Poly-ε-caprolactone (PCL) nanoparticles in breast cancer therapy: bridging bench research and clinical potential.

Breast cancer continues to challenge global health, with rising incidence and limited success from conventional treatments such as chemotherapy, surgery, and radiotherapy. These approaches often lack precision, leading to systemic toxicity, resistance, and relapse. Nanotechnology offers a transformative path by creating drug delivery systems that concentrate therapeutics at the tumor site while protecting healthy tissue. Among polymeric carriers, poly-ε-caprolactone (PCL) has emerged as a leading material due to its biodegradability, biocompatibility, and tuneable release profile. This review examines recent progress in PCL-based nanoparticles (NPs) for breast cancer therapy, highlighting their structural versatility and diverse applications. We discuss innovations in single and multi-drug delivery platforms, integration of natural bioactives, and co-delivery systems that combine chemotherapeutics with genetic material for synergistic effects. Active and passive targeting strategies are explored, with special focus on ligand-functionalized systems that exploit tumor-specific receptors. Emerging designs incorporate stimuli-responsive release and multifunctional properties, enabling both therapeutic and diagnostic capabilities. Preclinical studies show that PCL NPs can enhance the solubility of poorly water-soluble drugs, prolong systemic circulation, and improve the therapeutic index while reducing off-target toxicity. By bridging laboratory discoveries with translational research, PCL-based nanocarriers represent a promising preclinical strategy for personalized breast cancer management and warrant further in vivo and clinical investigation.