In vitro performance investigation of bioresorbable scaffolds - Standard tests for vascular stents and beyond.
OBJECTIVE
Biodegradable polymers are the main materials for coronary scaffolds. Magnesium has been investigated as a potential alternative and was successfully tested in human clinical trials. However, it is still challenging to achieve mechanical parameters comparative to permanent bare metal (BMS) and drug-eluting stents (DES). As such, in vitro tests are required to assess mechanical parameters correlated to the safety and efficacy of the device.


METHODS
In vitro bench tests evaluate scaffold profiles, length, deliverability, expansion behavior including acute elastic and time-dependent recoil, bending stiffness and radial strength. The Absorb GT1 (Abbott Vascular, Temecula, CA), DESolve (Elixir Medical Corporation, Sunnyvale, CA) and the Magmaris (BIOTRONIK AG, Bülach, Switzerland) that was previously tested in the BIOSOLVE II study, were tested.


RESULTS
Crimped profiles were 1.38±0.01mm (Absorb GT1), 1.39±0.01mm (DESolve) and 1.44±0.00mm (Magmaris) enabling 6F compatibility. Trackability was measured depending on stiffness and force transmission (pushability). Acute elastic recoil was measured at free expansion and within a mock vessel, respectively, yielding results of 5.86±0.76 and 5.22±0.38% (Absorb), 7.85±3.45 and 9.42±0.21% (DESolve) and 5.57±0.72 and 4.94±0.31% (Magmaris). Time-dependent recoil (after 1h) was observed for the Absorb and DESolve scaffolds but not for the Magmaris. The self-correcting wall apposition behavior of the DESolve did not prevent time-dependent recoil under vessel loading.


CONCLUSIONS
The results of the suggested test methods allow assessment of technical feasibility based on objective mechanical data and highlight the main differences between polymeric and metallic bioresorbable scaffolds.
Institute for Biomedical Engineering, University Medicine Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: wolfram.schmidt@uni-rostock.de.
Wolfram
W
Schmidt
Institute for Biomedical Engineering, University Medicine Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: peter.behrens@uni-rostock.de.
Peter
P
Behrens
Institute for ImplantTechnology and Biomaterials - IIB e.V., Associated Institute of the University of Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: christoph.brandt@uni-rostock.de.
Christoph
C
Brandt-Wunderlich
Institute for ImplantTechnology and Biomaterials - IIB e.V., Associated Institute of the University of Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: stefan.siewert@uni-rostock.de.
Stefan
S
Siewert
Institute for Biomedical Engineering, University Medicine Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: niels.grabow@uni-rostock.de.
Niels
N
Grabow
Institute for ImplantTechnology and Biomaterials - IIB e.V., Associated Institute of the University of Rostock, Friedrich-Barnewitz-Strasse 4, D-18119 Rostock-Warnemünde, Germany. Electronic address: klaus-peter.schmitz@uni-rostock.de.
Klaus-Peter
KP
Schmitz
D020341:Absorbable Implants; D015906:Angioplasty, Balloon, Coronary / Q000295:instrumentation*; D019245:Compressive Strength; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging / Q000628:therapy*; D004548:Elasticity; D019544:Equipment Failure Analysis; D006801:Humans; D008422:Materials Testing; D008670:Metals / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011312:Pressure; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015607:Stents; D013718:Tensile Strength; D013997:Time Factors; D054457:Tissue Scaffolds
D008670:Metals; D011108:Polymers
Biodegradable scaffolds; Cardiovascular stenting; Mechanical performance testing