Awesome new voltage-sensitive dye
New genetically encoded fluorescent voltage-sensitive dye.
Sensitivity: up to 34% change (delta F/F) per 100 mV.
Time constant: .5 ms.
Phototoxicity: You can expose the cells to light for up to 100 seconds without much effect; over 200 seconds is noticably damaging.
Location: specific to cell membranes.
Not ratiometric (if you don’t know what that is, don’t worry about it).
Excerpt from figure caption: “(c) Confocal section of HEK293 cells expressing eGFP-F shows very little fluorescence from internal membranes. Scale bar, 20 mum. (d) Fluorescence response (shown as colored increments) of hVOS on voltage pulses from -120 to +120 mV in steps of 20 mV from a holding potential of 0 mV in patch-clamped HEK293 cells.”
Baron Chanda, Rikard Blunck, Leonardo C Faria, Felix E Schweizer, Istvan Mody and Francisco Bezanilla. A hybrid approach to measuring electrical activity in genetically specified neurons. Nature Neuroscience 8, 1619 - 1626 (2005)
August 16th, 2007 at 3:18 pm
I am interested in developing a microelectron device in which such a voltage sensitive dye might be separated from an aggegrate of cells by a distance of the order of 5-30 nm. Thus, the dye would not be in contact with the cell. Am I correct in assuming that if the dye receives a voltage of the order of 50-100 mV, it will fluoresce? Is this concept of interest?
Thanks,
Ted Morse
Boston Unviersity
August 18th, 2007 at 2:16 am
Last time I checked, HEK293 cells don’t carry action potentials and you don’t find them in brains. It’s not so hard to get a beautiful signal-to-noise ratio in a culture dish. One small step for cell sorting, but not necessarily any big whup for in situ or otherwise in vivo study of brains.
August 18th, 2007 at 4:23 pm
> It’s not so hard to get a beautiful signal-to-noise ratio in a culture dish.
well actually it is pretty hard :). at least when it comes to VSDs.
anyway, even though it’s not brain cells, it’s a start. now people can start to do it in neurons (or at least they could if a commercial supplier of dipicrylamine was available — i tried to get my hands on some about a year ago and couldn’t find any). i don’t know much about it, but I think people do HEK293 first because they’re easy to transfect.