Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
1997-07-07
2001-04-03
Lacyk, John P. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S345000, C600S347000, CD24S186000, C128S903000
Reexamination Certificate
active
06210326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microsensor for determination of glucose and other analytes in liquids based on affinity viscosimetry.
2. Description of the Related Art
Affinity sensors are important for analytics, as there exists a large number of affinity receptors, e.g. antibodies, which are not catalytically active. The technical task to transduce concentration dependent binding of analytes to the suitable receptor into an electrical signal within a microsensor, is an actual one, which is not easy to solve. A promising way for solving this task consists in the inclusion of receptor proteins and polymer affinity ligands in the lumen of a dialysis hollow fiber with a membrane which is permeable to the analyte (schultz, J. S. and Sims, G., 1979: Affinity sensors for individual metabolites, Biotechn. Bioeng. Symp-9, 65-71, Schultz, J. S., 1982, Optical sensor of plasma constituents, U.S. Pat. 4,344,438). The analyte-dependent dissociation of the receptor from the polymer ligand may be made detectable by diffusion of the polymer binding partner between the immobilized binding site and the ligand phase within the fiber lumen (Schultz, J. S., Mansouni, S. and Goldstein, I. J., 1982: Affinity sensor, A new technique for developing implantable sensor for glucose and other metabolites, Diabetes Care, 5,245-253, Knoll, D., Ehwald, K. E., Ehwald, R. Sorge, E., Ballersätdt, R. und Bolleroth, M., 1991: A silicon based microsystem for continuous in vivo glucose monitoring using a new reversible measuring principle) or by Fluorescence quenching (Meadows, D. L. and Schultz J. S., 1988, Fiberoptic bionsensor based on fluorescence energy transfer, Talante 35, 145-150). An interesting and simple alternative to the mentioned techniques is an affinity viscosimetry, measuring the concentration of affinity bonds mechanically in a direct manner. Affinity viscosimetry with dispersions of dextran and Concanavalin A is suitable for glucose determination in the blood sugar range and may be carried out with dialysis hollow fibers. The until now described hollow fiber viscosimeters do not have an electrical signal transducer and are unstable because of nonavoidable volume changes of the sensitive polymer phase (Ballerstädt, R. und Ehwald, R., 1992, Affinitätssensor, DE-P4203466, Ballerstädt, R., und Ehwald, R, 1994: Suitability of aqueous dispersion of dextran and Concanavalin A for glucose sensing in different variants of the affinity sensor, Biosensors and Bioelectronics, 9, 557-567).
An important field of application of microsensors is the on-line registration of analytes in body fluids, e.g. of glucose in the blood. Affinity viscosimetry is generally suitable for measuring relevant analytes which are known to bind to affinity receptor proteins. A miniaturized implantable affinity viscosimeter combined with a dialysis chamber or hollow fiber would therefore have promising applications. Such viscosimeter is not known.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to produce a reliably working sensor on the base of affinity viscosimetry which can be sufficiently miniaturized by microsystem technology for implantation purposes.
This and other objects of the present invention are attained by a hydraulic coupling of the sensitive polymer system dissolved in water and a measuring signal delivering system to a closed completely liquid-filled conducting system (hollow conductor). The analyte-sensitive polymer solution and eventually one or more other liquids which are not miscible with this polymer solution are mobile on a closed path. The measuring system contains a micromotor for driving the movement of the analyte-sensitive polymer solution and a pressure-, volume- or flow-sensitive unit delivering signals which are unequivocally related to the viscosity of the liquids.
For example, a hollow conductor with solid walls may be tightly connected at both ends with the endings of a hollow fiber which is filled with the sensitive polymer solution. The whole hollow conductor is filled with a liquid which can transduce forces between a pumping micromotor and the sensitive polymer solution within the fiber. Possible micromotors are magnetic particles or liquids in the magnetic field, dielectrically moved solids or liquids. The liquid movement within the hollow conductor is registrated either optically by photosensors at dragged interfaces or solids, or electromechanically by the reaction of the frictional reactive force on the micromotor. The micromotor is a microsystem on the base of silicon technology, for its application in vivo a microelectronic system with integrated transducing elements for energy and signals is opportune.
According to the invention, there exist several variants, enabling or facilitating galvanic uncoupling of the extracorporal monitoring and energy supply form intracorporal viscosimetric sensing device. For efficient transduction of energy and information it is especially lucrative that apart from the dialysis fiber or chamber, the hollow conductor is filled by a liquid which is nonmiscible with water. This enables the application of dielectric micromotors which can realize oscillating liquid movements with high efficiency and can deliver well transferable electrical signals (capacity based) for streaming. The application of the nonhydrophilic liquid in the hollow conductor enables the construction of the sensor according to the invention in a simple way and allows for fast diffusional equilibration of the analyte between the whole sensitive polymer phase and the external medium. The surface forces resulting from the contact of the different liquids may be used for prevention of rotating movements of the liquid through the hollow conductor and for restriction of the oscillating movements within a certain amplitude.
Further advantages of the invented principle are the complete independence from the external pressure, as changes in external pressure cannot induce liquid movements in a closed system completely filled with noncompressible liquid, and the potentially small volume of the device, as the sensitive part (dialysis chamber or hollow fiber) has a very small volume.
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patent: 4832034 (1989-05-01), Pizziconi et al.
patent: 5156972 (1992-10-01), Issachar
patent: 5174291 (1992-12-01), Schoonen et al.
patent: 5269891 (1993-12-01), Colin
patent: 5615671 (1997-04-01), Schoonen et al.
Astorino Michael
Helfgott & Karas, P C.
Lacyk John P.
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