Design and Construction of Enzyme–Nanozyme Integrated Catalyst as a Multifunctional Detection Platform

Uniform PtCoRuRhFe high-entropy alloy nanoflowers: Multi-site synergistic signal amplification for colorimetric assay of captopril

Uniform PtCoRuRhFe high-entropy alloy nanoflowers (HEANFs) were fabricated by a simple wet-chemical co-reduction method in oleylamine for quantitative colorimetric determination of captopril (CAP) based on multi-site synergistic signal amplification. Specifically, the peroxidase mimetic activity of the PtCoRuRhFe HEANFs was examined through catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, whose catalytic mechanism was investigated by electron paramagnetic resonance (EPR) spectroscopy. The role of the ·O2- was figured out during the catalytic procedure. Further, the oxidation of TMB (oxTMB) can be effectively reduced by CAP, accompanied by quickly transforming the solution color from blue to colorless. More importantly, the absorbance at 652 nm is linearly related to the CAP concentration in a range 5.0-50.0 mM with a low detection limit of 2.82 mM. The method has been applied to the determination of CAP in human urine samples. It offers a simple and high-efficiency method for facile and visual detection of CAP in hospitals.

When nanozymes meet enzyme: Unlocking the dual-activity potential of integrated biocomposites

Integrating enzymes and nanozymes in various applications is a topic of significant interest. The researchers have explored the encapsulation of enzymes using diverse nanostructures to create nanomaterial-enzyme hybrids. These nanomaterials introduce unique properties that contribute to the additional activity along with the stabilization of enzymes in immobilized form, enabling a cascade of second-order reactions. This review centers on dual-activity nanozymes, providing insights into their applications in biosensors and biocatalysis. These applications leverage the enhanced catalytic activity and stability offered by dual-activity nanozymes. These nanozymes find promising applications in fields like bioremediation, offering eco-friendly solutions for mitigating environmental pollution while showing potential in medical diagnostics. The review delves into various techniques for creating enzyme-nanozyme hybrid catalysts, including adsorption, encapsulation, and incorporation methods. The review also addresses the challenges that must be overcome, such as overlapping catalytic surfaces and disparities in reaction rates in multi-enzyme cascade reactions. It concludes by presenting strategies to tackle these issues and offers insights into the field's promising future, suggesting that machine learning may drive further advancements in enzyme-nanozyme integration. This comprehensive exploration illuminates the present and charts a promising course for future innovations in the seamless integration of enzymes and nanozymes, heralding a new era of catalytic possibilities.

Metal-organic frameworks for enzyme immobilization and nanozymes: A laccase-focused review

Laccases are natural catalysts with remarkable catalytic activity. However, their application is limited by their lack of stability. Metal-organic frameworks (MOFs) have emerged as a promising alternative for enzyme immobilization. Enzymes can be immobilized in MOFs via two approaches: postsynthetic immobilization and in situ immobilization. In postsynthetic immobilization, an enzyme is embedded after MOF formation by covalent interactions or adsorption. In contrast, in in situ immobilization, a MOF is formed in the presence of an enzyme. Additionally, MOFs have exhibited intrinsic enzyme-like activity. These materials, known as nanozymes when they have the ability to replace enzymes in certain catalytic processes, have multiple key advantages, such as low cost, easy preparation, and large surface areas. This review presents a general overview of the most recent advances in both enzyme@MOF biocatalysts and MOF-based nanozymes in different applications, with a focus on laccase, which is one of the most widely investigated enzymes with excellent industrial potential.

Ceria-Based Nanozymes in Point-of-Care Diagnosis: An Emerging Futuristic Approach for Biosensing

In recent years, there has been a notable increase in interest surrounding nanozymes due to their ability to imitate the functions and address the limitations of natural enzymes. The scientific community has been greatly intrigued by the study of nanoceria, primarily because of their distinctive physicochemical characteristics, which include a variety of enzyme-like activities, affordability, exceptional stability, and the ability to easily modify their surfaces. Consequently, nanoceria have found extensive use in various biosensing applications. However, the impact of its redox activity on the enzymatic catalytic mechanism remains a subject of debate, as conflicting findings in the literature have presented both pro-oxidant and antioxidant effects. Herein, we creatively propose a seesaw model to clarify the regulatory mechanism on redox balance and survey possible mechanisms of multienzyme mimetic properties of nanoceria. In addition, this review aims to showcase the latest advancements in this field by systematically discussing over 180 research articles elucidating the significance of ceria-based nanozymes in enhancing, downsizing, and enhancing the efficacy of point-of-care (POC) diagnostics. These advancements align with the ASSURED criteria established by the World Health Organization (WHO). Furthermore, this review also examines potential constraints in order to offer readers a concise overview of the emerging role of nanoceria in the advancement of POC diagnostic systems for future biosensing applications.

A novel copper-based nanozyme: fabrication and application for colorimetric detection of resveratrol

A novel nanozyme (urea@Cu-NF) was synthesized by self-assembly of urea and copper phosphate with urea as plasticizer. Urea@Cu-NF exhibited excellent peroxidase-like activity with the ability to oxidize TMB in the presence of H2O2. However, its peroxidase-like activity could be inhibited by resveratrol, leading to an absorption decrease in the intensity of oxTMB. Based on this phenomenon, a colorimetric method was designed for resveratrol detection. The colorimetric reaction could be completed within 20 min with a linear range of 1-120 μM. The limit of detection (LOD) of resveratrol is 0.43 μM. Our experimental results demonstrate that urea@Cu-NF has enormous potential to function as a cheap and accurate quality detection tool.

Peroxidase-like activity of bimetal Cu-Zn oxide mesoporous nanospheres for the determination of o-aminophenol

To enhance the peroxidase-like performance and its application in detection of toxic o-aminophenol (o-AP), a kind of bimetal Cu-Zn oxide-based mesoporous nanosphere (Cu_2/3Zn_1/3O PNPs) was constructed under microwave-radiation conditions. Its mesoporous microstructure and peroxidase-like catalytic activity were investigated in detail. The results showed that Cu_2/3Zn_1/3O PNPs possessed a high specific surface area of 34.89 m²g^-1 and a well-distributed mesoporous size of approximate 6.07 nm, which endowed the superior peroxidase-like performance. The material catalyzes the oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) with K_m/V_max of 0.104 mM/3.79 × 10^-8 M·s^-1 in the presence of H₂O₂. Especially o-AP could exclusively deteriorate the characteristic UV-Vis absorbance intensity at 653 nm (A₆₅₃) of the Cu_2/3Zn_1/3O PNPs-TMB-H₂O₂ system with obvious color change from blue to colorless. Under the optimal conditions, the effect of some interfering substances was low and the limit of detection (LOD) for o-AP was 1.65 × 10^-8 mol/L (S/N = 3). When applied to the colorimetric detection of o-AP in practice, the recovery was between 96.1 and 107.2% with R.S.D. less than 2.04%. The mechanism of synergic-enhancement peroxidase-mimic activity of Cu_2/3Zn_1/3O PNPs and its exclusive colorimetric response to o-AP were proposed as well.