Sorption of macromolecules to solid surfaces: Sorption of dextran to cellulose nitrate membranes in the presence of serum albumin and surface-active agents

Abstract

Dynamic measurements of osmotic pressure may be affected by sorption phenomena on the membrane. Likewise the sorption of polymeric plasma expanders to tissue after infusion may have adverse physiological effects. The sorption of C 14 carboxy-labeled dextran ( M n = 35,000) to collodion membranes was studied in several media. The membranes were cast over mercury from a Merck collodion solution under controlled conditions. Aqueous solutions were prepared containing dextran, sodium chloride, serum albumin, and three detergents having different chemical characteristics, in different combinations. Both sides of the membranes were exposed to these solutions for a selected sequence of time intervals up to 52 hours; they were uniformly washed (without scrubbing) and air-dried at 30°C. The radioactivity in each membrane, which is a measure of the amount of dextran present, was determined with a PC-1 Proportional Counter. The experiment was statistically designed in order to isolate and compensate for possible systematic errors due to differences between membranes and to variations in the counting procedure or fluctuations in the instrument, and in order to evaluate the precision of the data. The results indicate differences between membranes, despite the precautions taken in their preparation. Aqueous solutions containing only dextran show a continuous increase in sorption with a high initial rate. Addition of sodium chloride increases the amount of sorption, whereas the presence of serum albumin decreases it, whether or not sodium chloride is present. The cationic detergent markedly increases the sorption of dextran to the membrane, whereas the nonionic detergent has the reverse effect.