Biotinylated and streptavidinylated liposomes as labels in cytokine immunoassays

In this study parameters are evaluated in order to improve the recently developed liposome immunosorbent assays (LISA) for the cytokines interferon-γ (IFN-γ) and interleukin-2 (IL-2). The first parameter, leakage of the liposomes, is found to be largely influenced by the concentration of the biotinylated lipid and the binding of the liposomes to the microtitre plate. However, due to the short time this leakage can occur, these liposomes are still very useful in a liposome immunoassay. A second parameter studied is the number of steps involved in the assay. As with each step the efficiency of the assay decreases, the number should be as small as possible. One step has been eliminated by developing streptavidinylated liposomes. The IL-2 LISA with these liposomes has a lower detection limit when compared with both the ELISA and LISA with biotinylated liposomes, although the linear dynamic range is much smaller.