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Detecting Amyloid-β Accumulation via Immunofluorescent Staining in a Mouse Model of Alzheimer's Disease
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A High Affinity Red Fluorescence and Colorimetric Probe for Amyloid β Aggregates
K Rajasekhar1, Nagarjun Narayanaswamy1, N Arul Murugan2
1Bioorganic Chemistry Laboratory, New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bengaluru 560064, Karnataka, India.
Scientific Reports
|April 2, 2016
Summary
A new fluorescent probe, benzothiazole-coumarin (TC), detects toxic Alzheimer's disease amyloid β42 aggregates. This probe offers enhanced red fluorescence and colorimetric changes for early AD diagnosis.
Area of Science:
- Biochemistry
- Neuroscience
- Chemical Biology
Background:
- Alzheimer's disease (AD) diagnosis is challenging, with amyloid β (Aβ) aggregates as key biomarkers.
- Developing sensitive and selective probes for Aβ detection is crucial for early AD diagnosis.
Purpose of the Study:
- To develop a novel hemicyanine-based benzothiazole-coumarin (TC) probe for detecting toxic amyloid β42 (Aβ42) aggregates.
- To evaluate the probe's fluorescence and colorimetric properties, selectivity, binding affinity, and mechanism of action.
Main Methods:
- Synthesis and characterization of the benzothiazole-coumarin (TC) probe.
- Fluorescence and colorimetric assays for Aβ42 aggregate detection.
- Selectivity studies against other protein aggregates.
- Binding affinity measurements (Ka) and Thioflavin T (ThT) displacement assays.
- Spectroscopic analysis (absorption and emission) to study probe-aggregate interactions.
- Molecular docking and time-dependent density functional theory (TD-DFT) for computational validation.
Main Results:
- The TC probe exhibits a significant 'switch-on' fluorescence enhancement (~30-fold) with red emission (Emax = 654 nm) upon binding to Aβ42 aggregates.
- TC shows a distinct colorimetric change from light red to purple, indicating Aβ42 presence.
- The probe demonstrates high selectivity for Aβ42 fibrils over other protein aggregates.
- TC possesses a high binding affinity (Ka = 1.72 × 10^7 M⁻¹) for Aβ42 aggregates and can displace ThT.
- Spectroscopic and computational studies reveal that the probe's interaction with Aβ42 induces micro-environmental changes and red-shifted absorption.
Conclusions:
- The benzothiazole-coumarin (TC) probe is a promising tool for sensitive and selective detection of toxic Aβ42 aggregates.
- The probe's dual optical outputs (fluorescence and colorimetric) facilitate AD diagnosis.
- TC's ability to bind Aβ42 fibrils with high affinity and selectivity warrants further investigation for in vivo imaging and diagnostic applications.
