Figure 4 . Comparison of NPC43 cell disruption ratio with
different treatments. (a) Optical images of NPC43 cells incubated with
PTX and PEG-PTX NPs for 16 h in 100×100 μm2 microwells
without and with glass cover. Cell disruption was highlighted in red
circles. Percentage of cell disruption after PTX and PEG-PTX NPs
addition for 16 h in different microwells (b) without cover and (c) with
cover. Number of NPC43 cells
counted is marked in white.
To study the cytotoxicity of PTX and PEG-PTX NPs, the percentage of cell
disruption was calculated as shown in Supporting Table S2. As shown inFigure. 4a and Supporting Figure. S5-S6, some cells ruptured
after NPC43 cells were treated with PTX or PEG-PTX NPs for 16 h in
microwells with different sizes. As shown in Figure. 4b-c, the size of
microwells had no effect on cell division. Therefore 100×100
μm2 microwells were used for further
explanation. In 100×100
μm2 microwells without a cover, the percentages of
cell disruption after PTX and PEG-PTX NPs addition for 16 h were
14.01±3.66% and 10.77±3.92%, respectively. However, the percentage of
cell disruption was only 4.42±3.50% for cells without any treatment.
This result showed that PTX was more effective to treat NPC43 cells than
PEG-PTX NPs, which was consistent with the result from the MTT assays.
Furthermore, in 100×100 μm2 microwells with a cover,
the percentages of cell disruption after PTX and PEG-PTX NPs addition
for 16 h were 13.12±3.44 and 12.23±5.26%, respectively. After NPC43
cells were treated with PEG-PTX NPs for 16 h, slightly more cells
reptured in microwells with a cover compared to microwells without a
cover. In the presence of PEG-PTX NPs, the additional confinement by the
cover led to an increase in cell disruption. In addition, similar
results were obtained for 50×50 and 150×150 μm2microwells.
2.3. NPC43 cell behaviors with PTX and PEG-PTX NPs
treatments
Because cell migration speed is a key indicator for cell behaviors and
PTX could inhibit cell motility, cell migration speed was monitored
after cells were treated with PTX and PEG-PTX NPs in different
microwells. Additionally, cells on flat surface were also tested for
comparison. As shown in Supporting Figure. S7, for cells without any
treatment, the migration speed of NPC43 cells decreased a little in 16
h. However, after NPC43 cells were incubated with PTX, the migration
speed decreased to 0.1 μm/min after PTX treatment for 5.4 h. The time
when the cell migration speed was equal to 0.1 μm/min was defined as
t0.1. NPC43 cells moved slower after treated with PTX
for 5.4 h because small molecule PTX could act directly on tubulin to
inhibit cell movement. However, for cells treated with PEG-PTX NPs,
t0.1 was 12.4 h which demonstrated that PEG-PTX NPs
could continuously release PTX to slow down the NPC43 cell motility.