Accelerated and precise identification of antioxidants and pesticides using a smartphone-based colorimetric sensor array

A simple colorimetric and paper-based-smartphone sensing platform based on the enhanced peroxidase-like activity of Al doping Prussian blue for point-of-care detection of GSH

Glutathione (GSH) is a very important antioxidant and also participates in many important physiological processes, accurate determination of GSH in food and blood fluid is crucial for human health. Herein, we introduce a simple colorimetric and paper-based-smartphone dual signal output platform for point-of-care (POC) detection of GSH in garlic and human serum. The experiment revealed that the peroxidase-like activity of Aluminum-doped Prussian blue (AlPB) could be enhanced by the doping of Al element on Prussian blue. AlPB exhibited excellent peroxidase-like activity and efficiently catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to generate blue oxidized TMB, resulting in an absorbance and color-based-smartphone dual signal readouts. Enzyme kinetic studies also indicated that the AlPB showed high affinity towards TMB. Hence, a reliable colorimetric and color-based-smartphone dual signal readouts assay was constructed based on AlPB-mediated the peroxidase-like activity, it was used for highly sensitive colorimetric and POC detection of GSH in food and human serum within 7 min with a wide range of linear response from 1 to 20 μM, a low detection limit of 0.1748 μM. This work demonstrates a novel and versatile strategy to develop superior peroxidase mimics and holds great potential for rapid and portable detection of GSH in food, healthcare and clinical diagnosis, and also open promising avenues for more powerful paper-based POC tests.

Self-supplying of hydrogen peroxide nanozyme-based colorimetric sensing array as electronic tongue for biothiol detection and disease discrimination

Developing a highly reliably and sensitive nanozyme-based colorimetric sensor array for biothiols analysis is critical owing to they play an essential role in diagnosing disease. The required procedure of introducing hydrogen peroxide (H2O2) directly into the colorimetric reaction systems in traditional biothiols array analysis limits its applicability due to its poor stability and inhibition in biomolecular activity by using the high-concentration H2O2. Herein, we carried out a "green" and convenient approach to propose for the biothiol detection and disease discrimination through nanozymes-based colorimetric sensor technique without adding the high-concentration H2O2 for the first time. The copper peroxide nanodots (CPNs) and graphene oxide (GO) modified CPNs (GO@CPNs) are as sensing units to release H2O2 and Cu2+ under acidic conditions, which triggered a Fenton-like reaction, generating hydroxyl radical (•OH) to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) accompanied by a change in TMB color from colorless to blue. Due to the synergistic effect of Cu2+ and GO, GO@CPNs showed increased the activity of peroxidase-like compared to CPNs. Therefore, the catalytic abilities of nanozymes-based colorimetric sensing array were inhibited to different degrees by different biothiols (i.e., glutathione (GSH), cysteine (Cys) and homocysteine (Hcy)) with a detection limit of 50 nM, which could be precisely distinguished by using pattern recognition method. Besides, the detection of a single biothiol at different concentrations and mixtures of biothiols has also been achieved. Moreover, the real biological samples (cells and human serum) can be accurately discriminated through array method, which demonstrated its potential application of medical diagnosis.

Development of a cholinesterase sensor array based on manganese dioxide nanosheet and carbon dots for fluormetric discrimination of organophosphorus pesticide

Recently, the integration of advanced nanomaterials with conventional enzymatic inhibition methods offered a promising strategy for the development of efficient organophosphate pesticides (OPs) discrimination methods. Herein, we proposed to design a sensitive sensor array based on the fluorescence "turn-off" detection model of carbon dots (CDs) - MnO2 nanosheets (NSs) and three biogenic cholinesterase enzymes (ChEs) as recognition elements for six popular and typical OPs detection. The three ChEs can be inhibited to a different extent by the OPs, leading to diverse fluormetric signal output pattern of each pesticide. Subsequently, linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA) was used to accurately investigate the effectiveness of the sensor array in screening pesticides at 0.1-20 μg/mL. The sensor array displayed high sensibility and well storage stability. More importantly, the sensor array's strong immunity to various interference and the precise recognizing of OPs spiked in grape and pepper samples highlighted its practical feasibility. This promising fluormetric sensor array provides a significant advance for the identification and recognition of OPs residues in cops matrices.

Colorimetric sensor array constructed based on bimetallic porphyrin-based metal organic framework nanozyme for the detection and recognition of tannic acid

Colorimetric sensor arrays based on nanozymes hold promise for the simultaneous detection of multiple target analytes, but the rational design of nanozymes with high catalytic activity remains a major challenge. Herein, a porphyrin-based metal organic framework (Zr-MOFFe/CuPh) with bimetallic reaction centers (M - N4) were prepared by solvothermal method. Zr-MOFFe/CuPh nanozyme formed a redox cycle between different valence states, which significantly improved the peroxidase-like activity of the nanozyme, and further revealed its catalytic mechanism. In view of tannic acid (TA) can effectively inhibit nanozyme activity, an enzyme-driven colorimetry method was designed to detect TA, the method showed a good linear relationship in the range of 0.5-6.0 μM and the detection limit was as low as 0.143 μM. Interestingly, due to the varying inhibition levels of antioxidant molecules, resulting in different colorimetric response and forming a unique "fingerprint". A three-channel colorimetric sensor array to accurately identify and detect TA and other antioxidants was developed based on Zr-MOFFe/CuPh as a single sensing receptor. The proposed colorimetric sensor array achieved 100 % accuracy in identifying TA and other antioxidants, and was capable of measuring TA in real samples. This work not only designed an effective method for the TA detection, but also carried out a promising way for the application of bimetallic nanozymes in food monitoring.

Colorimetric/fluorescent dual-mode biosensor based on metalloporphyrin covalently modified NH2-MIL-101(Fe) with highly efficient peroxidase-like activity for the detection of tetracycline in honey samples

Accurate detection of tetracycline residue is of great significance for ensuring product quality and protecting human health. Here, a colorimetric/fluorescent dual-mode biosensor was developed for the detection of tetracycline in honey by using metalloporphyrin [TCPP(Fe)] covalently modified NH2-MIL-101(Fe) [named NH2-MIL-101(Fe)@TCPP(Fe)]. The morphology, chemical structure and peroxidas-like activity of this hybrid nanozyme were comprehensively studied. Based on excellent catalytic activity and intrinsic fluorescence of NH2-MIL-101(Fe)@TCPP(Fe), a colorimetric/fluorescent dual-mode biosensor was developed for the detection of tetracycline. The primary mechanism for this dual mode biosensor was the inhibitory effect of tetracycline on on NH2-MIL-101(Fe)@TCPP(Fe) catalyzed chromatic reaction between H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB)/o-phenylenediamine (OPD), which was ascribed to the consumption of ·OH by tetracycline and the adsorption of tetracycline on the surface of NH2-MIL-101(Fe)@TCPP(Fe). After effective validation, this colorimetric/fluorescent dual mode method was applied to detect tetracycline residues in three actual honey samples.

Optical biosensor arrays based on nanozymes for environmental monitoring and food safety detection: principles, design, and applications

Typical biosensing platforms are based on the "lock-and-key" approach, providing high specificity and sensitivity for environmental and food safety monitoring. However, they are limited in their ability to detect multiple analytes simultaneously. With the use of pattern identification methods, biosensor arrays can detect faint fluctuations caused by multiple analytes with similar properties in complex systems. As a simple and efficient detection tool, optical biosensor arrays have become crucial for on-site and visible environmental and food safety monitoring. To enhance their practical applications, enzyme-like nanomaterial (nanozyme)-based biosensor arrays have been developed and integrated into optical biosensing platforms, leveraging their exposed active sites and tunable catalytic capabilities. For the development of an optical biosensor array, it is essential to incorporate multiple biosensing elements that can specifically interact with analytes to produce distinct "fingerprint" signals, enabling the differentiation of different targets via pattern identification. This review provides a comprehensive overview of nanozyme-based optical biosensor arrays for environmental and food safety monitoring. It explores the selective approaches of nanozyme-based colorimetric and fluorescent biosensor arrays, compares detection platforms utilizing nanozyme systems, and emphasizes the application of nanozyme-based optical biosensor arrays for environmental and food hazard monitoring. By evaluating current trends and summarizing both prospects and challenges, this review offers valuable guidance for the rational design of unique nanozyme-based optical biosensor arrays.

A SERS/colorimetric biosensor based on AuNSs@Ag core-shell Prussian blue nanozyme for non-interference and rapid detection of Staphylococcus aureus in milk

A AuNSs@PB@Ag-Apt surface-enhanced Raman scattering (SERS) probe has been developed by embedding Prussian blue (PB) between Au core and Ag shell. The PB SERS probe illustrates strong SERS activity in the Raman silent region of 2070 cm-1, and has a zero background signal, ensuring high sensitivity for the detection of Staphylococcus aureus (S. aureus). Moreover, the assemble SERS probe exhibits the catalytic function of peroxidase (POD), enabling the catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) for colorimetric detection. Additionally, we prepared lectin-functionalized magnetic nanoparticles (F-MNPs-ConA) that demonstrate superior adsorption capabilities towards S. aureus, achieving an impressive adsorption value of up to 98.62%. The F-MNPs-ConA/S. aureus/AuNSs@PB@Ag-Apt sandwich structure constructed by the above SERS probe and magnetic nanoparticles achieves highly sensitive detection of S. aureus. The detection range is 1 × 100 ~ 1 × 108 CFU·mL-1, and the detection limit (LOD) is 1 CFU·mL-1. Notably, this method can be integrated into smartphones, facilitating rapid and on-site detection of S. aureus. Compared with similar biosensors, this biosensor offers distinct advantages, including a wide detection range and a low detection limit. The reliability of the biosensor was confirmed by its application in milk, where the recovery ranged from 93.66 to 120.8%. The dual-mode SERS/colorimetric detection, non-interfering nature, magnetic enrichment, and reusability of the biosensor make it a promising tool for point-of-care testing (POCT).

Recent Advances in Nanozyme-Based Sensing Technology for Antioxidant Detection

Antioxidants are substances that have the ability to resist or delay oxidative damage. Antioxidants can be used not only for the diagnosis and prevention of vascular diseases, but also for food preservation and industrial production. However, due to the excessive use of antioxidants, it can cause environmental pollution and endanger human health. It can be seen that the development of antioxidant detection technology is important for environment/health maintenance. It is found that traditional detection methods, including high performance liquid chromatography, gas chromatography, etc., have shortcomings such as cumbersome operation and high cost. In contrast, the nanozyme-based detection method features advantages of low cost, simple operation, and rapidity, which has been widely used in the detection of various substances such as glucose and antioxidants. This article focuses on the latest research progress of nanozymes for antioxidant detection. Nanozymes for antioxidant detection are classified according to enzyme-like types. Different types of nanozyme-based sensing strategies and detection devices are summarized. Based on the summary and analysis, one can find that the development of commercial nanozyme-based devices for the practical detection of antioxidants is still challenging. Some emerging technologies (such as artificial intelligence) should be fully utilized to improve the detection sensitivity and accuracy. This article aims to emphasize the application prospects of nanozymes in antioxidant detection and to provide new ideas and inspiration for the development of detection methods.