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Target-sensitive(TG-S) liposomes, which have the antibodies coupled on the surface of liposome and can release their entrapped contents by the binding of antibodies with the specific target cells, were prepared and employed to study the release of calcein and the selective delivery of an anticancer agent, doxorubicin(DOX). The monoclonal antibody, Y;used for the preparation of the TG-S liposome was one against major histocompatibility complex class 1 of mouse(MHC1, H-2K" type) and the target cells were EL-4 and RMA, which have the MHC1, H-2K´ type on their membrane surfacem. The release of calcein from TG-S liposome occurred when the target cells were contacted with liposomes and it was proportionally increased with the rise of binding capacity of antibody coupled on the surface of liposome to the target cells. The experimental results of drug delivery were similar to the cases of calcein release. The viability of specific target cell, EL-4 with liposomal DOX was not so different from that with the free DOX, while for the non-specific target cell, Yacl(H-2K`), the cell viability with liposomal DOX was much higher than that with free DOX. This shows the fact that the liposomal DOX can be efficiently delivered to the specific target cells, while it was not the case for the non-specific target cells. And the drug delivery was inhibited when the free antibody of Y3 was added in the contact process between EL-4 and TG-S liposomes, which means the drug delivery occurred mainly by the destabilization of TG-S liposomes. From these results, we could conclude that the selective drug delivery to specific target cell using the TG-S liposome would be feasible.
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