Lactobacillus reduction drives oxidative gut-liver adverse effects of heterogeneous aggregates polylactic acid nanoplastics and silica nanoparticles.

Polylactic acid (PLA) plastics are increasingly used in food packaging as biodegradable substitute to petroleum-based plastics. However, the high temperatures used to reconstitute powdered foods, which often contain silica nanoparticles (SiNPs), readily induce PLA degradation, generating large amounts of PLA nanoplastics (PLA NPs). Due to the high affinity of PLA NPs to contaminants, this study investigated the interactions between PLA NPs and SiNPs, and their gut-liver adverse effects. Following the oral administration of PLA NPs and SiNPs to C57BL/6J male mice for 90 days, liver, colon, blood, and fecal samples were collected to assess liver damage, gut function and microbiota composition. The results showed that PLA NPs and SiNPs formed heterogeneous aggregates complexes (HAC), resulting in different hydrodynamic size and zeta potential. Compared with PLA NPs or SiNPs, HAC induced more severe hepatic and intestinal injuries and further disrupted gut microbial homeostasis. In the fecal microbiota transplantation and key bacteria supplementation experiments, liver oxidative stress induced by HAC was partly attributed to gut dysbiosis and the reduced abundance of Lactobacillus. In conclusion, HAC exhibited different physicochemical and toxicological properties than single contaminant, and oxidative stress is the key factor in gut-liver adverse effects. These findings uncover the potential interactions among contaminants and their combined adverse effects, and provided a new perspective for risk assessment process related to food contaminant exposure.