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Wang, et al.
The radial crush resistance property is an essential to the value of relative cell viability, the cytotoxicity of
indicator to respond the ability of stents to resist radial the medical devices or materials was graded as none
deformation. A parallel plate compression test was (>100%), slight (80 – 99%), mild (50 – 79%), moderate (30
accomplished to record the load and displacement in the – 49%), and severe (0 – 29%). Samples were considered
compression process. Stents with a length of 10 mm and to have cytotoxic effects, as relative cell viability was
a diameter of 3 mm were applied in this test. Stents were <80%. As depicted in Figure S5, the cell viability of
compressed until a radical deformation of 1.5 mm, and RASMCs cultured in the extract of the “Stent + Nano-
the load and displacement were continuously recorded PDLLA-DP” group (48.92 ± 2.05%) showed a significant
in this process. As presented in Figure 3F, the stress– decrease, compared to the “Stent” group (96.14 ± 6.21%)
strain behavior suggested that the radial strength of stents and “Stent + Nano-PDLLA” group (90.40 ± 3.86%). In
with added nanofibers was slightly enhanced compared contrast, there was no significant difference in the cell
to that of the bare stent group. There was no significant viability of HUVECs among the three groups (all >90%),
difference between the “Stent + Nano-PDLLA” group and and all specimens showed no obvious cytotoxic function.
the “Stent + Nano-PDLLA-DP” group. The quantitative
analysis of the stress value when the strain was 50% (2) Cell proliferation and morphology analysis of
further corroborated the above results. RASMCs seeded on stents

3.3. In vitro hemocompatibility evaluation To further demonstrate the cell morphology of
RASMCs and HUVECs on different stents, cytoskeletal
Thrombosis caused by platelet adhesion is a complication immunofluorescence staining and SEM observation were
of stent implantation . Thus, it is necessary to assess carried out. Fluorescent phalloidin was used to bind to
[30]
the hemocompatibility of stents. The platelet adhesion F-actin, which is a key cytoskeletal component and could
test was accomplished in the current study to evaluate help to identify the overall shape and structure of the cell.
the hemocompatibility of vascular implants. The surface However, because of the opaque characteristic of the PCL
morphology of adhered platelets on different stents thick fibers of stents, only cells attached between adjacent
is presented in Figure 4A. The red circles indicate the V-shaped struts could be observed in immunofluorescence
positions of adhered platelets, and the area of the red staining images. Thus, SEM characterization was
circles is proportional to the number of platelets inside. accomplished to show the overall distribution of cells.
Compared to the bare PCL stents, stents coated with As shown in Figure 5A and 5B, RASMCs seeded on
PDLLA nanofibers showed extensively increased platelet the “Stent + Nano-PDLLA” group showed a significantly
adhesion. Remarkably, compared with the “Stent + Nano- higher cell proliferation rate than those seeded on the bare
PDLLA” group, the number of adherent platelets in the stent group. Compared to the “Stent + Nano-PDLLA”
“Stent + Nano-PDLLA-DP” group was significantly group, the “Stent + Nano-PDLLA-DP” group showed
reduced due to the addition of DP agents. significantly decreased cell proliferation. In addition,
Moreover, a hemolysis test can indicate whether the proliferation of RASMCs on day 7 showed no
samples destroy the structure of erythrocytes. As presented significant difference between the bare stents and stents
in Figure 4B, the hemolysis ratios of the three groups were with PDLLA/DP nanofibers. As shown in Figure 5C
less than the safe value (5%). In particular, the “Stent + Nano- and 5D, the surface of bare PCL stents and stents coated
PDLLA-DP” group could intensively reduce the hemolysis with PDLLA nanofibers was sufficiently covered with
ratio to 1.00 ± 0.42%, compared with the hemolysis ratio of RASMCs after culture for 7 days. In the bare PCL stent
2.91 ± 0.44% for the bare PCL stents, and 2.76 ± 0.41% for group (Figure 5C(i) and 5D(i)), RASMCs were only
the stents coated with PDLLA nanofibers. closely deposited on the surface of the PCL struts and

3.4. In vitro biocompatibility assessment exhibited powerful proliferation ability, despite the
limited contact area and microenvironment. Remarkably,
Here, RASMCs and HUVECs were selected to RASMCs crazily overspread the surface of stents coated
investigate the biocompatibility of stents. In particular, with PDLLA nanofibers (Figure 5C(ii) and 5D(ii)). As
we investigated the effect of DP agents released from depicted in Figure 5C(iii) and 5D(iii), the proliferation
stents on cytotoxicity, cell viability and proliferation, and of RASMCs in the “Stent + Nano-PDLLA-DP” group
cell morphology. was significantly suppressed compared with that of
stents coated with only PDLLA nanofibers. It is worth
(1) In vitro cytotoxicity testing mentioning that DP is a pyrimidine derivative and has a
Cytotoxicity is an essential biological indicator in the similar structure to thymine (one of the four constituent
toxicity evaluation of medical devices . According to bases of nucleic acids), leading to the reaction between
[31]
ISO 10993- 5:2009 , the extract test method was applied DAPI and DP. Thus, the cell nuclei of cells seeded in the
[32]
to determine the in vitro cytotoxicity of stents. According “Stent + Nano-PDLLA-DP” group were absent in the
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