Characterisation of a novel solid lipid nanoparticle carrier system based on binary mixtures of liquid and solid lipids

A drug carrier of colloidal lipid particles with improved payloads and enhanced storage stability was investigated. Based on the experiences with hard fats nanoparticles, a new type of solid lipid nanoparticles (SLN) has been developed by incorporating triglyceride containing oils in the solid core of said particle. The structure and mixing behaviour of these particles were characterised and practical implications on controlled release properties tested. Nanoparticles were characterised by their melting and recrystallisation behaviour as recorded by differential scanning calorimetry (DSC). Polymorphic form and bilayer arrangement were assigned by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). Size distribution and storage stability were investigated by laser diffractometry (LD). Release properties were studied by drug release model according to Franz. A medium chain triglyceride oil was incorporated successfully in a matrix of a solid long chain glyceride. The crystal order was greatly disturbed, however, the carrier remained solid. The oil inside the particle remained in a liquid state and induced a slight shift form the beta' polymorph to the beta(i) form. Long spacings varied within 0.1 nm with increasing oil loads. Nanoparticles with low oil concentrations showed sustained release properties. Improved drug load levels were encapsulated by lipid particles supplemented with oily constituents. Thus, the presented carrier adds additional benefits to the well-known opportunities of conventional SLN and is suited for topical use. (C) 2000 Published by Elsevier Science B.V. All rights reserved.