Cationic Nanostructured Lipid Carrier for Paclitaxel and PD-L1 siRNA Co-delivery to Improve Breast Cancer Therapy

Introduction: Breast cancer remains a leading cause of mortality, with tumor immune evasion via the PD-1/PD-L1 axis limiting chemotherapy efficacy. To overcome this, we developed a cationic Nanostructured Lipid Carrier (NLC) system for the co-delivery of Paclitaxel (PTX) and PDL1- targeting siRNA. Methods: The P-NLC formulation was optimized using a Box-Behnken design and characterized via DLS, TEM, DSC, FTIR, and XRD. PD-L1 siRNA was complexed onto the cationic surface via electrostatic interactions, confirmed by gel retardation assays. Cellular uptake and cytotoxicity were evaluated in MCF-7 cells and a 3D spheroid model. Results: Complete siRNA binding was confirmed at a 100:1 mass ratio. The P-NLC-siRNA system exhibited sustained PTX release and enhanced cellular uptake in MCF-7 cells. In vitro assays demonstrated that the co-delivery system significantly suppressed cell viability compared to free PTX or PNLC alone, while the 3D model revealed improved apoptosis and tumor penetration. Discussion: These findings highlight the formulation's physicochemical stability and ability to enhance cytotoxicity. Although direct gene-silencing efficiency was not explicitly quantified in this study, the platform’s previously established in vivo PD-L1 knockdown capability supports the observed therapeutic potential. Conclusion: The developed cationic NLC enabled efficient co-loading of PTX and siRNA, demonstrating significant potential as a combined chemo-RNAi therapeutic strategy for improved breast cancer treatment.