Encapsulation of Enzymes, Cell Contents, Cells, Vaccines, Antigens, Antiserum, Cofactors, Hormones, and Proteins

Abstract

Unlike the other three major methods of enzyme immobilization, which emphasize the “microenvironment,” encapsulation of enzymes emphasizes the “intracellular environment” of enzymes and proteins (Figure 1). Here, the enzyme solution or suspension is encapsulated or enveloped within a membrane system in such a way that the membrane creates an intracellular environment for the enzymes, preventing them from leaking out or coming into direct contact with the external environment. Large molecules such as proteins and cells cannot cross the membrane to interact with the enclosed enzymes. Substrates that are permeable can equilibrate rapidly across the membrane to be acted on by the enzymes inside, and the product can diffuse out. Unlike the case of gel entrapment, which involves the entrapping of individual molecules of enzymes in polymer lattices, in encapsulation, any concentration, any volume, and any amount of enzymes can be enclosed within membrane envelopes of different configurations. This principle of allowing any type or concentration of enzymes, cells, or cell extracts to be encapsulated within membrane envelopes allows for an extremely large variation in the membrane composition, configuration, and content. This chapter is a brief review of the general principles and methods of preparation for encapsulation of enzymes and proteins, with emphasis on artificial cells. Only a brief review is made of other forms of encapsulation since they will be dealt with in detail in later chapters.