A Novel Strategy through Combining iRGD Peptide with Tumor-Microenvironment-Responsive and Multistage Nanoparticles for Deep Tumor Penetration

Despite the great achievements that nanomedicines have obtained so far, deep penetration of nanomedicines into tumors is still a major challenge in tumor treatment. The enhanced permeability and retention (EPR) effect was the main theoretical foundation for using nanomedicines to treat solid tumor. However, the antitumor efficiency is modest because the tumor is heterogeneous, with dense collagen matrix, abnormal tumor vasculature, and lymphatic system. Nanomedicines could only passively accumulate near leaky site of tumor vessels, and they cannot reach the deep region of tumor. To enhance further the tumor penetration efficiency, we developed a novel strategy of coadministering cell-homing penetration peptide iRGD with size-shrinkable and tumor-microenvironment-responsive multistage system (DOX-AuNPs-GNPs) to overcome these barriers. First, iRGD could specifically increase the permeability of tumor vascular and tumor tissue, leading to more DOX-AuNPs-GNPs leaking out from tumor vasculature. Second, the multistage system passively accumulated in tumor tissue and shrank from 131.1 to 46.6 nm to reach the deep region of tumor. In vitro, coadministering iRGD with DOX-AuNPs-GNPs showed higher cellular uptake and apoptosis ratio. In vivo, coadministering iRGD with DOX-AuNPs-GNPs presented higher penetration and accumulation in tumor than giving DOX-AuNPs-GNPs alone, leading to the best antitumor efficiency in 4T1 tumor-bearing mouse model.