In Vivo Behavior Of Surface-Enhanced Raman Scattering Tag Labeled Nanoplastics In Ruditapes Philippinarum

In recent years,micro-nanoplastics have attracted more and more attention from the public and scientists as emerging marine pollutants.Large pieces of plastic in the ocean are gradually decomposed into fragments under the action of ultraviolet radiation,high temperature,mechanical friction,etc.,among which particles smaller than 5 mm in diameter are defined as microplastics,and particles smaller than 1μm are defined as nanoplastics.Micro-nanoplastics have long-term and extensive existence in environmental media such as water bodies and sediments,and can be ingested by plankton,benthic and other marine animals,causing toxic effects,and may be transmitted along the food chain,posing a threat to human health.It is of great significance to deeply understand the interaction law of micro-nano plastics and marine organisms for in-depth understanding of their environmental ecological effects and clarify their fate in the marine environment.Optical imaging tracing is a key technology for the study of nanoplastics in vivo behavior.Traditional fluorescently labeled particles and imaging methods have bottlenecks such as biological background interference,inability to accurately quantify,and easy to cause false positive results.In this study,Surface enhanced Raman scattering（SERS）-labeled nanoplastic model particles with gold nanoparticles as the core and polystyrene（PS）as the shell were developed,which have high sensitivity,high anti-interference ability and high stability and other advantages.We further selected Ruditapes philippinarum,a filter-feeding bivalve that has important ecological significance as a model organism.And the distribution,accumulation,and metabolic behaviors of nanoplastic model particles in monodisperse（100 nm）and aggregated state（1.5μm）were investigated in the clam.Using characteristic SERS signal detecting and Raman imaging technology,the in vivo distribution of micro-nano plastics can be quickly and accurately obtained;the content of micro-nano plastics can be quantitatively analyzed by inductively coupled plasma mass spectrometry（ICP-MS）to determine the content of gold elements.The results showed that nanoplastics could be absorbed by clam and transported to major organs such as gills,aqueducts,axopods,adductor muscles,mantle,and digestive gland.Among them,digestive gland is the main accumulation organ of micro-nano plastics,accounting for 86.7%of the whole body.After 11 days of purification and metabolism,90%of the nanoplastics in the body were excreted.The aggregated nanoplastics showed similar distribution and metabolic trends as monodisperse nanoplastics,however the accumulated content in each organ decreased by 15.2%-77.6%.At the same time,it was found that surface adsorption is also an important way to lead to the accumulation of nanoplastics in vivo.In addition,cooking treatments such as boiling do not reduce the amount of nanoplastics in the edible body.This study provides a new quantitative analysis method for the distribution,accumulation,and metabolism of nanoplastics in marine organisms,and provides basic data for the food safety assessment of clam aquaculture under the background of offshore pollution.Revealing the physical and chemical properties of the interface of micro-nano plastics after being digested by marine animals is an important part of understanding their environmental fate.However,efficient,and convenient analysis tools and screening evaluation methods are still lacking.In this study,a novel multifunctional plastic model particle was developed to explore and evaluate the interfacial properties of nanoplastics in Ruditapes philippinarum.The probe structure is composed of four parts from the inside to the outside.They are the core of iron tetroxide（Fe₃O₄）magnetic particle,gold nanoparticles,p H-responsive Raman reporter molecule 4-mercaptopyridine（4-Mpy）,and PS nanoshell.The digested particles in the feces were recovered by magnetic separation technology,and the response of the particle SERS signal to p H changes was analyzed by means of SERS spectrum acquisition and imaging technology,indicating changes in PS shell permeability.The results showed that the p H-sensitive peak intensity of 4-Mpy changed and the ratio of the Raman peak at 1005 cm^-1/1094 cm^-1 risen after the model particles were digested by Ruditapes philippinarum,indicating that the PS shell permeability of the plastic model particles increased,making the plastic model particles more permeable.H⁺diffused into the model nanoparticles through the pores,suggesting that the PS shell was swollen or degraded.This result is consistent with the in vivo results of Tenebrio molitor with plastic-degrading ability.The Fe₃O₄@Au@PS model particle is expected to be a new method and a new tool to reveal the changes in the properties of nanoplastics in marine organisms,and to rapidly screen potential plastic-degrading species.