Janus plasmonic-aggregation induced emission nanobeads as high-performance colorimetric-fluorescent probe of immunochromatographic assay for the ultrasensitive detection of staphylococcal enterotoxin B in milk.

Herein, a colorimetric-fluorescent hybrid bifunctional nanobead with Janus structure (J-cf-HBN) was synthesized via one-pot microemulsification. Oleylamine-coated AuNPs and aggregation-induced emission luminogens (AIEgens) were suggested as building blocks to obtain high-performance colorimetric-fluorescent signals. The as-prepared J-cf-HBNs were used as a signal amplification probe to construct an immunochromatographic assay (J-cf-HBNs-ICA) platform for the ultrasensitive detection of staphylococcal enterotoxin B (SEB) in milk samples. Owing to the rational spatial distribution of AuNPs and AIEgens, the J-cf-HBNs present a highly retained photoluminescence and enhanced colorimetric signals. Combined with a pair of highly affinitive anti-SEB antibodies, the J-cf-HBN-ICA platform enabled the fast naked-eye visualization and fluorescent quantitative detection of SEB in various milk matrices. Given the advantages of the dual-mode high-performance J-cf-HBNs, the proposed strip achieved a high sensitivity for SEB qualitative determination with a visual limit of detection (LOD) of 1.56 ng mL-1 and exhibited ultrasensitivity for SEB quantitative detection with a LOD of 0.09 ng mL-1, which is 139-fold lower than that of ELISA using same antibodies. In conclusion, this work provides new insights into the construction of multimode immunochromatographic methods for food safety detection in the field.

Metabolic Regulation of Endothelial Cells: A New Era for Treating Wet Age-Related Macular Degeneration.

Wet age-related macular degeneration (wet AMD) is a primary contributor to visual impairment and severe vision loss globally, but the prevailing treatments are often unsatisfactory. The development of conventional treatment strategies has largely been based on the understanding that the angiogenic switch of endothelial cells (ECs) is mainly dictated by angiogenic growth factors. Even though treatments targeting vascular endothelial growth factor (VEGF), like ranibizumab, are widely administered, more than half of patients still exhibit inadequate or null responses, suggesting the involvement of other pathogenic mechanisms. With advances in research in recent years, it has become well recognized that EC metabolic regulation plays an active rather than merely passive responsive role in angiogenesis. Disturbances of these metabolic pathways may lead to excessive neovascularization in angiogenic diseases such as wet AMD, therefore targeted modulation of EC metabolism represents a promising therapeutic strategy for wet AMD. In this review, we comprehensively discuss the potential applications of EC metabolic regulation in wet AMD treatment from multiple perspectives, including the involvement of ECs in wet AMD pathogenesis, the major endothelial metabolic pathways, and novel therapeutic approaches targeting metabolism for wet AMD.

Novel therapeutic perspectives for wet age-related macular degeneration: RGD-modified liposomes loaded with 2-deoxy-D-glucose as a promising nanomedicine.

Choroidal neovascularization (CNV), characterized as a prominent feature of wet age-related macular degeneration (AMD), is a primary contributor to visual impairment and severe vision loss globally, while the prevailing treatments are often unsatisfactory. The development of conventional treatment strategies has largely been based on the understanding that the angiogenic switch of endothelial cells is dictated by angiogenic growth factors alone. Even though treatments targeting vascular endothelial growth factor (VEGF), like Ranibizumab, are widely administered, more than half of the patients still exhibit inadequate or null responses, emphasizing the imperative need for solutions to this problem. Here, aiming to explore therapeutic strategies from a novel perspective of endothelial cell metabolism, a biocompatible nanomedicine delivery system is constructed by loading RGD peptide-modified liposomes with 2-deoxy-D-glucose (RGD@LP-2-DG). RGD@LP-2-DG displayed good targeting performance towards endothelial cells and excellent in vitro and in vivo inhibitory effects on neovascularization were demonstrated. Moreover, our mechanistic studies revealed that 2-DG interfered with N-glycosylation, leading to the inhibition of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream signaling. Notably, the remarkable inhibitory effect on neovascularization and biocompatibility of RGD@LP-2-DG render it a highly promising and clinically translatable therapeutic candidate for the treatment of wet AMD and other angiogenic diseases, particularly in patients who are unresponsive to currently available treatments.

A Ligand-Directed Spatial Regulation to Structural and Functional Tunability in Aggregation-Induced Emission Luminogen-Functionalized Organic-Inorganic Nanoassemblies.

Aggregation-induced emission luminogen (AIEgen)-functionalized organic-inorganic hybrid nanoparticles (OINPs) are an emerging category of multifunctional nanomaterials with vast potential applications. The spatial arrangement and positioning of AIEgens and inorganic compounds in AIEgen-functionalized OINPs determine the structures, properties, and functionalities of the self-assembled nanomaterials. In this work, a facile and general emulsion self-assembly tactic for synthesizing well-defined AIEgen-functionalized OINPs is proposed by coassembling alkane chain-functionalized inorganic nanoparticles with hydrophobic organic AIEgens. As a proof of concept, the self-assembly and structural evolution of plasmonic-fluorescent hybrid nanoparticles (PFNPs) from concentric circle to core shell and then to Janus structures is demonstrated by using alkane chain-modified AuNPs and AIEgens as building blocks. The spatial position of AuNPs in the signal nanocomposite is controlled by varying the alkane ligand length and density on the AuNP surface. The mechanism behind the formation of various PFNP nanostructures is also elucidated through experiments and theoretical simulation. The obtained PFNPs with diverse structures exhibit spatially tunable optical and photothermal properties for advanced applications in multicolor and multimode immunolabeling and photothermal sterilization. This work presents an innovative synthetic approach of constructing AIEgen-functionalized OINPs with diverse structures, compositions, and functionalities, thereby championing the progressive development of these OINPs.

Aggregation-induced emission nanoparticles facilitating multicolor lateral flow immunoassay for rapid and simultaneous detection of aflatoxin B1 and zearalenone.

Herein we developed a multicolor lateral flow immunoassay (LFIA) test strip for rapid and simultaneous quantitative detection of aflatoxin B1 (AFB1) and zearalenone (ZEN). Three differently colored aggregation-induced emission nanoparticles (AIENPs) were designed as LFIA signal tags, with red and green AIENPs for targeting AFB1 and ZEN at the test line, and yellow AIENPs for indicating the validity of the test strip at the control (C) line. After surface functionalization with antibodies, the developed AIENP-based multicolor LFIA allows simultaneous and accurate quantification of AFB1 and ZEN using an independent C-line assisted ratiometric signal output strategy. The detection limits of AFB1 and ZEN were 6.12 and 26 pg/mL, respectively. The potential of this method for real-world applications was well demonstrated in corn and wheat. Overall, this multicolor LFIA shows great potential for field screening of multiple mycotoxins and can be extended to rapid and simultaneous monitoring of other small molecule targets.

Aggregation-Induced Emission (AIE), Life and Health.

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Aggregation-Induced Emission Luminogen-Encapsulated Fluorescent Hydrogels Enable Rapid and Sensitive Quantitative Detection of Mercury Ions.

Hg2+ contamination in sewage can accumulate in the human body through the food chains and cause health problems. Herein, a novel aggregation-induced emission luminogen (AIEgen)-encapsulated hydrogel probe for ultrasensitive detection of Hg2+ was developed by integrating hydrophobic AIEgens into hydrophilic hydrogels. The working mechanism of the multi-fluorophore AIEgens (TPE-RB) is based on the dark through-bond energy transfer strategy, by which the energy of the dark tetraphenylethene (TPE) derivative is completely transferred to the rhodamine-B derivative (RB), thus resulting in intense photoluminescent intensity. The spatial networks of the supporting hydrogels further provide fixing sites for the hydrophobic AIEgens to enlarge accessible reaction surface for hydrosoluble Hg2+, as well create a confined reaction space to facilitate the interaction between the AIEgens and the Hg2+. In addition, the abundant hydrogen bonds of hydrogels further promote the Hg2+ adsorption, which significantly improves the sensitivity. The integrated TPE-RB-encapsulated hydrogels (TR hydrogels) present excellent specificity, accuracy and precision in Hg2+ detection in real-world water samples, with a 4-fold higher sensitivity compared to that of pure AIEgen probes. The as-developed TR hydrogel-based chemosensor holds promising potential as a robust, fast and effective bifunctional platform for the sensitive detection of Hg2+.

Highly Sensitive Immunochromatographic Detection of Zearalenone Based on Ultrabright Red-Emitted Aggregation-Induced Luminescence Nanoprobes.

Highly luminescent nanospheres have been demonstrated in enhancing the sensitivity of lateral flow immunoassay (LFIA) due to their loading numerous luminescent dyes. However, the photoluminescence intensities of existing luminescent nanospheres are limited due to the aggregation-caused quenching effect. Herein, highly luminescent aggregation-induced emission luminogens embedded nanospheres (AIENPs) with red emission were introduced as signal amplification probes of LFIA for quantitative detection of zearalenone (ZEN). Optical properties of red-emitted AIENPs were compared with time-resolved dye-embedded nanoparticles (TRNPs). Results showed that red-emitted AIENPs have stronger photoluminescence intensity on the nitrocellulose membrane and superior environmental tolerance. Additionally, we benchmarked the performance of AIENP-LFIA against TRNP-LFIA using the same set of antibodies, materials, and strip readers. Results showed that AIENP-LFIA exhibits good dynamic linearity with the ZEN concentration from 0.195 to 6.25 ng/mL, with half competitive inhibitory concentration (IC50) and detection of limit (LOD) at 0.78 and 0.11 ng/mL, respectively. The IC50 and LOD are 2.07- and 2.36-fold lower than those of TRNP-LFIA. Encouragingly, the precision, accuracy, specificity, practicality, and reliability of this AIENP-LFIA for ZEN quantitation were further characterized. The results verified that the AIENP-LFIA has good practicability for the rapid, sensitive, specific, and accurate quantitative detection of ZEN in corn samples.

Ultrabright orange-yellow aggregation-induced emission nanoparticles for highly sensitive immunochromatographic quantification of ochratoxin A in corn.

Herein, we report a novel aggregation-induced emission nanoparticles (AIENPs)-based immunochromatography assay (ICA) platform to detect ochratoxin A (OTA) using orange-yellow-emitting AIENPs as fluorescent nanoprobes. Immunochromatographic strip is used for the quantitative detection of OTA in crop matrix using AIENPs coupled with anti-OTA ascites. Under optimal conditions, AIENPs-ICA exhibits stronger signal output capacity and higher sensitivity than traditional gold nanoparticles-based ICA. The half-maximal inhibitory concentration is as low as 0.149 ng mL-1, and the limit detection is 0.042 ng mL-1 at 10 % competitive inhibition concentration. The average recovery of AIENPs-ICA ranges from 82.60 % to 113.14 % with the coefficient of variation ranging from 1.26 % to 11.57 %, proving the proposed method possesses good reliability and reproducibility. Moreover, the developed AIENPs-ICA exhibits negligible cross-reactions with other mycotoxins. We believe the presented AIENPs-ICA platform holds promising potential as a powerful tool for on-site detection of OTA and other molecules detection in food samples.

Aggregation-Induced Red Emission Nanoparticle-Based Lateral Flow Immunoassay for Highly Sensitive Detection of Staphylococcal Enterotoxin A.

Staphylococcal enterotoxin A (SEA) has presented enormous difficulties in dairy food safety and the sensitive detection of SEA provides opportunities for effective food safety controls and staphylococcal food poisoning tracebacks. Herein, a novel aggregation-induced emission (AIE)-based sandwich lateral flow immunoassay (LFIA) was introduced to detect SEA by using red-emissive AIE nanoparticles (AIENPs) as the fluorescent nanoprobe. The nanoprobe was constructed by directly immobilising antibodies on boronate-tagged AIENPs (PBA-AIENPs) via a boronate affinity reaction, which exhibited a high SEA-specific affinity and remarkable fluorescent performance. Under optimal conditions, the ultrasensitive detection of SEA in pasteurised milk was achieved within 20 min with a limit of detection of 0.04 ng mL-1. The average recoveries of the PBA-AIENP-LFIA ranged from 91.3% to 117.6% and the coefficient of variation was below 15%. It was also demonstrated that the PBA-AIENP-LFIA had an excellent selectivity against other SE serotypes. Taking advantage of the excellent sensitivity of this approach, real chicken and salad samples were further analysed, with a high versatility and accuracy. The proposed PBA-AIENP-LFIA platform shows promise as a potent tool for the identification of additional compounds in food samples as well as an ideal test method for on-site detections.

Advantages of aggregation-induced luminescence microspheres compared with fluorescent microspheres in immunochromatography assay with sandwich format.

Organic fluorescein dye-embedded fluorescent microspheres (FMs) are currently the most established commercially fluorescent markers, and they have been widely used to improve the sensitivity of immunochromatography assay (ICA). However, these FMs have natural defects, such as the aggregation-caused quenching effect and small Stokes shift, which are not conducive to improving the detection performance of ICA. Herein, two green emitted FMs, namely aggregation-induced emission FMs (AIEFMs) and fluorescein isothiocyanate FMs (FITCFMs), were prepared by swelling the AIE luminogens and FITC dyes into the carboxyl group-modified polystyrene microspheres. The average diameters of AIEFMs and FITCFMs were 350 and 450 nm, respectively. Compared with FITCFMs, the AIEFMs exhibited stronger fluorescence intensity and a larger Stokes shift. These two FMs were used as the labeling markers of ICA for procalcitonin (PCT) detection with the sandwich format. Among them, AIEFM-ICA showed dynamic linear detection of PCT from 7.6 pg mL-1 to 125 ng mL-1 with the limit of detection (LOD) at 3.8 pg mL-1. These values were remarkably superior to those of FITCFM-ICA (linear range from 61 pg mL-1 to 62.5 ng mL-1 and LOD value at 60 pg mL-1). Furthermore, the average recoveries of the intra- and inter-assays of AIEFM-ICA ranged from 86% to 112%, with coefficients of variation ranging from 1.2% to 8.8%, indicating accuracy and precision for PCT quantitative detection. Additionally, the reliability of the developed AIEFM-ICA was further assessed by analyzing 30 real serum samples from systemic inflammatory response by infectious diseases, and the results showed good agreement with the chemiluminescence immunoassay. In conclusion, compared with traditional FITCFMs, green emitted AIEFMs as a novel fluorescent label, exhibits greater potential to enhance the detection performance of the ICA platform.

High-performance green-emitting AIE nanoparticles for lateral flow immunoassay applications.

Ultrabright green-emissive AIE nanoparticles (AIENPs) were used as signal-amplification probes to enhance the detectability of lateral flow immunoassay (LFIA). The detection performances of the green-emissive AIENP probes in both sandwich and competitive LFIA formats were systematically evaluated. Benefiting from its remarkable fluorescent brightness, the developed AIENP-LFIA showed versatile applicability for the detection of small molecules and macromolecules by using ochratoxin A (OTA) and procalcitonin (PCT) as model analytes, respectively. Under the optimum conditions, the detection limits (LODs) of the fabricated AIENP-LFIA for OTA and PCT were 0.043 ng mL-1 and 0.019 ng mL-1, respectively. These LOD values are significantly lower than those of conventional LFIA methods using gold nanoparticles as signal reporters. In addition, we demonstrated the practical application potential of AIENP-LFIA for the detection of OTA in real maize samples and PCT in real serum samples. These results indicated that the ultrabright green-emissive AIENPs were promising as signal output materials for building high-performance LFIA platform and broadening the application scenarios of LFIA.

Ultrasensitive Lateral Flow Immunoassay for Fumonisin B1 Detection Using Highly Luminescent Aggregation-Induced Emission Microbeads.

Lateral flow immunoassay (LFIA) based on fluorescent microbeads has attracted much attention for its use in rapid and accurate food safety monitoring. However, conventional fluorescent microbeads are limited by the aggregation-caused quenching effect of the loaded fluorophores, thus resulting in low signal intensity and insufficient sensitivity of fluorescent LFIA. In this study, a green-emitting fluorophore with an aggregation-induced emission (AIE) characteristic was encapsulated in polymer nanoparticles via an emulsification technique to form ultrabright fluorescent microbeads (denoted as AIEMBs). The prepared AIEMBs were then applied in a competitive LFIA (AIE-LFIA) as signal reporters for the rapid and highly sensitive screening of fumonisin B1 (FB1) in real corn samples. High sensitivity with a detection limit of 0.024 ng/mL for FB1 was achieved by the developed AIE-LFIA. Excellent selectivity, good accuracy, and high reliability of the AIE-LFIA were demonstrated, indicating a promising platform for FB1 screening.

Quantum dot bead-based competitive immunochromatographic assay for enterotoxin aureus A detection in pasteurized milk.

Staphylococcal enterotoxin A (SEA) is an important biotoxin, produced by Staphylococcus aureus under appropriate conditions, and often contaminates milk and dairy products. Herein, an anti-SEA monoclonal antibody (anti-SEA mAb) was prepared by injecting the SEA protein in BALB/c mice, and a novel immunochromatographic assay (ICA) was developed for the rapid and sensitive determination of SEA in pasteurized milk by using highly luminescent quantum dot beads (QB) as signal amplification probe. Given the 1020-fold enhancement in the photoluminescence intensity of QB to the original quantum dot, the proposed QB-ICA exhibits high sensitivity for SEA determination in real milk samples with a limit of detection of 1.89 ng/mL, and shows good dynamic linearity for SEA quantitative detection from 2 to 150 ng/mL within 15 min of test time. The proposed QB-ICA also shows good selectivity to SEA detection with a negligible cross-reaction to common analogs, including staphylococcal enterotoxins B, C, D, and E. In addition, the accuracy and precision of QB-ICA were assessed by analyzing SEA-fortified milk samples. The average recoveries of intra- and interassays range from 85.5 to 128.1%, and the coefficients of variation range from 4.6 to 14.2%, indicating an acceptable accuracy for the quantitative detection of SEA in real milk samples. In summary, this work provides a powerful and rapid analysis tool for the sensitive monitoring of SEA contamination in pasteurized milk samples.

Ratiometric Monitoring of Biogenic Amines by a Simple Ammonia-Response Aiegen.

Herein, we developed a paper-based smart sensing chip for the real-time, visual, and non-destructive monitoring of food freshness using a ratiometric aggregation-induced emission (AIE) luminogen (i.e., H+MQ, protonated 4-(triphenylamine)styryl)quinoxalin-2(1H)-one) as pH sensitive indicators. Upon exposure to amine vapors, the deprotonation of H+MQ occurs and triggers its color change from blue to yellow, with the fluorescence redshift from blue to amaranth. Consequently, we successfully achieved the sensitive detection of ammonia vapors by recording the bimodal color and fluorescence changes. Given the high sensitivity of H+MQ to ammonia vapor, a paper-based smart sensor chip was prepared by depositing H+MQ on the commercial qualitative filter paper through a physical deposition strategy. After being placed inside the sealed containers, the developed H+MQ-loaded paper chip was applied to the real-time monitoring of biogenic amine contents according to its color difference and ratio fluorescence change. The detection results were further compared with those obtained by the high-performance liquid chromatography method, which verified the feasibility of the designed paper chip for the food spoilage degree evaluation. Briefly, this work indicates that the designed H+MQ-loaded paper chip could be a promising approach for improving food freshness monitoring.

Avoiding the self-nucleation interference: a pH-regulated gold in situ growth strategy to enable ultrasensitive immunochromatographic diagnostics.

Background: Gold nanoparticle-based immunochromatographic assay (AuNP-ICA) has insufficient sensitivity due to its inherent colorimetric signal intensity and low capture efficiency of AuNPs. The metal in situ growth is a common strategy to enhance the sensitivity of AuNP-ICA due to its superior signal amplification potential and simple operation. However, the detection distortion caused by metal self-nucleation during the growth process can seriously affect the accuracy and reproducibility of the strips. Methods: We present a pH-regulated gold in situ growth (GISG) strategy to amplify the colorimetric signal and demonstrate its application in improving the performance of traditional AuNP-ICA. The controllable growth signal amplification is achieved by lowering the pH of the growth solution to weaken the reducibility of hydroxylamine (HA), thus urging the crystallization and growth of Au3+ on the AuNP surface instead of free reduction and self-nucleation. In addition, the mechanism of pH regulation on HA reducibility is elucidated by introducing an electron-donating or electron-withdrawing group to affect the electron density of hydroxyl group. Results: The proposed GISG strategy shows improved sensitivity, low background, robust operation, and good reproducibility. The LOD values of the designed GISG-amplified AuNP-ICA are as low as 0.0198 ng mL-1 for hepatitis B surface antigen and 0.0125 ng mL-1 for HIV-1 capsid p24 antigen, which are lower by about 500- and 70-fold, respectively, than those of the unamplified AuNP-ICA. Conclusions: This method is extended to enable ultrasensitive and rapid diagnosis of viral infections, and has potential as a general signal amplification platform to redefine immunochromatographic diagnostics.

"Three-in-One" Multifunctional Nanohybrids with Colorimetric Magnetic Catalytic Activities to Enhance Immunochromatographic Diagnosis.

Colorimetric lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters has been widely used in point-of-care testing. Nonetheless, the potential of traditional AuNP-based LFIA for the early diagnosis of disease is often compromised by limited sensitivity due to the insufficient colorimetric signal brightness of AuNPs. Herein, we develop a "three-in-one" multifunctional catalytic colorimetric nanohybrid (Fe3O4@MOF@Pt) composed of Fe3O4 nanoparticles, MIL-100(Fe), and platinum (Pt) nanoparticles. Fe3O4@MOF@Pt displays enhanced colorimetric signal brightness, fast magnetic response, and ultrahigh peroxidase-mimicking activity, which are beneficial to the enhancement of the sensitivity of LFIA by coupling with magnetic separation and catalytic amplification. When integrated with the dual-antibody sandwich LFIA platform, the developed Fe3O4@MOF@Pt can achieve an ultrasensitive immunochromatographic assay of procalcitonin with a sensitivity of 0.5 pg mL-1, which is approximately 2280-fold higher than that of conventional AuNP-based LFIA and superior to previously published immunoassays. Therefore, this work suggests that the proposed catalytic colorimetric nanohybrid can act as promising signal reporters to enable ultrasensitive immunochromatographic disease diagnostics.

Tailoring noble metal nanoparticle designs to enable sensitive lateral flow immunoassay.

Lateral flow immunoassay (LFIA) with gold nanoparticles (AuNPs) as signal reporters is a popular point-of-care diagnostic technique. However, given the weak absorbance of traditional 20-40 nm spherical AuNPs, their sensitivity is low, which greatly limits the wide application of AuNP-based LFIA. With the rapid advances in materials science and nanotechnology, the synthesis of noble metal nanoparticles (NMNPs) has enhanced physicochemical properties such as optical, plasmonic, catalytic, and multifunctional activity by simply engineering their physical parameters, including the size, shape, composition, and external structure. Using these engineered NMNPs as an alternative to traditional AuNPs, the sensitivity of LFIA has been significantly improved, thereby greatly expanding the working range and application scenarios of LFIA, particularly in trace analysis. Therefore, in this review, we will focus on the design of engineered NMNPs and their demonstration in improving LFIA. We highlight the strategies available for tailoring NMNP designs, the effect of NMNP engineering on their performance, and the working principle of each engineering design for enhancing LFIA. Finally, current challenges and future improvements in this field are briefly discussed.

Gold Nanobeads with Enhanced Absorbance for Improved Sensitivity in Competitive Lateral Flow Immunoassays.

BACKGROUND: Colloidal gold based lateral flow immunoassay (LFIA) commonly suffers from relatively low detection sensitivity due to the insufficient brightness of conventional gold nanoparticles (AuNPs) with the size of 20-40 nm. METHODS: Herein, three kinds of gold nanobeads (GNBs) with the size of 94 nm, 129 nm, and 237 nm, were synthesized by encapsulating numerous hydrophobic AuNPs (10 nm) into polymer matrix. The synthesized GNBs exhibited the enhanced colorimetric signal intensity compared with 20-40 nm AuNPs. The effects of the size of GNBs on the sensitivity of LFIA with competitive format were assessed. RESULTS: The results showed that the LFIA using 129 nm GNBs as amplified signal probes exhibits the best sensitivity for fumonisin B1 (FB1) detection with a cut-off limit (for visual qualitative detection) at 125 ng/mL, a half maximal inhibitory concentration at 11.27 ng/mL, and a detection limit at 1.76 ng/mL for detection of real corn samples, which are 8-, 3.82-, and 2.89-fold better than those of conventional AuNP40-based LFIA, respectively. The developed GNB-LFIA exhibited negligible cross-reactions with other common mycotoxins. In addition, the accuracy, precision, reliability, and practicability were demonstrated by determining real corn samples. CONCLUSIONS: All in all, the proposed study provides a promising strategy to enhance the sensitivity of competitive LFIA via using the GNBs as amplified signal probes.

Hydrazide-assisted directional antibody conjugation of gold nanoparticles to enhance immunochromatographic assay.

The analytical performance of immunochromatographic assay (ICA) is usually determined by the biological activity of antibody and gold nanoparticle conjugates (AuNP probes). However, conventional probes are constructed using the nondirectional coupling method that can cause the improper orientation of antibodies with the poor accessibility of antigen-binding sites. To address these issues, we report a site-specific directional coupling strategy to enhance the bioactivity of AuNP probes through the specific covalent binding of the aldehyde group in the Fc domain of antibodies with the hydrazide group modified on the surface of AuNPs. Through this design, the antibodies can be erected on the AuNP surface to fully expose the Fab domain and achieve the maximized functional availability. Leveraging these AuNP probes as ICA labels, we demonstrate an improved detection of the hepatitis B surface antigen with less used amount of labeled antibody (0.2 mg/pmol AuNPs), shorter reaction time (10 min), better antibody bioactivity, and higher detection sensitivity (2 ng/mL) compared with the carbodiimide method. Overall, this work provides great promise for the design and the construction of high-performance probes to enhance the detection performance of ICA sensors.