To study the brain‐targeted delivery efficiency of protein nanogels, we evaluated the enrichment rate in the brains of PD mice with Cy5‐labeled IL‐3 and Cy5‐labeled RVG‐IL3 NGs at different time points (10 min, 1 h, 3 h, 6 h, 9 h, 12 h, and 24 h), post‐administration, via the In Vivo Imaging System (IVIS) imaging. The gene discussed is IL3; the disease is Parkinson disease.