Countdown Biosensors for Quantitative Small Molecule Detection
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Solution Overview
Problem
Current fluorescent biosensors face challenges in measuring small molecule dynamics due to ambiguity in photon emission changes, which can be attributed to either target concentration or biosensor concentration, and are either fast but ambiguous or slow and quantitative but expensive, with difficulty in constructing novel biosensors.
Innovation Solution
Development of 'countdown sensors' that combine a fluorescent domain capable of spontaneous photoswitching via cis-trans isomerization or protonation, with an analyte binding domain that alters the photoswitching rate in response to analyte binding, allowing for fast, quantitative measurement of small molecule concentrations without instrument-dependent variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fluorescent intensity measurement is used, then measurement speed and cost are improved, but measurement precision deteriorates due to ambiguity between target concentration and biosensor concentration effects
Solution Approach 1:
The patent segments the fluorescent biosensor into two functionally independent domains: a fluorescent domain that reports target binding through photoswitching rate changes, and an analyte binding domain that provides specificity. This segmentation allows the fluorescent properties to be decoupled from concentration dependencies, enabling intensity measurements to reflect only target concentration rather than a combination of target and sensor concentrations.
Solution Approach 2:
The patent changes the operational parameter from measuring steady-state fluorescent intensity (which conflates sensor and target concentration effects) to measuring photoswitching rate (which is independent of sensor concentration). By using optogenetic photoswitching with controlled illumination, the system transforms the measurement parameter to one that is insensitive to biosensor concentration variations, thereby resolving the quantification ambiguity.
2Measurement precision
If fluorescent lifetime measurement is used, then measurement precision is improved by eliminating concentration ambiguity, but productivity deteriorates due to slower measurement speed and higher cost
Solution Approach 1:
The patent creates a functional copy of the quantitative measurement capability of lifetime sensors using intensity measurements. By engineering the fluorescent domain to exhibit photoswitching behavior whose rate is modulated by analyte binding, the system replicates the concentration-independent quantification of lifetime sensors through a different physical mechanism (photoswitching kinetics rather than lifetime decay), thereby achieving lifetime-like precision with intensity-like speed and cost.
3Adaptability or versatility
If novel fluorescent biosensors are constructed through traditional mutation and screening, then adaptability is improved for different targets and colors, but ease of manufacture deteriorates due to several years of work and high failure rate
Solution Approach 1:
The patent creates a universal platform where a single fluorescent domain design can be paired with different analyte binding domains to create biosensors for multiple targets and wavelengths. The photoswitching fluorescent domain serves as a universal reporter module that can be combined with various binding specificities, eliminating the need for de novo engineering of each biosensor and enabling rapid adaptation to different analytical needs through modular assembly.
Solution Approach 2:
The patent performs preliminary engineering of the fluorescent domain to establish robust photoswitching behavior with appropriate kinetics before combining it with analyte binding domains. By pre-optimizing the fluorescent component's photoswitching properties through rational design and characterization, the system eliminates the need for extensive mutation and screening during biosensor construction, allowing direct assembly of functional biosensors with predictable performance.
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
Countdown sensors provide a fast, cheap, and unambiguous method for measuring small molecule concentrations by modulating fluorescent intensity or color, achieving quantitative results similar to lifetime sensors while maintaining ease of use and construction simplicity.
Implementation Method 1
the fluorescent domain can spontaneously photoswitch by cis-trans isomerization or protonation
Implementation Method 2
the fluorescent domain can spontaneously photoswitch by cis-trans isomerization or protonation
Implementation Method 3
the rate of isomerization or rate of protonation is altered by binding of the analyte binding domain to an analyte of interest
Data Source
AI summary
Described herein are countdown biosensors, and methods of using the same, comprising fluorophores which can spontaneously photoswitch between two or more states with different fluorescent properties (e.g. fluorescent intensity or fluorescent color). The countdown sensor comprises a fluorescent domain which can spontaneously photoswitch, and a sensing domain which responds to the desired input. The countdown sensor is “read” by measuring the photoswitching rate. In certain embodiments, the decay of fluorescent intensity over time (due to spontaneous photoswitching of different fluorescent domains) can be made to depend on the concentration of different small molecules, such as calcium and nicotinamides.