Search Results (95)

Engineering volumetric three-dimensional tissues requires the rapid establishment of dense, capillary-like microchannels to ensure adequate oxygen and nutrient supply while preventing hypoxic cell necrosis. Sacrificial microfiber templating approaches using lower critical solution temperature (LCST) polymers cannot employ type I collagen hydrogels—a biologically ideal extracellular matrix—because LCST fiber dissolution in cold collagen solutions precedes matrix gelation owing to thermodynamic mismatch. Here, we present a proof-of-concept strategy to rapidly fabricate capillary-sized microchannels within collagen hydrogels using thermoresponsive, physically crosslinked gelatin microfibers as sacrificial templates. Three-dimensional gelatin microfibers with capillary-sized diameters (approximately 10 μm) were fabricated via wet spinning and embedded in a type I collagen aqueous solution (4 °C). Open microchannels throughout the collagen matrix were successfully generated within 1 h of sequential thermal incubation (20 °C for collagen gelation and subsequently 37 °C for gelatin thermal dissolution), without cytotoxic chemicals. Active particle flow confirmed channel patency and fluidic continuity. Additionally, heparinized rat blood readily perfused through the channels, and scanning electron microscopy revealed open microchannel cross-sections (diameter: approximately 10 μm). This simple, thermally controlled approach resolves the limited temperature compatibility between collagen matrices and sacrificial microfibers, serving as a promising biofabrication foundation for engineering tissue constructs. Full article

Insufficient vascularization remains a major limitation in tissue engineering, restricting the survival and maturation of larger bioengineered constructs. While candidate hydrogels are commonly characterized with regard to physicochemical properties, gelation behavior, mechanical performance, and cytocompatibility, simple functional assays that assess their capacity to support vascular sprouting are less frequently integrated into early-stage biomaterial evaluation. Here, we investigated the established ex vivo aortic ring assay (ARA) as an exploratory functional approach for the initial comparison of selected hydrogel formulations. Murine aortic rings were embedded in collagen I (Col I), alginate (Alg), or gelatin methacryloyl (GelMA) and cultured under control conditions or with vascular endothelial growth factor A (VEGF-A) stimulation. These hydrogels were intentionally selected as a proof-of-concept panel of representative, non-equivalent material classes with distinct expected cell-interactive properties. After five days, Col I supported robust capillary-like outgrowth that was further enhanced by VEGF-A, whereas the tested GelMA formulation supported only limited cellular migration and the tested unmodified Alg formulation showed no detectable sprouting under the conditions examined. Cluster of differentiation 31 (CD31) immunostaining supported the presence of an endothelial component within the Col I-supported sprouting structures. These findings demonstrate that the ARA can detect pronounced formulation-dependent differences among the specific hydrogels tested using straightforward morphological and immunostaining readouts. Within the scope of the formulations tested, these findings support the ARA as a complementary functional readout alongside conventional biomaterial characterization before more complex tissue engineering or biofabrication studies are performed. Full article

Background: Loss of epithelial integrity leaves the wound bed open to opportunistic bacterial colonization, and the risk of secondary infection persists for as long as the defect remains unclosed. Wound dressings must therefore provide an immediate external barrier while accelerating restoration of the skin’s own barrier. This study aims to develop and evaluate a bioactive nanotechnological platform comprising dexpanthenol (Dxp)-engineered extracellular vesicles (EVs) embedded within cross-linked hyaluronic acid hydrogels (HA@Dxp-engineered EVs) for targeted wound treatment and protection against external contaminants. Methods: EVs were engineered via exogenous (extrusion; Exo EV) and endogenous (co-incubation; Endo EV) strategies to encapsulate Dxp. The physicochemical properties of the HA@Dxp-engineered EV systems were characterized, and their therapeutic efficacy was validated through in vitro assays, including fibroblast migration and endothelial tube formation, and in vivo using a full-thickness excisional wound model in mice. Results: Both engineering strategies successfully encapsulated Dxp while preserving the structural integrity of the EVs. The HA hydrogel enabled sustained EV release and provided a physical barrier. In vitro, HA@Endo EVs significantly promoted fibroblast proliferation, migration, and the formation of mature capillary-like networks in HUVECs compared to controls. In vivo, the HA@Endo EV group demonstrated accelerated wound closure, achieving 99.88% healing by day 10, and promoted tissue remodeling with upregulated expression of COL1A1, VEGF, and HIF-1α. Conclusions: The HA@Endo EV system provides a dual-action strategy against secondary infection risk. It supplies an immediate physical barrier over the wound bed and simultaneously accelerates re-epithelialization, thereby shortening the interval during which the tissue remains exposed. Full article

Automated and accurate segmentation of retinal vessels in fundus images provides pivotal evidence for ophthalmologists to effectively and non-invasively diagnose prevalent ocular and systemic diseases. However, existing methods often struggle to maintain the topological continuity of fine-diameter capillaries, leading to severe vascular discontinuity and fragmented segmentation results in challenging scenarios such as complex, irregular microvascular branches, pathological lesions, and high-noise conditions. To address these limitations, we developed a novel symmetric dual-branch network with frequency-aware decomposition and prototype refinement (FDPR-DBNet). Specifically, the network initially utilizes the discrete wavelet transform (DWT) to decompose input retinal images into high-frequency and low-frequency components, which are then processed by a structurally symmetric dual-branch encoder. In the high-frequency branch, the parallel atrous convolution activation (PACA) module is designed to explore fine-grained contour and edge patterns related to vessel terminals and microvessels. Concurrently, within the low-frequency branch, the spatial-frequency characteristic activation (SFCA) unit is constructed by introducing the selective state-space model ($S6$) and Fourier transform to extract salient structural backbones. Moreover, the spatial attention residual fusion (SARF) module and cross-frequency fusion (CFF) block are designed to establish a symmetric guidance mechanism, effectively reinforcing bidirectional feature interaction and alignment across different frequency spectra to eliminate vascular fragmentation. Furthermore, by embedding global and local window self-attention into the Transformer, we formulated the cross-scale enhancement (CSE) module, comprising global semantic enhancement (GSE) and local detail enhancement (LDE), to model multi-scale contextual semantic correlations and enhance the adaptive recognition of vessel structures. Ultimately, we embedded the multi-wise prototype characteristic refinement (MPCR) component into the decoder to correct cross-scale semantic features through a dynamic calibration mechanism, while introducing a new connectivity loss to strictly enforce topological continuity. Experimental results on four publicly available retinal image datasets (DRIVE, CHASE_DB1, STARE, and IOSTAR) demonstrate that the proposed model achieves competitive performance and effectively preserves vascular integrity even in the presence of fundus lesions and noise. Full article

Microwave (MW) ablation is a minimally invasive technique used to destroy pathological tissues through localized heating generated by a needle applicator. Internally cooled applicators using water circulation have long been the standard for high-power applications; however, water cooling introduces significant mechanical complexity. This work investigates the feasibility of a novel air-cooled coaxial thermal-ablation needle operating at 2.45 GHz up to 70 W. The system uses two concentric metal tubes—an outer 14 G stainless steel shaft (OD 2.1 mm) and an inner copper capillary (OD 1 mm, ID 0.7 mm)—serving simultaneously as the MW transmission line and cooling conduit, with dry air at room temperature (25 °C) flowing at 11 L/min under 5 bar input pressure. Experimental cooling efficiency tests demonstrated 78% efficiency for the shaft section in air and 32% for the section embedded in tissue. Electromagnetic and thermal simulations predicted ablation dimensions in a non-perfused liver of 35 mm short axis with ellipticity of 0.65 for the basic applicator, improving to 0.88 with an advanced PEEK-shaft design featuring a cancelling slot. A prototype was built and tested on exvivo bovine liver, achieving input matching better than −24 dB at 2.44 GHz and ablation dimensions (average of 5 tests) of 31 mm short axis and 45 mm long axis. Results confirm the feasibility of air cooling as a simpler, safer, and lower-cost alternative to water cooling for medium-power MW ablation. Full article

Background/Objectives: An ideal bone scaffold should promote bone cell growth and functional vascularization, hence the importance of imbuing biomaterials with pro-angiogenic cues. In this work, silica-based bioactive glasses, either pristine (SBA3) or doped with copper (SBA3_Cu), were embedded in poly(ε-caprolactone) (PCL), which was also used as a control. Methods: In vitro co-cultures of adipose-derived mesenchymal stem/stromal cells (ASCs) and human microvascular endothelial cells (HMEC-1s) were kept in α-MEM, MCDB131, and EndoGRO media to test the biomaterials. The co-cultures were visualized by immunofluorescence and SEM, while flow cytometry was performed to characterize cellular immunophenotype. The angiogenic potential was evaluated using conditioned media of co-cultures to perform a tubulogenesis assay and VEGF-A quantification. Results: Immunophenotypic analysis showed a significant decrease in the endothelial CD31+ cellular subset, whereas the OB-like cellular subset expressing CD105, CD73, CD90, and ALP increased in all culture media over time. In α-MEM, HMEC-1s were unable to form a capillary network independent of the substrates. A more organized network was visible when co-cultures were plated on PCL, in MCDB131 and EndoGRO, or if they were kept in EndoGRO on PCL/SBA3_Cu. The VEGF-A concentrations were similar in the conditioned media from co-cultures grown on PCL/SBA_Cu, in EndoGRO, and on PCL and PCL/SBA3, in MCDB131. Conclusions: The presence of copper did not promote the angiogenic potential of HMEC-1, likely due to the low concentration of released copper ions and the predominant osteoinductive effect of the other ions released by the bioglass. A re-evaluation of formulation and structure of bioglass scaffold could enhance the angiogenic potential. Full article

The present study evaluates the electrochemical behaviour of reinforcing steel embedded in an alkali-activated eco-cellular geopolymer concrete designed for applications in environments with high chloride exposure. The material was formulated using a ternary precursor composed of fluid catalytic cracking residue (FCC), Class F fly ash, and ground granulated blast furnace slag (BFS), activated with an alkaline solution and combined with preformed foam to generate a microstructure characterised by predominantly closed porosity and low capillary connectivity. The electrochemical response of the system was assessed through open circuit potential (OCP) measurements, Tafel polarisation curves, electrochemical impedance spectroscopy (EIS), and potentiodynamic tests under accelerated exposure to NaCl solutions. The results demonstrate a markedly improved electrochemical performance, evidenced by shifts in OCP towards more noble values, reductions of 45–65% in corrosion current density (Icorr), and increases of up to fourfold in charge transfer resistance (Rct), together with the development of broader and more stable passive regions. This behaviour is attributed to the synergistic interaction between the formation of dense N-(C)-A-S-H (sodium/calcium–aluminosilicate hydrate) and C-(A)-S-H (calcium–aluminosilicate hydrate) gels, the eco-cellular architecture with low capillary connectivity, and the stable high alkalinity of the activated matrix, which collectively restrict ionic transport and promote the passive stability of the reinforcing steel—defined here by noble OCP values, low Icorr, high Rct, and sustained passive domains in polarisation curves. Overall, the findings position the developed eco-cellular geopolymer concrete as a sustainable, high-performance alternative for infrastructure exposed to chloride-rich environments. Full article

Microfluidic paper-based analytical devices (µPADs) convert ordinary cellulose into an active analytical platform where capillary gradients shape transport, surface chemistry guides recognition, and embedded electrodes or optical probes translate biochemical events into readable signals. Progress in fabrication—from wax and stencil barriers to laser-defined grooves, inkjet-printed conductive lattices, and 3D-structured multilayers—has expanded reaction capacity while preserving portability. Detection strategies span colorimetric fields that respond within porous fibers, fluorescence and ratiometric architectures tuned for low abundance biomarkers, and electrochemical interfaces resilient to turbidity, salinity, and biological noise. Applications now include diagnosing human body fluids, checking food safety, monitoring the environment, and testing for pesticides and illegal drugs, often in places with limited resources. Researchers are now using learning algorithms to read minute gradients or currents imperceptible to the human eye, effectively enhancing and assisting the measurement process. This perspective article focuses on the newest advancements in the design, fabrication, material selection, testing methods, and applications of µPADs, and it explains how they work, where they can be used, and what their future might hold. Full article

The hydraulic performance of woven geotextiles is frequently overlooked in roadway design, despite their extensive use for reinforcement applications. Woven geotextiles are typically manufactured from hydrophobic polymers such as polypropylene or polyester and can act as capillary barriers under unsaturated conditions. This results in moisture accumulation at the soil–geotextile interface, adversely impacting long-term pavement performance. Such problems can be effectively mitigated using geotextiles with enhanced lateral drainage (ELD) capabilities, which are engineered with hydrophilic fibers to facilitate capillary-driven lateral water movement under unsaturated conditions. This functionality facilitates the redistribution of moisture away from the interface, mitigating moisture retention and enhancing drainage performance. The hydraulic performance of geotextiles with enhanced lateral drainage capabilities under unsaturated conditions remains insufficiently understood, particularly in terms of their influence zone and drainage efficiency. For this reason, the present study evaluates the lateral drainage behavior of an ELD geotextile using a soil column test, compared against a control setup without a geotextile and with a non-woven geotextile. Two moisture migration scenarios, namely capillary rise and vertical infiltration, were simulated, with the water table varied at multiple depths. Moisture sensors were embedded along the column depth to monitor real-time water content variations. Results show that the ELD geotextile facilitated efficient lateral drainage, with a consistent influence zone extending up to 2 inches below the fabric. Under infiltration, the ELD geotextile reduced moisture accumulation by 30% around the geotextile, highlighting its superior drainage behavior. These findings encourage practicing engineers to adopt rational, performance-based designs that leverage ELD geotextiles to enhance subgrade drainage and moisture control in pavement and geotechnical applications. Full article

Calcium is a key macroelement involved in a range of physiological processes in the body, and its concentration in blood is an important diagnostic indicator in various diseases. This work presents a novel rapid method for the point-of-care determination of total calcium content in patient blood, by applying a drop of capillary blood from a finger onto a hydrogel. Gelatin hydrogel, modified with an optical sensor for calcium, Arsenazo III, was used as a platform for the separation of blood into plasma and erythrocytes. A comparative analysis of various types of hydrogel materials (polyacrylamide, PVA, Fmoc-FF, carbomer, carbopol, gelatin) was performed, demonstrating that among the studied systems, only gelatin hydrogel is suitable as a platform for the determination of calcium in blood plasma. The binding of calcium ions from blood plasma with the calcium sensor embedded in the hydrogel leads to a change in the absorption spectrum of the system, enabling photometric determination of calcium concentrations below and above the normal range in blood plasma. Therefore, this rapid assay allows monitoring of calcium metabolism disorders in the human organism. The method is characterized by its speed, simplicity of sample preparation, and potential for integration into clinical practice. Full article

Thermally activated building systems (TABS) rely on high thermal mass materials, such as concrete, which perform well thermally but have a high carbon footprint. This study systematically investigates the thermal behavior of bio-based materials—spruce, pine, beech, and oak—in TABS using numerical simulations, comparing them with conventional and hybrid materials like concrete and clay. A total of 120 variants were simulated with different pipe diameters, spacing, embedment depths, and inlet temperatures. Thermal properties, particularly thermal conductivity and specific heat capacity, significantly influenced component activation efficiency. Concrete exhibited a characteristic cooling time of 71 h at an inlet temperature of 26 °C (pipe diameter 16 mm), while pine reached 80 h under the same conditions. The use of capillary tube mats extended the cooling times to 75 h for concrete and 92 h for pine. Although concrete provides the best thermal performance, certain bio-based materials achieve comparable results under optimized conditions. Hybrid systems with mineral components offer additional potential for improvement. These findings demonstrate that ecologically sustainable component activation using bio-based materials is feasible with only moderate efficiency losses compared to mineral-based systems, provided system parameters are appropriately adapted. Full article

The funerary cenotaph dedicated to Antonio Canova in the Frari basilica was erected in 1827. Since the beginning, some alteration features were recorded. In the last decades, some areas showed a sharp increase in deterioration processes due to large pieces of marble details missing from the statue surfaces. Macroscopic observation of the marble surface showed different forms of alteration as well as the massive presence of salt efflorescence. The main aim of this paper is to assess if there is a relationship between the decay observed and the presence of salt efflorescence, to subsequently ascertain the source of salts, and consequently to propose how to intervene to stop any further cause of alteration. In order to assess the relationship between the different types of alteration macroscopically observed, some samples were taken from the specific areas showing significant alteration features. Optical (OM) and scanning electron microscopic (SEM) observations associated with energy dispersive analysis (EDS) allowed us to explain the stages, each one corresponding to different features, through which the exfoliation and lamination of surface scales have been taking place. Moisture content in the brick structure was in the range of 17–26% until 140 cm of height. Above this height, moisture content is decreasing, and the maximum height of the capillary rise front is between 200 and 250 cm. In these areas, ions coming from the foundations of the monument deposit salt crystals within marble at a sub-surface level, causing the detachment of marble surface layers. In order to stop the rapidly increasing rate of decay observed over the last decades, it has been recommended to remove the statues from the basement and to insert a damp-proof course to prevent any further capillary rising damp. For the removal of embedded salts in the statues, the immersion of the removed statues inside deionized water baths has been recommended. Full article

Exploring innovative approaches to enhance the performance of photonic lanterns is greatly valuable. In this paper, we first propose an air-hole-assisted pure silica-based capillary (AHC), featuring a single ring of embedded air holes. As a result, the PL based on the AHC exhibits good performance, successfully exciting LP₀₁, LP_11a & LP_11b, LP_21a & LP_21b, LP₀₂, and LP_31a & LP_21b modes. The average mode loss, mode-dependent loss, and maximum crosstalk are 0.08 dB, 0.04 dB, and −27.2 dB, respectively. In fact, the overall performance of the proposed AHC-based PL is on par with that of the traditional PL. Furthermore, an error analysis is provided to confirm the feasibility of our approach. The AHC-based PLs possess high numerical apertures and are expected to enable high spatial resolution imaging in optical imaging. Full article

Spontaneous counter-current imbibition is a crucial recovery mechanism in water-wet fractured reservoirs, especially in unconventional formations like tight and shale reservoirs. The geometric characteristics of microscale fractures require further clarification regarding their impact on imbibition. In this paper, the numerical simulation method is used to study the influence of fracture aperture, length, density, and relative position between fracture and imbibition open face on the counter-current imbibition process of a matrix block. For fractures perpendicular to the imbibition surface and in contact with water, the embedded discrete fracture model is utilized to simulate the impact of varying fracture apertures on counter-current imbibition. For fractures parallel to the imbibition surface, considering the impact of fracture on the capillary discontinuity of the matrix, the effects of varying fracture lengths and densities on counter-current imbibition are simulated. The results show that when fractures are perpendicular to the imbibition surface and in contact with water, the imbibition rate can be increased, and as the fracture aperture decreases, the imbibition rate first increases and then decreases. On the other hand, fractures parallel to the imbibition surface inhibit the imbibition process, with the imbibition rate decreasing as fracture length or density increases. This paper proposes an empirical shape factor considering the geometric characteristics of fractures, which can effectively characterize the influence of microfractures on matrix block imbibition, thus improving the dual-medium numerical simulation model. Full article

Non-invasive blood analysis has the power to completely change how doctors identify and track illnesses. This study presents a novel approach for the non-invasive monitoring of red blood cell (RBC) mobility and concentration within capillaries, using photon absorption as a key diagnostic tool. The research combines optical modeling with the diffusion equation for light propagation, leveraging COMSOL simulations to create a comprehensive framework for understanding RBC dynamics. A two-dimensional geometric model of capillaries with RBCs is developed, where blood flow is modeled as a laminar, incompressible fluid. The Arbitrary Lagrangian–Eulerian (ALE) formulation is employed to account for the fluid–structure interactions, while photon attenuation by the RBCs is analyzed to investigate wavelength-dependent absorption characteristics. The methodology is implemented through a workflow developed with MATLAB’s S-Function builder, consisting of three main components: mesh generation, fluence computing, and Software-in-the-Loop (SIL) verification. The mesh generation process adapts to the target architecture using COMSOL Multiphysics for fluid–structure interaction (FSI) modeling. The fluence computing function solves the diffusion equation to model light intensity attenuation due to RBCs, and the SIL function compares computed results with real-time measurements, ensuring accuracy for potential real-time embedded system applications. The results demonstrate significant wavelength-dependent variations in photon absorption by RBCs, providing insights into the optical behavior of blood in microvascular structures. The findings have important implications for medical imaging, photodynamic therapy, and diagnostic tools, emphasizing the potential of integrating computational models with real-time systems for enhanced performance in biomedical applications. Full article