Search Results (136)

In the rapidly evolving field of biomedical engineering, hydrogels have emerged as highly versatile biomaterials that bridge biology and technology through their high water content, exceptional biocompatibility, and tunable mechanical properties. This review provides an integrated overview of both natural and synthetic hydrogels, examining their structural properties, fabrication methods, and broad biomedical applications, including drug delivery systems, tissue engineering, wound healing, and regenerative medicine. Natural hydrogels derived from sources such as alginate, gelatin, and chitosan are highlighted for their biodegradability and biocompatibility, though often limited by poor mechanical strength and batch variability. Conversely, synthetic hydrogels offer precise control over physical and chemical characteristics via advanced polymer chemistry, enabling customization for specific biomedical functions, yet may present challenges related to bioactivity and degradability. The review also explores intelligent hydrogel systems with stimuli-responsive and bioactive functionalities, emphasizing their role in next-generation healthcare solutions. In modern medicine, temperature-, pH-, enzyme-, light-, electric field-, magnetic field-, and glucose-responsive hydrogels are among the most promising “smart materials”. Their ability to respond to biological signals makes them uniquely suited for next-generation therapeutics, from responsive drug systems to adaptive tissue scaffolds. Key challenges such as scalability, clinical translation, and regulatory approval are discussed, underscoring the need for interdisciplinary collaboration and continued innovation. Overall, this review fosters a comprehensive understanding of hydrogel technologies and their transformative potential in enhancing patient care through advanced, adaptable, and responsive biomaterial systems. Full article

The development of alginate/polyacrylamide hydrogels for various biomedical applications has attracted significant interest, particularly due to their potential use in wound healing and tissue engineering. This study explores the fabrication of these hydrogels via 3D bioprinting with ultraviolet light curing, focusing on how the alginate concentration and curing speed impact their mechanical properties. Rheological testing was employed to examine the viscoelastic behavior of alginate/polyacrylamide hydrogels manufactured using a 3D bioprinting technique. The relaxation behavior and dynamic response of these hydrogels were analyzed under torsional stress, with relaxation curves fitted using a two-term Prony series. Fourier Transform Infrared (FTIR) spectroscopy was also employed to assess biocompatibility and the conversion of acrylamide. This study successfully demonstrated the printability of alginate/polyacrylamide hydrogels with varying alginate contents. The rheological results indicated that 3D bioprinted hydrogels exhibited significantly high stiffness, viscoelasticity, and long relaxation times. The curing speed had a minimal impact on these properties. Additionally, the FTIR analysis confirmed the complete conversion of polyacrylamide, ensuring no harmful effects in biological applications. The study concludes that 3D bioprinting significantly enhances the mechanical properties of alginate/polyacrylamide hydrogels, with the alginate concentration playing a key role in the shear modulus. These hydrogels show promising potential for biocompatible applications such as wound healing dressings. Full article

Both biosystems and engineering fields demand advanced friction-reducing and lubricating materials. Due to their hydrophilicity and tissue-mimicking properties, hydrogels are ideal candidates for use as lubricants in water-based environments. They are particularly well-suited for applications involving biocompatibility or interactions with intelligent devices such as soft robots. However, external environments, whether within the human body or in engineering applications, often present a wide range of dynamic conditions, including variations in shear stress, temperature, light, pH, and electric fields. Additionally, hydrogels inherently possess low mechanical strength, and their dimensional stability can be compromised by changes during hydration. This review focuses on recent advancements in using environmentally responsive hydrogels as lubricants. It explores strategies involving physical or structural modifications, as well as the incorporation of smart chemical functional groups into hydrogel polymer chains, which enable diverse responsive mechanisms. Drawing on both the existing literature and our own research, we also examine how composite friction materials where hydrogels serve as water-based lubricants offer promising solutions for demanding engineering environments, such as bearing systems in marine vessels. Full article

Cellulose nanocrystals (CNCs), derived from renewable biomass, have emerged as a pivotal component in the design of biomimetic composite hydrogels due to their exceptional mechanical strength, biocompatibility, and tunable surface chemistry. This review comprehensively explores recent advancements in surface modification strategies for CNCs (physical adsorption, chemical grafting, and bio-functionalization) and their impacts on the structure and properties of hydrogel networks, with particular emphasis on mechanical properties. Future applications in light/thermal/electrical-responsive soft actuators are critically analyzed. Guided by biomimetic design principles, the anisotropic mechanical responses induced by CNC-oriented alignment are explored, along with their cutting-edge advancements in soft robotics, wearable sensing, and biomedical devices. Perspectives are provided on future directions, including multi-stimuli synergistic actuation systems and sensing-actuation integration architectures. This work establishes a fundamental framework for designing CNC-enhanced smart hydrogels with tailored functionalities and hierarchical structures. Full article

In this study, we present bi-layered hydrogel systems that incorporate different sizes and shapes of gold nanoparticles (nanospheres and nanorods) for potential use in areas such as photoactuators, soft robotics, artificial muscles, drug delivery and tissue engineering. The synthesized nano Au-PNiPAAm/PVA bi-layered hydrogel nanocomposites provide the unique ability to exhibit controlled motion upon light exposure, indicating that the above systems possess the capability of photo–thermal energy conversion. The chosen synthesis approach is a combination of chemical production of gold nanoparticles (AuNPs) followed by gamma radiation formation of crosslinked polymer networks around them, as the final step, which also allows for sterilization in a single technological step. According to the TEM analysis, the gold nanospheres (AuNSs) with mean diameters of around 17 and 30 nm, as well as nanorods (AuNRs) with an aspect ratio of around 4.5, were synthesized and used as nanofillers in the formation of nanocomposites. Their stability within the polymer matrix was confirmed by UV–Vis spectral studies, by the presence of local surface plasmon resonance (LSPR) bands, typical for nanoparticles of various shapes and sizes. Morphological studies (FE-SEM) of hydrogels revealed the formation of a porous structure with PNiPAAm hydrogel as an active layer and PVA hydrogel as a passive layer, as well as a stable interfacial layer with a thickness of around 80 μm. The synthesized bi-layered photoactuators showed a photo–thermal response upon exposure to irradiation of green lasers and lamps that simulate sunlight, resulting in bending motion. This bending response reveals the huge potential of the obtained materials as soft actuators, which are more flexible than rigid systems, making them effective for specific applications where controlled movement and flexibility are essential. Full article

The integration of chirality into nanomaterials holds significant potential for improving molecular recognition and biomedical technologies. In this work, we fabricated novel chiral horned gold nanostructures (HNS) by controlling the concentration of chiral ligands L-/D-cysteine (Cys). The unique three-dimensional morphology with horns-rotational arrangement enables synergistic optimization of chiral optical responses and surface-enhanced Raman scattering (SERS) performance. The proposed chiral HNSs can be used to recognize amino acid enantiomers, in which homochiral amino acid has distinct affinities to the chiral HNSs of homogeneous handedness. The 4-mercaptobenzoic acid (4-MPBA)-modified D-HNS demonstrates significantly enhanced targeting affinity for D-amino acids in the Escherichia coli (E. coli) cell wall, enabling successful amplification of SERS signals and advancing bacterial detection methodologies. By demonstrating the rotation-selective interaction between chiral HNSs and circularly polarized light (CPL), D-HNS exhibits excellent photothermal conversion efficiency under right-handed circularly polarized light (RCP) irradiation. This enables the synergistic combination of targeted physical disruption and photothermal sterilization, which leads to efficient eradication of E. coli. The D-HNS hydrogel composite system further expands the practical application of photothermal sterilization. Altogether, chiral HNSs have achieved SERS detection of bacteria and efficient polarization photothermal sterilization, which helps further develop applications based on chiral nanomaterials. Full article

Stimuli-responsive hydrogels have emerged as a promising class of biomaterials for advanced wound healing applications, offering dynamic and controllable responses to the wound microenvironment. These hydrogels are designed to respond to specific stimuli, such as pH, temperature, light, and enzyme activity, enabling precise regulation of drug release, antimicrobial activity, and tissue regeneration. Composite stimuli-responsive hydrogels, by integrating multiple response mechanisms and functions, show potential for addressing the diverse needs of wound healing. This review explores the biological mechanisms of wound healing, the design and classification of composite stimuli-responsive hydrogels, and the key fabrication strategies employed to optimise their properties. Despite their immense potential, unresolved challenges such as biocompatibility, long-term stability, and scalability continue to limit their translation into clinical practice. Future research will focus on integrating hydrogels with smart wearable devices, AI-driven personalised medicine, and 3D bioprinting technologies to develop next-generation wound care solutions. With continuous advancements in biomaterials science and bioengineering, stimuli-responsive hydrogels hold great promise for revolutionising wound management. Full article

The low fluorescence quantum efficiency of hydrophilic modified spiropyran in hydrogel matrices cannot be naturally improved during photoresponsive operation, which significantly limits their practical applications.In this study, a hybrid hydrogel system integrating metal plasmon resonance-enhanced fluorescence effects is designed through copolymerization of N,N′-bis(acryloyl)cystamine-modified Au nanoparticles (Au NPs), hydrophilic graft-modified spiropyran molecules, and N-isopropylacrylamide. This approach successfully achieves a spiropyran-based fluorescent hydrogel sensor with enhanced fluorescence intensity. Furthermore, an inverted pyramid-structured surface is engineered on the hydrogel using a template-assisted strategy, combining anti-reflection optical effects with plasmonic enhancement mechanisms. Molecular modification facilitated the integration of spiropyran and Au NPs into the hydrogel molecular chains, enhancing the dispersion of Au NPs within the hydrogel matrix and preventing fluorescence quenching from direct contact between Au NPs and spiropyran. Additionally, the anti-reflection effect of the hydrogel surface microstructure and the plasmon resonance effect of Au NPs were crucial in boosting the sensor’s fluorescence. Finally, the fluorescence intensity of the hydrogel increased by 10.2 times. In addition, under the action of excitation light, this sensor exhibited dual responsiveness of colorimetry and fluorescence, allowing for the sensing of heavy metal ions. The limit of detection for Zn²⁺ is as low as 0.803 μM, and the hydrogel exhibited more than 10 cycles of photo-isomerization and ion responsiveness. Full article

In the context of the information age, the need for data security and confidentiality is becoming increasingly urgent. In this study, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were used as the matrix, and a PVA/PEG/rare earth composite hydrogel material with controllable photoluminescence color was successfully developed by incorporating rare earth ion doping. Through scanning electron microscopy (SEM), X-ray photoelectronic spectroscopy (XPS), X-ray diffraction (XRD), and fluorescence spectroscopy, it was confirmed that the introduction of lanthanide metal light-emitting units makes the material’s photoluminescence color adjustable from red to green, significantly improves the mechanical properties, and the compressive strength is increased from 17.6 MPa to 23 MPa, representing a 30.7% improvement. In addition, the material exhibits excellent alkaline pH response characteristics; as the concentration of NaOH solution increases, the luminous intensity gradually decays to complete quenching. Based on the adjustable light color and dynamic response characteristics, the material can realize information concealment and encryption through programmable light color changes, providing a new functional material solution for intelligent anti-counterfeiting and optical encryption. Full article

Organophosphorus pesticides (OPs), while pivotal for agricultural productivity, pose severe environmental and health risks due to their persistence and bioaccumulation. Existing detection methods, such as chromatography and spectroscopy, face limitations in field adaptability, cost, and operational complexity. To address these challenges, this study introduces a novel dual-mode photoelectrochemical–electrochemical (PEC-EC) sensor based on a Co,N-TiO₂@ZrO₂/3DGH nanocomposite. The sensor synergistically integrates zirconium oxide (ZrO₂) for selective OP capture via phosphate-Zr coordination, cobalt-nitrogen co-doped titanium dioxide (Co,N-TiO₂) for visible-light responsiveness, and a three-dimensional graphene hydrogel (3DGH) for enhanced conductivity. In the PEC mode under light irradiation, OP adsorption induces charge recombination, yielding a logarithmic photocurrent attenuation with a detection limit of 0.058 ng mL⁻¹. Subsequently, the EC mode via square wave voltammetry (SWV) self-validates the results, achieving a detection limit of 0.716 ng mL⁻¹. The dual-mode system demonstrates exceptional reproducibility, long-term stability, and selectivity against common interferents. Parallel measurements revealed <5% inter-mode discrepancy, validating the intrinsic self-checking capability. This portable platform bridges the gap between laboratory-grade accuracy and field-deployable simplicity, offering transformative potential for environmental monitoring and food safety management. Full article

Conductive hydrogels, particularly those incorporating poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), have revolutionized wearable health monitoring by merging tissue-like softness with robust electronic functionality. This review systematically explores design strategies for PEDOT:PSS-based hydrogels, focusing on advanced gelation methods, including polymer crosslinking, ionic interactions, and light-induced polymerization, to engineer hierarchical networks that balance conductivity and mechanical adaptability. Cutting-edge fabrication techniques such as electrochemical patterning, additive manufacturing, and laser-assisted processing further enable precise microstructural control, enhancing interfacial compatibility with biological systems. The applications of these hydrogels in wearable sensors are highlighted through their capabilities in real-time mechanical deformation tracking, dynamic tissue microenvironment analysis, and high-resolution electrophysiological signal acquisition. Environmental stability and long-term durability are critical for ensuring reliable operation under physiological conditions and mitigating performance degradation caused by fatigue, oxidation, or biofouling. By addressing critical challenges in environmental stability and long-term durability, PEDOT:PSS hydrogels demonstrate transformative potential for personalized healthcare, where their unique combination of softness, biocompatibility, and tunable electro-mechanical properties enables seamless integration with human tissues for continuous, patient-specific physiological monitoring. These systems offer scalable solutions for multi-modal diagnostics, empowering tailored therapeutic interventions and chronic disease management. The review concludes with insights into future directions, emphasizing the integration of intelligent responsiveness and energy autonomy to advance next-generation bioelectronic interfaces. Full article

This paper comprehensively reviews the latest advances in hydrogel-based continuum soft robots. Hydrogels exhibit exceptional flexibility and adaptability compared to traditional robots reliant on rigid structures, making them ideal as biomimetic robotic skins and platforms for constructing highly accurate, real-time responsive sensory interfaces. The article systematically summarizes recent research developments across several key dimensions, including application domains, fabrication methods, actuator technologies, and sensing mechanisms. From an application perspective, developments span healthcare, manufacturing, and agriculture. Regarding fabrication techniques, the paper extensively explores crosslinking methods, additive manufacturing, microfluidics, and other related processes. Additionally, the article categorizes and thoroughly discusses various hydrogel-based actuators responsive to solute/solvent variations, pH, chemical reactions, temperature, light, magnetic fields, electric fields, hydraulic/electro-osmotic stimuli, and humidity. It also details the strategies for designing and implementing diverse sensors, including strain, pressure, humidity, conductive, magnetic, thermal, gas, optical, and multimodal sensors. Finally, the paper offers an in-depth discussion of the prospective applications of hydrogel-based continuum soft robots, particularly emphasizing their potential in medical and industrial fields. Concluding remarks include a forward-looking outlook highlighting future challenges and promising research directions. Full article

Hydrogels are innovative materials characterized by a water-swollen, crosslinked polymeric network capable of retaining substantial amounts of water while maintaining structural integrity. Their unique ability to swell or contract in response to environmental stimuli makes them integral to biomedical applications, including drug delivery, tissue engineering, and wound healing. Among these, “smart” hydrogels, sensitive to stimuli such as pH, temperature, and light, showcase reversible transitions between liquid and semi-solid states. Thermoresponsive hydrogels, exemplified by poly(N-isopropylacrylamide) (PNIPAM), are particularly notable for their sensitivity to temperature changes, transitioning near their lower critical solution temperature (LCST) of approximately 32 °C in water. Structurally, PNIPAM-based hydrogels (PNIPAM-HYDs) are chemically versatile, allowing for modifications that enhance biocompatibility and functional adaptability. These properties enable their application in diverse therapeutic areas such as cancer therapy, phototherapy, wound healing, and tissue engineering. In this review, the unique properties and behavior of smart PNIPAM are explored, with an emphasis on diverse synthesis methods and a brief note on biocompatibility. Furthermore, the structural and functional modifications of PNIPAM-HYDs are detailed, along with their biomedical applications in cancer therapy, phototherapy, wound healing, tissue engineering, skin conditions, ocular diseases, etc. Various delivery routes and patents highlighting therapeutic advancements are also examined. Finally, the future prospects of PNIPAM-HYDs remain promising, with ongoing research focused on enhancing their stability, responsiveness, and clinical applicability. Their continued development is expected to revolutionize biomedical technologies, paving the way for more efficient and targeted therapeutic solutions. Full article

Diabetic wounds are therapeutically challenging because of the complex and adverse microenvironment that impedes healing. Unlike conventional wound dressings, hydrogels provide antibacterial, anti-inflammatory, and repair-promoting functions. In this study, we developed a light-responsive and injectable chitosan methacryloyl (CSMA) hydrogel, incorporating soy isoflavones (SIs) and gold nanoparticles (AuNPs). Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance (1H NMR) spectroscopy analyses confirmed the successful synthesis of the CSMA/SI/AuNP hydrogels. In vitro experiments demonstrated that this hydrogel exhibited exceptional biocompatibility and enhanced the migration of human umbilical vein endothelial cells (p < 0.05), thereby underscoring its potential for promoting angiogenesis. In vivo studies have indicated that hydrogels significantly enhance the rate of wound healing (p < 0.001). Moreover, they facilitate angiogenesis (p < 0.01) and diminish the inflammatory response at the wound site (p < 0.05). Additionally, hydrogels promote collagen deposition and the regeneration of skin appendages. These findings substantiate the hydrogel’s therapeutic potential for diabetic wound care, highlighting its promise for regenerative medicine. CSMA/SI/AuNP represents a significant advancement in diabetic wound treatment, addressing key challenges in wound healing by offering a multifaceted therapeutic approach with broad clinical implications for enhancing patient outcomes in chronic wound management. Full article

Leaky waveguides (LWs) are low-refractive-index films deposited on glass substrates. In these, light can travel in the film while leaking out at the film–substrate interface. The angle at which light can travel in the film is dependent on its refractive index and thickness, which can change with pH when the film is made of pH-responsive materials. Herein, we report an LW comprising a waveguide film made of a synthetic hydrogel containing the monomers acrylamide and N-[3-(dimethylamino)propyl]methacrylamide (DMA) and a bisacrylamide crosslinker for pH measurements between 4 and 8. The response of the LW pH sensor was reversible and the response times were 0.90 ± 0.14 and 2.38 ± 0.22 min when pH was changed from low to high and high to low, respectively. The reported LW pH sensor was largely insensitive to typical concentrations of common interferents, including sodium chloride, urea, aluminum sulfate, calcium chloride, and humic acid. Compared to a glass pH electrode, the measurement range is smaller but is close to the range required for monitoring the pH of drinking water. The pH resolution of the hydrogel sensor was ~0.004, compared to ~0.01 for the glass electrode. Full article