Glucose Sensor with Optical Waveguide and Dialysis Membrane
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Solution Overview
Problem
Current glucose monitoring methods, such as enzymatic conversion and optical spectroscopy, face limitations including discontinuous measurements, enzyme consumption, risk of device breakage, and interference from blood cells, leading to inaccurate and unreliable glucose level determination.
Innovation Solution
A glucose sensor using a catheter with a first optical waveguide and a detection chamber filled with a membrane-permeable detection fluid for glucose, allowing diffusion-based glucose measurement in the near-infrared spectrum, with a reference channel for systematic error subtraction, enabling precise and continuous glucose monitoring without direct blood contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If enzymatic conversion of glucose is used for measurement, then glucose concentration can be detected, but the measurement can only be performed discontinuously and the test strip can only be used once
Solution Approach 1:
The patent replaces the enzymatic chemical conversion system with a direct optical detection system. Near-infrared light is used to directly measure glucose concentration in interstitial fluid through a dialysis membrane, eliminating the need for enzymatic conversion and enabling continuous measurement without disposable test strips.
Solution Approach 2:
The invention implements continuous glucose monitoring by maintaining a constant flow of perfusate through the dialysis needle and continuously measuring the optical properties of the dialysate. This allows uninterrupted glucose concentration detection over extended periods, resolving the discontinuity limitation of enzymatic methods.
2Productivity
If an implanted enzymatically functionalized sensor surface is used for quasi-continuous measurement, then continuous glucose monitoring is achieved, but the lifetime is limited by progressive enzyme consumption requiring frequent recalibration
Solution Approach 1:
The patent eliminates enzymatic components entirely by using direct near-infrared optical detection of glucose in the dialysate. This substitution removes the source of enzyme consumption and degradation, thereby extending sensor lifetime and eliminating the need for frequent recalibration while maintaining continuous monitoring capability.
Solution Approach 2:
The dialysate acts as an intermediary medium that carries glucose from the interstitial fluid to the optical detection cell. This intermediary approach allows indirect but continuous measurement without direct contact between the detection system and biological tissues, improving reliability and reducing calibration needs.
3Measurement precision
If optical spectroscopy with a measurement fiber recess is used for glucose determination, then glucose can be detected in blood stream, but the recess forms a breaking point that increases risk of fiber breakage and patient endangerment
Solution Approach 1:
The invention extracts the measurement function from a vulnerable recessed structure and relocates it to a protected optical detection cell positioned outside the body. The dialysis needle delivers the sample to an external detector, eliminating the structural weak point that created breaking risks while maintaining the ability to measure blood sugar values.
Solution Approach 2:
The dialysate serves as an intermediary that transports glucose from the blood stream through the dialysis membrane to an external optical detection system. This intermediary approach allows glucose measurement without requiring a vulnerable recess in the measurement fiber, thereby eliminating the breaking point hazard.
4Measurement precision
If absorption measurement is performed directly in blood, then glucose detection is possible, but the measurement is influenced by other effects such as blood cell buildup that impairs accuracy
Solution Approach 1:
The invention extracts glucose from the complex blood matrix through dialysis and measures it in a simplified dialysate solution. This extraction process separates glucose from interfering blood cells and proteins, allowing accurate optical absorption measurement without the harmful effects present in whole blood.
Solution Approach 2:
The dialysis membrane and dialysate solution act as intermediaries that selectively allow glucose passage while blocking blood cells and large proteins. This intermediary system purifies the sample before measurement, eliminating interference from blood cells and improving measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides continuous, precise glucose monitoring with minimal external influence, achieving a mean absolute relative error of less than 5% and reducing the need for frequent recalibration, while minimizing the risk of device breakage and interference from blood cells.
Implementation Method 1
the glucose depending on a concentration gradient diffuses out from the blood or the interstitial fluid into the detection fluid
Implementation Method 2
a membrane having a separation capacity of at most 20 kDa... which is not permeable to blood cells and larger molecules such as fats, proteins
Implementation Method 3
light in dependence on the glucose concentration in the detection fluid is absorbed in the detection chamber
Data Source
AI summary
A method for determining the glucose value in blood or in interstitial liquids and to a glucose sensor including a catheter which has one or more openings in the region of the distal end of the catheter; a first optical waveguide which is arranged in the catheter and which includes a coupling surface at the distal end of the optical waveguide; a measuring probe which is arranged in the region of the distal end of the catheter, is coupled to the coupling surface of the first optical waveguide, and has a mirror arranged opposite the coupling surface of the first optical waveguide and a detection chamber between the coupling surface of the first optical waveguide and the mirror; a detection liquid for glucose in the detection chamber; and a membrane which encloses at least the detection chamber filled with the detection liquid and which has a separation capacity of maximally 20 kDA.