Despite their promise, XFEL experiments have been notoriously sample-hungry, requiring vast amounts of precious protein material. Traditional methods inject a continuous stream of protein crystals into the beam, but most are wasted since only a fraction aligns with the pulsed laser at any given time. This inefficiency restricts dynamic structural studies to abundant proteins and excludes many that are rare, fragile, or difficult to produce at scale. Addressing this bottleneck, a team led by Alexandra Ros at Arizona State University, along with international collaborators including the Consejo Superior de Investigaciones Científicas (CSIC), has engineered a breakthrough microfluidic device that slashes sample consumption by as much as 97% without sacrificing data quality.

The innovation centers on a microfluidic droplet injector, an elegantly designed system that dispenses protein crystals not in a continuous stream but as precisely timed micrometer-scale droplets. These droplets are synchronized perfectly with XFEL pulses, ensuring protein crystals are introduced exactly when the X-ray beam probes their structure. This targeted delivery maximizes the utility of every protein crystal, fundamentally transforming how time-resolved serial crystallography experiments are conducted. The device incorporates advanced 3D printing techniques to fabricate intricate fluid channels that mix solutions and generate droplets on demand—compatible with the lightning-fast repetition rates of modern XFELs.

This technology sets the stage for dynamic studies of medically important proteins that were previously inaccessible due to sample volume constraints. Researchers demonstrated the device’s capabilities at the European XFEL facility by resolving the early redox cycle of human NAD(P)H:quinone oxidoreductase 1 (NQO1), a key enzyme involved in cellular detoxification and oxidative stress defense. By capturing snapshots of NQO1 binding its cofactor NADH in real time, they revealed critical details about molecular interactions driving enzymatic activity. The insight into cofactor dynamics provided by time-resolved crystallography could shed light on disease mechanisms and inform precision drug design.

The impact of such minimal sample consumption extends far beyond this one enzyme. Many proteins implicated in disease pathways or industrial biocatalysis are challenging or costly to produce in high yield. This microfluidic injector lowers the barrier for structural investigations of these elusive molecules’ timed behavior. Facilities equipped with XFELs can now expand their scope to encompass fragile and low-abundance proteins without prohibitive protein waste, democratizing access to dynamic structural biology experiments across the scientific community. Scientists anticipate that this method will accelerate both fundamental research and therapeutic innovation.

Technically, the microfluidic injection system operates by generating a stable “train” of droplets approximately tens of microns in diameter. Each droplet encapsulates a microcrystal slurry and travels through microscale channels etched into the device before arriving at the intercept point with the XFEL beam. The droplet timing is meticulously adjusted and synchronized with pulse sequences typically in the kilohertz to megahertz range of modern X-ray lasers, ensuring maximal hit rates with minimal idle exposure. This mode of sample delivery contrasts sharply with traditional continuous liquid jets, which squander up to 99% of protein samples.

By enabling time-resolved serial femtosecond crystallography with greatly reduced sample volumes, this technology also helps unlock the full potential of next-generation X-ray laser facilities. Upcoming XFELs promise higher repetition rates and brighter pulses, but such improvements come with challenges of sample delivery and data acquisition. The droplet injector design is well suited to meet these demands, offering scalable throughput and compatibility with compact, laboratory-scale XFEL sources under development, such as the Biodesign Institute’s compact X-ray free-electron laser (CXFEL).

The conceptual advance embodied by this work not only solves a major practical impediment but also enriches the study of conformational heterogeneity and reaction intermediates in proteins. By capturing transient states during enzymatic cycles or ligand binding events with unprecedented precision and minimal resource use, it paves the way for discoveries in molecular mechanisms that underlie health and disease. This could facilitate the design of drugs targeting fleeting but functionally critical protein states, a frontier in rational drug development. Moreover, the method’s compatibility with automated workflows promises to speed up data throughput while reducing experimental costs.

Lead researcher Alexandra Ros underscores the transformative potential of this approach: “Seeing proteins react in real time is incredibly powerful, but the sample demands to unravel dynamic protein behavior with X-ray crystallography have been a major limitation. Our droplet approach dramatically reduces that burden, which is exciting because many more labs can now ask dynamic questions that were previously too costly or impractical.” Her team’s work represents a milestone in structural biology, enabling real-time visualization of biochemical pathways at atomic resolution with extraordinary sample efficiency.

In summary, the microfluidic droplet injector designed by ASU researchers addresses one of the physics and biology communities’ key challenges by marrying cutting-edge fluidics with ultrafast X-ray science. It sharply reduces protein consumption in XFEL experiments, unlocks access to rare and valuable proteins, and expands the horizon for time-resolved molecular studies. This technological leap not only enriches our fundamental comprehension of protein dynamics but also holds promise to accelerate drug discovery and biotechnological innovation by providing a clearer window into the molecular machinery of life. As XFEL technology continues to evolve, such innovations in sample delivery will be indispensable for maximizing scientific returns from these colossal instruments.

Subject of Research: Time-resolved serial crystallography of human enzyme NQO1 using microfluidic droplet injector technology

Article Title: Minimized sample consumption for time-resolved serial crystallography applied to the redox cycle of human NQO1

News Publication Date: 29-Jan-2026

Web References:
http://dx.doi.org/10.1038/s42004-026-01908-9

Image Credits: The Biodesign Institute at ASU

Keywords

Applied sciences and engineering, Life sciences, Biochemistry, Biomolecules, Protein crystals, Protein structure, Protein subunits, Protein interactions, Applied physics, Accelerator physics

To improve the utility of cryo-ET, researchers often employ a method called cryo-focused ion beam (FIB) milling. This technique is used to thin frozen specimens into cryo-lamellae that are less than 500 nanometers thick, thereby enhancing their suitability for electron tomography. However, a major hurdle remains: the difficulty of precisely locating regions of interest within these thin samples. Untargeted milling can inadvertently lead to the ablation of areas that hold vital biological information, complicating subsequent imaging efforts.

The integration of correlative light and electron microscopy (CLEM) with cryo-FIB milling has emerged as a solution to this pressing issue. By combining these techniques, researchers can utilize fluorescence microscopy to pinpoint labeled targets within the cellular context before applying FIB milling. This correlation allows for more accurate milling, ultimately preserving critical regions that are essential for studying cellular processes. However, the workflow frequently necessitates multiple transfers between different cryo-imaging instruments, which introduces significant challenges. These include cumbersome correlation algorithms, low accuracy, and diminished throughput, all of which have hindered the widespread application of cryo-FIB milling in structural biology.

To address these challenges head-on, a new integrated workflow has been proposed, blending 3D correlative cryo-fluorescence light microscopy with FIB-ET. This innovative approach not only streamlines the process of fluorescence microscopy-guided FIB milling but also significantly improves the throughput by minimizing inefficiencies in the workflow. By enhancing the accuracy of targeting during cryo-milling and maintaining structural integrity, this method represents a transformative leap in the field of in situ structural biology.

One of the key advancements of this new workflow is the integration of hardware and software components that reduce the risk of sample contamination during cross-platform exchanges. This enhanced efficiency is crucial for ensuring precise targeting of the sample, which is vital when aiming to visualize specific macromolecules within their native surroundings. The ability to seamlessly transition between imaging modalities without compromising sample integrity opens the door to a more coherent and reliable correlative approach in structural studies.

Researchers have also developed a technique known as montage parallel array cryo-ET (MPACT), designed to facilitate high-throughput cryo-ET acquisitions. MPACT can be implemented on any modern life-science transmission electron microscope and supports rapid data acquisition—allowing for ten tilt series to be collected in just 1.5 hours. This speed is a game changer for researchers aiming to discern structural details in a timely manner, as it combines efficiency with high-quality results.

In practical terms, a complete workflow session—from sample preparation to MPACT data processing—can typically be conducted within five to seven days by an experienced researcher familiar with both cryo-electron microscopy and cryo-FIB milling. This relatively rapid timeline enhances the feasibility of integration in routine laboratory settings, meaning that researchers can conduct experiments and obtain results quicker than before.

This workflow not only promotes a higher throughput for data collection but also preserves the vital contextual information that is often lost with traditional techniques. By ensuring that critical biological features are retained during the milling and imaging processes, scientists can obtain a more comprehensive understanding of cellular architecture. This advancement has the potential to propel structural biology forward, allowing for new discoveries in areas ranging from cellular signaling to the development of new therapeutics.

As this innovative approach gains traction, it may pave the way for breakthroughs in a variety of biological research fields. For instance, the ability to visualize protein interactions in their natural contexts may yield invaluable insights into cellular mechanisms, disease pathways, and even the development of novel drugs. The preservation of structural and contextual integrity makes this methodology not just a technical advancement but a crucial step towards breakthroughs in molecular biology.

Furthermore, the ongoing evolution of imaging technologies and methodologies like MPACT is indicative of the scientific community’s commitment to refining and enhancing our understanding of life’s molecular underpinnings. As more researchers adopt these advanced techniques, we can expect a rapid acceleration in knowledge, further unraveling the complex tapestry of biology.

The future of cryogenic-electron tomography and correlative methodologies looks promising. The ongoing integration of innovative technologies and techniques signals a bright horizon for structural biology. By improving imaging capabilities and enhancing precision in sample preparation and analysis, researchers are poised to explore new frontiers in biological sciences. As we continue to build on these advances, we move closer to unlocking the secrets hidden within the cellular milieu, paving the way for groundbreaking discoveries in health and disease.

Overall, the collaborative work being done in the fields of cryogenic-em and structural biology exemplifies the intersection of creativity and technological prowess. As researchers share their findings and refine existing techniques, we can anticipate not only a better understanding of complex biological systems but also the development of new tools and methods that will shape the future of scientific inquiry.

This evolving landscape is testament to the power of interdisciplinary research, as experts in microscopy, molecular biology, and imaging technology come together to tackle pressing scientific questions. The implications of these innovations extend far beyond individual lab settings, offering the potential for groundbreaking transformations in our approach to biological research and beyond.

We are at the cusp of a new era in structural biology, where the confluence of advanced imaging techniques and innovative sample preparation methods will allow scientists to visualize cellular processes with unprecedented clarity. As we look ahead, the integration of correlative cryo-ET and MPACT may well redefine how we investigate and interact with the building blocks of life itself.

Subject of Research: Cryogenic-electron tomography and cryo-focused ion beam milling in structural biology.

Article Title: Integrated fluorescence light microscopy-guided cryo-focused ion beam-milling for in situ montage cryo-ET.

Article References:

Yang, J.E., Vrbovská, V., Mitchell, J.M. et al. Integrated fluorescence light microscopy-guided cryo-focused ion beam-milling for in situ montage cryo-ET.
Nat Protoc (2026). https://doi.org/10.1038/s41596-025-01284-z

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41596-025-01284-z

Keywords: cryogenic-electron tomography, cryo-focused ion beam milling, correlative light and electron microscopy, molecular biology, high-throughput imaging.

Conventional super-resolution techniques, including STED, SIM, and SMLM, offer remarkable resolution under optimal conditions yet struggle as imaging depth increases. STED microscopy relies on a doughnut-shaped depletion beam whose spatial integrity is compromised by tissue scattering, undermining resolution. SIM’s dependence on structured stripe illumination patterns makes it vulnerable to distortion and artifacts when photons scatter. SMLM, while powerful for localizing single molecules, suffers from poor localization accuracy in environments rife with background fluorescence and optical aberrations. These limitations have restricted their efficacy in thick biological tissues, which are opaque and highly scattering.

Image Scanning Microscopy (ISM), an evolution of confocal microscopy, enhances spatial resolution by approximately twofold beyond the diffraction limit through pixel reassignment and deconvolution techniques. However, ISM’s conventional implementations encounter inherent constraints—particularly a compromise between spatial and temporal resolution during data acquisition, impeding its applicability in live or volumetric deep-tissue studies. Addressing this, the research team previously introduced Multi-Confocal ISM (MC-ISM), improving temporal resolution but still contending with background interference and fidelity reduction at significant depths.

The newly introduced C²SD-ISM pushes these boundaries by integrating a spinning-disk confocal microscope with a digital micromirror device (DMD) and a sophisticated adaptive reconstruction algorithm named dynamic pinhole array pixel reassignment (DPA-PR). This dual-confocal architecture physically filters out-of-focus fluorescence through the spinning disk, establishing the first confocal layer, effectively enhancing optical sectioning and mitigating background noise at the hardware level. Simultaneously, the DMD projects sparse multifocal excitation patterns, enabling efficient spatial encoding vital for the second confocal layer powered by the DPA-PR computational engine.

Unlike conventional ISM reconstruction algorithms that assume idealized Gaussian excitation and detection point spread functions (PSFs), C²SD-ISM confronts real-world complexities head-on. Systemic aberrations and the ubiquitous Stokes shift—differences between excitation and emission wavelengths—distort PSF profiles, undermining reconstruction accuracy. The DPA-PR algorithm innovatively constructs a virtual 5×5 detector array from subsets of raw image stacks by extracting multiple offset sub-images. Spatial offsets are precisely quantified using phase cross-correlation methods, allowing for high-fidelity reassignment that preserves structural integrity and brightness linearity within reconstructed images.

Demonstrating formidable prowess, C²SD-ISM achieves lateral resolution down to 144 nanometers within dense tissue specimens—a substantial improvement over standard confocal microscopy. This precision is maintained even in heavily scattering environments, as validated using mouse kidney tissue sections. The system’s capability to maintain high visibility of excitation foci under dense multifocal excitation patterns is critical, substantiated by comparative analyses showing superior local contrast and reduced computation overhead, requiring six times fewer raw images than conventional multifocal structured illumination microscopy (MSIM).

One of the standout features of C²SD-ISM lies in its volumetric imaging capabilities. The technology facilitates three-dimensional reconstructions over volumes as large as 66.5 × 66.5 × 12 micrometers with axial step sizes as fine as 150 nanometers. This fine sampling preserves exquisite detail and spatial continuity across complex cellular architectures. The application to EGFP-labeled zebrafish vasculature exemplifies its scalability and robustness. Over a mosaic volume reaching nearly 3 millimeters in lateral dimensions, the system delivers markedly enhanced spatial resolution compared to conventional confocal microscopy, revealing delicate vascular networks with unprecedented clarity.

Further expanding its versatility, C²SD-ISM leverages the DMD’s programmability to perform projection-based Structured Illumination Microscopy, addressing key SIM limitations in thick tissues. The spinning disk’s physical rejection of out-of-focus fluorescence dramatically improves stripe modulation contrast, permitting 3D imaging of fungal samples to depths and resolutions unattainable by traditional SIM approaches. Achieving approximately a 1.68-fold resolution enhancement, this mode breaks the longstanding depth barrier, facilitating detailed volumetric observation in optically challenging samples.

C²SD-ISM’s elegant synergy of hardware optimization and intelligent algorithm design culminates in an imaging platform that harmonizes resolution enhancement, imaging depth penetration, and signal fidelity. This triumvirate is critical for advancing biological microscopy beyond its conventional boundaries, enabling more reliable investigations of cellular and tissue-scale phenomena. Moreover, the system’s high throughput, multicolor capabilities, and adaptability render it an exceptionally practical tool for diverse research domains, from neurobiology to developmental biology and pathology.

Forecasting future developments, the research team envisions augmenting C²SD-ISM with deep learning algorithms for denoising and adaptive optics for aberration correction. Such integrations could unlock even deeper penetration depths and larger volumetric datasets with minimized phototoxicity. Particularly, the adaptive illumination strategies enabled by DMD programmability open avenues for real-time feedback-controlled microscopy—ushering in ‘intelligent’ imaging platforms that minimize photodamage while maximizing information throughput during live-cell or in vivo studies.

A testament to its technological maturity and industrial applicability, elements of the C²SD-ISM framework have already been commercialized in the Nova-SD spinning-disk confocal system. This commercial instrument boasts native lateral resolutions around 230 nanometers, exceptionally high imaging speeds reaching 2000 frames per second, seven-channel excitation options, and expansive fields of view up to 25 millimeters, underscoring the practical impact of this research on mainstream biological imaging.

In the spirit of open science, the researchers have made critical components freely available, including simulation codes for artifact-free spinning-disk imaging, mask designs for disk fabrication, super-resolution reconstruction software for multifocal excitation leveraging DPA-PR, and comprehensive hardware control packages. This commitment facilitates global collaboration and accelerates adoption across imaging centers worldwide, ensuring that C²SD-ISM’s benefits extend beyond the originating lab.

By surmounting entrenched obstacles to deep tissue super-resolution imaging, the Confocal² Spinning-Disk Image Scanning Microscopy stands poised to revolutionize optical microscopy. Its capacity to deliver unprecedented resolution and fidelity at significant depths, coupled with efficient data acquisition and adaptability, heralds a new chapter for biomedical research—empowering scientists to unravel the complexities of life with clarity and precision previously thought unattainable.

Subject of Research: Advanced optical microscopy techniques for super-resolution imaging in complex biological tissues

Article Title: High-fidelity tissue super-resolution imaging achieved with confocal² spinning-disk image scanning microscopy

Web References: https://doi.org/10.1038/s41377-025-01930-x

Image Credits: Liang, Q., Ren, W., Jin, B. et al.

Keywords

Optics, Super-resolution microscopy, Confocal microscopy, Spinning-disk microscopy, Digital micromirror device, Image scanning microscopy, Deep tissue imaging, Adaptive optics, Structured illumination microscopy