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

In this study the interaction of lectin-functionalized liposomes with two d ifferent alveolar epithelial cell culture models was evaluated. Plant lecti ns were coupled to liposomes exploiting the avidin/biotin technology. In co ntrast to lectin-free liposomes, lectin functionalized liposomes specifical ly bound to A549 cells, a tumor-derived cell line. Using this cell line, te mperature-dependent binding assays as well as confocal laser scanning micro scopy (CLSM) revealed that the lectin liposomes were only bound but not tak en up by these cells. In contrast to these findings, confocal images of hum an alveolar epithelial cells in primary culture incubated together with lec tin liposomes indicated binding as well as cellular uptake. Fluorescein-iso thiocyanate (FITC)-labeted dextrans (Mw 40000 Da), encapsulated in lectin-f unctionalized liposomes and incubated with monolayers of primary cultured h uman alveolar epithelial cells appeared to be localized intracellularly by CLSM. This suggests that lectin-mediated bioadhesion and uptake of liposoma l carriers may provide a useful technology for improved delivery of hydroph ilic macromolecules to the alveolar epithelium.