Evaluation of hypotonic preswelling method for encapsulation of enalaprilat in intact human erythrocytes

The hypotonic preswelling method for encapsulation of drugs in intact human erythrocytes tr,as evaluated using enalaprilat as a model peptidelike drug. Several process variables, including volume, concentration, pH, and method of addition of drug solution, type of erythrocyte-suspending medium, temperature, initial packed density of erythrocytes, and individual process steps, were exploited with respect to their effects on the loading parameters (i.e., loaded amount efficiency of entrapment, and cell recovery). In addition, the probable mechanism by which the erythrocytes were loaded by enalaprilat at the point of lysis was shown to be a simple concentration gradient-based diffusion through membrane openings occurring on hemolysis. Finally, the adopted method was validated and the results showed a considerable degree of reproducibility and recovery; for the entire loading procedure.