Lectin-mediated bioadhesion: Proteolytic stability and binding-characteristics of wheat germ agglutinin and Solanum tuberosum lectin on Caco-2, HT-29 and human colonocytes

Abstract

For the development of lectin-mediated drug delivery systems, the proteolytic stability of the non-toxic lectins from Arachis hypogea, Lens culinaris, Dolichus biflorus, Solanum tuberosum (STL) and Triticum vulgare was investigated by in vitro exposure to gastrointestine-located enzymes. No degradation products were observed within 24 h of incubation on sodium dodecyl sulfate polyacrylamide gels. Binding to human colon carcinoma cell lines was investigated by flow cytometry. The fluorescein-labelled derivatives of N-acetylglucosamine-specific wheat germ agglutinin (WGA) and STL exhibited the highest cell-associated fluorescence intensity. As determined by dilution experiments, the number of WGA-binding sites on Caco-2, HT-29 and human colonocytes exceeded those for STL by 5-, 1.7- and 1.4-fold, respectively. By a competitive flow cytometric assay using N,N′, N″-triacetylchitotriose for inhibition, WGA-affinity exceeded STL-affinity by ten-fold. The affinity of each lectin to Caco-2, HT-29 and human colonocytes was about the same, indicating that similar lectin receptors were involved. Preventing N-glycosylation of the carcinoma cells by pretreatment with 0.001% tunicamycin for 40 h resulted in 30% inhibition of WGA- and STL-binding. When WGA was covalently attached to Sepharose beads (250–350 μm), the interaction with HT-29 and Caco-2 cells showed stable and tight binding. Therefore, especially considering the comparable affinity of human colonocytes and monolayer-forming Caco-2 and HT-29 cells, this system is proposed as a model for the development of lectin-mediated particulate pharmaceutical devices.