IL13 and neoplasm: Other promising ligands include Aptamer AS1411, a stable DNA aptamer that binds nucleolin, a protein overexpressed on GBM cell surfaces, enabling high-specificity nanoparticle functionalization (Bie et al. 2022); and interleukin-13 (IL-13), a cytokine that selectively targets interleukin-13 receptor alpha-2 (IL-13Rα2), a tumor-restricted antigen abundant in GBM but minimal in normal brain tissue (Gao et al. 2014).