Release behavior of dibutyl phthalate from polyvinyl chloride microplastics in gastric fluid system: Effects of microplastic characteristics and pepsin

Pepsin promotes the DBP release from PVC-MPs. • Smaller PVC-MPs with higher DBP contents exhibit higher release amounts. • Competitive adsorption of pepsin weakens the DBP binding with PVC-MPs. • Electrostatic, vdW interactions and hydrogen bonds with pepsin drive the DBP release. Ubiquitous microplastics (MPs) can be inadvertently ingested by organisms, and plasticizers released from them may pose potential exposure risks to wildlife and humans. However, the release behavior of dibutyl phthalate (DBP) from polyvinyl chloride (PVC) MPs in digestive tract environments remains poorly understood. In this study, the release behavior of DBP from PVC-MPs under simulated gastric fluid (SGF) conditions was investigated, with particular emphasis on the effects of microplastic characteristics and pepsin. It was found that smaller particle size and higher DBP content resulted in greater DBP release from PVC-MPs. In addition, the presence of pepsin facilitated DBP release. The maximum release amount of DBP was measured to be 1.536 mg/g in pepsin-containing SGF, which was 1.62 times that observed in pepsin-free SGF. Meanwhile, the release rate constant of DBP in pepsin-containing SGF was up to 1.79 times that in pepsin-free SGF. Molecular dynamics simulations suggested that pepsin could bind to the PVC-MP surface, potentially alter the interfacial interactions between PVC-MPs and DBP, and contribute to DBP dissociation from PVC-MPs. Density functional theory calculations further indicated that the stronger interaction between pepsin and DBP may contribute to enhanced DBP release, with electrostatic interactions, van der Waals interactions, and hydrogen bonding potentially involved. These findings could improve our understanding of the release behavior of plasticizers from MPs under SGF conditions. Download: Download high-res image (220KB) Download: Download full-size image