Opinion ID: 1405856
Heading Depth: 1
Heading Rank: 3

Heading: Membraneless Sensor

Text: The claims of the '551 patent describe a test strip with an electrochemical sensor for testing whole blood without any membrane over the electrode. [3] Some sensors in the prior art had employed diffusion-limiting membranes to control the flow of glucose to the electrode because the slower mediators of the time could not deal with a rapid influx. Other prior art sensors employed protective membranes to prevent foulingwhen red blood cells stick to the active electrode and interfere with electron transfer to the electrode, resulting in an inaccurate measurement. In addition, sensors injected into the human body for in vivo measurements used protective membranes as a safety measure to prevent the chemistry from dissolving into the body and because fouling was a particular problem with respect to long-term in vivo implants. The central question with respect to obviousness is whether the prior art disclosed a glucose sensor without a membrane for use in whole blood. The district court found after trial that the prior art '382 patent disclosed electrochemical sensors in which a protective membrane was optional in all cases except the case of live blood, in which case the protective membrane was preferredbut not required. Trial Opinion, 565 F.Supp.2d at 1103. Whether the '382 patent disclosed a membraneless sensor is a question of fact which we review for clear error. See Graham v. John Deere Co., 383 U.S. 1, 17, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966). Initially filed in 1981 by one of Abbott's predecessors, the '382 patent represented an early achievement in the field of electrochemical sensors for measuring glucose levels. The '382 patent disclosed a faster-acting ferrocene mediator chemistry that allowed for better response times and quicker test results. The first two named inventors on the '382 patent are also the first two named on the '551 patent. At the outset, it is important to understand the scope and context of the '382 patent. The claims of a prior art patent are part of its disclosure. In re Benno, 768 F.2d 1340, 1346 (Fed.Cir.1985) ([I]t is true ... that `a claim is part of the disclosure'....); In re Smolak, 24 C.C.P.A. 1132, 88 F.2d 838, 841 (1937) ([T]he disclosures in [prior art] specifications... include the claims, the written specification, and the drawings. (quotation omitted)); see also Gabrielidis v. Prince Sports Group, Inc., Nos. 99-1469, 99-1490, 2000 WL 1648134, at  (Fed.Cir. Nov. 1, 2000). The claims of the '382 patent are plainly directed in part to sensors without a membrane, as is made clear by the dependent claims that specifically include a membrane as an additional feature of the device. For example, claim 1 claims a sensor electrode utilizing an enzyme and a ferrocene mediator for generating an electrical current representative of the level of a substance in a sample liquid, see '382 patent col. 10 ll.52-63, while dependent claim 12 adds an outermost protective membrane permeable to water and glucose molecules, said membrane covering said enzyme located upon said ferrocene layer, id. col.11 ll.29-32. One embodiment described in the patent involves a membraneless sensor for testing interstitial fluid, see id. col.3 l.53-col.4 l.2, and Example 8 of the patent specifically describes tests on strips using a buffer solution both with and without membranes, see id. col.9 ll.22-30. Abbott appears not to contest that the '382 patent broadly claims membraneless strips and that the specification discloses such membraneless strips. It contends, however, that in the case of bloodas opposed to other fluidsa membrane is required. In this respect it is significant that none of the claims in the '382 patent explicitly distinguishes between blood and other fluids. Also pertinent is the difference between in vivo sensors and in vitro sensors. In vivo sensors test live blood or other fluids inside the body, while in vitro sensors test fluids such as blood after they have been extracted from the body. Claims 1-17 of the '382 patent cover both in vivo and in vitro sensors; additional claims 18-19 are limited to in vivo sensors, though again those claims do not distinguish between sensors for blood and other fluids. Thus, as the district court found, the difficulty with Abbott's position that membranes are required for blood testing is that the claims covering membraneless sensors do not exclude blood and that other fluids are described as being tested by sensors without membranes. Most significantly, the specification addresses blood directly, stating that: Optionally, but preferably when being used on live blood, a protective membrane surrounds both the enzyme and the mediator layers, permeable to water and glucose molecules. Id. col.4 ll.63-66. On its face, the specification appears to contradict Abbott's position. It states that when testing with bloodblood in the body (i.e., in vivo testing)a protective membrane is preferred. The use of the term preferably implies that such a membrane is not necessary. See, e.g., Callaway Golf Co. v. Acushnet Co., 576 F.3d 1331, 1346-47 (Fed.Cir.2009) (holding that despite stating that the outer layers of a golf ball were preferably made of ionomer resins, the patent also disclosed the use of other materials such as polyurethane); Halliburton Energy Servs., Inc. v. M-I LLC, 514 F.3d 1244, 1251 (Fed.Cir.2008) ([T]he specification states that `preferably' none of these clays are added; this strongly suggests that absence of clays is simply a preferred embodiment.); Cordis Corp. v. Medtronic AVE, Inc., 339 F.3d 1352, 1357 (Fed.Cir. 2003) ([U]se of the term `preferably' makes clear that the language describes a preferred embodiment, not the invention as a whole.). Furthermore, when testing other sample typeswhich include whole blood outside the body, as well as blood plasma, interstitial fluid, and buffer solutionsthe protective membrane is optional, even more strongly confirming that it is not required for whole blood. The language of the patent thus confirms that a membrane is not necessary when testing live blood in vivo or whole blood in vitro. Abbott, however, contends that a person having ordinary skill in the art would not have read the '382 specification that way. Abbott asserts that the conventional wisdom of those skilled in the art was that a membrane was necessary when testing with blood, and that skilled artisans would not have read the patent's disclosure literally when it said that a membrane was not necessary with blood. Abbott may well be correct that for in vivo blood testingwhere the sensor is implanted in the body for up to a yeara membrane might sometimes be required for safety and for accurate measurement because of the risk of fouling over the long period of time that the sensor must operate. [4] The question, however, is whether a membrane was required for in vitro testing of whole blood where the blood stays on the sensor for, at most, a matter of minutes. Dr. Johnson, Abbott's expert, testified that one of ordinary skill in the art in 1983 would have thought that a membrane was required with blood with the '382 patent because of the risk of fouling. He did not specifically address the differences between in vivo and in vitro testing of blood. Bayer's expert witness, on the other hand, specifically addressed both types of testing, recognizing that for in vivo testing of blood a membrane might be necessary to ensure patient safety from the risk of chemicals escaping the sensor and entering the body, and to eliminate the problem of fouling that would occur as the sensor remained in the body for weeks or months. He testified that with in vitro testing a membrane was not necessary because there was no risk of chemicals entering the body and the time period involved in the testing was very short, particularly with respect to the faster chemistry claimed in the '382 patent. The district court plainly found the Abbott testimony not credible and credited the Bayer testimony, stating: Skilled artisans would have known that deleting the membrane would simply have deleted their mechanical advantages. They would have known, however, that the electrochemistry would still have worked. They would have known that the degree of fouling would have depended on how long the sensor was exposed to blood. They would have known that the risk of fouling would have been reduced for faster-acting chemistry and reduced even more for sensors used only once, i.e., disposable sensors with no accumulation of residue. They would have known that omitting the filter would have had the further advantage of speeding up the test time even more. Trial Opinion, 565 F.Supp.2d at 1101. The district court did not clearly err in crediting Bayer's expert testimony. Abbott also contends that another portion of the '382 patent's specification beyond the [o]ptionally, but preferably sentence demonstrates that a membrane is required when testing whole blood. Abbott in particular points to Example 8 of the patent. Abbott theorizes that the failure of Example 8 (listing test results for a buffer solution with and without a membrane and blood with a membrane) to mention whole blood testing without a membrane somehow demonstrates that whole blood testing required a membrane. We reject this argument. A single example testing whole blood with a membrane does not imply that membranes are required. In fact, there was testimony from Dr. Turner that Example 8's tests with the buffer solution demonstrated that the membraneless sensor would have worked with blood and provided a suggestion to do so, because the pH level of the buffer was apparently deliberately chosen in this example to match the pH of blood. The district court correctly found that Example 8 in the '382 patent [is] consistent with the plain meaning of [the `[o]ptionally, but preferably'] sentence. Trial Opinion, 565 F.Supp.2d at 1100. The court thus did not clearly err in finding that the '382 patent disclosed a membraneless sensor for whole blood testing. [5]