*2.2. Electrospinning*

PLLA (molecular weight 85−160 kg mol−1, Sigma-Aldrich, Munich, Germany) was dissolved in a mixture of dichloromethane and acetone (80:20 *v*/*v*) at a concentration of 20% (*w*/*v*) at room temperature. The solution was stirred overnight, then SBA2 was added with a concentration of 7% *w*/*v*. The resulting suspension was vigorously mixed and then stirred again overnight to obtain a homogeneous dispersion of SBA2 in the polymer solution. The solution was put in an ultrasound bath for 1 hour prior the electrospinning with the aim to reduce SBA2 clustering and then transferred in a 1 mL syringe. The spinning process was performed by a 21G stainless steel needle and a syringe pump (Harvard Apparatus, Holliston, MA, United States) with feeding rate 0.8 mL h−<sup>1</sup> and by applying a positive high-voltage of 12 kV (EL60R0.6-22, Glassman High Voltage, XP Power, Milano, Italy) between the needle and a metal collector. Random fibre mats were collected on a static grounded 10 × 10 cm2 collector meanwhile aligned fibre mats were collected on a grounded disk (8 cm diameter, 1 cm thickness) rotating at a speed of 5000 rpm, maintaining constant all the other processing parameters. The air relative humidity and temperature during the electrospinning process were about 40% and 20◦C, respectively. The needle-collector distance was adjusted to 15 cm. Neat PLLA fibres were fabricated as reference material by using identical set-up parameters.
