Polymer Molecular Weight Influences Cancer Cell Surface Retention and Cytokine Presentation by Layer-by-Layer Nanoparticles

Engineering the surface chemistry of nanoparticles (NPs) via the electrostatic layer-by-layer (LbL) assembly approach is a viable strategy for developing targeted drug delivery vehicles. However, how assembly solution conditions and polymer molecular weight (MW) govern LbL-NP properties remains poorly understood. We investigated the influence of layering buffer ionic strength and polymer MW on the functional performance of PLR/PLE bilayer-coated LbL-NPs designed to promote cancer cell targeting and NP retention on the extracellular membrane to deliver the cytokine interleukin-12 (IL-12). Assembly under mild ionic strength conditions increased LbL film stability but reduced IL-12 bioavailability and lipid exchange at the NP surface, ultimately diminishing therapeutic efficacy. In contrast, highly stable LbL-NPs assembled using high-MW (HMW) polymers under low ionic strength conditions exhibited enhanced in vitro NP association, increased cancer cell surface retention, and improved tumor accumulation in vivo in a metastatic ovarian cancer model, leading to improved efficacy and long-term survival. Molecular dynamics (MD) simulations revealed that HMW polymer layering produced denser PLE outer layer architecture compared to more highly interpenetrated LMW layers, providing structural insight into the superior performance of HMW LbL-NPs. These results demonstrate that control over LbL-NP delivery performance is influenced by polymer MW and assembly conditions, with HMW polymers augmenting the performance of PLR/PLE-coated NPs for IL-12 delivery.