Search Results (647)

This comprehensive review aims to cover the surface tribology and triboelectric properties of additively manufactured (AM) natural biopolymers, including cellulose, chitosan (CS) and silk fibroin (SF), in biomedical interface engineering. While these sustainable materials exhibit innate biocompatibility and tribopositivity, their baseline triboelectric performance demands targeted surface engineering. We synthesize key physical mechanisms governing charge generation, emphasizing how controlled surface roughness, hierarchical porosity and nanoscale architectures maximize contact electrification. Furthermore, distinct dielectric and polarity modulation strategies are evaluated across the biopolymer families: cellulose relies heavily on chemical functionalization to overcome weak native polarity; chitosan utilizes ionic coordination and fillers to elevate its relatively low charge density; and silk fibroin achieves exceptional power outputs via highly porous three-dimensional nanocomposite aerogels. AM technologies afford unprecedented spatial control over these biointerfaces but introduce severe processing constraints. Techniques such as those based on extrusion impose strict shear-thinning rheology and rapid crosslinking for cellulose and chitosan, while SF frequently suffers from crystallization-induced nozzle clogging, necessitating photocurable derivatives. Full article

Alginate hydrogels offer mild ionic gelation and tunable porosity for drug delivery, yet their hydrophilic, macroporous networks suffer from rapid initial burst release of water-soluble payloads. Here we introduce a hierarchical barrier-engineering strategy in which poly(D,L-lactide-co-glycolide)/poly(ethylene glycol) (PLGA/PEG) blend coatings are applied via dip-coating to Ca²⁺-cross-linked alginate beads (~1 mm) and microgels (~100 µm). For beads, three-cycle PLGA/PEG multilayer coating suppressed the initial swelling rate (dQ/dt) by ~50% and reduced 1 h burst release from >85% to ~60%, functioning as an “early-burst buffer” rather than a long-term depot. For microgels, a single PLGA/PEG layer partially attenuated burst release; however, an additional PLGA outer shell (double-barrier architecture) shifted the release-governing mechanism from swelling-dominated to diffusion-barrier-dominated control, limiting 10 min release to <10%. Core–shell formation was verified by confocal laser scanning microscopy (CLSM), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS); thermogravimetric analysis (TGA) showed ~73–79% coating retention after 9 days in phosphate-buffered saline (PBS, 37 °C). A vacuum re-loading process further improved encapsulation efficiency (>50% for beads, >20% for microgels) without compromising gel integrity. In beads, burst control was governed by swelling suppression; in microgels, the additional PLGA shell shifted control to diffusion-barrier-dominated release, demonstrating that barrier architecture must be adapted to particle scale. Full article

In sensing technologies, a hydrogel sensor with a specific response to stimuli allows for real-time monitoring of mechanical, thermal, and biochemical signals in wearable and implantable devices. This review discusses the latest advances in hydrogel-based sensors published between 2023 and spring 2026 and the design strategies prevalent in these articles, including the use of polymers, nanomaterial reinforcement, incorporation of ionic solvents, and physical or chemical crosslinking. The influence of supramolecular hydrogels on the quality of sensor parameters, including the impact on mechanical resistance, ionic conductivity, adaptation, and self-healing, is examined. In biomedical engineering, hydrogels, thanks to their biomimetic and programmable properties, enable control of wound repair and soft tissue interfaces. The review concludes by outlining the challenges, opportunities, and advances in the chemistry and mechanics of hydrogels, which may ultimately facilitate the development of multifunctional monitoring systems in healthcare. The abundance of information requires systematic, frequent reviews to accelerate the application of innovative solutions in practice. Carbon nanostructures are a key component that ensures the sensor’s electrical conductivity. 3D printing technology has enabled the creation of individually customizable health monitoring devices. The work also highlights the use of nanodots in sensor production. Full article

Solid-state sodium batteries based on polymer electrolytes offer a sustainable solution to overcome current and near-future needs regarding the growing energy and transport electrification issues. In this work, we propose the development of solvent-free polymer electrolytes based on an unsaturated polyether, which, once cross-linked, leads to an amorphous structure at room temperature that favors ionic transport towards reliable and robust solid-state sodium batteries operative at moderate temperatures. Using NaClO₄ and NaPF₆ as sodium salts, the best polymer electrolyte reaches an ionic conductivity in the range of 0.02 mS·cm⁻¹ (30 °C)–0.90 mS·cm⁻¹ (100 °C) with a lifetime superior to 2000 h after plating and stripping. Regarding electrochemical performance, a maximum specific capacity of 110.2 mAh·g⁻¹ (C/20) is obtained for the polymer electrolyte including NaClO₄, using Na and C/FePO₄ as anode and cathode, respectively, which represents about 65% of the theoretical value expected for FePO₄. In view of more sustainable energy storage devices, a life cycle assessment is also applied. While the polymer matrix is identified as the main environmental hotspot, the choice of Na salt significantly affects the overall impact, with NaClO₄ exhibiting lower climate change and particulate matter impacts than NaPF₆. Full article

High-performance flexible electronics require soft materials that combine mechanical robustness with efficient ionic conduction. In conventional ionogels, however, these requirements often conflict: dense networks improve strength but reduce the free volume and mobility needed for ion transport. This review provides a critical overview of recent progress in cellulose-based ionogels, with emphasis on design principles for decoupling mechanical and conductive properties. We discuss how cellulose precursors, crosslinking architectures (hydrogen bonding, covalent networks, and metal-ion coordination), and processing histories determine gel structure and mechanical integrity. We then highlight strategies that mitigate the trade-off, including precursor engineering, phase-separated networks, double-network architectures, crystallization-induced reorganization, and anisotropic assembly. Representative applications in flexible sensors, flexible energy-storage devices, and soft actuators are also summarized. This review offers a practical framework for designing cellulose-based soft functional materials with robust mechanics and sustained ionic conductivity. Full article

Hydrogel scaffolds have emerged as a central platform in tissue engineering due to their ability to mimic the extracellular matrix and support cellular functions. Among natural polymers, chitin and its derivative chitosan have emerged as valuable candidates for hydrogel scaffold development because of their biodegradability, compatibility with living tissues, and inherent biological functionality; however, their distinct and complementary roles in hydrogel scaffold design are often insufficiently differentiated in the literature. This review provides a comprehensive and mechanism-driven analysis of chitin- and chitosan-based hydrogel scaffolds, emphasising how their molecular structure governs network formation, mechanical performance, and biological functionality. Chitin is highlighted primarily as a structurally robust and crystalline component suitable for reinforcement. In contrast, chitosan serves as a versatile, soluble, and chemically reactive matrix enabling various crosslinking and functionalization strategies. Recent advances in physical, ionic, and covalent crosslinking as well as composite scaffold engineering, biofunctionalization, and emerging fabrication approaches such as injectable systems and three-dimensional bioprinting are systematically examined. The relationships between scaffold architecture, degradation behaviour, and cellular responses are discussed in key tissue engineering applications, including bone, cartilage, skin, and nerve regeneration. Importantly, this review introduces a unified structure–property–function framework that distinguishes the roles of chitin and chitosan within hydrogel systems and links crosslinking mechanisms to application-specific performance requirements, an aspect not comprehensively addressed in previous studies. Current challenges related to mechanical limitations, material variability, and clinical translation are critically evaluated, and future perspectives for the rational design of next-generation biomimetic hydrogel scaffolds are proposed. Full article

Objective: Developing foundational biomaterial platforms for cultured meat research requires 3D co-culture systems capable of supporting multiple relevant cell types in a spatially organized manner. This study aimed to establish a compartmentalized tri-culture hydrogel disc incorporating a lipid-containing barrier phase as a proof-of-concept in vitro model. Methods: Beeswax/alginate (Bw/Algi) hydrogels were fabricated and evaluated for morphology and cytocompatibility as a lipid-containing scaffold component. Fucoidan/alginate (Fu/Algi) hydrogels were prepared at varying fucoidan concentrations and screened to identify conditions compatible with C2C12 viability and early-stage differentiation. A composite beeswax/fucoidan/alginate disc (Bw/Fu/Algi) was then assembled by casting cell-laden Fu/Algi regions (myoblasts, fibroblasts, and endothelial cells), separated by Bw/Algi barrier layers and ionically crosslinked with CaCl₂. Scaffold performance was assessed using standard assays for morphology, cytocompatibility, myogenic marker expression, protein production, and thermal stability. Results: Bw/Algi supported cytocompatible C2C12 attachment and growth, while Fu/Algi exhibited concentration-dependent effects on myogenic marker expression, enabling selection of an optimized fucoidan concentration for 3D assembly. The final Bw/Fu/Algi disc maintained viable compartmentalized tri-culture and supported indirect co-culture through spatial separation by the Bw barrier. Myogenic regions exhibited myogenic marker expression with measurable protein production, and differential scanning calorimetry confirmed structural stability under heating. Conclusion: This work establishes a Bw/Fu/Algi tri-culture disc integrating a lipid-containing barrier component with hydrogel-based myogenic compartments, providing a preliminary platform for multicellular in vitro modeling and scaffold design relevant to cultured meat research. Full article

The world’s current technical developments are mostly dependent on semiconductors. Even though traditional semiconductor materials are important, they have various disadvantages, especially when evaluated against polymer-based alternatives. Hydrogel-based semiconductors provide soft, ionically linked electronic interfaces by combining hydrated, mechanically compliant matrices with electrically active conjugated polymers and composites which can be applied in bioelectronic and thermoelectric generator/cells. Volumetric capacitances are normally in the range of 1–485 F·cm⁻³, demonstrating excellent ion storage, transport capabilities, and electron mobilities for hydrogel semiconductors spanning roughly 0.25 cm²/V·s (measured for n-type P(PyV)-H hydrogel). The fabrication techniques include additive free casting and room-temperature crosslinking, which lower energy input while maintaining electronic performance; typical systems maintain >80% of their conductivity after ${10}^3$–${10}^4$ mechanical cycles. This review study mainly focuses on the design, preparation, application, and prospects of gel/hydrogel-based semiconductors. It gives readers a thorough understanding of the basic ideas that underline their structure and operation. All things considered, this work is a useful tool for engineers and researchers looking to maximize the potential of gel-based semiconductors in next-generation electrical systems. Full article

Protein recognition underpins advances in drug discovery, immunoassays, clinical diagnostics and biosensing. As a biomimetic alternative to natural receptors, molecularly imprinted polymers (MIPs) have been developed to emulate antibody–antigen complementarity by generating binding cavities that mirror the size, shape and functionality of target macromolecules through template-directed polymerization and subsequent template removal. However, protein imprinting has historically been hampered by low imprinting efficiency and limited selectivity, rendering conventional protein-imprinted polymers (PIPs) inadequate for many contemporary biomedical applications. Functional ionic liquids (ILs)—a class of designer solvents and materials distinguished by tunable structures, exceptional physicochemical properties and favorable biocompatibility—have emerged as versatile additives to address the principal limitations of traditional PIPs, including poor selectivity, sluggish mass transfer and destabilization of protein conformation. Here, we provide a systematic review of the multifaceted roles that ILs play within protein-imprinting systems, delineating their employment as template-anchoring motifs, functional monomers, cross-linkers, porogens and structural stabilizers, and evaluating the consequent effects on polymer architecture and recognition performance. We further probe the multiplicity of non-covalent interactions between ILs and template proteins—highlighting the synergistic modulation afforded by electrostatic forces, hydrogen bonding, hydrophobic interactions and π-π stacking—and consider how such interplay can be harnessed to fine-tune binding-site fidelity. Consolidating recent progress, we summarize IL-enabled PIP applications in protein-specific recognition, biosensor development and analysis of complex real-world samples, and we critically examine the prevailing technical challenges and prospects for translation. The evidence indicates that ILs, by furnishing abundant interaction sites, accelerating mass transport and stabilizing native protein conformations, can markedly enhance PIP adsorption capacity, target specificity and recyclability, positioning them as a cornerstone for next-generation protein separation and enrichment materials and paving the way toward industrial deployment of protein-imprinting technologies. Full article

Electrical monitoring of brain activity can be performed discreetly and continuously over long periods of time using intra-auricular electroencephalography (intra-auricular EEG), a promising technique suitable for subjects who are difficult to monitor, such as newborns or patients with neurological conditions requiring discreet but long-term neurophysiological assessment. The concept of intra-aural EEG can be realized through the development of systems that include wearable sensors, whose performance critically depends on the development of biocompatible electrode materials that exhibit low impedance and can maintain and provide stable contact between the electrode and the epithelial tissue. Based on our previous work on carbon nanotube (CNT)-based hydrogel composites for intra-aural EEG electrodes, this study focuses on the electrochemical characterization of hydrogels initially prepared from gelatin methacrylate (GelMA)/2-hydroxyethyl methacrylate (HEMA) doped with varying concentrations of CNTs (0–3 wt%). In the present study, the materials obtained in the first stage were evaluated using electrochemical impedance spectroscopy (EIS) under both liquid and dry conditions, supplemented by measurements of hydration capacity. The results show that the composite with 3% CNT content exhibits suitable properties, making the material making the 3 wt% CNT formulation a promising platform for the further development of 3D-printable hydrogel electrodes for intra-aural EEG applications. Equivalent circuit modeling reveals improved ionic and electronic conductivity compared to the undoped hydrogel, attributed to better CNT dispersion and polymer crosslinking. This work provides insights into the structure–property relationships of CNT–hydrogel composites and lays the foundation for the further development of a 3D-printed and in vitro/in vivo validated prototype of intra-aural EEG sensors. Full article

Electrostatic protein–polysaccharide hydrogels are attractive materials formed without thermal denaturation or chemical crosslinkers and at low biopolymer contents. Their broader application in foods, however, has been limited by slow gelation, with network development often requiring many hours (~18 h). In this study, millimeter-scale hydrogel beads were fabricated from amaranth proteins and xanthan gum by extrusion into glucono-δ-lactone (GDL) solutions (1–5 mg/mL) using hardening times of 10 or 30 min. Beads were successfully formed under all conditions (3.07–3.95 mm diameter), and their physicochemical properties, intermolecular interactions, microstructure, and gel strength were evaluated. Electrostatic attraction remained the dominant force driving gelation. Furthermore, 10 min hardening favored interpolymeric electrostatic interactions, whereas longer exposure reduced them and promoted hydrogen bonding and hydrophobic interactions. These molecular rearrangements were accompanied by a decreased size, lower water retention capacity (WRC), and higher mechanical strength. The mildest treatment (1 mg/mL GDL, 10 min) was post-loaded with a coffee pulp phenolic extract and showed reduced gel strength and electrostatic interactions, suggesting competition for binding sites within the macromolecular network. The extrusion of amaranth protein–xanthan gum mixtures into a GDL bath markedly shortens electrostatic gelation time, supporting this approach as a potential alternative to ionic gelation for the production of millimeter-scale hydrogel beads for food applications. Full article

This study evaluated the feasibility of developing 3D-printable chontaduro (Bactris gasipaes) gel inks. Freeze-dried chontaduro pulp and encapsulated Lactiplantibacillus plantarum were used. Two formulations were analysed: a control (ChC) and a probiotic ink (ChLp) containing 10% (w/w) microencapsulated cells in a maltodextrin–whey protein carrier. Both were baked at 140 °C under zero humidity and evaluated for water activity, colour, texture, and sensory properties. Rheological analysis showed shear-thinning behaviour for both inks. Notably, ChLp had higher storage (G′) and loss (G″) modulus, which may indicate structural reinforcement by the carrier. Furthermore, FTIR suggested enhanced protein–polysaccharide interactions and ionic cross-linking. Both inks were found to be extrudable; however, ChLp showed a 4.1% reduction in printed height. Baking reduced water activity (aw < 0.88) and caused Maillard browning, which was more pronounced in ChLp. With respect to microbial viability, Ltp. Plantarum viability (~7.1 log CFU/g) was maintained after extrusion but lost after baking. Sensory evaluation indicated formulation-dependent differences in colour (greater yellowness) and texture (reduced adhesiveness, increased hardness) for ChLp. Overall, these findings showed chontaduro gel as a viable matrix for 3D food printing, with the encapsulated carrier altering physicochemical and sensory descriptors. Full article

Conductive hydrogels have emerged as promising candidates for flexible strain sensors owing to their high water content, low elastic modulus, and intrinsic ionic conductivity. However, conventional hydrogel networks often suffer from an inherent trade-off among conductivity, mechanical robustness, and long-term stability, which limits their practical deployment in wearable sensing scenarios. The introduction of metal–ligand coordination bonds into hydrogel networks offers a versatile strategy to address these challenges: dynamic coordination cross-links can dissipate energy under deformation and reform upon unloading, thereby enhancing toughness, enabling self-healing, and contributing to ionic transport. This review focuses on metal-ion-coordinated conductive hydrogels designed for strain-sensing applications. Representative coordination systems based on Fe³⁺, Ca²⁺, Zn²⁺, Al³⁺, Cu²⁺, Ti⁴⁺, and Zr⁴⁺ are surveyed, with emphasis on their characteristic polymer matrices, ligand chemistries, and network-construction strategies. Key sensing-relevant properties—including ionic conductivity, mechanical stretchability, self-healing capability, interfacial adhesion, freezing resistance, and resistance to dehydration—are discussed in relation to coordination network design. Typical application demonstrations in large-deformation motion monitoring and subtle physiological signal detection are reviewed. Unlike existing reviews that survey conductive hydrogels broadly by conductive mechanism or sensor type, this review takes metal-ion coordination as the central organizing principle and systematically traces its influence across the full design chain—from ion–ligand coordination chemistry through network architecture to macroscopic sensing output. By comparatively analyzing seven representative metal-ion systems within a unified framework, this work aims to clarify how the choice of metal ion governs the interplay among conductivity, mechanical robustness, self-healing, and strain sensitivity—a perspective that has not yet been systematically addressed in prior reviews. Finally, current challenges—including the conductivity–mechanics coupling bottleneck, insufficient long-term stability, biosafety concerns for skin-contact deployment, the lack of standardized evaluation protocols, and device-integration barriers—are identified, and future directions for this field are outlined. Full article

Gelatin–alginate composite hydrogels are some of the most prevalent bioinks used for extrusion-based three-dimensional (3D) bioprinting because of their combined bioactivity and ability to ionically crosslink. Ionically crosslinked gelatin–alginate constructs containing human bone marrow–derived mesenchymal stem cells (hBM-MSCs) were characterised over time under standardised in vitro conditions to assess physicochemical properties and resultant cell behaviour. Water uptake and degradation were quantified over time in phosphate-buffered saline (PBS) and collagenase type II media for up to 21 days. Cell viability and metabolic activity were quantified, and osteogenic gene expression (RUNX2, COL1A1, OCN) was assessed. Raman spectroscopy and compressive mechanical characterisation were performed. Collagen and glycosaminoglycan-related peaks were observed from extracellular matrix (ECM)-associated components, with an increased presence of protein-associated signatures later in culture. Hydrogels displayed nonlinear elastic behaviour with increased stress after longer incubation times, suggesting no degradation of mechanical integrity over the duration of the study. Hydrogels experienced rapid hydration followed by decreased swelling over time, with a maximum swelling ratio at 24 h. Degradation rates significantly increased over longer incubation times (p < 0.001) and in collagenase media compared to PBS (p < 0.001). Observed differences were likely due to both ion-exchange-mediated network disassembly and the dissolution of gelatin components. Cell metabolic activity decreased under osteogenic culture conditions, while changes in osteogenic marker expression were sequential, suggesting a transition from proliferation to early osteogenic commitment in this 3D system. This work provides both physicochemical and biological characterisation of a commonly utilised gelatin–alginate bioink system, to provide future optimisations within the field of extrusion-based bone tissue engineering, a reproducible baseline for future optimisation of bioink systems in extrusion-based bone tissue engineering. Full article

Purpose: Natural polysaccharides have shown considerable potential in the management of type 2 diabetes mellitus (T2DM) due to their multi-target metabolic regulatory effects. However, their clinical translation is limited by poor oral stability and low intestinal permeability. Snow lotus polysaccharide (SIP), a representative plant-derived polysaccharide, exhibits promising metabolic benefits but suffers from these delivery barriers. This study aimed to develop an oral nanodelivery system to enhance the gastrointestinal stability and intestinal transport of SIP, thereby improving its in vivo efficacy. Methods: SIP-loaded chitosan–tripolyphosphate nanoparticles (SIP@CS-TPP) were prepared via ionic crosslinking and characterized in terms of particle size, surface charge, morphology, and structural features. In vitro release behavior under simulated gastrointestinal conditions was evaluated. Ex vivo intestinal permeation was assessed using an isolated intestinal sac model. The metabolic regulatory effects were further investigated in a high-fat diet/streptozotocin-induced T2DM rat model. Results: SIP@CS-TPP nanoparticles exhibited a uniform particle size of 188.9 ± 12.8 nm, a surface charge of 28.3 ± 5.1 mV, and good stability after freeze-drying. A pH-responsive and diffusion-controlled release profile was observed. Ex vivo studies demonstrated significantly enhanced intestinal transport, with an approximately 3.7-fold increase in apparent permeability compared with free SIP. In vivo, SIP@CS-TPP improved glycemic control, glucose tolerance, insulin resistance, lipid metabolism, oxidative stress, and inflammatory responses more effectively than free SIP at the same dose. Conclusions: The CS-TPP nanodelivery system effectively enhances the oral delivery and metabolic regulatory effects of SIP. This study highlights the potential of a delivery-oriented strategy to improve the in vivo performance of natural polysaccharides and provides a promising approach for their application in metabolic disease management. Full article