Biology subjects

Heiles, B.

Publications and source records attributed to Heiles, B..

3 recordsLinked to original sources

bioRxiv2025

Acoustic pH sensor for dynamic ultrasound imaging of cellular acidification

Genetically encoded pH sensors based on fluorescent proteins enable dynamic optical imaging of cellular processes such as endocytosis and exocytosis. To date, light scattering in thick tissue as well as photobleaching of fluorescent proteins prevent deep cellular imaging over sustained periods of time. To visualize intracellular pH variations across opaque organs, we introduce a genetically encoded acoustic pH sensor dubbed pHonon. We modified the outer gas vesicle protein (GvpC) of echogenic protein nanostructures via histidine point mutations. At low pH, engineered gas vesicles exhibit an increased shell stiffness which switched their acoustic response from nonlinear to linear. By combining pHonons with nonlinear ultrasound imaging, we captured dynamic deep tissue images of lysosomal acidification by macrophages in murine liver. The combination of pHonon with nonlinear ultrasound creates the possibility for basic studies of endo- and exocytic activity in deep tissue of living opaque organisms.

bioengineering↗

bioRxiv2024

Nonlinear sound-sheet microscopy: imaging opaque organs at the capillary and cellular scale

Light-sheet fluorescence microscopy has revolutionized biology by visualizing dynamic cellular processes in three dimensions. However, light scattering in thick tissue and photobleaching of fluorescent reporters limit this method to studying thin or translucent specimens. Here we show that non-diffractive ultrasonic beams used in conjunction with a cross-amplitude modulation sequence and nonlinear acoustic reporters enable fast and volumetric imaging of targeted biological functions. We report volumetric imaging of tumor gene expression at the cm3 scale using genetically encoded gas vesicles, and localization microscopy of currently uncharted cerebral capillary networks using intravascular microbubble contrast agents. Nonlinear sound-sheet microscopy provides a [~]64x acceleration in imaging speed, [~]35x increase in imaged volume and [~]4x increase in classical imaging resolution compared to the state-of-the-art in biomolecular ultrasound.

bioengineering↗

bioRxiv2021

Volumetric ultrasound localization microscopy of the whole brain microvasculature

Technologies to visualize whole organs across scales in vivo are essential for our understanding of biology in health and disease. To date, only post-mortem techniques such as perfused computed tomography scanning or optical microscopy of cleared tissues achieve cellular resolution across entire organs and imaging methods with equal performance in living mammalian organs have yet to be developed. Recently, 2D ultrasound localization microscopy has successfully mapped the fine-scale vasculature of various organs down to a 10 m precision. However, reprojection issues and out-of-plane motion prevent complex blood flow quantification and fast volumetric imaging of whole organs. Here, we demonstrate for the first time in vivo volumetric ultrasound localization microscopy mapping of the rodent brain vasculature. We developed a complete methodological pipeline that includes specific surgery, a dedicated 3D ultrasound acquisition sequence, localization and tracking algorithms, motion correction and realignment, as well as the post-processing quantification of cerebral blood flow. We illustrate the power of this approach, by mapping the whole rat brain vasculature at a resolution of 12 m, revealing mesoscopic to macroscopic vascular architectures and cerebral blood flows ranging from 1 to 100 mm/s. Our results pave the way to the investigation of in vivo vascular processes across the mammalian brain in health and disease, in a wide range of contexts and models.

bioengineering↗