Nanotechnology
Key staff: Dr Lisa Benée
The behaviour of sub-micron-sized particles, dispersed in liquids, can be manipulated for opportunities across a vast range of products used in fabric care, home care and beauty care. Many colloidal systems reported in scientific literature have yet to be fully exploited. Among the possible particulate carriers are cross-linked micelles, niosomes, solid lipid nanospheres, nanocapsules and microgel systems.
Crosslinked micelles
Micelles are self-forming particles that are prepared from individual surfactant molecules that have a water-loving and a water-hating component. The surfactant molecules orientate themselves to form spheres where the water-loving component is on the outside and in contact with the water.
The water-hating component remains inside the sphere, preferring to interact with itself rather than with the water. This hydrophobic core makes them ideal carrier systems for water-hating small molecules. Crosslinked micelles are similar. However, they are held in their configuration much more tightly and are therefore more robust. Typically prepared in the size range 5–50nm, they offer more protection than conventional micelle systems do. Size and physico-chemical properties can be manipulated by varying the composition or molecular weight of the surfactant.
Niosomes
Liposomes are vesicles or “bags” in which an aqueous volume is entirely enclosed by a membrane composed of lipid (fat) molecules, usually phospholipids. Niosomes are in many respects similar but are prepared from non-ionic surfactants instead of phospholipids. The low cost of the surfactants and the greater stability of niosomes, as well as their enhanced organoleptic properties (taste, colour, odour and feel), make them an attractive alternative to liposomes.
Solid lipid nanospheres
Prepared by homogenisation of a melted lipid in an aqueous surfactant solution, these colloidal carrier systems have good bioavailability, stability and low toxicity. The inclusion of an active or other small molecule does not affect the particle stability or particle size, which can be between 10nm–2mm. The matrix can release the incorporated active/chemical entity either by heating the matrix or by rubbing the nanospheres on to a material such as human skin or fabric.
Nanocapsules
Liquid-filled capsules can be prepared with an aqueous or organic core to enable solubilisation, stability and protection of compounds in a cross-linked polymer matrix. These compounds can be released by the rupture of the nanocapsule membrane in a burst profile.
Microgels
Materials that respond to subtle changes in external stimuli may be described as “intelligent” or “smart”, for example, colloidal microgels. Acting like microsponges, when held in dispersion they undergo a conformational change as a function of temperature, pH, ionic strength and solvency. They can exhibit as much as a fourfold change in particle volume as they shrink and swell in response to environmental conditions.
These microsponges, with their responsive porous network, can be used for a variety of applications, including drug adsorption (poorly soluble drugs) and drug protection (sensitive to pH extremes), as well as drug delivery. These nano-particulate systems provide a vehicle to deliver a number of actives or volatile components.
The range of commercial applications of these materials is expanding, as is this area of research.