The cytotoxic effect of Eucheuma serra agglutinin (ESA) on cancer cells and its application to molecular probe for drug delivery system using lipid vesicles.

Eucheuma serra agglutinin (ESA) derived from a marine red alga, Eucheuma serra, is a lectin that specifically binds to mannose-rich carbohydrate chains. ESA is a monomeric molecule, with a molecular weight of29,000. ESA induced cell death against several cancer cell lines, such as colon cancer Colo201 cells and cervix cancer HeLa cells. DNA ladder detection and the induction of caspase-3 activity suggested that the cell death induced by ESA against cancer cells was apoptosis. ESA bound to the cell surface of Colo201 cells in the sugar chain dependent manner. This means that the binding of ESA to the cell surface is specific for mannose-rich sugar chains recognized by ESA. The binding of ESA to the cell surface of Colo201 cells was slightly suppressed by the high concentrations of serum because of the competition with serum components possessing the mannose-rich sugar chain motifs. On the other hand, a lipid vesicle is a very useful microcapsule constructed by multilamellar structure,and adopted as drug or gene carrier. ESA was immobilized on the surface of the lipid vesicles to apply the lipid vesicles to cancer specific drug delivery system. ESA-immobilized lipid vesicles were effectively bound to cancer cell lines compared with plane vesicles.