Designing drug nanodispersions

Oil-in-water microemulsion with steroidal drug (testosterone) shown.

Cartoon of an oil-in-water microemulsion with steroidal drug (testosterone) shown.
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Oil-in-water microemulsions are spontaneously formed, nanosized dispersions of oil in water stabilised by surfactant.

They have recently found favour as ‘solvents’ in which to encapsulate poorly water-soluble drugs. At present, however, there is little understanding as to the combinations of oil and surfactant that are most effective for encapsulating drug. We have been using small angle neutron scattering to perform the first studies to determine the location of a range of steroidal drugs encapsulated within these nanodispersions, with a view to determining the oil/surfactant combinations best for drug delivery. We have used the technique of neutron contrast variation by employing deuterated and hydrogenous oils and surfactants. By fitting the neutron scattering results to models of microemulsion shape and size, the location of the drugs within the microemulsions has been deduced. At low steroid concentration, the drug is preferentially located in the surfactant shell, while at higher concentrations it enters the particle’s oil core – thus demonstrating the importance of the oil in determining the level of drug encapsulation.

MJ Lawrence, DJ Barlow (King’s College London), RK Heenan (ISIS)

Research date: December 2007

Further Information

MJ Lawrence and DJ Barlow (2006) in Encyclopedia of Pharmaceutical
Technology (Third Edition), J Swarbrick (Ed), Marcel Dekker Inc.

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