Plga cooh

PTX-loaded PLGA NBs (PTX-PLGA NBs) were generated using a water/oil/water double emulsion. Briefly, 50 mg PLGA-COOH (50:50, molecular weight [MW] =12.3 kDa, Jinan Daigang Biomaterial Co., Ltd, Shandong, People’s Republic of China) was directly dissolved in 1.5 mL of dichloromethane and mixed with 5 mg of PTX (Haoxuan, Xian, People’s Republic of China) and 0.2 mL of Milli-Q water under sonication (VCY-500; Yongyan, Shanghai, People’s Republic of China) with an amplitude of 20% for 1.5 min to obtain the first emulsion (first emulsion). The first emulsion was immediately poured into 8 mL of a poly(vinyl alcohol) (PVA; Sigma-Aldrich Co., St Louis, MO, USA) solution (4%, w/v) and sonicated for 1 min to form a double emulsion (second emulsion). Following dichloromethane evaporation to solidify the PTX-PLGA, the double emulsion was transferred into 20 mL of isopropanol (2%, v/v) and continuously stirred for 2–4 h at room temperature to extract dichloromethane. The obtained PTX-PLGA nanoparticles were further collected through centrifugation at 8,000 rpm for 10 min and washed three times using Milli-Q water, subsequently lyophilized for 48 h, and filled with perfluoropropane gas. A lyophilized powder of PTX-PLGA NBs was obtained and sealed at 4°C until further use. NBs without the addition of PTX were used as pure PLGA NBs.