The rapid, real-time measurement capabilities of the Zetasizer Nano system from Malvern Panalytical have enabled quantified nanoscale characterization of the environmental sensitivity of novel solubilization nanoparticles.
A joint research paper, presented at Particulate Systems Analysis 2008  and a new publication in Cosmetics & Toiletries Sep 2010 , illustrate the application of dynamic light scattering (DLS) to investigate the effects of pH and temperature on the structure and particle size of environmentally-responsive Lipodisq® systems produced by Malvern Panalytical Cosmeceutics Ltd, UK.
Lipodisqs are designed to mimic naturally occurring high-density lipoproteins which bind cholesterol for transport back to the liver for excretion. Composed of a phospholipid membrane core bound together into spherical or disc-like structures by a responsive chaperone molecule (a protein that assists non-covalent folding/unfolding), these particles can enclose and transport oil soluble molecules through an aqueous environment. Used to improve topical delivery of an active botanic or pharmaceutical ingredient, Lipodisqs can be engineered to withstand or respond to particular environmental specifications.
Using the Zetasizer Nano it was demonstrated that Poly(styrene-maleic acid) Lipodisq particles are sensitive to changes in pH, increasing in particle size from ~12nm to >200 nm over a pH range of 7.7 to 5.7. The temperature sensitivity of Poly(styrene-maleic acid) Lipodisq particles was also shown with an increase in particle size from ~20 nm to ~300 nm over a temperature range of 20°C to 90°C.
Both complexes were shown to spontaneously reassemble when these environmental changes were reversed.
Dynamic light scattering (DLS) is a particle sizing technique that delivers rapid, real-time data that are sensitive enough to demonstrate subtle changes over time for sizes below 1 nm. As such it is particularly suited to the investigation of environmentally triggered particle size changes in topical applications such as creams, gels and lotions.
 Harper, A., Kazsuba, M, Connah, M. & Tonge, S. pH and Temperature Responsive
Novel Nanoparticles Characterised by Dynamic Light Scattering Paper presented at
Particulate Systems Analysis 2008 (PSA 2008), Stratford-upon-Avon, UK. Sep 2008
 Harper et al, Environmentally responsive nanoparticles for delivery as
assessed via light scattering and infrared imaging, Cosmetics & Toiletries Vol
125, No 9, Sep 2010
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