In a recent article published in the journal Scientific Reports, researchers introduced a novel ultraviolet-excitable aptasensor for the rapid and sensitive detection of Aflatoxin B1. They aim to provide a user-friendly and cost-effective solution for on-site testing.
Schematic illustration of UV-based aptasensor in sensing target AFB1 by employing FEP film strip. The aptasensor with conducting GO-CT undergoes electronic excitation when exposed to UV light during measurement. In contrast, no excitation signal when exposed to visible light. Image Credit: https://www.nature.com/articles/s41598-024-68264-3
Background
Aflatoxins are toxic secondary metabolites produced by fungi, primarily Aspergillus species, with AFB1 being the most toxic and carcinogenic. Therefore, detecting AFB1 is crucial for maintaining food safety.
Traditional detection methods, such as HPLC and LC-MS, involve complex sample preparation and analysis, which can be impractical for non-experts or in field settings.
A promising alternative is the use of aptamer-based sensors. These novel sensors leverage aptamers—short, single-stranded DNA or RNA molecules that bind specifically and with high affinity to targets like AFB1. This approach offers significant advantages in terms of specificity, sensitivity, and ease of use, potentially revolutionizing the way we detect aflatoxins by simplifying the process and making it more accessible in various settings.
The Current Study
In this study, an aptamer with a high affinity for AFB1 was developed using the Systematic Evolution of Ligands by Exponential Enrichment (SELEX). This process started with a diverse library of single-stranded DNA (ssDNA) sequences, which varied in their central region but had fixed primer binding sites at both ends for amplification.
The aptamers were enriched for their ability to bind to AFB1 through polymerase chain reaction (PCR), which amplified the sequences with the highest binding affinity. The final aptamer candidates were then characterized using surface plasmon resonance (SPR) or fluorescence-based assays to determine their binding affinity (Kd values) and specificity for AFB1 compared to other aflatoxins.
An aptasensor was created using a fluorinated ethylene propylene (FEP) film strip as the sensing platform. This aptasensor operates on the principle of fluorescence changes upon AFB1 binding. It is excited by ultraviolet (UV) light at an optimized wavelength to maximize the fluorescence signal emitted by the aptamer-AFB1 complex. When AFB1 is introduced, the aptamer binds to it, causing a conformational change that alters the fluorescence properties.
The fluorescence intensity was measured using a portable fluorescence reader or a custom-built detection system. Changes in fluorescence intensity were correlated with AFB1 concentration in the sample. The study also investigated various factors, such as pH, ionic strength, and temperature, to optimize the binding affinity and stability of the aptamer-AFB1 complex.
The performance of the aptasensor was compared with established methods like high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Food samples such as brown sugar, peanuts, and rice were spiked with known concentrations of AFB1, and the aptasensor's results were compared to those from standard methods.
The specificity of the aptasensor was assessed by testing its performance in the presence of common food matrix components and potential interfering substances. This ensured that the aptasensor could reliably detect AFB1 in complex food samples. Finally, the stability of the aptasensor was evaluated by storing it under various conditions and periodically testing its performance to determine its shelf-life and operational stability.
Results and Discussion
The results demonstrated that the developed aptasensor exhibited a high sensitivity for AFB1 detection, with a detection limit significantly lower than that of traditional methods. The sensor was able to detect AFB1 concentrations as low as 0.1 ng/mL, making it suitable for monitoring food safety standards. When compared to HPLC and LC-MS, the aptasensor provided comparable results in terms of accuracy and precision. The study highlighted that the aptasensor could deliver results within 20 minutes, significantly faster than conventional methods, which often require hours or even days.
The simplicity of the aptasensor's design allows for easy use in field conditions, making it an ideal tool for non-experts. The study emphasized the potential for on-site testing, which could greatly enhance food safety monitoring in regions with limited access to laboratory facilities. The researchers conducted interference studies to evaluate the sensor's performance in the presence of common food matrix components.
The aptasensor showed robust performance, with minimal interference from other substances, further validating its practical application. The aptasensor demonstrated excellent stability over time, with a shelf-life of several months when stored properly. This characteristic is crucial for ensuring consistent performance in real-world applications.
Conclusion
In conclusion, this study introduced a novel ultraviolet-excitable aptasensor for the rapid and sensitive detection of aflatoxin B1 in food products. The aptasensor demonstrates high sensitivity, a quick response time, and minimal interference from food matrices, making it a promising tool for enhancing food safety, especially in areas prone to aflatoxin contamination. Future research could aim to expand the sensor's capabilities to detect other aflatoxins and incorporate advanced technologies for improved data management and analysis.
Journal Reference
Mazlan N.F., Sage E.E., et al. (2024). On-site sensing for aflatoxicosis poisoning via ultraviolet excitable aptasensor based on fluorinated ethylene propylene strip: a promising forensic tool. Scientific Reports 14, 17357. DOI: 10.1038/s41598-024-68264-3, https://www.nature.com/articles/s41598-024-68264-3