2 research outputs found
Whole-Cell Photoacoustic Sensor Based on Pigment Relocalization
Photoacoustic
(optoacoustic) imaging can extract molecular information
with deeper tissue penetration than possible by fluorescence microscopy
techniques. However, there is currently still a lack of robust genetically
controlled contrast agents and molecular sensors that can dynamically
detect biological analytes of interest with photoacoustics. In a biomimetic
approach, we took inspiration from cuttlefish who can change their
color by relocalizing pigment-filled organelles in so-called chromatophore
cells under neurohumoral control. Analogously, we tested the use of
melanophore cells from Xenopus laevis, containing compartments (melanosomes) filled with strongly absorbing
melanin, as whole-cell sensors for optoacoustic imaging. Our results
show that pigment relocalization in these cells, which is dependent
on binding of a ligand of interest to a specific G protein-coupled
receptor (GPCR), can be monitored in vitro and in vivo using photoacoustic
mesoscopy. In addition to changes in the photoacoustic signal amplitudes,
we could furthermore detect the melanosome aggregation process by
a change in the frequency content of the photoacoustic signals. Using
bioinspired engineering, we thus introduce a photoacoustic pigment
relocalization sensor (PaPiReS) for molecular photoacoustic imaging
of GPCR-mediated signaling molecules
Calcium Sensor for Photoacoustic Imaging
We
introduce a selective and cell-permeable calcium sensor for
photoacoustics (CaSPA), a versatile imaging technique that allows
for fast volumetric mapping of photoabsorbing molecules with
deep tissue penetration. To optimize for Ca<sup>2+</sup>-dependent
photoacoustic signal changes, we synthesized a selective metallochromic
sensor with high extinction coefficient, low quantum yield, and high
photobleaching resistance. Micromolar concentrations of Ca<sup>2+</sup> lead to a robust blueshift of the absorbance of CaSPA,
which translated into an accompanying decrease of the peak photoacoustic
signal. The acetoxymethyl esterified sensor variant was readily
taken up by cells without toxic effects and thus allowed us for the
first time to perform live imaging of Ca<sup>2+</sup> fluxes in genetically
unmodified cells and heart organoids as well as in zebrafish larval
brain via combined fluorescence and photoacoustic imaging