Orientation selective immobilization of human erythrocyte membranes on ultrathin cellulose films
We report the orientation selective immobilization of human erythrocyte membranes on planar solid supports. The orientation of the immobilized membrane was identified with selective fluorescence labels. When the right-side-out (RSO) ghosts were incubated with planar glass cover slides, no adsorption or rupture of erythrocytes could be observed. To increase the interfacial attraction between cells and the surface, two types of hydrated polymer films were deposited on the glass cover slides; (a) physisorbed films of cationic polylysine, and (b) Langmuir–Blodgett (LB) films of cellulose derivatives. On polylysine films, patches of the ruptured membranes could be observed, but the surface coverage still remained poor. On the other hand, RSO ghosts were likely to coat the surface of cellulose films more continuously. The fluorescence labeling demonstrated that immobilized erythrocyte membranes selectively inverted their native orientation. Tentatively, we interpreted this larger surface coverage on the cellulose film in terms of the “wetting affinity” between the cell surface glycocalix and the polysaccharides. Such ultrathin (thickness 5–10 nm), biological polysaccharide films have a large potential to immobilize native cell membranes without denaturing their structure, membrane orientation, and functions.