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Clinical trials addressing the viability of lipid and nanoparticle-based solid dosage forms for the oral delivery of poorly water-soluble drugs are limited to date. This Phase I study aimed to assess the comparative tolerability and oral pharmacokinetics of a novel silica nanoparticle-lipid hybrid formulation encapsulating ibuprofen (i.e., Lipoceramic-IBU) with reference to a commercial tablet (i.e., Nurofen®). The test (Lipoceramic-IBU) and reference (Nurofen®) ibuprofen formulations were characterised for physicochemical properties and in vitro solubilisation performance prior to the clinical study. A randomised, double-blinded, one-period single oral dose (20 mg ibuprofen) study was performed in 16 healthy male subjects under fasting conditions. Encapsulation of ibuprofen in a molecularly dispersed form in the Lipoceramic nanostructured silica-lipid matrices was shown to produce superior drug solubilisation in comparison to Nurofen® and the pure drug during a two-step dissolution (or solubilisation) study in aqueous buffers of pH 1.2 followed by pH 6.5. Pharmacokinetic profiles revealed an approximately 1.95-fold increased bioavailability (p=0.02) and a 1.5-fold higher maximum plasma concentration (p=0.14) for Lipoceramic-IBU with reference to Nurofen®. Review of the safety assessments, including physical examinations, clinical laboratory tests and reports of adverse events, confirmed negligible acute side effects related to the administration of blank and ibuprofen-loaded Lipoceramic formulations. This first in man study of a dry lipid and nanoparticle-based formulation successfully demonstrated the safe use and effectiveness of the nanostructured Lipoceramic microparticles in mimicking the food effects for optimising the oral absorption of poorly water-soluble compounds. Refereed/Peer-reviewed

Thesis (PhD)--University of South Australia, 2009. Includes bibliographical references. Toxicological aspects of nanoparticle-coated emulsions were highlighted with the investigation of the in-vitro porcine skin penetration of silica nanoparticles. Results suggested that silica nanoparticles were uptaken by skin and reached up to the viable epidermis and dermis with negligible permeation through the whole skin. In addition, invitro viability assay using a human keratinocyte cell line suggested a dose-dependent cytotoxicity of silica nanoparticles which was more pronounced in oleylamine compared to lecithin-stabilised emulsions. Based on this study, a new insight was gained in the fundamental aspects of nanoparticle-coated emulsions; a significant implication of this research may be in the development of novel topical carriers with enhanced chemical stability of payload, controlled release kinetics, targeted skin delivery, and potentially limited systemic exposure and toxicity. In addition, the potential mechanisms of the improved physicochemical properties and dermal delivery from nanoparticle-coated submicron o/w emulsions with mixed interfacial layers composed of classical surfactants and silica nanoparticles are proposed.

The influence of silica nanoparticle coating on the chemical stability and phase distribution of all-trans-retinol in submicron oil-in-water emulsions is reported. The chemical stability was studied as a function of UVA+UVB irradiation, and storage temperature (4 degrees C, ambient temperature, and 40 degrees C) for emulsions stabilised with lecithin and oleylamine as the initial emulsifier with and without silica nanoparticle layers. The chemical stability of all-trans-retinol was highly dependent on the emulsifier type and charge, with negligible influence of the initial loading phase of silica nanoparticles. A significant stability improvement (approximately 2-fold increase in the half-life of the drug) was observed by nanoparticle incorporation into oleylamine-stabilised droplets (i.e. electrostatically coated), with no considerable effect for partially coated lecithin-stabilised droplets. The chemical stability of all-trans-retinol incorporated into nanoparticle-coated emulsions was well-correlated to the phase distribution of the active agent, and the interfacial structure of emulsions as determined by freeze fracture-SEM. Specifically engineered nanoparticle layers can be used to enhance the chemical stability of active ingredients in emulsion carriers.

Purpose: The aim of this research is to investigate the dermal delivery of all-trans-retinol from nanoparticle-coated submicron oil-in-water emulsions as a function of the initial emulsifier type, the loading phase of nanoparticles, and the interfacial structure of nanoparticle layers. Methods: The interfacial structure of emulsions was characterized using freeze-fracture-SEM. In-vitro release and skin penetration of all-trans-retinol were studied using Franz diffusion cells with cellulose acetate membrane, and excised porcine skin. The distribution profile was obtained by horizontal sectioning of the skin using microtome-cryostat and HPLC assay. Results: The steady-state flux of all-trans-retinol from silica-coated lecithin emulsions was decreased (up to 90%) and was highly dependent on the initial loading phase of nanoparticles; incorporation from the aqueous phase provided more pronounced sustained release. For oleylamine emulsions, sustained release effect was not affected by initial location of nanoparticles. The skin retention significantly (p ≤ 0.05) increased and was higher for positive oleylamine-stabilised droplets. All-trans-retinol was mainly localized in the epidermis with deeper distribution to viable skin layers in the presence of nanoparticles, yet negligible permeation (∼1% of topically applied dose) through full-thickness skin. Conclusions: Sustained release and targeted dermal delivery of all-trans-retinol from oil-in-water emulsions by inclusion of silica nanoparticles is demonstrated. Refereed/Peer-reviewed