor based on a Ti3C2Tx MXene field-effect transistor (FET) is reported. The Ti3C2Tx MXene works as the sensing element in the FET sensor, which shows excellent sensing performance, i.e., fast response (few seconds) and good sensitivity and selectivity to Ag+ without any detection label or probe. Utilizing the visual photograph, transmission electron microscopy image, and Ag elemental mapping analysis, the sensing mechanism of the label-free Ti3C2Tx MXene FET sensor is demonstrated to be the in situ reduction of Ag+ and the formation of Ag nanoparticles (AgNPs). Moreover, Ag+ detection in real samples shows that the proposed FET devices have satisfactory sensing capability for Ag+ in tap water and river water. This study puts forward a novel FET strategy for Ag+ detection in aqueous systems, which is of essential and inspiring meaning for motivating the potential applications of MXene-based sensor devices in analytical applications and the realization of on-site environmental monitoring.

Silver (Ag) is a widely used heavy metal, and its oxidation state (Ag

A novel electrochemiluminescence (ECL) sensor based on carbon quantum dots (CQDs) immobilized on graphene (GR) has been first developed for the determination of chlorinated phenols (CPs) in water. The detection is based on the ECL signals from the interaction between the analytes and the excited CQDs (C(*+)) using S2O8(2-) as coreactant. GR facilitates both C(•-) and SO4(•-) production, resulting in a high yield of C(*+), and the multistage amplification effect leads to a nearly 48-fold ECL amplification. Pentachlorophenol (PCP) is often monitored as an important indicator for CPs in real environmental samples, but its ultratrace and real-time analysis is an intractable issue in environmental monitoring. The resulting ECL sensor enables the real-time detection of PCP with unprecedented sensitivity reaching 1.0 × 10(-12) M concentration in a wide linear range from 1.0 × 10(-12) to 1.0 × 10(-8) M. The ECL sensor showed high selectivity to CPs, especially to PCP. The practicability of the sensing platform in real water samples showed ideal recovery rates. It is envisaged that the eco-friendly and recyclable sensor could be employed in the identification of key CPs in the environment.