Noninvasive Transdermal Systems for Detecting an Analyte in a Biological Fluid and Methods

Abstract

The present invention relates to noninvasive transdermal systems comprised of a noninvasive transdermal patch and a reflectometer. The noninvasive transdermal patches are comprised of a wet chemistry component and a dry chemistry component. The wet chemistry component is a liquid transfer medium in the form of a gel layer for the extraction and liquid bridge transfer of the analyte of interest from the biological fluid within or beneath the skin to the dry chemistry component. The dry chemistry component is a reagent system for interacting with the analyte of interest (glucose) to generate a color change. The reflectometers include a modulated light source for emitting light to illuminate a target surface which possesses a certain color and shade of color for detection by an optical detector. The output signal is processed for determining a corresponding quantity of quality measurement.

Description

FIELD OF THE INVENTION[0001]The present invention concerns noninvasive transdermal systems and methods for analyte extraction from a biological fluid within or beneath the skin, such as interstitial fluid, and detection of the analyte. More particularly, the present invention relates to noninvasive transdermal systems comprised of a noninvasive patch and a reflectometer for detecting an analyte of interest and methods. The noninvasive patches include a wet chemistry component for extraction of the analyte of interest from a biological fluid within or beneath the skin and presentation to a dry chemistry component which interacts with the analyte for indicator molecule formation to confirm detection of the analyte, and methods of use thereof.[0002]The present invention also relates to reflectometer technology and, in particular, to a method and apparatus for detecting and measuring color shades with a relatively high degree of accuracy. Where the color shades are indicative of a certa...

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Benefits of technology

[0019]In brief, the present invention overcomes certain of the above-mentioned drawbacks and shortcomings through the discovery of a novel transdermal system for detecting an analyte of interest in a biological fluid and methods concerning same, without resort to prior standard invasive, painful techniques. In accordance with the present invention, the novel noninvasive transdermal systems provide for sample collection and detection in the form of a simple, easy-to-use, integrated system which is low-cost and suitable for convenient use by non-medical personnel. Moreover, because the novel transdermal systems of the present invention are noninvasive and painless, as compared to the invasive techniques generally utilized heretofore, e.g, a finger prick or finger lance, individual compliance should be enhanced, and the risk of disease transmission and infection should be reduced.

[0020]With the foregoing in mind and other objects in view, there is provided, in accordance with the present invention, a noninvasive transdermal system for collecting and detecting an analyte of interest in a biological fluid within or underneath the skin. Generally speaking, the noninvasive transdermal systems of this invention are comprised of two essential components: (1) a dry chemistry component; and (2) a wet chemistry component. The dry chemistry component comprises a super sensitive or conditioned membrane containing a compliment of chemical reagents which are specific for reacting with one or more analytes of interest. The interaction of the analyte(s) and such chemical reagents is manifest by the release or formation of indicator molecules, e.g., color change, which is indicative of the presence of the analyte(s) in the biological fluid. The surface of the super sensitive or conditioned membrane, which is receptive of and exposed to the analyte of interest, is relatively dense, thereby being generally free of cells, particles and / or other micromolecules which can potentially interfere with reaction of the analyte and the chemical reagents and / or the detection of a reporter molecule. In contrast, the opposing surface of the super sensitive or conditioned membrane is substantially less dense (more porous), thereby allowing for infusion of the reagent system during manufacture, and the formation, diffusion and visualization of reporter or indicator molecules, which are indicative of the presence of the analyte of interest and its level of concentration in the body fluid. The super sensitive or conditioned membranes of the present invention have the unique ability to detect analytes in very small sample volumes, e.g., about 25 mcl, in very small concentrations which are at least as low as about 5 mg / dl or about 5 mcg / ml.

[0032]A novel method of combining test chemistries known to those in the healing arts with the interstitial fluid collection medium in such a manner as to cause to be noninvasively and transdermally extracted from or through the skin, a quantity of analyte of interest sufficient for the chemical test to proceed and then to have the ability to read and record the results in a very short period of time, e.g., a few minutes, is described. This is one of the major objects of this invention.

[0033]In a preferred embodiment, the present invention contemplates small disposable transdermal patches for use with a reflectometer to detect an analyte such as glucose. In accordance with the present invention, the small disposable transdermal patches measure blood glucose levels noninvasively. In actuality, the small disposable transdermal patches of the present invention have the unique ability to detect the levels of glucose in interstitial fluid which directly correlate to those levels in the blood. Briefly, and not to be limited, the process is believed to occur as follows. A small disposable transdermal patch of the present invention, which is strategically placed on the targeted skin area, painlessly draws glucose from the interstitial fluid through the skin. The glucose is transported by the skin permeation enhancer combined with a gel capable of transporting glucose through the stratum corneum (upper level of the epidermis). The glucose in the interstitial fluid then undergoes a glucose-specific biochemical reaction at the site of the dry chemistry membrane, the biochemical reaction of which are contained within the dry chemistry membrane in the patch. This biochemical reaction results in a color formation which is then measured by a reflectometer and directly correlated to the blood glucose levels. It is believed that the membrane based technology of the present invention is at least 100, if not 400-500, times more sensitive for detection of very small concentrations of an analyte, e.g., about 5 mg / dl or 5 mcg / ml, in a very small volume of fluid, e.g., about 25 mcl, than what is being currently used with finger stick or finger lancing technology. Thus, and in accordance with the present invention, the extraction and detection process only requires a small patch and a small hand held reflectometer. And, because blood is not at all involved, pain and the risk of infection and disease transmission generally associated with glucose monitoring have been eliminated. Moreover, special handling procedures or disposal systems are no longer required.

Problems solved by technology

Some attempts to use infrared techniques to look through the skin to make blood sugar determinations have proven to be less reliable and too expensive for commercial application.

Unfortunately, the current methods of monitoring blood glucose levels has many drawbacks.

The current methods generally rely upon finger lancing to monitor blood glucose levels, which is not easy for anyone, especially young children and the elderly.

Moreover, because blood is involved, there is always the risk of infection and of transmission of blood borne diseases, such as AIDS.

If the blood glucose concentrations in such individuals are not properly maintained, the individuals become susceptible to numerous physiological problems, such as blindness, circulatory disorders, coronary artery disease, and renal failure.

Ethyl ether, however, is a known skin irritant which is flammable and explosive.

However, these techniques generally require invasive methods to draw a blood sample from a subject; typically, blood must be drawn several times a day by a finger prick, such as presently employed by a diabetic and externally determining the glucose level, generally by chemical reaction followed by colorimetric comparative testing.

Because the prior art invasive techniques are painful, individuals frequently avoid having blood glucose measured.

For diabetics, the failure to measure blood glucose on a prescribed basis can be very dangerous.

Also, the invasive techniques, which rely upon lancing blood vessels, create an enhanced risk for disease transmission and infection.

However, with respect to transdermal detection mechanism, the extracted analytes which are indicative of widely varying blood sugar levels may produce only very slight changes in developed color shade.

In many instances, the difference between developed color shade for an acceptable and an unacceptable blood sugar level cannot be accurately and repeatably detected by the naked eye.

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