PLGA-b-PEG-COOH synthesis

PLGA-PEG-COOH polymer was synthesized using EDC/NHS chemistry. Briefly, 500 mg PLGA-COOH (0.071 mmol) and 109 mg EDC (0.7 mmol) were dissolved in 7 mL DCM, under magnetic stirring at room temperature for 10 min. Then, 160 mg NHS (1.4 mmol) was dissolved in 7 mL DCM, followed by dropwise addition into the above solution. The reaction was conducted overnight at room temperature. PLGA-NHS was washed with cold 1:1 methanol/diethyl ether mixture for three times, collected by centrifugation, and lyophilized. Then, 200 mg PLGA-NHS (0.028 mmol) was dissolved in 5 mL DCM under magnetic stirring at room temperature for 10 min. 30 mg NH₂-PEG-COOH (0.03 mmol) and 60 µL DIEA (0.28 mmol) were dissolved in 2 mL DCM, and dropwise added into the PLGA-NHS solution. The reaction was conducted overnight. The conjugated PLGA-b-PEG-COOH polymer was washed with cold, 1:1 v/v methanol/diethyl ether mixture for three times, collected by centrifugation, and lyophilized. The product was stored at – 20 °C. Chemical structure was confirmed by 1 H-NMR on a Varian Mercury Plus 400 system.