KEYWORDS: Liquid crystal on silicon, Proteins, Luminescence, In vivo imaging, Molecules, Spectroscopy, Alzheimer's disease, In vitro testing, Polymers, Optical properties
Luminescent conjugated polymers (LCPs) have been frequently utilized for optical biosensors. The detection schemes of
these sensors are employing the light harvesting properties or the conformation sensitive optical properties of the
conjugated polymers. LCPs have been utilized as colorimetric and fluorescent sensing elements for the recording of
biological processes. However, LCPs have several limitations for being used as real time in vivo imaging agents. In this
regard, novel thiophene based molecular scaffolds, denoted luminescent conjugated oligothiophenes (LCOs) have been
developed. These LCOs are chemically defined molecules having distinct side chain functionalizations and a precise
number of thiophene units. Herein the utilization of LCOs as specific ligands for the pathological hallmarks underlying
protein misfolding diseases, such as Alzheimer's disease, is described. The use of the conformation sensitive optical
properties of the LCOs for spectral separation of these pathological entities in a diversity of in vitro, ex vivo or in vivo
systems is demonstrated. The protein aggregates are easily identified due to the conformation-dependent emission profile
from the LCOs and spectral assignment of protein aggregates can be obtained. Overall, these probes will offer practical
research tools for studying protein misfolding diseases and facilitate the study of the molecular mechanism underlying
these disorders.
KEYWORDS: Liquid crystal on silicon, Proteins, In vivo imaging, Molecules, Luminescence, Tissues, Optical properties, Real time imaging, Molecular mechanisms, Biosensing
Molecular probes for selective identification of biomolecular targets are important to advance our understanding of the
molecular mechanisms underlying pathological events and for clinical diagnostic of specific diseases. Luminescent
conjugated polythiophenes (LCPs) have been utilized as colorimetric and fluorescent sensing elements for the recording
of biological processes, such as DNA-hybridization and ligand-receptor interactions. However, LCPs have several
limitations for being used as real time in vivo imaging agents. In this regard, novel thiophene based molecular scaffold,
denoted luminescent conjugated oligothiophenes (LCOs) have been developed. The LCOs are chemically defined
molecules having distinct side chain functionalizations and a precise number of thiophene units. Properly functionalized
LCO showed a striking specificity and selectivity towards distinct molecular targets, such as protein aggregates under
physiological conditions. The protein aggregates were easily identified due to the conformation-dependent emission
profile from the LCOs and spectral assignment of protein aggregates both in vitro and in ex vivo tissue samples could be
obtained. It was also shown that LCOs could be used for live imaging of intracellular molecules and compartments in
cells. Overall, we demonstrate that LCOs have the potential of being utilized as powerful practical research tools for
studying biological processes in real time.
We report on the initial time-resolved luminescense and nonlinear absorption properties of two polythiophenes 3-substituted with chiral charged amino acid-derivatized substituents, POWT and POMT. The photo-physical characterization yielded quantum efficiency typically in the range 0.01 - 0.1, however, with two-photon absorption cross-section better than or similar to a typical two-photon reference chromophore, such as fluorescein. They were tested as conformational sensitive optical probes for the recording of pH-induced conformational changes of synthetic peptides, proteins and samples of protein amyloid fibrils characteristic of amyloid related diseases. Particularly, the POMT polyelectrolyte with the L-enantiomeric side chains is shown to favor this induction of well defined structure as judged by the circular dichroic signal as well as a stronger enhancement of luminescense for the L-form over the D-form complex. Furthermore, time-resolved fluorescense and two-photon induced fluorescence both also showed a difference in the complexation with the D and L form. This shows that the multi-photon excitation path can be an efficient means for chiral recognition of biomolecular complexes. It is demonstrated how the conjugated polyelectrolyte L-POMT can be used to spectrally image the formation of amyloid fibrils of insulin using both one- and two-photon absorption based fluorescence imaging.
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