Purpose: The goal of the study was to investigate a method for the real-time assessment of a target concentration in vivo using a combination of a spectral unmixing technique and a fluorescent probe specific for amyloid beta (Aβ) species, the biomarkers for Alzheimer's disease (AD).
Procedures: The probe CRANAD-3 has a significant emission wavelength shift upon binding to Aβ species. It was used to differentiate a bound probe from an unbound probe in a phantom, ex vivo in brain slices and whole brain, and in vivo in a transgenic mouse model of AD.
Results: The ex vivo unmixing imaging of AD brain clearly showed differential distribution of the bound and unbound probes between the brain tissue and blood vessels. The in vivo unmixed signals of bound CRANAD-3 reached a plateau with increasing dosage, demonstrating that these signals correspond to Aβ content, not probe injected dose.
Conclusion: This study provided evidence that signals processed by the spectral unmixing technique could be used as a real-time reporter of Aβ species loading in vivo and ex vivo.