Method and apparatus for measuring changes in cell volume
A method and apparatus for measuring changes in cell volume generally includes introducing cells into a chamber having a volume between 2 and 100 times the volume of the introduced cell. A first electrically conductive extracellular fluid is introduced into the chamber and a current is applied. The voltage induced by said current flow is measured. The first fluid is exchanged with a second electrically conductive extracellular fluid and a current is applied. The voltage induced by said current flow is measured. The first induced voltage result and the second induced voltage result are used in conjunction with known voltages induced by such current flows to monitor changes in the volume corresponding to fluid flow between the cell and an extracellular fluid.
1. A method of measuring change in cell volume comprising:
introducing cells into a first chamber defined by a first pair of electrodes for measuring voltage drop across said first chamber, wherein a first chamber volume of said first chamber is between 2 and 100 times a cell volume of said cells;
introducing a first electrically conductive extracellular fluid into said first chamber;
applying a current through said first chamber;
measuring voltage drop across said first chamber to obtain a first voltage drop result corresponding to said first electrically conductive extracellular fluid;
exchanging the first electrically conductive extracellular fluid in said first chamber with a second electrically conductive extracellular fluid;
applying a current through said first chamber;
measuring voltage drop across said first chamber to obtain a second voltage drop result corresponding to said second electrically conductive extracellular fluid;
using said first voltage drop result and said second voltage drop result in conjunction with known voltage drops across said first chamber for the first and second electrically conductive extracellular fluids, respectively, absent impedance to current flow attributable to said cells, to monitor changes in said cell volume, said changes in said cell volume are calculated according to:
Δ
V
V
=
Δ
R
R
SC
×
1
R
RC
R
0
-
1
;
wherein V 0 is a volume of said cells after introducing said first electrically conductive extracellular fluid into said first chamber,
V is a volume of said cells after stimulation by exchanging the first electrically conductive extracellular fluid with the second electrically conductive extracellular fluid,
ΔV=V−V 0 ,
Δ
V
V
is
a
relative
cell
volume
change
,
R 0 is a first resistance correlated to the known voltage drop across said first chamber for said first electrically conductive extracellular fluid,
R RC is a second resistance correlated to the first voltage drop result,
R SC is a third resistance correlated to the second voltage drop result, and
ΔR is R SC −R RC .
2. The method of claim 1 wherein said cells are adhered within said first chamber.
3. The method of claim 1 wherein a height of said first chamber is less than 100 micrometers.
4. The method of claim 1 wherein a height of said first chamber is less than 5 micrometers.
5. The method of claim 1 further comprising:
introducing said first electrically conductive extracellular fluid into a second chamber void of said cells, said second chamber defined by a second pair of electrodes for measuring voltage drop across said second chamber;
applying a current through said second chamber;
measuring voltage drop across said second chamber to obtain a third voltage drop result corresponding to said first electrically conductive extracellular fluid;
exchanging said first electrically conductive extracellular fluid in said second chamber with said second electrically conductive extracellular fluid;
applying a current through said second chamber; and,
measuring voltage drop across said second chamber to obtain a fourth voltage drop result corresponding to said second electrically conductive extracellular fluid.
6. The method of claim 5 wherein said first and second chambers are arranged in parallel relationship such that the introduction of at least one of said first and second electrically conductive extracellular fluids therein occurs concurrently.
7. The method of claim 1 further comprising a second pair of electrodes adapted for applying said current through said first chamber, said first pair of electrodes disposed between said second pair of electrodes.
8. The method of claim 7 wherein a distance between said first pair of electrodes is variable.
9. The method of claim 7 wherein a distance between said second pair of electrodes is variable.