Calibrating and normalizing an imager for optogenetics
The present invention includes methods and systems for optical assays, such as optogenetic assays, of biological activity in which an optical reference signal is used to normalize an optical test signal.
1. A method for assaying biological activity, the method comprising:
providing a sample comprising cells including optical reporters of cellular activity wherein the cells are in a well of a multi-well plate;
positioning the multi-well plate on a plate reader comprising a plurality of optical channels corresponding to a respective plurality of wells of the multi-well plate, wherein each optical channel is operable to provide to one well of the plurality of wells excitation and stimulation light of different wavelengths and to simultaneously read optical signals of different wavelengths from the one well;
stimulating, via one optical channel of the plurality of optical channels, the sample with a reference stimulus;
detecting by the one optical channel an optical signal produced in response to the reference stimulus;
exposing the sample to test conditions modeling a biological and/or chemical stimulus of the cellular activity;
detecting by the one optical channel an optical signal produced in response to the test conditions; and
calibrating the test signal to the reference signal to predict a level of activity of the cells in response to the modeled biological and/or chemical stimulus.
2. The method of claim 1 , wherein the optical reporters are fluorescent reporters of membrane electrical potential.
3. The method of claim 1 , wherein the cellular activity is caused by neurons.
4. The method of claim 3 , wherein the cells include optical actuators of electrical activity.
5. The method of claim 4 , wherein the optical actuators of electrical activity include one or more light-gated ion channels.
6. The method of claim 5 , wherein the light-gated ion channels include one or more algal channelrhodopsins.
7. The method of claim 6 , wherein the reference stimulus is blue light transmitted to the cells.
8. The method of claim 7 , wherein the test conditions include synaptic transmission by pre-synaptic neurons connected to the cells via synapses.
9. The method of claim 1 , wherein the calibrating step corrects for inherent variability across a plurality of assays.
10. The method of claim 1 , wherein the sample is a multi-well plate and a plurality of wells of the plate comprise the cells comprising optical reporters of cellular activity.
11. The method of claim 10 , wherein the stimulating step comprises transmitting the reference stimulus to the cells in a plurality of the wells.
12. The method of claim 11 , wherein the stimulating step comprises transmitting the reference stimulus to every well of the multi-well plate.
13. The method of claim 11 , wherein detecting the optical signal produced in response to the test conditions comprises simultaneously detecting an optical test signal from each of the plurality of wells.
14. The method of claim 13 , wherein the optical test signal from each of the plurality of wells is detected by a different detection module of a plate reading device.
15. The method of claim 14 , wherein the optical reporters are fluorescent reporters of membrane electrical potential.
16. The method of claim 15 , wherein the cells are neurons.
17. The method of claim 16 , wherein the cells include optical actuators of electrical activity.
18. The method of claim 17 , wherein the optical actuators of electrical activity include one or more light-gated ion channels.
19. The method of claim 17 , wherein the light-gated ion channels include one or more algal channelrhodopsins.