ABSTRACT
Aim To prepare sterically stabilized liposomes modified with chimeric TNT-3 monoclonal antibody (chTNT-3) and investigate their immunoreactivity and in vitro targeting. Methods An endgroup functionalized polyethylene glycol-lipid derivative (pyridylthiopropionoylamino-polyethylene glycolhydrogenated soy phosphatidylethanolamine, PDP-PEG-HSPE ) was synthesized and incorporated to sterically stabilized liposomes. After mild thiolysis of the PDP groups by dithiothreitol, liposomes were covalently linked with maleimide-derivatized chTNT-3 and formed sterically stabilized immunoliposomes.Coupling efficiency, antibody density, size distribution, immunoreactivity of chTNT-3-modified sterically stabilized liposomes (chTNT-3-SLs) and specific binding properties of the chTNT-3-SLs to fixed Raji cells were determined, separately. Results Higher initial Ab/PDP-PEG-HSPE molar ratios resulted in higher antibody density on the surface of liposomes but lower coupling efficiency. The optimal coupling efficiency of 71% was obtained while antibody density in liposome was 106 μg antibody/μmol phospholipids (as initial antibody/PDP-PEG-HSPE = 1: 10). The chTNT-3-SLs had a narrow size distribution after extrusion and the mean size of this immunoliposomes was (115 ± 33) nm. The immunoreactivity of chTNT-3 can be preserved after efficient attachment of maleimide-derivatized chTNT-3 to the surface of liposomes. But calculated per antibody concentration, the immunoreactivity of chTNT-3-SLs would obviously decrease compared to that of chTNT-3 or chTNT-3 derivatives. Significantly higher binding of chTNT-3-SLs to fixed Raji cells directed by chTNT-3 was obtained compared to other preparations in serial dilutions (P＜0.01). Conclusion chTNT-3-SLs prepared by PDP-PEG-HSPE method remained most immunoreactivity of chTNT-3 and was able to bind nuclear antigens in vitro.