Wavelength-dependent optoacoustic imaging probes for NMDA receptor visualisation

The cellular localisation and binding specificity of two NMDAR-targeted near-IR imaging probes has been examined by microscopy, followed by exemplification of MSOT to monitor simulated glutamate bursts in cellulo and a preliminary study in mice observing the signal in the brain

Nucleus size and DNA accessibility are linked to the regulation of paraspeckle formation in cellular differentiation

Background Many long noncoding RNAs (lncRNAs) have been implicated in general and cell type-specific molecular regulation. Here, we asked what underlies the fundamental basis for the seemingly random appearance of nuclear lncRNA condensates in cells, and we sought compounds that can promote the disintegration of lncRNA condensates in vivo. Results As a basis for comparing lncRNAs and cellular properties among different cell types, we screened lncRNAs in human pluripotent stem cells (hPSCs) that were differentiated to an atlas of cell lineages. We found that paraspeckles, which form by aggregation of the lncRNA NEAT1, are scaled by the size of the nucleus, and that small DNA-binding molecules promote the disintegration of paraspeckles and other lncRNA condensates. Furthermore, we found that paraspeckles regulate the differentiation of hPSCs. Conclusions Positive correlation between the size of the nucleus and the number of paraspeckles exist in numerous types of human cells. The tethering and structure of paraspeckles, as well as other lncRNAs, to the genome can be disrupted by small molecules that intercalate in DNA. The structure-function relationship of lncRNAs that regulates stem cell differentiation is likely to be determined by the dynamics of nucleus size and binding site accessibility.FWN – Publicaties zonder aanstelling Universiteit Leide

In vivo hybrid microscopy of small model organisms.

We present the investigation of in vivo small model organisms, which are well established in biological and biomedical research, using a hybrid multiphoton and optoacoustic microscope (HyMPOM). The unique capabilities of HyMPOM for multimodal and potentially label-free signal acquisition, high resolution, as well as deep and fast imaging allow extraction of detailed information across large areas of living tissue on the microscale. Applying HyMPOM to living zebrafish-like fish larvae allowed exploration of the structural composition of the entire brain, including the brain vasculature and the neuronal network. Applying HyMPOM to the ears of living mice enabled accurate imaging of vasculature, connective tissue, keratinocytes, and sebaceous glands. The hybrid microscope proposed here constitutes a novel approach to explore small model organisms in vivo in great detail by revealing the spatial distribution and interplay of various tissue compartments on the microscale

Genetically encodable materials for non-invasive biological imaging.

Many questions in basic biology and medicine require the ability to visualize the function of specific cells and molecules inside living organisms. In this context, technologies such as ultrasound, optoacoustics and magnetic resonance provide non-invasive imaging access to deep-tissue regions, as used in many laboratories and clinics to visualize anatomy and physiology. In addition, recent work has enabled these technologies to image the location and function of specific cells and molecules inside the body by coupling the physics of sound waves, nuclear spins and light absorption to unique protein-based materials. These materials, which include air-filled gas vesicles, capsid-like nanocompartments, pigment-producing enzymes and transmembrane transporters, enable new forms of biomolecular and cellular contrast. The ability of these protein-based contrast agents to be genetically encoded and produced by cells creates opportunities for unprecedented in vivo studies of cellular function, while their amenability to genetic engineering enables atomic-level design of their physical, chemical and biological properties

Near-infrared photoacoustic imaging probe responsive to calcium.

Photoacoustic imaging (PAI) is an attractive imaging modality that can volumetrically map the distribution of photoabsorbing molecules with deeper tissue penetration than multiphoton microscopy. To enable dynamic sensing of divalent cations via PAI, we have engineered a new reversible near-infrared probe that is more sensitive to calcium as compared to other biologically relevant cations. The metallochromic compound showed a strong reduction of its peak absorbance at 765 nm upon addition of calcium ions that was translated into robust signal changes in photoacoustic images. Therefore, the heptamethine cyanine dye will be an attractive scaffold to create a series of metallochromic sensors for molecular PAI

Hyperpolarized multi-metal¹³C-sensors for magnetic resonance imaging.

We introduce hyperpolarizable13C-labeled probes that identify multiple biologically important divalent metals via metal-specific chemical shifts. These features enable NMR measurements of calcium concentrations in human serum in the presence of magnesium. In addition, signal enhancement through dynamic nuclear polarization (DNP) increases the sensitivity of metal detection to afford measuring micromolar concentrations of calcium as well as simultaneous multi-metal detection by chemical shift imaging. The hyperpolarizable13C-MRI sensors presented here enable sensitive NMR measurements and MR imaging of multiple divalent metals in opaque biological samples

Pushing the boundaries of neuroimaging with optoacoustics.

With the central ability to visualize a variety of endogenous chromophores and biomarkers or exogenous contrast agents, optoacoustic (photoacoustic) imaging empowers new experimental capabilities for investigating brain mechanisms and functions. Here, the operational principles of optoacoustic neuroimaging are reviewed in conjunction with recent advances enabling high-resolution and real-time observation, which extend beyond the reach of optical imaging methods. Multiple implementations of optoacoustics for monitoring hemodynamics and neuro-vascular responses in the brain are showcased. The unique capabilities of optoacoustic imaging for multi-spectral cellular and molecular sensing are discussed with reference to recent application for visualizing healthy and diseased brains. Outstanding challenges in the field are considered in the context of current and future applications of optoacoustic neuroimaging for basic and translational neuroscience research. In pushing the boundaries of brain imaging, optoacoustic methods afford major insights into the neuronal mechanisms of brain functions and organization of behavior