Surface Functionalization of PLGA Particles

The core particles were prime-coated with pD by incubating 0.5 mg particles in 1 mL of dopamine hydrochloride solution in Tris buffer (10 mM, pH 8.5) for 3h at room temperature with rotation. Dopamine concentration was fixed at 0.5 mg/mL unless specified otherwise. The pD-coated PLGA particles (NP-pD or MP-pD) were collected by centrifugation (NP-pD: 8,161 ×g for 20 min; MP-pD: 1,306 ×g for 10 min) at 4°C. For surface functionalization, NP-pD or MP-pD were resuspended in Tris buffer (10 mM, pH 8.5), which contained different ligands (Folate, mPEG-NH₂, Fol-PEG-NH₂, cRADyK, cRGDyK, or pCB). The final concentrations of particles and ligands were 1 mg/mL and 2 mg/mL, respectively. After 30 min incubation at room temperature with rotation, particles were collected by centrifugation and washed with deionized water once. The functionalized NPs or MPs were named as NP-pD-Fol, NP-pD-PEG, NP-pD-PEG-Fol, NP-pD-RAD, NP-pD-RGD, MP-pD-pCB, and MP-pD-PEG according to the ligand used for the functionalization.