Amphiphilic polymers have been designed and self-assembled into vesicles,which exhibit diverse potential applications in catalysis,biomacromolecules and drug delivery,water remediation,bacterial inhibition and theranostics,etc.1-8 We recently prepared an antibacterial polypeptide-grafted chitosan-based vesicle as an “armed” carrier of anticancer and antiepileptic drugs,showing low cytotoxicity to normal human L02 cells but excellent antibacterial efficacy.8 Very recently,to significantly improve the sensitivity of a T1 MRI contrast agent and to enhance the efficacy of cancer chemotherapy,we synthesized a noncytotoxic asymmetrical cancer targeting polymer vesicle based on R-poly(L-glutamic acid)-block-poly(caprolactone)(Figure 1).4 These vesicles have a cancer-targeting outer corona and a Gd(Ⅲ)-chelating and drug-loading-enhancing inner corona,exhibiting an extremely high T1 relaxivity(42.39 mM-1s-1,8-fold better than DTPA-Gd)and anticancer drug loading efficiency(52.6%for doxorubicin hydrochloride,DOX·HCl).Moreover,the DOX-loaded vesicles exhibited excellent antitumor activity(two-fold better than free DOX).This “chelating-just-inside” strategy for synthesizing asymmetrical polymer vesicles demonstrated promising potential theranostic applications in magnetic resonance imaging and cancer-targeted drug delivery.