Nontarget Screening of Per- and Polyfluoroalkyl Substances Binding to Human Liver Fatty Acid Binding Protein
By Diwen Yang, Jiajun Han, David Ross Hall, Jianxian Sun, Jesse Fu, Steven Kutarna, Keith A Houck, Carlie A LaLone, Jon A Doering, Carla A Ng, and Hui Peng
Environ. Sci. Technol.
April 14, 2020
More than one thousand per- and polyfluoroalkyl substances (PFASs) have been discovered by nontarget analysis (NTA), but their prioritization for health concerns is challenging. We developed a method by incorporating size exclusion column co-elution (SECC) and NTA, to screen PFASs binding to human liver fatty acid binding protein (hL-FABP). Of 74 PFASs assessed, 20 were identified as hL-FABP ligands in which 8 of them have high binding affinities. Increased PFASs binding affinities correlate with stronger responses in electrospray ionization (ESI-) and longer retention times on C18 column. This is well explained by a mechanistic model which revealed that both polar and hydrophobic interactions are crucial for binding affinities. Encouraged by this, we then developed a SECC method to identify hL-FABP ligands, and all 8 high-affinity ligands were selectively captured from 74 PFASs. The method was further applied to an aqueous film-forming foam (AFFF) product in which 31 new hL-FABP ligands were identified. Suspect and nontargeted screening revealed these ligands as analogues of perfluorosulfonic acids, and homologues of alkyl ether sulfates (C8- and C10/EOn, C8H17(C2H4O)nSO4- and C10H21(C2H4O)nSO4-). The SECC method was then applied to AFFF-contaminated surface waters. In addition to perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulphonic acid (PFHxS), 8 other AFFF chemicals were discovered as novel ligands, including four C14- and C15/EOn. This study implemented a high-throughput method to prioritize PFASs and revealed the existence of many previously unknown hL-FABP ligands.