Biosensing and -imaging with enantiomeric luminescent conjugated polythiophenes using single- and multiphoton excitation

Summary form only given. Proteins can alter their conformation and aggregate leading to pathogenic states. Beta sheet-rich fibrillar assemblies are known as amyloid fibrils and these can lead to many devastating diseases known as the amyloidoses, including Alzheimer´s disease and the systemic amyloidoses. Thioflavin T or S (ThT or ThS) and Congo red are commonly used as detection agents for amyloid fibrils. ANS, Bis-ANS and DCVJ are known to prove valuable in order to study the conformational state and evolution of the aggregation process into amyloid fibrils. Simple, sensitive, and versatile tools that detect the fibrillar conformation of amyloidogenic proteins are of great importance. In this regard, fluorescent conjugated polyelectrolytes (CPs) have been studied for being used as amyloid specific dyes for staining of amyloid-containing tissue and as conformational sensitive probes for the detection of conformational changes in biomolecules. These are capable of selectively detecting biological processes and have large potential for being used as biosensors and in biomolecular devices. In particular, biospecific interactions can be detected through the impact on photoinduced charge or excitation transfer or through the conformational alterations of the polyelectrolyte chains. We present results of time-resolved luminescense and nonlinear absorption properties of polythiophenes 3-substituted with chiral charged amino acid-derivatized substituents. The photo-physical characterization yielded quantum efficiency typically in the range 0.01 - 0.1, however, with two-photon absorption cross-section more than 10 times better than a typical two-photon reference chromophore, such as fluorescein.