Characterization of physiochemical and biological properties of spherical protein crystals for sustained release

This study presents an exploration on extending the action of therapeutic proteins by crystallization strategy without new molecular entities generation. Recombinant human interferon α-2b (rhIFN), a model protein drug in this case, was crystallized using a hanging drop vapor diffusion method. A novel chelating technique with metal ions was employed to promote crystals formation. The physico-chemical characterization of the protein crystals, including morphology, particle size, X-ray diffraction, circular dichroism and biological potency evaluations were performed. In addition, the in vitro release behavior of rhIFN from crystal lattice suggested an exciting possibility of protein crystals as a long-acting formulation. The work described here demonstrates the possibility of spherical crystals of biomacromolecules for controllable delivery application of therapeutic proteins.