Dynamic light scattering

VSOPs C200 were purchased from Ferropharm (Teltow, Germany). They have a diameter of about 11 nm, a 5 nm iron oxide core and a negative surface charge due to the citrate coating. Information about R1 (22.5 mmol⁻¹ s⁻¹ at 0.47 T) and R2 (49.7 mmol⁻¹ s⁻¹ at 0.47 T) relaxivities of VSOP C200 could be found in the publication of Stroh et al. [15 (link)]. For labelling of the cells no additional transfection agent is necessary [3 (link),14 (link),17 ].
Transmission electron microscopy (TEM) was used to determine the morphology and intracellular distribution of the VSOPs. The samples were prepared by drop coating on carbon-coated copper grids after sonication and stabilization. A transmission electron microscope (EM 900, Carl Zeiss, Oberkochen, Germany) was used for evaluation. The investigations were kindly supported and performed by the group of Prof. Dr. Krohne, Division of Electron Microscopy Theodor-Boveri-Institute, University of Wuerzburg.
Dynamic light scattering (Malvern Instruments Ltd., Herrenberg, Germany) was used to determine the size distribution of the VSOPs in the expansion medium. The surface zeta-potential of the dispersion in the expansion medium (pH 7.4) was determined with a ZetaSizer 3000HSA (Malvern Instruments Ltd.). These investigations were kindly carried out by Mrs. Susanne Koch of the ISC Fraunhofer Institute Wuerzburg.

Spherical AuNPs of 60 nm functionalised with PDDAC were synthesized in-house using the Turkevic method, as reported before [19 , 68 ]. The AuNPs have a zeta potential of at least + 30 mV, as verified by dynamic light scattering (Malvern Instruments, Worcestershire, UK).

To measure particles, all of the nanoemulsions are diluted at a ratio of 1:50 in oil to prevent multiple particle scattering. The mean particle size (Z_average) and polydispersity index (PDI) were determined by dynamic light scattering (Malvern Instrument) at the temperature of 25°C and an angle of 90°.

The morphology of the exosomes was evaluated via transmission electron microscopy (TEM), and the particle distribution and size were evaluated via dynamic light scattering (Malvern Instruments, Malvern, UK). For TEM, exosomes were placed on a transmission electron microscopy grid, and the excess solution was removed by blotting with filter paper. The exosomes were negatively stained with uranyl acetate at room temperature. The exosomes were then observed using a transmission electron microscope (Hitachi, Tokyo, Japan). For nanoparticle tracking analysis, exosomes were analysed using the NanoSight® software program. The results showed the particle size distribution vs. the intensity (percent).

To compare the effect of the optimized exposure medium with traditional media on the stability of AgNP suspensions, a representative AgNPs (AgNP_CIT20, 4 mg L⁻¹ as total Ag) were prepared in OECD SM4 medium (which included most components of M459 but excluded CoCl₂, KI, Na₂SeO₃, NH₄VO₃ and Vitamins), EPA hard water60 , 0.1 mmol L⁻¹ NaNO₃ medium and ultrapure water, respectively. The total Ag⁺ release from AgNP_CIT20 in these media were monitored during the 8-h exposure. After 8-h exposure, the characterizations of AgNP_CIT20, including UV-vis spectra (UV-3600 Spectrometer, Shimadzu, Japan), TEM imaging (preformed on H-7500 (Hitachi)), hydrodynamic sizes (Dynamic Light Scattering, DLS, Malvern, UK) and photographing of these samples were performed. TEM samples were prepared by loading 10 μL aliquots of suspensions onto ultrathin carbon-coated copper grid, and drying at room temperature under vacuum.

The particle size distribution and ζ-potential of these NPs were measured using dynamic light scattering (Malvern Instruments, Malvern, Worcestershire, UK).

Zeta potential measurements were performed using dynamic light scattering (Malvern Instruments, Malvern, U.K.) applying PALS zeta potential analyzer software as previously described [14 (link)]. The sample was run at least three times and each run lasted 50 cycles at 298 K with the Smoluchowski model. The zeta potential in millivolt units was calculated as the electrophoretic mobility (μm/cm[V·s]⁻¹).