Single droplets to particles - size, shape, shell thickness and porosity analyses using X-ray computed tomography

Pore development in viscoelastic foods during drying

In this paper, we present a numerical model that can describe the pore formation/cavitation in viscoelastic food materials during drying. The food material has been idealized as a spherical object, with a core/shell structure and a central gas-filled cavity. The shell represents a skin as present in fruits/vegetables, having a higher elastic modulus than the tissue, which we approximate as a hydrogel. The gas-filled pore is in equilibrium with the core hydrogel material, and it represents pores in food tissues as present in intercellular junctions. The presence of a rigid skin is a known prerequisite for cavitation (inflation of the pore) during drying. For modeling, we follow the framework of Suo and coworkers, describing the inhomogeneous large deformation of soft materials like hydrogels - where stresses couple back to moisture transport. In this paper, we have extended such models with energy transport and viscoelasticity, as foods are viscoelastic materials, which are commonly heated during their drying. To approach the realistic properties of food materials we have made viscoelastic relaxation times a function of Tg/T, the ratio of (moisture dependent) glass transition temperature and actual product temperature. We clearly show that pore inflation only occurs if the skin gets into a glassy state, as has been observed during the (spray) drying of droplets of soft materials like foods.

Advances in Structure Pharmaceutics from Discovery to Evaluation and Design

Drug delivery systems (DDSs) play an important role in delivering active pharmaceutical ingredients (APIs) to targeted sites with a predesigned release pattern. The chemical and biological properties of APIs and excipients have been extensively studied for their contribution to DDS quality and effectiveness; however, the structural characteristics of DDSs have not been adequately explored. Structure pharmaceutics involves the study of the structure of DDSs, especially the three-dimensional (3D) structures, and its interaction with the physiological and pathological structure of organisms, possibly influencing their release kinetics and targeting abilities. A systematic overview of the structures of a variety of dosage forms, such as tablets, granules, pellets, microspheres, powders, and nanoparticles, is presented. Moreover, the influence of structures on the release and targeting capability of DDSs has also been discussed, especially the in vitro and in vivo release correlation and the structure-based organ- and tumor-targeting capabilities of particles with different structures. Additionally, an in-depth discussion is provided regarding the application of structural strategies in the DDSs design and evaluation. Furthermore, some of the most frequently used characterization techniques in structure pharmaceutics are briefly described along with their potential future applications.

A Critical Review on Engineering of d-Mannitol Crystals: Properties, Applications, and Polymorphic Control

d-mannitol is a common six-carbon sugar alcohol, which is widely used in food, chemical, pharmaceutical, and other industries. Polymorphism is defined as the ability of materials to crystallize into different crystal structures. It has been reported for a long time that d-mannitol has three polymorphs: β, δ, and α. These different polymorphs have unique physicochemical properties, thus affecting the industrial applications of d-mannitol. In this review, we firstly introduced the characteristics of different d-mannitol polymorphs, e.g., crystal structure, morphology, molecular conformational energy, stability, solubility and the analytical techniques of d-mannitol polymorphisms. Then, we described the different strategies for the preparation of d-mannitol crystals and focused on the polymorphic control of d-mannitol crystals in the products. Furthermore, the factors of the formation of different d-mannitol polymorphisms were summarized. Finally, the application of mannitol polymorphism was summarized. The purpose of this paper is to provide new ideas for a more personalized design of d-mannitol for various applications, especially as a pharmaceutical excipient. Meanwhile, the theoretical overview on polymorphic transformation of d-mannitol may shed some light on the crystal design study of other polycrystalline materials.