The pH regulated phycobiliproteins loading and releasing of polyelectrolytes multilayer microcapsules

The polyelectrolytes multilayer microcapsules considered as a good matrix can meet the requirements of protein encapsulation and release. It is important to understand the factors affecting the encapsulation and release of proteins in capsules. In this study, the eight layers hollow capsules (PSS/PAH)4 and nine layers hollow capsules (PSS/PAH)4PSS are fabricated. The protein, R-Phycoerythrins (R-PEs) is employed as a probe instead of fluorescein isothiocyanate labeled proteins to investigate protein loading capacities on capsules as a function of pH, since R-PEs demonstrate an excellent stability over a broad pH range. The loading capacities of R-PEs on capsules (PSS/PAH)4 or (PSS/PAH)4PSS are demonstrated to be sensitive to pH. The R-PE encapsulated in capsules exhibit the largest load capacity around isoelectric point of the protein independent of outer most layer of polyelectrolytes. However, if the pH of buffer is far away from the isoelectric point of the protein, they are absorbed on the surface of capsules. Based on a Freundlich model, capsules take up proteins on their surface by monolayer adsorption. The release process of R-PEs from microcapsules to solution is also shown to be sensitive to pH. Proteins show a faster release process around isoelectric point. Therefore, the pH sensitive polyelectrolyte microcapsules may offer a promising delivery system for loading and releasing proteins in biological systems depending on environment.