The Development of Analytical Detection Methods for Different Types of Nanoplastics in Human Placenta Tissue

Abstract

The environment is one of the birthplaces of micro- and nanoplastics (MNPs), originating from the accumulating plastic waste present in the environment. These particles have already been found in several organisms and even in several human organs, for example the placenta. Thus, exposure of the unborn child to MNPs is possible. Health risk assessments for MNPs are in high demand, as complications during this precious and fragile stage of human life can cause lifelong health issues. However, knowledge gaps exist on the detection of MNPs in biological matrices, especially for nanoplastics (NPs), due to detection limitations for the small size of NPs. Hence, health risk assessments of NPs are absent. Additionally, health risk assessments cannot be performed properly at this moment, since the diversity of plastic types in the MNPs research field are lacking, caused by the absence of commercial NPs other than polystyrene. For all these reasons, this thesis aims to contribute to the development of detection methods for different types of NPs in placental tissue. In order to achieve this aim, in-house synthesized fluorescently dyed polymethyl methacrylate and polyvinyl chloride NPs (FPMMA and FPVC) were used for the spiking of human placental tissue. First, a dispersion protocol was developed for both polymeric NPs and analysed by Dynamic Light Scattering (DLS) to examine the success of the dispersion protocol. The final dispersion protocol consists of adding either 300 µg FPMMA or 350 µg of FPVC to 5 mL of a sodium dodecyl sulphate (SDS) solution with a SDS concentration of respectively 0.2 mg/mL or 0.5 mg/mL. Sedimentation was observed, however, after decantation, moderately monodispersed dispersions were obtained for both aforementioned polymeric NPs. Changing the pH, surfactant or adding salts to the dispersions may improve the dispersity of NPs in SDS solutions and are recommended for further research. Secondly, human placental tissue was spiked with dispersed FPMMA and FPVC. A previously in-house developed digestion protocol was utilised to digest the spiked placental tissue. The obtained aliquots and the dispersions were analysed by Confocal Fluorescence Microscopy (CFM) to discover the relative recovery rate of the utilised NPs, i.e. how many particles can be detected after the digestion. For FPVC, a recovery rate of 157 % was found and for FPMMA a recovery rate of 48% was found. However, further analysis with CFM shows that these percentages are not representative as recovery rates, because a major part of the particles was missed during the analysis. Therefore, the CFM is at this stage not suited as a quantitative tool. Adaptations of the software to analyse CFM images at higher magnifications could potentially result in a detection method that can be used as a quantitative tool to better estimate recovery rates of the NPs. Overall, the results presented in this thesis give direction to further development of the detection methods for different types of NPs in complex biological matrices.