The overall workflow of this project was: a. Synthesis of ENMs. b. Characterization and stability-testing of ENMs. c. Establishment of an in vitro BBB model. d. Assessment of the transport and distribution of ENMs. e. In vivo validation. The original plan was to synthesize and label a broad library of ENMs, including Fe3O4, CeO2, and GO. However, given budgetary and time limitations, it was decided to focus on Fe3O4, ZnO, CeO2, Ag. The background level of these elements in cells is negligible, so there is no necessity to be labelled. In total, 10 nanoparticles was synthesized. Fe3O4 with two different sizes (Fe3O4 NPs-18nm, Fe3O4 NPs-35nm), CeO2 with three sizes (CeO2 NPs-3nm, CeO2 NPs-7nm, CeO2 NPs-25nm), Ag with four shapes (Spherical Ag nanoparticle (Ag NS), disc-like Ag nanoparticle (Ag ND), rod-like Ag nanoparticle (Ag NR), Ag nanowires (Ag NW)), and ZnO (ZnO NPs). All the particles were characterized using DLS and TEM for the size measurement. Then, an in vitro BBB model displaying key BBB features and functions was successfully set up and validated. It can be used for transport studies. Next, the nanoparticle transport across the BBB was tested using the in vitro BBB model, and analysed by ICP-MS and SP-ICPMS combined with synchrotron radiation-based X-ray absorption fine structure spectroscopy (XAFS). 8 of 10 particles transport across the BBB: CeO2 NPs-3nm, CeO2 NPs-7nm, CeO2 NPs-25nm, Ag NS, Ag ND, Fe3O4 NPs-18nm, Fe3O4 NPs-35nm, and ZnO NPs. For CeO2 NPs-3nm, CeO2 NPs-7nm, CeO2 NPs-25nm, Ag NS, Fe3O4 NPs-18nm, and Fe3O4 NPs-35nm, most of transported elements are in the form of particle. For Ag ND and ZnO, ion accounted for the most of the elements. For Ag NS and Ag NW samples, further LCF analysis of the NEXAFS spectra using standard references compounds showed that the Ag were mainly presented as particulate Ag, with a small proportion as Ag complex (Ag-cystine).
In total, seven papers were generated under this project, published in Nature Protocols, Nano Today, Nanoscale, Small, Environmental Science & Technology, , Environmental International, Environmental Science & Technology Letters. Results have been also disseminated in several international conference including 13th International Conference On The Environmental Effects Of Nanoparticles And Nanomaterials (ICEENN 2018, September 5-8, Duke University, USA), SOT conference 2018 (March 11-15, San Antonio Texas, USA), China Nano 2019 (July 22-26, 2019, Beijing, China), The 10th National Conference on Environmental Chemistry 2019 (15-19 August, 2019, Tianjin, China).
