Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or...
Reexamination Certificate
1997-06-23
2001-11-13
Leary, Louise N. (Department: 1623)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
C435S007320, C435S007100, C435S007200, C435S018000, C435S029000, C435S034000, C435S039000, C424S001690, C549S034000
Reexamination Certificate
active
06316180
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed generally to analytical biochemistry. More specifically, the present invention is useful for monitoring chemical transformations of detectable compounds having a chemically-transformable first compound covalently linked to an electrochemiluminescent compound.
The present invention also relates to the development of an electrochemiluminescence (ECL) based assay for the detection and the quantitative measurement of &bgr;-lactams and &bgr;-lactamases which assay is suitable for the diagnosis and the monitoring of the treatment of bacterial infections.
BACKGROUND OF THE INVENTION
An ever-expanding field of applications exists for rapid, highly specific, sensitive, and accurate methods of detecting and quantifying chemical, biochemical, and biological substances, including enzymes such as may be found in biological samples. Because the amount of a particular analyte of interest such as an enzyme in a typical biological sample is often quite small, analytical biochemists are engaged in ongoing efforts to improve assay performance characteristics such as sensitivity.
One approach to improving assay sensitivity has involved amplifying the signal produced by a detectable label associated with the analyte of interest. In this regard, luminescent labels are of interest. Such labels are known which can be made to luminesce through photoluminescent, chemiluminescent, or electrochemiluminescent techniques. “Photoluminescence” is the process whereby a material luminesces subsequent to the absorption by that material of light (alternatively termed electromagnetic radiation or emr). Fluorescence and phosphorescence are two different types of photoluminescence. “Chemiluminescent” processes entail the creation of the luminescent species by a chemical reaction. “Electrochemiluminescence” is the process whereby a species luminesces upon the exposure of that species to electrochemical energy in an appropriate surrounding chemical environment.
The signal in each of these three luminescent techniques is capable of very effective amplification (i.e., high gain) through the use of known instruments (e.g., a photomultiplier tube or pmt) which can respond on an individual photon by photon basis. However, the manner in which the luminescent species is generated differs greatly among and between photoluminescent, chemiluminescent, and electrochemiluminescent processes. Moreover, these mechanistic differences account for the substantial advantages as an bioanalytical tool that electrochemiluminescence [hereinafter, sometimes “ECL”] enjoys vis a vis photoluminescence and chemiluminescence. Some of the advantages possible with electrochemiluminescence include: (1) simpler, less expensive instrumentation; (2) stable, nonhazardous labels; and (3) increased assay performance characteristics such as lower detection limits, higher signal to noise ratios, and lower background levels.
As stated above, in the context of bioanalytical chemistry measurement techniques, electrochemiluminescence enjoys significant advantages over both photoluminescence and chemiluminescence. Moreover, certain applications of ECL have been developed and reported in the literature. U.S. Pat. Nos. 5,147, 806; 5,068,808; 5,061,445; 5,296,191; 5,247,243; 5,221,605; 5,238,808, and 5,310,687, the disclosures of which are incorporated by reference, detail certain methods, apparatuses, chemical moieties, inventions, and associated advantages of ECL.
Copending and commonly-assigned U.S. patent application Ser. No. 08/368,429, filed January 4, 1995, the disclosure of which is incorporated by reference, details certain aspects of ECL in connection with beta-lactam and beta-lactamase (neither of which is conjugated through a covalent linkage to an electrochemiluminescent compound).
None of the above-identified documents disclose nor suggest the present invention. Additionally, the practice of the invention offers significant advantages to the skilled bioanalytical chemist in comparison to the electrochemiluminescent techniques taught by these documents. Accordingly, the invention meets the as-yet unmet needs of skilled workers with respect to the achievement of improved assay performance characteristics (e.g., signal output, detection limits, sensitivity, etc.) for the measured species and represents a patentable advance in the field.
Assays based on ECL are well known in the art and are finding expanding applications because of their accuracy, ease of use and freedom from radioactive materials.
A particularly useful ECL system is described in a paper by Yang et al,
Bio/Technology,
12, pp. 193-194 (Feb. 1994). See also a paper by Massey,
Biomedical Products
, October 1992 as well as U.S. Pat. Nos. 5,235,808 and 5,310,687, the contents of these papers and patents being incorporated herein by reference.
ECL processes have been demonstrated for many different molecules by several different mechanisms. In Blackburn et al (1991) Clin. Chem. 37/9, pp. 1534-1539, the authors used the ECL reaction of ruthenium (II) tris(bipyridyl), Ru(bpy)
3
+2
, with tripropylamine (TPA) (Leland et al (1990) J. Electrochem. Soc. 137:3127-31) to demonstrate the technique. Salts of Ru(bpy)
3
+2
are very stable, water-soluble compounds that can be chemically modified with reactive groups on one of the bipyridyl ligands to form activated species with which proteins, haptens, and nucleic acids are readily labeled. The activated form of the Ru(bpy)
3
+2
used by Blackburn et al was Ru(bpy)
3
+2
-NHS ester:
Beta-lactamases which hydrolyze the amide bonds of the &bgr;-lactam ring of sensitive penicillins and cephalosporins are widely distributed amongst microorganisms and play a role in microbial resistance to P-lactam antibiotics. Beta-lactamases constitute a group of related enzymes which are elaborated by a large number of bacterial species but not by mammalian tissues and can vary in substrate specificities. See generally Payne, D.J., J. Med. Micro (1993) 39, pp. 93-99: Coulton, S. & Francois, L., Prog. Med. Chem. (1994) 31, 297-349; Moellering, R.C., Jr., J. Antimicrob. Chemother. (1993) 31 (Suppl. A), pp. 1-8: and Neu, H.C., Science (1992) 257, pp. 1064-1072.
The detection of &bgr;-lactamase activity in a body fluid has long been considered to be indicative of a recent or current bacterial infection.
The developing microbial resistance to antibiotics such as penicillin and cephalosporin has been of concern for awhile. Recently, this concern has escalated in light of the dwindling number of new antibiotics and the over-use of those which are known. It is becoming more imperative to select the optimum antibiotic for treating a particular infection and to avoid prescribing the latest antibiotic when effective alternatives exist. This ability to select the optimum antibiotic is especially critical in those facilities involved in long-term care facilities where antibiotic resistance is increasingly becoming a problem. The lifetime of the current family of antibiotics can be prolonged by the selection of the optimum antibiotic. See generally Harold C. Neu, “The Crisis in Antibiotic Resistance”,
Science
Vol. 257 (Aug. 11, 1992) pp. 1064-1072.
The rising resistance to microbial resistance to antibiotics has heightened the need for a test which can rapidly measure quantitatively the degree of resistance to a particular &bgr;-lactam antibiotic such as a penicillin or a cephalosporin and then select the most appropriate antibiotic for a particular infective condition.
Several methods currently exist for the detection of microbial &bgr;-lactamases. Some representative examples follow.
W.L. Baker, “Co-existence of &bgr;-lactamase and penicillin acylase in bacteria: detection and quantitative determination of enzyme activities”,
J. Appl. Bacteriol.
(1992) Vol. 73, No. 1, pp. 14-22 discloses a copper-reducing assay for the detection of penicilloates and a fluorescamine assay to detect 6-aminopenicillanic acid concentrations when both substances were produced by the action of the enzymes on a sing
IGEN International Inc.
Leary Louise N.
Whitman Breed Abbott & Morgan LLP
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