There has been quite move in the past 6-12 months to produce a commercially viable super resolution light microscopy system. Breaking the inherent resolution limits of light microscopy is quite a challenge and a number of approaches have been used - check out the Wikipedia entry http://en.wikipedia.org/wiki/Microscopy#Sub-diffraction_techniques for a nice summary of the approaches used. Remember earlier in the year Zeiss launched their super resolution ELYRA system at Liverpool.
Last week we went to Milton Keynes to have a look at Leica's offering for super resolution, their development of the STED system originally designed by Steffan Hell at the Max Plank http://www.mpibpc.mpg.de/groups/hell. Essentially this system utilises a second laser which acts to deplete the spread of light as it enters the microscope thus reducing the lateral resolution to <75nm. Originally this was a limited technology from a commercial point of view as only a handful of fluorescent dyes were suitable and would involve a redesigned experimental approach. Now however dyes such as Alexa 488 and YFP can be used which makes it more user friendly. Multicolour imaging is still limited however as the use of red dyes is not possible due to the depletion laser being at 594nm. I'm sure this will be resolved soon.
The demonstration data sets were pretty impresive with a full width half maximum (FWHM) of approx 50-75nm. I hope I can post some of the images from the workshop on here soon once the appropriate permissions have been granted.
One major drawback of this technology is its application to live cell imaging. Amazingly to get rapid depletion of the flurophore one has to run the laser at a phenominal 70mW!! This will basically fry any viable samples and has quite an amazing effect on some green flurophores with unbelievable levels of photobleaching, I think with Cy2 dyes.
A footnote here, I think at the moment super resolution imaging is promising but from a facility point of view has a great deal of development needs. I think the largest contribution will be the development of new flurophores that are either more photostable under such high laser powers or can be depleted with different laser sources that allow multicolour imaging to be performed. Its far from optimal just yet! With all these different approaches I'm sure the requesite information is currently available but we maybe need to pull it all together to make a viable system.
In addition to this Leica showed us their super zoom confocal for imaging large speciemens such as embryos and plants. They also had their high content screening system based on the SP5, this was particularly interesting. Finally we saw their TIRF microscopy. All in all a very good day, well organised with interesting talks and as usual excellent back up knowledge from the Leica staff. Hopefully, images to follow!
I'll have to check now that the resolution obtained on our confocals is the best it can be -- I have already ordered some sub-defraction beads to do this and will tackle it after my holidays ;-)
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