High speed innovations in photoacoustic microscopy.

Photoacoustic microscopy (PAM) is a key implementation of photoacoustic imaging (PAI). PAM merges rich optical contrast with deep acoustic detection, allowing for broad biomedical research and diverse clinical applications. Recent advancements in PAM technology have dramatically improved its imaging speed, enabling real-time observation of dynamic biological processes in vivo and motion-sensitive targets in situ, such as brain activities and placental development.

Deep tissue photoacoustic imaging with light and sound.

Photoacoustic computed tomography (PACT) can harvest diffusive photons to image the optical absorption contrast of molecules in a scattering medium, with ultrasonically-defined spatial resolution. PACT has been extensively used in preclinical research for imaging functional and molecular information in various animal models, with recent clinical translations. In this review, we aim to highlight the recent technical breakthroughs in PACT and the emerging preclinical and clinical applications in deep tissue imaging.

Advanced deep-tissue imaging and manipulation enabled by biliverdin reductase knockout.

We developed near-infrared (NIR) photoacoustic and fluorescence probes, as well as optogenetic tools from bacteriophytochromes, and enhanced their performance using biliverdin reductase-A knock-out model (Blvra-/-). Blvra-/- elevates endogenous heme-derived biliverdin chromophore for bacteriophytochrome-derived NIR constructs. Consequently, light-controlled transcription with IsPadC-based optogenetic tool improved up to 25-fold compared to wild-type cells, with 100-fold activation in Blvra-/- neurons.

The sound of blood: photoacoustic imaging in blood analysis.

Blood analysis is a ubiquitous and critical aspect of modern medicine. Analyzing blood samples requires invasive techniques, various testing systems, and samples are limited to relatively small volumes. Photoacoustic imaging (PAI) is a novel imaging modality that utilizes non-ionizing energy that shows promise as an alternative to current methods.

Integrated Photoacoustic, Ultrasound, and Angiographic Tomography (PAUSAT) for NonInvasive Whole-Brain Imaging of Ischemic Stroke.

Presented here is an experimental ischemic stroke study using our newly developed noninvasive imaging system that integrates three acoustic-based imaging technologies: photoacoustic, ultrasound, and angiographic tomography (PAUSAT). Combining these three modalities helps acquire multi-spectral photoacoustic tomography (PAT) of the brain blood oxygenation, high-frequency ultrasound imaging of the brain tissue, and acoustic angiography of the cerebral blood perfusion. The multi-modal imaging platform allows the study of cerebral perfusion and oxygenation changes in the whole mouse brain after stroke.

Plasmonic nanorod probes' journey inside plant cells for SERS sensing and multimodal imaging.

Nanoparticle-based platforms are gaining strong interest in plant biology and bioenergy research to monitor and control biological processes in whole plants. However, monitoring of biomolecules using nanoparticles inside plant cells remains challenging due to the impenetrability of the plant cell wall to nanoparticles beyond the exclusion limits (5-20 nm). To overcome this physical barrier, we have designed unique bimetallic silver-coated gold nanorods (AuNR@Ag) capable of entering plant cells, while conserving key plasmonic properties in the near-infrared (NIR).

Multiscale photoacoustic tomography using reversibly switchable thermochromics.

Significance: Based on acoustic detection of optical absorption, photoacoustic tomography (PAT) allows functional and molecular imaging beyond the optical diffusion limit with high spatial resolution. However, multispectral functional and molecular PAT is often limited by decreased spectroscopic accuracy and reduced detection sensitivity in deep tissues, mainly due to wavelength-dependent optical attenuation and inaccurate acoustic inversion.

Aim: Previous work has demonstrated that reversible color-shifting can drastically improve the detection sensitivity of PAT by suppressing nonswitching background signals.

Three-dimensional non-invasive brain imaging of ischemic stroke by integrated photoacoustic, ultrasound and angiographic tomography (PAUSAT).

We present an ischemic stroke study using our newly-developed PAUSAT system that integrates photoacoustic computed tomography (PACT), high-frequency ultrasound imaging, and acoustic angiographic tomography. PAUSAT is capable of three-dimensional (3D) imaging of the brain morphology, blood perfusion, and blood oxygenation. Using PAUSAT, we studied the hemodynamic changes in the whole mouse brain induced by two common ischemic stroke models: the permanent middle cerebral artery occlusion (pMCAO) model and the photothrombotic (PT) model.

Sound out the impaired perfusion: Photoacoustic imaging in preclinical ischemic stroke.

Acoustically detecting the optical absorption contrast, photoacoustic imaging (PAI) is a highly versatile imaging modality that can provide anatomical, functional, molecular, and metabolic information of biological tissues. PAI is highly scalable and can probe the same biological process at various length scales ranging from single cells (microscopic) to the whole organ (macroscopic). Using hemoglobin as the endogenous contrast, PAI is capable of label-free imaging of blood vessels in the brain and mapping hemodynamic functions such as blood oxygenation and blood flow.