Microplastics, defined as plastic particles smaller than 5 millimeters, have rapidly emerged as an environmental hazard due to their pervasive presence in aquatic ecosystems and potential risks to marine life and human health.
Traditional MP detection techniques predominantly rely on physical and chemical analyses such as microscopic enumeration, Fourier-Transform Infrared Spectroscopy (FTIR), and Raman spectroscopy.
While these methods can provide detailed morphological and chemical information, their operational complexity and high costs impede their routine application, especially in resource-limited settings.
Recent advances have shown that biological detection systems—biosensors—offer a promising alternative owing to their high sensitivity, specificity, and potential for in situ deployment.
Microbial biosensors, in particular, harness bacteria engineered to produce measurable signals upon interaction with target pollutants. T
he study emphasizes the bacterial adhesion protein CdrA's affinity for hydrophobic surfaces like plastics, making Pseudomonas aeruginosa a suitable chassis for developing a biosensor responsive to MPs.
The Current Study
The study employed a microbial biosensor based on Pseudomonas aeruginosa, engineered to express green fluorescent protein (GFP) for detecting microplastics (MPs).
Environmental seawater samples from urban locations in Hong Kong were collected and then sieved through filters to remove large debris.
To eliminate organic contaminants and potential biofouling agents, samples were washed with ethanol and treated with hydrogen peroxide.
The seawater was adjusted to an approximate pH of 8.1 for experimental consistency. MPs, mainly composed of biodegradable plastics, were introduced into the samples at varying concentrations. The biosensor was exposed to these samples, and fluorescence intensity was monitored over time as an indicator of MP presence.
Detection sensitivity was optimized through calibration curves correlating fluorescence levels with known MP concentrations.
To validate the detection, additional analytical techniques such as Raman microspectroscopy and FTIR spectroscopy were used to identify polymer types of MPs.
Raman spectroscopy measurements involved drying the particles on a sample holder and using a 785 nm laser to acquire spectra, which were then compared against a polymer database for identification.
The biosensor's performance in real seawater conditions was assessed by testing fluorescence responses at different temperatures, pH levels, and particle sizes.
Reusability was evaluated by cycling the biosensor through multiple detection rounds, monitoring GFP expression stability.
The combined approach enabled rapid, sensitive, and cost-effective detection of MPs in environmental samples, demonstrating the biosensor’s practical application in pollution monitoring.
Results and Discussion
The microbial biosensor demonstrated high sensitivity and specificity in detecting MPs within water samples, correlating GFP fluorescence intensity with MP concentration.
It responded within approximately three hours, which is significantly faster than conventional physical and chemical methods that often require up to a day or more.
The biosensor showed robustness, retaining over 85 % of its initial fluorescence after multiple detection cycles and remaining stable for up to three days when stored at 4 °C.
It detected MPs in clean and environmentally relevant seawater samples, including complex mixtures of different polymer types, such as polyethylene, polyester, nylon, and PVC.
The results were consistent with conventional methods but offered advantages in simplicity, cost, and speed. The integration with Raman spectroscopy allowed quantification and polymer-type identification, which is crucial for understanding MP sources and environmental impacts.
This combined methodology helped to distinguish biodegradable plastics from traditional ones in real samples, demonstrating practical applicability for environmental monitoring.
The study highlights the sensor’s potential as a first-line screening tool that can guide more detailed analyses and enable large-scale, routine monitoring in diverse aquatic environments.
Conclusion
This study underscores the transformative potential of microbial biosensors in environmental pollution detection, specifically for microplastics.
The engineered Pseudomonas aeruginosa-based GFP biosensor provides a rapid, sensitive, and cost-effective alternative to traditional physical and chemical detection techniques. Its ability to detect low concentrations of MPs within hours and its compatibility with Raman microspectroscopy for detailed chemical characterization make it especially promising for real-time environmental monitoring.
The biosensor's reusability, stability, and ease of deployment position it as an accessible tool capable of addressing the pressing need for scalable MP detection in various water bodies.
Future advancements could include integrating this biosensor with portable devices for in-field application, further expanding its potential for widespread environmental surveillance.
Overall, this approach offers significant advantages in speed, sensitivity, and practicality, paving the way toward more effective management of plastic pollution.
Journal Reference
Choi E., Ma Y., et al. (2025). Detection of microplastics pollution using a green fluorescent protein-based microbial biosensor coupled with Raman spectroscopy. ACS Sensors. DOI: 10.1021/acssensors.5c01120, https://pubs.acs.org/doi/10.1021/acssensors.5c01120