Manufactured nanoplastic particles (NPs) are indispensable for in vitro and in vivo testing and a health risk assessment of this emerging environmental contaminant is needed. The high surface area and inherent hydrophobicity of plastic materials makes the production of NPs devoid of any contaminants very challenging. In this study, we produced nanoprecipitated polyethylene terephthalate (PET) NPs (300 nm hydrodynamic diameter) with an overall yield of 0.76%. The presence of the ionic surfactant sodium dodecyl sulfate (SDS) was characterized by ¹H NMR, where the relative ratio of NP/surfactant was monitored on the basis of the chemical shifts characteristic of PET and SDS. For a wide range of surfactant/NP ratios (17:100 to 1.2:100), the measured zeta potential changed from −42.10 to −34.93 mV, but with an NP concentration up to 100 μg/mL, no clear differences were observed in the cellular assays performed in protein-rich media on primary human cells. The remaining impurities contributed to the outcome of the biological assays applied in protein-free buffers, such as human red blood cell hemolysis. The presence of SDS increased the NP-induced hemolysis by 1.5% in protein-rich buffer and by 7.5% in protein-free buffer. As the size, shape, zeta potential, and contaminants of NPs may all be relevant parameters for the biological effects of NPs, the relative quantification of impurities exemplified in our work by the application of ¹H NMR for PET NPs and the ionic surfactant SDS could be a valuable auxiliary method in the quality control of manufactured NPs.

Manufactured nanoplastic particles (NPs) are indispensable for in vitro and in vivo testing and health risk assessment of this emerging environmental contaminant. High surface area and inherent hydrophobicity of plastic material, makes production of NPs devoid of any contaminants very challenging. In this study we produced nanoprecipitated polyethylene terephthalate (PET) NPs (300 nm hydrodynamic diameter) and characterized presence of ionic surfactant sodium dodecyl sulfate (SDS) by 1H NMR. Relative ratio of NP/surfactant was monitored on the basis of chemical shifts characteristic for PET and SDS. For a wide range of surfactant/NP ratio (1:17 to 1:1.2), measured zeta potential changed from -42.10 to -34.93 mV, but no clear differences were observed in cellular assays performed in protein-rich media on primary human cells. The remaining impurities contributed to the outcome of biological assays applied in protein-free buffers, such as human red blood cells hemolysis. As size, shape, zeta potential and contaminants of NPs may all be relevant parameters for biological effects of NPs, relative quantification of impurities exemplified in our work by application of 1H NMR for PET NPs and ionic surfactant SDS could be a valuable auxiliary method in quality control of manufactured NPs.