Engineering a protein biosensor to detect common NSAIDs in wastewater

Why this research matters

Pharmaceuticals often end up in wastewater after use, and monitoring them can be technically demanding. Traditional analytical methods are powerful but typically require specialized equipment and off-site processing, which can limit how frequently water is tested.

This study describes a protein-based biosensor designed to detect two widely used “profen” non-steroidal anti-inflammatory drugs, ketoprofen and pranoprofen, under conditions meant to resemble wastewater effluent.

The challenge

Profen NSAIDs are commonly used pain relievers. According to the authors, these drugs can enter water systems through multiple pathways. Routine monitoring, however, is not always straightforward. Wastewater contains many other chemicals, and testing often depends on laboratory-based methods rather than simple, scalable detection tools.

The authors set out to build a genetically encodable sensor that could recognize specific profen drugs and produce a measurable signal.

The new approach

The team started with PYR1, a plant hormone receptor that naturally binds abscisic acid. When PYR1 binds its ligand, it interacts with another protein called HAB1. This ligand-dependent interaction can serve as a sensing mechanism: if a new molecule triggers PYR1 to bind HAB1, the interaction can be detected.

Using computational modeling and laboratory screening, the researchers redesigned PYR1 so that it would respond to profen NSAIDs instead of its natural plant hormone. They tested many variants and selected versions that responded to ketoprofen and pranoprofen while minimizing background activity in the absence of drug.

The final engineered variant, called PYRNSAID, was then evaluated in binding assays.

Key results

In yeast-based assays, PYRNSAID detected ketoprofen and pranoprofen at nanomolar concentrations. The sensor also responded to several related NSAIDs, although with different sensitivities.

To move closer to a practical format, the authors linked the engineered receptor to a split luciferase system. In this setup, when the drug triggers receptor–partner binding, the luciferase halves come together and produce light.

In this in vitro assay, the sensor remained responsive to ketoprofen and pranoprofen even when tested in simulated wastewater containing other common small molecules. Most of the tested background compounds did not strongly activate the sensor.

Broader significance

The authors describe this work as an initial step toward scalable monitoring of pharmaceutical contaminants. While additional development would be needed before real-world deployment, the study demonstrates that a redesigned protein receptor can detect specific NSAIDs and function in a complex chemical background.

Together, these results show how protein engineering and high-throughput screening can be combined to create biosensors for small-molecule detection in environmental contexts.

This work was recently posted as a bioRxiv preprint by Whitehead and colleagues.