Pes syringe filters

HTS and TS were identified and quantified by an Alliance 2695 HPLC system (Waters, Milford, MA, USA) coupled with a 2475 Multi λ detector (FLD) with Xenon lamp, according to modified method of Tsarbopoulos and co-workers [35 (link)]. Samples were prepared by filtration through 0.45 µm PES syringe filters (Macherey–Nagel, Düren, Germany). Chromatographic separation was conducted by injecting 20 µL of sample on a reversed phase column (250 × 4.6 mm, 5 µm) (Agilent Zorbax Eclipse Plus C18, Santa Clara, CA, USA). Mobile phases were 0.05 M sodium acetate buffer pH 5 and acetonitrile with the flow rate of 1 mL/min. Elution was conducted over 20 min at 25 °C. Identification was performed with FLD set at the excitation wavelength of 280 nm, and emission wavelength of 316 nm. Polyphenols were identified by comparing the retention times of the eluting peaks with those of the standards. Peaks were quantified by using the Empower2 software (Waters, Milford, MA, USA) and compared to external standard calibration. Standard stock solutions were prepared by dissolving reference compounds in DMSO. Aliquots of these solutions were further diluted with ultrapure water to obtain calibration curve (1–81 mg/L).

The amount of betulin entrapped within fiber mats was estimated by dissolving approximately 20 mg of electrospun fiber mat, exactly weighed, in 30 mL ethanol:water (50:50 v/v) solution by means of sonication at 65 °C (Sonorex RK 31H, Bandelin, Berlin). Samples were then filtered using hydrophilic polyethersulfone (PES) syringe filters (Macherey-Nagel, Düren, Germany), and the total amount of drug extracted was quantified by High Performance Liquid Chromatography with Ultraviolet detection (HPLC-UV). The percentage entrapment efficiency (%EE) was calculated by the following Equation (1): $\% \mathrm{EE}=\frac{\mathrm{Total} \mathrm{mass} \mathrm{of} \mathrm{drug} \mathrm{extracted} \mathrm{from} \mathrm{nanofiber}}{\mathrm{Mass} \mathrm{of} \mathrm{total} \mathrm{drug} \mathrm{added} } \times 100\%$

Prior to SeNP synthesis, lyophilized OPE was dissolved in ultrapure water to give a 10 mg/mL solution and filtered through a 0.45 μm polyethersulfone (PES) syringe filters (Macherey-Nagel, Düren, Germany).
To synthesize SeNPs, 15 mg of raw or purified mandarin peel pectin was weighed directly into a 50 mL Erlenmeyer flask, 28 mL ultrapure water (23 mL for functionalized samples) was added under magnetic stirring (350 rpm), followed by the addition of 1 mL of ascorbic acid (1 M)—acting as a reducing agent and 5 mL of OPE (1%) to the functionalized samples. Finally, 1 mL of Na₂SeO₃ (0.1 M) was added dropwise, changing the color of the reaction mixture to red. When the reaction was completed (after 20 min), the reaction mixture was purified from the remaining reactants by dialysis. The end of cellulose dialysis tubing (D9527-100FT, Sigma-Aldrich, St. Luis, MO, USA) was folded twice, closed with a sealing clip (Bevara 6 cm, IKEA, Delft, Netherlands), filled with the reaction mixture, closed and submerged in a beaker filled with 950 mL ultrapure water. The dialysis was performed according to a previously described procedure [16 (link)]. The composition of non-functionalized SeNPs stabilized with raw pectin (M) and purified pectin (Mpr) in comparison to OPE-functionalized samples stabilized with raw pectin (Mf) and purified pectin (Mprf) are presented in Table 1.