Abstract
It is well-known that serum components destabilize liposomal membranes. Therefore, most in-vitro transfection protocols avoid serum, which make the extrapolation to in-vivo situations difficult. In this study, we investigated the stability of different anionic liposomal formulations including artificial viral envelopes (AVEs) in 100% fetal calf serum (FCS), human serum (HS) and human plasma (HP) by measuring the release of entrapped carboxyfluorescein (CF). We observed that FCS and HP induce leakage of CF from vesicles, while HS did not induce a pronounced leakage from the liposomes. In addition, we studied the effect of the phosphatidylethanolamine (PE) moiety, negatively charged lipid components and cholesterol (CHOL) on the stability of AVE liposomes. We found that the liposomes composed of DMPE/DPPG/CHOL (1:2:1) were the most stable liposomes in FCS and HP, among the examined liposomal formulations. Liposomes having a lipid composition similar to viral envelopes (AVE) were more stable in serum than pH-sensitive liposomes also used in gene therapy.