I) ADSORPTION EEEEEEEE E E carrier 2) COVALENT LINKAGE a) Insoluble support b) Intermolecular linkage N'E~ ~~ c) Soluble support 0 \:)....m 3) tM TRIX (MOLECULAR) ENTRAPMENT ~~~~~;;..,J~-polymer matrix 4) ENCAPSULATION membrane FIGURE I. Classification of immobilized enzymes. Covalently linked, adsorbed, and matrix-entrapped enzymes represent stage II, research on the microenvironment. Microencapsulation represents stage III, research on the intracellular environment. Further subdivision of microencapsulated enzymes will be found in Chapter 12. 4 T. M. S. CHANG matrix entrapment. In this section, detailed discussions will center on clinical analysis, urine analysis, monitoring of environmental pollution, radioimmune assay, enzyme-linked immunosorbent assay, enzyme electrodes, and other approaches involving immobilized enzymes, antibodies, and antigens. In the final section, research workers describe and discuss the perspectives of immobilized enzymes and proteins. Here, they speculate on the future potential of possible approaches, even though these may not have been extensively studied or tested at the laboratory stage. The biomedical applications of enzymes and proteins, especially in the thera­ peutic area, is in a very early stage of development. Much remains to be explored and studied, and the area is wide open for investigators interested in original research in a new interdisciplinary area. References Chang, T. M. S., 1972, Artificial Cells, Charles C. Thomas, Publisher, Springfield, Ill. Dunlop, R. B. (ed.), 1974, Immobilized Biochemicals and Affinity ChrOTIULtography, Plenum Press, N ew York.