Fig 1.
A) photograph and B) schematic drawing of the biodegradable self-expandable SX-ELLA stents. LN is the total nominal length of the unloaded stent; D1, D2 are the nominal stent diameters; LH is the length of a single turn of a single helix of the unloaded stent (helix length).
Fig 2.
Photograph and scheme of the dedicated tool for shear modulus measurement.
The device consists of a solid frame denoted by A, a fixed Jacobs microchuck denoted by B, a revolving Jacobs microchuck, denoted by C, tightly connected to a pair of pulleys, and a pulling wire, denoted by E, connected to the “pulling” pulley on one side and the Instron force transducer on the other side (marked by the arrow). The tested specimen (wire) is denoted by D. The thick gray dashed line denotes the elastic reverting element connected to the “reverting” pulley on one side and to the solid frame on the other side. DRP is the diameter of the “pulling” pulley; d is the stent wire diameter; LW is the specimen (wire) length.
Fig 3.
Details of the custom holding tool.
The tool consists of a hollow cylinder with one open end and one closed end. A hook is mounted to the closed end, allowing its attachment to the measuring device. There are three small holes in the cylinder shell for the transverse attachment of stainless-steel needles.
Fig 4.
Scanning electron micrographs of polydioxanone filament: A) surface at magnifications of 100x and 200x; B) and C) fracture at magnifications of 100x and 200x. The white line corresponds to a size of 100 μm.
Fig 5.
TGA results for the 3rd monofilament stent wire sample.
The black line shows the dependence of the relative sample weight on the temperature. The blue dashed line shows the dependence of the rate of the change of the sample weight (derivate weight) on the temperature. The derivative thermal gravimetric (DTG) peak is observed at 234°C.
Fig 6.
Chromatogram and mass spectrum (shown in the inset) for the 3rd monofilament stent wire sample from GCMS analysis.
The red curve in the chromatogram shows the relative intensity, with a single peak detected at 4.33 min. The maximum relative intensity (100%) is derived from the maximum peak, which corresponds to the carrier gas N2 (not shown). The red vertical lines in the mass spectrum in the inset show the relative intensity for the detected ions. The maximum relative intensity (100%) is derived from the maximum peak m/z = 28, which corresponds to the carrier gas N2. The molecular ion peak has a value of m/z = 102, which corresponds to the molecular weight of a dioxanone monomer.
Fig 7.
Force relaxation over time for the selected stent sample.
The samples were measured in an air-conditioned chamber at a constant temperature of (37 ± 0.3)°C. The difference between the maximum and minimum relative humidity values did not exceed 10%.
Fig 8.
Force relaxation of all samples at selected time steps.
The samples were measured in an air-conditioned chamber at a constant temperature of (37 ± 0.3)°C. The difference between the maximum and minimum relative humidity values did not exceed 10%. The asterisk (*) indicates the statistically significant force relaxation of the respective time step compared to the previous time step. The red plus sign (+) indicates the calculated force value using the generalized Maxwell model.