© Imperial College LondonPage 1 Detecting gold nanoparticles in electron microscope images John...

© Imperial College London

Detecting gold nanoparticles in electron

microscope images

John Cupitt, Exp. Med. & Tox.

16 November 2009


Technique

Use gold nanoparticles to label receptors, signalling proteins and lipids

Use up to three particle sizes to label different features

Image sections of cell membrane with transmission electron microscopy

Particle positions reveal information about membrane function


TEM imaging of cell membrane fragments

Then fix lightly, label with gold particles, fix securely, stain, dry and image with TEM


Problem

Gold nanoparticles are in the 3 – 15nm range, as few as 100 atoms

Image sections of cell membrane ~2000nm across containing several hundred particles

Particles therefore appear rather small: 4 - 12 pixels across

Standard blob detectors are designed for larger features and have poor accuracy at this scale

Only 50% accuracy with most systems


Characteristics

Approximately Gaussian profile7 – 13 pixels acrossApproximately circularAmong the darkest objects in the image


Our new detector

Gaussian ring divided into octants, convolve with each octant, take minimum response, compare to centre average


Results

On the test image, with a little tuning, we get 99+% accuracySearching the whole 2,500 x 2,500 pixel image takes about 2 secondsNeed to test on more images, add some better tuning


Credits

Nicolas Robidoux, Department of Mathematics and Computer Science, Laurentian University, designed the detector with help from Chantal Racette, an undergraduate studentThe NIH/NIGMS Center for the Spatiotemporal Modeling of Cell Signaling provided images and the gold standard, as well as funding for Chantal Racette's work.

© Imperial College LondonPage 1 Detecting gold nanoparticles in electron microscope images John...

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