Solid Lipid Matrices for Delivery of Laundry Actives and Lipid Membrane Transport

Abstract

The work presented in this thesis reports the preparation and characterisation of novel solid lipid microparticle (SLM) and solid lipid nanoparticle (SLN) systems for applications in delivery of laundry actives and transport of electroactive substances into lipid membranes. The SLM and SLN systems studied are: silicone-loaded SLM, dye-loaded SLM, dual-active SLM (both silicone and dye) and ferrocene-loaded SLN (Fc-SLN).

Silicones are used as fabric softeners in laundry applications and dyes are used to enhance the hue of fabrics. The incorporation of two actives into one, dual-active SLM, is a concept that could enable compact formulation and optimized formulation manufacture. The ferrocene-loaded SLN system represent the group of electroactive nanoparticles that could potentially find applications in biosensors, targeted delivery and other biomedical applications.

The SLM and SLN systems were prepared using lauric acid as the lipid matrix. Silicone-loaded SLM systems were prepared using solvent-assisted methods with either ethanol or n-hexane as the solvent. They were stabilized with a combination of a primary alcohol ethoxylate (C14-15) (neodol 45-7) and polysorbate 80 (tween 80) as surfactant/co-surfactant). The silicones used were: polydimethylsiloxane (PDMS)(10,000 cST and 100,000 cSt), terminal amino-functionalised silicone (TAS) and a tertiary amino-functionalised silicone (PK10).

The dye-loaded SLM systems, incorporating Coomassie Brilliant Blue R (CBB or BB) and ethyl violet (EV, Basic Violet 4) as hueing dyes were prepared using the double emulsion method, also descriptively known as the water-in-oil-in-water (w/o/w) emulsion method. The inner emulsion, w/o was stabilized using a low HLB surfactant, Brij 80 and the outer emulsion o/w was stabilized using a high HLB surfactant, tween 80. For the dual-active SLM system, PK10 silicone was added to the lipid phase before emulsification.

The Fc-SLN system was prepared using the solvent emulsification/evaporation method. The surfactants used were poloxamer 188 and tween 80. The lipid membrane systems used were: solid-supported self-assembled monolayer (SAM) and tethered bilayer lipid membrane. The SAM was prepared by chemisorption of a thiolipid, 1,2-dipalmitoyl-sn-glycero-phosphothioethanol (DPPTE) onto a gold surface. Self-assembled monolayers were used as a lower leaflet or tether for the BLM system; an upper leaflet of 1-palmitoyl-2-oloeyl-sn-glycero-3-phosphocholine (POPC) was added by vesicle fusion. The characterisation and penetration of Fc-SLN into lipid membranes was studied using electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and Resonance Enhanced Surface Impedance (RESI).

The SLM and SLN systems where characterised using laser diffraction and dynamic light scattering (DLS) for particle size analysis, optical microscopy and electron microscopy for morphology and particle size, small angle X-Ray Scattering (SAXS) and differential scanning calorimetry (DSC) for crystallinity and structural arrangement and chemical analysis using FTIR, solid state NMR and TGA.