Enhancements in Spray-Dried Powder Functionality, Using Multistage Fluidized-Bed Drying and a New Templating Process

Abstract

Spray drying is a technique that is widely applied to produce dry powders from their liquid or slurry states in the food and pharmaceutical industries. Spray-dried forms of dairy powders may have several advantages, such as greater solubility, dissolution rates and surface areas. However, they are thermodynamically-unstable solids, which may undergo undesirable changes, such as caking after production. To overcome this problem, a fluidized-bed dryer has been used in this study to improve the degree of lactose crystallinity of sweet whey. It has been found that, with controlling the operating conditions in a continuous multi-stage fluidized bed dryer, whey powders can have different degrees of lactose crystallinity with reasonable overall processing times. However, crystalline powders may have some undesirable properties, such as lower dissolution rates. Thus, a new templating method has been developed to create spray-dried powders with high porosity and controlled characteristics, while maintaining the high stability of a crystalline powder. There were significant improvements in the surface areas. These engineered particles were then used as porous excipients in an adsorption technique to evaluate the potential of this technique for improvement of the dissolution characteristics of poorly water-soluble drugs and for content uniformity enhancement by incorporating the drug molecules onto this porous structure. Indomethacin, nifedipine, and acetaminophen as model drugs were studied. This method significantly improved the dissolution rate of these poorly water-soluble drugs due to the nanoconfinement of drug crystals inside the porous structure and the high solubility of porous mannitol. Tunable drug loadings have also been achieved with low variability for the drug content, indicating the ability of this method to produce highly-uniform blends.