(674g) Dry (Solvent-less) Polymer Coating of Microparticles for Control Release Applications

Coating is a necessary unit operation in the pharmaceutical industry for applications ranging from aesthetic improvement (e.g taste, appearance, texture) to the controlled or targeted release of active pharmaceutical ingredients (API) which is critical for the production of efficacious dosage forms.  While solvent-based polymer coating methods are widely used, solvent-less or dry-polymer coating technologies have recently emerged as an attractive alternative to improve upon processing limitations and inefficiencies.  This study introduces a solvent-less coating methodology by which microparticles can be coated with polymers without the use solvents, plasticizers, or heat treatments, noted as being major improvements upon solvent-based and current dry-polymer coating technologies. The method first creates an ordered mixture composed of a micronized polymer adhered to the surface of an API particle by virtue of van der Waals particle interactions resulting in a discrete polymer coating.  Subsequent processing in a high intensity vibratory mixer induces mechanical impactions which deforms the discrete polymer into a continuous coating layer.  As a practical example, ascorbic acid (50 – 500 μm) is coated with the polymer polyethylene wax (6.7 μm).  Polymer coatings were able to prolong the dissolution time of ascorbic acid from seconds to hours depending on the coating thickness and processing conditions.  Detailed characterization and modeling of the coating layer and the release mechanism was also performed.  This novel dry-polymer-coating technique can reasonably be extended to a wide variety of applications in the pharmaceutical industry for control release applications.