Using an Andor Technology Electron Multiplying CCD (EMCCD) camera in combination with an imaging spectrograph and a sheath flow cuvette, researchers at the La Jolla Bioengineering Institute in California, have been able to analyse individual metal nanoparticles at rates of 100 per second or faster. This new capability will remove current bottlenecks associated with characterizing single nanoparticles, potentially leading to the development of brighter and more uniform tags for use in biomolecular detection and cancer therapeutics.
Exploiting the unique structure-dependent optical properties of metal nanoparticles depends on controlling particle size and shape, and this is limited not only by synthetic and assembly approaches, but also on the ability to efficiently measure nanoparticle optical properties. Ensemble (or bulk) characterization techniques are simple and fast, but do not directly reveal information about sample heterogeneity. Single nanoparticle analysis techniques based on microscopic imaging reveal heterogeneity, but are slow and labor intensive. The new approach developed by the team at La Jolla provides multiparameter optical measurements of thousands of individual nanoparticles in just a few minutes.
An Andor Newton EMCCD camera was used to collect Raman scattering spectra since it offers a combination of high detection efficiency, much lower noise, and far faster spectral acquisition rates than conventional CCDs, without any loss of data quality. In this case, the EMCCD is used to capture spectral data from individual surface enhanced resonant Raman (SERRS) nanoparticle tags with signal integration times of only 300µs.
The researchers are using this new technique to guide the development of brighter and more uniform SERRS tags, which have much narrower spectral features compared to fluorescence labels. This should enable more highly multiplexed measurements of cells and molecules than is currently possible with fluorescence flow cytometry.
According to Prof. John Nolan, who developed the technique with David Sebba and Dakota Watson at La Jolla, “This new approach exploits the advantages of both flow cytometry and EMCCD detection to create a powerful new way of characterizing metal nanoparticles, in our case SERRS tags. By removing single nanoparticle analysis bottlenecks, it should stimulate progress in many areas of nanoengineering.”
More information on the Andor Newton EMCCD camera is available at: www.andor.com/scientific_cameras/newton/
 High Throughput Single Nanoparticle Spectroscopy, David S. Sebba, Dakota A. Watson, John P. Nolan, ACS Nano Article ASAP DOI: 10.1021/nn9003346.