Finding a way out? Comprehensive biotransformation study of novel fluorinated surfactants

A group of novel polyfluoroether substances affects lipid metabolism in human hepatocyte HepaRG cells less than classic perfluoroalkyl compounds

Per- and polyfluoroalkyl substances (PFAS) are used for numerous industrial applications including the production of fluorosurfactants. Some prominent PFAS, e.g., perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are non-degradable and therefore persist in the environment. They display various toxic properties including dysregulation of hepatic lipid metabolism. At the molecular level, these effects are mainly based on a PFAS-mediated activation of the peroxisome proliferator-activated receptor alpha (PPARα). A group of novel, degradable polyfluoroether compounds has been designed as building blocks for the production of alternative, degradable fluorosurfactants. In the present study, we examined the capacity of four of these novel polyfluoroether compounds to induce PPARα activation, increase intracellular triglyceride accumulation, and produce a cytotoxic response. In contrast to some classic PFAS including PFOA and PFOS, the novel compounds neither activated PPARα in a transactivation assay, nor did they induce expression of selected PPARα-dependent target genes in differentiated HepaRG cells, a model for human hepatocytes. They also did not induce triglyceride accumulation in HepaRG cells. The in vitro data indicate that the polyfluoroether compounds tested in the present study are not PPARα agonists. Since PPARα agonist activity is often associated with toxic responses, it can be assumed that these substances are less toxic than classic PFAS such as PFOA and PFOS, at least with respect to PPARα-dependent toxicity mechanisms.

Interspecies comparison of metabolism of two novel prototype PFAS

As a result of proposed global restrictions and regulations on current-use per-and polyfluoroalkyl substances (PFAS), research on possible alternatives is highly required. In this study, phase I in vitro metabolism of two novel prototype PFAS in human and rat was investigated. These prototype chemicals are intended to be safer-by-design and expected to mineralize completely, and thus be less persistent in the environment compared to the PFAS available on the market. Following incubation with rat liver S9 (RL-S9) fractions, two main metabolites per initial substance were produced, namely an alcohol and a short-chain carboxylic acid. While with human liver S9 (HL-S9) fractions, only the short-chain carboxylic acid was detected. Beyond these major metabolites, two and five additional metabolites were identified at very low levels by non-targeted screening for the ether- and thioether-linked prototype chemicals, respectively. Overall, complete mineralization during the in vitro hepatic metabolism of these novel PFAS by HL-S9 and RL-S9 fractions was not observed. The reaction kinetics of the surfactants was determined by using the metabolite formation, rather than the substrate depletion approach. With rat liver enzymes, the formation rates of primary metabolite alcohols were at least two orders of magnitude higher than those of secondary metabolite carboxylic acids. When incubating with human liver enzymes, the formation rates of single metabolite carboxylic acids, were similar or smaller than those experienced in rat. It also indicates that the overall metabolic rate and clearance of surfactants are significantly higher in rat liver than in human liver. The maximum formation rate of the thioether congener exceeded 10-fold that of the ether in humans but were similar in rats. Overall, the results suggest that metabolism of the prototype chemicals followed a similar trend to those reported in studies of fluorotelomer alcohols.

Biopolymeric Nanocomposites for Wastewater Remediation: An Overview on Recent Progress and Challenges

Essential for human development, water is increasingly polluted by diverse anthropogenic activities, containing contaminants like organic dyes, acids, antibiotics, inorganic salts, and heavy metals. Conventional methods fall short, prompting the exploration of advanced, cost-effective remediation. Recent research focuses on sustainable adsorption, with nano-modifications enhancing adsorbent efficacy against persistent waterborne pollutants. This review delves into recent advancements (2020-2023) in sustainable biopolymeric nanocomposites, spotlighting the applications of biopolymers like chitosan in wastewater remediation, particularly as adsorbents and filtration membranes along with their mechanism. The advantages and drawbacks of various biopolymers have also been discussed along with their modification in synthesizing biopolymeric nanocomposites by combining the benefits of biodegradable polymers and nanomaterials for enhanced physiochemical and mechanical properties for their application in wastewater treatment. The important functions of biopolymeric nanocomposites by adsorbing, removing, and selectively targeting contaminants, contributing to the purification and sustainable management of water resources, have also been elaborated on. Furthermore, it outlines the reusability and current challenges for the further exploration of biopolymers in this burgeoning field for environmental applications.