Protein encapsulation within oppositely charged polyelectrolyte complexes

Abstract

In this study, it is aimed to perform enzyme immobilization with the coacervation, which is used as a physicochemical encapsulation method. By using this encapsulation technology, active agents like drugs and enzymes can be protected from several non desirable conditions of the environment such as high pH, organic solvents, and chaotic agents. In this research, one of the objectives is to form complex coacervate droplets with poly (diallyldimethylammonium chloride) (PDADMAC) which is a synthetic homopolymer, and pectin which is a carbohydrate found in the cell walls of plants. The biggest driving force in the formation of coacervation is the electrostatic interactions of the positive charges in PDADMAC with the negative charges in pectin. To learn more about protein encapsulation within complex coacervates, encapsulation of trypsin enzyme within complex coacervates comprised of a cationic polyelectrolyte, PDADMAC, and an anionic polyelectrolyte, pectin, was investigated as a function of mixing order of macromolecules and at different salt concentrations. Three different mixing orders was performed. Additionally, turbidimetric titrations of pectin – PDADMAC mixtures were done at six different salt concentrations. Formation of coacervate microdroplets was observed by light microscopy at these salt concentrations. Potentiometric titration experiments were performed for pectin to find the degree of ionization of pectin at the optimum pH of trypsin, which is 7.5. For further experiments, the most appropriate mixing order is selected, and the remaining experiments are performed with that addition sequence. Then trypsin and polyelectrolyte concentrations were changed and its effect on encapsulation was examined. After determining the most effective encapsulation method, enzyme activity was measured. Finally, it was investigated whether the secondary structure of trypsin changed with encapsulation by circular dichroism experiments.