Background and purpose: – Artificial intelligence (AI) is increasingly being applied to automate image interpretation, including in coronary optical coherence tomography (OCT), the gold standard for in vivo assessment of atherosclerotic plaques. Most AI models are trained using expert annotations; however, human interpretation is inherently subjective and may limit model performance. Therefore, validation against the true reference standard—histology—remains essential. The study aims to evaluate and compare the performance of an AI-powered plaque characterization model with that of clinicians, using co-registered histology as the reference standard. Methods: – Matched OCT pullbacks and serial histological sections from 25 plaques in 11 swine atherosclerotic arteries were analyzed. Precise OCT–histology co-registration was achieved using a hierarchical coarse-to-fine approach, with stent edges and anatomical landmarks as references. Plaque components (fibrous, lipidic, and calcific) were manually labeled on histology and automatically segmented on OCT by the AI model. Meanwhile, three blinded readers with different levels of OCT expertise independently annotated the corresponding frames. The relative percentages of plaque components derived from OCT were compared with histology. Results: – Across all histological sections, the median percentages of fibrous, lipidic, and calcific components were 65.0% (interquartile range [IQR]: 53.9%–92.5%), 34.3% (IQR: 6.5%–44.7%), and 0.2% (IQR: 0%–1.9%), respectively. The AI model demonstrated excellent correlation with histology, with Spearman’s ρ = 0.907 (P < 0.001) for fibrous and ρ = 0.900 (P < 0.001) for lipidic components. The mean absolute discrepancy relative to histology was comparable between the AI model and the senior reader and smaller than that of the intermediate and junior readers. Agreement with histology improved with reader’s experience (fibrous: intraclass correlation coefficients [ICC] = 0.666, 0.720, and 0.821; lipidic: ICC = 0.593, 0.684, and 0.803), yet remained lower than that of the AI model (fibrous: ICC = 0.938; lipidic: ICC = 0.939). Conclusions: – Despite being trained on human-annotated data, the AI model demonstrated superior agreement with histology compared with clinicians. AI-driven plaque characterization may reduce interpretative subjectivity and enhance the clinical utility of coronary OCT in the management of coronary artery disease.

Background: Ex vivo vascular bioreactors that enable interventions in arteries from slaughterhouse surplus hearts present valuable alternatives to animal models to test cardiovascular stents. However, the knowledge for stent implantation during ex vivo culture in slaughterhouse coronary arteries is limited. The objective of the study is two-fold: first, to determine culture settings, the time point and optimal conditions for in-culture stent implantation using surplus right coronary arteries (RCAs) from swine with known in vivo RCA diameters; and second, to implement the gained insights to culture and stent RCAs obtained from slaughterhouse hearts (unknown in vivo diameter). Methods: Swine RCAs were mounted, cultured and stented in an ex vivo vascular bioreactor (VABIO) under conditions of flow and pressure. The bioreactor culture and stenting protocols were optimized using a step wise approach. In Step 1, the RCAs dissected from in-house swine hearts, with known diameters, were cultured until endothelialized as the ideal time point for stenting, and the stent implantation procedure was optimized. In Step 2, the successful ex vivo stent implantation procedure was repeated in slaughterhouse RCAs. Structural changes of the RCAs were assessed by ultrasound imaging during culture. The morphology of the RCAs at the end of culture was assessed by histology. Results: The RCAs adapted to the ex vivo environment, stabilizing their diameter in the range of the in vivo diameter after day 3, which was selected as the earliest time point for stenting. Because stent implantations caused mural dissections in the RCAs, visible with ultrasound imaging and confirmed by histology, we developed an external support for the RCA. This was found to be critical for better physiological intravascular pressures and to minimize dissections upon stent implantation. Finally, the stent implantation procedure was successfully replicated in slaughterhouse arteries. Conclusions: Our study demonstrates the feasibility of in-culture ex vivo stent implantation in the VABIO, providing important requirements and useful insights for in vivo mimicking stent implantation, for future investigations in slaughterhouse arteries.

Coronary atherosclerosis is caused by plaque build-up, with lipids playing a pivotal role in its progression. However, lipid composition and distribution within coronary atherosclerosis remain unknown. This study aims to characterize lipids and investigate differences in lipid composition across disease stages to aid in the understanding of disease progression. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to visualize lipid distributions in coronary artery sections (n ¼ 17) from hypercholesterolemic swine. We performed histology on consecutive sections to classify the artery segments and to investigate colocalization between lipids and histological regions of interest in advanced plaque, including necrotic core and inflammatory cells. Segments were classified as healthy (n ¼ 6), mild (n ¼ 6), and advanced disease (n ¼ 5) artery segments. Multivariate data analysis was employed to find differences in lipid composition between the segment types, and the lipids' spatial distribution was investigated using non-negative matrix factorization (NMF). Through this process, MALDI-MSI detected 473 lipid-related features. NMF clustering described three components in positive ionization mode: triacylglycerides (TAG), phosphatidylcholines (PC), and cholesterol species. In negative ionization mode, two components were identified: one driven by phosphatidylinositol(PI)(38:4), and one driven by ceramidephosphoethanolamine(36:1). Multivariate data analysis showed the association between advanced disease and specific lipid signatures like PC(O-40:5) and cholesterylester(CE)(18:2). Ether-linked phospholipids and LysoPC species were found to colocalize with necrotic core, and mostly CE, ceramide, and PI species colocalized with inflammatory cells. This study, therefore, uncovers distinct lipid signatures correlated with plaque development and their colocalization with necrotic core and inflammatory cells, enhancing our understanding of coronary atherosclerosis progression.

Polydimethylsiloxane (PDMS) is one of the materials of choice for the fabrication of microfluidic chips. However, its broad application is constrained by its incompatibility with common organic solvents and the absence of surface anchoring groups for surface functionalization. Current solutions involving bulk-, ex-situ surface-, and in-situ liquid phase modifications are limited and practically demanding. In this work, we present a simple, novel strategy to deposit a metal oxide nano-layer on the inside of bonded PDMS microfluidic channels using atmospheric pressure atomic layer deposition (AP-ALD). Using three important classes of microfluidic experiments, i.e., (i) the production of micron-sized particles, (ii) the cultivation of biological cells, and (iii) the photocatalytic degradation in continuous flow chemistry, we demonstrate that the metal oxide nano-layer offers a higher resistance against organic solvent swelling, higher hydrophilicity, and a higher degree of further functionalization of the wall. We demonstrate the versatility of the approach by not only depositing SiO_x nano-layers, but also TiO_x nano-layers, which in the case of the flow chemistry experiment were further functionalized with gold nanoparticles through the use of AP-ALD. This study demonstrates AP-ALD as a tool to broaden the applicability of PDMS devices.

The production of base chemicals by electrochemical conversion of captured CO₂ has the potential to close the carbon cycle, thereby contributing to a future energy transition. With the feasibility of low-temperature electrochemical CO₂ conversion demonstrated at lab scale, research is shifting toward optimizing electrolyser design and operation for industrial applications, with target values based on techno-economic analysis. However, current techno-economic analyses often neglect experimentally reported interdependencies of key performance variables such as the current density, the faradaic efficiency, and the conversion. Aiming to understand the impact of these interdependencies on the economic outlook, we develop a model capturing mass transfer effects over the channel length for an alkaline, membrane electrolyser. Coupling the channel scale with the higher level process scale and embedding this multiscale model in an economic framework allows us to analyze the economic trade-off between the performance variables. Our analysis shows that the derived target values for the performance variables strongly depend on the interdependencies described in the channel scale model. Our analysis also suggests that economically optimal current densities can be as low as half of the previously reported benchmarks. More generally, our work highlights the need to move toward multiscale models, especially in the field of CO₂ electrolysis, to effectively elucidate current bottlenecks in the quest toward economically compelling system designs.

Safety and efficacy of coronary drug-eluting stents (DES) are often preclinically tested using healthy or minimally diseased swine. These generally show significant fibrotic neointima at follow-up, while in patients, incomplete healing is often observed. The aim of this study was to investigate neointima responses to DES in swine with significant coronary atherosclerosis. Adult familial hypercholesterolemic swine (n = 6) received a high fat diet to develop atherosclerosis. Serial OCT was performed before, directly after, and 28 days after DES implantation (n = 14 stents). Lumen, stent and plaque area, uncovered struts, neointima thickness and neointima type were analyzed for each frame and averaged per stent. Histology was performed to show differences in coronary atherosclerosis. A range of plaque size and severity was found, from healthy segments to lipid-rich plaques. Accordingly, neointima responses ranged from uncovered struts, to minimal neointima, to fibrotic neointima. Lower plaque burden resulted in a fibrotic neointima at follow-up, reminiscent of minimally diseased swine coronary models. In contrast, higher plaque burden resulted in minimal neointima and more uncovered struts at follow-up, similarly to patients’ responses. The presence of lipid-rich plaques resulted in more uncovered struts, which underscores the importance of advanced disease when performing safety and efficacy testing of DES.

It is common practice in the development of bioprocesses to genetically modify a microorganism and study a large number of resulting mutants in order to select the ones that perform best for use at the industrial scale. At industrial scale, strict nutrient-controlled growth conditions are imposed to control the metabolic activity and growth rate of the microorganism, thereby enhancing the expression of the product of interest. Although it is known that microorganisms that perform best under these strictly controlled conditions are not the same as the ones that perform best under uncontrolled batch conditions, screening, and selection is predominantly performed under batch conditions. Tools that afford high throughput on the one hand and dynamic control over cultivation conditions on the other hand are not yet available. Microbioreactors offer the potential to address this problem, resolving the gap between bioprocess development and industrial scale use. In this review, we highlight the current state-of-the-art of microbioreactors that offer the potential to screen microorganisms under dynamically controlled conditions. We classify them into: (i) microtiter plate-based platforms, (ii) microfluidic chamber-based platforms, and (iii) microfluidic droplet-based platforms. We conclude this review by discussing the opportunities of nutrient-fed microbioreactors in the field of biotechnology.

Two decades of research on droplet formation in microchannels have led to the widely accepted view that droplets form through the squeezing mechanism when interfacial forces dominate over viscous forces. The initially surprising finding that the volume of the droplets is insensitive to the relative importance of these two forces is nowadays well understood from the constrained deformation of the droplet interface during formation. In this work, we show a lower limit of the squeezing mechanism for droplets produced in microfluidic cross-junctions. Below this limit, in the leaking regime, which was recently discovered for droplets produced in T-junctions, the volume of the produced droplets strongly depends on the relative importance of interfacial and viscous forces, as captured by the capillary number. We reveal a fundamental difference in the mechanisms at play in the leaking regime between T- and cross-junctions. In cross-junctions, the droplet neck elongates substantially, and unlike the case of the T-junction, the magnitude of this elongation depends strongly on the value of the capillary number. This elongation significantly affects the final droplet volume in a low capillary number regime. Generalizing the classical squeezing law by lifting the original assumptions and incorporating both identified mechanisms of leaking through gutters and neck elongation, we derive a model for droplet formation and show that it agrees with our experiments.

We explore three variants of atomic layer deposition (ALD) to deposit titanium oxide on the soft polymer polydimethylsiloxane (PDMS). We show that the organic solvent resistance of PDMS is increased by two orders of magnitude compared to uncoated PDMS for ALD performed at atmospheric pressure, which results in a unique surface-subsurface coating of PDMS.

Properties of powders produced from drying solute-containing droplets arise from the dynamic redistribution of solute during drying. While insights on the dynamic redistribution are instrumental for the rational design of powders and for the optimized operation of equipment such as spray dryers, experimental techniques that allow measuring the spatio-temporal concentration of solute in drying droplets are scarce. In this work, we explore and demonstrate the use of optical coherence tomography (OCT) to measure the spatio-temporal concentration of solute in drying droplets and the development of a solidifying shell at the liquid-air interface, using aqueous droplets of maltodextrin as a model system. This work provides a solid foundation for the use of OCT to quantify the dynamic redistribution of solute and link it to the development of the morphology of the produced particles and agglomerates.

Electrochemical reduction of CO₂using renewable energy is a promising avenue for sustainable production of bulk chemicals. However, CO₂electrolysis in aqueous systems is severely limited by mass transfer, leading to low reactor performance insufficient for industrial application. This paper shows that structured reactors operated under gas-liquid Taylor flow can overcome these limitations and significantly improve the reactor performance. This is achieved by reducing the boundary layer for mass transfer to the thin liquid film between the CO₂bubbles and the electrode. This work aims to understand the relationship between process conditions, mass transfer, and reactor performance by developing an easy-to-use analytical model. We find that the film thickness and the volume ratio of CO₂/electrolyte fed to the reactor significantly affect the current density and the faradaic efficiency. Additionally, we find industrially relevant performance when operating the reactor at an elevated pressure beyond 5 bar. We compare our predictions with numerical simulations based on the unit cell approach, showing good agreement for a large window of operating parameters, illustrating when the easy-to-use predictive expressions for the current density and faradaic efficiency can be applied.

Urine is commonly used for clinical diagnosis and biomedical research. The discovery of extracellular vesicles (EV) in urine opened a new fast-growing scientific field. In the last decade urinary extracellular vesicles (uEVs) were shown to mirror molecular processes as well as physiological and pathological conditions in kidney, urothelial and prostate tissue. Therefore, several methods to isolate and characterize uEVs have been developed. However, methodological aspects of EV separation and analysis, including normalization of results, need further optimization and standardization to foster scientific advances in uEV research and a subsequent successful translation into clinical practice. This position paper is written by the Urine Task Force of the Rigor and Standardization Subcommittee of ISEV consisting of nephrologists, urologists, cardiologists and biologists with active experience in uEV research. Our aim is to present the state of the art and identify challenges and gaps in current uEV-based analyses for clinical applications. Finally, recommendations for improved rigor, reproducibility and interoperability in uEV research are provided in order to facilitate advances in the field.

A key bottleneck in bioprocess development is that state-of-the-art tools used for screening of cells and optimization of cultivation conditions do not represent the conditions enforced at industrial scale. At industrial scale, cell growth is strictly controlled (“fed-batch”) to optimize the metabolites produced by the cells. In contrast, cell growth is uncontrolled (“batch”) in microwells commonly used for bioprocess development due to the difficulty to continuously supply minute amounts of nutrients to the cells in these wells over the course of the cultivation experiment. This work addresses this bottleneck through the development of a droplet-based fed-batch nanobioreactor. A key challenge addressed in this work is the implementation of the required non-steady droplet operations on chip to establish a semi-continuous nutrient supply, while keeping the chip and its operation as simple as possible. The ability to study micro-organisms under nutrient-controlled fed-batch conditions is demonstrated using the yeast Cyberlindnera (Pichia) jadinii, with the cell growth rate controlled through the glucose concentration. Given the relative ease of operation and the potential to extend its features, the presented nanobioreactor provides a solid platform technology for further development and use in the field of bioprocess development and beyond.

Sticking of particles has a tremendous impact on powder-processing industries, especially for hygroscopic amorphous powders. A wide variety of experimental methods has been developed to measure at what combinations of temperature and moisture content material becomes sticky. This review describes, for each method, how so-called stickiness curves are determined. As particle velocity also plays a key role, we classify the methods into static and dynamic stickiness tests. Static stickiness tests have limited particle motion during the conditioning step prior to the measurement. Thus, the obtained information is particularly useful in predicting the long-term behavior of powder during storage or in packaging. Dynamic stickiness tests involve significant particle motion during conditioning and measurement. Stickiness curves strongly depend on particle velocity, and the obtained information is highly relevant to the design and operation of powder production and processing equipment. Virtually all methods determine the onset of stickiness using powder as a starting point. Given the many industrial processes like spray drying that start from a liquid that may become sticky upon drying, future effort should focus on developing test methods that determine the onset of stickiness using a liquid droplet as a starting point.

Atherosclerotic arteries are commonly treated using drug-eluting stents (DES). However, it remains unclear whether and how the properties of atherosclerotic plaque affect drug transport in the arterial wall. A limitation of the currently used atherosclerotic animal models to study arterial drug distribution is the unpredictability of plaque size, composition, and location. In the present study, the aim is to create an artificial atherosclerotic plaque—of reproducible and controllable complexity and implantable at specific locations—to enable systematic studies on transport phenomena of drugs in stented atherosclerosis-mimicking arteries. For this purpose, mixtures of relevant lipids at concentrations mimicking atherosclerotic plaque are incorporated in gelatin/alginate hydrogels. Lipid-free (control) and lipid-rich hydrogels (artificial plaque) are created, mounted on DES and successfully implanted in porcine coronary arteries ex-vivo. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) is used to measure local drug distribution in the arterial wall behind the prepared hydrogels, showing that the lipid-rich hydrogel significantly hampers drug transport as compared to the lipid-free hydrogel. This observation confirms the importance of studying drug transport phenomena in the presence of lipids and of having an experimental model in which lipids and other plaque constituents can be precisely controlled and systematically studied.

The initial thickness and radius of the film that forms upon close contact of two foam bubbles are known to influence the thinning dynamics and lifetime of the film. Various scalings of lifetime tr, with initial radius Rfilm and thickness ho, have been proposed in literature. In this paper, we present a hydrodynamic thin-film model that includes both surface tension, van der Waals forces, and drainage and that clarifies the various proposed scalings of lifetime. Our model equations were solved numerically for a range of Rfilm and ho as direct input parameters. Films with a large radius are found to thin locally at a dimple, while films with a small radius thin across the entire film. The observed dynamics and lifetime were interpreted by developing a simplified model that describes the early stage dimpled drainage and the late stage van der Waals thinning, using known similarity solutions. For large radii films, our simulations confirm earlier theoretical work on semi-infinite films that predicts tr∼Rfilm0h05/7. For small radii films, our numerical simulations show the opposite trend with lifetime being solely dependent on Rfilm, in fair agreement with the simplified model that predicts tr∼Rfilm10/7h00.