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. In this methodology, antibodies are simply attached to the PEG terminus of liposomes, which had been endgroup-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.