Comprehensive analysis of the tumor targeting efficiency of functionalized nanoparticles in an immunocompetent environment

The success of nanoparticle-based cancer therapeutics relies on their efficient tumor uptake and retention. Given this, improving nanoparticle localization in tumors is paramount to maximize their therapeutic potential. A common approach to achieve this is to functionalize nanoparticles with active targeting moieties that bind to specific tumor-associated receptors. Among these, arginine-glycine-aspartic acid (RGD) peptides have shown a potential to promote tumor accumulation by targeting the α_νβ₃ integrin receptor, a receptor commonly overexpressed by tumors owing to its role in promoting angiogenesis, metastasis and proliferation. Yet, its efficacy is commonly assessed using immunocompromised mice models. While useful, these models do not accurately account for immune-related interactions, which could lead to an overestimation of targeting efficacy. In our study, we investigated the efficacy of RGD peptides to improve the tumor accumulation of PEGylated gold nanoparticles (GNPs) using an immunocompetent mouse model. While RGD functionalization increased GNP uptake in cancer cells in vitro, it significantly reduced tumor accumulation in vivo due to enhanced off-target clearance by the mononuclear phagocyte system, with elevated accumulation in the spleen and liver. These findings highlight that RGD functionalization can promote immune-driven clearance in vivo, despite improving GNP uptake in cancer cells in vitro, emphasizing the importance of assessing targeting strategies in immunocompetent models for more physiologically relevant assessments.