Interaction of liposomal and polycationic transfection complexes with pulmonary surfactant

Background The delivery of genes to the airways holds promise for the treat ment of lung diseases such as cystic fibrosis and asthma. Current nonviral gene delivery systems lack sufficient transfection efficiency. Pulmonary su rfactant has been reported to be a barrier to gene transfer into the airway s. Here we analyze the interaction of liposomal and polycationic transfecti on complexes with pulmonary surfactant. Methods The efficiency of non-viral transfection of cultured human airway e pithelial cells (16HBE14o-), COS7 cells and porcine primary airway epitheli al cells was studied in the presence of various surfactant preparations in order to model the conditions prevailing in the airways during transfection . Results The natural pulmonary surfactant, Alveofact, an extract from bovine lung lavage, was found to inhibit lipofection with lipofectAMINE for all c ell lines investigated. Dendrimer meditated polyfection was unaffected for pulmonary cell lines and was weakly affected for COS7 cells. PEI-mediated p olyfection was unaffected for all cell lines tested. The synthetic surfacta nt preparation Exosurf containing L-alpha-phosphatidylcholine-dipalmitoyl ( DPPC) as the sole lipid ingredient had no statistically significant effect on polymer- and lipid-mediated transfection. The transfection efficiencies are related to structural changes in the DNA complexes as demonstrated by D Nase-accessibility tests and fluorescence spectroscopy. In the presence of the phospholipid POPG, which is a constituent of Alveofact, DNA condensed i n lipofectAMINE lipoplexes became accessible to DNaseI, while DNA condensed with PAMAM dendrimer or PEI was less accessible to DNase I as compared to lipoplexes. Consistently, the fluorescence of a DNA-intercalating dye incre ased after addition of Alveofact only in the case of lipoplexes. Conclusions In contrast to lipofection, gene transfer with cationic polymer s to airway epithelial cells is not inhibited by pulmonary surfactant in vi tro. Depending on the surfactant concentration even an increase in polymer- mediated transfection can be seen. In conclusion, cationic polymers appear to be the more stable gene delivery systems for topical application into th e airways. Copyright (C) 1999 John Wiley & Sons, Ltd.