Microplastics interaction with bisphenol A: Adsorption, desorption, and in vitro biological effects

Microplastic (MP) pollution is an increasing environmental concern due to its persistence and potential risks to both ecosystems and human health. Additionally, MPs can adsorb and become vehicle of other pollutants and hazardous chemicals. Among these, Bisphenol A (BPA) is a well-known endocrine disruptor. This study investigates the effects of MPs exposure in multiple cell types (preadipocytes, hepatocytes, hypothalamic neurons, and endothelial cells), the adsorption/desorption dynamics of BPA on MPs and the biological effects of BPA-sorbed MPs. We employed 5 μm commercial polystyrene microplastics (PS-MPs), both in their pristine form and with carboxyl (-COOH) functionalization, mimicking surface oxidation resulting from environmental weathering. While exposure to a wide range of pristine PS-MPs concentrations did not affect cell viability, COOH-functionalized PS-MPs induced significant toxicity in neurons and endothelial cells at high concentrations (>100 μg/mL). Furthermore, COOH-functionalized MPs altered lipid accumulation during preadipocyte to adipocyte differentiation. Using an optimized HPLC-MS/MS method with online SPE, we quantified the adsorption of BPA onto PS-MPs in water and its subsequent desorption under physiological conditions, achieving detection and quantification limits (3 ng/mL and 10 ng/mL, respectively) that enabled accurate BPA measurements, particularly in desorption studies. COOH-functionalized PS-MPs exhibited higher BPA adsorption efficiency and an increased desorption in cell culture media (29 % adsorption; 45 % desorption) compared to pristine PS-MPs (23 % adsorption; 13 % desorption), suggesting that oxidized MPs may act as more effective carriers for toxic chemicals. However, when cells were exposed to BPA-sorbed PS-MPs, no synergistic effects between the two pollutants were observed. These findings underscore the pivotal role of MP surface chemistry in governing pollutant interactions and shaping biological responses. Additionally, they emphasize the importance of assessing pollutant adsorption onto MPs; this approach, rather than using simple co-exposure methods, is essential for studying the role of MPs as carriers of environmental pollutants in biological systems.