Branched pei bpei

Tetramethylrhodamine (TRITC; 1 mg; Sigma Aldrich, St. Louis, MO, USA) dissolved in 3 mL dimethyl sulfoxide (DMSO) was mixed with 500 mg branched PEI (bPEI; 25,000 Da; Sigma Aldrich, St. Louis, MO, USA) dissolved in 10 mL distilled water for 12 h at room temperature. The solution was then dialyzed (molecular weight cut-off (MWCO), 1000 Da) for 2 days in the dark; and TRITC-conjugated bPEI (PEI) were synthesized. TRITC/DEX-conjugated bPEI (DEX/PEI) was synthesized via a conventional carbodiimide reaction. The bPEI (250 mg, 10 μmol) was stirred in 10 mL DMSO until completely dissolved. Then, a mixture of DEX (25 mg, 50.76 μmol; Steraloids, Newport, RI, USA), dicyclohexylcarbodiimide (DCC; 16 mg, 77.55 μmol), and n-hydroxysuccinimide (NHS; 16 mg, 139.02 μmol) prepared in 5 mL DMSO was added to the bPEI solution and incubated for 24 h at room temperature. Subsequently, 1 mg TRITC dissolved in 3 mL DMSO was added dropwise to this solution over 12 h. The final solution was dialyzed (MWCO, 1000 Da) against distilled water for 3 days. The final products were obtained by lyophilization.