ISFET Array Detects Radioactivity via pH Shift
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Solution Overview
Problem
Current methods for analyzing radioactivity of biomolecules in an array format are inefficient, as they require expensive detectors and image analysis, and do not allow for simultaneous analysis of sequence information and radiolabeling of nucleic acids.
Innovation Solution
An ion-sensitive field effect transistor array is incubated in a microautoradiographic emulsion, where radioactivity forms a latent image that accelerates silver halide reduction to metallic silver upon development, causing a pH decrease measurable by the array, enabling direct detection of radioactivity without image scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional radioactivity detection methods are used, then radioactivity can be detected, but the equipment is expensive and requires image scanning analysis
Solution Approach 1:
The patent introduces silver halide emulsion as an intermediary substance that converts radioactivity signals into chemical changes (silver reduction). The semiconductor sensor then detects these chemical changes through pH changes in the developer solution, rather than directly detecting radioactivity. This intermediary approach allows using simple pH sensors instead of complex radioactivity detectors.
Solution Approach 2:
The patent replaces the mechanical/optical image scanning system with a chemical-electrical detection system. Instead of using image scanners to read autoradiographic films, the invention uses semiconductor pH sensors to directly measure pH changes in the developer solution, converting a visual analysis process into an automated electrical measurement process.
2Measurement precision
If separate analyses are performed for sequence information and radioactivity, then each can be analyzed accurately, but the process is time-consuming and requires multiple steps
Solution Approach 1:
The patent combines sequence information analysis and radioactivity detection into a single integrated process. The semiconductor sensor array simultaneously performs both functions by detecting pH changes that occur during the development of silver halide emulsion exposed to radioactivity, while the same array has already captured sequence information through previous hybridization steps.
Solution Approach 2:
The semiconductor sensor array is designed to perform multiple functions: it can detect sequence information through hybridization and detect radioactivity through pH measurement during emulsion development. This multi-functional approach eliminates the need for separate analysis systems and steps for different types of molecular analysis.
3Quantity of substance
If large volumes are used for analysis, then sufficient signal can be obtained, but the method lacks sensitivity for small volume samples
Solution Approach 1:
The patent uses an array format with multiple discrete sensing locations, allowing concentrated analysis in small volumes at each position. The silver halide emulsion and developer solution are confined to specific reaction chambers or well positions, creating localized high-concentration environments that enhance detection sensitivity without requiring large overall sample volumes.
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 allows for the simultaneous analysis of radioactivity and sequence information of nucleic acids, reducing costs and complexity, and can differentiate low levels of radioactivity in small volumes, enhancing sensitivity and flexibility.
Implementation Method 1
radioactivity forms a latent image that accelerates silver halide reduction to metallic silver
Implementation Method 2
silver halide reduction to metallic silver upon development
Implementation Method 3
incubating the array with a developer solution reducing the silver halides that have been exposed to radioactivity to elemental silver
Implementation Method 4
measuring pH at each separate reaction chamber, wherein decrease of the pH indicates the presence of radioactivity
Data Source
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AI summary
The present invention provides a method for determining radioactivity in an ion-sensitive field effect transistor array, the method comprising the steps of incubating the array with electron-sensitive silver-halide material and then incubating the array with a developer solution reducing the silver halides that have been exposed to radioactivity to elemental silver and simultaneously measuring pH at each separate reaction chambers, wherein decrease of the pH indicates the presence of radioactivity in a reaction chamber.