Method and apparatus for measuring biological activity with single cell resolution
A method and apparatus for carrying out measurements on single cells, either one or many single cells at a time in order to characterize the cellular response to stimuli in a perfused liquid. The apparatus for performing the respirometry includes a double-barrel pipette probe.
1. A method of perfusing a single cell with a liquid and measuring the single cell's effect on the liquid using a double barrel pipette probe ( 1 ) comprising a pipette shaft body ( 2 ) having a distal end ( 5 ), wherein the pipette shaft body ( 2 ) comprises a channel A ( 6 ) and a channel B ( 7 )), wherein channel A ( 6 ) is configured for guiding a liquid out of the distal end ( 5 ) of the pipette shaft body ( 2 ) and channel B ( 7 ) is configured to receive the liquid exiting channel A ( 6 ) at the distal end ( 5 ) of the pipette shaft body ( 2 ), wherein said channel B ( 7 ) comprises or is in fluid connection with a sensor module for measuring concentration of material in the liquid or a temperature of the liquid,
said method comprising steps of:
positioning said distal end ( 5 ) of the pipette shaft body ( 2 ) in proximity to said single cell,
flowing the liquid having a baseline concentration of material or baseline temperature from channel A ( 6 ) to channel B ( 7 ) at the distal end ( 5 ) of pipette shaft body ( 2 ) while perfusing said single cell with the liquid exiting channel A ( 6 ),
measuring the concentration of the material in the liquid or the temperature of the liquid with the sensor module in channel B ( 7 ), and
comparing the baseline concentration of material or baseline temperature with the concentration of material or the temperature of the liquid as measured by the sensor module to determine an effect of said single cell on the concentration or temperature value.
2. The method according to claim 1 , wherein a separator wall ( 3 ) connects opposite sides of an inner wall ( 4 ) of the pipette shaft body ( 2 ) and said separator wall ( 3 ) is formed in a plane bisecting a lumen of the pipette shaft body ( 2 ) in a longitudinal direction, said separator wall ( 3 ) separates the pipette shaft body ( 2 ) into said two channels A ( 6 ) and B ( 7 ) in a manner whereby channel A ( 6 ) is parallel to channel B ( 7 ) and, in said method, a direction of flow of liquid within channel A ( 6 ) is opposite a direction of flow of liquid within channel B ( 7 ).
3. The method according to claim 1 , wherein the pipette shaft body ( 2 ) has a conical tip portion narrowing at the distal end ( 5 ) of the pipette shaft body ( 2 ) and the distal end ( 5 ) of the pipette shaft body ( 2 ) has a diameter of from about 100 nm to about 100 microns.
4. The method according to claim 1 , wherein the single cell is one cell in a tissue sample ( 9 ) containing other cells.
5. The method according to claim 4 , wherein the double barrel pipette probe ( 1 ) is a first pipette probe and said method further comprises a step of perfusing a second single cell with a liquid using a second double barrel pipette probe located in proximity to a second single cell in the tissue sample, determining a baseline concentration of a material in the liquid in channel B of the second pipette probe, adding a modulator to the liquid in channel A of the first pipette probe, and measuring for variations of said concentration of the material in the liquid in channel B of the second pipette probe.
6. The method according to claim 4 , wherein a single cell on the surface of the tissue is exposed to a modulator at a baseline concentration and/or for a duration and the depth of response within the tissue cells is measured, subsequently the single cell on the surface of the tissue is exposed to a modulator at an increased concentration and/or for an increased duration and the depth of response within the tissue cells is measured.
7. The method according to claim 1 , wherein the material comprises oxygen and the liquid further comprises a respiration modulator.
8. The method according to claim 7 , wherein the respiration modulator is at least one selected from the group consisting of a metabolite, a mitochondrial electron transport inhibitor, a chemotherapeutic agent, and a compound which affects extracellular pH.
9. The method according to claim 1 , wherein the material is at least one of oxygen, an alkali metal cation, an alkaline earth metal cation and a halide.
10. The method according to claim 1 , wherein the flow of liquid from channel A ( 6 ) to channel B ( 7 ) is maintained for at least 10 minutes.
11. The method according to claim 1 , wherein the cell is an animal cell.
12. The method according to claim 1 , wherein a wall of channel B ( 7 ) and a wall of channel A ( 6 ) have a carbon coating.
13. The method according to claim 1 , wherein the sensor module is a coating ( 41 ) capable of providing a fluorescent response in the presence of at least one of glucose, lactose, protein, carbon dioxide, sodium, chlorine, potassium, iron, magnesium and calcium.
14. The method according to claim 13 , wherein a microscope objective ( 42 ) is positioned below a substrate ( 43 ) holding the single cell or tissue containing the single cell so as to receive a light signal through the substrate.
15. The method according to claim 1 , wherein the sensor module is an oxygen sensor ( 8 ) or a plasma discharge wire ( 50 ).
16. The method according to claim 1 , wherein channel A ( 6 ) comprises a sensor module.