Artificial cells in medicine and biotechnology.

Since the feasibility of artificial cells was first demonstrated in 1957 [Chang (1, 2)], an increasing number of approaches to their preparation and use have become available. Thus artificial cell membranes can now be formed using a variety of synthetic or biological materials to produce desired variations in their permeability, surface properties, and blood compatibility. Almost any material can be included within artificial cells. These include enzyme systems, cell extracts, biological cells, magnetic materials, isotopes, antigens, antibodies, vaccines, hormones, adsorbents, and others. Since cells are the fundamental units of living organisms, it is not surprising that artificial cells can have a number of possible applications. This is especially so since artificial cells can be "tailor-made" to have very specialized functions. A number of potential applications suggested earlier have now reached a developmental stage appropriate for clinical trial or application. These clinical applications include the use of such cells as a red blood cell substitute, in hemoperfusion, in an artificial kidney or artificial liver, as detoxifiers, in an artificial pancreas, and so on. Artificial red blood cells based on lipid-coated fluorocarbon or crosslinked hemoglobin are being investigated in a number of centers. The principle of the artificial cells is also being used in biotechnology to immobilize enzymes and cells. Developments in biotechnology have also resulted in the use of the principle underlying the artificial cell to help produce interferons and monoclonal antibodies; to create immunosorbents; to develop an artificial pancreas; and to bring enzyme technology usefully into biotechnology and biomedical applications. Artificial cells are also being used as drug delivery systems based on slow release, on magnetic target delivery, on biodegradability, on liposomes, or other approaches. The present status and recent advances will be emphasized in this paper.