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MOF−Bacteriophage Biosensor for Highly Sensitive and Specific Detection of Staphylococcus aureus
Summary:
The authors from CSIR-Central Scientific Instrument Organisation, Academy of Scientific and Innovative Research, and Hanyang University developed a MOF−bacteriophage biosensor (NH₂-MIL-53(Fe) conjugated with S. aureus-specific bacteriophages) with characteristics such as high sensitivity, specificity, regenerability, long-term stability, and water dispersibility, achieving excellent results in the application of Staphylococcus aureus detection.
Background:
1. Bacterial contamination in food is a serious issue, and Staphylococcus aureus is a common pathogen. Traditional detection methods like culture-based methods are time-consuming, while existing biosensors have limitations such as low stability, poor specificity, or complex preparation. Although some fluorescent biosensors using nanomaterials exist, they often have issues like low aqueous stability or high toxicity.
2. The authors proposed an innovative method by conjugating a water-stable, non-toxic fluorescent MOF (NH₂-MIL-53(Fe)) with S. aureus-specific bacteriophages using glutaraldehyde as a cross-linker, developing a highly sensitive and specific biosensor for S. aureus detection.
Research Content:
1. Synthesis:
The authors synthesized NH₂-MIL-53(Fe) via a solvothermal method by reacting FeCl₃·6H₂O and 2-aminobenzene-1,4-dicarboxylic acid (NH₂-BDC) in deionized water at 150 °C for 3 days. Then, the MOF was conjugated with S. aureus-specific bacteriophages using glutaraldehyde as a cross-linker: the MOF was first treated with glutaraldehyde, then mixed with the bacteriophage solution and reacted overnight to form the MOF−bacteriophage complex.
2. Characterizations:
1) BET, pore size distribution: Not mentioned in the article.
2) SEM/TEM tests: The TEM and FE-SEM images showed that the MOF has clear edges, and after conjugation with bacteriophages, the edges become irregular with bacteriophages attached, maintaining structural integrity and crystallinity; the particles are micron-sized.
3) Other tests: UV−vis spectra showed absorption peaks of the MOF at 220, 250, and 340 nm, and a protein-specific peak at 279 nm after conjugation with bacteriophages; PL spectra showed the MOF has a characteristic emission peak at 430 nm, and the complex retains this signature with slight intensity reduction; FTIR spectra confirmed the presence of amine and carboxyl groups in the MOF, and an additional peak around 900 cm⁻¹ in the complex indicating successful conjugation; XRD patterns matched literature data for the MOF, and the complex retained most peaks, showing structural integrity.
3. Application:
- Detection of S. aureus: The biosensor achieved a limit of detection of 31 CFU/mL and a detection range of 40 to 4×10⁸ CFU/mL based on photoluminescence quenching.
- Specificity: It showed high specificity for S. aureus, with little response to S. arlettae and E. coli, even in mixed samples.
- Stability: It remained stable for over 100 days at room temperature with insignificant PL response change.
- Regeneration: It could be regenerated, retaining ~90% activity after 5 cycles.
- Real sample analysis: It successfully detected S. aureus in spiked cream pastry samples, with results consistent with the standard colony counting method.
4. Mechanism:
The bacteriophages specifically bind to S. aureus, causing a reduction in the effective excitation of the MOF due to competitive absorption of light between components, leading to photoluminescence quenching. The quenching intensity is proportional to the bacterial concentration, enabling quantitative detection.
Outlook:
This research successfully developed a MOF−bacteriophage biosensor for S. aureus detection with high sensitivity, specificity, stability, and regenerability. It overcomes the limitations of existing methods, providing a new tool for food safety monitoring and clinical diagnosis, and lays a foundation for the application of MOF−bacteriophage complexes in biosensing.
MOF−Bacteriophage Biosensor for Highly Sensitive and Specific Detection of Staphylococcus aureus
Authors: Neha Bhardwaj, Sanjeev K. Bhardwaj, Jyotsana Mehta, Ki-Hyun Kim, Akash Deep
DOI: 10.1021/acsami.7b07818
Link: https://pubs.acs.org/doi/10.1021/acsami.7b07818
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