Particle Engineering of Polymers into Multifunctional Interactive Excipients

Both natural and man-made polymers are widely utilized as tablet binders and filler-binders. The physicochemical and mechanical properties such as particle size, shape and deformation behavior of polymeric binders are key in their effective use. Many such binders are applied as solution in a wet granulation process, which facilitate its facile distribution leading to improved effectiveness as a binder. Direct compression and dry granulation are recognized as routes with reduced process complexity and cost. These processes require a binder to be employed in a dry form and it can be more difficult to obtain a homogeneous distribution of a dry binder in a powder formulation. Therefore, these binders are required in high proportions to generate mechanically strong tablets. At lower proportions, they often are insufficient to create mechanically strong tablets. Recently, innovations in the generation of co-processed excipients have been proposed. Co-processing is a popular means of improving excipient functionalities, where two or more existing excipients are combined by some suitable means to generate new structures with improved and often combined functionalities as compared to the component excipients. Particle size reduction is known to improve the binder properties of an excipient, but also makes it highly cohesive and hard to blend. Via particle engineering, surface structure of smaller particles can be tailored to optimize the cohesive-adhesive balance (CAB) of the powder, allowing formation of interactive mixtures. This chapter reviews recent efforts to engineer surface-modified polymeric micro-excipient structures with the inherent ability to not only form an interactive mixture efficiently and provide flow enhancement, but also to create harder tablets at lower proportions. Hence, this approach represents a potential novel multifunctional prototype polymeric micro-excipient for direct compression and dry granulation processes.