A new scientific technique being developed by the National Physical Laboratory (NPL) shows how quickly particles are absorbed into the skin. It promises to be a useful tool in developing more effective topical products.
The technique – ambient surface mass spectrometry – was invented in 2004 and provides real-time analysis of chemical samples.
The National Physical Laboratory (NPL), the UK’s National Measurement Institute, is developing the metrology to make it reliable for use in areas such as chemical testing for the skin cream industry.
NPL’s breakthrough technique involves improving signal stability to provide more detailed micron resolution, which has yielded important insights into skin cream absorption. This process is particularly significant for those working in pharmaceutical r&d and medical processes, including transdermal drug delivery, as the technique can also measure how different skin types absorb chemicals.
The technique has been used by NPL, working with industry partners, to test key ingredients from samples including sunscreen agents, solvents and aromas, as well as siloxanes, a common ingredient in personal care products.
The speed and detail with which ambient surface mass spectrometry analyses these samples will help new products progress through the r&d stage, reducing the time it takes for them to appear on the pharmacy or supermarket shelves.
Ian Gilmore, project lead at NPL, says: ‘The project has shown scientists developing medicinal and personal care products how quickly active ingredients distribute and absorb into the skin. This will be important in formulating the chemical make-up of new skin creams to make them as effective as possible.
People of different ethnicities absorb chemicals very differently; this is very important for controlled transdermal drug delivery using a skin patch
‘Interestingly, it is known that people of different ethnicities absorb chemicals very differently, and this method could be used to measure the rates. This is very important for controlled transdermal drug delivery using a skin patch.’
Mass spectrometry identifies substances on a sample from their mass, and has found uses such as detecting drugs and explosives. Until relatively recently, the technique for surfaces could only be carried out in a vacuum.
A few years ago a technique called Desorption Electrospray Ionisation (DESI) was developed by Zoltán Takáts, Graham Cooks and colleagues at Purdue University, allowing ambient mass spectrometry to be carried out for the first time on surfaces.
DESI involves spraying a surface, such as human tissue, with water and alcohol droplets. These desorb chemicals from the surface that are then transferred into the mass spectrometer. This allows real-time testing of how chemicals are absorbed into skin.
More reliable measurements using this technique will allow even better understanding of molecular behaviour. The challenge has been to improve the signal stability and to optimise the parameters so that repeatable measurements can be made.
NPL is developing other important ambient surface mass spectrometries such as Plasma Assisted Desorption Ionisation (PADI), which uses a plasma plume instead of chemical spray and can, in theory, offer spatial resolutions of 10µm. A project starting this summer will investigate new techniques to get below 1µm.
NPL welcomes interest in this project from industry or academic partners and is currently looking to establish a Centre of Excellence for Mass Spectrometry Imaging.
