COLLOIDAL SYSTEMS FOR TUMOR TARGETING

The potential and limitations of targeted delivery of anticancer agent s with colloidal particulate carriers is the subject of this contribut ion, Because over the years liposomes have gained the most attention a s carrier system in the category of colloidal carrier systems, this pa per focuses on the utility of the liposomal system for tumor targeting . It is imperative that an intended therapeutic application of liposom es should be well matched with the liposome behavior in vivo. Therefor e, the in vivo fate of the first-generation liposomes and the more rec ently developed second-generation liposomes (surface-modified liposome s such as the immunoliposomes and long-circulating liposomes) is analy zed in terms of accessibility of target sites, time-, and site-control led drug release and potential target sites for rational targeted deli very are discussed. A few examples of areas in cancer chemotherapy, wi th a strong rationale for the use of liposomes, are given, It is concl uded that, although several options are available on the drawing board , issues such as tumor cell heterogeneity, access to the target site, shedding of antigens, and target site-specific release of the liposome -associated drug need to be addressed early in the development process .