pH-responsive polymers for trehalose loading and desiccation protection of human red blood cells.

PP-50, a synthetic pH-responsive biopolymer, is here shown to increase the permeability of the phospholipid bilayer to trehalose, a disaccharide accumulated in desiccation tolerant organisms across all kingdoms. Uptake of 251 ± 6 mm intracellular trehalose facilitated an increase in the membrane integrity of vacuum dried cells by a factor of 9 ± 1 and reduced extent of hemoglobin oxidation in dried cells from 66 ± 1% to 23 ± 3%. To elucidate the mechanism of PP-50 mediated trehalose delivery, permeability studies were conducted using molecules ranging in size from sucrose to 10 kDa poly(ethylene glycol). It was shown that the logarithm of relative diffusant membrane permeability decreased linearly with diffusant molecular volume, suggesting transport via non-Stokesian diffusion. Consistent with this conclusion, topographic atomic force micrographs reported membrane thinning proximate to PP-50 adsorption on the erythrocyte membrane, a phenomenon associated with increased incidence of phospholipid hydrocarbon chain bending.