RCB-4-8

RCB-4-8​​ is a biodegradable ionizable lipid nanoparticle (LNP) engineered for efficient pulmonary mRNA delivery and in vivo genome editing, as detailed in the primary research article ​​"Combinatorial design of nanoparticles for pulmonary mRNA delivery and genome editing"​​ (Li et al., Nature Biotechnology 2023）. Synthesized from a combinatorial library of 720 biodegradable lipids via a three-component reaction system, RCB-4-8 features an alkyne-containing lipid tail and tertiary amine headgroup, optimized through high-throughput screening for superior lung-targeting capabilities. Its unique molecular design incorporates hydrolyzable ester and carbonate groups, enabling rapid biodegradation (<30% lung retention at 48 h vs. >90% for conventional lipids) while maintaining high transfection efficiency. When formulated with DOTAP instead of DOPE, RCB-4-8 LNPs achieved ​​100-fold higher luciferase mRNA expression​​ in murine lungs compared to FDA-approved MC3 LNPs and mediated ​​95% GFP knockout​​ in vitro. In Ai9 reporter mice, intratracheal delivery of RCB-4-8 loaded with Cre mRNA edited ​​53% of total lung cells​​ after three doses, while codelivery with Cas9 mRNA/sgRNA yielded ​​7.2% tdTomato⁺ cells​​, rising to ​​17%​​ when combined with AAV-sgRNAs. With an optimal particle size of ​​85.7 nm​​ (PDI 0.11) and ​​>87% mRNA encapsulation​​, RCB-4-8 supports repeat dosing and represents a transformative platform for inhalable gene therapies targeting congenital lung diseases like cystic fibrosis.