Research using a laser beam trap could help improve the effectiveness of asthma inhalers by modelling how the drug particles behave as they are projected through the air. The scientists’ findings could improve the effectiveness of inhalers for the over 5 million people in the UK suffering from asthma.
Using the Octopus laser imaging facility at the UK Science and Technology Facilities Council (STFC) Central Laser Facility, the scientists trapped individual solid particles of the drug salbutamol sulphate. They suspended them in air to test how they behave in conditions modelled to simulate those in the human respiratory system.
More than 73 million inhalers are used every year in the UK. By studying how the expelled drug particles might behave as they enter the human respiratory tract and travel into the lungs, the research could lead to an improvement in the formulation of these drug delivery systems.
This is the first time that tests on these microscopic particles have been carried out in an environment that mimics their journey from inhaler to lung. The research is published in the Royal Society of Chemistry journal, Chemical Communications.
Dr Andy Ward, from the STFC Central Laser Facility, explained: ‘We captured each particle by trapping it between two focused laser beams, and then tested its behaviour in different temperatures and levels of humidity. Our tests show how water is adsorbed by following changes in chemical bond vibrations. Usually such tests are done on a glass slide so this is the first time the particles have been tested while airborne, as they would be when travelling through the respiratory tract.’
The human respiratory tract is anatomically evolved to prevent particles being inhaled. Dr Peter Seville from the University of Birmingham’s School of Clinical and Experimental Medicine, one of the researchers on the project, explained: ‘To overcome the natural defence mechanisms of the body, complex delivery devices and extremely small drug particles are required.’
The particles are typically 2-5µm in diameter, increasing in size with any moisture that clings to them. Moisture attaching to the particle can affect the site of particle deposition within the lung and give rise to less effective treatment.
Using Raman spectroscopy techniques to measure the vibration and wavelength of light from molecules, the research team was able to provide a new method of studying the salbutamol sulphate as it exited from a commercially-available inhaler.
They discharged the inhaler into the optical laser trap, without changing the drug’s physical and chemical properties, captured a microscopic particle in air and recorded its size, shape and chemical signature to show evidence of any water adsorption. This all happened within a matter of seconds, closely replicating the time, relative humidity and trajectory of the particle in the lung.
The research team comprised scientists from the Universities of Birmingham and Cambridge, Imperial College London and the STFC Central Laser Facility, based at the Research Complex at Harwell, Oxfordshire.