Preformulation Studies to Meet the Challenges in the Manufacture of Betaine Solid Dosage Form

Controlling simonkolleite crystallisation via metallic Zn oxidation in a betaine hydrochloride solution

Zinc oxide nanoparticles, with a hexagonal flake structure, are of significant interest across a range of applications including photocatalysis and biomedicine. Simonkolleite (Zn₅(OH)₈Cl₂·H₂O), a layered double hydroxide, is a precursor for ZnO. Most simonkolleite synthesis routes require precise pH adjustment of Zn-containing salts in alkaline solution, and still produce some undesired morphologies along with the hexagonal one. Additionally, liquid-phase synthesis routes, based on conventional solvents, are environmentally burdensome. Herein aqueous ionic liquid, betaine hydrochloride (betaine·HCl), solutions are used to directly oxidise metallic Zn, producing pure simonkolleite nano/microcrystals (X-ray diffraction analysis, thermogravimetric analysis). Imaging (scanning electron microscopy) showed regular and uniform hexagonal simonkolleite flakes. Morphological control, as a function of reaction conditions (betaine·HCl concentration, reaction time, and reaction temperature), was achieved. Different growth mechanisms were observed as a function of the concentration of betaine·HCl solution, both traditional classical growth of individual crystals and non-traditional growth patterns; the latter included examples of Ostwald ripening and oriented attachment. After calcination, simonkolleite's transformation into ZnO retains its hexagonal skeleton; this produces a nano/micro-ZnO with a relatively uniform shape and size through a convenient reaction route.

Dipalmitoylphosphatidylcholine (DPPC): Annealing Strategy to Mitigate Variability in Thermotropic and Moisture Sorption Behavior

Dipalmitoylphosphatidylcholine (DPPC) demonstrated complex differential scanning calorimetry (DSC) thermal behavior. Transitions below 100°C showed variability in their thermotropic reversibility. An experimental design employing a DSC heat-cool-heat-cool-heat cycle and modulated DSC were used to gain insight into the DPPC's complex thermal nature. An annealing strategy was developed to reduce DPPC's thermotropic variability, moisture uptake rate, and rate variability. Samples annealed at 110°C for 5 min provided a reproducible, thermally reversible material. The annealed material also exhibited an 8-fold decrease in moisture sorption rate and a statistically significant (p = 0.0233) 100-fold decrease in water sorption rate variability compared to DPPC "as is." An optimized validated stability-indicating high performance liquid chromatography with evaporative light scattering detection method was developed and showed no change in DPPC chemical stability under the annealing treatment conditions.