Fig. 1.

Anti-PDGF DARPin strongly binds PDGF-BB and inhibits PDGF-BB-induced proliferation of NIH3T3 cells. a Triplicate samples consisting of 2 pM up to 8 nM of purified anti-PDGF DARPin were incubated overnight at 4 °C with 40 pM hPDGF-BB and then free PDGF-BB was assayed by ELISA. b Triplicate wells of starved NIH3T3 cells were incubated with a constant amount of hPDGF-BB (20 or 10 ng/mL) and a serial dilution of PDGF DARPin ranging from 200 to 0.05 nM. Control wells were incubated with hPDGF-BB alone. Cells were incubated for 48 h at 37 °C/5 % CO₂, developed by addition of WST-1, and after 1–4 h absorbance was measured at OD450-620 nm. IC₅₀ values were determined using the Graph Pad Prism fitting program and a non-linear fitting algorithim [log(inhibitor) vs. response with variable slope]