Lectin-functionalized liposomes for pulmonary drug delivery: interaction with human alveolar epithelial cells

In this study the interaction of lectin-functionalized liposomes with two different alveolar epithelial cell culture models was evaluated. Plant lectins were coupled to liposomes exploiting the avidin/biotin technology. In contrast to lectin-free liposomes, lectin functionalized liposomes specifically bound to A549 cells, a tumor-derived cell line. Using this cell line, temperature-dependent binding assays as well as confocal laser scanning microscopy (CLSM) revealed that the lectin liposomes were only bound but not taken up by these cells. In contrast to these findings, confocal images of human alveolar epithelial cells in primary culture incubated together with lectin liposomes indicated binding as well as cellular uptake. Fluorescein-isothiocyanate (FITC)-labeled dextrans (Mw 40,000 Da), encapsulated in lectin-functionalized liposomes and incubated with monolayers of primary cultured human alveolar epithelial cells appeared to be localized intracellularly by CLSM. This suggests that lectin-mediated bioadhesion and uptake of liposomal carriers may provide a useful technology for improved delivery of hydrophilic macromolecules to the alveolar epithelium.