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Luminescence and Two-Photon Absorption Cross Section of Novel Oligomeric Luminescent Conjugated Polythiophenes for Diagnostics of Amyloid Fibrils
Mikael Lindgren, Eirik Glimsdal, Andreas Åslund, Rosalyn Simon, Per Hammarström and K. Peter R. Nilsson

Here we present the TPA cross section and quantum efficiencies of a series of novel oligomeric luminescent conjugated polythiophenes used for detection and spectral diagnostics of amyloid protein aggregates of the amyloid-beta peptide associated with Alzheimer’s disease. Specifically, these probes consist of pentameric or heptameric thiophenes derivatives with carboxylic substituents attached onto various thiophene rings. The probes absorbs over a broad range approx. 400–500 nm with quantum efficiency of approx. 20% in at neutral pH conditions, and also showed TPA cross sections of 5–50 GM in the range 700–840 nm, in the same order of magnitude as commonly used fluorescein derivatives. Importantly, the multiphoton excitation capabilities of LCPs provided excellent performance when compared to imaging using conventional “single photon” excitation. It is also demonstrated their utilization in both one- and two-photon excitation laser scanning microscope spectral imaging for diagnostics of Alzheimer disease pathology in ex vivo histological sections.

Keywords: Fluorescent dyes, thiophene oligomers, amyloid detection, amyloid spectroscopic diagnostics, TPA cross section, quantum efficiency.

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