Spacer engineering in nanoparticle-peptide conjugates boosts targeting specificity for tumor-associated antigens.

Developing and synthesizing nano-objects capable of enabling early targeted diagnosis and ensuring effective tumor treatment represents a significant challenge in the theranostic field. Among various nanoparticles (NPs), iron oxide nanoparticles (IONPs) have made significant contributions to advancing this field. However, a key challenge lies in achieving selective recognition of specific cell types. In oncology, the primary goal is to develop innovative strategies to enhance NP uptake by tumors, primarily through active targeting. This involves adding targeting ligands (TL) to the NP surface to facilitate tumor accumulation and increase retention within the tumor microenvironment. Despite biofunctionalization strategies, overall tumor uptake remains modest at only 5-7% of the injected dose per gram. In this work, we demonstrate the effect of spacing between the NPs and the TL to improve their availability and thus the tumor uptake of the complex. This proof-of-concept study targets the epidermal growth factor receptor (EGFR) using a peptide as a targeting ligand. Specifically, we characterized the PEG-peptide coupled to dendronized IONPs, including the density of grafted TL. These nano-objects underwent in vitro evaluation to assess their ability to specifically target and be internalized by tumor cells. Therapeutically, compared to non-functionalized NPs, the presence of the TL with a PEG linker enhanced targeting efficacy and increased internalization, leading to improved photothermal efficacy.