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	<title>In-Vivo Imaging &#8211; Science</title>
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	<title>In-Vivo Imaging &#8211; Science</title>
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		<title>Switchable dual-focus metalens extends depth of photoacoustic eye imaging</title>
		<link>https://scienmag.com/switchable-dual-focus-metalens-extends-depth-of-photoacoustic-eye-imaging/</link>
		
		<dc:creator><![CDATA[Denise Maddox]]></dc:creator>
		<pubDate>Thu, 08 Oct 2026 22:00:11 +0000</pubDate>
				<category><![CDATA[Technology and Engineering]]></category>
		<category><![CDATA[advanced optical lens technologies]]></category>
		<category><![CDATA[blood vessel imaging in living eyes]]></category>
		<category><![CDATA[corneal neovascularization]]></category>
		<category><![CDATA[depth extension in photoacoustic imaging]]></category>
		<category><![CDATA[depth of field]]></category>
		<category><![CDATA[electrically tunable metalens for imaging]]></category>
		<category><![CDATA[flat metalens with multiple focal planes]]></category>
		<category><![CDATA[flat optics]]></category>
		<category><![CDATA[high-resolution biomedical imaging]]></category>
		<category><![CDATA[hybrid light and sound imaging techniques]]></category>
		<category><![CDATA[In-Vivo Imaging]]></category>
		<category><![CDATA[liquid crystal]]></category>
		<category><![CDATA[metalens]]></category>
		<category><![CDATA[metasurface]]></category>
		<category><![CDATA[microvasculature]]></category>
		<category><![CDATA[Nanophotonics]]></category>
		<category><![CDATA[non-invasive eye imaging techniques]]></category>
		<category><![CDATA[ophthalmic imaging]]></category>
		<category><![CDATA[optical microscopy resolution-depth trade-off]]></category>
		<category><![CDATA[photoacoustic imaging of abnormal vessel growth]]></category>
		<category><![CDATA[photoacoustic microscopy]]></category>
		<category><![CDATA[silicon nitride]]></category>
		<category><![CDATA[switchable dual-focus metalens]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=250001</guid>

					<description><![CDATA[Researchers at POSTECH have built an electrically switchable dual-focus metalens that extends the imaging depth of photoacoustic microscopy to nearly 1.2 millimeters while preserving micron-scale resolution, enabling label-free in vivo imaging of corneal neovascularization in rat eyes.]]></description>
										<content:encoded><![CDATA[<p>For decades, one of the most stubborn trade-offs in optical microscopy has been the relationship between resolution and depth. Focus light tightly enough to resolve individual capillaries, and the sharp zone of your image shrinks to a razor-thin sliver. Loosen the focus to cover more depth, and the fine detail dissolves. A research team at Pohang University of Science and Technology (POSTECH) in South Korea has now demonstrated an elegant way out of this dilemma, using a flat, electrically switchable metalens to give photoacoustic microscopy two diffraction-limited focal planes that can be swapped at the flick of a voltage. Writing in Light: Science &amp; Applications, the team led by Junsuk Rho and Chulhong Kim shows that the approach can image blood vessels across nearly the entire depth of a living rat eye, tracking the abnormal vessel growth that follows a chemical corneal burn.</p>
<p>The technique at the heart of the work is photoacoustic microscopy, or PAM, a hybrid imaging modality that marries light and sound. A pulsed laser is delivered into tissue, where molecules such as hemoglobin absorb the energy and heat slightly, expanding and launching ultrasonic waves. Because ultrasound scatters far more weakly in tissue than light does, these waves can be detected and traced back to their origin, yielding images with optical contrast but acoustic penetration. Optical-resolution PAM, the variant used here, focuses the laser beam as tightly as diffraction allows, achieving micron-scale lateral resolution that can resolve the microvascular networks feeding the iris, choroid, and cornea. The catch is that this tight focusing produces a very shallow depth of field: structures even a fraction of a millimeter away from the focal plane blur dramatically, forcing researchers into slow, repeated refocusing scans to build a three-dimensional image.</p>
<p>Previous attempts to stretch the depth of field have relied on nondiffracting beams, such as Bessel beams and needle beams, which concentrate light into long, pencil-like axial profiles. These beams do maintain resolution over a longer range, but they carry a punishing penalty: their energy is distributed into prominent side lobes that generate spurious photoacoustic signals, and spreading the laser power over a larger volume weakens the signal at any single depth, degrading the signal-to-noise ratio. The POSTECH team took a fundamentally different route. Rather than smearing a single focus along the axis, they built a metalens that produces two separate, diffraction-limited Gaussian foci, each as strong and clean as a conventional lens focus, and switches between them electrically without moving a single mechanical part.</p>
<p>The metalens itself is a marvel of nanoscale engineering. It consists of silicon nitride nanostructures, each smaller than the wavelength of light, arranged on a flat glass substrate. Each nanostructure, or meta-atom, acts as a tiny waveguide that imparts a precise phase delay to passing light. By combining two phase-control mechanisms, the propagation phase and the geometric, or Pancharatnam-Berry, phase, the designers encoded two entirely independent lens phase profiles into the same surface, one for right-handed circularly polarized light and one for left-handed circularly polarized light. When the incident beam is right-circularly polarized, the metalens focuses at 4.5 millimeters; flip the polarization to left-handed, and the focus jumps to 5.2 millimeters. In water, where the device is designed to operate to minimize photoacoustic signal loss, this translates into two focal planes separated by roughly 0.9 millimeters.</p>
<p>Choosing the right material was critical, because photoacoustic imaging drives the lens with a high-power pulsed laser at 532 nanometers, the wavelength at which hemoglobin absorbs strongly. Any absorption in the lens material would both waste laser energy and generate unwanted photoacoustic signals from the lens itself. The team used plasma-enhanced chemical vapor deposition to grow silicon nitride films, carefully tuning the ratio of silane to nitrogen gas precursors to engineer the film&#8217;s bandgap. The optimal recipe, a silane-to-nitrogen ratio of 1.52, yielded a high refractive index of 2.4 with a near-zero extinction coefficient at 532 nanometers, and a wide optical bandgap of 5.17 electronvolts. A full micrometer-thick film of this material absorbs only about two percent of the green laser light, keeping the lens optically quiet while maximizing the focusing efficiency of its meta-atoms, each of which was optimized to act as a half-wave plate with conversion efficiencies exceeding seventy percent.</p>
<p>The electrical switching is performed by a liquid crystal cell placed in front of the metalens. The liquid crystal, a common material called 5CB, rotates its molecules in response to an applied alternating voltage, changing the polarization state of the transmitted light. At 0.87 volts, the output is right-circularly polarized and the metalens focuses at the near plane; at 1.03 volts, it becomes left-circularly polarized and the focus shifts to the far plane. The response time is about 250 milliseconds, fast enough to alternate between modes during a scan, and the optical contrast between the on- and off-state foci reaches 40:1 at the near focus and 20:1 at the far one. Crucially, both focal spots exhibit Strehl ratios close to unity, meaning each behaves as a nearly ideal diffraction-limited Gaussian focus rather than a compromised beam shape. The measured lateral resolutions, 3.1 and 3.7 micrometers for the two modes, match theoretical predictions almost exactly.</p>
<p>To turn this into an imaging system, the researchers mounted the metalens on a custom ring-shaped ultrasound transducer made from an 18-micrometer-thick polyvinylidene fluoride film, with the metalens sitting in a central aperture so that the optical and acoustic axes are perfectly coaxial. Bench tests with resolution targets and layered nylon threads confirmed that switching modes reliably shifted the sharp focal zone by about 0.9 millimeters, extending the usable axial imaging range to roughly 1.2 millimeters, a dramatic improvement over conventional single-focus PAM. Tests in a scattering phantom made of water, gelatin, and intralipid showed that the deeper focus mode genuinely improved contrast and resolution for objects buried about a millimeter deeper, confirming the effect survives realistic tissue-like scattering.</p>
<p>The demonstration that will interest clinicians most came in living animals. The team imaged the eyes of Sprague-Dawley rats, first healthy animals and then a model of corneal neovascularization induced by applying an alkali-soaked filter paper to the cornea, a standard model of chemical burn injury. In the healthy eye, the short-focus mode sharply resolved the root vessels and fine microvasculature of the iris, while the long-focus mode brought deeper structures into view, including the posterior ciliary vessel and pupil-associated vasculature that appeared blurred in the near mode. Fourteen days after the burn, the dual-focus system mapped the newly grown corneal vessels in detail while simultaneously imaging iris vessels as deep as 1.5 millimeters beneath the neovascular layer in one mode and about 2.2 millimeters in the other, a 0.7-millimeter extension in detectable depth. Notably, the images confirmed that the pathological new vessels remained strictly confined to the cornea, leaving the iris vasculature untouched.</p>
<p>The quantitative results underscore why this matters. Vessels imaged out of focus appear artificially fat: iris vessels measured through the near-focus mode showed an apparent average diameter of about 42 micrometers, but when the focus was shifted deeper, the same vessels measured a truer 16 micrometers, comparable to the roughly 18-micrometer diameter of the corneal vessels measured in their own focal plane. Meanwhile, the total area of the neovascular lesion came out nearly identical in both modes, at 5.55 and 5.65 square millimeters, showing that the dual-focus approach yields reliable lesion-scale measurements even as it trades resolution between depths. The 0.9-millimeter focal separation neatly spans the thickness of a typical cornea, around 0.5 to 0.6 millimeters, meaning the clinically relevant corneal layers fall comfortably within the high-resolution regime of the system.</p>
<p>The researchers are candid about the limitations and the road ahead. The current frame rate of about 0.42 frames per second could rise to 20 frames per second with faster optical scanning, though that would demand motion compensation to counter respiration-induced eye movement. Switching modes changes the numerical aperture slightly, which can be corrected by subpixel registration when merging the two image sets, and extending the design to multispectral imaging will require metasurfaces that correct for the wavelength dispersion of silicon nitride. Still, the concept reaches well beyond the eye: the same tunable dual-focus optics could be folded into optical coherence tomography, two-photon microscopy, or metalenses designed around the optical properties of skin and brain tissue. What the POSTECH team has delivered is more than a clever lens. It is a demonstration that flat, electrically reconfigurable optics can solve one of biomedical imaging&#8217;s oldest trade-offs, offering a compact, mechanically silent path to high-resolution, high-contrast, volumetric imaging of living tissue.</p>
<p><strong>Subject of Research:</strong> An electrically tunable dual-focus metalens integrated into photoacoustic microscopy for depth-extended in vivo imaging of ophthalmic vascular disease</p>
<p><strong>Article Title:</strong> Electrically switchable dual-focus metalens for depth-extended in vivo photoacoustic imaging of ophthalmic vascular disease</p>
<p><strong>Article References:</strong> Kim, H., Park, E., Park, J., Oh, D. K., Shin, J., Heo, H., Kim, C., &amp; Rho, J. (2026). Electrically switchable dual-focus metalens for depth-extended in vivo photoacoustic imaging of ophthalmic vascular disease. <em>Light: Science &amp;amp; Applications, 15</em>(1), Article 369. <a href="https://doi.org/10.1038/s41377-026-02365-8" rel="noopener noreferrer">https://doi.org/10.1038/s41377-026-02365-8</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1038/s41377-026-02365-8" rel="noopener noreferrer">10.1038/s41377-026-02365-8</a></p>
<p><strong>Keywords:</strong> metalens, metasurface, photoacoustic microscopy, silicon nitride, liquid crystal, corneal neovascularization, ophthalmic imaging, depth of field, nanophotonics, in vivo imaging, microvasculature, flat optics</p>
]]></content:encoded>
					
		
		
		<post-id xmlns="com-wordpress:feed-additions:1">250001</post-id>	</item>
		<item>
		<title>Chemical Trick Gives MRI a Clear Window on Brain Molecules It Could Never See</title>
		<link>https://scienmag.com/chemical-trick-gives-mri-a-clear-window-on-brain-molecules-it-could-never-see/</link>
		
		<dc:creator><![CDATA[Cassandra Pierce]]></dc:creator>
		<pubDate>Tue, 06 Oct 2026 05:00:53 +0000</pubDate>
				<category><![CDATA[Medicine]]></category>
		<category><![CDATA[advanced neuroimaging techniques]]></category>
		<category><![CDATA[biomolecular detection in living tissue]]></category>
		<category><![CDATA[brain metabolism]]></category>
		<category><![CDATA[brain molecule imaging]]></category>
		<category><![CDATA[chemical reactions for medical imaging]]></category>
		<category><![CDATA[chemical shift]]></category>
		<category><![CDATA[chemical shift engineering]]></category>
		<category><![CDATA[Depression]]></category>
		<category><![CDATA[fluoxetine]]></category>
		<category><![CDATA[In-Vivo Imaging]]></category>
		<category><![CDATA[magnetic resonance spectroscopy]]></category>
		<category><![CDATA[molecular imaging]]></category>
		<category><![CDATA[molecular imaging in neuroscience]]></category>
		<category><![CDATA[molecular probes]]></category>
		<category><![CDATA[MRI contrast enhancement]]></category>
		<category><![CDATA[neurotransmitters]]></category>
		<category><![CDATA[non-invasive brain chemistry analysis]]></category>
		<category><![CDATA[norepinephrine]]></category>
		<category><![CDATA[overcoming spectral overlap in spectroscopy]]></category>
		<category><![CDATA[preclinical imaging]]></category>
		<category><![CDATA[proton magnetic resonance spectroscopy]]></category>
		<category><![CDATA[reaction-based MRI signal manipulation]]></category>
		<category><![CDATA[spectral resolution in MRI]]></category>
		<category><![CDATA[Translational Medicine]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=240286</guid>

					<description><![CDATA[Researchers in Shanghai have engineered a molecular probe that converts the neurotransmitter norepinephrine into a product resonating at 9.7 ppm, opening an interference-free detection window for in vivo proton magnetic resonance spectroscopy.]]></description>
										<content:encoded><![CDATA[<p>Magnetic resonance imaging has long been the workhorse of modern medicine, but its lesser-known sibling, proton magnetic resonance spectroscopy, has always promised something more intimate: the ability to eavesdrop on the chemistry of living tissue without so much as a needle. That promise has been hampered by an awkward physical reality. Nearly every molecule the body cares about — glucose, glutamate, lactate, the neurotransmitters that carry our moods — crowds its hydrogen signals into the same narrow slice of the spectrum, a region between 1 and 5 parts per million on the chemical shift scale. The result is a spectral traffic jam in which the signature of any one biomolecule blurs into the signatures of dozens of its neighbors. A team of researchers in Shanghai has now demonstrated a way to break that jam wide open, and their solution is as chemically elegant as it is conceptually simple: make the target molecule undergo a reaction that relocates its signal to a part of the spectrum where nothing else lives.</p>
<p>The strategy, described in the Journal of Translational Medicine, is what the investigators call reaction-based chemical shift engineering. Rather than trying to untangle overlapping resonances with ever more sophisticated pulse sequences or higher magnetic fields, the team sidestepped the problem entirely. They designed a molecular probe that reacts selectively with a chosen target — in their proof-of-concept study, the neurotransmitter norepinephrine — and converts it into a new chemical species whose protons resonate far outside the crowded endogenous window. The product of the reaction, 4-hydroxybutanal, carries an aldehyde proton that rings out at approximately 9.7 parts per million, a spectral neighborhood essentially deserted by the metabolites of living tissue and safely distant from the towering water signal that dominates every in vivo proton spectrum.</p>
<p>The choice of norepinephrine was no accident. This catecholamine neurotransmitter sits at the center of the brain&#8217;s arousal and reward circuitry, and disturbances in its signaling have been implicated in depression for decades — indeed, some of the most widely prescribed antidepressants, including fluoxetine, are thought to modulate noradrenergic tone among their downstream effects. Yet norepinephrine has been notoriously difficult to observe in a living brain. Optical probes cannot penetrate the skull, positron emission tomography tracers offer limited chemical specificity, and conventional spectroscopy cannot pick the molecule out of the dense thicket of overlapping signals. A probe that renders norepinephrine visible as a clean, isolated peak would therefore fill a genuine gap in both neuroscience research and translational drug development.</p>
<p>The probe itself, designated FS, works through a cascade of nucleophilic substitution reactions. When it encounters norepinephrine, the catecholamine&#8217;s amine and hydroxyl groups attack the probe in sequence, triggering a chemical rearrangement that liberates 4-hydroxybutanal as the detectable product. The team did not simply assert this mechanism; they supported it with theoretical simulations that mapped the reaction pathway and predicted the chemical shift of the resulting aldehyde proton. That computational grounding matters, because the entire strategy hinges on a quantitative prediction: that the product&#8217;s resonance would land at a frequency far enough from every endogenous signal to be resolved cleanly even at the moderate field strengths available in clinical and preclinical settings.</p>
<p>Validation proceeded in careful steps, from the test tube to the living brain. In aqueous solutions, the probe showed favorable selectivity for norepinephrine over a panel of structurally related catecholamines and other biological amines, along with robust resistance to interference and stability across the physiological pH range — properties that are essential for any reagent intended to function in the chemically noisy environment of cells and blood. The investigators then moved to PC12 cells, a widely used model line derived from rat adrenal tissue that differentiates into neuron-like cells and secretes catecholamines. Inside these cells, the probe successfully detected endogenous norepinephrine release, demonstrating that it could function not merely against purified standards but against the genuine molecular inventory of a living cell.</p>
<p>The decisive test came in vivo. Working on a 7.0 Tesla magnetic resonance system — a field strength common in preclinical research and increasingly in human imaging — the team administered the probe to live rats that had been treated with fluoxetine, a pharmacological manipulation expected to elevate norepinephrine signaling in the brain. The characteristic aldehyde resonance near 9.7 parts per million appeared in the spectra of the treated animals, providing what the researchers describe as in vivo monitoring of pharmacologically elevated norepinephrine. In other words, for the first time in this experimental context, a specific neurotransmitter could be tracked in a living brain as a single, interference-free spectroscopic peak, using the same fundamental physics that powers every clinical MRI scanner.</p>
<p>The technical significance of this achievement is worth unpacking for readers who do not live and breathe spectroscopy. Chemical shift — the tiny displacement of a nucleus&#8217;s resonance frequency caused by its electronic environment — is the fundamental currency of magnetic resonance spectroscopy. Aldehyde protons are among the most deshielded protons in organic chemistry, which is why they resonate at such high parts-per-million values. By designing a reaction that manufactures an aldehyde in situ, the team effectively hijacked the extreme end of the chemical shift scale as a private detection channel. No pulse-sequence trickery, no spectral deconvolution, no isotope labeling with its attendant cost and regulatory burden: just a targeted chemical transformation that moves the signal out of the crowd. The approach is, in principle, generalizable — any analyte for which a selective reaction can be devised that yields a product with a distinctive chemical shift becomes a candidate for the same treatment.</p>
<p>The translational implications stretch across several domains. In disease diagnosis, an interference-free window would allow clinicians to quantify specific biomarkers in the brain or in tumors with a specificity that conventional proton spectroscopy cannot deliver, potentially distinguishing pathological biochemistry from normal variation. In dynamic metabolic monitoring, the ability to follow a neurotransmitter&#8217;s fluctuations over time could illuminate how psychiatric medications actually reshape brain chemistry in individual patients. In preclinical drug evaluation, the method offers pharmaceutical researchers a non-invasive readout of target engagement in animal models — a way to confirm that an experimental compound genuinely changes the neurochemical landscape it is designed to change, without sacrificing the animals at each time point. The authors frame the work as establishing a generalizable strategy for expanding the metabolic detection scope of proton MRS, and the framing seems justified by the breadth of those applications.</p>
<p>Caveats remain, as they always do on the road from proof of concept to bedside. The study was conducted in rats at 7 Tesla with a probe administered exogenously, and the safety, pharmacokinetics, and clearance of such probes in humans would require extensive evaluation before any clinical deployment. The sensitivity of the method — how little norepinephrine can be detected, and how quickly — will determine whether it can capture the fast, transient dynamics of neurotransmission or only slower, tonic changes. And for each new target molecule, chemists will need to design a new probe with the right selectivity, kinetics, and biocompatibility, a nontrivial task that the elegant norepinephrine example does not automatically solve for every analyte. Still, the conceptual barrier that has constrained proton spectroscopy for half a century — the crowding of all endogenous signals into a few parts per million — has now been shown to be circumventable by design rather than by brute force.</p>
<p>What makes this work resonate beyond its immediate field is the way it reframes a classic instrumentation problem as a chemistry problem. For decades, the response to spectral congestion in magnetic resonance has been to build bigger magnets and cleverer sequences. This team&#8217;s answer was to reach into the molecule itself and rearrange it. If reaction-based chemical shift engineering proves as adaptable as its creators suggest, the crowded 1-to-5-ppm window that has defined the limits of proton spectroscopy may no longer be the whole story — and the quiet, empty region beyond 5 parts per million could become a busy new address for the molecules of the mind.</p>
<p><strong>Subject of Research:</strong> Reaction-based chemical shift engineering for interference-free in vivo proton magnetic resonance spectroscopy of norepinephrine</p>
<p><strong>Article Title:</strong> Reaction-based chemical shift engineering unlocks interference-free detection window for in vivo proton magnetic resonance spectroscopy</p>
<p><strong>Article References:</strong> Lv, G., Gao, J., Qi, M., Meng, X., Tang, H., Han, F., &amp; Zhang, J. (2026). Reaction-based chemical shift engineering unlocks interference-free detection window for in vivo proton magnetic resonance spectroscopy. <em>Journal of Translational Medicine</em>. <a href="https://doi.org/10.1186/s12967-026-08931-3" rel="noopener noreferrer">https://doi.org/10.1186/s12967-026-08931-3</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1186/s12967-026-08931-3" rel="noopener noreferrer">10.1186/s12967-026-08931-3</a></p>
<p><strong>Keywords:</strong> magnetic resonance spectroscopy, chemical shift, molecular probes, norepinephrine, depression, neurotransmitters, in vivo imaging, fluoxetine, preclinical imaging, molecular imaging, brain metabolism, translational medicine</p>
]]></content:encoded>
					
		
		
		<post-id xmlns="com-wordpress:feed-additions:1">240286</post-id>	</item>
		<item>
		<title>D-Amino-Acid-Powered Enzyme Cascade Maps Biomolecules Across Living Animals</title>
		<link>https://scienmag.com/d-amino-acid-powered-enzyme-cascade-maps-biomolecules-across-living-animals/</link>
		
		<dc:creator><![CDATA[Ophelia Keating]]></dc:creator>
		<pubDate>Wed, 30 Sep 2026 17:48:31 +0000</pubDate>
				<category><![CDATA[Medicine]]></category>
		<category><![CDATA[Advanced Live Animal Imaging]]></category>
		<category><![CDATA[APEX2]]></category>
		<category><![CDATA[Biomolecular Mapping in Living Animals]]></category>
		<category><![CDATA[chemical biology]]></category>
		<category><![CDATA[D-amino acid oxidase]]></category>
		<category><![CDATA[D-Amino-Acid-Powered Enzyme Cascade]]></category>
		<category><![CDATA[Enzyme-Based Molecular Identification]]></category>
		<category><![CDATA[In Vivo Protein and RNA Tagging]]></category>
		<category><![CDATA[In-Vivo Imaging]]></category>
		<category><![CDATA[innovative techniques in cellular biology]]></category>
		<category><![CDATA[Low-Toxicity Molecular Labeling]]></category>
		<category><![CDATA[LRPPRC]]></category>
		<category><![CDATA[mitochondria]]></category>
		<category><![CDATA[Molecular Machinery Visualization in Animals]]></category>
		<category><![CDATA[Overcoming Proximity Labeling Limitations]]></category>
		<category><![CDATA[PRADA]]></category>
		<category><![CDATA[PRADA Proximity Labeling Technique]]></category>
		<category><![CDATA[Protein-RNA Interaction Mapping]]></category>
		<category><![CDATA[proximity labeling]]></category>
		<category><![CDATA[RNA structure]]></category>
		<category><![CDATA[spatial proteomics]]></category>
		<category><![CDATA[structurome]]></category>
		<category><![CDATA[Tissue-Specific Molecular Neighborhoods]]></category>
		<category><![CDATA[xenograft]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=217698</guid>

					<description><![CDATA[Researchers have developed PRADA, an engineered enzyme cascade that uses D-amino acids to generate hydrogen peroxide locally, enabling low-toxicity protein and RNA proximity labeling and the first in vivo mapping of mitochondrial RNA structure in living mice.]]></description>
										<content:encoded><![CDATA[<p>For decades, biologists have dreamed of watching the molecular machinery of life not in a dish, but inside a living animal — seeing which proteins cluster at a synapse, which RNAs fold into which shapes, and how these arrangements shift as tissues grow, age, or turn cancerous. A new technique reported in Nature Chemical Biology brings that vision substantially closer. The method, called PRADA — peroxidase reactions activated by D-amino acids — lets researchers tag and map proteins and RNA molecules in their immediate molecular neighborhoods inside fruit flies, roundworms, zebrafish and mice, all with remarkably low toxicity and background noise.</p>
<p>The core challenge that PRADA addresses is a long-standing bottleneck in proximity labeling. The most widely used tools, such as APEX2 and TurboID, genetically fuse an engineered enzyme to a protein of interest. The enzyme then converts a supplied small molecule into a reactive species that tags nearby biomolecules, which can later be fished out and identified by mass spectrometry or sequencing. The catch is the trigger. APEX2 requires a bolus of exogenous hydrogen peroxide, a reactive oxidant that damages cells and diffuses poorly through intact tissues. TurboID requires biotin, which works in vivo but generates its own background labeling. Neither approach has proven ideal for the delicate, three-dimensional environment of a living organism.</p>
<p>The Shanghai- and Singapore-based team, led by Shuo Han of the Chinese Academy of Sciences together with Yue Wan of the Genome Institute of Singapore, took a different route: instead of supplying hydrogen peroxide directly, they engineered the system to make it on the spot. PRADA pairs a genetically fused peroxidase with an engineered D-amino acid oxidase, or DAAO, derived from the yeast Rhodotorula gracilis. When researchers deliver a nonproteinogenic D-amino acid such as D-phenylalanine or D-alanine — molecules that animal cells largely ignore — the oxidase converts them into hydrogen peroxide right next to the peroxidase. That locally generated oxidant then activates the peroxidase, which converts phenol probes such as biotin-phenol into short-lived radicals that covalently tag whatever proteins or nucleic acids sit within roughly a few tens of nanometers.</p>
<p>The engineering itself was nontrivial. The team used structural modeling and rational mutagenesis to delete a flexible C-terminal loop of the R. gracilis oxidase, producing a monomeric variant that fuses cleanly with APEX2 without disrupting either enzyme&#8217;s activity. Extended data show the researchers systematically tested fusion orientations, split-enzyme designs and D-amino acid concentrations, using fluorescence assays to confirm that the cascade produces hydrogen peroxide efficiently and that the labeling signal colocalizes precisely with the tagged protein&#8217;s known subcellular address. When the two enzymes were expressed separately rather than fused, labeling dropped sharply, confirming that the reaction is genuinely confined to the immediate vicinity of the fusion protein.</p>
<p>That spatial confinement is what makes the method safe enough for living animals. Because the hydrogen peroxide is generated in situ at nanometer scales and consumed almost immediately by the peroxidase, it never accumulates to toxic levels. The researchers measured malondialdehyde levels, a marker of lipid peroxidation, and protein carbonylation after PRADA labeling and found both below detection limits or unchanged compared with controls. Mitochondrial superoxide, a sensitive indicator of oxidative stress, was actually lower in PRADA-labeled cells than in cells labeled conventionally with APEX2 and exogenous peroxide. Cell viability assays showed no measurable harm from the D-amino acid treatment itself. In effect, PRADA converts the most dangerous step of proximity labeling into a self-limiting, locally contained reaction.</p>
<p>The versatility of the platform is striking. In cultured cells, the team targeted PRADA to the nucleus, nucleolus, endoplasmic reticulum, plasma membrane and mitochondria, and in each case recovered proteomic profiles consistent with the known composition of those compartments. They also showed that PRADA can drive functional polymer assembly — the genetically targeted chemical assembly of conducting or insulating materials inside living cells — extending the technique beyond mapping into materials synthesis. And, crucially, they demonstrated that the peroxidase step can label RNA as well as protein, opening a door that most proximity-labeling systems leave closed.</p>
<p>That RNA reactivity became the foundation of the study&#8217;s most inventive application. When peroxidase radicals oxidize RNA, they leave behind chemical lesions that cause reverse transcriptase to misread bases during cDNA synthesis. The team realized these misincorporations could be read as a molecular fingerprint of RNA structure: nucleotides that are chemically accessible — that is, single-stranded and exposed — accumulate more mutations than nucleotides buried inside base-paired helices. Building on the logic of mutational profiling sequencing, they developed PRADA-MaPseq, a strategy that converts peroxidase labeling directly into a spatiotemporally resolved map of RNA secondary structure inside living cells.</p>
<p>They benchmarked PRADA-MaPseq against the well-established mitochondrial DMS-MaPseq datasets, showing that uracil and guanine reactivity scores accurately reproduce known structures of mitochondrial messenger RNAs, with area-under-the-curve values reaching 0.60 to 0.82 across transcripts and inter-experimental correlation coefficients as high as 0.96 for individual transcripts. The approach worked with both 4-thiouridine and 6-selenoguanosine metabolic labeling, and the team optimized reverse transcriptase choice to maximize mutational signal. In short, they turned a proximity-labeling enzyme into a structure-probing reagent that reports on RNA folding in a defined cellular compartment at a defined moment in time.</p>
<p>The payoff came in a mouse xenograft model. The researchers implanted HEK293T cells expressing mitochondria-targeted PRADA into immunodeficient mice, then administered D-amino acids and phenol probes systemically. Labeling proceeded efficiently inside the tumors in living animals. Proteomic analysis recovered the expected mitochondrial proteome, transcriptomic enrichment captured mitochondrial RNAs with high specificity, and PRADA-MaPseq yielded the first in vivo structurome of mitochondrial RNA within a living mammalian tumor. Comparing these in vivo structure maps with in vitro measurements of the same transcripts revealed systematic differences — evidence that RNA folding inside a living organism is actively shaped by its environment rather than being a fixed property of the sequence.</p>
<p>Those differences carried biological meaning. The team focused on LRPPRC, a mitochondrial RNA-binding protein known to organize the folding of the mitochondrial transcriptome. When they knocked down LRPPRC in the xenografts, changes in RNA structure propagated to changes in mitochondrial gene expression, demonstrating that RNA architecture functions as a regulatory layer controlling how mitochondrial genes are read. This finding elevates the structurome from a descriptive atlas to a mechanistic insight: the three-dimensional shapes of RNAs inside mitochondria help determine how much protein the organelle makes, and those shapes are tunable in vivo.</p>
<p>Beyond mitochondria, the breadth of validated applications suggests PRADA could become a workhorse across biology. The team demonstrated labeling in the cytoplasm and nuclei of body wall muscle cells in Caenorhabditis elegans, recovering nuclear-enriched transcripts and detecting retained introns as expected; in rat neurons and Drosophila; and in zebrafish. Because the trigger molecule — a simple D-amino acid — is cell-permeable, inexpensive and largely inert, the method should scale to tissues and organisms where peroxide bolus delivery is impractical, such as dense neural tissue, developing embryos or intact tumors. The authors have filed patent applications, and the analysis code for RNA structuromics is freely available on GitHub under an MIT license, with sequencing and proteomic data deposited in public repositories.</p>
<p>Limitations remain, as with any new technology. The labeling window is measured in tens of minutes rather than seconds, so fast molecular events may still escape capture. The peroxidase chemistry, while gentler than exogenous peroxide, still relies on radical intermediates whose diffusion radius sets the spatial resolution. And the D-amino acid oxidase must be carefully engineered for each fusion context to avoid perturbing the protein under study. Nevertheless, PRADA represents a genuine conceptual advance: it decouples proximity labeling from externally supplied oxidants, unifies protein, RNA and polymer chemistries under one enzymatic umbrella, and — for the first time — brings RNA structure mapping into living animals. If the platform generalizes as its developers hope, the spatial organization of biomolecules in health and disease may soon be readable not just in culture dishes, but in the bodies of living organisms, one D-amino acid at a time.</p>
<p><strong>Subject of Research:</strong> An engineered D-amino-acid-activated peroxidase cascade for in vivo multiomic proximity labeling of proteins and RNA structures</p>
<p><strong>Article Title:</strong> Multiomic proximity labeling in vivo by D-amino-acid-activated peroxidase reaction</p>
<p><strong>Article References:</strong> Liu, J., Han, J., Wang, Y., Song, M., Zhu, J., Liang, Y., Chen, F., Liu, Z., Yan, X., Wang, Z., Peng, W., Tu, R., Zhang, Z., Zhong, B., Sun, H., Yin, J., Chang, J., Long, Y., Men, Y., &#8230; Han, S. (2026). Multiomic proximity labeling in vivo by D-amino-acid-activated peroxidase reaction. <em>Nature Chemical Biology</em>. <a href="https://doi.org/10.1038/s41589-026-02336-5" rel="noopener noreferrer">https://doi.org/10.1038/s41589-026-02336-5</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1038/s41589-026-02336-5" rel="noopener noreferrer">10.1038/s41589-026-02336-5</a></p>
<p><strong>Keywords:</strong> proximity labeling, PRADA, D-amino acid oxidase, APEX2, RNA structure, structurome, mitochondria, spatial proteomics, chemical biology, in vivo imaging, xenograft, LRPPRC</p>
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		<title>Elizabeth Hillman Appointed Chair of Imaging Sciences at St. Jude</title>
		<link>https://scienmag.com/elizabeth-hillman-appointed-chair-of-imaging-sciences-at-st-jude/</link>
		
		<dc:creator><![CDATA[Harold Sullivan]]></dc:creator>
		<pubDate>Wed, 22 Jan 2025 19:23:53 +0000</pubDate>
				<category><![CDATA[Chemistry]]></category>
		<category><![CDATA[biomedical engineering]]></category>
		<category><![CDATA[Child Health Care]]></category>
		<category><![CDATA[Elizabeth Hillman]]></category>
		<category><![CDATA[High-Speed Microscopy]]></category>
		<category><![CDATA[Imaging Sciences]]></category>
		<category><![CDATA[In-Vivo Imaging]]></category>
		<category><![CDATA[Medical Imaging]]></category>
		<category><![CDATA[National Academy of Inventors]]></category>
		<category><![CDATA[Pediatric Medicine]]></category>
		<category><![CDATA[Scientific Research]]></category>
		<category><![CDATA[St. Jude Children's Research Hospital]]></category>
		<category><![CDATA[Technology Innovation]]></category>
		<guid isPermaLink="false">https://scienmag.com/elizabeth-hillman-appointed-chair-of-imaging-sciences-at-st-jude/</guid>

					<description><![CDATA[St. Jude Children&#8217;s Research Hospital has recently made significant strides by appointing Elizabeth M.C. Hillman, PhD, as the founding chair of its newly established Department of Imaging Sciences. This cutting-edge department aims to foster a flourishing community of technological innovators dedicated to enhancing the understanding of catastrophic childhood diseases. The training and expertise of Hillman [&#8230;]]]></description>
										<content:encoded><![CDATA[<p>St. Jude Children&#8217;s Research Hospital has recently made significant strides by appointing Elizabeth M.C. Hillman, PhD, as the founding chair of its newly established Department of Imaging Sciences. This cutting-edge department aims to foster a flourishing community of technological innovators dedicated to enhancing the understanding of catastrophic childhood diseases. The training and expertise of Hillman as a prominent figure in imaging method development provide an excellent basis for a leap forward in imaging technologies applied to life-saving research.</p>
<p>Hillman’s appointment is rooted in her remarkable history as a pioneer in the field of imaging. She holds an impressive track record in developing high-speed microscopes and advanced in-vivo imaging systems for studying living tissues. Under her leadership, a range of talented faculty members is expected to join the department, collectively driving the advancement of imaging techniques that span from microscopic imaging at the sub-cellular scale to comprehensive medical imaging processes. This diverse expertise will ideally enhance scientific studies while simultaneously improving patient care outcomes.</p>
<p>The establishment of this department is a clear indication of St. Jude’s commitment to innovation in biomedical research, especially focused on children. “Elizabeth is a renowned physicist, gifted biomedical engineer, and prolific inventor of new technologies,” remarked James R. Downing, MD, the president and CEO of St. Jude Children&#8217;s Research Hospital. The ambitious vision involves not merely building a functional department but rather creating a hub of excellence that integrates cutting-edge imaging technology into multidisciplinary research and clinical applications for children experiencing severe health challenges.</p>
<p>One of the primary objectives of this new department will be to develop and refine imaging and measurement methodologies that can facilitate transformative scientific studies. By leveraging advanced imaging technologies, researchers will likely better grasp disease processes and treatment outcomes, creating pathways for groundbreaking innovations in patient care. Hillman’s deep-rooted beliefs regarding the synergy between environment and innovation underscore the importance of St. Jude’s unique collaborative landscape. She acknowledges that local collaborations and shared scientific inquiries have significantly influenced her creative endeavors throughout her career.</p>
<p>Prior to joining St. Jude, Hillman made remarkable contributions during her tenure at Columbia University, serving as both a Herbert and Florence Irving Professor and a tenured professor in biomedical engineering and radiology. Her extensive 20-year career is marked by the successful development and application of a wide array of novel imaging and data analysis methods. These methods have not only advanced scientific inquiry but have also paved the way for potential commercial applications, evidenced by technologies she developed that have been licensed to major industry players like PerkinElmer and Leica Microsystems.</p>
<p>The broader implications of Hillman’s appointment extend beyond mere technological advancements. J. Paul Taylor, MD, PhD, St. Jude&#8217;s executive vice president and scientific director, articulated the revolutionary potential of recent advances in visualization and quantification methodologies. This revolutionary potential is expected to catalyze significant improvements in biomedical research specifically tailored to combating childhood diseases. Therefore, St. Jude’s commitment to propelling the institution forward in biomedical imaging innovation could manifest profound benefits for children diagnosed with life-threatening illnesses.</p>
<p>As Hillman transitions into her new role, she emphasizes the unique combination of talent and passion present at St. Jude, which she considers to be critical in addressing some of the most challenging questions in child health. The hospital&#8217;s environment presents a stimulating atmosphere where facilitators of scientific discovery can collaborate toward shared goals, maximizing the impact of their findings in real-time patient care. Hillman asserts that working in an inspiring environment like St. Jude will foster creativity and significantly heighten the immediate impacts of innovative discoveries.</p>
<p>Hillman’s academic pedigree includes a PhD in medical physics and bioengineering from University College London, one of the leading institutions known for driving scientific advancements. Furthermore, her post-doctoral work at the Martinos Center for Biomedical Engineering, affiliated with Massachusetts General Hospital and Harvard Medical School, provided her with foundational expertise in biomedical engineering, focusing on imaging sciences. She has authored over 100 research papers featured in esteemed journals such as Science, Nature Methods, Nature Photonics, and Nature Biomedical Engineering, showcasing her prominent role in advancing the field.</p>
<p>Moreover, Hillman has made substantial contributions to augmenting the scientific community’s understanding of critical biological processes and disease mechanisms. Her work reflects a synthesis of theory and applied sciences, which illustrates the value of interdisciplinary collaboration in driving biomedical progress. As a testament to her innovative contributions, she holds over 20 issued patents and was elected to the National Academy of Inventors in 2022. This remarkable recognition underscores her dedication to fostering an environment rich in innovation and invention, ensuring young researchers also have the opportunities to thrive within this dynamic landscape.</p>
<p>St. Jude Children&#8217;s Research Hospital has solidified its position as a preeminent institution in transforming how childhood diseases are understood, treated, and cured. With a unique focus as the only National Cancer Institute-designated Comprehensive Cancer Center exclusively dedicated to children, the hospital has played a critical role in improving pediatric treatment outcomes over its 60-plus-year history. Specifically, the treatment advancements achieved at St. Jude have propelled the childhood cancer survival rate from a mere 20% to 80%, representing a drastic shift and a beacon of hope for countless families across the globe.</p>
<p>Notably, the breakthroughs generated at St. Jude do not remain confined within its walls. The institution is deeply committed to sharing its discoveries, allowing healthcare providers worldwide to enhance treatment quality and care for children suffering from life-threatening conditions. Whether through its digital platforms or social media presence, St. Jude actively engages in disseminating vital knowledge that can have a lasting influence on partners in the healthcare community. </p>
<p>As the new Department of Imaging Sciences embarks on its groundbreaking journey under Hillman’s leadership, it signifies not just a commitment to scientific advancement but also a profound dedication to the lives of the children it serves. By uniting cutting-edge technology with a comprehensive understanding of pediatric diseases, the collaborative efforts within this department could redefine the contours of research excellence at the intersection of imaging and healthcare, ultimately transforming the future landscape of pediatric medicine for generations to come.</p>
<p><strong>Subject of Research</strong>: Imaging and Measurement Approaches in Pediatric Medicine<br />
<strong>Article Title</strong>: Elizabeth Hillman Appointed Founding Chair of St. Jude’s Imaging Sciences Department<br />
<strong>News Publication Date</strong>: October 2023<br />
<strong>Web References</strong>: <a href="https://www.stjude.org/">St. Jude Children&#8217;s Research Hospital</a><br />
<strong>References</strong>: N/A<br />
<strong>Image Credits</strong>: Credit: St. Jude Children&#8217;s Research Hospital  </p>
<h4><strong>Keywords</strong></h4>
<p>Imaging, Biomedical Engineering, Pediatric Medicine, High-Speed Microscopy, In-Vivo Imaging, Technology Innovation, Scientific Research, Child Health Care, Imaging Sciences, Medical Imaging.</p>
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