AU624340B2 - Electrochemical contact lens disinfection and neutralization system - Google Patents

Description

AU-AI-23133/88 WORLD INTELLECTUAL PROPEiTY ORGANIZATION International Bureau

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INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 4 A61L 2/18, C25F 1/00 G01N 33/483 (11 rn nal /blic on N! ber WO 89/ 00430 (43) Internai onal Pbli on Dai: anuary 1989 (26.01.89) (21) International Application Number: PCT/US88/02376 (22) International Filing Date: (31) Priority Application Numbers: 13 July 1988 (13.07.88) 074,703 117,922 (81) Designated States: AT (European patent), AU, BE (European patent), BR, CH (European patent), DE (European patent), DK, FI, FR (European patent), GB (European patent), IT (European patent), JP, LU (European patent), NL (European patent), NO, SE (European patent).

Published With international search report.

Before the expiration of the time limitfor amending the claims and to be republished in the event of the receipt (32) Priority Dates: (33) Priority Country: 17 July 1987 (17.07.87) 4 November 1987 (04.11.87) (71)tSETION 34(4)(a) DIRECTION SEE FOLIO_ 1 NME DIRECTED t 1o rr L-PP-c 1 ATOA Ies A bqo H Pb k lI no s b o o- Lf -3c du s 40 I de cl (74) A-gent'iIAND EBAU M,.Hiowaro,-r. r Basseches Mandelbaum, 420 Lexington Avenue, New York, NY 10170 (US).

A-O. J. P. 6 APR 1989,1 I AUSTRALIAN I 3 FE51939 (54) Title: ELECTROCHEMICAL CONTACT LENS DISINFECTION AND NEU 1 (57) Abstract A method and apparatus generates superoxides for cleaning and sterilizing contact lenses in an electrolytic solution which optionally includes an antiseptic, such as hydrogen peroxide. The apparatus includes a container in the form of a lens case containing water and/or a disinfectant solution in two chambers in which each one of a pair of contact lensis is immersed. The lens case can be made of nonconductive materials such as glass, most rigid or semirigid plastics, or any other material which is not significantly chemically reactive with hydrogen peroxide or free radicals generated in the disinfecting process. The lens case is provided with circular covers which can be threaded onto the lens case to seal the corresponding circular chambers thereby preventing leakage of the solution j Background of the Invention This invention relates to a method of sterilizing a contaminated article.

The invention is particularly applicable and will hereinafter be described for convenience with respect to sterilizing contact lens or the like.

Contact lenses, and porous soft -ontact lenses in particular, must be periodically disinfected to control growth of bacteria on their surfaces which, if left unchecked,. could infect the eyes of the wearer. Ordinarily, the lenses are removed each evening before the wearer retires to sleep and are then reinserted into the eyes upon awakening. This provides an opportunity to disinfect the lenses by their placement in an antiseptic solution, typically one containing chemicals such as hydrogen peroxide although other disinfectants such as sorbic acid may also be used.

The hydrogen peroxide solution is an eye irritant. Hence, any latent trace of the peroxide solution that remains on the lens surface or is absorbed into a 1~porous lens is likely to cause the wearer extreme discomfort, if not pain. It is therefore necessary to remove or neutralize any residual peroxide in the contact lenses. Other chemical disinfectants are also irritating in varying degrees.

Since hydrogen peroxide is relatively unstable and decomposes into water and oxygen, allowing the solution to stand, exposed to atmospheric conditions at 26 ambient temperatures, will eventually result in neutralization of the solution.

However, the time necessary for effective neutralization to occur is typically on the ordei- of several days. The prospect of being unable to use contact lenses for several days presents the user with an intolerable situation.

:It is known in the prior art to neutralize the disinfectant peroxide solution through the use of chemical additives. See, U.S. Patent No.

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0 1 2 WO 89/00430 PCT/US88/02376 4,568,517 to Kaspar et al. which discloses a contact lens disinfecting system wherein a chemical neutralizer, e.g. sodium sulfite or sodium thiosulfate is added to the disinfecting solution and U.S. Patent No.

4,521,375 to Houlsby for Sterilizing Treatment with Hydrogen Peroxide and Neutralization of Residual Amounts Thereof which discloses a contact lens disinfecting system wherein a chemical neutralizer consisting of sodium pyruvate is used. However, these result in the solution, and lenses, being left with other undesirable byproducts of the chemical neutralization.

A more effective solution to the neutralization problem has been found in the use of one or more catalysts to enhance the decomposition of a hydrogen peroxide solution. The use of catalytic agents to accelerate the neutralization of a hydrogen peroxide solution absorbed by contact lenses in the course of sterilization is disclosed in U.S. Patent No. 3,912,451 to Gaglia, Jr. for a Method for Removing Hydrogen Peroxide from Soft Contact Lenses. Although Gaglia's method represents an improvement over some prior methods, specifically the ambient decomposition method, in that it substantially shortens the decomposition time, it still takes at least six hours to reduce the percentage of peroxide to an acceptable level for contact lens wear.

Another method for disinfecting contact lenses, disclosed in U.S. patent No. 4,202,740 to Stoner et al., uses electrically charged ions as the disinfectant. In this method the case holding the contact lenses must be made of a conducting material to serve as a bipolar system whereby the ions flowing through the electrolyte decontaminate the contact lens.

If there is an uneven current distribution shadows result and the disinfection is incomplete. For proper operation of the latter electrolysis method, the voltages must be kept below the potential at which electrolytic oxygen and chloride from the HO and NaCl 2

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<V WO 89/00430 3 PCT/US88/02376 are generated, otherwise oxidation of the case material, which is conductive, will occur and cause uneven current distribution.

Summary of the Invention The instant invention overcomes the aforementioned problems of the prior art in substantially lessening the time for effective cleaning and sterilization of contact lenses and neutralization of the disinfectant solution through the use of electrolysis. The use of hydrogen peroxide and free radical electrolysis for sterilization in a contact lens disinfecting environment according to the instant invention should not be confused with the use of electrolysis with ion current for sterilization of contact lenses per se without a disinfectant solution as disclosed in U.S.

Patent No. 4,202,740 to Stoner et al. for Apparatus and Method for Disinfecting Objects.

Electrolysis can also achieve disinfection by the generation of certain free radicals such as H and 0 2 2 and pH changes when the electrolyte used in the solution is more stable than the water molecule and when the electrolyte itself generates additional free radicals that are not destructive to the material to be disinfected. Therefore in the electrolytic system of the instant invention the amount of H 0 can be reduced 22 below the standard three percent used in solutions typical of the prior art. If the H 0 were completely 2 2 removed from the electrolytic solution sterilization would still occur but would take a somewhat longer period of time. Without H 2 2 the disinfection rate can be increased with increased current. The generated free radicals and pH changes can, in addition to disinfection, be used to neutralize other agents such as cleaning enzymes and soaps added to the electrolyte.

More specifically, the instant inv.e tion provides q /iol r iri.l% conM-fed aartcl pe 0 lenses, tonometers, plastic medical equipment and other

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poorly oxidizing objects by immersion in a solution with hydrogen peroxide, followed by subjecting the solution to electrolysis to rapidly decompose the hydrogen peroxide and at the same time generate free radicals so that together the effectiveness of the disinfection is increased and at the end of the process render the solution neutral so that it is compatible with the natural liquid secretions on the eye, thereby permitting the user to wear the lenses without undue delay.

Thus the method of the invention comprises a method of sterilizing a contaminated article comprising immersing said article in a disinfectant hydrogen peroxide solution for a time sufficient to allow disinfection thereof, and causing an electric current to flow through said solution between at least two electrodes in contact therewith for a time sufficient to neutralize said disinfectant solution.

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0005 00 0 0* ?,A4/ lull T k"1- Ok[ Description of the Drawings Fig. 1 is a perspective view of part of an apparatus that can be used in the method of the invention.

Fig. 2(a) is an elevation view of the apparatus of Fig. 1 installed in an environment including additional apparatus that can be used in the method of the invention.

Fig. 2(b) is a plan view of the apparatus of Fig. 2(a).

Fig. 3 is a flow diagram for the method of a preferred embodiment of the invention.

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5. S S S 0* 6 s RA~( -1 U -,VlV u ~NT 0 WO 89/00430 PCT/US88/02376 Fig. 4 is a schematic circuit diaaram of part of the apparatus 4 -of pro err od:ombodirnnt of the invention.

Description of the Preferred Embodiment Referring now to the drawings, there is shown a container in the form of a lens case 1 containing water and/or a disinfectant solution 3 in two chambers 4 in which each one of a pair of contact lenses 5 is immersed. The lens case 1 can be made of nonconductive materials such as glass, most rigid or semi-rigid plastics, or any other material which is not significantly chemically reactive with hydrogen peroxide -r fr cradicalc gonoratod in the disinfecting process. The lens case 1 is provided with circular covers 2 which can be threaded onto the the lens case 1 to seal the corresponding circular chambers 4 thereby preventing leakage of the solution 3.

Typically the solution 3 will be water containing from zero to three percent hydrogen peroxide and a small amount, 102 milimoles of sodium sulfate, Na SO or 153 milimoles of calcium sulfate, 2 4 Ca SO or potassium bromide (KBr), sodium bromide 2 4 (NaBr), sodium iodide (Nal), or a similar salt to render the solution conductive in order to enhance the electrolysis process. Phosphate buffers, NaH PO Na HPO 4 or Na PO may be added to maintain pH constant 2 4 3 4 when necessary. Other phosphated buffers wherein metals from classes IA or IIA of the periodic table of elements are substituted for sodium can be used. Salts such as sodium chloride NaC1 and potassium chloride KC1 which break down into gaseous components, i.e., chlorine, have been found less desirable -or physiologic conditions in that the gaseous byproducts can evaporate leaving hydroxyl ions which can form strong bases such as sodium hydroxide and potassium hydroxide which- can chemically damage or destroy contact lenses. When physiologic conditions are not K1 1) :v'x~As :win~_ L _I WO 89/00430 -7- PCT/US88/02376 requ.red, small amounts of NaCl can be added to Na SO 2 4 to cause generation of chlorine and hydroxides both of which are strong disinfectants. Metals from classes IA and IIA of the periodic table of the elements can be substituted for sodium in the various sodium containing salts herein.

The salt is added in sufficient amounts to buffer the solution to a pH rendering it nearly isotonic with the tears secreted about the eyes. The major salt used should have the property of resistance to disintegration in the electrolytic system while small amounts of other salts such as NaCl and the water and hydrogen peroxide are broken down into free radicals.

Mounted adjacent the bottom of the lens case 1 is a pair of elongated thin wire electrodes including an anode 9 and a cathode 11. Electrically connected to the ends of the anode 9 and cathode 11, respectively, are a positive conductor 13 and a negative conductor 15. The electrodes 9 and 11 are preferably made of a metal alloy or other conducting material which is not readily oxidized, e.g. platinum, rhodium, iridium, carbon, platinum rhodium alloy or platinum iridium alloy. For electrode stability an alloy is the preferred choice as pure elements tend to have weaker bonds and degrade more rapidly under high current densities.

While some of the suitable materials may also have a catalytic effect on neutralizing the peroxide solution when used in sufficient quantity as taught by Gaglia, the size of the electrodes, typically about 0.5mm diameter by 20mm length is such as to make the amount of electrode material much less than the catalytic amount needed for any material increase in the decomposition of the peroxide by catalytic action.

Absent the electrolysis process taught herein, the insertion of the electrodes in the sterilizing solution would provide no material advantage over merely allowing the peroxide to normally decompose under ambient conditions.

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i' ij WO 89/00430 PCT/US88/02376 Also mounted on the bottom of the lens case 1 is an integral array of spacers 12, projecting upwardly from the bottom interior surface of the lens case 1, on which the lenses are supported to permit the solution 3 to flow between the bottom surface and lenses so that the lenses are surrounded on all sides by the disinfectant solution 3. The lens case covers 2 are provided with openings 6 to permit oxygen to escape.

Optionally, an oxygen permeable liquid tight seal may be disposed within the openings in the covers 2 to further ensure against leakage of the disinfectant solution as will be known to those skilled in the art.

Where no hydrogen peroxide i used and the din ±ay period is kept short, the ne-d-r he openings 6 may 1 td.

A source 17 of electrical potential which serves as a power supply provides the energy for rapid decomposition of the sterilization solution 3. The source 17 may be A.C. or D.C. In the preferred embodiment of tho invention the source 17 is a conventional storage battery with a D.C. potential of between and 20 volts, high enough to generate free radicals. A power source 17 capable of generating square waves having peaks of sufficient amplitude to generate free radicals is alternatively preferred. A timing and control unit 14 is provided for carrying out the lens cleaning, sterilization and disinfectant neutralization processes of the invention in accordance with the flow diagram of Fig. 3. The construction and operation of the timing and control unit is described with reference to Fig. 4.

The timing and control unit 14 governs three process time periods. During the first period, the lenses are placed in a salt solution as previously described which may contain cleaning agents, e.g.

including one or more enzyme ingredients and/or soaps, and or an antiseptic, hydrogen peroxide. During the first time period, the cleaning agents, soaps or

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WO 89/00430 9 PCT/US88/02376 enzymes, if present, remove contaminants from the lenses and the antiseptic, if present, kills infectious microerganisms.

During the second time period, electric current is applied to the solution. The current is at a level in the rang of 5 to 300 milliamperes, sufficient to cause the generation of free radicals of hydrogen and oxygen as well as pH change from Na SO electrolysis, all of 2 4 whiuh have an antiseptic effect and sanitize the lenses, even in the absence of an antiseptic additive.

The electrolysis, disinfects by pH changes as well as free radical formation and also neutralizes any residual hydrogen peroxide, and any enzymes or soaps added, thereby leaving a weak salt solution having a 13 tonicity near the tonicity of the natural fluids surrounding the eyes. The first few seconds following the current interruption are included in the second period. It is during this time that the free radicals dissipate and the pH returns to the physiologic range.

The third time period follows the interruption of the electrolysis current following the disinfection of the lenses and neutralization of the solution 3. It is during the third time period that the cleaned, sterilized and neutralized lenses may be removed from the timing and control unit 14.

A pair of electrodes 16 and 18 project upwardly from a planar mounting surface 20 on the timing and control unit 14 for contacting the conductors 13 and respectively on the lens case i. Electrode 18 is grounded while electrode 16 is normally maintained at the positive battery voltage to which it is connected through a resistor 20 which in the preferred embodiment f tho inCntion has a resistance of approximately 1 megohm. When the electrodes 16 and 18 make contact with the conductors 13 and 15 which are bridged by the ionized solution 3, a current path is completed between the electrodes 16 and 18.

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0 WO 89/00430 1 0 PCT/US88/02376 Upon completion of the current path between the electrodes 16 and 18, the input to an inverter 22 is brought to ground potential, The low signal input to inverter 22 results in a high signal at the output of the inverter 22 which sets a flip-flop 24. The flipf lop 24 is a type 4013 CMOS. The resultant high signal at the Q output of flip-flop 24 feeds NAND gate 30. The other input of NAND gate 30 is connected to the output of an inverter 44. When both inputs of NAND gate 30 are high, the lens case 1 is in the timing and control unit 14 and the cleaning process has not yet been completed, the output of NAND gate 30 is low. This signal is applied to an inverter buffer 32 and enables an eight bit counter 26, which can be a type 4520 CMOS integrated circuit, to begin counting pulses applied by a type 555 integrated circuit timer 28 which in the preferred embodiment -f the invention generates one pulse approximately every ten seconds. Inverter 44 indicates the status of the eighth bit Q7 of the counter 26, whether the cleaning process is completed as will be later explained.

The inverter buffer 32, which can be a 4049 CMOS integrated circuit, is connected to the anode of a red light emitting diode 34 having a cathode connected to ground through a resistor 35. This causes ay the L.E.D. 34 to light while the cleaning and, where- anantiseptic hydrogen peroxide is used, partial disinfection of the lenses takes place.

After a predetermined time, dictated by the frequency of the timer 28, the seventh bit Q6 of the eight bit counter 26 goes high marking the completion of the cleaning portion of the process. The high output at the seventh bit of counter 26 sets a flip-flop 36 which can also be a type 4013 CMOS. This causes the Q output of flip-flop 36 to go low, and the output of an inverter buffer 38 which is connected to the base of transistor 40 to go high, thereby turning on transistor to begin the generation of the free radicals as well -p- 9, 4

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C TJ WO 89/00430 1 PCT/US88/02376 as neutralizing the hydrogen peroxide (H 2 02) and/or any added soaps or enzymes.

When transistor 40 is turned on, battery current flows through the ionized salt-containing sterilization solution 3 while the counter 26 continues to count the pulses from timer 28. It has been found that the electrolysis current should preferably be in the range of 2-120 milliamperes per cubic centimeter of solution.

In the preferred embodiment -f th invcnticn, wherein each of the chambers 4 is filled with approximately c.c. of solution, the total electrolysis current to generate the radicals in the solution 3 in both chambers 4 is approximately 10-600 milliamperes. The current flow also causes the peroxide, if any is present, to be reduced to water and free oxygen in accordance with the following relationship.

HO HO 0 2 2 2 2 Also, free hydrogen and oxygen radicals are generated in accordance with HO H O and H 0 H O 22 2 2 2 2 2 Also, basic and acidic ions are generated in accordance with: Na SO 2(Na+OH-) H+ SO 2 4 2 4 2NaCl 2Na+OH- 2H+C1- 2Na+OH- H Cl 2 2 This electrolysis procedure by which the solution 3 creates the free radicals and also neutralizes the disinfectant solution continues for a predetermined time until the eighth bit Q of the counter 26 goes high. The output of the eighth bit of the counter 26 is connected to the clock inputs of the flip-flops 24 and 36. Hence, when the output of the eighth bit of the counter 26 goes high, after the disinfection with the free radicals that were generated by electrolysis of the solution 3 has been completed, the low state at the grounded D input to each of the flip-flops 24 and 36 is loaded into the respective Q outputs. The low A signal at the Q output of flip-flop 24 turns off the 7 1 WO 89/00430 1 2 PCT/US88/02376 red L.E.D. 34 and disables the counter 26. The high signal at the Q output of flip-flop 36 turns off transistor 40 thereby halting the electrolysis current flow.

The output of the eighth bit of the counter 26 is connected to the inverter buffer 44, which can be a 4049 CMOS integrated circuit. Inverter buffer 44 is connected to inverter buffer 61 which is, in turn, connected to the anode of a green light emitting diode 46 having a cathode connected to ground through a resistor 45. This causes the green L.E.D. 46 to light after the sterilization by radicals with or without peroxide and the neutralization by electrolysis of the solution 3 has been completed, thereby signaling the user to remove the lens case 1 from the timing and control unit 14. The cleaned, sterilized and neutralized lenses can then be removed from the lens case 1 and safely inserted into the eyes. Removal of the lens caso 1 causes the flip-flops 24 and 36 to be reset at which time the counter 26 is initialized and the L.E.D.s 34 and 46 are turned off.

The timing and control unit 14 is automatically initialized either when the lens case 1 is removed from the timing and control unit 14 or system battery power is removed and then reapplied. The reset logic for initializing the system is provided by NAND gates 48 and A NAND gate 42 has its respective inputs connected to the output Q of flip-flop 36 and to the electrode 16 for generating a low output signal when the transistor 40 is off and the case 1 is out of the timing and control unit 14. Capacitor 56 and diode 58 prevent sudden changes in the voltage at the input of NAND gate 42 which could upset the sequence for reinitializing the system.

The low signal from NAND gate 42 is then applied to NAND gate 48. NAND gate 48 has its other input connected to capacitor 54 and resistor 60. When power

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-WO 89/00430 1 3 PCT/US88/02376 is reapplied after being off, the capacitor 54 is charged through resistor 60 and provides a low signal pulse. The low signal pulse is applied to the other input of NAND gate 48. This low signal pulse causes a reset signal to be generated whenever power is restored after being interrupted.

The output of NAND gate 48 is inverted by inverter 62. Operational amplifier 31 has its respective inputs connected to the electrode 16 and to a voltage divider formed by resistors 63 and 64. The values of the resistors 63 and 64 are such that the voltage at the node between them is lower than the voltage at electrode 16 when transistor 40 is on and the case 1 is out of the timing and control unit 14 and higher than the voltage at electrode 16 during any other condition, the operational amplifier 31 yields a low logic output when transistor 40 is on and the ca-e 1 is taken out of the timing and control unit 14.

NAND gate 50 has its respective inputs connected to the output of inverter 62 and to the output of operational amplifier 31. A high signal output from NAND gate 50 is used to reset counter 26 and flip-flops 24 and 36 when the case 1 is removed from the timing and control unit 14 while transistor 40 is off, or the case 1 is removed from the timing and control unit 14 while transistor 40 is on, or power is restored after being interrupted.

The reset signal from the output of NAND gate is applied to the reset inputs of flip-flops 24 and 36 and turns off the red L.E.D. 34 and 46 if either was previously lit.

In use, the container 1 is partially filled with a sterilizing solution of water (H20), hydrogen peroxide

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2 0 2 and salt (Na 2 S04, CaSO 4 NaBr, KBr, NaI, KI, phosphate buffer or other organic salts that ionize but are otherwise stable at the applied potential) in the above stated relative quantities. When the contact lens wearer retires to bed, or at any other time when it is i WO 89/00430 -1 PCT/US88/02376 desired to clean and sterilize the lenses, they are inserted into the solution 3 in the lens case 1 which is inserted into the timing and control unit 14 and left there a sufficient time for cleaning, sterilization and neutralization to be achieved, as indicated by the lit red and green L.E.D.s.

The resultant solution is a dilute saline having a tonicity and pH like that of the tears. Hence, to the extent that the solution is absorbed into or remains on the surface of the contact lenses after their removal from the lens case or container 1, it causes no discomfort to the wearer after insertion into the eyes.

Ultrasonic cleaners m be used in conjunction {roerrrewl elye4 W, with the apparatust-e-'the invention.

It is to be appreciated that the foregoing is a description of a preferred embodiment of the invention to which variations and modifications may be made without departing from the spirit and scope of the invention. Moreover, the invention is not limited to sterilizing contact lenses and may apply to the disinfection of any article or object which can be cleaned and sterilized by electrolysis. Additionally, the apparatuc and method c-n be used for the treatment of diseased tissue. The application of free radical containing solution is believed to be able to dec'troy or, at least, retard the growth of infectious viruses and bacteria in living tissue. The apparatus herein described can be used for tissue treatment. It can also be used in the experimental evaluation of the destructive effects of superoxides on the heart muscle and cataracts. In vitro studies can be done using the apparatus to generate free radicals, such as superoxides, in solutions, inserting the tissue into the solution, and observing the effects of the free radicals, superoxides, on the tissue.

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Claims (5)

1. A method of sterilizing a contaminated article comprising immersing said article in a disinfectant hydrogen peroxide solution for a time sufficient to allow disinfection thereof, and causing an electric current to flow through said solution between at least two electrodes in contact therewith for a time sufficient to neutralize said disinfectant solution.

2. A method for sterilizing a contaminated article according to claim 1 wherein said solution contains an ionized salt.

3. A method of sterilizing a contaminated article according to claim 2 wherein said salt is stable under electrolysis.

4. A method of sterilizing a contaminated article according to claim 3 :wherein said salt is selected from thke group consisting of sodium sulfate, phosphate buffer, potassium bromide, sodium bromide, potassium iodide and 1. sodiumiode A method of sterilizing a contaminated article according to claim 1 wherein said current is maintained in the range of 2 to 120 milliamperes per cubic centimeter of solution.

6. A method of sterilizing a contaminated article according to claim 1, substantially as hereindescribed with reference to the accompanying drawings. DATED this 25 day of March 1992. ABBOTT LABORATORIES By their Patent Attorneys: CALLINAN LAWEE ,A L 1 M''V OA K4