A new use for empty space – Microbubbles
The Leeds Microbubble Symposium (organised by the Leeds Microbubble Consortium, University of Leeds), held on the 17th and 18th July in a 16th century manor house, drew together delegates from European and American institutions in order to discuss a growing area of medical research – the diagnosis and treatment (or ‘theranostics’) of disease using bubbles.
Theranostic microbubbles generally consist of gas in a phospholipid, protein or polymer shell, and can be detected and exploded using ultrasound. The former makes them useful to the imaging of tumors and clogged blood vessels. That these bubbles can be made to explode-on-demand makes it possible to distribute therapeutics, attached to the microbubble, throughout diseased tissue. The size of the explosion is controlled by the gas chosen to fill them. Given the non-invasiveness of microbubble therapy and diagnosis, it is little wonder that this area of medical research is rapidly growing.
The presentations made over the two-day conference illustrated the potential usefulness of microbubbles as relatively non-invasive and safe theranostics. The complexity of ensuring that this is the case was also illustrated. For biopharmaceutical applications, for instance, the microbubble, usually in the size range of 1-10 µM, is often surrounded by liposomes, each generally having a diameter of 100 – 500 µM. These liposomes can be packed with biopharmaceuticals, giving the latter a fatty protective layer and ensuring that they are only released when required. Characterization of the microbubbles, and associated liposomes, is essential to ensure they do what they are meant to.
The highly buoyant nature of microbubbles makes their analysis unsuited to many traditional sizing methods. On the other hand, sizing techniques that can measure the buoyancy of particles, such as the Resonant Mass Measurement (RMM) method that the Malvern Archimedes employs, are perfectly suited to such applications. Malvern’s range of DLS measuring techniques can be applied to the sizing of liposomes. With charge being an important factor in the stability and targeting of drug delivery systems, zeta potential measurements also find application in the wider field, such as theranostic gold nanoparticle analysis.
However this fascinating field of research grows and develops, Malvern Instruments should have a major role to play in guaranteeing the efficacy of what comes out of it.