Steric Protected and Illumination‐Activated Tumor Targeting Accessory for Endowing Drug‐Delivery Systems with Tumor Selectivity

Here, an ABA‐typed polymer, octadecyl‐polyethylene glycol (biotin)‐(o‐nitrobenzyl)‐octadecyl ester (CPB‐p‐C) with an o‐nitrobenzyl group inserted between polyethylene glycol (PEG) and octadecyl ester is synthesized as an illumination‐activated tumor targeting accessory for micelle‐based drug carriers. The functional accessory can form a flower‐like structure with folded PEG segments in aqueous solution to hide targeting biotin ligands in the core of the mixed micelle. Thus the specific binding between biotin and avidin can be suppressed by the steric hindrance of PEG shell. Upon illumination, the flower‐like structure of CPB‐p‐C is destroyed due to the cleavage of the o‐nitrobenzyl group and the biotin moieties are exposed on the surface of the micelle through the stretching process of PEG segments, generating ligand‐receptor‐mediated targeted delivery. By confocal laser scanning microscopy and flow cytometry, the illumination‐activated, tumor‐targeting delivery is studied. The influence of the amount of functional accessory in the mixed micelle on the targeting property is investigated and the optimal amount of CPB‐p‐C to achieve less side effects and better illumination activated tumor targeting activity is identified. The observed properties of CPB‐p‐C qualify it as a promising functional accessory to endow traditional drug‐delivery systems with tumor selectivity.