Rapid detection of bacteria and sensitive detection of bacteria are like two sides of a coin, making it difficult to achieve both at the same time. This study designed a colorimetric-photothermal dual-mode vertical flow assay based on 4-mercaptophenylboronic acid (MPBA)-functionalized Cu2-xSe-Au nanozyme (Cu2-xSe-Au@MPBA). The Cu2-xSe-Au@MPBA probes were synthesized through in situ reduction. These probes can bind with target bacteria and the antibodies immobilized on the filter membrane, thereby forming a "nanomaterial-bacteria-antibody" sandwich structure. The dual-mode signals come from the peroxidase-like activity and photothermal properties of the Cu2-xSe-Au@MPBA nanozyme. Both colorimetric and photothermal modes can be completed in 60 min. This assay demonstrates low detection limits of 26.34 CFU mL(-)(1) in colorimetric mode and 1.91 CFU mL(-)(1) in photothermal mode. Real sample analysis by this assay showed excellent anti-interference capability and reliable recovery rates, which demonstrate a significant potential for applications in food safety monitoring and bioanalysis.

A "on-off-on" photocatalytic fuel cell (PFC) aptasensor was developed for the portable detection of zearalenone (ZEN) and T-2 toxin via a digital multimeter (DMM). The n-type BiVO4/FeVO4 and p-type Cu2O/carbon spheres (Cu2O/CSs) were prepared as photoanode and photocathode materials, respectively. ZEN aptamer was modified on the photoanode. When the target ZEN was added, a "signal-off" detection signal was obtained due to the spatial hindrance effect resulting from the binding of ZEN aptamer to the target ZEN. Subsequently, methylene blue (MB) was loaded in the pore of UIO-66-NH2 and T-2 aptamer was used to seal the pore of UIO-66-NH2 for effectively preventing MB leakage, which was acted as the signal probe (MB@UIO-66-NH2/Apt). In the presence of target T-2, the specific recognition interaction between T-2 aptamer and T-2 was triggered, resulting in releasing a large amount of MB molecules from UIO-66-NH2. MB, as an electroactive substance, was reduced to leuco-methylene blue (LMB) by electrons generated at the photocathode under light excitation, accelerating electron transfer for signal amplification and providing a "signal-on" response for T-2 toxin detection. The incorporation of a capacitor into a DMM was used as a portable device for the direct signal readout as well as the amplification of the electrical signal. The detection limits for ZEN and T-2 were 0.31 pg mL- 1 and 0.19 pg mL-1, respectively. Compared to conventional PFC sensors that rely on electrochemical workstations and single-target designs, this work presents a portable, self-powered, and dual-target detection platform with a dual-signal-mode mechanism. The sensor integrates optical excitation, electrochemical conversion, and capacitive signal storage, providing a versatile blueprint for developing next-generation, self-powered devices for food safety and environmental monitoring.

Hydrogen-bonded organic frameworks (HOFs) are promising porous crystalline materials for sensing, but their weak intrinsic enzyme-like activity limits nanozyme applications. Herein, a Ru-functionalized HOF material (Ru-HOFs) was fabricated through Ru–N coordination. In this material, the HOFs framework anchors and stabilizes the Ru sites. The resulting Ru-HOFs exhibited enhanced peroxidase-like activity toward hydrogen peroxide (H2O2)-mediated oxidation of o-phenylenediamine (OPD), with favorable catalytic stability and substrate affinity. Density functional theory (DFT) calculations suggest that Ru-N coordination modulates the local electronic structure and provides a more favorable free-energy profile for H2O2 adsorption and subsequent activation. By coupling Ru-HOFs with D-amino acid oxidase (DAAO), a cascade colorimetric platform was developed for salivary D-proline (D-Pro) and D-alanine (D-Ala), two reported gastric cancer (GC)-related D-amino acids (DAAs). Under individual assay conditions, the platform showed linear ranges of 2–150 µmol L⁻¹ for D-Pro and 5–100 µmol L⁻¹ for D-Ala, with limits of detection of 0.6112 and 2.299 µmol L⁻¹, respectively. Smartphone-based red–green–blue (RGB) analysis enabled visual readout and quantitative determination under controlled conditions. Spiked saliva tests showed satisfactory recoveries, demonstrating the applicability of the proposed assay to saliva matrices for the analysis of reported GC-related salivary DAAs. This work also provides a useful strategy for constructing coordination-regulated HOF-based nanozymes with improved catalytic performance for colorimetric sensing applications.

Foodborne bacterial infection causes serious harm to human health and brings a huge economic burden. Escherichia coli (E. coli) O157:H7 is a common foodborne pathogen. Establishing a simple and portable multifunctional platform for E. coli O157:H7 detection is important. Based on the glycolipid interaction between Cu2-xSe nanoparticles functionalized with 4-mercaptophenylboronic acid (Cu2-xSe@MPBA) and bacterial cells, a multifunctional immunomagnetic separation integrated platform independent of signal probe antibodies was constructed in this study to realize label-free colorimetric biosensing of E. coli O157:H7. The signal probe (Cu2-xSe@MPBA) is easy to prepare without the participation of an antibody or aptamer. The immunomagnetic platform reduced sample background interference for colorimetric detection and improved the sensitivity. Meanwhile, we developed a mobile application for rapid data analysis, which can quickly realize high-sensitivity high-throughput detection of point-of-care testing (POCT) for E. coli O157:H7 by combining smartphones as analyzers. Under optimal reaction conditions, the results showed that the Delta B/ (R + G) values showed a good linear relationship with the concentration of E. coli O157:H7 in the range of 2.08 x 10(3)-2.08 x 10(8) CFU mL(-1), and the detection limit of this method was 6.83 x 10(2) CFU mL(-1). Furthermore, the platform was successfully applied for the detection of E. coli O157:H7 in water and food samples, showing great advantages in the rapid detection of pathogens and providing a promising biosensor for food safety.

BACKGROUND:Acid phosphatase (ACP) is closely associated with various diseases, rendering it a vital clinical diagnostic marker. Therefore, it is significant to establish a detection method for ACP. Enzyme cascade reaction has been a frequently-used method for enzyme detection. Hydrogen-bonded organic frameworks (HOFs) are a class of porous materials which have shown several advantages in the field of separation, catalysis and biological enzyme protection. However, the design and investigation of HOFs-mediated multifunctional nanozymes for applications in biosensing based on enzyme cascade reactions remain ongoing. RESULTS:A colorimetric and ratio-fluorescence dual-mode assay for multicolor detection of ACP based on iron ions modified HOFs nanozymes (HOFs@Fe) was constructed. HOFs@Fe exhibits excellent peroxidase-like activity, capable of catalyzing hydrogen peroxide to oxidize o-phenylenediamine into 2,3-diaminophenazine (DAP). The addition of sodium pyrophosphate (PPi) can significantly inhibit the catalytic activity of HOFs@Fe and enhance the fluorescence at 440 nm. Based on the fluorescence properties of HOFs@Fe and DAP, a colorimetric and ratio-fluorescence dual-mode assay was developed for ACP detection. In the fluorescence mode, the detection limit is 0.038 U L-1; in the colorimetric mode, the detection limit is 0.99 U L-1. This method has been applied for ACP detection in human serum. Furthermore, owing to the multi-color of fluorescence mode, a smartphone sensing platform was combined to achieve a point-of-care testing of ACP. SIGNIFICANCE:This method features simplified procedures, low material synthesis complexity, no requirement for fluorescent labeling, and low detection limits for ACP detection. Furthermore, this work provides a bright avenue for the synthesis of multifunctional HOF-based nanozyme, and offers new opportunities for the development of visual biosensors in the field of biosensing.

To meet the increasing demands for highly active and stable nanozymes for bioanalysis, Pt nanoparticles (NPs) were successfully supported on the surface of hydrogen-bonded organic frameworks (Pt/HOFs) to obtain a stable, multifunctional and highly active nanozyme for the colorimetric detection of alkaline phosphatase (ALP). Through a redox reaction, Pt precursors are reduced to ultrasmall Pt NPs that are loaded on HOFs. The Pt/HOFs nanozyme showed excellent oxidase-like, peroxidase-like and some catalase-like activity. To avoid the signal instability caused by H2O2 decomposition, the oxidase-like activity of Pt/HOFs was applied for the detection of ALP using 3,3', 5,5 '-tetramethylbenzidine (TMB) as a chromogenic substrate. When the substrate L-ascorbic acid 2-phosphate (AAP) is present, ALP can catalyze AAP to produce strongly reductive ascorbic acid (AA). AA can reduce the oxidation product of TMB. Therefore, a colorimetric sensing strategy for ALP detection was constructed. The linear range of the strategy was from 0.5 to 8 mU mL-1, and the detection limit was 0.46 mU mL-1. Finally, the strategy was successfully applied to the detection of ALP in human serum, which provided a reliable strategy for the colorimetric detection of clinical ALP. This study not only presents a simple approach to maintain the high activity of nanoparticle-based nanozymes, but also expands the application of multifunctional HOF-based materials for future applications.

Strong and persistent chemiluminescence (CL) is essential for enhancing the detection accuracy and reproducibility of CL-based analytical methods. In this study, we explored the synergistic effects of amino groups present on the surface of hydrogen-bonded organic framework (HOF-PyTTA, where PyTTA is denoted as 4,4',4″,4‴-(pyrene-1,3,6,8-tetrayl)tetraaniline) materials and N-(4-aminobutyl-N-ethylisoluminol) (ABEI) for reducing gold nanoparticles (AuNPs) on the surface of HOFs. Additionally, we utilized the substantial specific surface area and abundant amino groups of HOFs to sequester Co2+ ions, resulting in the synthesis of HAACo material. The resulting HAACo exhibited remarkable peroxidase, oxidase, and catalase mimetic activities, enabling the luminol-H2O2 chemiluminescence system to maintain a glow-type CL phenomenon for more than 1 h. Subsequently, we developed a CL point-of-care testing (POCT) sensor that integrated the CL characteristics of HAACo with smartphone technology and 3D printing for the determination of acetylcholinesterase (AChE) activity in serum samples, as well as the screening for AChE inhibitors. The sensor demonstrated a linear detection range for AChE activity from 0.001 to 40 mU mL-1, with a detection limit of 0.00057 mU mL-1. The calculated IC50 for the AChE inhibitor tacrine was found to be 21.9 nmol L-1, indicating good selectivity and stability of the sensor. This work not only expands the applications of glow-type CL in biosensing but also enriches the utilization of HOF materials in analytical chemistry, paving the way for the development of multifunctional HOF-based materials for future applications.

Malathion plays an important role in agricultural production, and the accurate detection of malathion residues is essential to ensure food safety. A novel enzyme-free sensing method was proposed by employing bimetallic magnetic nanozymes for both colorimetric quantification and multicolor semi-quantitative detection of malathion. The nanozyme exhibits peroxidase-like activity, catalyzing H2O2-mediated oxidation of 3,3',5,5'-Tetramethylbenzidine dihydrochloride (TMB). Malathion inhibits this activity via ZrOP coordination, reducing oxidized TMB (oxTMB) generation. Under acidic conditions, oxTMB is further converted to TMB2+, which etches gold nanorods, inducing aspect-ratio variations accompanied by distinct multicolor changes. This method demonstrates low detection limits of 0.68 ng/mL. It does not require biological enzymes and can semi-quantify the malathion concentration through color changes. Thus, it can achieve convenient and accurate quantitative analysis without instruments, meeting on-site detection requirements. This work contributes to food safety and the development of efficient and reliable methods for malathion detection.

In this study, Ag-CdIn2S4 was selected as a photosensitive material and combined with the zeolite imidazole frame-90 encapsulated methylene blue (ZIF-90@MB) to establish a controlled release system. On that basis, a self-powered photoelectrochemical (PEC) aptasensor was constructed based on target responses to realize the highly sensitive detection of prostate-specific antigen (PSA). The self-powered sensing method was employed to effectively avoid interference from other oxidizing/reducing substances in the system and improve the accuracy of the detection method. The band gap of CdIn2S4 was adjusted by Ag doping, and the visible light absorption capacity and photoelectric conversion efficiency of the material were improved by the local surface plasmon resonance (LSPR) effect of metal Ag. The ZIF-90 porous material was used as a carrier, the MB photosensitizer as a signal molecule was loaded in the ZIF-90 pore channel. The PSA aptamer (PApt) was attached to the ZIF90@MB surface to form a simple biological gate. In the presence of the PSA, the recognition interaction between PApt and PSA made the biological gate open, then many MB molecules were released from ZIF-90 and enhanced the photocurrent signal. Under the optimal experimental conditions, the linear range of the sensor was 0.005 similar to 50 ng mL(-1), and the detection limit was 2.35 pg mL(-1). The accurate determination of PSA in human serum was achieved, which provided a novel sensing strategy for the early diagnosis of clinical biomarkers.

Hydrogen-bonded organic frameworks (HOFs) have drawn great attention in recent years; however, few reports show the applications of HOFs in biosensing. Abnormal concentration of glutathione (GSH) usually relates to some diseases, thus quantifying the amount of GSH is of great importance. Fluorescence method has the advantages of high sensitivity, simplicity, and low cost, however, traditional fluorescent sensors for GSH need complex synthesis procedures for fluorescent probes. Herein, a simple off-on fluorescence sensor based on hydrogen-bonded organic frameworks (HOF-PyTTA) was constructed. Firstly, the fluorescence of HOF-PyTTA was quenched by Fe3+, and after the addition of GSH, Fe3+ reacted with GSH to restore the fluorescence intensity of HOF-PyTTA. Based on the above principles, a simple HOF-PyTTA/Fe3+ mixed system was constructed and applied to detect GSH. The concentration of GSH showed a good linear relationship with the fluorescent intensity of HOF-PyTTA/Fe3+ in the range of 0-0.40 mmol/L, and the limit of detection was 8.8 mu mol/L. This method was applied to the determination of GSH in human serum samples. The recoveries were in the range of 95.9-102.5 %, and the RSD was 0.1 % -0.64 %. The proposed method based on the off-on fluorescence change of HOF-PyTTA shows a simple operation and a rapid response within 10 min. It not only broadened the application of hydrogen-bonded organic frameworks but also indicated a great potential of HOF as an efficient fluorescence probe for biosensing.

An ultrasensitive photothermal assay was designed for point-of-care testing (POCT) of tumor markers based on a filter membrane. Firstly, Cu2-xSe was successfully encapsulated in liposome spheres with biotin on the surface and connected to carcinoembryonic antigen (CEA) aptamer with 3'end modified biotin by streptavidin. Secondly, the CEA antibody was successfully modified on the surface of the nitrocellulose membrane through simple incubation. Finally, the assay process was completed using a disposable syringe, and the temperature was recorded using a handheld infrared temperature detector. In the range 0–50 ng mL−1, the temperature change of the nitrocellulose membrane has a strong linear relationship with CEA concentration, and the detection limit is 0.097 ng mL−1. It is worth noting that the entire testing process can be easily performed in 10 min, much shorter than traditional clinical methods. In addition, this method was successfully applied to the quantitative determination of CEA levels in human serum samples with a recovery of 96.2–103.3

A novel split-type photoelectrochemical (PEC) biosensor was constructed for the sensitive detection of carcinoembryonic antigen (CEA) based on the Ag+-liposome (ALL) signal amplification strategy and Bi2S3@BiOI heterojunction as the substrate material. The split-type sensing mode effectively avoids the complex fixation of biomolecules on the electrode surface and preserves the activity of biomolecules. The sandwich complex was formed between CEA and aptamer-anchored streptavidin-functionalized magnetic beads (SMB-Apt) and ALL-labeled aptamer (ALL-Apt). After the methanol was added, a large amount of Ag+ was released from the liposome. The released Ag+ was transferred to the Bi2S3@BiOI modified electrode surface for incubation and then soaked in Na2S solution to form a narrow band gap photosensitive material Ag2S on the electrode surface. Bi2S3@BiOI/Ag2S ternary heterojunction in situ was formed due to the band gap matching relationship between Ag2S and the Bi2S3@BiOI heterojunction, which effectively expanded the light absorption range and enhanced the photocurrent signal. Under the optimal experimental conditions, the constructed PEC sensing platform exhibited good analytical performance for CEA with a linear range of 0.005 similar to 50 ng mL(-1) and a detection limit of 1.21 pg mL(-1). Additionally, the PEC sensor had good selectivity, reproducibility, and stability, which provided a new research idea for the detection of clinical tumor biomarkers.

An intelligent nanodrug delivery system (Cu/ZIF-8@GOx-DOX@HA, hereafter CZGDH) consisting of Cu-doped zeolite imidazolate framework-8 (Cu/ZIF-8, hereafter CZ), glucose oxidase (GOx), doxorubicin (DOX), and hyaluronic acid (HA) was established for targeted drug delivery and synergistic therapy of tumors. The CZGDH specifically entered tumor cells through the targeting effect of HA and exhibited acidity-triggered biodegradation for subsequent release of GOx, DOX, and Cu2+ in the tumor microenvironment (TME). The GOx oxidized the glucose (Glu) in tumor cells to produce H2O2 and gluconic acid for starvation therapy (ST). The DOX entered the intratumoral cell nucleus for chemotherapy (CT). The released Cu2+ consumed the overexpressed glutathione (GSH) in tumor cells to produce Cu+. The generated Cu+ and H2O2 triggered the Fenton-like reaction to generate toxic hydroxyl radicals (·OH), which disrupted the redox balance of tumor cells and effectively killed tumor cells for chemodynamic therapy (CDT). Therefore, synergistic multimodal tumor treatment via TME-activated cascade reaction was achieved. The nanodrug delivery system has a high drug loading rate (48.3 wt

Escherichia coli (E. coli) O157:H7 is a common foodborne pathogen which can cause serious harm. It is particularly important to establish a simple and portable method to achieve on-site pathogen detection. In this study, a capture-antibody-independent lateral flow immunoassay (LFIA) was constructed based on Cu2-xSe nanocrystals (Cu2-xSe NCs) for rapid detection of E. coli O157:H7. Cu2-xSe NCs can not only be regarded as the "nano-antibody" for the recognition of E. coli O157:H7 through electrostatic adsorption, but also as nanozymes that show good peroxidase-like catalytic activity. The formed compound of E. coli O157:H7 and Cu2-xSe NCs would be captured by a detection antibody on the T line due to the specific recognition of the antibody and E. coli O157:H7. Then, Cu2-xSe NCs could catalyze the oxidation of TMB by H2O2 to generate oxTMB, thereby generating blue bands. Meanwhile, we developed a mobile app for rapid data analysis. Under the optimal reaction conditions, E. coli O157:H7 could be detected within 70 min. The detection limit of this method was 2.65 × 105 CFU mL-1 with good specificity and stability. Additionally, it could achieve on-site rapid detection of E. coli O157:H7 in environmental water samples, providing a promising biosensor for portable pathogen detection.

Conventional lateral flow assays based on colorimetry and fluorescence still have shortages in sensitivity and selectivity due to the severe background interference from complex human fluid sample matrices. In this work, Cu2-xAgxS nanocrystals with high photothermal conversion efficiency and good peroxidase-like activity were synthesized and applied in the construction of a dual-mode near-infrared-photothermal/chemiluminescence (CL) vertical flow assay of carcinoembryonic antigen (CEA). These two-mode principles showed nearly zero background and the synthesized Cu2-xAgxS exhibited a high photothermal conversion efficiency of 75.23%, enabling the luminol-H2O2 CL system to have over 4 min of chemiluminescence. By combining filter membrane enrichment, Cu2-xAgxS@liposome encapsulation amplification, and nanozyme catalysis, a dual-mode photothermal/CL portable assay was constructed for sensitive and accurate detection of CEA in serum, with linear ranges of 0.02-40 and 0.001-30 ng mL-1, and detection limits of 0.0023 and 0.00029 ng mL-1, respectively. Furthermore, a smartphone application and a 3D printing device were combined for point-of-care testing. This assay can be completed within 20 min, with simple operation and no need for large instruments. It exhibited good sensitivity, selectivity, and stability, and is expected to be used in early diagnosis and prevention of relevant diseases in resource-limited areas.

A multicolor visual method for the detection of hydrogen peroxide (H2O2) was reported based on the iodide-mediated surface etching of gold nanostar (AuNS). First, AuNS was prepared by a seed-mediated method in a HEPES buffer. AuNS shows two different LSPR absorbance bands at 736 nm and 550 nm, respectively. Multicolor was generated by iodide-mediated surface etching of AuNS in the presence of H2O2. Under the optimized conditions, the absorption peak Δλ had a good linear relationship with the concentration of H2O2 with a linear range from 0.67~66.67 μmol L−1, and the detection limit is 0.44 μmol L−1. It can be used to detect residual H2O2 in tap water samples. This method offered a promising visual method for point-of-care testing of H2O2-related biomarkers.

Information-carrying capacity has become an important factor in the development of encryption and anti-counterfeiting. Herein, a hydrogen-bonded organic framework (HOF-PyTTA) was developed as novel anti-counterfeiting ink without rare metals and a smartphone-based APP was written for encryption and anti-counterfeiting. We found that the fluorescence of HOF-PyTTA can be quenched by Fe3+ ions and recovered by the addition of ascorbic acid. And the fluorescence of HOF-PyTTA can be enhanced by the increasing concentrations of ethanol. Based on these stimulus-response properties, four anti-counterfeiting models with gradually increased security were studied. Mode one was printed by HOFs ink and decrypted by UV light. Mode two was based on HOF-PyTTA and CsPbBr3 inks (or HOF-PyTTA-Fe3+) which are used to separately print the genuine and pirated information. A decryption reagent was applied to get the genuine information. Furthermore, we successfully construct a dynamic information encryption anti-counterfeiting model using a fluorescence array in combination with an information encryption anti-counterfeiting APP. The circular array is printed by several concentrations of HOF-PyTTA ink and different RGB thresholds are set with the help of the information encryption anti-counterfeiting APP, to obtain distinct encrypted anti-counterfeiting information, thus accomplishing a high information-carrying capacity.

A novel probe for bacteria was simply synthesized through the solvent-induced co-assembly of bacitracin (AMP) and thymolphthalein (TP) without complicated modification. Combining with aptamer-Fe3O4, AMP/TP nanoparticles were used for the colorimetric detection of Escherichia coli with good sensitivity through the NaOH-triggered blue color and a smartphone-based App.

Alpha fetoprotein (AFP) is an embryonic glycoprotein that is produced by hepatocytes and soft yellow sacs, which is closely related to liver cell proliferation, as well as the development of cirrhosis, chronic hepatitis and other diseases. Thus, AFP has been widely used as an important tumor marker in the basic research and clinical diagnosis of diseases such as early-stage liver cancer, endodermal sinus tumors and germ cell tumors. In this study, we developed a near-infrared (NIR) fluorescent carbon quantum dots by microwave synthesis, and con-structed a turn-on fluorescent nanosensor by unique modifications. This nanosensor not only has specific response to AFP, but also good biocompatibility and high photostability. The results show that the proposed NIR nanosensor has very high sensitivity, and its detection limit is 3.0 pg/mL for AFP. Thus, it was used for the accurate quantification of AFP in human serum and the imaging of AFP in vitro and in vivo. Therefore, the diagnosis of early-stage liver cancer can be achieved by using proposed method.

A colorimetric method for the catalysis hydrolysis of profenofos (C11H15BrClO3PS) was designed based on Zn-ZrMOF. Zn-ZrMOF has the catalytic activity of organophosphorus hydrolase and contains Lewis acid-base cat-alytic sites, which can catalyze the cleavage of P-O bond of profenofos to obtain hydrolysate (4-bromo-2-chlorophenol). As a phenolic substance, 4-bromo-2-chlorophenol can react with the chromogenic agent 4-amino-antipyrine (4-AAP) and produce a pink product (4-((3-chloro-4-oxocyclohexa-2,5-dien-1-ylidene)amino)- 1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one) in the presence of oxidizer K3[Fe(CN)6] under the weak alkalinity. The pink product has a strong UV absorption peak at 508 nm. The solution color gradually changed from colorless to pink with the increase of the concentration of profenofos. The concentration of profenofos could be semi-quantitatively analyzed by naked eye. The linear range of this method was 0.01-1000 mu g mL-1, and the detection limit was 6.33 x 10-3 mu g mL-1. Additionally, the method has good selectivity and accuracy for the determination of profenofos. This study provides a feasible strategy for the design of a metal-organic framework material with organophosphorus hydrolase-like catalytic activity for the determination of profenofos in vegetables.