Detection of Microplastics Pollution Using a Green Fluorescent Protein-Based Microbial Biosensor Coupled with Raman Spectroscopy

The persistence of plastics in the environment, especially after waste disposal, poses a significant threat to ecosystems. Microplastics (MPs) are particularly concerning due to their small size and the difficulty of detection. Once in aquatic systems, MPs threaten marine life and human health through the food chain. Current MP detection methods, such as microscopic enumeration or Fourier-transform infrared, for assessment of plastic pollution are either tedious or expensive to operate. Biological-based detection techniques could offer higher sensitivity to detect low concentrations of pollutants, which raises the rationale to develop a cost-effective MP-detecting biosensor. As a proof of concept, we employed an environmental bacterium Pseudomonas aeruginosa as a green fluorescent protein-based biosensor capable of producing detectable fluorescence signals within 3 h, with a detection limit of 1 ng/mL that is more sensitive than the existing MP analytical methods. Fluorescence signals expressed by the biosensor correlated positively to MP concentration, so a standard curve could be established for convenient measurement of MP concentrations. We then established a microbial biosensor-Raman microspectroscopy combinatorial method to detect 100 μg/mL MPs primarily composed of biodegradable plastics in a pilot trial of pretreated urban waterfront seawater samples. Hence, we showed the novelty of using microbial biosensors as a cost-effective, rapid, and efficient tool in assessing MP presence and concentration, enabling convenient monitoring of the extent of MP pollution in the environment.