Impact of carrier particle surface properties on drug nanoparticle attachment

HYPOTHESIS

The stabilization and isolation to dryness of drug nanoparticles has always been a challenge for nano-medicine production. In the past, the use of montmorillonite (MMT) clay carrier particles to adsorb drug nanoparticles and maintain their high surface area to volume ratio after isolation to dryness has proven to be effective. We hypothesise that the distribution of hydrophilic and hydrophobic patches on the clay's surface as well as its porosity/roughness, hinder the agglomeration of the drug nanoparticles to the extent that they retain their high surface area to volume ratio and display fast dissolution profiles.

EXPERIMENTS

In this work, the distribution of hydrophobicity and hydrophilicity, and the porosity/roughness, of the surface of selected silica carrier particles were varied and the impact of these variations on drug nanoparticle attachment to the carrier particle and subsequent dissolution profiles was studied.

FINDINGS

The fastest dissolution profiles at the highest drug nanoparticle loadings were obtained with a periodic mesoporous organosilane carrier particle which had a homogeneous distribution of hydrophobic and hydrophilic surface properties. Carrier particles with rough/porous surfaces and a combination of hydrophobic and hydrophilic patches resulted in nanocomposite powders with faster dissolution behaviour than carrier particles with predominantly either a hydrophobic or hydrophilic surface, or with non-porous/smoother surfaces.

Crystal nucleation of salicylamide and a comparison with salicylic acid

Nucleation behaviour of salicylamide in different solvents was determined and compared with salicylic acid, attempting to progress the rationalization of the influence of the solvent and solute on crystal nucleation of organic compounds in solution.

Face indexing and shape analysis of salicylamide crystals grown in different solvents

The effect of solvent on salicylamide's crystal habit was investigated. It is deduced that ethyl acetate is adsorbed more strongly on the faces, the increased size of which, can explain the shape change.

Carrier particle design for stabilization and isolation of drug nanoparticles

Nanoparticles of poorly water-soluble drugs were prepared in suspension via antisolvent precipitation in order to improve their dissolution behaviour. Insoluble, surface-functionalized, micron-range, clay carrier particles were employed for the dual purpose of stabilizing the nanoparticles in suspended state, and facilitating their unhindered isolation to solid state; often a challenging step in nanoparticle production. The carrier particles, which were functionalized with an optimal level of cationic polymer (protamine), attracted negatively-charged nanoparticles to their surface as a uniform and segregated nanoparticle layer, at drug loadings up to 9% w/w. By using carrier particles to stabilise the nanoparticles on their surface, the traditionally used solubilised nanosuspension stabilisers could be eliminated, thus avoiding time-consuming stabiliser screening tests. The carrier particle system facilitated stabilisation of nanoparticles in suspension, isolation of nanoparticles to the solid state via filtration, and preservation of fast nanoparticle-induced dissolution rates of the dried nanoparticle-carrier composites, indicating preservation of their high surface area during drying. The process was validated with two poorly water-soluble BCS Class II drugs, fenofibrate and mefenamic acid, both of which demonstrated negative surface charge in aqueous suspension.