Decoupling Physisorption from Chemisorption in Clickable Lipid Nanoparticles

Antibody conjugation is essential for targeted lipid nanoparticle (LNP) delivery, but here we show that click-chemistry produces artifacts that confound accurate measurement of covalent antibody-LNP bonding. We demonstrate that hydrophobic interactions between the most common click alkyne linker, dibenzocyclooctyne (DBCO), and the inherently hydrophobic LNP surface drive extensive nonspecific antibody physisorption, even in the absence of LNP azide groups. This physisorption yields artificially high apparent conjugation efficiencies measured by chromatographic methods. In contrast, less hydrophobic liposomes exhibit azide-dependent conjugation, highlighting a consequence of nanoparticle surface chemistry. Plasma incubation rapidly displaces physisorbed antibodies from LNPs, confirming their weak, noncovalent association, whereas covalently bound antibodies remain attached and enable effective in vivo targeting. Substituting DBCO with the less hydrophobic bicyclononyne (BCN) also reduces nonspecific associations. Our findings reveal hydrophobicity as a hidden variable in antibody-LNP conjugation and establish new standards for quantitative and reproducible measurement of targeted LNPs.