Chromogenic Reaction Research Articles

Au@Pt nanoparticles-based signal-enhanced lateral flow immunoassay for ultrasensitive naked-eye detection of SARS-CoV-2.

With SARS-CoV-2 N protein as a model target, a signal-enhanced LFIA based on Au@Pt nanoparticles (NPs) as labelsis proposed. This Au@Pt NPs combined the distinguished localized surface plasma resonance (LSPR) effect of Au NPs and the ultrahigh peroxidase-like catalytic activity of Pt NPs. Au@Pt NPs could trigger substrate chromogenic reaction, generating acolor signal orders of magnitude darker than their intrinsic color. In the detection, after the coloration of the strips, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 were added, and adark blue chelate (OxTMB) was produced soon, enhancing the band color significantly. After the signal amplification, the naked-eye detection limit for N protein reached 40pg/mL. The detection sensitivity enhanced more than 1000 times than that without signal amplification. Compared with mainstream LFIA requiring complex readout instruments, theAu@Pt-based LFIA achieved a comparable sensitivity usingnaked eyesdetection. This point is crucial, especially for unprofessional users or low-resource areas. Hence, this signal-enhanced LFIA may serve as a sensitive, cost-effective, and user-friendly detection method. It can shorten the testing window period and help identify early infections.

Enantiospecific profiling of D-amino acid for gastric cancer diagnosis by using a biocatalytic MHOF nanoreactor

The dynamic variation of D-amino acids (D-AAs) in human saliva has great potential as the indicator for individual physiological states and disease progression; however, enantiospecific profiling of D-AAs is a great challenge. In this work, a nanoreactor based on mesoporous hydrogen-bonded organic framework (MHOF) has been fabricated for the enantiospecific profiling of D-AAs. The nanoreactor is prepared by using MHOFs as the scaffold to organize the biocatalytic cascade of D-AA oxidase (DAAO) and horseradish peroxidase (HRP). In the meanwhile, the large, stable, and robust transport channels of MHOFs allow the unimpeded transport of the involved biocatalytic substrates. Once D-AA substrates efficiently transport into MHOFs, the chromogenic reactions of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 can be activated. So, using this MHOF nanoreactor, enantiospecific and visual detection of D-AAs can be achieved. Moreover, the stable nanoreactor can be operated in complex solution and utilized for the profiling of D-AA levels in saliva samples collected from gastric cancer patients, suggesting that D-AAs may be a powerful fingerprint for the diagnosis of gastric cancer. Therefore, the fabricated MHOF-based nanoreactor may provide an emerging tool for the enantiospecific profiling of D-AAs and supports the D-AA fingerprint as the indicator of gastric cancer diagnosis.

Ultrasensitive optical biosensing detection and multiple therapy based on an NIR-II thermoelectric nanoheterojunction

An one-to-all optical diagnostic and therapeutic agent, referring to a single nanocatalyst synchronously displaying multiple optical biosensor and therapeutic modes, is still a remarkable promise because of its outstanding capability in tumor. However, nanocatalyst activity is significantly weakened by the limited light absorption property and catalytic efficiency. Here, a unique pyroelectric nanocatalyst, In2S3-CuInS2@red blood cell membrane (In2S3-CIS@RM), with excellent pyroelectric/photothermal conversion capability for boosted peroxidase-mimicking catalytic activity, is rationally developed. The In2S3-CIS@RM displays catalytic capacity by reacting Cu+ with H2O2 to produce highly toxic ·OH, promoted by 808 nm near-infrared (NIR) light-mediated photothermal/pyroelectric therapy. By synergizing this three-modal effect, cancer suppression is realized with an obvious cancer inhibition rate after the introduction of In2S3-CIS@RM into the HepG2 cells and following 808 nm laser irradiation. Meanwhile, an optical biosensor array is constructed through In2S3-CIS@RM-triggered chromogenic reaction for a fast and accurate analysis of five antioxidants. Interestingly, this biosensor array is verified to be effective for accurate monitoring of invasive cancer in early cancer occurrence, benefiting from the superior catalytic activity of In2S3-CIS@RM and abnormal levels of antioxidants in cancer cells. Thus, this study provides an avenue for developing an NIR laser-activatable one-to-all optical diagnostic and therapeutic nanosystem.

Three in one: A multifunctional oxidase-mimicking Ag/Mn3O4 nanozyme for colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria

A multifunctional oxidase-mimicking Ag/Mn3O4 was prepared, catalyzing the 3, 3′, 5, 5′-tetramethylbenzidine (TMB) chromogenic reaction. Six foodborne pathogenic bacteria species, including Escherichia coli, Staphylococcus aureus, Salmonella enterica, Listeria monocytogenes, Bacillus cereus, and Cronobacter sakazakii, were observed to differentially inhibit its oxidase-like activity, resulting in decelerating the TMB chromogenic reaction. Owing to these properties, the following achievements were achieved: colorimetric determination of these bacteria with high sensitivity can be achieved using Ag/Mn3O4 + TMB reaction system; precise identification of these bacteria at different concentrations, including individual bacterium, binary mixtures, and even multivariate mixtures, can be effectively realized by combining the Ag/Mn3O4-based colorimetric sensor array with principal component analysis (PCA); broad-spectrum inactivation of these bacteria can be remarkably realized through catalyzation of Ag/Mn3O4 to generate superoxide anion free radicals. Therefore, our proposed Ag/Mn3O4 holds significant application potential in the colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria.

Ultrasensitive on-site colorimetric detection of Campylobacter in oyster with a portable biosensing platform based on hydroxamate/Fe3+–violurate chromogenic reaction and smartphone

The contamination of Campylobacter in shellfish poses a health risk for its pathogenicity associated with campylobacteriosis. However, an efficient method to detect this risk is unavailable. Herein, we introduce a portable colorimetric biosensing platform that comprises three modules: an enrichment module 1, a binding and transduction module 2, and a smartphone-based module 3. Module 1 is an aptamer-modified 96-well plate for the specific capture of Campylobacter in a simple and high-throughput manner. Module 2 features a bifunctional biopolymer of L-glutamic acid γ-hydroxamate–alginate–Fe3+ coordinating fusarinine C, which can bind the captured Campylobacter cells and transduce them into amplified color signals upon reaction with Fe3+–violurate complexes. Module 1 achieves a capture efficiency of 97.24%, and the subsequent addition of module 2 renders colorimetric indication of Campylobacter ranging from 101 to 106 CFU/mL, achieving an actual limit of detection of 8 CFU/mL validated by Campylobacter single-cells. Moreover, the generated colors can be recognized and converted into cell densities by module 3 with ultrasensitivity. Notably, this biosensor–smartphone platform accomplishe reliable high-throughput colorimetric detection of Campylobacter in real samples with an accuracy of 80%. This work showcases a proof of principle for efficient on-site detection of Campylobacter contamination regarding shellfish farming.

Gold/DNA-Cu2+ Complex Nanozyme-Based Aptamer Lateral Flow Assay for Highly Sensitive Detection of Kanamycin.

Aptamer-based lateral flow analysis (Apt-LFAs) has promising applications in many fields. Nanozymes have demonstrated high potential in improving the performance of Apt-LFAs and have been increasingly utilized in recent studies. In this study, we developed a nanozyme-based Apt-LFA for the rapid and sensitive detection of kanamycin by using a novel dual-functionalized AuNPs@polyA-DNA/GpG-Cu2+ nanozyme as a nanoprobe. In the nanoprobe design, the polyA-cDNA strand can discriminate a kanamycin aptamer from the kanamycin/aptamer complex, and the GpG-Cu2+ complex can amplify the detection signal by catalyzing the chromogenic reaction. The nanozyme Apt-LFA can quantify kanamycin in the range of 1-250 ng/mL with an LOD of 0.08 ng/mL, which demonstrated a 4-fold sensitivity improvement and had a wider linear range than the conventional AuNP-based LFA. The Apt-LFA was successfully applied to the detection of kanamycin in honey with good recoveries. Our dual-functionalized AuNP nanoprobe is easily prepared and can be highly compatible with the conventional AuNP-DNA-based LFA platform; thus, it can be extended to the application of Apt-LFAs for other small molecules.

Fluorescent Iron-Doped Polymer Dot Nanozyme-Based Cascade System for Dual-Mode Detection of Acetylcholinesterase Activity and Its Inhibitors.

The advancement of acetylcholinesterase (AChE) activity and its inhibitor assays is crucial for clinical diagnosis, drug screening, and environmental monitoring. A nanozyme-mediated cascade reaction system could offer promising prospects for a wide range of applications in such biosensing; however, the creation of nanozyme catalysts with diverse functionalities remains a significant challenge. Herein, we have proposed a multifunctional iron-doped polymer dots (Fe-PDs) nanozyme possessing excellent fluorescence and peroxidase (POD)-mimicking activity. Notably, the Fe-PDs nanozyme is capable of catalyzing H2O2 to produce a series of reactive oxygen species, which can simultaneously quench the fluorescence of Fe-PDs and induce a chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB), enabling the dual-mode detection of H2O2 through both fluorescence turn-off and absorbance turn-on signals. Furthermore, by integrating acetylcholine (ACh) and choline oxidase (ChOx), we have developed a three-enzyme (AChE-ChOx-POD) cascade-based fluorometric and colorimetric dual-mode sensing platform for monitoring AChE activity and its inhibitors. The sensitive and convenient dual-mode sensor has achieved low limits of detection with 0.5 mU/mL (fluorometry) and 0.014 mU/mL (colorimetry) for AChE, respectively, which are superior to the traditional Ellman's assay. More significantly, this sensor can also be extended to detect the reversible and irreversible inhibitors of AChE, such as tacrine (IC50 = 23.3 nM) and carbaryl (LOD = 0.8 nM). We firmly believe that this innovative dual-mode nanozyme-involved multienzyme cascade system-based sensing strategy will stimulate further exploration and serve as a versatile and practical tool for biochemical sensing applications.

A Photoelectrochemical Retinomorphic Synapse.

Reproducing human visual functions with artificial devices is a long-standing goal of the neuromorphic domain. However, emulating the chemical language communication of the visual system in fluids remains a grand challenge. Here, a "multi-color" hydrogel-based photoelectrochemical retinomorphic synapse is reported with unique chemical-ionic-electrical signaling in an aqueous electrolyte that enables, e.g., color perception and biomolecule-mediated synaptic plasticity. Based on the specific enzyme-catalyzed chromogenic reactions, three multifunctional colored hydrogels are developed, which can not only synergize with the Bi2S3 photogate to recognize the primary colors but also synergize with a given polymeric channel to promote the long-term memory of the system. A synaptic array is further constructed for sensing color images and biomolecule-coded information communication. Taking advantage of the versatile biochemistry, the biochemical-driven reversible photoelectric response of the cone cell is further mimicked. This work introduces rich chemical designs into retinomorphic devices, providing a perspective for replicating the human visual system in fluids.

Fluorescent and colorimetric dual-mode detection of Cu2+ based on carbon dots.

A fluorescent and colorimetric dual-mode strategy based on carbon dots (CDs) was rationally designed for sensitive determination of Cu2+. Green fluorescent CDs with high absolute quantum yield of 72.9% were synthesized by facile one-step hydrothermal treatment of triethylenetetramine and Rose Bengal. Cu2+ could trigger the oxidative and chromogenic reaction of p-phenylenediamine (PPD) to generate chromogenic PPDox, accompanied by the fluorescence quenching of the CDs. The quenching mechanism was identified as the inner filter effect between PPDox and CDs. Therefore, a colorimetric/fluorescent dual-mode detection method for Cu2+ recognition was constructed. The limits of detection for Cu2+ were 4.14μM and 1.28μM for colorimetric and fluorescent mode, respectively. In addition, this method had achieved satisfactory results in the detection of Cu2+ in real serum samples.

Polyoxometalate-based nanozyme with laccase-mimicking activity for kanamycin detection based on colorimetric assay.

As a kind of aminoglycoside antibiotics, kanamycin (KAN) is widely applied to animal husbandry and aquaculture. However, the abuse of KAN causes the large-scale discharge of it into rivers, lakes and groundwater, which threatens environmental safety and human health. Therefore, it is imperative to develop a method that is applicable to detect KAN in an efficient and accurate way. The colorimetric method based on enzymes provides a feasible solution for the detection of organic pollutants. However, the extensive application of natural enzymes is constrained by high cost and low stability. Herein, a polyoxometalate-based nanozyme, namely [H7SiW9V3O40(DPA)3]·4H2O (SiW9V3/DPA) (DPA = dipyridylamine), is synthesized. As a low-cost nanozyme with high stability compared to natural enzymes, SiW9V3/DPA performs well in laccase-mimicking activity. It can be used to induce chromogenic reaction between 2,4-dichlorophenol (2,4-DP) and 4-aminoantipyrine (4-AP), which generates red products. With the addition of KAN, the color fades. That is to say, KAN can be detected with colorimetric assay in the concentration range 0.1 to 100μM with high selectivity and low limit of detection (LOD) of 6.28μM.Moreover, SiW9V3/DPA is applied to KAN detection in lakeand riverwater and milk with satisfactory results. To sum up, polyoxometalate-based nanozyme is expected to provide a promising solution to the detection of organic pollutants in the aquatic environment.

Understanding Variations in Ferrate Detection through the ABTS Method in the Presence of Electron-Rich Organic Compounds.

The chromogenic reaction between 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and ferrate [Fe(VI)] has long been utilized for Fe(VI) content measurement. However, the presence of electron-rich organic compounds has been found to significantly impact Fe(VI) detection using the ABTS method, leading to relative errors ranging from ∼88 to 100%. Reducing substances consumed ABTS•+ and resulted in underestimated Fe(VI) levels. Moreover, the oxidation of electron-rich organics containing hydroxyl groups by Fe(VI) could generate a phenoxyl radical (Ph•), promoting the transformation of Fe(VI) → Fe(V) → Fe(IV). The in situ formation of Fe(IV) can then contribute to ABTS oxidation, altering the ABTS•+:Fe(VI) stoichiometry from 1:1 to 2:1. To overcome these challenges, we introduced Mn(II) as an activator and 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic agent for Fe(VI) detection. This Mn(II)/TMB method enables rapid completion of the chromogenic reaction within 2 s, with a low detection limit of approximately 4 nM and a wide detection range (0.01-10 μM). Importantly, the Mn(II)/TMB method exhibits superior resistance to reductive interference and effectively eliminates the impact of phenoxyl-radical-mediated intermediate valence iron transfer processes associated with electron-rich organic compounds. Furthermore, this method is resilient to particle interference and demonstrates practical applicability in authentic waters.

A microfluidic chip with integrated plasma separation for sample-to-answer detection of multiple chronic disease biomarkers in whole blood

Point-of-care testing of multiple chronic disease biomarkers is crucial for timely intervention and management of chronic diseases. Here, a “sample-to-answer” microfluidic chip was developed for simultaneous detection of multiple chronic disease biomarkers in whole blood by integrating a plasma separation module. The whole detection process is very convenient, i.e., just add whole blood and get the results. The chip successfully achieved the simultaneous detection of total cholesterol, triglycerides, uric acid, and glucose in undiluted whole blood within 21 min, including 6 min for plasma separation and 15 min for enzymatic chromogenic reactions. Moreover, the sensitivity levels of on-chip detection of chronic disease biomarkers can also meet clinically relevant thresholds. The chip is easy to use and has significant potential to improve home self-management of chronic diseases and enhance healthcare outcomes.

Characterization, Molecular Mechanism of Prochloraz-Resistance in Fusarium fujikuroi and Development of Loop-Mediated Isothermal Amplification Rapid Detection Technique Based on the S312T Genotype of Resistances.

Rice bakanae disease (RBD) is a typical seed-borne fungal disease caused by Fusarium fujikuroi. Prochloraz is a sterol demethylation inhibitor, which is among the most important classes of active ingredients for the management of RBD. In 2022, the total resistance frequency of F. fujikuroi to prochloraz in Zhejiang Province was 62.67%. The fitness of the prochloraz-resistant population was lower than that of the susceptible population, but its pathogenicity was slightly stronger. The S312T and F511S double mutations of Ffcyp51b were detected in the resistant isolates. Loop-mediated isothermal amplification (LAMP) technology based on S312T was established to rapidly determine prochloraz resistance in F. fujikuroi. LAMP primer mismatch design was performed based on the cyp51b gene, and 100-300 bp sequences containing a mutation at codon 312 were amplified. In a 25 µL reaction tube, 1 pg/µL DNA of F. fujikuroi could be detected. The detection limit for the frequency of prochloraz resistance was 0.498% using this method. We performed LAMP detection on rice seedlings inoculated with prochloraz-sensitive and -resistant isolates and treated them with prochloraz. Prochloraz demonstrated good control in rice seedlings. A chromogenic reaction was observed in seedlings treated with prochloraz-resistant isolates, and the results were verified using electrophoresis. It has been demonstrated that LAMP technology based on the S312T genotype can quickly and specifically detect prochloraz-resistant isolates in rice seedlings.

Enhanced oxidoreductase activity of diatom frustule supported Fe3O4 for sensitive colorimetric detection of Cr(VI)

Given Cr(VI) is a ubiquitous water pollutant posing significant public health risks, there is a need for an inexpensive and easy-to-use detection tool. Herein, a diatom frustule-supported Fe3O4 (DF-Fe3O4) with enhanced oxidoreductase mimetic activity is reported for direct colorimetric detection of Cr(VI). Unlike the peroxidase nanozymes which are often reported for colorimetric detection, DF-Fe3O4 triggered a chromogenic redox reaction between TMB and Cr(VI) without requiring H2O2. This enables direct redox reactions while circumventing potential interferences associated with the use of H2O2. DF-Fe3O4 was synthesized with a coprecipitation method and subsequently characterized by SEM, XRD, and XPS techniques, revealing the distribution of Fe3O4 NPs on the frustule matrix. The frustule obtained from Nitzschia sp. of a sediment sample rendered a robust catalytic support enhancing the oxidoreductase activity of pristine Fe3O4 NPs by 20.8 %. Further, the nanozyme maintains 73 % of its activity even at 95 °C while losing only 33 % of its activity after one month of storage. The oxidoreductase mimetic activity was evaluated using the chromogenic redox reaction between TMB and Cr(VI) which rapidly forms a blue color (λmax= 654 nm), where its intensity forms the basis of the colorimetric detection. With a Km value of 0.058 mM, the nanozyme was able to selectively detect Cr(VI) down to 0.21 µM with a linear range between 0.1–500 µM. Recoveries from spiked wastewater samples were between 91.14–102.20 %. The obtained analytical figures of merits demonstrated the applicability of the developed sensor for Cr (VI) analysis devoid of complex instrumentation in the established analytical methods.

An ultrasensitive dual-mode stagey for 17β-estradiol assay: Photoelectrochemical and colorimetric biosensor based on a WSe2/TiO2-modified electrode coupled with nucleic acid amplification

BackgroundThe abuse of 17β-estradiol(E2) has aroused wide concern in environmental and biomedical fields, which severely affects the endocrine function of human and animals. Therefore, an ultrasensitive and accurate assay of E2 is critically important. Traditional chromatography or immunoassay techniques exhibited good sensitivity and selectivity, but expensive instruments and antibodies may pose cost and stability issues, as well as difficulties in meeting on-site detection requirements. Ultrasensitive, reliable, and on-site detection of E2 at trace level remains a challenge. Hence, developing a simple, ultrasensitive assay to simultaneously achieve accurate detection and rapid visual analysis of E2 is extremely crucial. ResultsWe developed a versatile dual-mode photoelectrochemical (PEC) and colorimetric biosensor based on isothermal nucleic acid amplification strategy for the ultrasensitive and accurate detection of E2. The method modified titanium dioxide (TiO2) with tungsten selenide (WSe2) nanoflowers to synthesize WSe2/TiO2 heterostructures as a substrate for signal amplification and nanoprobe modification. Isothermal nucleic acid amplification strategy has been proven to be a powerful tool for strong signal amplification. The presence of a target triggered the nucleic acid amplification reaction, and produced a large amount of tDNA that competed with G-quadruplex immobilized on the electrode surface. The remaining G-quadruplex/hemin catalyzed the 4-chloro-1-naphthol (4-CN) to form biocatalytic precipitation (BCP) and ABTS-H2O2 chromogenic reaction, thus, the dual-mode platform was capable of achieving PEC-colorimetric ultrasensitive detection based on the catalytic activity of G-quadruplex/hemin DNAzyme. Within optimal conditions, the dual-mode biosensor exhibited a remarkable detection limit as low as 0.026 pM. SignificanceBenefiting from the superior performance of WSe2/TiO2 and the power signal amplification of isothermal nucleic acid amplification strategy, this aptasensor achieved the ultrasensitive detection of E2. The independent transmission paths of photoelectrochemical and colorimetric provide mutual support and flexible switching, significantly enhancing the overall sensitivity and accuracy of the detection strategy, which can meet the needs for E2 precise quantification and rapid on-site detection.

Environmental responsive peroxidase-like activity of MoS2@halloysite nanotubes mediated by piezoelectric effect

Nanozymes, as a class of synthetic enzymes, have the characteristics of abundant raw materials and powerful environmental adaptability, potentially serving as substitutes for natural enzymes. Herein, the MoS2 nanosheets were anchored on the surface of alkali activated halloysite nanotubes by utilizing a facile hydrothermal process, resulting in the formation of MoS2@halloysite (MoS2@HNTs) core-shell nanocomposites. The catalytic effect of material on peroxidase under the mechanical stress of applied ultrasonic vibration was systematically investigated with 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate for chromogenic reaction. The results demonstrated that the established piezoelectric polarization effect generated by MoS2 with asymmetric crystal structure under mechanical force can promote the in-situ coloration of TMB. Concretely, MoS2@HNTs possessing higher Michaels constant (3.42 mmol L-1) and reaction velocity (3.16 × 10–6 mol L-1 min-1) exhibited enhanced peroxidase-like activity compared to pristine MoS2 microspheres. This may be attributed to the fact that halloysite dispersed the MoS2 nanosheets, exposing more reactive sites, and the nanocomposites produced more pronounced structural deformation under mechanical stress. The detailed experiments and theoretical calculation have elucidated the structure-activity relationship and microscopic mechanism among the microstructures, piezoelectric polarization effects and peroxidase catalytic effects of materials. This work provides an advanced prototype for the research of environmental responsive enzyme-like catalytic effects of mineral-based nanozymes with the regulation of external environmental factors.

Integration of Myrica rubra-based N-doped carbon dots with Fe3S4 as excellent peroxidase mimics for colorimetric assay and smartphone-based intelligent sensing of p-aminophenol in waters.

To realize the reutilization of waste Myrica rubra in the analytical field, we synthesized Myrica rubra-based N-doped carbon dots (MN-CDs) and further anchored them onto the surface of Fe3S4 to fabricate Fe3S4@MN-CD nanocomposites. The as-fabricated nanocomposites possessed higher peroxidase-mimetic activity than its two precursors, resulting from the synergistic effect between them, and could catalyze colorless 3,3',5,5'-tetramethylbenzidine (TMB) into deep blue oxTMB with a strong 652-nm absorption. Under optimized conditions (initial solution pH, 3.5; incubation temperature, 35 ℃; Fe3S4@MN-CD concentration, 50µg mL-1, and 652-nm absorption), Fe3S4@MN-CDs were employed for colorimetric assay of p-aminophenol (p-AP) with wide linear range (LR, 2.9-100 µM), low detection limit (LOD, 0.87 µM), and satisfactory recoveries (86.3-105%) in environmental waters. Encouragingly, this colorimetric assay provided the relative accuracy of 97.0-99.4% as compared withconventional HPLC-UV detection. A portable smartphone-based colorimetric application was developed by combining the Fe3S4@MN-CD-based visually chromogenic reaction with a "Thing Identify" APP software. Besides, we engineered an image-capturing device feasible for field use, in which the internal-compact sealing prevented external light source from entering photography chamber, thereby reducing light interference, and also the bottom light source enhanced the intensity of blue imaging. This colorimetric platform exhibited satisfactory LR (1-500 µM), low LOD (0.3 µM), and fortification recoveries (86.6-99.6%). In the chromogenic reaction catalyzed by Fe3S4@MN-CDs, ·O2- played a key role in concomitant with the participation of •OH and h+. Both the colorimetric assay and smartphone-based intelligent sensing show great promising in on-site monitoring of p-AP under field conditions.

Carbon/ruthenium hybrid nanozymes for efficient β-glucosidase sensing

Highly efficient nanozymes are useful for constructing sensors with exceptional performance. Herein, carbon nanotubes loaded with ruthenium nanoclusters (Ru/CNTs) were successfully prepared through a straightforward ambient chelating reduction synthetic method. The strong d-π interactions between CNTs and metallic Ru facilitated the nucleation, dispersion, and enduring stability of Ru nanoclusters. Benefiting from the robust peroxidase-like activity and recyclability of Ru/CNTs, an accurate colorimetric sensing platform was established for efficient β-glucosidase (BG) sensing. Ru/CNTs efficiently catalyzed H2O2 to generate reactive oxygen species (ROS, O2•− and 1O2), initiating the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB). However, the above chromogenic reaction was suppressed in the presence of HQ due to its inherent reducibility. Using phenolic β-arbutin (BA) as substrate, BG catalyzed the hydrolysis of BA, releasing HQ. The proposed Ru/CNTs-based sensing system, involving the implementation of two-step catalytic reactions and concurrently possessing the stability and high specificity of enzymes, significantly enhanced the system’s selectivity and sensitivity. As expected, this colorimetric sensor exhibited remarkable sensitivity (limit of detection, LOD 0.472 U L−1) with exceptional accuracy (recoveries, 94.84–111.32 %; RSD, 0.89–3.07 %). Overall, the proposed cascade catalysis strategy significantly enhanced the stability and sensitivity of the sensor, paving the way for its practical application in the fields of food and biology.

Green and Versatile High-Throughput Microwell Oxidation-Based Spectrophotometric Methods for Determination of Galidesivir in Capsules.

Galidesivir (GDV) is a promising new antiviral drug for the potent and safe treatment of a broad spectrum of viral diseases, including COVID-19. In the literature, no analytical method exists for the determination of GDV in bulk and dosage form. The aim of this study was the development of versatile green and simple microwell spectrophotometric methods (MW-SPMs) for the determination of GDV in its bulk form and capsules. Three MW-SPMs were developed involving the oxidation of GDV by ammonium metavanadate (AMV), chromium trioxide (CTO), and potassium iodate (PIO) in an acid medium. The reactions were carried out in 96-well plates at room temperature and the absorbances of chromogenic reaction products were measured by an absorbance microplate reader at 780, 595, and 475 nm for AMV, CTO, and PIO, respectively. Variables influencing the reactions were carefully investigated and optimized. Linear relations with excellent correlation coefficients (0.9991-0.9997) were found between the absorbances and GDV concentrations in the range of 25-500 µg/mL. The LODs were ≥8.3 µg/mL. The accuracy and precision of the three MW-SPMs were confirmed by recovery and replicate analysis, respectively. The recovery values were 98.6-101.2% and the RSDs were ≤1.02%. The proposed MW-SPMs were successfully applied to the analysis of GDV in bulk drug and capsules with high accuracy and precision. The greenness of the MW-SPMs was confirmed by three comprehensive metric tools. The proposed MW-SPMs combined the inherent advantages of microwell-based analysis and the use of common laboratory reagents for the reactions involved. These advantages include high-throughput, ready automation, reduced sample/reagent volume, precise measurements, and versatility. The advantages of the use of common laboratory reagents include availability, consistency, compatibility, safety, and cost-effectiveness. Overall, the proposed MW-SPMs are versatile valuable tools for the quantitation of GDV during its pharmaceutical manufacturing.

Droplet array with microfluidic concentration gradient (DA-MCG) for 2-dimensional reaction condition screening

Droplet microfluidic technology can use each microdroplet as a microreactor, which has the advantages of low reagent dosage, less cross contamination, and fast reaction time. Combining concentration gradient generation with droplet formation and capture to form a two-dimensional reaction condition screening platform (including reactant concentration and reaction time) is expected to broaden the application range of microfluidic screening. In this work, a microfluidic chip that can dynamically generate and capture microdroplets and form static microdroplet array was designed and fabricated. An optimized Christmas tree structure by adjusting the horizontal channel length ratio was used to generate a chemical concentration gradient while obtaining a uniform outlet flow rate, forming a droplet array with different concentrations. The performance of droplet array with microfluidic concentration gradient (DA-MCG) was verified using sodium fluorescein as a model reagent. The chromogenic reaction of NaOH and phenolphthalein, and luminol chemiluminescence reaction were used to verify the two-dimensional screening ability of DA-MCG. The results indicated that the DA-MCG has the potential to be applied in the field of multi-dimensional drug screening.