Electromicroinjection of particles into living cells

A method for introducing individual particles suspended in an electrically conducting aqueous solution into recipient biological cells. the method comprising the steps of:

• attracting at least one of the individual particles to the tip of a micropipette for piercing the membrane of a target recipient cell and located in the conducting aqueous solution containing the target recipient cells by applying a first voltage between the tip of the micropipette and the conducting aqueous solution:
• inserting the micropipette tip into a target recipient cell, the at least one particle remaining attached thereto during said insertion step;
• and
• releasing the at least one particle from the tip of the micropipette by applying a second voltage between the tip of the micropipette and the conducting aqueous solution. the second voltage having a polarity opposite to that of the first voltage.

An apparatus for introducing individual particles suspended in an electrically conducting aqueous solution into recipient biological cells, the apparatus comprising in combination:

• an injection micropipette having an exit orifice size for piercing the membrane of a target recipient cell, the outside surface of said injection micropipette having a conducting material thereon in the region of the exit orifice;
• first electrode means for providing electrical contact with the conducting material at a location away from the exit orifice;
• second electrode means located in the electrically conducting aqueous solution containing the recipient biological cells;
• and
• means for providing a first voltage and a second voltage between said first electrode means and said second electrode means both when the exit orifice of said injection micropipette is located in the conducting aqueous solution and when the exit orifice of said injection micropipette is located within the body of a recipient cell located in the conducting aqueous solution, the first voltage having a chosen magnitude and polarity for electrostatically attracting at least one particle to the region of the exit orifice of said injection micropipette, and for holding the particle in this location during the process of piercing the membrane of a cell with the exit orifice of said injection micropipette and insertion of the particle into the recipient cell body, and the second voltage having a polarity opposite to that of the first voltage and a chosen magnitude for electrostatically repelling the particle away from the injection micropipette.

An apparatus for introducing individual particles suspended in an electrically conducting aqueous solution into recipient biological cells. the apparatus comprising in combination:

• a conducting microneedle having a tip size for piercing the membrane of a target recipient cell;
• electrode means located in the electrically conducting aqueous solution containing the recipient biological cells;
• and
• means for providing a first voltage and a second voltage between the tip of said conducting microneedle and said electrode means both when the tip of said conducting microneedle is located in the conducting aqueous solution and when the tip of said conducting microneedle is located within the body of a recipient cell located in the conducting aqueous solution, the first voltage having a chosen magnitude and polarity for electrostatically attracting at least one particle to the region of the exit orifice of said injection micropipette, and for holding the particle in this location during the process of piercing the membrane of a cell with the tip of said conducting microneedle and insertion of the particle into the recipient cell body, and the second voltage having a polarity opposite to that of the first voltage and a chosen magnitude for electrostatically repelling the particle away from the conducting microneedle.