Selective Fluorescent Probe for ALDH1A1 Detection
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Solution Overview
Problem
Current methods for detecting cancer stem cells (CSCs) are limited by the inability to selectively target ALDH1A1 without confounding consequences, such as off-target binding and cross-reactivity with other ALDH isoforms, and require the use of efflux pump and ALDH inhibitors, which can have unintended effects in live animals.
Innovation Solution
Development of a highly selective, activity-based fluorescent probe, AlDeSense, that specifically targets ALDH1A1 by utilizing a photostable Pennsylvania Green dye platform with a pendant benzaldehyde moiety, which is selectively oxidized by ALDH1A1, allowing for the modulation of fluorescent intensity to image CSCs without the need for inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If BODIPY-aminoacetaldehyde (BAAA) is used as a fluorescent probe for ALDH detection, then ALDH activity can be detected, but cross-reactivity with several ALDH isoforms occurs rendering interpretation challenging
Solution Approach 1:
The patent introduces a control probe (BAAA-control) with modified chemical structure that lacks the reactive aldehyde group, creating local chemical differentiation between the test probe and control probe. This allows the test probe to react with ALDH while the control probe remains inert, enabling differentiation of specific ALDH activity from background noise and cross-reactivity
Solution Approach 2:
The patent uses efflux pump inhibitors and ALDH inhibitors as intermediary substances to modulate probe behavior. These inhibitors serve as mediators that enhance the contrast between specific and non-specific probe binding, allowing more accurate interpretation of ALDH activity despite inherent cross-reactivity issues
2Measurement precision
If efflux pump inhibitors and ALDH inhibitors are used with BAAA to distinguish CSC signal, then CSC detection is enabled, but unintended consequences occur in live animals
Solution Approach 1:
The patent extracts the essential function of inhibitor-based discrimination by incorporating control elements directly into the probe design. The BAAA-control probe internally contains the control function, eliminating the need for separate inhibitor treatments and their associated harmful effects in live animal models
Solution Approach 2:
The control probe serves itself by providing an inherent reference signal that automatically accounts for non-specific binding and background accumulation. This self-contained control mechanism eliminates the need for external inhibitor interventions, reducing harmful effects while maintaining signal discrimination capability
3Measurement precision
If antibody-dye conjugates are used to target CSC surface biomarkers, then CSC imaging is achieved, but off-target binding and uneven staining occur due to poor permeation
Solution Approach 1:
The patent replaces the mechanical/physical approach of antibody-dye conjugates (which rely on passive diffusion and binding) with a chemical approach using small molecule fluorescent probes. These probes actively react with ALDH enzyme active sites through covalent bonding, enabling deep tissue penetration and uniform staining without off-target binding issues
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
AlDeSense provides a 20-fold fluorescent enhancement upon ALDH1A1 activation, is selective against other ALDH isoforms, and is chemostable, enabling accurate imaging of CSCs in cell cultures and animal models, thereby simplifying the detection of CSCs and monitoring their plasticity.
Implementation Method 1
aldehyde dehydrogenase (ALDH), when present in the contacted cell, oxidizes the aldehyde moiety R1 of the xanthenone to a carboxyl moiety
Implementation Method 2
the fluorescent intensity of the contacted cell is modulated by the presence or absence of ALDH, thereby providing an image of aldehyde dehydrogenase activity in the contacted cell
Data Source
AI summary
High aldehyde dehydrogenase 1A1 (ALDH1A1) activity has emerged as a reliable marker for the identification of both normal and cancer stem cells. Herein, is presented AlDeSense, a turn-on green fluorescent probe for aldehyde dehydrogenase 1A1 (ALDH1A1) and Ctrl-AlDeSense, a matching non-responsive reagent. AlDeSense exhibits a 20-fold fluorescent enhancement when treated with ALDH1A1. Through the application of surface marker antibody staining, tumorsphere assays, and assessment of tumorigenicity, the disclosed results show that cells exhibiting high AlDeSense signal intensity have properties of cancer stem cells. Herein, is also reported the development of a red congener, red-AlDeSense. Importantly, red-AlDeSense represents one of only a few examples of a turn-on sensor in the red region using the d-PeT quenching mechanism.