The UK's national metrology institute, the National Physical Laboratory (NPL),
is commencing a one-year evaluation program of NanoSight's
nanoparticle characterization technology, Nanoparticle Tracking Analysis (NTA).
The program takes the form of a Joint Industry Project, funded in part by government.
The initial objective is a validation of NTA and comparison with existing nanoparticle
sizing techniques and standards.
Dr Alex Cuenat, NPL’s Nanomaterials Group Leader, reports: “What
differentiates NanoSight from existing light scattering techniques is that it
provides a direct view of the sample under analysis and rapid quantitative estimation
of the sample size, size distribution and concentration.
“No method is truly universal. Most ensemble measurements are made using
dynamic light scattering (DLS) or photon correlation spectroscopy (PCS). These
methods are very fast with thousands of particles analysed in a single second
but they cannot accurately analyze multi-modal (more than one size) dispersions
or follow changes during analysis.
“NanoSight’s Nanoparticle Tracking Analysis (NTA) differs in that
it measures particle speed compared to DLS which is measuring intensity of light
scattered. This unique real-time capability to follow the Brownian motion of
individual nano-particles, leads to advantages over DLS. These include avoidance
of a bias towards larger particles, which is driven by the latter’s dependence
on scatter intensity; an estimate of concentration which NanoSight provides;
and a unique image validating the results and providing additional insight.
“We first saw a NanoSight prototype in 2005 and recognised how, with
development, the technique had potential to fill gaps in characterization methodologies
of sub-micron dispersions. Since then, we have seen this technique develop well,
so, although we do not know yet how this will result, we are enthusiastic about
running an in-depth validation. This investigation will look at precision and
accuracy and assess the validity of the algorithms used in NTA in some depth.”
Dr Patrick Hole, Development Manager at NanoSight comments: “During the
past four years, we have seen nanoparticle size and size distribution at the
top of the list of characterization requirements for those assessing the toxicology
of engineered nanoparticles. We are already working with a number of researchers
in this field. Before accepting NTA, they will usually compare NanoSight to
DLS/PCS or electron microscopy to see what additional information can be obtained
on their own samples.
“With more than 150 users worldwide, we have seen many successful comparative
tests, but in this project with NPL, we have third party scrutiny from an internationally
respected expert group. Consequently, this project is a significant step towards
gaining technical acceptance, as well as a chance for us to improve NTA with
expert input from Dr Cuenat’s team.”
One such advocate of the technique is Professor Kenneth Dawson, at UCD in Ireland
who states: “We have evaluated NanoSight for evaluating nanoparticle dispersions
for nanosafety and find it uniquely useful in assessing dispersion quality.
The rigorous approach taken by NPL in verification of this will be very welcome.”
Another NanoSight user, Dr Rob Aitken, Director of SAFENANO says: “Improved
characterization in the field of nanotoxicology is a critical requirement, and
NanoSight has demonstrated significant potential in filling the gaps not covered
by other techniques”.