The Use of Fusion Methods for the Microinjection of Animal Cells

This chapter reviews that experiments that utilize microinjection or other means to introduce specific macromolecules into whole cells are becoming increasingly widespread. The majority of microinjection experiments have used amphibian oocytes; many fewer have been done with normal-sized mammalian cells that, because of their small size, are difficult to inject with microneedles. Three different types of methods have been used to introduce macromolecules into mammalian cells in culture: (1) uptake of macromolecules added to the medium, either unaided or facilitated by polycations or nascent calcium phosphate, (2) direct microinjection using microneedles, and (3) vesicle-mediated microinjection that, in all cases, is based on two steps. First the macromolecules are trapped within vesicles, and then the vesicles are used with recipient cells. The chapter explains mainly to questions related to vesicle-mediated and particularly erythrocyte ghost-mediated microinjection (EMM). It discusses the mechanism of membrane fusion that has been included to provide a theoretical basis for vesicle-mediated microinjection. Direct microinjection is also surveyed briefly, as it is interesting to compare the scope and applications of the vesicle-mediated and the direct methods.