Specific binding of lentivirus to PS-PLG microspheres LV-GFP (A-D) and rAd-GFP (E-H) were incubated with PLG (B, F), PC-PLG (C, G), or PS-PLG (D, H) microspheres for 30 min and centrifuged to remove the unbound viruses. After wash with PBS, the microspheres were mixed with 293 cells and seeded on the plate. GFP expression was visualized at 2 days after seeding. Viruses without mixing with microspheres were used as control (A, E). Bar represents 100 μm.