H2O2 is necessary for nanoparticles proangiogenesis activity. A. Primary cell culture with 1 µg/ml nanoparticles and 1000 units/ml catalase. i) Blank control, ii) 1000 units/ml catalase, iii) 20 ng/ml VEGF, iv) 20 ng/ml VEGF and 1000 units/ml catalase, v) 1 µg/ml Eu Rods, vi) 1 µg/ml Eu Rods and 1000 units/ml catalase. B. Quantitative analysis shows that catalase can abolish proangiogenesis activity induced by nanoparticles, but not by VEGF.