BC@DNA-Mn3(PO4)2 Nanozyme for Real-Time Detection of Superoxide from Living Cells

Integrating of analytical techniques with enzyme-mimicking nanomaterials for the fabrication of microfluidic systems for biomedical analysis

Bioanalysis faces challenges in achieving fast, reliable, and point-of-care (POC) determination methods for timely diagnosis and prognosis of diseases. POC devices often display lower sensitivity compared to laboratory-based methods, limiting their ability to quantify low concentrations of target analytes. To enhance sensitivity, the synthesis of new materials and improvement of the efficiency of the analytical strategies are necessary. Enzyme-mimicking materials have revolutionized the field of the fabrication of new high-throughput sensing devices. The integration of microfluidic chips with analytical techniques offers several benefits, such as easy miniaturization, need for low biological sample volume, etc., while also enhancing the sensitivity of the probe. The use enzyme-like nanomaterials in microfluidic systems can offer portable strategies for real-time and reliable detection of biological agents. Colorimetry and electrochemical methods are commonly utilized in the fabrication of nanozyme-based microfluidic systems. The review summarizes recent developments in enzyme-mimicking materials-integrated microfluidic analytical methods in biomedical analysis and discusses the current challenges, advantages, and potential future directions.

Manganese-Based Nanozymes: Preparation, Catalytic Mechanisms, and Biomedical Applications

Manganese (Mn) has attracted widespread attention due to its low-cost, nontoxicity, and valence-rich transition. Various Mn-based nanomaterials have sprung up and are employed in diverse fields, particularly Mn-based nanozymes, which combine the physicochemical properties of Mn-based nanomaterials with the catalytic activity of natural enzymes, and are attracting a surge of research, especially in the field of biomedical research. In this review, the typical preparation strategies, catalytic mechanisms, advances and perspectives of Mn-based nanozymes for biomedical applications are systematically summarized. The application of Mn-based nanozymes in tumor therapy and sensing detection, together with an overview of their mechanism of action is highlighted. Finally, the prospective directions of Mn-based nanozymes from five perspectives: innovation, activity enhancement, selectivity, biocompatibility, and application broadening are discussed.

Mechanism and Application of Surface-Charged Ferrite Nanozyme-Based Biosensor toward Colorimetric Detection of l-Cysteine

Peroxidase-like nanozymes with robust catalytic capacity and detection specificity have been proposed as substitutes to natural peroxidases in biochemical sensing. However, the catalytic activity enhancement, detection mechanism, and application of nanozyme-based biosensors toward l-cysteine (l-Cys) detection still remain significant challenges. In this work, a doped ferrite nanozyme with well-defined structure and surface charges is fabricated by a two-step method of continuous flow coprecipitation and high-temperature annealing. The resulted ferrite nanozyme possesses an average size of 54.5 nm and a zeta-potential of 6.45 mV. A high-performance biosensor is manufactured based on the peroxidase-like catalytic feature of the doped ferrite. The ferrite nanozyme can oxidize the 3,3',5,5'-tetramethylbenzidine (TMB) with the assistance of H₂O₂ because of the instinctive capacity to decompose H₂O₂ into ·OH. The Michaelis-Menten constants (0.0911 mM for TMB, 0.140 mM for H₂O₂) of the ferrite nanozyme are significantly smaller than those of horseradish peroxidase. A reliable colorimetric method is established to selectively analyze l-Cys via a facile mixing-and-detecting methodology. The detection limit and linear range are 0.119 μM and 0.2-20 μM, respectively. Taking the merits of the ferrite nanozyme-based biosensors, the l-Cys level in the human serum can be qualitatively detected. It can be anticipated that the surface-charged ferrite nanozyme shows great application prospects in the fields of bioanalytical chemistry and point-of-care testing.

Enzyme-nanozyme cascade colorimetric sensor platform: a sensitive method for detecting human serum creatinine

Creatinine, as a significant biomarker for kidney, thyroid, and muscle dysfunction-related diseases, detection is of great important meaning. In this paper, an enzyme-nanozyme cascade sensing platform was developed for visual creatinine detection. Perovskite oxide BiFeO₃ synthesized by a sol-gel method was applied as a nanozyme, showing excellent peroxidase-like activity. During detection, creatinine was oxidized in turn by three natural enzymes (creatinase, creatininase, and sarcosine oxidase) to produce H₂O₂, and H₂O₂ was then catalyzed by the BiFeO₃ nanozyme, resulting in the change of achromatous 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB). Based on this principle, visual quantification of creatinine was realized. Due to the high stability and catalytic efficiency of nanozyme, the cascade sensing platform can be used to detect creatinine in a broad range of 0.5-150 μM with a detection limit of 0.09 μM. Meanwhile, thanks to the specificity of the natural enzymes, the platform exhibited admirable selectivity for creatinine determination despite the existence of a variety of interfering substances, which were successfully adopted to measure the level of creatinine in human serums. The cascade sensing platform is expected to serve the determination of a large number of biomarkers by simply alternating the natural enzymes.

BSA-stabilized manganese phosphate nanoflower with enhanced nanozyme activity for highly sensitive and rapid detection of glutathione

The development of an efficient protein-inorganic nanohybrid with superior nanozyme activity for highly sensitive detection of glutathione (GSH) is essential for early diagnosis of human diseases. Herein, a rapid and highly sensitive colorimetric assay using self-assembled bovine serum albumin-hydrated manganese phosphate nanoflowers (MnPNF) as a biomimic oxidase is developed for GSH detection in human serum. The BSA can complex with Mn²⁺ to serve the nucleation center to produce MnPNF in the presence of phosphate-buffered saline (PBS). The morphology and surface characterization results show that the MnPNF is assembled with hierarchical nanoplates to form 500 nm nanoflowers. The oxidase-like activity of MnPNF is based on the redox reaction with 3,3',5,5'-tetramethylbenzidine. However, the addition of GSH can reduce MnPNF to Mn²⁺, and subsequently supresses the oxidase-like activity and a yellow color at 450 nm is observed in the presence of H₂SO₄. The MnPNF-based nanozyme exhibits excellent sensing ability toward GSH detection, and a good linear relationship between the change in absorbance at 450 nm and the added amounts of GSH at 50 nM-10 μM with low limits of detection of 20 and 26.6 nM in the PBS and diluted human serum, respectively, is observed. Moreover, the sensing probe shows a superior selectivity over the other 16 interferences, which drive the determination of GSH feasible in real human serum. Since the MnPNF can be simply prepared at room temperature and no functionalization is required, this assay can be used to design the highly efficient biomimic oxidase for effective sensing of GSH and other disease-related biomolecules in biological fluid samples.

Highly Efficient Synergistic Biocatalysis Driven by Stably Loaded Enzymes within Hierarchically Porous Iron/Cobalt Metal-Organic Framework via Biomimetic Mineralization

The integration of multimodal chemo-/bio-catalysis for efficient cascade reactions has long provided broad prospects in the field of biotechnology for ages. In this work, we describe the synthesis of a...

Selective detection of glutathione by flower-like NiV2O6 with only peroxidase-like activity at neutral pH

In view of the broad application prospect of peroxidase-like nanozymes in biomedical analysis, it is of great significance to eliminate the interference of their oxidase-like activity and enable them to work under neutral conditions. Herein, flower-like NiV₂O₆ was synthesized and their enzyme-mimicking activity was investigated. Through the regulation of pH, NiV₂O₆ nanozyme showed only peroxidase-like activity but not oxidase-like activity under neutral conditions, which could catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine into its blue product in the presence of H₂O₂. Furthermore, based on the competitive effect of glutathione (GSH) on the catalytic activity of nanozymes, a semi-quantitative/quantitative colorimetric assay was established for GSH detection by using peroxidase-like NiV₂O₆. The assay exhibited a good linear relationship in GSH concentration ranging from 3-100 μmol L^-1, with a detection limit of 0.89 μmol L^-1. Moreover, in the presence of formaldehyde as masking agent, this method showed satisfactory specificity for GSH under the interference of a variety of interfering substances and even biothiols. Concerning the practical application, the system was applied to monitor GSH level in fetal bovine serum, human serum and SiHa cells. Satisfyingly, the obtained results were consistent well with those of Ultra performance liquid chromatography (UPLC) and assay kit, indicating the constructed assay has great potential in clinical application.