2.5. LBA-PDA-PEG-DSF-Cy3 synthesis

PDA-PEG-DSF was modified by Cy3 for cellular uptake study. Briefly, cysteamine (0.84 mg, 30% PDA function group) in 500 μL DMSO was added dropwise into 20 mg PDA-PEG in 500 μL DSMO and the reaction mixture was left at room temperature overnight. After overnight reaction, Cy3 NHS ester (0.142 mg in 20 μL DMSO, 5% PDA function group) was added and the mixture was left for reaction for 2 h at room temperature. For LBA conjugation, LBA (4.33 mg in 100 μL DMSO) was activated by EDC (4.64 mg in 100 μL DMSO) and NHS (2.79 mg 100 μL DMSO) for 30 min and added to the polymer solution and reacted overnight. Both PDA-PEG-Cy3 and LBA-PDA-PEG-Cy3 then reacted with DDTC to get Cy3 labeled polymers (PDA-PEG-Cy3-DSF and LBA-PDA-PEG-Cy3-DSF). The reaction mixture was finally followed with a thorough dialysis towards DMSO to remove free Cy3 and DDTC. The concentration of Cy3 in the final product was measured by microplate reader (Ex=485 nm, Em= 595nm, Beckman Coulter DTX 880 Multimode Detector, Beckman Coulter, Inc).