Comparison of Downstream Processing of Nanocrystalline Solid Dispersion and Nanosuspension of Diclofenac Acid to Develop Solid Oral Dosage Form

Optimization of Particle Properties of Nanocrystalline Solid Dispersion Based Dry Powder for Inhalation of Voriconazole

A one-step spray drying based process was employed to generate ready-to-use nanocrystalline solid dispersion (NCSD) dry powder for inhalation (DPI) of voriconazole (VRC). The solid dispersion was prepared by spray drying VRC, MAN (mannitol) and soya lecithin (LEC) from mixture of methanol-water. Various formulation and process related parameters were screened, including LEC, inlet temperature, total solid content and feed flow rate to generate particles of geometric size ≤5 µm. Aerosil® 200 was explored as the quaternary excipient either during spray drying or by physically mixing with the optimized ternary NCSD. The powders were extensively characterized for solid form, primary particle size, assay, embedded nanocrystal size, morphology, porosity, density and moisture content. Aerodynamic properties were studied using next generation impactor (NGI), while surface elemental composition and topography were investigated using SEM-EDS (scanning electron microscopy- energy dispersive spectroscopy) and AFM (atomic force microscopy), respectively. At selected inlet temperature of 120 ˚C, total solid content and feed flow rate significantly impacted the size of primary NCSD particles. Size of primary particles increased with increase in total solid content and feed flow rate of the solution. VRC nanocrystals were obtained in polymorphic Form B whereas the matrix of MAN consisted of mixture of polymorphic Forms α, β and δ. SEM-EDS analysis confirmed deposition of Aerosil® 200 on surface of spray dried particles. In addition to increased porosity and reduced density, increase in surface roughness of particles (evident from AFM topographic analysis) contributed to enhanced powder deposition at stages 3 and 4 in NGI. In comparison, physical blending of NCSD with Aerosil® 200 showed improvement in aerosolization due to flow enhancement property.

Pharmaceutical nanocrystals: A promising approach for improved topical drug delivery

The barrier function of skin and non-optimal physicochemical properties of drug present a challenge to skin penetration of many drugs, thus motivating the development of novel drug delivery systems. Recently, nanocrystal-based formulations have been investigated for topical drug delivery and demonstrated improved skin penetration. This review highlights barriers in skin penetration, current techniques to improve topical delivery and application of nanocrystals in conquering obstacles for topical delivery. Nanocrystals can improve delivery through the skin by mechanisms like higher concentration gradient across skin resulting in increased passive diffusion, hair follicle targeting, diffusional corona and adhesion to skin. This would be of interest for formulation scientists for product development of molecules that are 'difficult-to-deliver' topically.