Ratiometric Fluorescent Probe for Low-Background APN Detection
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Solution Overview
Problem
Existing fluorescent probes for detecting aminopeptidase N (APN) suffer from high background interference and lack sensitivity, making them inadequate for accurate and selective detection in biological samples.
Innovation Solution
A ratiometric fluorescent probe comprising an alanyl group and Nile blue derivative (NB) is developed, which exhibits a significant fluorescence peak shift upon reacting with APN, allowing for sensitive and selective detection of APN through a fluorescence ratio change.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If affinity-based fluorescent probes are used for detecting APN, then fluorescent imaging can be performed on cancer cells or tumor-transplanted nude mice, but background interference increases heavily affecting imaging quality
Solution Approach 1:
The patent introduces a reaction-based detection mechanism as an intermediary between the probe and APN. The probe contains a fluorophore and a recognition unit that specifically reacts with APN to trigger fluorescence emission. This reaction-based approach acts as a mediator that converts the presence of APN into a detectable fluorescent signal while inherently suppressing background interference, as the fluorescence is generated only upon specific enzymatic reaction rather than through direct binding as in affinity-based probes
Solution Approach 2:
The patent utilizes reaction-based fluorescence probes where the fluorescence intensity or ratio changes significantly upon reaction with APN. The probe design incorporates a recognition unit that, when cleaved or modified by APN enzymatic activity, induces a large change in fluorescence parameters (intensity or wavelength ratio). This parameter change approach allows for high-contrast imaging by comparing fluorescence signals before and after the reaction, effectively reducing the impact of background interference
2Object-affected harmful factors
If reaction-based fluorescent probes are used to reduce background interference, then detection sensitivity must be maintained, but probe design and development complexity increases
Solution Approach 1:
The patent divides the fluorescent probe into distinct functional modules: a fluorophore unit and a recognition unit. The recognition unit contains a specific peptide sequence or substrate structure that is selectively cleaved or modified by APN. This segmentation allows for modular design where the fluorophore provides the signaling function while the recognition unit provides the specificity, simplifying the overall design process by separating detection and recognition functions into independent components that can be optimized separately
Solution Approach 2:
The patent employs composite fluorescent probe structures combining different functional components with complementary properties. The probe integrates a fluorophore with specific photophysical properties and a recognition unit with high specificity for APN. This composite approach allows the probe to simultaneously achieve low background interference through reaction-based detection and high sensitivity through optimized fluorophore-recognition unit combinations, while the modular nature of composite design facilitates systematic optimization and development
3Measurement precision
If fluorescent probes are used for quantitative detection in complex biological samples like urine, then detection limit must be low, but sample complexity and interference increase
Solution Approach 1:
The reaction-based probe acts as a specific intermediary that selectively responds to APN in complex urine samples. The probe's recognition unit is designed to specifically interact with APN through enzymatic reaction, while remaining insensitive to other components in the urine matrix. This specificity allows the probe to effectively filter out sample complexity and interference, responding only to the target analyte and enabling low detection limits even in complex biological fluids
Solution Approach 2:
The patent utilizes probes that exhibit large changes in fluorescence intensity or wavelength ratio upon reaction with APN. This significant parameter change provides a strong analytical signal that can be easily distinguished from background noise and interference in complex urine samples. The large signal change enables detection at low concentrations (low detection limit) by providing sufficient signal-to-noise ratio even when the analyte concentration is low and sample matrix effects are present
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 probe achieves a detection limit of 15 μg/mL for APN and can be used for quantitative detection in urine samples, as well as imaging in cells and living organisms, providing a reliable tool for diagnosing APN-related diseases.
Implementation Method 1
Fluorescence spectroscopy has attracted much attention due to its unique advantages such as simplicity, convenience, non-invasiveness, real-time detection, high sensitivity, high temporal and spatial resolution, and in vivo imaging
Data Source
AI summary
A method for preparing a ratiometric fluorescent probe includes following steps: subjecting boc-L-alanine to a reaction with the NB in a dichloromethane (DCM) solution for 24 h to obtain an intermediate, and subjecting the intermediate to a reaction with CF3COOH to obtain the ratiometric fluorescent probe. A structure of the ratiometric fluorescent probe comprises an alanyl group and a Nile blue derivative.