Biotin-SR peptide forms enzyme-responsive coacervate vesicles, suppressing tumor growth in xenograft models.

Targeted drug delivery remains a critical challenge in cancer therapy, often limited by systemic toxicity and poor tumor penetration. Current carriers struggle with stability in physiological environments and lack precise, enzyme-responsive release mechanisms within the tumor microenvironment. This study addresses these gaps by designing a minimal, sequence-defined peptide that leverages liquid-liquid phase separation to create stable, lipid-free coacervate vesicles (CVs) capable of targeted delivery and multi-modal therapeutic action, specifically exploiting elevated alkaline phosphatase (ALP) levels in tumors.

Researchers engineered a short, sequence-defined peptide, Biotin-Ser(-OPO3 2 -)-Phe-Phe-Arg (Biotin-SR), to self-assemble into lipid-free coacervate vesicles (CVs). This peptide integrates an alkaline phosphatase (ALP)-cleavable anionic phosphoester, a diphenylalanine motif for hydrophobic packing, and a cationic guanidinium group for architectural stability and nitric oxide (NO) generation. They evaluated the CVs' morphological persistence using FRAP analysis and their ability to encapsulate glucose oxidase (GOx). The therapeutic efficacy was assessed in both spheroids (in vitro 3D cell cultures) and xenograft models (in vivo tumor models), focusing on ALP-induced GOx release and the resulting synergistic cascade.

The Biotin-SR peptide successfully formed stable, lipid-free coacervate vesicles (CVs) with enhanced structural persistence, confirmed by restricted molecular exchange in FRAP analysis. These CVs demonstrated selective targeting of cancer cells via biotin-mediated recognition. In ALP-rich tumor environments, the CVs underwent ALP-induced enzymatic dephosphorylation, triggering an irreversible loss of charge complementarity and subsequent GOx release. This release initiated a synergistic therapeutic cascade: enzymatic starvation (from GOx depleting glucose), oxidative stress amplification, and NO-mediated mitochondrial dysfunction. The resulting glucose depletion, coupled with NO generation, significantly elevated reactive oxygen species (ROS), inducing mitochondrial dysfunction. This multi-pronged attack led to a notable suppression of tumor growth. > Biotin-SR coacervate vesicles effectively suppressed tumor growth in both spheroids and xenograft models by integrating enzymatic starvation, oxidative stress, and NO-mediated mitochondrial dysfunction.