Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving virus or bacteriophage
Reexamination Certificate
1999-12-17
2002-06-04
Chin, Christopher L. (Department: 1641)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving virus or bacteriophage
C385S012000, C385S129000, C385S130000, C385S131000, C356S305000, C356S317000, C356S318000, C356S340000, C422S082110, C435S006120, C435S007100, C435S007200, C435S007310, C435S007320, C435S007340, C435S007370, C435S287100, C435S287200, C435S288700, C435S808000, C436S164000, C436S165000, C436S518000, C436S524000, C436S525000, C436S527000, C436S805000
Reexamination Certificate
active
06399295
ABSTRACT:
TECHNICAL FIELD
The present invention is generally in the field of detecting analytes in a medium and, more particularly, the present invention relates to the methods of making optical diffraction-based sensors which are capable of indicating the presence of the analyte in a medium.
BACKGROUND OF THE INVENTION
There are many systems and devices available for detecting a wide variety of analytes in various media. Most of these systems and devices are relatively expensive and require a trained technician to perform the test. There are many cases where it would be advantageous to be able to rapidly and inexpensively determine if an analyte were present. What is needed is a biosensor system that is easy and inexpensive to manufacture and is capable of reliable and sensitive detection of analytes, including smaller analytes.
Sandstrom et al., 24
Applied Optics
472, 1985, describe use of an optical substrate of silicon with a layer of silicon monoxide and a layer of silicon formed as dielectric films. They indicate that a change in film thickness changes the properties of the optical substrate to produce different colors related to the thickness of the film. The thickness of the film is related to the color observed and a film provided on top of an optical substrate may produce a visible color change. The authors indicate that a mathematical model can be used to quantitate the color change, and that “[c]alculations performed using the computer model show that very little can be gained in optical performance from using a multilayer structure . . . but a biolayer on the surface changes the reflection of such structures very little since the optical properties are determined mainly by the interfaces inside the multilayer structure. The most sensitive system for detection of biolayers is a single layer coating, while in most other applications performance can be by additional dielectric layers.”
Sandstrom et al., go on to indicate that slides formed from metal oxides on metal have certain drawbacks, and that the presence of metal ions can also be harmful in many biochemical applications. They indicate that the ideal top dielectric film is a 2-3 nm thickness of silicon dioxide which is formed spontaneously when silicon monoxide layer is deposited in ambient atmosphere, and that a 70-95 nm layer silicon dioxide on a 40-60 nm layer of silicon monoxide can be used on a glass or plastic substrate. They also describe formation of a wedge of silicon monoxide by selective etching of the silicon monoxide, treatment of the silicon dioxide surface with dichlorodimethylsilane, and application of a biolayer of antigen and antibody. From this wedge construction they were able to determine film thickness with an ellipsometer, and note that the “maximum contrast was found in the region about 65 nm where the interference color changed from purple to blue.” They indicate that the sensitivity of such a system is high enough for the detection of protein antigen by immobilized antibodies. They conclude “the designs given are sensitive enough for a wide range of applications. The materials, i.e., glass, silicon, and silicon oxides, are chemically inert and do not affect the biochemical reaction studied. Using the computations above it is possible to design slides that are optimized for different applications. The slides can be manufactured and their quality ensured by industrial methods, and two designs are now commercially available.
U.S. Pat. No. 5,512,131 issued to Kumar et al. describes a device that includes a polymer substrate having a metal coating. An analyte-specific receptor layer is stamped on the coated substrate. The device is used in a process for stamping or as a switch. A diffraction pattern is generated when an analyte binds to the device. A visualization device, such as a spectrometer, is then used to determine the presence of the diffraction pattern.
However, the device described by Kumar et al. has several disadvantages. One disadvantage is that an extra visualization device is needed to view any diffraction pattern. By requiring a visualization device, the Kumar et al. device does not allow a large number of samples to be tested since it is not possible to determine the presence of an analyte by using the unaided eye. Additionally, this device is not able to detect smaller analytes as these analytes do not produce a noticeable diffraction pattern.
U.S. Pat. No. 5,482,830 to Bogart, et al., describes a device that includes a substrate which has an optically active surface exhibiting a first color in response to light impinging thereon. This first color is defined as a spectral distribution of the emanating light. The substrate also exhibits a second color which is different from the first color (by having a combination of wavelengths of light which differ from that combination present in the first color, or having a different spectral distribution, or by having an intensity of one or more of those wavelengths different from those present in the first color). The second color is exhibited in response to the same light when the analyte is present on the surface. The change from one color to another can be measured either by use of an instrument, or by eye. Such sensitive detection is an advance over the devices described by Sandstrom and Nygren, supra, and allow use of the devices in commercially viable and competitive manner.
However, the method and device described in the Bogart, et al. patent has several disadvantages. One disadvantage is the high cost of the device. Another problem with the device is the difficulty in controlling the various layers that are placed on the wafer so that one obtains a reliable reading.
Additionally, biosensors having a self-assembling monolayer have been used to detect analytes and are set forth in U.S. patent application Ser. Nos. 08/768,449 and 08/991,844, both of which are incorporated herein by reference in their entirety. However, these biosensors currently do not have the requisite sensitivity required to detect smaller analytes since these smaller analytes do not produce a sufficient diffraction pattern to be visible.
Some commercial lateral flow technologies have been used which employ latex bead technology. These technologies are currently employed in most of the commercially-available home diagnostic kits (e.g. pregnancy and ovulation kits). These kits use colored beads which accumulate in a defined “capture zone” until the amount of beads becomes visible to the unaided eye. However, these systems lack the requisite sensitivity to test for many analytes, since a much larger number of latex beads must bind in the capture zone to be visible to the naked eye than that required to cause diffraction in the same size zone. Theoretically, the number of beads needed is about 2 to 3 orders of magnitude higher than the sensors of the present invention.
Biosensors having a self-assembling monolayer and using microparticle technology have been used to detect smaller analytes and are set forth in U.S. patent application Ser. No. 09/210,016, which is incorporated herein by reference in its entirety. However, these biosensors require multiple process steps to produce, thereby increasing the difficulty and cost for using these types of sensors.
What is needed is a biosensor system that is easy and inexpensive to manufacture and is capable of reliable and sensitive detection of analytes, including smaller analytes.
SUMMARY OF THE INVENTION
The present invention provides an inexpensive and sensitive system and method for detecting analytes present in a medium. The invention provides a new approach to reduce the number of steps involved by a user of diffraction diagnostic devices using “diffraction enhancing elements,” such as microparticles. The approach involves the use of a wicking agent that is used to remove unbound labeled microparticles, as well as any residual liquid from the sample. The wicking agent then avoids the necessity of any additional rinsing, which may be cumbersome or more difficult for a user. Additionally, a small hole (e.g., {fra
Chidebelu-Eze Chibueze Obinna
Choi Abraham B.
Grunze Michael Heinrich Herbert
Kaylor Rosann M.
Chin Christopher L.
Kilpatrick & Stockton LLP
Kimberly--Clark Worldwide, Inc.
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