COMPARISON OF POLYMERICALLY STABILIZED PEG-GRAFTED LIPOSOMES AND PHYSICALLY ADSORBED CARBOXYMETHYLCHITIN AND CARBOXYMETHYL GLYCOLCHITIN LIPOSOMES FOR BIOLOGICAL APPLICATIONS/

The stabilities of two types of polymerically stabilized liposomes con sisting of PEG-grafted (DSPC:CHOL: DSPE-PEG1900, 5:4:1) and physically adsorbed carboxymethylchitin (CMC) and carboxymethyl/glycolchitin (CO ) are compared. The polyelectrolyte is adsorbed on positive (DSPC:CHOL :DMTAP, 5:4:1) and neutral (DSPC:CHOL, 1:1) liposomes at different mol ecular weights (M-w). In PBS buffer(4 = 154 mM, pH = 7.4) the theoreti cal stability ratios (W)calculated using the classical DLVO Theory, in dicate that the CMC-coated vesicles and the negative liposomes (DSPC:C HOL:DMPG, 5:4:1) are highly stable (W much greater than 1) compared to the PEG-grafted (W = 0.9511) and CO-coated (W = 0.9550) liposomes. Me anwhile, experimentally determined values of I W, prove that the PEG-g rafted is the most stable suspension (W = 5.5). Computation of the the oretical values of W for liposome-red blood cell and liposome-macropha ge indicates that the electrosterically stabilized suspensions and the negative liposomes are stable. Light scattering results show that the flocculation of liposomes in blood and plasma depends on polymer mole cular weight, type of polyelectrolyte and surface charge of the uncoat ed liposome. Neutral liposomes coated with CMC of M-w = 1.01 x 10(5) a nd negative liposomes provide a more effective barrier to plasma macro molecular protein adsorption than the grafted PEG groups and are easy to resuspend in blood. (C) 1998 Elsevier Science Ltd. All rights reser ved.