Microenvironment‐Adaptive, Size‐Transformable Self‐Assembling Peptide Nanoassemblies for Targeted Delivery and Synergistic Combat Biofilm and Deep Tissue Associated Infections

ABSTRACT Bacterial biofilms and deep‐seated infections pose major therapeutic challenges by impairing antibiotic efficacy and accelerating antimicrobial resistance. Peptide‐based nanomaterials offer unique advantages, including low resistance induction and high biocompatibility, yet their clinical translation is limited by poor infection‐site targeting, short circulation, and restricted penetration into pathological barriers. Here, we present microenvironment‐adaptive self‐assembling peptide nanoassemblies (CyPN12) designed to overcome these limitations. CyPN12 forms large‐sized nanoparticles under physiological conditions, functioning as both intrinsic antibacterial agents and stable carriers. Upon encountering infectious microenvironments, they actively target pathogenic bacteria and transform into nanofibers, achieving prolonged retention and sustained antibacterial activity. In gelatinase‐rich associated with biofilms and deep tissue infections, CyPN12 undergo a secondary transformation into small‐sized nanoparticles, enabling efficient penetration through dense tissue and biofilm matrices. This dynamic size‐ and structure‐transformable behavior promotes targeted delivery, controlled release, and synergistic bactericidal efficacy while reducing the likelihood of resistance through membrane‐disruptive mechanisms. In murine and porcine models, ciprofloxacin‐loaded CyPN12 (Cip@CyPN12) selectively accumulated at infection sites and exhibited potent therapeutic efficacy against both localized and systemic infections. Collectively, this work offers a size‐transformable peptide system that improves biofilm penetration and antimicrobial efficacy, providing a feasible approach for the treatment of biofilm‐associated and deep‐seated infections in animal husbandry, thereby contributing to improved animal health.