David Morton

This Letter reports a technique of measuring polar surface energy distributions of lactose using inverse gas chromatography (IGC). The significance of this study is that the total surface energy distributions can now be characterized by combining the already known dispersive surface energy distribution with polar surface energy distribution determined in this study. The polar surface energy was calculated from the specific free energies for surface interactions with a monopolar basic probe, ethyl acetate, and a monopolar acidic probe, dichloromethane.

In this study, we investigated the applicability of cohesive-adhesive balance (CAB) model to predict the interactive mixing behaviour of small excipient particles. Further, we also investigated the application of this CAB model to predict the flow and compactability of resultant blends. Excipients created by co-spraying polyvinylpyrrolidone (PVP, a model pharmaceutical binder) with various L-leucine concentrations were used for this study. Paracetamol was used as model active pharmaceutical ingredient (API). The surface energy was used to derive the work of cohesion (wco) and work of adhesion (wad) to predict the interactive mixing behaviour of the excipients with paracetamol. The blends were visualized under a scanning electron microscopy microscope to assess the interactive mixing behaviour. In addition, the flow performance and tabletting behaviour of various blends were characterized. The surface-energy derived work of adhesion (wad) between excipient and paracetamol particles i...

The amino acid l-leucine has been demonstrated to act as a lubricant and improve the dispersibility of otherwise cohesive fine particles. It was hypothesized that optimum surface l-leucine concentration is necessary to achieve optimal surface and bulk powder properties. Polyvinylpyrrolidone was spray dried with different concentration of l-leucine and the change in surface composition of the formulations was determined using X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS). The formulations were also subjected to powder X-ray diffraction analysis in order to understand the relationship between surface concentration and solid-state properties of l-leucine. In addition, the morphology, surface energy and bulk cohesion of spray dried formulations were also assessed to understand the relation between surface l-leucine concentration and surface and bulk properties. The surface concentration of l-leucine increased with higher feed concentrations and plateaued at about 10% l-leucine. Higher surface l-leucine concentration also resulted in the formation of larger l-leucine crystals and not much change in crystal size was noted above 10% l-leucine. A change in surface morphology from spherical to increasingly corrugated particles was also recorded. Specific collapsed/folded over particles were only seen in formulations with 10% or higher l-leucine feed concentration suggesting a change in particle surface formation process. In addition, bulk cohesion also reduced and approached a minimum with 10% l-leucine concentration. Thus, the surface concentration of l-leucine governs particle formation and optimum surface l-leucine concentration results in optimum surface and bulk powder properties.

ABSTRACT Tablets make up approximately one third of all drug dosage forms which makes tablet manufacture a common process in the pharmaceutical industry. The unified compaction curve [1] is a model developed initially to look at the impact of the roller compaction conditions on the tablet strength. The tensile strength of the tablets made from formulations containing at least 50% microcrystalline cellulose produced at roller compaction pressures were measured and the profiles were collapsed into a single master “unified compaction curve” (UCC). This allowed for the tablet strength to be predicted from the roller compaction condition and formulations and target the required tablet strength criterion set by standards or specifications [1].

ABSTRACT Silk particles have gained interest in recent years due to their use in cosmetic, coating, biomedical and other advanced materials applications. However there is a limited understanding of the powder surface and bulk properties, which include the cohesion and flowability that play important roles in powder production and applications. We have produced silk powders of different size and shape by altering the milling processing and chemical pre-treatments and studied their dispersive and acid/base surface properties using an inverse gas chromatography technique. An FT4 rheometer was used to measure powder compression and flow behaviours. The study demonstrated that the surface energy of silk particles was reduced when prepared from alkaline hydrolysed fibre. All samples have amphoteric surfaces and the concentration of acidic groups increased after milling while surfaces remained predominantly basic in nature. The compressibility, bulk density and cohesion of the powders depended both on the surface energy as well as the physical characteristics such as particle size, surface area, aggregation state and the testing conditions, notably the consolidated and unconsolidated states. The study has helped to understand how silk particle properties such as size, moisture absorption, surface chemistry and flowability were changed when using different fabrication approaches.