Optimizing Pluronic–PEI Nanocarriers for RNAi Delivery in Oral Cancer: From Polymer Synthesis to Functional Screening

Oral squamous cell carcinoma (OSCC) treatment is hindered by the poor delivery of RNA interference (RNAi) therapeutics such as microRNAs (miRNAs). Here, we systematically explored the synthesis and functional optimization of Pluronic-polyethylenimine (PEI) nanocarriers for efficient miRNA delivery in OSCC. Among several Pluronic variants tested, only Pluronic L121 formed stable, fully cross-linked micellar nanogels via covalent bonding with low-molecular-weight PEI (1.8 kDa), enabling robust miRNA-100 complexation at an N/P ratio of 5:1. These cross-linked nanogels (PP03) outperform counterparts derived from other Pluronics or PEI alone, demonstrating enhanced cellular uptake and potent miRNA-mediated silencing in both 2D and 3D OSCC models. PP03 exploits a pH-sensitive ester linkage that facilitates endosomal escape through PEI's proton sponge effect combined with Pluronic-mediated osmotic modulation. The nanogels' rough 3D morphology confers superior colloidal stability and mucoadhesion, supporting oromucosal delivery. Furthermore, PP03 displayed hemocompatibility with no hemolytic or hemorrhagic events observed, highlighting its versatility for intravenous administration. This work emphasized the significance of polymer chemistry and cross-linking efficiency in designing functional RNAi nanocarriers, thereby advancing miRNA-based therapeutics for oral cancer.