2.10. ABTS Antioxidant Assay

The green colored ABTS•⁺ free radical cation solution was obtained by mixing equal volumes of a 7.4 mM aqueous solution of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) and a 2.6 mM aqueous solution of potassium persulphate, then allowing them to react overnight in the dark at room temperature. Prior to assay, the obtained ABTS•⁺ solution was diluted with ethanol to an absorbance of ~0.77 ± 0.05 measured at 750 nm.

Amounts of ~8 mg of electrospun fibers from each sample were kept in 5 mL solution 95/5 ethanol/water (v/v); the vials were left shaking overnight at 23 °C and 120 rpm in a thermostated bath. 50 μL of supernatant from each sample or pure αT were added to 1 mL of the diluted ABTS•⁺ solution and the absorbance at 750 nm was read after 10 min incubation in the dark at room temperature. Control sample was prepared with 50 μL ethanol added to 1 mL ABTS•⁺ solution. The absorbance at 750 nm of each sample was read using a Cary 60 UV–Vis spectrophotometer (Agilent Technologies) and the RSA% inhibition of ABTS•⁺ was calculated with the same Equation (2) as for DPPH.