F11T6 is a next-generation lipid nanoparticle (LNP) optimized for ultra-efficient neuron-targeted mRNA delivery, featuring a dual-tetrahydrofuran (THF) core and four pH-responsive acetal tails. Its unique bis-THF architecture enhances lipid bilayer stability and promotes brain-specific biodistribution, achieving 16.4% GFP+ neurons in vivo—the highest reported among CNS-targeting LNPs. Cryo-EM reveals a compact spherical structure (Ø~150 nm) with 93.2% mRNA encapsulation efficiency, while THF-acetal synergy enables rapid endosomal escape (Pearson coefficient: 0.16 vs. 0.27 for F10T5). Preclinical studies show F11T6 leverages meningeal lymphatic transport for brain accumulation, yielding 13.0% neuron-specific tdTomato expression in Ai14 mice, surpassing F10T5 (8.93%) and SM102 (0.1%). Mechanistically, the dual-THF core strengthens interactions with lipoprotein receptors on brain endothelial cells, whereas acetal tails undergo acid-triggered hydrolysis in endosomes, releasing mRNA into the cytoplasm. Despite slightly higher liver/spleen accumulation than F10T5, toxicology assessments confirm no hepatorenal toxicity (BUN/ALT/AST within normal ranges) or histopathological changes. Co-localization analyses demonstrate superior penetration into deep brain regions like the hippocampus, critical for treating neurodegenerative disorders. With a LogD of 12.3, F11T6 balances lipid solubility and biodegradability, outperforming clinical benchmarks in both efficiency (40× SM102) and neuron specificity. This platform holds transformative potential for delivering CRISPR-Cas9, siRNA, or neurotrophic factors, particularly in diseases demanding high-dose CNS transfection with minimal off-target effects.
