Ming Li

Improper use of vanillin as a food flavor additive presents a potential threat, and its effective supervision is therefore essential. Rapid biosensing is a beneficial supplementary or alternative strategy for current detection methods. Two modes of immunochromatographic assay (ICA) strips, based on gold nanoparticles (GNP) and fluorescent microparticles (FMP) labeled with a monoclonal antibody against vanillin, were separately assembled to obtain a GICA strip and an FICA strip for the detection of vanillin. The colorimetric/fluorescence signals of the strips were directly judged for semi-quantification by the naked eye and then digitally quantified by strip readers. The GICA demonstrated a linear range of 15.6–500 ng/mL, having a limit of detection (LOD) of 10.3 ng/mL. For the FICA strip, the enhanced sensitivity achieved an LOD value as low as 2.04 ng/mL and showed a linear range between 3.12 ng/mL and 200 ng/mL, representing a 5-fold improvement over the GICA strip. The two modes of ICA strips all had high specificity, stability, accuracy and precision for on-site vanillin detection within 10 min. For vanillin levels in authentic food product samples, the results were well correlated with the measurements obtained via the referenced ELISA and HPLC methods. The results indicated that two modes of ICA strips were capable of rapid, sensitive, on-site, semi-quantitative and quantitative detection of vanillin in food products, ultimately guaranteeing food safety and consumer health.

Ochratoxin A (OTA) is a highly toxic mycotoxin prevalent in agricultural samples. In order to overcome the limitations of traditional detection methods, this study developed a rapid visual detection system based on deep learning by optimizing the YOLOv5 algorithm. Through integrating attention mechanism to enhance color feature extraction and employing dilated convolutions to expand the receptive field, the proposed Efficient-YOLOv5 algorithm significantly improved the accuracy of OTA concentration identification. Comparative experiments demonstrated the superior performance of Efficient-YOLOv5, with mean average precision (mAP) increasing from 92.86% to 97.65%, precision from 93.34% to 95.73%, recall from 91.67% to 92.68%, and F1-score from 90.34% to 91.69%. Validation on real agricultural samples further confirmed the high accuracy of the method, yielding a detection error of 0.04 compared to standard concentration and 0.25% under simulated scenarios. The optimized loss function achieved a mAP value of 91.37%, precision of 91.86%, and F1-score of 88.26%, highlighting its efficiency, accuracy and high-throughput potential. By combining visual data with deep learning, the proposed detection system offered a promising framework for the rapid, accurate and efficient identification and detection of OTA.

Portable and ultrasensitive biosensing was described for the rapid detection of targets, benefiting for the early warning and risk intervention. A Lab-in-Tip biosensing platform based on toehold-mediated strand displacement (TMSD) amplification and glucose oxidase (GOD)/Fe-PDs enzyme cascade strategy had integrated for dual-mode detection of target ochratoxin A (OTA). On the internal surface of pipette tip, the OTA-Apt@cDNA and T-DNA@DNA-GOD were immobilized to prepare micro workstation in advance. The prepared Fe-PDs nanozyme was employed in catalysis and used as substrate. When OTA was added in the micro workstation, the released cDNA might activate the powerful TMSD reaction and generated abundant DNA-GOD, and then introduced into the GOD/Fe-PDs enzyme cascade to reflect ultrasensitive dual-mode signals. The OTA could be identified via two optical signal modes: colorimetry (LOD of 0.24 pg/mL) and fluorescence (LOD of 0.074 pg/mL), demonstrating excellent sensitivity. The Lab-in-Tip biosensing exhibited several advantages, such as a notable pattern of micro workstation, high integration, dual-mode detection, ultrasensitivity and simplified operation. This proposed biosensing integrated GOD/Fe-PDs based colorimetric detection and fluorescence quenching based ”Turn-on” to ”Turn-off” detection, which may recommend valuable insights for the improvement of novel and portable detection pattern for other targets.

The widespread accumulation of ampicillin (AMP) poses significant ecological and health risks, demanding rapid and portable monitoring tools. Herein, a Fe-Ni bimetallic-doped polydopamine (FeNi@PDA) nanozyme with exceptional peroxidase-like activity was synthesized for the visual and on-site monitoring of AMP. Optimized through bimetallic electronic coupling, FeNi@PDA exhibited enhanced catalytic efficiency (K_M = 0.051 mmol/L for H₂O₂ and 0.049 mmol/L for 3,3′,5,5′-tetramethylbenzidine) and generated ¹O₂ and ·O₂⁻ via H₂O₂ activation. Leveraging the competitive consumption of reactive oxygen species (ROS) by electron-rich AMP, a colorimetry detection mode was developed where AMP concentration inversely correlated with oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB) formation. This strategy achieved a good linear relationship of between 0.05 to 100 μg/mL, with a limit of detection (LOD) of 10.38 ng/mL. Furthermore, a smartphone-integrated paper-based detection mode was fabricated by immobilizing FeNi@PDA on filter paper. The color gradient of test papers, analyzed via smartphone imaging, enabled on-site AMP quantification with a LOD of 340 ng/mL. This work not only developed a novel Fe-Ni bimetallic nanozyme with enhanced peroxidase-like activity and established a competitive ROS-consumption sensing mechanism but also pioneered a dual-mode detection platform for low-cost, user-friendly ampicillin monitoring in environmental samples.

The widespread accumulation of ampicillin (AMP) poses significant ecological and health risks, demanding rapid and portable monitoring tools. Herein, a Fe-Ni bimetallic-doped polydopamine (FeNi@PDA) nanozyme with exceptional peroxidase-like activity was synthesized for the visual and on-site monitoring of AMP. Optimized through bimetallic electronic coupling, FeNi@PDA exhibited enhanced catalytic efficiency (KM = 0.051 mmol/L for H₂O₂ and 0.049 mmol/L for TMB) and generated ¹O₂ and ·O₂- via H₂O₂ activation. Leveraging the competitive consumption of reactive oxygen species (ROS) by electron-rich AMP, a colorimetry detection mode was developed where AMP concentration inversely correlated with oxTMB formation. This strategy achieved good linear relationship between 0.05 to 100 μg/mL, with a limit of detection (LOD) of 10.38 ng/mL. Furthermore, a smartphone integrated paper-based detection mode was fabricated by immobilizing FeNi@PDA on filter paper. The color gradient of test papers, analyzed via smartphone imaging, enabled on-site AMP quantification with an LOD of 340 ng/mL. This work not only developed a novel Fe-Ni bimetallic nanozyme with enhanced peroxidase-like activity and established a competitive ROS-consumption sensing mechanism, but also pioneered a dual-mode detection platform for low-cost, user-friendly ampicillin monitoring in environmental samples.

Tetracycline (TC) pollution poses a severe threat to ecosystems and human health, thus urging the development of efficient detection and degradation methods. In this study, manganese nanocube single-atom catalysts (Mn-Cube SACs) with oxidase/peroxidase-like activities were prepared by tannic acid etching of ZIF-8 metal-organic frameworks (MOFs), and a bifunctional platform was further constructed for the synergistic sensitive detection and controllable degradation of TC. For detection, a colorimetric immunosensor for TC detection was established by combining Mn-Cube SACs with TC antigens and conjugating immunomagnetic bead (IMB) with TC antibodies, enabling magnetic separation. The proposed immunosensor achieved a remarkably low limit of detection (LOD) of 1.16 ng/mL with a linear range of 1.80-21.6 ng/mL, demonstrating a 5-fold enhancement in sensitivity compared to conventional ELISA. For degradation, the Mn-Cube SACs were leveraged for their excellent adsorption capacity and robust photocatalytic activity. Mn-Cube SACs displayed a maximum adsorption capacity of 233.3 mg/g toward TC via chemical adsorption, and under optimal conditions, achieved a 93.1% degradation efficiency within 2 hours. This work presents a versatile Mn-Cube SACs-based platform capable of both sensitive detection and efficient degradation of TC, which dual-functional platform will provide a foundation for developing multifaceted solutions against hazardous pollutants.