(213b) Engineered, Field-Deployable Biosensors for Detection of Pfas Compounds in Soil, Water and Food

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic fluorinated chemicals with surface active and water-repellent properties. Given their wide-spread use in numerous consumer and industrial products and persistence in the environment due to strong carbon-fluorine bonds, there is significant accumulation of PFAS in water, soils, food and ultimately people. Recent studies have indicated that any level of PFAS exposure is detrimental to human health; currently, the EPA has set legal exposure limits for PFOA and PFOS at 4 ppt, although higher levels are often found in water, soil and food. As most human interaction with PFAS comes from ingestion, it is important to be able to detect PFAS in multiple types of heterogeneous samples. We present an approach to designing fluorescence-based biosensors for the rapid detection of PFAS based on human liver fatty acid binding protein (hLFABP). In our first approach, introduction of solvatochromic fluorophores within the ligand binding pocket (F50) allowed for intrinsic detection of PFOA, PFOS, and PFHxS via blue-shifts in fluorescence emission spectra. Initially, a single tryptophan mutation (F50W) was found to be able to detect PFOA with a LOD of 2.8 ppm. We improved the sensitivity of the biosensor by exchanging tryptophan for the thiol reactive fluorophore, acrylodan. The acrylodan conjugated C69S/F50C hLFABP variant is capable of detecting PFOA, PFOS, and PFHxS in PBS with LODs of 112 ppb, 345 ppb, and 1.09 ppm respectively. The protein-based sensor is also capable of detecting these contaminants at similar ranges in spiked environmental water samples, including samples containing interfering anionic surfactants such as sodium dodecyl sulfate (SDS). In our second approach, we developed a circularly-permuted green fluorescent protein (GFP)-based biosensor using hLFABP as the binding element to implement a genetically-encoded biosensor for cell-based detection; initial designs indicate our GFP biosensor can also detect key PFAS compounds such as PFOA. Additional work demonstrates these biosensors can be expanded to detect other co-pollutants such as fuel hydrocarbons. Ongoing work is focused on optimizing signal-to-noise ratio and lowering LOD for PFAS detection, as well as expanding testing to other foods. Overall, this work demonstrates engineered hLFABP is a useful platform for detection of PFAS in environmental water samples and highlights its ease of use and versatility in field applications.