Researchers from Oxford have recently presented exciting new data applying
nanoparticle tracking analysis (NTA) from Nanosight
to size and count both cellular microvesicles and exosomes at a low concentration
and, 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 & 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.
The NanoSight NS500 system like the one being used in Oxford by the Sargent group
Most researchers concur that the high levels of microvesicles and/or exosomes
are associated with (i.e. potential biomarkers for) thrombotic diseases, cardiovascular
disease and some cancers. Leading the research at the Nuffield Department of
Obstetrics and Gynaecology, University of Oxford, Professor Ian Sargent says
“many cells shed small vesicles in a regulated way which plays a key role
in intercellular communication. In general, there are two types of vesicle:
microvesicles (100nm – 1 µm in diameter) which directly bud from
the plasma membrane and nanovesicles (exosomes 30nm - 100nm) 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.
Continuing, Sargent said: “NanoSight’s NTA technique is a major
step forward in analytical capability taking the limits of flow cytometry down
almost an order of magnitude. It is rapid and, in common with flow cytometry,
characterizes polydispersity well.”
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 mis-reporting renders it of little value. It is also not able
to make concentration measurement.
Jeremy Warren, NanoSight CEO, commented “The work of this important group
is a significant milestone for us. It is the first step toward directing NanoSight’s
capability as a platform for biomarker detection”.
In the closing session, Dr Karl Morten, also from University of Oxford, described
NanoSight’s useful role in rapidly assessing newly developed nanoparticles,
as he summarised a range of roles of nanotechnology in drug delivery.
This conference bought together 135 delegates in this rapidly growing area
of interest. There were five groups from the UK, Netherlands and USA who have
recently added NanoSight’s NTA to their characterisation capability.