Formulating protein therapeutics into particulate forms.

This review is aimed at providing critical comments on selected approaches to formulating protein drugs into particulate forms feasible as practical pharmaceutical dosage forms. From a practical point of view, the need to formulate protein therapeutics into particulate forms includes inhalation and sustained-release delivery proteins, stabilizing and incorporating proteins into tissue engineering scaffolds and medical devices, as well as protecting and targeting protein therapeutics in an in vivo environment. For either of the applications, a common challenge is that proteins are easily denatured during particle-forming processes in which water-oil or water-air interfaces, multivalent ions or polyelectrolytes, strong shear stress and/or reactive crosslinking agents are often involved. Moreover, methods to protect proteins during the particle-forming processes must not compromise their pharmaceutical objectives, such as encapsulation efficiency, burst-free controlled release and storage convenience. Although numerous methods have been reported to formulate proteins into particulate systems, few of them meet the criteria above. To stimulate critical and interactive readings of the vast and booming information, the authors also provide their analysis regarding the feasibility of the formulation strategies summarized in this review.