Resomer rg 503

Recombinant human VEGF (PeproTech, London, UK) and recombinant murine GDNF (Peprotech) enclosing PLGA (50:50; lactic/glycolic [%]) (Resomer^® RG 503; Boehringer Ingelheim, Ingelheim, Germany) NS were prepared as previously described.20 (link)
Briefly, 133 mg PLGA 50:50 (previously sterilized by gamma radiation) were dissolved in 3.33 mL dichloromethane and emulsified with 200 μL of 0.15% w/v Recombinant human VEGF or recombinant murine GDNF aqueous solution (containing 7% [w/v] human serum albumin and 2.5% [w/v] poly-ethylene-glycol 400) by probe sonication for 30 seconds at 50 W (Branson^® Sonifier^® 250, Biogen, Derio, Spain). The first emulsion was poured into 5% (w/v) polyvinyl alcohol solution and sonicated again for 1 minute, in order to obtain a double emulsion (w₁/o/w₂). This emulsion was poured into 2% (v/v) isopropanol solution and stirred at room temperature for 2 hours to promote the removal of the organic solvent. The newly formed NS were separated by centrifugation at 20,000× g, resuspended in 2.5% (w/w in respect to PLGA) trehalose aqueous solution and freeze-dried for 24 hours. The entire process of NS preparation was conducted under aseptic conditions. Empty NS (without VEGF or GDNF) were prepared using the same method described above.

The PLGA used was commercially available (Resomer^® RG 503; Boehringer Ingelheim, Ingelheim, Germany) and had a lactide-to-glycolide ratio of 50:50 and a molecular weight of 33,000 Da. Commercial-grade vancomycin hydrochloride and ceftazidime hydrate were obtained from Sigma-Aldrich (St Louis, MO, USA). The solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) was also purchased from Sigma-Aldrich.
The electrospinning setup used in this study consisted of a syringe and needle (0.42 mm internal diameter), a ground electrode, an aluminum sheet, and a high-voltage supply. The needle was connected to the high-voltage supply, which generated positive DC voltages and currents up to 35 kV and 4.16 mA/125 W, respectively. To prepare the membranes, PLGA, vancomycin, and ceftazidime of various polymer-to-antibiotic weight ratios (260/10/10, 240/20/20, 230/25/25 in mg/mg/mg, respectively, denoted Groups 1–3) were dissolved in 1 mL of HFIP. The solution was then delivered and electrospun by a syringe pump with a volumetric flow rate of 3.0 mL/h to obtain a 0.110 mm-thick membrane. The distance between the needle tip and the ground electrode was 12 cm, and the positive voltage applied to the polymer solution was 17 kV. All electrospinning experiments were carried out at room temperature. All manufactured nanofibers were placed in a vacuum oven at 40°C for 72 hours to evaporate the solvents.

Multilayered drug-loaded PLGA membranes were prepared using an electrospinning setup. The materials used included PLGA 50:50 polymer (Resomer RG 503; Boehringer Ingelheim, Ingelheim, Germany), lidocaine hydrochloride, and ketorolac (Sigma-Aldrich Co., St Louis, MO, USA). Membranes with two different PLGA-to-drug ratios (6:1 and 4:1) were produced. To prepare the drug-eluting membranes with 6:1 polymer-to-drug ratio, PLGA/lidocaine (240 mg: 40 mg) and PLGA/ketorolac (240 mg:40 mg) were first dissolved in 1 mL of hexafluoroisopropanol (HFIP; Sigma-Aldrich Co.). The PLGA/lidocaine solution was then conveyed and electrospun by the syringe pump into a nonwoven form of nanofibrous membrane. This was followed by the electrospinning of PLGA/ketorolac solution. The same procedures were followed to produce the membranes with 4:1 polymer-to-drug ratio, except that the polymer/drug amounts used were 224 mg:56 mg, respectively.

The PLGA used in this study was a commercially available material (Resomer RG 503, Boehringer, Ingelheim, Germany) with a lactide:glycolid ratio of 50:50. The drug used was commercial grade vancomycin hydrochloride (Sigma-Aldrich, Saint Louis, MO, USA).
The drug-eluting nanofibrous membranes were prepared using an electrospinning process. The electrospinning setup consisted of an adjustable, high-DC-voltage power supply, a syringe pump and needle (internal diameter 0.42 mm), a ground electrode, and an aluminium sheet. The needle was connected to the high-voltage supply, which generated positive DC voltage (up to 35 kV) and current (up to 4.16 mA/125 W). For nanofibre preparation, PLGA (1,250 mg) and vancomycin (250 mg) were first dissolved in 5 mL of 1,1,1,3,3,3-hexafluoro-2-propanol (Sigma-Aldrich, USA). The solution was then delivered and electrospun using a syringe pump at a volumetric flow rate of 1.8 mL/hour. The distance between the needle tip and the ground electrode was 12 cm, and the positive voltage applied to the polymer solutions was 17 kV. All electrospinning experiments were conducted room temperature. The electrospun nanofibres were collected in membrane form on the aluminium sheet, and the thickness of the membrane was measured to be 0.11 mm.