Dual-recognition detection of Staphylococcus aureus using vancomycin-functionalized magnetic beads as concentration carriers

Selection of affinity peptides for the purification potential of porcine circovirus type 2 (PCV2) Cap virus-like particles (VLPs)

In this study, we describe the use of a M13 phage-displayed random peptide library for screening novel peptide motifs that specifically recognize recombinant PCV2 Cap protein for the first time.

Sensitive detection of Listeria monocytogenes based on highly efficient enrichment with vancomycin-conjugated brush-like magnetic nano-platforms

Pathogens pose a significant threat to public health worldwide. Despite many technological advances in the rapid diagnosis of pathogens, sensitive pathogen detection remains challenging because target pathogenic bacteria usually exist in complex samples at very low concentrations. Here, the construction of multivalent brush-like magnetic nanoprobes and their application for the efficient enriching of pathogens are demonstrated. Brush-like magnetic nanoprobes were constructed by modification with poly-L-lysine (PLL) onto amino-modified magnetic beads, followed by coupling of PEG (amine-PEG₅₀₀₀-COOH) to the amine sites of PLL. Subsequently, vancomycin (Van), a small-molecule antibiotic with affinity to the terminal peptide (D-alanyl-D-alanine) on the cell wall of Gram-positive bacteria, was conjugated to the carboxyl of the PEG. The use of multivalent brush-like magnetic nanoprobes (Van-PEG-PLL-MNPs) results in a high enrichment efficiency (>94%) and satisfactory purity for Listeria monocytogenes (employed as a model) within 20min, even at bacterial concentrations of only 10²cfumL^-1. Integrated with the enrichment of the Van-PEG-PLL-MNP nano-platform and electrochemiluminescence (ECL) detection, Listeria monocytogenes can be rapidly and accurately detected at levels as low as 10cfumL^-1. The approach described herein holds great potential for realizing rapid and sensitive pathogen detection in clinical samples.

Multiplexed immunochromatographic test strip for time-resolved chemiluminescent detection of pesticide residues using a bifunctional antibody

A novel bifunctional antibody (BfAb) that could recognize methyl parathion and imidacloprid simultaneously was prepared by a hybrid hybridomas technique. Using the BfAb as the sole recognition reagent, a multiplexed immunochromatographic test strip based on a time-resolved chemiluminescence (CL) strategy was developed for quantitative detection of pesticide residues. Horseradish peroxidase (HRP) and alkaline phosphatase (ALP) were used as the CL probes to label the haptens of methyl parathion and imidacloprid, respectively. After the labeled haptens competed with methyl parathion and imidacloprid to bind with the BfAb immobilized on the test strip, the two CL reactions catalyzed by the enzymes were triggered simultaneously by coreactants injection. Due to the distinct CL kinetics characteristics of HRP and ALP, the signals for methyl parathion and imidacloprid detections were collected at 2.5s and 300s, respectively. The linear ranges for methyl parathion and imidacloprid were both 0.1-250ngmL^-1, with detection limits of 0.058ngmL^-1 (S/N=3). The whole assay process could be accomplished within 22min. The detection results for spiked traditional Chinese medicine samples demonstrated its application potential. The proposed method provided a low-cost, facile and rapid tool for multiplexed screening of pesticide residues using single antibody.

Rapid and visual detection of Listeria monocytogenes based on nanoparticle cluster catalyzed signal amplification

Foodborne pathogens pose a significant threat to human health worldwide. The identification of foodborne pathogens needs to be rapid, accurate and convenient. Here, we constructed a nanoparticle cluster (NPC) catalyzed signal amplification biosensor for foodborne pathogens visual detection. In this work, vancomycin (Van), a glycopeptide antibiotic for Gram-positive bacteria, was used as the first molecular recognition agent to capture Listeria monocytogenes (L. monocytogenes). Fe3O4 NPC modified aptamer, was used as the signal amplification nanoprobe, specifically recognize to the cell wall of L. monocytogenes. As vancomycin and aptamer recognize L. monocytogenes at different sites, the sandwich recognition showed satisfied specificity. Compared to individual Fe3O4 nanoparticle (NP), NPC exhibit collective effect-enhanced catalytic activity for the color reaction of chromogenic substrate. The change in absorbance or color could represent the concentration of target. Using the Fe3O4 NPC-based signal amplification method, L. monocytogenes whole cells could be directly assayed within a linear range of 5.4×10(3)-10(8) cfu/mL and a visual limit of detection of 5.4×10(3) cfu/mL. Fe3O4 NPC-based method was more sensitive than the Fe3O4 NP-based method. All these attractive characteristics of highly sensitivity, visual and labor-saving, make the biosensor possess a potential application for foodborne pathogenic bacteria detection.