The COVID-19 pandemic has posed an unprecedented global challenge, with Staphylococcus aureus (S. aureus) emerging as a particularly dangerous and pervasive foodborne pathogen. Capable of producing a multitude of toxins, S. aureus contamination can lead to a host of life-threatening illnesses, making its rapid and accurate detection a critical priority for food safety.
Conventional detection methods, while considered the gold standard, suffer from lengthy processing times, labor-intensive procedures, and limited detection ranges. Emerging techniques, such as nucleic acid-based and immunological approaches, offer improved speed and sensitivity, but often require specialized equipment and trained personnel. To address these limitations, researchers have turned to the remarkable potential of nanomaterials, which hold the key to developing innovative, high-performance biosensing platforms.
Nanozymes, a class of superior nanomaterials, have garnered significant attention due to their exceptional catalytic activity and stability, making them ideal for enhancing the sensitivity of nano-biosensors. Among these, manganese dioxide nanosheets (MnO2 NSs) have emerged as a versatile choice, exhibiting fluorescence quenching, oxidation, and peroxidation properties that can be leveraged for dual-mode detection.
In this groundbreaking study, we present the development of a ratiometric fluorescence and colorimetry dual-mode nano-biosensor for the rapid and reliable determination of S. aureus. By harnessing the unique capabilities of MnO2 NSs and blue emission carbon dots (BCDs), this innovative approach offers a comprehensive solution to the challenges faced in S. aureus detection.
Experimental Approach and Findings
The synthesis of the key nanomaterials, MnO2 NSs, BCDs, and amino-functionalized ferriferrous oxide nanoparticles (Fe3O4 NPs-NH2), was achieved through simple, labor-saving methods. Comprehensive characterization confirmed the successful fabrication of these nanomaterials, with MnO2 NSs exhibiting the desired sheet-like nanostructure, BCDs displaying excellent fluorescence properties, and Fe3O4 NPs-NH2 demonstrating magnetic separation capabilities.
The dual-mode detection mechanism was elegantly designed, leveraging the fluorescence quenching and oxidation properties of MnO2 NSs. In the presence of S. aureus, the content of MnO2 NSs in the supernatant decreased, leading to an increase in the fluorescence of BCDs at 440 nm and a decrease in the fluorescence of the oxidation product, 2,3-diaminophenazine (DAP), at 555 nm. Simultaneously, the absorption peak of DAP at 420 nm decreased, enabling both ratiometric fluorescence and colorimetric detection.
The optimized dual-mode nano-biosensor exhibited impressive analytical performance, with wide linear ranges (37 to 3.7 × 106 CFU/mL), low limits of detection (9 CFU/mL for ratiometric fluorescence and 22 CFU/mL for colorimetry), and excellent precision and accuracy, validated according to ICH guidelines. Importantly, the use of dual aptamers (MnO2 NSs-Apt1 and Fe3O4 NPs-Apt2) ensured high specificity, and the ratiometric fluorescence and colorimetry dual-mode approach minimized the risk of false positive and false negative results.
Real-world Applicability and Impact
To assess the practical applicability of the dual-mode nano-biosensor, the team conducted extensive testing in various food matrices, including chicken, fish, mutton, and shrimp. The results demonstrated excellent recoveries and insignificant differences compared to the standard plate counting method, confirming the reliability and accuracy of the developed approach.
The significance of this work extends far beyond the laboratory. By providing a rapid, sensitive, and dual-mode detection platform for S. aureus, this innovation holds the potential to revolutionize food safety monitoring and management. The ability to quickly and accurately identify S. aureus contamination will empower food producers, regulators, and consumers to take swift and informed actions, safeguarding public health and strengthening global food security.
Conclusion and Future Perspectives
The development of this ratiometric fluorescence and colorimetry dual-mode nano-biosensor for S. aureus detection represents a groundbreaking advancement in the field of food safety. The seamless integration of MnO2 NSs, BCDs, and magnetic separation has yielded a versatile, high-performance platform that addresses the limitations of existing methods.
Looking ahead, the adaptability of this approach opens up exciting possibilities for the detection of other critical foodborne pathogens, simply by incorporating the appropriate aptamers. As the global community continues to grapple with the challenges of foodborne diseases, innovations like this dual-mode nano-biosensor will be instrumental in ushering in a new era of enhanced food safety and security, ultimately benefiting both producers and consumers worldwide.
