In order to develop a rapid and straightforward coupling procedure at the PEG terminus, a method of direct coupling antibodies to the PEG terminus of liposomes was introduced by Bendas et al. [1]. In this methodology, antibodies are simply attached to the PEG terminus of liposomes, which had been end-group functionalized with cyanuric chloride, in mild basic conditions (pH 8.8) without prior antibody derivatizations. It has been shown that in order to obtain a stable attachment of proteins on liposome, the DSPE-PEG-cyanur was added into the liposomes to chemically conjugate with proteins to form a stable complex and minimize the denaturation of proteins.

Proteins can be covalently coupled to the liposomes via amine-reactive cyanur-groups, either directly to the vesicle surface using cyanuric chloride-activated DSPE (cyanur-DSPE) or to the distal ends of PEG-spacers using activated cyanur-PEG-PE (ammonium salt). Cyanuric chloride at the PEG terminus functions to link peptides, antibodies and other amine-containing biomolecules or nanoparticles via a nucleophilic substitution reaction under basic conditions. Antibodies or other proteins can be conjugated without any previous derivatization.

Immunosome®-Cyanur is a PEGylated product. For other amine reactive (PEGylated and non-PEGyalated products) and also Immunosome® products suitable for other types conjugation methods see here.