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Nanozymes with intrinsic enzyme-like properties and excellent stability are promising alternatives to natural enzymes. Yet, their low density of active sites and unclear crystal structure have been the major obstacles that impede their progress. Single-atom nanozymes (SAzymes) have emerged as a unique system to mitigate these issues, due to maximal atomic utilization, well-defined electronic and geometric structures, and outstanding catalytic activity distinct from their nanosized counterparts. Furthermore, the homogeneously dispersed active sites and well-defined coordination structures provide rare pathways to shed light on the catalytic mechanisms. In this review, we summarize the latest progress in the rational design and engineering of SAzymes and their applications in biomedicine and biosensing. We then conclude the review with highlights of the remaining challenges and perspectives of this emerging technology.
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Nanozymes—Hitting the Biosensing “Target”
Nanozymes are a class of artificial enzymes that have dimensions in the nanometer range and can be composed of simple metal and metal oxide nanoparticles, metal nanoclusters, dots (both quantum and carbon), nanotubes, nanowires, or multiple metal-organic frameworks (MOFs). They exhibit excellent catalytic activities with low cost, high operational robustness, and a stable shelf-life. More importantly, they are amenable to modifications that can change their surface structures and increase the range of their applications. There are three main classes of nanozymes including the peroxidase-like, the oxidase-like, and the antioxidant nanozymes. Each of these classes catalyzes a specific group of reactions. With the development of nanoscience and nanotechnology, the variety of applications for nanozymes in diverse fields has expanded dramatically, with the most popular applications in biosensing. Nanozyme-based novel biosensors have been designed to detect ions, small molecules, nucleic acids, proteins, and cancer cells. The current review focuses on the catalytic mechanism of nanozymes, their application in biosensing, and the identification of future directions for the field.
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- Award ID(s):
- 1946202
- PAR ID:
- 10318360
- Date Published:
- Journal Name:
- Sensors
- Volume:
- 21
- Issue:
- 15
- ISSN:
- 1424-8220
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract MXene‐based nanozymes (recently called MXenzymes) have emerged as promising candidates for environmental remediation, biomedical, (bio‐)catalytic, and sensing technologies due to their surface tunability, tailored electronic properties, remarkable electrical conductivity, and high surface area. These materials offer significant advantages over traditional enzymes, such as enhanced stability, tunable catalytic activity, and multifunctionality. However, despite the increasing number of studies in this field, critical challenges remain, including the long‐term stability, the lack of studies on structure–activity relationships to better understand the catalytic mechanisms, and the scalability required for real‐world applications. This mini‐review provides a comprehensive overview of the most recent advancements in MXenzymes, focusing on the type of MXenes used, the reported enzyme‐like activity, and the role of the photothermal effects in enhancing their catalytic performance. Moreover, key limitations, such as oxidation susceptibility, biocompatibility concerns, and the scarce in‐depth mechanistic studies, are critically examined. Last, the necessary steps to transition from proof‐of‐concept studies to real‐world applications are discussed. By addressing the listed fundamental challenges, MXenzymes could represent a valuable and effective alternative to natural enzymes used in catalysis, medicine, and environmental science.more » « less
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Abstract Fe–N–C single‐atom catalysts (SACs) exhibit excellent peroxidase (POD)‐like catalytic activity, owing to their well‐defined isolated iron active sites on the carbon substrate, which effectively mimic the structure of natural peroxidase's active center. To further meet the requirements of diverse biosensing applications, SAC POD‐like activity still needs to be continuously enhanced. Herein, a phosphorus (P) heteroatom is introduced to boost the POD‐like activity of Fe–N–C SACs. A 1D carbon nanowire (FeNCP/NW) catalyst with enriched Fe–N4active sites is designed and synthesized, and P atoms are doped in the carbon matrix to affect the Fe center through long‐range interaction. The experimental results show that the P‐doping process can boost the POD‐like activity more than the non‐P‐doped one, with excellent selectivity and stability. The mechanism analysis results show that the introduction of P into SAC can greatly enhance POD‐like activity initially, but its effect becomes insignificant with increasing amount of P. As a proof of concept, FeNCP/NW is employed in an enzyme cascade platform for highly sensitive colorimetric detection of the neurotransmitter acetylcholine.more » « less
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null (Ed.)Single-atom catalysts (SACs) exhibit unique catalytic property and maximum atom efficiency of rare, expensive metals. A critical barrier to applications of SACs is sintering of active metal atoms under operating conditions. Anchoring metal atoms onto oxide supports via strong metal-support bonds may alleviate sintering. Such an approach, however, usually comes at a cost: stabilization results from passivation of metal sites by excessive oxygen ligation—too many open coordination sites taken up by the support, too few left for catalytic action. Furthermore, when such stabilized metal atoms are activated by reduction at elevated temperatures they become unlinked and so move and sinter, leading to loss of catalytic function. We report a new strategy, confining atomically dispersed metal atoms onto functional oxide nanoclusters (denoted as nanoglues) that are isolated and immobilized on a robust, high-surface-area support—so that metal atoms do not sinter under conditions of catalyst activation and/or operation. High-number-density, ultra-small and defective CeOx nanoclusters were grafted onto high-surface-area SiO2 as nanoglues to host atomically dispersed Pt. The Pt atoms remained on the CeOx nanoglue islands under both O2 and H2 environment at high temperatures. Activation of CeOx supported Pt atoms increased the turnover frequency for CO oxidation by 150 times. The exceptional stability under reductive conditions is attributed to the much stronger affinity of Pt atoms for CeOx than for SiO2—the Pt atoms can move but they are confined to their respective nanoglue islands, preventing formation of larger Pt particles. The strategy of using functional nanoglues to confine atomically dispersed metal atoms and simultaneously enhance catalytic performance of localized metal atoms is general and takes SACs one major step closer to practical applications as robust catalysts for a wide range of catalytic transformations.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/s21155201
