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Qiu et al. Vessel Plus 2018;2:12 I http://dx.doi.org/10.20517/2574-1209.2018.13 Page 3 of 15

Figure 1. Stent in crimped and deployed configurations [11]

7
6
Stent diameter (mm) 5 4 3

2

1
0 1 2 3 4 5 6 7 8
Balloon pressure (bar)

Figure 2. Stent diameter change against balloon pressure during expansion [11]

of degradation. This paper offers a review of current research status of biodegradable polymeric scaffolds,
covering both experimental and modelling work.

EXPERIMENTAL STUDIES OF BRSS
Mechanical behaviour
Stents, as medical devices used in human bodies, impose difficulties and challenges for experimental
studies due to their tiny size and complex design. Despite the challenges, various methods have already
been developed to investigate the behaviour of stents, including polymeric stents. Grabow et al. studied
[11]
the expansion behaviour of a biodegradable slotted tube stent, made of PLLA and poly-hydroxybutyric acid
(PHB), by stent bench testing. As shown in Figure 1, the crimped stent was mounted on a balloon catheter,
and then expanded by balloon inflation. All stents were expanded successfully without the occurrence of strut
fracture, and Figure 2 shows the stent diameter change as a function of balloon pressure. The stent initially
expanded rapidly at a balloon pressure of 1-2 bars and then achieved full expansion at a pressure of 6 bars.
The measured recoil effect and collapse pressure were 4.2% and 1.1 bars, respectively. These results revealed
that the PLLA/PHB slotted tube stent exhibited adequate mechanical properties during rapid expansion
process. The same method was also used by Grabow et al. to investigate the mechanical performance of
[12]
two types of biodegradable balloon-expandable stents, made of PLLA and PLLA/PCL/TEC, respectively.
Both types of stents were able to expand fully by balloon inflation under a pressure of 8 bars, but differences
were observed for expansion process as shown in Figure 3. Specifically, the PLLA/polycaprolactone (PCL)/
TEC stent expanded immediately with the balloon inflation while the pure PLLA stent started to expand at