Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
2001-04-11
2003-06-03
Nguyen, Nam (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S278000, C204S292000, C204S293000, C252S500000, C252S062200
Reexamination Certificate
active
06572740
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to an improved electrolytic cell having novel electrolytes and/or novel electrode materials. The electrolytic cell can be used as a gas generator for a drug delivery device.
BACKGROUND OF THE INVENTION
There are many applications requiring the dispensing or delivering of a liquid at a predetermined or precisely controlled rate. One application requiring a particularly precise rate of delivery is a system for administering a drug, such as insulin or morphine. Precise pumps have been devised for this purpose. However, such pumps are expensive to produce and maintain, and are inconvenient to refill with the periodic dosage requirements.
One solution to this problem is to use an electrolytic cell as a gas generator which functions to dispense a liquid from a device. For example, U.S. Pat. No. 5,062,834 (“the '834 patent”), for “Device for Dispensing a Liquid Particularly Useful for Delivering Medicaments at a Predetermined Rate,” describes a device for dispensing a liquid at a predetermined rate. The device comprises a container for the liquid to be dispensed and a piston assembly movable within the container and dividing the container into two expandable-contractible chambers. The first chamber contains the liquid to be dispensed and the second chamber contains pressurized gas which functions to dispense the liquid from the first chamber of the container. The second expandable-contractible chamber includes an electrolytic cell having electrodes and an electrolyte. Upon energization of the cell, the electrolyte conducts current between the electrodes, triggering the generation of gas.
The electrolytic cell of the '834 patent comprises a pair of electrodes and an electrolyte capable of generating a gas upon energization of the electrodes. The gas expands the second chamber which results in displacing a piston, thereby forcing the liquid out from the first chamber. Examples of useful electrolytes include saline solution and other polar solutions or gels which generate hydrogen, oxygen, nitrogen or carbon dioxide. A similar device containing an electrolytic cell is described in U.S. Pat. No. 5,242,406 for “Liquid Delivery Device Particularly Useful for Delivering Drugs.”
Another example of an electrolytic cell used in a drug delivery device is given in U.S. Pat. No. 5,090,963 for “Electrochemically Driven Metering Medicament Dispenser.” This patent describes a liquid material dispenser comprising an electrolytic cell capable of generating a gas when energized by a source of electric current. The liquid material dispenser comprises a rigid housing having a flexible partition forming two compartments. Upon energization by a source of electric current, the electrolytic cell in the first compartment generates a gas, thereby expanding the first compartment of the dispenser. This results in contracting the second compartment containing the liquid material, thereby dispensing the liquid material. The patent teaches that the electrolyte can be an 8% solution of sodium bicarbonate (NaHCO
3
) in water or a 4% solution of copper sulphate (CuSO
4
) in water.
Yet another example of a prior art use of an electrolytic cell in a drug delivery device is given in U.S. Pat. No. 5,186,805 (“the 805 patent”) for “Electrolytic Dispensing Device.” This patent describes a device similar to that the '834 patent. For this particular adaptation of an electrolytic cell, the electrodes are preferably stainless steel nets or screens. The electrolyte can be a water solution of various salts or acids, such as baking soda (sodium bicarbonate), caustic soda, magnesium sulphate, potassium sulphate, sodium sulphate, potassium nitrate, potassium bicarbonate, boric acid, acetic acid, formic acid, or carbonic acid. The '805 patent teaches that particularly good results were obtained using an 8% solution of baking soda (sodium bicarbonate) as an electrolyte.
Finally, a liquid material dispenser, in which the liquid is forced from the dispenser by a gas generated by an electrolytic cell, is described in U.S. Pat. No. 5,704,520. The electrolytic cell contains electrodes and electrolyte. Suitable electrolytes are disclosed to be sodium bicarbonate and potassium acetate.
While these prior art references describe useful electrolytic cells, there remains a need in the art for improved electrolytic cells useful in drug delivery devices. In particular, there is a need for electrolytic cells having a more constant rate of gas production and electrolytic cells having a controlled variable rate of gas production. The present invention satisfies these needs.
SUMMARY OF THE INVENTION
The present invention is directed to an improved electrolytic cell having a new electrolyte and/or a new electrode composition for water electrolysis or other type of electrochemical reaction. The invention also encompasses pre-treatment protocols for electrodes which produce a more efficient electrolytic cell. The electrolytic cell is useful as a gas generator in a drug delivery device.
The improved cell allows for miniaturization of the electrolytic cell and any device incorporating such a cell. The novel electrolytic cell is one of the smallest electrolytic cells comprising a liquid electrolyte. The miniaturization or micronization is possible because the cell delivers a large amount of gas volume as compared to the size and quantity of components. The miniaturized electrolytic cell can be used in human applications, such as for administering drugs to be applied either externally or internally. In addition to being useful on a small scale, the electrolytic cell of the invention can be scaled-up and used in commercial manufacturing settings.
In a first embodiment, the improved electrolytic cell exhibits a constant rate of gas production over a prolonged period of time. For this type of cell, the anode must be insoluble in an anodic dissolution process, which is an electrochemical reaction (this is distinguishable from chemical or other types of dissolution); the cathode can be chosen from a wide variety of materials. Steady state production over an extended period of time, as shown below, is highly desirable as such a constant rate produces a constant rate of drug delivery when the electrolytic cell is employed in a drug delivery device.
In a second embodiment, the electrolytic cell can be designed to have a controlled variable rate of gas production, as shown below. For this type of cell, the anode is soluble, such as brass or copper. Such a variable rate is desirable for certain types of applications, such as delivering pain medication, in which it is preferred that an initial high delivery rate is followed by a lower constant rate.
In a third embodiment, the electrolytic cell is designed to have an pulsatile rate of gas production, as shown below. For this type of cell, the anode is insoluble material in an anodic dissolution process, which is an electrochemical reaction (this is distinguishable from chemical or other types of dissolution); the cathode can be chosen from a wide variety of materials. Such an intermittent rate of gas production is useful for certain types of applications, such as for irrigation systems, for the addition of fertility materials to irrigation water, and for administering insulin or hormones to mammals.
An electrolytic cell of the invention is dramatically superior to prior art cells in that it is simple and cost effective to manufacture, it is composed of materials that are safe and non-toxic, and it can be used in a variety of applications. For example, an electrolytic cell according to the invention can be used in a drug delivery device to administer a steady and controlled amount of drug over an extended period of time. Alternatively, the an electrolytic cell according to the invention can be used to administer a high amount of medication immediately following use, followed by a lower steady rate of administration, or the electrolytic cell can be used to administer a drug at intermittent periods of time.
A. New Electrolyte
The new electroly
Lavi Gilad
Rosenblum Maya
Yigal Gil
Caesar Rivise Bernstein Cohen & Pokotilow Ltd.
Elan Pharma International Limited
Nguyen Nam
Nicolas Wesley A.
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