Phages modified hydrogel pellet assembled in 3D printed both-in-one device for detecting Pseudomonas aeruginosa based on colorimetric and pressure readout modes.

Pseudomonas aeruginosa (P. aeruginosa) with noticeable drug-resistance profile is one of the most pernicious pathogens that attracts major public health concerns. Herein, a 3D printed device combined with hydrogel pellet modified with phages was designed for point-of-care testing (POCT) of this pathogen with both colorimetric and pressure readout modes. A P. aeruginosa phage belonging to the family of Podoviridae was isolated from river water and noted as vB_PaeP-JZ1 (JZ1). Due to its host specificity, phage JZ1 was used as a recognizing agent for modifying the hydrogel pellet, and the modified hydrogel pellet was assembled into the 3D printed device to act as the sensing interface. Polymyxin B (PMB) was tagged with Pd@Pt core-shell nanodendrites (Pd@PtNDs) showing excellent peroxidase-like activity to act as the colorimetric and pressure signal tracer. P. aeruginosa can be quantified within the concentration ranges of 2.6 × 103 cfu mL-1 - 2.6 × 108 cfu mL-1 and 2.6 × 102 cfu mL-1 - 2.6 × 107 cfu mL-1 with colorimetric and pressure readout modes, respectively. The both modes can achieve quantitation of P. aeruginosa within 25 min. Thus the "both-in-one" 3D printed device with dual-mode readout function offers a rapid, sensitive, and specific platform for POCT of pathogenic bacteria.

Dual-Mechanism-Driven Ratiometric Electrochemiluminescent Biosensor for Methicillin-Resistant Staphylococcus aureus.

Design of a ratiometric method is a promising pathway to improve the sensitivity and reliability of electrochemiluminescent (ECL) assay, for which the signals produced at two distinct potentials change reversely as it is applied to the target analyte. Herein, a biosensor for ECL assay of methicillin-resistant Staphylococcus aureus (MRSA) was constructed by immobilizing porcine IgG for capturing MRSA onto an electrode that was precoated with ß-cyclodextrin-conjugated luminol nanoparticles (ß-CD-Lu NPs) as an anodic luminophore. MOF PCN 224 loaded with an atomically distributed Zn element (PCN 224/Zn) was conjugated with phage recombinant cellular-binding domain (CBD) to act as a cathodic luminophore for tracing MRSA. After the formation of the sandwich complex of ß-CD-Lu NPs-porcine IgG/MRSA/PCN 224/Zn-CBD on the biosensor, two ECL reactions were triggered with cyclic voltammetry. The anodic process of the ß-CD-Lu NPs-H2O2 system and the cathodic process of the PCN 224/Zn-S2O82- system competed to react with reactive oxygen species (ROS) for producing ECL emission, which led to a reverse change of the two signals. Meanwhile, the overlap of the ß-CD-Lu NPs emission spectrum and PCN 224/Zn absorption spectrum effectively triggered ECL resonance energy transfer between the donor (ß-CD-Lu NPs) and the acceptor (PCN 224/Zn). Thus, a ratiometric ECL method was proposed for assaying MRSA with a dual-mechanism-driven mode. The detection limit for assaying MRSA is as low as 12 CFU/mL. The biosensor was applied to assay MRSA in various biological samples with recoveries ranging from 84.9 to 111.3%.

Layer Growth Inhibiting Strategy for Superior-Loading Atomic Metal Sites on Ultrathin Layered Double Hydroxides as the Efficient Chemiluminescence Probes.

Owing to the remarkable catalytic attributes, single-atom catalysts (SACs) have exhibited promising application prospects as the substitutes of natural enzymes. However, the low loading amount of atomic sites on typical SACs (no more than 5 wt %) significantly restricts their increased capability. Hereby, a layer growth inhibitor protocol was attempted to optimize anchoring isolated Co atoms efficiently on ultrathin monolayer layered double hydroxides (LDHs). Superior to the conventional multiple-layer LDHs, the synthesized monolayer LDHs (7.29 nm-thick) served as the emerging support for dispersing substantial active sites and featured a dramatic loading content of 32.5 wt %. Through X-ray absorption spectroscopy, the atomically dispersed active centers on Co SACs were verified as Co-N4 moieties. The results of radical scavenger experiments and electron paramagnetic resonance spectroscopy showed that Co SACs were favorable to the high yield of reactive oxygen species originating from the decomposition of H2O2. Therefore, Co SACs functioned as a sensitive enhancer to drastically boost the luminol-H2O2 chemiluminescence intensity by ∼4713-fold, which excelled drastically over these previously reported SACs. Furthermore, Co SACs were adopted as chemiluminescent probes for the quantitation of chlorothalonil, wherein a low detection limit of 49 pg mL-1 (3σ) was achieved. Additionally, the successful application in recovery trials demonstrated the favorable feasibility of Co SACs. The facile layer growth inhibitor protocol affords SACs with improved loading properties and even superior catalytic performances for sensitive luminescent bioassays.

Preparation of Co dual atomic site catalysts loaded on defect-engineered MOFs material with superb chemiluminescent enhancement effect for sensitive detection of bacteria.

BACKGROUND: Dual atomic site catalysts (DASCs) have aroused extensive interest in analytical chemistry on account of the superb catalytic activity caused by the highly-exposed active centers and synergistic effect of adjacent active centers. The reported protocols for preparing DASCs usually involve harsh conditions such as acid/base etching and high-temperature calcination, leading to unfavorable water dispersity and restricted application. It is crucial to develop DASCs with satisfactory water dispersity, improved stability, and mild preparation procedures to facilitate their application as signal probes in analytical chemistry. RESULTS: Formic acid was adopted as a modulator for preparing MOF-808 with abundant defective sites, which was used as the carrier for implanting Co atoms. Co DASCs with a special coordination structure of Co2-O10 and a high loading efficiency of 11.1 wt% were prepared with a mild solvothermal protocol. The resultant Co DASCs can significantly accelerate decay of H2O2 for forming numerous reactive oxygen radicals and boost chemiluminescent (CL) signal. Co DASCs at 1.0 µg mL-1 can enhance the CL signal of luminol-H2O2 system by about 5800 times. Thanks to their satisfactory water dispersity and excellent CL enhancement performance, they were used as ultra-sensitive CL signal probes for monitoring methicillin-resistant Staphylococcus aureus. The method shows a detection range of 102-107 CFU mL-1 and a detection limit of 47 CFU mL-1. Antibiotic susceptibility test was performed with the established CL method to prove its practicality. SIGNIFICANCE: The water dispersible Co DASCs prepared with facile and mild solvothermal protocol exhibit prominent peroxidase-like activity and can promote the production of reactive oxygen radicals for boosting CL signal. Therefore, this study paves an avenue for implanting DASCs in defect-engineered carrier to prepare signal probes suitable for development of ultra-sensitive CL analytical methods.

Fluorescent immunochromatographic test strip for therapeutic drug monitoring of methotrexate with high sensitivity and wide dynamic range.

As a front-line chemotherapeutic drug for maintenance and consolidation therapy, methotrexate (MTX) has widely been applied to treat various tumors and some inflammatory diseases. However, because of its severe toxicity ascribed to low selectivity, it is necessary to monitor therapeutic drugs in high-dose MTX therapeutic regimens to ensure treatment safety. In this work, we developed a fluorescent immunochromatographic test strip (FITS) for monitoring MTX by employing time-resolved fluorescent microspheres as signal probes. With a competitive immunoassay mode, the FITS for MTX shows a super-wide dynamic range of 10 pM-10 µM, covering the entire clinical therapeutic concentration range of MTX. Therapeutic drug monitoring of MTX can be achieved within 7 min with high specificity, facilitating the timely rescue of drug poisoning led by high-dose MTX treatment. The method was employed for monitoring MTX in the spiked human serum, urine, and milk, showing acceptable recoveries ranging from 94.0 to 110.0%. The established FITS has been applied to MTX detection in serum obtained from high-dose MTX treatment. The results from FITS and enzyme multiplied immunoassay technique showed no significant difference, suggesting its reliability for usage in real biological samples. The device shows promise in point-of-care therapeutic drug monitoring for resource-limited countries and institutes, which significantly facilitates overcoming the lag time between sampling and results.

Paper-based analytical device integrated with bacteriophage tail fiber protein for bacteria detection and antimicrobial susceptibility test.

Severe antimicrobial resistance calls for developing rapid, sensitive and affordable methodological platform for clinical diagnosis of bacterial infection. Herein, a paper-based analytical device (PAD) for fluorescent (FL) detection and antimicrobial susceptibility test (AST) of Pseudomonas aeruginosa (P. aeruginosa) was fabricated by defining 96 hydrophilic microzones on a filter paper using a handheld stamp dipped with liquid wax. The size of microzones was designed to be consistent with traditional 96-well microplate, thus the FL signals can be collected by a commercialized microplate reader. Streptavidin was immobilized into the microzones by chitosan-glutaraldehyde crosslinking reaction, and then biotinylated bacteriophage tail fiber protein (TFP) was conjugated through biotin-streptavidin affinity system. TFP and fluorescein isothiocyanate (FITC) labeled antimicrobial peptide were used as capture agent and signal probe, respectively, for FL detection of P. aeruginosa on the PAD. The linear range for quantifying P. aeruginosa is 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL, with a detection limit of 137 CFU/mL. The PAD was also applied to conduct AST of P. aeruginosa for imipenem, meropenem, cefepime, amikacin, and gentamicin, and the results are consistent with the traditional broth dilution method. The PAD provides an affordable diagnosis platform for bacterial infection, especially in resource-limited institutes and countries.

Cobalt Species-Loaded MOFs as Chemiluminescent Catalysts for Monitoring Carbendazim.

The application of active metal-based nanoscale catalysts as signal enhancers for chemiluminescent immunoassay (CLIA) is restricted by poor thermodynamic stability and ease of aggregation. For the present exploration, zirconium-based MOFs UiO-66-NH2 were adopted as supports to load cobalt species by an impregnation-reduction approach. Cobalt species were uniformly distributed in the framework architecture of the MOF materials. The prepared cobalt-loaded MOF hybrids, noted as UiO-66-NH2/Co, display superior chemiluminescence (CL) catalytic activity owing to the introduction of cobalt catalytic centers. The CL catalytic capability of UiO-66-NH2/Co hybrids is about 18 times of that of free cobalt ions at the same cobalt amount. The results of mechanism exploration manifest that the hybrids are capable of accelerating the decay of hydrogen peroxide and promoting the yield of reactive oxygen species. Based on their remarkable CL catalytic capability, a CLIA approach was proposed to monitor carbendazim by adopting the hybrids as signal probes, which showed the merits of high sensitivity and satisfactory selectivity. Carbendazim was quantitated within a concentration range of 0.05 to 60 ng mL-1, with a detection limit of 19.8 pg mL-1. The results for monitoring spiked samples verify the acceptable practicality of the proposed CLIA approach.

Rapid separation and detection of Listeria monocytogenes with the combination of phage tail fiber protein and vancomycin-magnetic nanozyme.

In this work, a lateral flow assay for Listeria monocytogenes was developed based on phage tail fiber protein (TFP) and triple-functional nanozyme probes with capture-separation-catalytic activity. Inspired by interaction between phage and bacteria, TFP of L. monocytogenes phage was immobilized on test line as capture molecule, which replaced traditional antibody and aptamer. After Gram-positive bacteria was captured and separated from samples by nanozyme probes modified with vancomycin (Van), TFP specifically recognized L. monocytogenes and overcame non-specific binding of Van. Special color reaction between Coomassie Brilliant Blue and bovine serum albumin which was an amplification carrier on probe was simply utilized as control zone to replace traditional control line. Relying on enzyme-like catalytic activity of nanozyme, this biosensor realized improved sensitivity and colorimetric quantitative detection with a detection limit of 10 CFU mL-1. Analytic performance results suggested this TFP-based biosensor provided a portable, sensitive and specific strategy to detect pathogen.

Mn Single-Atom Nanozymes with Superior Loading Capability and Superb Superoxide Dismutase-like Activity for Bioassay.

Single-atom nanozymes (SANs) with highly exposed active sites and remarkable catalytic activity have shown noteworthy practicability in heterogeneous catalysis-based bioassay. Nevertheless, most of them were reported with peroxidase-like activity and ordinary loading capability. It is still a challenge to prepare high-loading SANs with desirable superoxide dismutase (SOD)-like activity. In this work, Mn SAN was successfully confined in the frameworks of Prussian blue analogues formed on Ti3C2 MXene sheets with the assistance of massive surfactants, which show a superior loading efficiency of 13.5 wt % (typically <2.0 wt %). The prepared Mn SAN exhibits desirable superoxide radical anion elimination capability because of its SOD-like activity. Moreover, due to the wide-spectrum absorption behavior of the carriers, Mn SAN shows a synergistically quenching efficiency up to 98.89% on the emission of the reactive oxygen species-mediated chemiluminescent (CL) system. Inspired by these features, a CL quenching method was developed on a lateral flow test strip platform by utilizing Mn SAN as a signal quencher and acetamiprid as a model analyte. The method for detecting acetamiprid shows a detection range of 1.0-10,000 pg mL-1 and a limit of detection of 0.3 pg mL-1. Its accuracy has been validated by detecting acetamiprid in medicinal herbs with acceptable recoveries. This work opens an avenue for preparing SANs with a surfactant-assisted protocol and pioneers the study of SANs with SOD-like activity in bioassay.

Employment of the Phage Cocktail as a Species-Specific Recognition Agent for Wide-Spectrum Detection of Bacterial Strains.

Phages have already been employed to detect bacteria because of their specific recognition capability and strong infectious activity toward their host. However, the reported single-phage-based techniques are inevitably restricted by false negative results that arose from extremely high strain specificity of phages. In this study, a cocktail composed of three Klebsiella pneumoniae (K. pneumoniae) phages was prepared as a recognition agent to broaden the recognition spectrum for detecting this bacterial species. A total of 155 clinically isolated strains of K. pneumoniae collected from four hospitals were adopted to test its recognition spectrum. A superior recognition rate of 91.6% for the strains was achieved due to the complementarity of the recognition spectra of the three phages composed of the cocktail. However, the recognition rate is as low as 42.3-62.2% if a single phage is employed. Based on the wide-spectrum recognition capability of the phage cocktail, a fluorescence resonance energy transfer method was established for detecting K. pneumoniae strains by employing fluorescein isothiocyanate labeled to the phage cocktail and Au nanoparticles labeled to p-mercaptophenylboronic acid as energy donors and acceptors, respectively. The detection process can be completed within 35 min, with a wide dynamic range of 5.0 × 102-1.0 × 107 CFU/mL. The application potential was verified by applying it to quantitate K. pneumoniae in different sample matrixes. This pioneer work opens an avenue for achieving wide-spectrum detection of different strains belonging to the same bacterial species with the phage cocktail.

Preparation of CH3NH3PbBr3 Perovskites Encapsulated in ZIF-8 with Improved Stability and Their Application in Fluorimetry and Information Encryption.

Metal halide perovskites (MHPs) have been promising functional materials for developing solar cells, lasers, photodetectors, and sensors due to their outstanding optical and electrical characteristics. However, they suffer from very poor stability for their high sensitivity to some environmental factors such as temperature, UV irradiation, pH, and polar solvent, which limits their extensive practical applications. Herein, a derived metal organic framework material, Pb-ZIF-8, was prepared as a precursor via a doping protocol. Then, CH3NH3PbBr3 perovskites encapsulated in ZIF-8 (CH3NH3PbBr3@ZIF-8) with green fluorescent (FL) emission were synthesized via a facile in situ protocol by using the derived metal organic frameworks material as a source of Pb element. With the protection of encapsulated ZIF-8, the perovskites material shows good FL properties under various harsh environmental conditions, which facilitates facile application in various fields. To verify the practical application potential of CH3NH3PbBr3@ZIF-8, we utilized them as FL probes to establish a highly sensitive method for detecting glutathione. Furthermore, the rapid conversion process from non-FL Pb-ZIF-8 to FL CH3NH3PbBr3@ZIF-8 was utilized to realize encryption and decryption of confidential information. This work opens an avenue to the development of perovskites-based devices with greatly improved stability in harsh external environments.

Mycobacteriophage Derived Lipoarabinomannan Binding Protein for Recognizing Non-Tuberculosis Mycobacteria.

Non-tuberculosis mycobacteria (NTM) is one family of pathogens usually leading to nosocomial infections. Exploration of high-performance biological recognition agent plays a pivotal role for the development of point-of-care testing device and kit for detecting NTM. Mycobacterium smegmatis (M. smegmatis) is a NTM which has been frequently applied as an alternative model for highly pathogenic mycobacteria. Herein, a recombinant tail protein derived from mycobacteriophage SWU1 infecting M. smegmatis was expressed with Escherichia coli system and noted as GP89. It shows a fist-like structure according to the results of homology modeling and ab initio modeling. It is confirmed as a lipoarabinomannan (LAM) binding protein, which can recognize studied NTM genus since abundant LAM constructed with d-mannan and d-arabinan is distributed over the mycobacterial surface. Meanwhile an enhanced green fluorescent protein (eGFP)-fused GP89 protein was acquired with a fusion expression technique. Then GP89 and eGFP-fused GP89 were applied to establish a sensitive and rapid method for fluorescent detection of M. smegmatis with a broad linear range of 1.0 × 102 to 1.0 × 106 CFU mL-1 and a low detection limit of 69 CFU mL-1. Rapid and reliable testing of antimicrobial susceptibility was achieved by the GP89-based fluorescent method. The present work provides a promising recognition agent for studied NTM and opens an avenue for clinical diagnosis of NTM-induced infections.

Smartphone-Based Pressure Signal Readout Device Combined with Bidirectional Immunochromatographic Test Strip for Dual-Analyte Detection.

Pressure has been a facile signal readout mode for developing point-of-care testing devices due to the attractive features of portability, accessibility, rapidity, and affordability. Herein, a pressure signal readout device was designed by integrating two homemade needle-type piezoresistive transducers, a controller for a thin-film piezoresistive sensor and a smartphone. Meanwhile, a bidirectional immunochromatographic test strip was designed as an immunoreaction platform for dual-analyte detection. Using PdCuPt nanoparticles with catalase-mimic activity as signal tags, the pressure signals triggered by catalyzed aerogenous reaction were monitored by the pressure signal readout device and read on a smartphone with the Bluetooth module. In this proof-of-principle work, imidacloprid and carbendazim were detected as model analytes. The dynamic ranges for quantitating imidacloprid and carbendazim are 20 pg mL-1 to 50 ng mL-1 and 50 pg mL-1 to 50 ng mL-1, respectively. The whole immunoassay process was completed within 16 min. The recovery values for imidacloprid and carbendazim spiked into herbal medicines are 82.0-110.0 and 84.0-116.0%, respectively, verifying its reliability for real sample detection. As the smartphone APP and controller for a thin-film piezoresistive sensor contain 12 signal channels, the system can be easily extended to meet the demand for high-throughput screening.

A Risk Prediction Model for Post-endoscopic Retrograde Cholangiopancreatography Pancreatitis After Stent Insertion for Malignant Biliary Obstruction: Development and Validation.

OBJECTIVES: Pancreatitis is the most common complication of post-endoscopic retrograde cholangiopancreatography (ERCP). There are currently no prediction models, particularly for post-ERCP pancreatitis (PEP) after biliary stent placement due to malignant biliary obstruction (MBO). To that end, we aim to develop and validate a predictive model for PEP. METHODS: We retrospectively analyzed the data of patients who underwent ERCP for biliary stent placement due to MBO at the Second Affiliated Hospital of Harbin Medical University from January 1, 2014 to August 31, 2021. The eligible patients were randomly allocated to the development and validation cohorts. A prediction model was built using the development cohort, and the model's effect was validated using a validation cohort. RESULTS: A total of 1524 patients were enrolled, including 1016 in the development cohort and 508 in the validation cohort, with an overall PEP rate of 7.1%. The model's predictors included acute pancreatitis history, the absence of pancreatic duct dilation, nonpancreatic cancer, difficult cannulation, and pancreatic injection. The area under the curve (AUC) in the development cohort was 0.810, and the incidence of PEP in the low-risk, medium-risk, and high-risk groups was 1.53%, 9.12%, and 36.36%, respectively. Meanwhile, the AUC of the validation cohort was 0.781, and the incidence of PEP in the low-risk, medium-risk, and high-risk groups was 4.17%, 8.75%, and 41.67%, respectively. CONCLUSIONS: This study was the first to build and validate a risk prediction model, especially for PEP after biliary stent placement due to MBO. Moreover, this model might assist clinicians in identifying high-risk patients and help implement preventive measures in a more timely manner.

CoN4-supported Co2N metal clusters for developing sensitive chemiluminescent immunochromatographic assays.

In view of the optimal catalytic efficiency (∼100%), single-atom site catalysts are being widely exploited in a range of areas including organic synthesis, energy conversion, environmental remediation, biotherapy, etc. However, low loading ratio of the unitary active sites on single-atom site catalysts dramatically hinders the remarkable improvement of their catalytic activity. Hereby, a facile low-temperature reduction protocol was adopted for synthesizing CoN4-supported Co2N metal clusters on graphitic carbon nitride, which show the remarkably superior chemiluminescent (CL) catalytic capacity than some reported pure single-atom site catalysts. Nitrogen-encapsulated Co2N clusters coupled with isolated Co-N4 moieties (Co2N@Co-N4) endowed the synergetic catalysts with high Co content of 53.2 wt%. Through X-ray absorption spectroscopy, the synergetic active sites (Co2N@Co-N4) afforded the CoN4-supported Co2N clusters with the remarkable catalytic activity for accelerating the decomposition of H2O2 to produce extensive superoxide radical anion rather than singlet oxygen or hydroxyl radical. Therefore, the CoN4-supported Co2N clusters possessed the superb enhancement effect on luminol-H2O2 CL reaction by ∼22829 times. The CoN4-supported Co2N clusters were utilized as signal probes to establish a CL immunochromatographic assay (ICA) platform for quantitating mycotoxins. Herein, aflatoxin B1 was employed as a mode analyte and the limit of detection was as low as 0.33 pg mL-1 (3σ). As a proof-of-principle work, the developed ICA protocol was successfully employed on the detection of aflatoxin B1 spiked in Angelica dahurica and Ganoderma lucidum with acceptable recoveries of 84.0-107.0%. The ideal practicability of the work elucidates that CoN4-supported Co2N clusters showed a new perspective for developing the sensitive CL biosensing.

Defective Site Modulation Strategy for Preparing Single Atom-Dispersed Catalysts as Superior Chemiluminescent Signal Probes.

Single atom-dispersed catalysts (SADCs) with highly exposed active sites can be used as sensitive signal probes because of their superior catalytic efficiency. However, the dispersed atoms tend to aggregate, restricting the loading capacity of metal atoms. Herein, the defective sites on Zr-oxo clusters of metal-organic frameworks (MOFs) UiO-66-NH2 were modulated by excessive acetic acid and utilized for confining metal atoms with high loading capacity. To verify the feasibility of the designed strategy, the Co element was loaded onto MOFs UiO-66-NH2 to prepare SADCs with desirable Fenton-like activity. The prepared Co SADCs at a low concentration of 1.0 µg mL-1 are found to boost chemiluminescent (CL) emission for 3700 times due to the significantly improved Co content of 5.55 wt %. The superior CL enhancement efficiency is ascribed to reactive oxygen species generated by the accelerated decay of H2O2. To verify the application potential in CL assay, they were used as signal probes to establish an immunoassay method for carbendazim with a dynamic range of 1.0 pg mL-1 to 25 ng mL-1 and a limit of detection of 0.33 pg mL-1. This defective site modulation strategy paves an avenue for preparing SADCs with a high CL response by improving the loading capacity of metal atoms.

PEGylated Ni Single-Atom Catalysts as Ultrasensitive Electrochemiluminescent Probes with Favorable Aqueous Dispersibility for Assaying Drug-Resistant Pathogens.

Ni single-atom catalysts (SACs) were synthesized by high-temperature calcination of nickel ions and 1,10-phenanthroline on carbon black as a carrier. Benefiting from the ultrahigh atom utilization efficiency, Ni SACs can significantly accelerate decay of dissolved oxygen to generate abundant reactive oxygen species through an oxygen reduction reaction occurring on cathodes. The generated reactive oxygen species can vastly enhance the electrochemiluminescent (ECL) signal of luminol without participation of exogenous co-reactants. To overcome the inherent unfavorable aqueous dispersibility of Ni SACs prepared by the calcination protocol, they were functionalized with highly hydrophilic PEG 2000. Thanks to the abundant carboxyl groups on PEG 2000, the PEGylated Ni SACs (Ni@PEG) can be used as ECL probes to tag biorecognition molecules. In this proof-of-principle work, an ECL biosensor for assaying methicillin-resistant Staphylococcus aureus was developed by using porcine IgG as capture molecule and phage cell-binding domain tagged with Ni@PEG as signal tracer. It shows a broad linear range of 73-7.3 × 106 CFU/mL and a low detection limit of 25 CFU/mL. The recovery values for assaying spiked samples are between 80.8 and 119.2%. It was also utilized to assess MRSA susceptibility to four antibiotics, with results consistent with those obtained by the standard broth microdilution technique. To the best of our knowledge, it is the first time to utilize aqueous dispersible SACs as highly sensitive ECL probes for developing biosensors.

Synergetic Dual-Site Atomic Catalysts for Sensitive Chemiluminescent Immunochromatographic Test Strips.

In view of the outstanding catalytic efficiency, single-atom catalysts (SACs) have shown great promise for the construction of sensitive chemiluminescent (CL) platforms. However, the low loading amount of active sites dramatically obstructs the improved catalytic activity of these metal SACs. Benefiting from the exceedingly unique catalytic properties of the metal-metal bonds, atomic clusters may give rise to enhancing the catalytic properties of SACs based on the synergistic effects of dual atomic-scale sites. Inspired by this, atomic Co3N clusters-assisted Co SACs (Co3N@Co SACs) were synthesized through a facile doping method. Through X-ray absorption spectroscopy, the active metal sites in the synergetic dual-site atomic catalysts of Co3N@Co SACs were confirmed to be Co-O4 and Co3-N moieties. Co3N@Co SACs served as a superior co-reactant to remarkably enhance the luminol CL signal by 2155.0 times, which was prominently superior to the boosting effect of the pure Co SACs (98.4 times). The synergetic dual-site atomic catalysts contributed to accelerating the decomposition of H2O2 into singlet oxygen as well as superoxide radical anions to display superb catalytic performances. For a concept employment, Co3N@Co SACs were attempted to utilize as CL probes for establishing a sensitive immunochromatographic assay to quantitate pesticide residues, in which imidacloprid was adopted as the model analyte. The quantitative range of imidacloprid was 0.05-10 ng mL-1 with a detection limit of 1.7 pg mL-1 (3σ). Furthermore, the satisfactory recovery values in mock herbal medicine samples demonstrated the effectiveness of the proposed Co3N@Co SAC-based CL platform. In the proof-of-concept work, synergetic dual-site atomic catalysts show great perspectives on trace analysis and luminescent biosensing.

Small ubiquitin-related modifier-fused bacteriophage tail fiber protein with favorable aqueous solubility for lateral flow assay of Pseudomonas aeruginosa.

Rapid and sensitive assay of pathogenic bacteria is critical for minimizing the risk of infectious diseases. Inspired by the interaction between bacteriophages and host bacteria, we obtained a gene sequence of tail fiber protein (TFP) from Pseudomonas aeruginosa (P. aeruginosa) bacteriophage. Then the gene sequence was used to express a recombinant TFP, which can act as a potential capture molecule for P. aeruginosa. Small ubiquitin-related modifier (SUMO) tag was fused onto the TFP fragment to overcome its unfavorable aqueous solubility. The obtained SUMO tag-fused TFP (STFP) can be uniformly distributed onto a nitrocellulose membrane to form a test line due to the improved aqueous solubility, which facilities fabrication of a lateral flow assay strip. Thus we developed a lateral flow assay method by using STFP as a capture molecule and AuCo nanoparticles-labeled aptamer as a signal tracer for point-of-care testing of P. aeruginosa. By using the test strip, P. aeruginosa can be semi quantified with color band and quantified with chemiluminescent (CL) signal catalyzed by AuCo nanoparticles. The concentration range for quantification is 3.3 × 102 CFU/mL to 3.3 × 107 CFU/mL. The test strip was applied to assay P. aeruginosa in different sample matrixes including cerebrospinal fluid, physiological salt solution, drinking water and pear juice. The results demonstrate the application potential of the STFP-based lateral flow assay for medical diagnosis, food and drug safety monitoring.

Shape-Encoded Functional Hydrogel Pellets for Multiplexed Detection of Pathogenic Bacteria Using a Gas Pressure Sensor.

Gas pressure is a promising signal readout mode in point-of-care testing for its merits such as rapidity, simplicity, affordability, and no need for sophisticated instrumentation. Herein, a gas pressure sensor for multiplexed detection of pathogenic bacteria was developed on a hydrogel platform. Spherical and square hydrogel pellets prepared by cross-linking of sodium alginate were functionalized with nisin and ConA for the capture of Staphylococcus aureus and Escherichia coli O157:H7, respectively. By using the shape-encoded functional hydrogel pellets and aptamer-modified platinum-coated gold nanoparticles (Au@PtNPs), a dual-molecule recognition mode was established for rapid and specific detection of the two pathogenic bacteria. Au@PtNPs were applied as signal probes to efficiently catalyze the decomposition of H2O2 for generating abundant O2, which was converted into an amplified gas pressure signal. In two closed containers, the significant gas pressure signals were monitored with a portable pressure meter to quantitate the two pathogenic bacteria. The sensor was successfully applied to detect the pathogenic bacteria in various environmental, biological, and food samples. Thus, the proof-of-principle work paves a new avenue for multiplexed detection of pathogenic bacteria with shape-encoded hydrogel pellets combined with gas pressure signal readout.