Apparatus and method for electrically contacting biological cells suspended in a liquid
An apparatus for electrically contacting biological cells suspended in a liquid has a substrate having at least one opening and an electrode for electrically contacting a cell immobilized above the opening. A contact unit with a contact tip is arranged below said opening. A top end of the contact tip projects into the opening in such a way that it comes to bear against a cell membrane of the immobilized cell. The contact tip has a contact channel which ends at its top end. A hydrodynamic low pressure can be exerted upon the cell membrane via the contact channel, and the electrode is electrically connected to the contact channel. In a method for electrically contacting biological cells suspended in a liquid, a cell is immobilized above an opening provided in a substrate, and the immobilized cell is contacted via at least one electrode. For contacting the immobilized cell, a hydrodynamic low pressure is generated acting on a cell membrane through a contact tip projecting into the opening.
1. An apparatus for electrically contacting biological cells suspended in a liquid, said apparatus comprising:
a substrate having at least one opening,
a suction channel ending in said opening, said suction channel being adapted to provide a first hydrodynamic low pressure at the opening for immobilizing a cell having a cell membrane on top of said opening,
a contact unit being arranged below the opening and comprising a contact tip, and
at least one electrode for electrically contacting the cell when it is immobilized on top of said opening,
wherein the contact tip comprises a top end projecting into said opening in such a way that said contact tip comes to bear against the cell membrane when the cell is immobilized on top of said opening, and further comprises a contact channel which opens at the top end in such a way that a second hydro-dynamic low pressure can be exerted upon the cell membrane, and
wherein the electrode is arranged within said contact channel, and
wherein the contact unit has a replaceable top part comprising the contact tip and a reusable bottom part comprising the electrode and a first section of the contact channel,
wherein the top part further comprises an annular recess formed around the contact tip and facing the substrate, with the annular recess having a passage connected to the suction channel.
2. The apparatus of claim 1 , wherein the annular recess is covered by a membrane having a gap which surrounds the contact tip at a distance.
3. The apparatus of claim 2 , wherein the membrane is fixed to the top part.
4. The apparatus of claim 1 , further comprising a reference electrode projecting into the liquid in the vicinity of the opening.
5. The apparatus of claim 1 , further comprising a functional coating provided on the substrate around the opening for immobilizing the cells on said opening.
6. The apparatus of claim 5 , wherein the functional coating is selected from the group of: polyanions, polycations, polyethyleneimine, antibodies against cell surface molecules, and magnetic coating.
7. The apparatus of claim 1 , further comprising a positioning unit for positioning a cell above the opening.
8. The apparatus of claim 7 , wherein the positioning unit comprises one of the following: laser tweezers, a means for building up an electromagnetic field, or a means for generating a hydrodynamic force.
9. The apparatus of claim 1 , further comprising a flow channel adapted to direct the liquid to the opening with a predefined transport flow.
10. The apparatus of claim 9 , further comprising a microperfusion unit connected to the flow channel upstream of the opening for applying test substances to an immobilized cell.