Cl-4A3-LNSC8 represents a novel class of thiourea-functionalized ionizable lipids engineered for selective organ-targeted mRNA delivery. Its core innovation lies in an anion-coordination strategy, where the parent lipid, 4A3-LNSC8, binds chloride ions (Cl⁻) via hydrogen-bonding interactions with its thiourea groups. This binding event is not merely structural but functionally critical, as it induces a significant shift in the surface pKa of the resulting lipid nanoparticles (LNPs) from approximately 5.54 to 8.79. This pKa modulation is the key mechanism that redirects the organotropism of the LNPs upon systemic administration. While the unmodified 4A3-LNSC8 LNPs preferentially deliver mRNA to the liver, Cl-4A3-LNSC8 LNPs effectivelyreprogram this tropism, enabling highly efficient mRNA delivery to secondary lymphoid organs (SLOs), particularly the spleen and lymph nodes. This platform demonstrates remarkable efficacy, achieving up to 65.7% gene editing efficiency in splenic macrophages in vivo, significantly outperforming benchmark delivery systems. Furthermore, by leveraging the coordination with different halides, such as iodine for computed tomography (CT) contrast, the system can be adapted for dual-modal theranostic applications, enabling simultaneous lymphatic metastasis imaging and therapeutic mRNA delivery.
