Photoacoustic tomography of calcium activity in the mouse brain could potentially provide whole-brain coverage of neural activity and therefore offer new insights into brain function. Here we report the development and characterization of a novel photoacoustic calcium-sensitive probe based on the HaloTag protein which is suitable for in vivo imaging in mice. The photoacoustic brightness and signal enhancement upon calcium binding were measured using a custom-built spectroscopy setup and compared to the available far-red calcium indicator NIR-GECO1. Additionally, we conducted validation experiments on tissue-mimicking phantoms using a Fabry-Perot-based photoacoustic tomography setup to determine the depth limit and concentration detection threshold of the imaged probes. Furthermore, we tested various in vivo delivery methods, by analyzing brain slices from mice labeled with the photoacoustic probe. These experiments demonstrated that we are able to specifically label neurons targeted brain regions, confirming the suitability of these photoacoustic probes for in vivo calcium imaging applications.
The goal of this study was to assess the ability of singlet oxygen generated at photodynamic treatment using different irradiation modes to inhibit the enzyme TAQ polymerase activity. Experimentally were determined the laser irradiation dose and the singlet oxygen concentration that results to complete inhibition of TAQ polymerase activity. The results show that using pulse mode irradiation is 1.5x more efficient then continuous wave. TAQ polymerase damage was also assessed by fluorescence spectrometry — tryptophan residues fluorescence is decreased if damaged by singlet oxygen during photodynamic treatment. It was observed that on doses, where TAQ polymerase looses its enzymatic activity the fluorescence decreases only by 7%. The fluorescence decrement of tryptophan correlates with damage to the enzyme.
In this present study we investigate the Radachlorin photosensitizer accumulation in K562 cells and Hela cells and determined the cell viability after PDT. Using the macroscopic singlet oxygen modeling and cellular photosensitizer concentration the singlet oxygen threshold doses for K562 cells and Hela cells were calculated.
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