All-in-one peptide with sequential pH gradient sensing capabilities for the targeted delivery and deep penetration of nanomicelles against breast cancer

Antitumor nanomedicines are usually decorated with ligands to achieve multiple functions, such as targeting delivery, tissue penetration and enhanced cellular uptake. However, a single ligand with multiple functions is generally preferred for use in practice. Herein, a versatile peptide, (HE)₁₀G₅R₆GDK (HE-RK), was engineered by integrating several motifs into a single sequence, including a masking segment (HE), a flexible linker (G₅), and a tumor-penetrating head (RK) which comprised a cell-penetrating peptide (R₆) and a C-end Rule peptide (RGDK). The RK moiety in HE-RK was sequentially activated following the gradual charge reversal of HE to facilitate the accumulation of its cargos in deep tumor tissue and the cytosol of cancer cells. Moreover, in our study, polymer micelles conjugated with the HE-RK peptide (PM-HE-RK) showed superior cellular internalization at pH 6.5 compared to pH 7.4 <i>in vitro</i>, as well as extended blood circulation time and improved tumor targeting and penetration <i>in vivo</i>. Furthermore, the paclitaxel-loaded micelles (PTX/PM-HE-RK) demonstrated considerable antitumor efficacy, with an 81.48% tumor inhibition rate in the 4T1 mouse model. Overall, the construction of this all-in-one multisegment peptide presents a synergistic and complementary approach to advancing multifunctional peptide ligand design.