Chemistry: analytical and immunological testing – Measurement of electrical or magnetic property or thermal...
Reexamination Certificate
1998-05-04
2001-04-24
Soderquist, Arlen (Department: 1743)
Chemistry: analytical and immunological testing
Measurement of electrical or magnetic property or thermal...
C436S151000, C436S183000, C436S139000, C436S140000, C422S082010
Reexamination Certificate
active
06221673
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the detection or quantitation of a chemical species in a target environment, and the discovery that the properties of certain particles which are interactive with the chemical species can advantageously be monitored as a indication or in which amount the species is present.
BACKGROUND OF THE INVENTION
There are a number of known approaches to determining the presence or amount of a chemical species in a target environment by exposing a substance capable of interacting with the species to such environment and monitoring a change in a property of the substance due to such interaction as an indication of whether or in what amount the species is present.
One such approach has been the exposure to the environment of a species-interactive substance applied to a piezoelectric substrate. The substance is affected such that, if any of the species present, a preselected property of the substance is changed. A surface acoustic wave is induced in the piezoelectric material. Any change of property in the substance results in an attenuation of the surface acoustic wave, which can be monitored as an indication of whether or in what amount the species is present. For instance, see U.S. Pat. Nos. 4,312,228 and 4,759,210.
Another approach has been the provision of a capacitive device for detecting the presence or measuring the concentration of an analyte in a fluid medium. A plurality of interdigitated fingers formed from metallic conductors are placed upon an insulating substrate. The substrate may be made from an insulating material such as glass and the fingers may be made of copper and gold; the fingers are covered with an insulating passivation layer. The approach involves biospecific binding between a biochemical binding system and the analyte to change the dielectric properties of the sensor. See U.S. Pat. No. 4,822,566.
Yet another approach has been the provision of a chemical sensor comprising a thin film of dithiolene transition metal complexes applied to a chemiresistor device. The film is deposited upon an interdigitated electrode on a substrate. The film changes conductivity when exposed to a chemical gas or vapor of analytical interest. The interdigitated electrodes may be gold and the substrate is an insulating material such as quartz. A power supply and current measuring device are included. See U.S. Pat. No. 4,992,244.
Still another approach has been provision of a biosensor in the nature of a sample testing device that includes an electrode structure which makes measurements of one or more electrically measurable characteristics of the sample. The area between two electrodes on one wall of the test cell can be coated with a binding agent which can bind conducting particles such as gold sol particles. See U.S. Pat. No. 5,141,868.
A different type of biosensor which has also been suggested has a thin crystalline drive surfactant polymeric electrically conducting layer to which may be bound members of specific binding pairs. Binding of an analyte or reagent to the binding pair member layer may change electrical properties of the layer for measurement of the analyte. See U.S. Pat. No. 5,156,810.
However, it would still be desirable for the art to have an alternative detection technology which lends itself to ready and versatile implementation as well as consumes power at a very low level, without sacrificing reliability, miniaturization affinity, and low cost.
OBJECTS OF THE INVENTION
It is an object of the invention to provide sensitive and reliable technology for the detection and monitoring of chemical species.
It is another object of the invention to provide materials, methods and equipment suitable for the sensitive and reliable detection or quantitation of a preselected chemical species in a target environment.
It is yet another object of the invention to provide materials, methods and equipment as aforesaid which are well-suited for applications requiring compact size, low cost and low power consumption.
It is a further object of the invention to provide methods of fabricating the aforementioned equipment.
SUMMARY OF THE INVENTION
In one aspect, the invention is in an article of manufacture suitable for use in determining whether or in what amount a chemical species is present in a target environment, which article comprises a multiplicity of particles in close-packed orientation, said particles having a core of conductive metal or conductive metal alloy, in each said particle such core being of 0.8 to 40.0 nm in maximum dimension, and on said core a ligand shell, of thickness from 0.4 to 4.0 nm, which is capable of interacting with said species such that a property of said multiplicity of particles is altered.
In a further aspect, the invention is in a method of investigating a target environment to determine whether or in what amount a chemical species may be present, which comprises: (a) exposing to said environment an article of manufacture comprising a multiplicity of particles in close-packed orientation, said particles having a core of conductive metal or conductive metal alloy and deposited thereon a ligand which is capable of interacting with said species such that a property of said multiplicity of particles is altered; (b) subjecting said multiplicity of particles to conditions sufficient for said property to be exhibited; and (c) monitoring said property to determine whether there is, or the amount of, any change as an indication of whether, or in what amount, said species is present.
In another aspect, the invention is in an assembly suitable for investigation of a target environment to determine whether or in what amount a chemical species may be present, which comprises: (a) a substrate suitably configured for presenting a multiplicity of particles supported thereon to contact with said environment; (b) supported by said substrate, a multiplicity of particles in close-packed orientation, said particles having a core of conductive metal or conductive metal alloy and deposited thereon a ligand which is capable of interacting with said species such that a property of said multiplicity of particles is altered; and (c) a sensor for monitoring said property of said multiplicity of particles.
In yet another aspect the invention is in a method of fabricating an assembly suitable for investigation of a target environment to determine whether or in what amount a chemical species may be present, which comprises depositing on a substrate (i) a pair of interdigitated electrodes each having a comb-like configuration and (ii) in such manner that the electrodes are electrically connected, a thin film of a multiplicity of particles having a core of conductive metal or conductive metal alloy, in each said particle the core being from 0.8 to 40.0 nm in maximum dimension, and deposited on said core a ligand shell, of thickness from 0.4 to 4.0 nm, which is capable of interacting with said species such that a property of said multiplicity of particles is altered.
In still a further aspect the invention in a system suitable for investigating a target environment to determine whether or in what amount a chemical species may be present, which comprises: (a) a multiplicity of particles in close-packed orientation, said particles having a core of conductive metal or conductive metal alloy and deposited thereon a ligand which is capable of interacting with said species such that a property of said multiplicity of particles is altered; (b) means for exposing said multiplicity of particles to said environment; (c) means for subjecting said multiplicity of particles to conditions sufficient for said property to be exhibited; and (d) means for monitoring said property to determine whether there is, or the amount of, any change in such property as an indication of whether or in what amount said species is present.
By the term “close-packed orientation” herein we mean a solid-state arrangement of nanoscale metal particles as aforesaid, wherein ligand shells are in contact with their nearest neighbors and in which multimolecular sized (for examp
Snow Arthur W.
Wohltjen Henry
MicroSensor Systems Inc.
Soderquist Arlen
Whitman Breed Abbott & Morgan LLP
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