Fluorescent analysis of Staphylococcus aureus by using daptomycin and immunoglobulin G for dual sites affinity

Ultrasensitive colorimetric detection of Staphylococcus aureus using wheat germ agglutinin and IgY as a dual-recognition strategy

A novel colorimetric platform was designed for the determination of S. aureus by utilizing a dual-recognition strategy, where wheat germ agglutinin (WGA)-functionalized magnetic beads were served as separation elements to capture and enrich S. aureus efficiently from the matrix. Horseradish peroxidase (HRP) labeled chicken anti-protein A IgY (HRP-IgY) was used to label the captured S. aureus. A chicken IgY was introduced as a signal tracer to bind with staphylococcal protein A (SPA) on the surface of S. aureus, which can circumvent the interference from protein G-producing Streptococcus. Subsequently, the colorimetric signal was achieved by an HRP-catalyzed reaction, which was amplified by HRP-IgY bound by approximately 80,000 SPA molecules on one S. aureus. The entire detection process could be accomplished within 90 min. Under optimal conditions, the linear response of different S. aureus concentrations ranged from 7.8 × 102 to 2.0 × 105 CFU/mL and the limit of detection reached down to 3.9 × 102 CFU/mL. Some common non-target bacteria yielded negative results, indicating the excellent specificity of the method. The developed strategy was successfully applied to the determination of S. aureus in various types of samples with satisfactory recoveries. Therefore, the novel dual-recognition strategy possessed the advantages of high sensitivity, specificity, and low cost and exhibited considerable potential as a promising tool to defend public health.

Applying a sandwich-like strategy for dual 'light up' capture and eradication of Staphylococcus aureus using magnetically functionalized materials

In this study, we proposed an innovative application of porcine immunoglobulin G (IgG)-functionalized Fe3O4 (IgG-Fe3O4) specifically designed to target and capture Staphylococcus aureus (S. aureus). In addition, aminophenylboronic acid-modified tetraphenylethylene nanoparticles (APBA-TPE NPs) were utilized, establishing a sandwich-type dual recognition system via interactions with the bacteria's extracellular glycolipids. This approach enables highly sensitive and precise detection of bacterial presence, with a limit of detection (LOD) reaching down to 5.0 CFU/mL. Specifically, the prepared APBA-TPE NPs achieved 99.99% bacterial inactivation within 60 min at a concentration of 200 µg/mL. The results showed that APBA-TPE NPs possess a remarkable capacity for reactive oxygen species (ROS) production, which could attack the bacterial cell membrane, leading to bacterial lysis and content leakage, and ultimately to bacterial death. Furthermore, the material still showed good recoveries ranging from 88.5% to 93.5% in actual water samples, as well as a favorable sterilizing effect of killing all microorganisms for 60 min. This research provides new strategies and insights into the construction of methods for the specific capture, detection, and inactivation of S. aureus.

Time-resolved fluorescence immunoassay based on glucose oxidase-encapsulated metal-organic framework for amplified detection of foodborne pathogen

BACKGROUND

Fluorescence immunoassays are commonly employed for the detection of pathogenic bacteria as a means of ensuring food safety and preserving public health. However, the challenges such as poor photostability and background interference have limited their sensitivity and accuracy. The emergence of metal-organic frameworks (MOFs) as a label probe offers a promising solution for advancing fluorescence immunoassays owing to their tunable nature. Nonetheless, the low fluorescence efficiency of MOFs and the potential risk of dye leakage pose obstacles to achieving high detection sensitivity. Therefore, there exists a pressing need to fully utilize the potential of MOF composites in fluorescence immunoassays.

RESULTS

We explored the potential of glucose oxidase-encapsulated zeolitic imidazole framework-90 (GOx@ZIF-90) as a label probe to construct a time-resolved fluorescence immunoassay with amplified detection signal. This immunoassay involved functionalizing Fe3O4 nanoparticle with porcine antibody to specifically capture and separate the target bacteria, Staphylococcus aureus (S. aureus). The captured S. aureus was then bound by GOx@ZIF-90 modified with vancomycin, resulting in a fluorescence response in the europium tetracycline (EuTc). The encapsulation of GOx in ZIF-90 provided a confinement effect that significantly enhanced the catalytic activity and stability of GOx. This led to a highly efficient conversion of glucose to H2O2, amplifying the fluorescence signal of EuTc. The immunoassay demonstrated a high sensitivity in detecting S. aureus, with a detection limit of 2 CFU/mL. We also obtained satisfactory results in milk samples. Attractively, the time-resolved detection mode of EuTc allowed the immunoassay to eliminate background fluorescence and enhance accuracy.

SIGNIFICANCE

This study not only presented a new method for detecting foodborne pathogens but also highlighted the potential of enzyme-encapsulated MOF composites as label probes in immunoassays, providing valuable insights for the design and fabrication of MOF composites for various applications.

Upconversion nanoparticles-based FRET system for sensitive detection of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a pathogenic bacterium that seriously endangers food safety. Herein, a rapid, sensitive and specific aptasensor based on upconversion fluorescence resonance energy transfer (FRET) was developed for S. aureus detection in food. Aptamer-functionalized gold nanoparticles (AuNPs-aptamers) were bonded to cDNA-modified upconversion nanoparticles (UCNPs-cDNA) by complementary pairing, resulting in fluorescence quenching. After adding S. aureus into the system, the aptamers preferentially combined with S. aureus, dissociated UCNPs-cDNA from AuNPs-aptamers, and the fluorescence was recovered. Under optimized conditions, there was a significant linear correlation between fluorescence intensity and S. aureus concentration over the range 47-4.7 × 10⁷ CFU/mL (R² = 0.9904) with a detection limit of 10.7 CFU/mL. Furthermore, the precision and accuracy of the developed biosensor were validated using standard plate count method, yielding no significant differences. The proposed method has potential application for rapid and sensitive quantification of S. aureus in food.

‘Off–on’ switchable fluorescent probe for prompt and cost-efficient detection of bacteria

The rapid and straightforward detection of bacteria in food and human samples is becoming important, particularly in view of the development of point-of-care devices and lab-on-a-chip tools for prevention and treatment of bacterial infections.