Figure 2 . Characterization of PEGylated paclitaxel nanoparticles (PEG-PTX NPs). (a) Schematic illustration of PEG-PTX NPs synthesis. (b) Size distribution and 7-day stability of PEG-PTX NPs measured by dynamic light scattering. Inserted images: PEG-PTX dissolved in dimethylformamide (left) and PEG-PTX NPs in water (right). (c) Scanning electron micrographs of PEG-PTX NPs. (d) Cell viability of NPC43 cells treated with PTX and PEG-PTX NPs for 16, 40, and 64 h, respectively. One-way ANOVA and Tukey’s post hoc tests, NS – not significant and *p <0.05.
PEG-PTX was synthesized according to previously reported work.[48-50] PEG is hydrophilic and PTX is hydrophobic so the amphiphilic PEG-PTX could self-assemble into nanoparticles (PEG-PTX NPs) in water by the nanoprecipitation method as shown in Figure. 2a . The diameter and polydispersity index (PdI) of PEG-PTX NPs were measured by dynamic light scattering (DLS). As shown in Figure. 2b, the diameter and PdI of PEG-PTX NPs were 114 nm and 0.24, respectively. After storing at room temperature for 7 days, the diameter and PdI of PEG-PTX NPs remained unchanged, which showed that the synthesized PEG-PTX NPs were stable. As shown in the inserted photos of Figure. 2b, PEG-PTX NPs in water showed the clear Tyndall effect as a bright light path in water was observed when irradiated by a laser, which indicated that nanoparticles were successfully synthesized in water. However, PEG-PTX could be dissolved in dimethylformamide (DMF) so there were no nanoparticles or Tyndall effect in DMF. The morphology of PEG-PTX NPs was revealed by a scanning electron microscope (SEM). As shown in Figure. 2c, the diameter of some PEG-PTX NPs was below 100 nm. Overall, the PEG-PTX NPs had a little smaller size than that measured by DLS as shown in Figure. 2b because the hydration layer was used in DLS but the dry sample was used in SEM. These results demonstrated that stable PEG-PTX NPs were successfully formed for the biological experiments.