13 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
Recommended from our members
Antiretroviral treatment simplification with two-drug regimens: Impact of transmitted drug resistance mutations
The frequency of clinically relevant transmitted drug resistance mutations (DRMs) against drugs used for 2-drug regimens was 15.6%, but only 2% were not eligible for 1 or more 2-drug regimens. More than 50% of patients harboring any clinically relevant DRMs were found to be part of genetic transmission clusters
Recommended from our members
Antiretroviral Treatment Simplification With 2-Drug Regimens: Impact of Transmitted Drug Resistance Mutations.
The frequency of clinically relevant transmitted drug resistance mutations (DRMs) against drugs used for 2-drug regimens was 15.6%, but only 2% were not eligible for 1 or more 2-drug regimens. More than 50% of patients harboring any clinically relevant DRMs were found to be part of genetic transmission clusters
MiR-328 promotes glioma cell invasion via SFRP1-dependent Wnt-signaling activation
Background: Diffusely infiltrative growth of human astrocytic gliomas is one of the major obstacles to successful tumor therapy. Thorough insights into the molecules and pathways signaling glioma cell invasion thus appear of major relevance for the development of targeted and individualized therapies. By miRNA expression profiling of microdissected human tumor biopsy specimens we identified miR-328 as one of the main miRNAs upregulated in invading glioma cells in vivo and further investigated its role in glioma pathogenesis.
Methods: We employed miRNA mimics and inhibitors to functionally characterize miR-328, 3′ untranslated region luciferase assays, and T-cell factor/lymphoid enhancer factor reporter assays to pinpoint miR-328 targets and signaling pathways, and analyzed miR-328 expression in a large panel of gliomas.
Results: First, we corroborated the invasion-promoting role of miR-328 in A172 and TP365MG glioma cells. Secreted Frizzled-related protein 1 (SFRP1), an inhibitor of Wnt signaling, was then pinpointed as a direct miR-328 target. SFRP1 expression is of prognostic relevance in gliomas with reduced expression, being associated with significantly lower overall patient survival in both the Repository of Molecular Brain Neoplasia Data (REMBRANDT) and The Cancer Genome Atlas. Of note, miR-328 regulated both SFRP1 protein expression levels and Wnt signaling pathway activity. Finally, in human glioma tissues miR-328 appeared to account for the downregulation of SFRP1 preferentially in lower-grade astrocytic gliomas and was inversely related to SFRP1 promoter hypermethylation.
Conclusion: Taken together, we report on a novel molecular miR-328–dependent mechanism that via SFRP1 inhibition and Wnt activation contributes to the infiltrative glioma phenotype at already early stages of glioma progression, with unfavorable prognostic implications for the final outcome of the disease
Bacterial encapsulins as orthogonal compartments for mammalian cell engineering
We genetically controlled compartmentalization in eukaryotic cells by heterologous expression of bacterial encapsulin shell and cargo proteins to engineer enclosed enzymatic reactions and size-constrained metal biomineralization. The shell protein (EncA) from Myxococcus xanthus auto-assembles into nanocompartments inside mammalian cells to which sets of native (EncB,C,D) and engineered cargo proteins self-target enabling localized bimolecular fluorescence and enzyme complementation. Encapsulation of the enzyme tyrosinase leads to the confinement of toxic melanin production for robust detection via multispectral optoacoustic tomography (MSOT). Co-expression of ferritin-like native cargo (EncB,C) results in efficient iron sequestration producing substantial contrast by magnetic resonance imaging (MRI) and allowing for magnetic cell sorting. The monodisperse, spherical, and iron-loading nanoshells are also excellent genetically encoded reporters for electron microscopy (EM). In general, eukaryotically expressed encapsulins enable cellular engineering of spatially confined multicomponent processes with versatile applications in multiscale molecular imaging, as well as intriguing implications for metabolic engineering and cellular therapy
Bacterial encapsulins as orthogonal compartments for mammalian cell engineering
We genetically controlled compartmentalization in eukaryotic cells by heterologous expression of bacterial encapsulin shell and cargo proteins to engineer enclosed enzymatic reactions and size-constrained metal biomineralization. The shell protein (EncA) from Myxococcus xanthus auto-assembles into nanocompartments inside mammalian cells to which sets of native (EncB,C,D) and engineered cargo proteins self-target enabling localized bimolecular fluorescence and enzyme complementation. Encapsulation of the enzyme tyrosinase leads to the confinement of toxic melanin production for robust detection via multispectral optoacoustic tomography (MSOT). Co-expression of ferritin-like native cargo (EncB,C) results in efficient iron sequestration producing substantial contrast by magnetic resonance imaging (MRI) and allowing for magnetic cell sorting. The monodisperse, spherical, and iron-loading nanoshells are also excellent genetically encoded reporters for electron microscopy (EM). In general, eukaryotically expressed encapsulins enable cellular engineering of spatially confined multicomponent processes with versatile applications in multiscale molecular imaging, as well as intriguing implications for metabolic engineering and cellular therapy
Codanin-1, mutated in the anaemic disease CDAI, regulates Asf1 function in S-phase histone supply
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