Cell membrane fusion induced by surface modification with cell-penetrating peptide–lipid conjugates that facilitates close contact between distinct membranes

Abstract

Cell fusion has several biotechnological applications. We previously reported cell surface modification with interactive ligands to induce cell–cell attachment, resulting in higher cell fusion efficiency when combined with a polyethylene glycol (PEG)-induced method. However, spontaneous cell fusion never occurred, even though cell–cell contact was strongly induced by ligand modification. The interactive ligands placed between the two membranes might obstruct spontaneous cell fusion during lipid exchange between the two cellular membranes. We hypothesized that two distinct cell membranes must be brought together to realize efficient membrane fusion by temporal ligand modification. Here, we aimed to induce spontaneous membrane fusion with single-polymer conjugates using liposomes and cells. We synthesized poly(ethylene glycol)-lipids (PEG-lipids) carrying the Tat peptide (Tat-PEG-lipid), a representative cell-penetrating peptide, and used it for cell–cell anchoring. We found that Tat-PEG-lipid interacted with the bilayer membrane via the Tat peptide and lipid domain and induced membrane fusion when the lipid was nonanoyl (C9) or dodecanoyl (C12) and the PEG chain was 5 kDa, as assessed by quartz crystal microbalance with dissipation monitoring, dynamic light scattering, and fluorescence resonance energy transfer measurements, transmission electron microscopy, and confocal microscopy. It was found that Tat-PEG-lipid could induce membrane attachment and fusion of cells as well as liposomes, but it did not remain stable on the membrane. Thus, membrane fusion could be effectively promoted by the attachment of lipid membranes induced by transient surface modification with a Tat-PEG-lipid containing a nonanoyl or dodecanoyl lipid chain and a 5 kDa PEG chain.