Nanogold for multiple drug delivery

Materials World magazine
1 Feb 2009

Exploring laser excitation of gold nanoparticles will enhance international research into these materials for controlled drug delivery, say researchers at MIT, Cambridge, USA.

They found that gold nanorods of different shapes respond to different infrared wavelengths, enabling selective melting of the carriers and release of the medication attached to their surfaces. ‘Just by controlling the wavelength, we can choose the release time for each drug,’ says Andy Wijaya, a graduate student in chemical engineering at MIT. This enables external control of the dosage, rather than relying on passive release to treat diseases such as cancer and HIV with multiple medicines.

Kimberly Hamad-Schifferli, Professor of Biological and Mechanical Engineering at MIT, says delivery devices that can release two drugs already exist, but the time of release has to be built in and cannot be externally stipulated. A system based on infrared light excitation could deliver up to three to four drugs in a controlled manner.

‘There is existing work using gold nanorods for laser trigger release, but it is always for a single species,’ adds Hamad-Schifferli.

The team at MIT has synthesised short and long gold nanorods and in vitro loaded each one with a different strand of DNA. As well as different infrared wavelengths, they have found that DNA release is ‘tunable’ by adjusting the laser power.

The next stage will be in vivo testing with a cocktail of drugs to explore stability in blood and circulation, as well as the targetting of affected areas by ‘decorating’ the nanorods with antibodies or receptors.

Dr Richard Holliday, Head of Industrial Applications at the World Gold Council in London, UK, is optimistic about the research. ‘This expands on the opportunities that gold nanoparticles can provide in the medical field [and] potentially offers new directions for treatments,’ he says.

‘The use of gold nanomaterials has now started to penetrate the commercial medical industry. Nanospectra Biosciences Inc [in Houston, USA] is commercialising the use of gold nanoshells for selective thermal destruction of solid tumours. The company is currently enrolling patients for trials.

He adds, ‘Cytimmune Sciences [Rockville, USA] has already completed phase one patient trials and early clinical data indicates that their nanogold-based technology accumulates in and around tumour sites, avoids uptake by organs like the liver and is largely absent from surrounding healthy tissues’.

Hamad-Schifferli believes that once the research is proved in vivo, the main issue will be cost. ‘The ultrafast laser beam is a large and expensive piece of equipment so that could be [addressed]. Also gold nanorod synthesis requires gold salts, and that is not cheap.’