*3.4. Electrospinning*

StarPLA-PTES were dissolved in TFE at concentrations ranging from 15 to 25 wt%. In order to activate the sol gel process, 10 μL of HCL (0.1 M in ethanol) was added per mL of polymer solution. After one minute of agitation using a vortex, the mixture was loaded into a syringe with a 21-G needle and fixed on a syringe pump (KDS100, KD Scientific,). To start the electrospinning process, a voltage of 15 kV was applied to the polymer solution, which was dispensed at a flow rate of 0.5 mL·h−1. The nanofibers were collected on a flat collector that was placed 15 cm from the syringe needle. The experiments were performed at 25 ± 1 ◦C with a relative humidity of 48 ± 3%. All the tests were carried out under the same conditions.

## *3.5. Characterization Methods*

Size exclusion chromatography (SEC) was conducted using a Shimadzu LC-200AD Prominence system (Shimadzu, Marne-la-Vallée, France) equipped with a PLgel MIXED-C guard column (Agilent, 5 μm, 50 mm length × 7.5 mm diameter), two PLgel MIXED-C columns (Agilent, 5 μm, 300 mm length × 7.5 mm diameter) and a RID-20A refractive index signal, using poly (ethylene glycol) as calibration standard with a flow rate = 1 mL·min−1. The polymer was solubilized in THF at 10 mg·mL−1; 200 μL of this solution was injected in the system. 1H-NMR measurements were carried out at 300 MHz with an AMX300 Bruker

spectrophotometer (Cambridge Scientific Products, Watertown, USA) at room temperature using deuterated chloroform as solvent. Fourier transform infrared analysis was performed using a Perkin Elmer Spectrum 100 (PerkinElmer France, Villebon-sur-Yvette, France); four scans were performed at room temperature in the range of 4000–650 cm<sup>−</sup>1.

For scanning electron microscopy (SEM), the samples were sputter coated with a 10 nm (2 min) thick gold film and imaged under a scanning electron microscope (Phenom-world ProX) using an accelerating voltage of 15 kV. Micrographs were analyzed with ImageJ (https://imagej.nih.gov/ij/download.html (accessed on 12 April 2021)). The diameter of the fibers was measured with the same software by drawing a perpendicular line on both edges of the fiber (number of fibers measured for each condition = 50).

The differential scanning calorimetry (DSC) analysis was conducted under argon with a Mettler Toledo 3 Star DSC system. A total of 3 mg of each nanofiber sample was weighed into a standard aluminum dish. The thermal cycle consisted of a heating sweep from 0 ◦C to 200 ◦C (10◦C·min−1) followed by cooling to −10 ◦C (10◦C·min−1) and a second heating sweep to 300 ◦C (10◦C·min−1). The glass transition temperature (Tg) was measured on the first ramp of heating.

## *3.6. Gel Fraction*

For each condition, gel fraction was measured by weighing 3 samples (wi) followed by immersion in 3 mL of DCM under agitation for 3 h. Next, the DCM solution was centrifugated (3000 rpm for 10 min) to separate the insoluble and soluble fractions. After drying under vacuum for 24h, the insoluble fractions were weighed (winsoluble). Gel fraction was calculated with Equation (1) after verifying that the addition of soluble and insoluble phases was 100% of the initial sample weight:

$$\text{Gel fraction } \left( \% \right) = \left( \text{w}\_{\text{irrsolable}} / \text{w}\_{\text{i}} \right) \times 100 \tag{1}$$

## *3.7. Tensile Tests*

Mechanical properties were measured on C, G, H samples (3 cm wide × 1 cm length, n = 4) after different degradation time points, using uniaxial tensile testing on an Instron 3344 testing system at a speed of 5 mm·min−<sup>1</sup> and at 37 ± 1 ◦C. The Young's modulus (E, MPa) was calculated based on the initial linear section of the stress–strain curve and was reported as the mean value of the measurements.

#### *3.8. Nanofibers Behavior in a Physiological Environment-Like over Time*

Electrospun scaffolds (10 mm length × 30 mm wide, 7.5 ± 3 mg) were weighed (mi = initial mass) and then immersed in 6 mL of PBS (pH = 7.4) at 37 ◦C under constant stirring. Samples were removed from PBS at months one, three and six and their mass loss, gel fraction and mechanical properties were evaluated using quadruplicates.

The water uptake and mass loss were calculated from Equations (2) and (3), respectively:

> Water uptake (%) = ((m w − mi)/mi) × 100 (2)

$$\text{Mass loss (\%)} = ((\text{m}\_{\text{i}} - \text{m}\_{\text{d}})/\text{m}\_{\text{i}}) \times 100\tag{3}$$

where m w is the hydrated mass of the scaffolds and md is mass after vacuum drying overnight.

The gel fraction and mechanical properties of degraded samples were evaluated following protocols described in Sections 3.6 and 3.7, respectively.

## *3.9. Biological Evaluation In Vitro*

NCTC-Clone 929 cells (mouse fibroblast cell line (ECACC 85011425)), passage 32, were cultured in 500 mL MEM with 5 mL glutamax (1% stabilized glutamine), 50 mL horse serum, and 100 U/mL penicillin and streptomycin 100 μg/mL.
