Preparation Of Magnetic Polystyrene-Based Nanoplastics And Quantitative Analysis By Intracellular MRI

Plastics have spread to every corner of the globe,and once they decompose into nanoplastics（NPs）,they will cause even greater harm.NPs are difficult to isolate from the natural environment by conventional methods and their elemental composition is similar to that of living organisms.Therefore,it is still very difficult to quantitatively study NPs in living organisms.At present,nanoplastic models are usually used to quantitatively study the biological toxicity of NPs.Fluorescence spectrophotometry is the primary method used to study NPs biotoxicity.However,the results of the quantitative research remain controversial.Other methods,such as SERS,TOC,and Py-GC/MS,have been used for the quantitative analysis of NPs in vitro but have not shown the potential of quantifying NPs in vivo.Magnetic resonance imaging（MRI）has excellent spatial resolution and deep tissue penetration;thus,confounding results can be avoided by using MRI to quantify NPs in living organisms.The specific content is as follows:A cross-linked magnetic polystyrene NPs（Fe₃O₄@PS）with a core-shell structure was successfully prepared by double miniemulsion polymerization.The effects of the amount of cross-linking agent and the concentration of magnetic fluid in the magnetic microemulsion on the physical and chemical properties of Fe₃O₄@PS were studied.Using a self-made magnetic separation device,Fe₃O₄@PS was magnetically separated to obtain Fe₃O₄@PS seeds with uniform size.Functionalized magnetic PS NPs were prepared by a two-step seed emulsion polymerization method,controlling the amount of acrylic acid（AA）and acrylamide（AM）comonomers.To explore its effect on the particle size distribution of functionalized PS micro-NPs,the content of functional groups on the surface and the Zeta potential.For carboxylated magnetic PS NPs,with the increase of AA content,the carboxyl content and Zeta potential on the surface of carboxylated magnetic PS NPs first increased and then decreased;The amide group content and Zeta potential on the surface of amidated magnetic PS NPs increased with the increase of AM monomer addition.Standard cell viability assays were performed using the CCK-8 method.The functionalized nanoplastic model showed significant cytotoxicity in mouse macrophages when the exposure time reached 72 h.Based on the MRI data of three nanoplastic models,standard curves of intensity and concentration were fitted by linear.According to the standard curve,the intensity and concentration relationship equations were fitted to calculate the mass of NPs in the mouse macrophages.The accuracy of the MRI results was demonstrated by inductively coupled plasma（ICP）.Quantitative results from MRI and ICP revealed higher rates of uptake by macrophages in mice exposed to lower concentrations of NPs.When the exposure concentration of the three nanoplastic models was 10μg/mL,according to the ICP results,the uptake rates of mouse macrophages were 63.00%,54.25%and 64.05%,respectively.The quantitative results of MRI technology were slightly lower than that of ICP,and the uptake rates of mouse macrophages at the same concentration were 57.70%,48.40%and 58.20%,respectively.Since the MRI quantitative method can effectively eliminate the interference of background iron,it has a significant advantage in the quantitative detection of iron content in organisms.In summary,MRI technology can provide a new perspective for the quantitative analysis of intracellular NPs.