Heterobifunctional folate-PEG-amine (Folate-PEG-NH2, Folic acid-PEG-NH2) can bind to folate receptors on the surface of broad-spectrum cancer tissues. Folic acid or vitamin B9 can selectively bind to folate receptors, while primary amines can react with various functional groups, such as succinimidyl ester (NHS), carboxylic acid (COOH), acid anhydride, etc.