Dual-Modal Immunochromatographic Test for Sensitive Detection of Zearalenone in Food Samples Based On Biosynthetic Staphylococcus aureus-Mediated Polymer Dot Nanocomposites.

The rapid detection of toxins is of great significance to food security and human health. In this work, a dual-modality immunochromatographic test (DICT) mediated by Staphylococcus aureus (SA)-biosynthesized polymer dots (SABPDs) was constructed for sensitive monitoring of zearalenone (ZEN) in agro products. The SABPDs as potent microorganism nanoscaffolds with excellent solubility, brightness, and stability were ingeniously fabricated employing hydroquinone and SA as precursors in the Schiff base reaction and a self-assembly technique. Thanks to the fact that they not only preserved an intact microsphere for loading Fc regions of monoclonal antibodies (mAbs) and the affinity of their labeled mAbs to antigen but also generated superb colorimetric-fluorescent dual signals, the versatile SABPDs manifested unique possibilities as the new carriers for dual-readout ICT with remarkable enhancement in sensitivity in ZEN screening (limit of detection = 0.036 ng/mL, which was 31-fold lower than that of traditional gold nanoparticle-based ICT). Ultimately, the proposed immunosensor performed well in millet and corn samples with satisfactory recoveries, demonstrating its potential for point-of-care testing. This work offers a bio-friendly strategy for biosynthesizing cell-based PD vehicles with bimodal signals for food safety analysis.

Polydopamine nanospheres-assisted direct PCR for rapid detection of Escherichia coli O157:H7.

Polymerase chain reaction (PCR) is one of the most common methods for rapid monitoring of foodborne pathogens; however, it requires purified nucleic acid as a template. Conventional nucleic acid purification is a time-consuming and laborious process. To overcome this, we developed polydopamine nanospheres (PDA NPs)-assisted direct PCR for detecting Escherichia coli O157:H7 (E. coli O157:H7). PDA NPs significantly enhanced PCR efficiency because of their strong interaction with PCR reagents, including polymerase and primers, thereby enabling regulation of the PCR performance. The optimal concentration and diameter for PDA NPs were 0.10 µg/µL and 504 nm, respectively. The PDA NPs-assisted direct PCR exhibited high sensitivity in E.coli O157:H7 detection. The detection limit of PDA NPs-assisted direct PCR was 6.7 × 104 CFU/mL, which was 10-fold lower than that of direct PCR (6.7 × 105 CFU/mL). Moreover, the sensor demonstrated excellent selectivity against E. coli O157:H7, with a negative reaction to eight other common pathogens. Most importantly, the PDA NPs-assisted direct PCR detected the order of 104-5 CFU/mL E.coli O157:H7 in milk, beef, and watermelon samples. No cultural enrichment was required, with the whole process taking <3 h. Therefore, PDA NPs-assisted direct PCR has tremendous potential in the rapid and sensitive detection of pathogens.

Diverse Dyes-Embedded Staphylococcus aureus as Potential Biocarriers for Enhancing Sensitivity in Biosensing.

Nanomaterials-based immunochromatographic assays (ICAs) have gained great commercial success in real-life point-of-care testing (POCT). Exploring novel carriers of ICAs with improved signaling and sustained activity favors the development of sensitive POCT. Herein a potent signal biotag, colored Staphylococcus aureus (SA), was created for ICA carriers through a mild self-assembly strategy, providing high luminance and abundant specific binding sites for immobilization of monoclonal antibodies (mAbs). The biocompatible SA-dyes (SADs) retained both an intact surface structure for mAbs labeling (Fc portion) and the superior bioactivity of immobilized mAbs (affinity constant was about 109 M-1), thus waiving the intrinsic limitations of traditional nanomaterials and endowing high sensitivity. Proof-of-concept was demonstrated by employing Congo red- or/and fluorescein isothiocyanate-embedded SA (SACR, SAFITC, and SACR-SAFITC) as ICA carriers to detect zearalenone (ZEN) through colorimetric or/and fluorimetric signals. Furthermore, the ICAs satisfied the clinical requirement perfectly, including limit of detection (0.013 ng/mL, which was at least an 85-fold improvement over that of traditional gold nanoparticles-based ICA), linearity (R2 > 0.98), reproducibility (RSD < 8%), selectivity, and stability. Importantly, the proposed biosensors could be well-applied in four real samples for ZEN monitoring with satisfactory recoveries, correlating well with the results from liquid chromatography-tandem mass spectrometry (LC-MS). This work also proved a universal design for tailoring coloration bands for SAD-ICA detection of multiple analytes.

Killing Two Birds with One Stone: Shape-Memory Cryogels for Hemostasis and Wound Repair.

The development of shape-memory hemostatic agents is crucial for the treatment of deep incompressible bleeding tissue. However, there are few reports on biomaterials that can monitor bacterial infection at the wound site in real time following hemostasis and effectively promote repair. In this study, we propose a multifunctional QCSG/FLZ cryogel composed of glycidyl methacrylate-functionalized quaternary chitosan (QCSG), fluorescein isothiocyanate (FITC), and a lysozyme (LYZ)-modified zeolitic imidazolate framework (ZIF-8) for incompressible bleeding tissue hemostasis and wound repair. QCSG/FLZ cryogels possess interconnected microporous structure and enhanced mechanical properties, allowing them to be molded into different shapes for effective hemostasis in deep incompressible wounds. Furthermore, the fluorescence quench signal of QCSG/FLZ cryogels enables timely monitoring of bacterial infection when wound triggers infection. Meanwhile, the acidic microenvironment of bacterial infection induces structural lysis of ZIF-8, releasing LYZ and Zn2+, which effectively kill bacteria and accelerate wound repair. In conclusion, our study not only provides potential application of QCSG/FLZ cryogels for hemostasis in deep incompressible wounds but promisingly promotes the development of a tissue repair technique.

Immunochromatographic Assay based on Sc-TCPP 3D MOF for the rapid detection of imidacloprid in food samples.

In this work, a highly sensitive immunochromatographic test strip (ITS) based on Scandium-Tetrakis (4-carboxyphenyl) porphyrin (TCPP) metal-organic framework nanocubes (ScTMNs) was developed for ultrasensitive and facile visual determination of imidacloprid (IDP). TCPP as the porphyrin-based planar ligand and Sc3+ as the metal center were applied to form the ScTMNs via coordination chelation. Giving the credit to its excellent optical characteristics, strong affinity with monoclonal antibodies, and favorable biocompatibility, the ScTMNs was selected as a signal tag. Under optimized conditions, the ITS exhibited a great liner relationship in the range of 0.04-3 ng/mL and the detection limit was 0.04 ng/mL for the IDP detection. Additionally, IDP was successfully detected in tomatoes, millet, corn and carrot samples with satisfied recoveries. To the best of our knowledge, this is the first time that ScTMNs have been used in immunochromatography which are expected to have potential applications in detection of other substances.

A bacteria-triggered wearable colorimetric band-aid for real-time monitoring and treating of wound healing.

Early diagnosis of bacterial infection and tracking of treatment effect are of great importance for developing a "sense-and-treat" integrated system. Herein, we developed a bacteria-triggered, portable, wearable and colorimetric film-based band-aid (FBA) for closed-loop monitoring and light-controlled therapy of wound infection. FBA with high photothermal conversion efficiency of 52.56% was prepared by wrapping Bi2S3 nanoflowers (BS NFs) loaded with rhodium nanoparticles (Rh NPs) and bromothymol blue (BTB) into LB agar film, integrating bacteria-triggered color change, photothermal/photodynamic therapy (PTT/PDT) synergistic bactericidal therapy and agar-based band aid in one intelligent system. Initially, FBA effectively simulates the pH sensing mechanism, and monitors the occurrence of bacterial infections within 5 min through color changes of Staphylococcus aureus (S. aureus) from blue to yellow and Escherichia coli (E. coli) from yellow to blue. Additionally, the short-term and controlled antibacterial strategy of "one light dual-mode responses" (photothermal and photodynamic responses) was implemented with the introduce of near-infrared (NIR). Ultimately, the effectiveness of FBA was fully validated in the monitoring and treating of S. aureus-infected mouse wounds. Notably, the designed FBA decisively abandoned off-target side effects maximizing the treatment effect and nakedly tracking therapeutic situation in real time, contributing an effective antibacterial alternative strategy for reducing the use of antibiotics. To the best of our knowledge, such integrated system is still unreported on film-fixed model. In view of the advantages of the low cost and convenience of the simple device, the integrated design is expected to provide a solution for the development of a closed-loop biomedical system combining diagnosis and treatment.

Golf-shaped Bi2Se3 microparticles based-immunochromatographic strip for ultrasensitive detection of Acetamiprid.

Rapid and sensitive detection of pesticide is of significance to the field of food safety and human health, but it is still challenging due to interferents from complex food matrices. Herein, a superb golf-shaped Bi2Se3 microparticles-based immunochromatographic strip (BS MPs-ICS) was constructed for ultrasensitive detection of acetamiprid (ATM). The novel immune signal tag demonstrated outstanding luminance, excellent biocompatibility, and high affinity with ATM (affinity constant was 3.874 ×107 M-1), which not only possessed a preeminent labeling efficiency but also significantly improved detection sensitivity. After optimization, the limit of detection (LOD) of the BS MPs-ICS was 8.780 pg/mL with an excellent linear relationship at the range of 0.010-6.000 ng/mL, which was approximately 62-fold lower than that of conventional gold nanoparticles-ICS (0.545 ng/mL), The BS MPs-ICS biosensor was well applied in apple and tomato samples with satisfactory recoveries of 83.823-99.223% (relative standard deviation < 1.739%). Therefore, the BS MPs-ICS could serve as a promising candidate for ATM detection in complicated samples and develop a new method in real-time monitoring.

Rose petals-like Bi semimetal embedded on the zeolitic imidazolate frameworks based-immunochromatographic strip to sensitively detect acetamiprid.

Ultrasensitive and facile detection of Acetamiprid (ACE) is of exceptional significance to assess the environmental and biological pollution. In this study, an advanced Bi semimetal/Zeolitic imidazolate frameworks hybrid material-based immunochromatographic strip (Bi/ZIF HM-ICS) sensor was developed for the sensitive detection of ACE. The novel Bi/ZIF HM was prepared through one-pot hydrothermal reduction of Bi nanoparticles on ZIF, which was selected as a signal tag taking advantages of its excellent color intensity, strong affinity with monoclonal antibodies (mAbs), and favorable biocompatibility. Bi/ZIF HM could not only improve the utilization efficiency of mAbs but also boost the sensing performance. Under optimal conditions, the limit of detection (LOD) of the Bi/ZIF HM-ICS was 4.68 pg/mL with the linear range from 0.01 ng/mL to 6 ng/mL, which was 98-fold lower than that of traditional gold nanoparticles-based ICS (0.457 ng/mL), and the recoveries of the Bi/ZIF HM-ICS ranged from 80.27% to 118.52% with the relative standard deviation (RSD) below 3.67% in pear, apple, tomato, and cucumber. Overall, the practical application of the Bi/ZIF HM-ICS in complicated samples was realized for detecting pesticide residue, and expanding its application scope in monitoring environment.

"Lighting-up" methylene blue-embedded zirconium based organic framework triggered by Al3+ for advancing the sensitivity of E. coli O157:H7 analysis in dual-signal lateral flow immunochromatographic assay.

The sensitive detection of foodborne pathogens is of great significance for ensuring food safety and quality. Herein, on the basis of methylene blue-embedded zirconium based organic framework (UIO@MB) as the remarkable capture carrier and signal indicator, with the Al3+-assisted the fluorescent signal response, we developed a label-free and dual-signal lateral flow immunochromatographic assay (LDLFIA) for sensitive detection of Escherichia coli (E. coli) O157:H7. The UIO@MB sensing carrier without monoclonal antibodies (mAbs) was manufactured, which adhered to bacteria to form the UIO@MB-E. coli O157:H7 conjugate, resulting in visible blue band. Then the fluorescent response of the OH-rich UIO@MB was excited by introducing Al3+, arising from capturing of Al3+ by -OH through coordination and electrostatic affinity, thus generating a green fluorescent band. Impressively, a smartphone-based portable reading system was developed that can reflect the test results of UIO@MB-LDLFIA immediately. Under optimum conditions, UIO@MB-LDLFIA can complete colorimetric and fluorescent mode detection within 90 min, with a detection sensitivity of 103 CFU/mL, which were 100 times lower than traditional gold nanoparticles-based LFIA and polymerase chain reaction (PCR). Moreover, the feasibility of the method was further evaluated by the determination of E. coli O157: H7 in drinking water and cabbage with average recoveries of 85.1-123.0%.

Well-orientation strategy for direct binding of antibodies: Development of the immunochromatographic test using the antigen modified Fe2O3 nanoprobes for sensitive detection of aflatoxin B1.

One of the major concerns in the application of nanocarriers in biosensing is the impair of the recognition molecules bioactivity loaded on their surfaces due to harsh and laborious cross-linking and random orientation, resulting in unsatisfactory sensitivity. Herein, we proposed a novel immunochromatographic test strip (FNS-ag-DICTS) by taking advantage of the antigen (ag) modified Fe2O3 nanostructures (FNSs) as new signal tags and goat anti-mouse IgG labeling on the detection line instead of ag, which was used for sensitive detection of aflatoxin B1 (AFB1). The fabricated FNS-ag can orientate the Fab region of monoclonal antibodies (mAbs), waiving the intrinsic limitations of traditional nanomaterials labeled mAbs. Under optimal conditions, FNS-ag-DICTS possessed excellent specificity and a wide detection range, with a visual limit of detection (vLOD) of 0.0125 ng mL-1. In addition, the biosensor successfully detected AFB1 in peanut, green bean and corn, with an average recovery rate of 82.8-124.9%.

Immunochromatographic Assay Based on Polydopamine-Decorated Iridium Oxide Nanoparticles for the Rapid Detection of Salbutamol in Food Samples.

Salbutamol (SAL), a ß-2 adrenoreceptor agonist, is an unpopular addition to livestock and poultry, causing several side effects to human health. Thus, it is very important to develop a simple and rapid analytical method to screen SAL in the field of food safety. Here, we present an immunochromatographic assay (ICA) method for sensitively detecting SAL with polydopamine-decorated iridium oxide nanoparticles (IrO2@PDA NPs) as a signal tag. The IrO2@PDA with excellent hydrophilicity, biocompatibility, and stability was synthesized by oxidating self-polymerization of dopamine hydrochloride (DAH) on the surface of IrO2 NPs and used to label monoclonal antibodies (mAbs) through simple physical adsorption. Compared with IrO2 NPs, the IrO2@PDA also possessed superior optical properties and higher affinity with mAbs. With the proposed method, the limit of detection for SAL was 0.002 ng/mL, which was improved at least 24-fold and 180-fold compared with the IrO2 NPs-based ICA and conventional gold nanoparticles-based ICA, respectively. Furthermore, the SAL residuals in pork, pork liver, and beef were successfully detected by the developed biosensor and the recoveries ranged from 85.56% to 115.56%. Briefly, this work indicated that the powerful IrO2@PDA-based ICA can significantly improve detection sensitivity and has huge potential for accurate and sensitive detection of harmful small molecules analytes in food safety fields.

Multifunctional bacteria-derived tags for advancing immunoassay analytical performance with dual-channel switching and antibodies bioactivity sustaining.

Constructing multifunctional immunochromatographic assays (ICA) carriers with multiple signals and retaining bioactivity of monoclonal antibodies (mAbs) are conducive to the sensitive and accurate point-of-care testing (POCT). To fulfill this pressing need, a microorganism-based microsphere mediated dual-modal ICA (DICA) was developed for sensitive and reliable detection of zearalenone (ZEN). As the key to the biosensor, a superb biotag with an intact coccus morphology was designed based on Staphylococcus aureus biosynthesized quantum dots incorporating Ru(bpy)32+ (SAQDsRu), in which SA offered a specific recognition capacity for Fc region of mAbs, QDs endowed a naked-eye discernible colorimetric signal on the SA, and robust fluorescence signal that remedied for the insufficient brightness of QDs was derived from Ru(bpy)32+. The characterization of SAQDsRu-labeled mAb (SAQDsRu-mAb) probe demonstrated strong luminescence, excellent stability and high affinity with ZEN (affinity constant was approximately 1.723 × 109 M-1), which can significantly improve the detection sensitivity. Impressively, a portable sensing system was developed by the integration of SAQDsRu-DICA with a smartphone-based readout. After optimization, this DICA indicated a limit of detection reaching down to 0.008 ng/mL (colorimetric mode) and 0.0058 ng/mL (fluorescent mode), which were much lower than that of conventional gold nanoparticles-based ICA (0.1029 ng/mL), possessing favorable specificity and repeatability (relative standard deviation (RSD) < 10%). Moreover, the feasibility of the immunoassay was further assessed by measuring ZEN in real samples with satisfactory recoveries, and the results are good consistent with liquid chromatography tandem mass spectrometry (LC-MS/MS).

An innovative prussian blue nanocubes decomposition-assisted signal amplification strategy suitable for competitive lateral flow immunoassay to sensitively detect aflatoxin B1.

A prussian blue nanocubes decomposition-assisted signal amplification strategy for competitive lateral flow immunoassay (PBNCD-SALFIA) was innovatively proposed to analyze aflatoxin B1 (AFB1) in foodstuffs. The signal was amplified on account of the PBNCs can degrade and fade under alkaline condition, which could weak the color of the test- and control-lines, thereby improving the sensitivity of the sensor. The strategy was technically-simple, just using NaOH as an amplifier can realize signal amplification in the competition assay. Under optimized conditions, the enhanced strip exhibited excellent specificity and sensitivity in AFB1 monitoring with a detection limit of 23 pg/mL, which was approximately 4- and 8-folds lower than those of PBNCs-LFIA (90 pg/mL) and conventional gold nanoparticles-LFIA (175 pg/mL), respectively. Taking the advantage of the color-fading, this platform revealing the lowest detectable concentration of 0.184, 0.368 and 0.184 µg/kg for AFB1 in corn, peanut and pumpkin seed within 58 min, separately, showing reliable results.

Gold nanoparticles-functionalized three-dimensional flower-like manganese dioxide: A high-sensitivity thermal analysis immunochromatographic sensor.

A sensitive photothermal immunochromatographic test strip (PITS) for the detection of deoxynivalenol (DON) was developed using flower-like gold nanoparticle-deposited manganese dioxide nanocarrier (FMD-G NC) labeled antibodies (Abs) as the photothermal-sensing probe. FMD was used as a template to deposit small gold nanoparticles (GNPs) to synthesize FMD-G NC with large specific surface area and significant photothermal conversion property. The FMD-G-Ab probe was competitively captured by DON target and antigen coated on test line (T-line), forming colorimetric signals under naked eyes and photothermal signals under an 808 nm laser. Under optimal conditions, the PITS exhibited sensitive and specific detection of DON from 0.19 ng mL-1 to 12 ng mL-1 with detection limits of 0.013 ng mL-1, which were over 15-fold and 58-fold more sensitive than visual FMD-G-ITS and traditional GNPs-ITS. In addition, the novel FMD-G-PITS possessed a universal applicability, which could be well applied in green bean, corn, and millet.

A novel colorimetric and fluorometric probe for biothiols based on MnO2 NFs-Rhodamine B system.

Herein, a novel bimodal ratiometric probe for sensitive and selective detection of biothiols (including glutathione (GSH), cysteine (Cys) and homocysteine (Hcys)) was constructed, which was based on the redox reaction between manganese dioxide nanoflakes (MnO2 NFs) and rhodamine (RhB) and biothiols. When MnO2 NFs was added into RhB solution, RhB was oxidized to a series of derivatives, accompanying with the colorimetric color changing from purple to light pink and fluorescence changing from red to green. In the presence of GSH, Cys or Hcys, they could reduce MnO2 NFs to Mn2+, thereby preventing the following oxidization of RhB and the corresponding color and fluorescence changes. The absorption intensity ratio and fluorescence intensity ratio showed good linear relationships with the concentrations of biothiols. The colorimetric detection limits for GSH, Cys and Hcys were 0.057 µM, 0.140 µM and 0.087 µM, respectively. And the fluorescence detection limits were 0.177 µM, 0.282 µM and 0.161 µM. More importantly, this probe was successfully applied to monitor the concentration of GSH/Cys/Hcys in human serum samples, with satisfactory recovery. Thus, this MnO2 NFs-RhB platform can potentially be a candidate for the detection of biothiols.