Researchers from Oxford have presented new data applying nanoparticle tracking analysis (NTA) to size and count cellular microvesicles and exosomes at a low concentration.
This was when used in conjunction with fluorescent labels to selectively determine and analyse specific types of vesicle within a complex sample.
This took place during a two-day conference in Oxford, 'Micro and nanovesicles in health and disease', organised by Dr Paul Harrison from the Oxford Haemophilia and Thrombosis Centre at the Churchill Hospital in Oxford and Ian Sargent, professor of Reproductive Science in the Nuffield Department of Obstetrics and Gynaecology, University of Oxford.
Most researchers concur that the high levels of microvesicles and/or exosomes are associated with thrombotic diseases, cardiovascular disease and some cancers.
'Many cells shed small vesicles in a regulated way, which plays a key role in intercellular communication,' said Prof Sargent, leading the research at the Nuffield Department of Obstetrics and Gynaecology, University of Oxford.
In general, there are two types of vesicle: microvesicles, which directly bud from the plasma membrane, and nanovesicles, which are released by exocytosis from multivesicular bodies of the endosome.
Both are involved in cell signalling.
They carry diverse membrane and cytosolic proteins, as well as messenger and microRNAs.
They can affect the physiology of their target cells in various ways, from inducing intracellular signalling following binding to receptors, to conferring new properties after the acquisition of new receptors, enzymes or genetic material by fusion or endocytosis.
They participate in physiological processes, including haemostasis and thrombosis, inflammation, immune interactions and angiogenesis.
'Nanosight's NTA technique is a major step forward in analytical capability, taking the limits of flow cytometry down almost an order of magnitude,' said Prof Sargent.
'It is rapid and, in common with flow cytometry, characterises polydispersity well,' he added.
Also at this conference, Edwin van der Pol from the Academic Medical Center at the University of Amsterdam presented a theoretical comparison of analytical techniques for microvesicles and exosomes.
This confirmed the advantages of using NTA for studying vesicles sized from 50-400nm.
The previously preferred technique was flow cytometry.
However, van der Pol concluded this has a practical lower limit of 300nm.
Similarly, electrozone sensing is not able detect at such small sizes.
He added that, while Dynamic Light Scattering (DLS) is able to identify very small particles, it generally biases towards large particles in polydisperse samples, so this misreporting renders it of little value.
It is also not able to make concentration measurement.
