Fluorogenic pH-Sensitive Dyes with Tunable pKa
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Solution Overview
Problem
Current pH-sensitive fluorescent dyes used in biological research and medical diagnostics have limitations, including a shifted working range towards acidic pH values and instability in solution, making them unsuitable for detecting pH changes in physiological conditions.
Innovation Solution
Development of novel pH-sensitive fluorescent dyes that omit hydroxyl or thiol groups, incorporating a dialkylamino group para to the alkoxy substituent, allowing for tunable pKa values and improved stability, which enables detection of pH changes in the green portion of the UV/VIS spectrum at physiological pH values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PET-based pH sensors with amino groups are used, then fluorescence response to pH changes is achieved, but the working range is shifted to acidic pH values due to low pKa
Solution Approach 1:
The patent changes the chemical parameters of the sensor molecule by replacing the amino group with a phenolic hydroxyl group, which has a higher pKa value. This parameter change shifts the working pH range from acidic to physiological/neutral conditions while maintaining the fluorescence response mechanism through ionization of the phenolic group.
Solution Approach 2:
The patent extracts the amino group indicator moiety from the sensor structure and replaces it with a phenolic hydroxyl group. This removal and replacement eliminates the low pKa limitation while preserving the core functionality of pH-dependent fluorescence changes.
2Reliability
If rhodamine-based pH sensors with hydroxyl or thiol groups are used, then fluorescence quenching upon deprotonation is achieved, but the compounds are unstable in solution
Solution Approach 1:
The patent removes the unstable hydroxyl or thiol groups from the rhodamine-based sensor structure. By eliminating these problematic functional groups, the patent resolves the solution instability issue while maintaining pH sensitivity through the ionization of remaining phenolic or other stable acidic groups.
Solution Approach 2:
The patent changes the chemical composition parameters by selecting alternative functional groups (phenolic hydroxyl groups with appropriate pKa values) that provide both fluorescence response and solution stability, avoiding the use of hydroxyl or thiol groups at positions that cause instability.
3Device complexity
If dyes with fixed pKa values are used, then simple structure is maintained, but the dyes cannot be tuned to match specific biological pH conditions
Solution Approach 1:
The patent creates a universal dye structure with a phenolic hydroxyl group whose pKa can be systematically adjusted by introducing different electron-donating or electron-withdrawing substituents on the aromatic ring. This provides a single structural platform that can be adapted to various pH conditions without requiring fundamentally different molecular architectures.
Solution Approach 2:
The patent modifies local regions of the molecular structure (substituent groups on the aromatic ring) to adjust the overall pKa value. By changing electron density at specific positions through substituent effects, the patent achieves pKa tuning while maintaining the core fluorescent structure and its essential properties.
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
The new dyes provide enhanced stability and tunable pKa values, enabling effective detection of pH changes in biological systems, particularly at neutral and biologically relevant pH ranges, overcoming the limitations of existing dyes.
Implementation Method 1
When such a molecule absorbs a photon creating an excited electronic state, the electron of the amino group's unshared pair transfers to the orbital vacated by excitation. Such an electron transfer, referred to as Photoinduced Electron Transfer (PET) prevents the excited molecule from emission transition
Implementation Method 2
pH-sensitive fluorescent dyes and assays for use in a variety of applications including monitoring of intracellular processes are disclosed
Data Source
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AI summary
Disclosed herein are compounds, compositions, methods and kits for detecting pH in samples using pH-sensitive fluorescent dyes. The compounds disclosed herein are novel xanthene-derivative dyes comprising an aniline moiety with one or more electron donating groups, which dyes are for detecting pH in samples either in vitro or in vivo. Also described herein are processes for preparing said dyes for use in the disclosed compositions, methods and kits.