The development of advanced hybrid hydrogels is essential for biomedical applications, such as tissue engineering, drug delivery, and wound healing. The incorporation of additives, such as graphene, imparts specific functional properties to hydrogel networks. In this work, we report the successful integration of few-layer graphene (FLG) into acrylate-endcapped urethane (AUP) hydrogels, resulting in hybrid materials with enhanced structural and functional properties. Notably, the introducton of FLG induces the formation of a porous microstructure within an otherwise non-porous AUP network, representing a simple and effective strategy to generate porosity without the use of porogens or templating methods. This induced porosity is critical for promoting nutrient diffusion and cellular infiltration. In addition to this structural modification, FLG contributes to the reinforcement of hydrogels and influences the crystallization behavior, acting as a nucleating agent, highlighting its role as an active component in the hydrogel matrix rather than a passive filler. A comprehensive characterization, including mechanical, thermal, and morphological analyses, was conducted to elucidate the role of FLG within the hydrogel matrix. The resulting materials exhibit high gel fractions, tunable swelling behavior, and mechanical properties within the range relevant for soft tissue applications. In vitro cytotoxicity assays confirmed the biocompatibility of the FLG-enhanced hydrogels, validating their safety for potential biomedical applications. Antimicrobial assessment demonstrated a limited, concentration-dependent inhibition of bacterial growth, primarily at higher FLG contents. Overall, this study demonstrates a straightforward approach to engineer porous AUP-based hydrogels through FLG incorporation, expanding their potential for biomedical applications.

The rapid expansion of industrial and commercial applications of graphene-based materials (GBMs) has raised increasing concern about their classification as emerging environmental contaminants and their long-term impacts on human and ecosystem health. However, most nanosafety studies still rely on acute, high-dose exposure scenarios that poorly reflect chronic, low-dose exposures likely to occur during manufacturing, handling, use and end-of-life of GBM-containing products. Here, we assessed the hazard of prolonged low-dose exposure to four GBMs, two commercial graphene oxides (GO 1, GO 2) and two few-layer graphenes (FLG 1, FLG 2), using human HaCaT keratinocytes, a non-tumorigenic and genomically stable skin cell line representative of a primary barrier to environmental and occupational contact, and xenografts in athymic mice. Cells were exposed weekly for 1 month (sub-chronic) and 6 months (chronic) to 0.5 and 5 µg/mL, sub-cytotoxic doses previously shown to induce DNA damage without overt cell death. Chronic GO exposure induced coordinated epithelial remodeling compatible with a partial epithelial-mesenchymal transition (EMT)-like state, including E- to N-cadherin switch, loss of occludin, β-catenin relocalization, keratin-to-vimentin intermediate filament reorganization, enhanced extracellular matrix degradation, increased clonogenic growth and nuclear enlargement in vitro. These EMT-like alterations were recapitulated in vivo in xenografts derived from sub-chronically and chronically exposed cells, where GO 2 produced the most pronounced cadherin switch and intermediate filament changes nine weeks after the last exposure, indicating persistence of the phenotype in a more complex microenvironment. Our findings demonstrate that long-term, low-dose exposure to oxidized GBMs at environmentally and occupationally relevant concentrations can promote epithelial plasticity and EMT-associated traits in skin barrier cells, identifying physicochemical properties such as oxidation degree and lateral size as key determinants of chronic hazard. These results highlight the need to consider chronic low-dose exposure scenarios in the environmental and occupational risk assessment and safe-by-design development of graphene-based materials.

Graphene-related materials (GRMs) are revolutionizing sectors such as electronics, energy storage, agriculture, and biomedicine due to their exceptional properties. However, concerns are emerging about their environmental impact, particularly regarding their persistence, potential toxicity to aquatic ecosystems, and challenges in safe disposal. These issues highlight the need for more robust sustainable-by-design and risk-assessment strategies. In this context, this research investigated the influence of GRMs on lignin peroxidase (LiP) and laccase (Lac), key enzymes involved in lignin breakdown with significant potential in bioremediation. These enzymes are crucial for degrading complex molecules, and understanding their interaction with GRMs could provide valuable insights into the degradation of 2D nanomaterials, particularly graphene oxide (GO), few-layer graphene (FLG), and reduced graphene oxide (rGO). In vitro enzymatic assays conducted with varying GRMs concentrations (12.5, 25.0, and 50.0 µg/mL) revealed that Lac remained unaffected, while LiP exhibited a noteworthy reduction in catalytic activity, particularly in the presence of GO at the highest concentration. A sequestration study to quantify the bioavailable fraction confirmed these effects, indicating significant enzyme loss, notably with GO at 50 µg/mL. These findings prompted a mechanistic exploration of enzyme inhibition dynamics, revealing the complex nature of GRM-catalytic enzyme processes. By considering factors such as zeta potential (electrostatic forces), hydrophobicity, dispersion stability, and oxidation state, this study addresses a key knowledge gap and provides a foundation for understanding these interactions, offering crucial insights into the environmental fate of GRMs and guiding their sustainable use and management.

The development of stretchable electrodes is crucial for advancing soft electronics, including biointegrated health systems and wearable devices. In this work, we present a biocompatible and highly conductive stretchable hydrogel electrode fabricated by combining a conductive polymer (PEDOT:PSS) and a thin platinum layer (approximate to 150 nm) deposited on top via radio frequency (RF) sputtering. The 2-hydroxyethyl acrylate (2-HEA) hydrogel acts as a flexible matrix into which the PEDOT:PSS polymer is incorporated, along with -OH groups that ensure strong adhesion of the metal layer to the hydrogel. The resulting electrode achieves a surface resistivity of 0.8 ohm sq-1 (approximate to 8 & times; 106 S m-1) and maintains conductivity even after 500 stretch-relaxation cycles at 70% strain. Unlike conventional electrodes, it exhibits minimal resistance variation (R/R0 approximate to 2) under strain due to a combined "island-bridge" conduction mechanism. Importantly, the electrode preserves its conductivity even after one year of storage under ambient conditions. Additionally, under 40 degrees C and 70% RH for 48 h, the resistivity only shows a slight increase, which is recovered once returned to standard conditions. Furthermore, biocompatibility tests confirm the electrode's suitability for skin-contact applications. This novel approach provides a promising solution for next-generation wearable and implantable bioelectronics, offering an optimal balance between high conductivity, mechanical durability, stretchability and biocompatibility.

A universal mechanochemical methodology is presented for the one-pot synthesis of two-dimensional hybrid nanomaterials. Exfoliation of bulk layered precursors and simultaneous formation of metallic nanoparticles anchored on their surfaces are achieved through ball milling. The process is operationally simple, solvent-free, and environmentally friendly, enabling the scalable preparation of diverse 2D-nanoparticle hybrids from readily available starting materials.

The rising incidence of neurodegenerative diseases has driven the development of advanced 3D scaffolds that better mimic the native neural environment. By incorporating tunable biomaterials such as hydrogels, these systems enable the investigation of how physical cues, including stiffness and spatial confinement or electrical conductivity, regulate neural stem cell fate, neurogenesis, and tissue repair processes. In this study, few-layer graphene (FLG) is incorporated into a photopolymerizable chitosan–acrylamide hydrogel designed as a biomimetic 3D scaffold for neural tissue engineering. The presence of FLG enhances SH-SY5Y cell viability and promotes differentiation towards a neuron-like phenotype, even without external factors, while showing a clear synergistic effect when combined with growth factors. These results are consistent with the electroactive nature of FLG, which provides a combination of electrical and structural cues that support neuronal development and network formation. Overall, FLG behaves as an active component within the matrix, modulating cell response rather than acting as a simple filler. Importantly, these 3D in vitro platforms may contribute to reducing reliance on animal models by providing physiologically relevant systems to study neuronal development and neurodegenerative diseases.

Heavy metal ions pose a significant environmental threat due to their non-degradability and accumulation to toxic levels. In addressing this challenge, we have designed two novel hydrogels through radical polymerization, an efficient and cost-effective method, using sulfonate groups. One hydrogel remained pristine, while the other was hybridized with few-layer graphene (FLG). The incorporation of FLG interacts with the polymeric network without compromising its thermal stability, as confirmed by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). It also reduces pore size (from 42 to 35 mu m), enhances mechanical properties (Young's modulus increased from 32 to 44 kPa), and increases the swelling degree (from 62 to 76), while maintaining a high adsorption capacity. The ability of both hydrogels to adsorb Pb2+, Ni2+, and Cd2+ ions from aqueous solutions was examined. These hydrogels demonstrated high adsorption capacity (qe), with maximum uptake of 631.7 mg/g for Pb2+, 633.3 mg/g for Ni2+, and 373.1 mg/g for Cd2+ in the pristine hydrogels (VBS) and 540.6 mg/g for Pb2+, 615.1 mg/g for Ni2+, and 304.9 mg/g for Cd2+ in the hybrid FLG hydrogels (VBS_G). Adsorption kinetics studies indicated a fit to the pseudo-second-order model for all metal ions. Adsorption isotherms showed that Pb2+, Cd2+ and Ni2+ follow the Freundlich model. To demonstrate reusability and regeneration, hydrogels with adsorbed ions were introduced into acidic media. Evaluating their performance in various water sources, the hydrogels showcased potential as efficient adsorbents for water purification and agricultural applications, offering a promising solution for contaminated water treatment.

We present the synthesis and characterization of a hybrid material comprising silver nanoparticles embedded within a 3D hydrogel network. The use of an aqueous extract of Acanthus mollis as a natural reducing agent facilitates the synthesis process. Acanthus mollis is a perennial, invasive and leafy plant that is widely distributed across the planet. Sequential introduction of silver nitrate solution and the plant extract into the hydrogel yielded a homogeneous dispersion of nanoparticles. The hybrid material, which contains an approximate weight percentage of 9 % silver, was characterized using various techniques, including scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, ultraviolet-visible spectroscopy, and thermogravimetric analysis. Remarkably, and in contrast to the initial hydrogel, the hybrid material was found to be stable at temperatures exceeding 100 °C. This material offers a practical means for preserving silver nanoparticles by preventing aggregation and oxidation thereof. Moreover, the nanoparticles can be safely transported after drying the hydrogel. The incorporation of silver within the hydrogel introduces synergistic effects and specific selectivity, thereby enhancing its applicability across various fields. The nanoparticles exhibit diverse properties, including antioxidant, antibacterial, antifungal, and antidiabetic effects. Additionally, they serve as efficient photocatalysts for dye degradation in aqueous solutions.

Thermoelectric hydrogels have the potential to be used in energy conversion devices for harnessing ubiquitous low-grade heat and generating useful electricity. This can be achieved through the use of thermogalvanic cells based on redox chemistry. While significant attention has been focused toward maximizing voltage for a given temperature gradient in liquid-based thermocells, it is crucial to consider both voltage and current density for accurate power output estimation in the case of gel-based thermocells. Here, we analyze the influence of the functional groups and the redox pair concentration over the voltage and current density in two different hydrogels. Our results confirm a path to enhance the current density in thermogalvanic hydrogels by incorporating a cationic pair into a cationic electroactive network (CN). This approach facilitates the movement of redox pairs, therefore increasing the power density output.

Graphene is the first 2D atomic crystal, and its isolation heralded a new era in materials science with the emergence of several other atomically thin materials displaying multifunctional properties. The safety assessment of new materials is often something of an afterthought, but in the case of graphene, the initial isolation and characterization of the material was soon followed by the assessment of its potential impact on living systems. The Graphene Flagship project addressed the health and environmental aspects of graphene and other 2D materials, providing an instructive lesson in interdisciplinarity - from materials science to biology. Here, the outcomes of the toxicological and ecotoxicological studies performed on graphene and its derivatives, and the key lessons learned from this decade-long journey, are highlighted.

This study introduces a novel grip pressure measuring device for hand rehabilitation, utilizing a 2-hydroxyethyl acrylate (2-HEA)-based conductive hydrogel. The hydrogel, fabricated through a UV-initiated 3D printing process, demonstrates robust mechanical properties, including a Young’s modulus of 44.8±8.0 kPa and high fatigue resistance, making it suitable for repeated deformation. Electrical properties were evaluated by an impedance analyzer achieving a sensitivity of 8.54 kΩ when the hydrogel is deformed by 1%. The device incorporates a unique air-chamber design and a four-probe method for precise resistance measurement, with signals processed via custom electronics. Experimental validation, involving a real-time graphical pressure control task, confirmed the accuracy and usability of the device. This hydrogel-based sensor offers a promising tool for advanced rehabilitation monitoring and control, particularly for detecting low-pressure variations, which are essential for early-stage rehabilitation or certain neuromuscular conditions.

This paper presents the design, development, and control of a low-cost two-flexible-finger robotic gripper for grasping fragile objects. The gripper is fabricated using 3D-printed materials, with flexible fingers made from TPU (95A shore hardness), equipped with conductive gel-based contact sensors and strain gauges for force feedback. The system is driven by a DC motor, and the control scheme includes position-force control to ensure delicate grasping. The gripper operates in two stages: object approach and controlled force application, with adaptive control parameters based on sensor feedback to prevent damage to fragile items. Experimental tests demonstrate the gripper’s capability to grasp fragile objects such as Christmas ornaments and eggs, validating the design and control strategy.

Graphene-related materials (GRMs) are used in many innovative applications for their outstanding physicochemical properties. Their possible release could have critical consequences for the environment. According to a European Union regulation, one of the test guidelines (TG) that must be applied to check the environmental hazard of new substances is the OECD TG 201 - Algae and Cyanobacteria Growth Inhibition Test. It was developed for water-soluble substances, whereas GRMs are not: dispersed in aqueous media, they tend to aggregate and settle, changing their bioavailability. This work aims to evaluate the applicability of the TG 201 to GRMs by investigating the stability of GRMs dispersions (GDS) in the TG 201 medium, focusing on the stability criterion of TG 201, i.e. maintaining +/- 20 % of the nominal initial concentration. Based on flow-cytometry, Turbiscan and Utermohl sedimentation chamber measurements, the following factors were tested: (i) particle composition and (ii) concentration; (iii) application of turbulence; (iv) addition of dispersants; (v) presence/ absence of the target organism. Strong agglomeration/aggregation and sedimentation phenomena were observed for all materials under all tested conditions, thus the stability criterion of TG 201 was not met. Nevertheless, this can be satisfied by allowing an adequate period of time (approx. 6 h) for the GRM dispersion to stabilize after its preparation. Only then, a detailed physico-chemical characterization of the suspended material is required, which must be reiterated at the end of the test.

Hydrogels have emerged as a promising sustainable alternative to proton exchange membranes (PEM) as components of microbial fuel cells (MFCs). This study investigates the feasibility of the replacement of the separator element by comparing the performance of air-breathing and bicompartmental cells consisting of Membrane Electrode Assemblies (MEAs) and Hydrogel Electrode Assemblies (HEAs) in terms of electrochemical efficiency, biocompatibility and chemical stability. Results demonstrate the feasibility of the replacement, which becomes especially important in terms of the necessary reduction of fluorinated membranes. However, the voltage generated by HEA-based configurations was slightly lower than that achieved by cells equipped with MEAs. In addition, they indicate that the two-compartment HEA configuration is more suitable than the air-breathing one to ensure proper acclimation of anaerobic electrogenic bacteria in the anode and prevent desiccation. This work highlights that hydrogels represent an encouraging, available and environmentally friendly solution for MFCs, which could accelerate the transition to energy independence and sustainable technological advances in a variety of applications.

Soft materials represent an interdisciplinary frontier in modern science, combining theoretical and experimental knowledge from diverse fields in both fundamental research and cutting‐edge technological applications. Hydrogels have garnered significant interest due to their unique properties. Nevertheless, practitioners often lack sufficient information on how to synthesize hydrogels, and the final composition is traditionally determined through trial and error. This study introduces a novel methodology to identify the optimal composition prior to experimentation. An ordinal regression model for mixture experiments to simulate the synthesis process, an adaptation of the Particle Swarm Optimization algorithm to tackle the complex optimization problem, and an open‐access interactive app to facilitate the calculations are proposed. This work represents a milestone in the hydrogel synthesis field: first, because of the savings in human, economic, and material resources it entails, the latter being consistent with the commitment to environmental sustainability; second, because it aligns with the principles of open science, providing an accessible and reproducible tool for the entire scientific community; and finally, because it seeks to overcome the barrier of expert knowledge to generalize the use of hydrogels. It represents the first step toward the development of an AI system specialized in the design of novel smart materials.

Diabetes remains one of the most prevalent chronic diseases globally, significantly impacting mortality ratetables. The development of effective treatments for controlling glucose level in blood is critical to improve the quality of life of patients with diabetes. In this sense, smart optical sensors using hydrogels, responsive to external stimuli, have emerged as a revolutionary approach to diabetes care. In this study, changes in the optical properties of a hydrogel are employed for monitoring α-glucosidase activity, a critical enzyme involved in diabetes mellitus type II due to its role in breaking terminal α-glycosidic bonds, releasing α-glucose. The enzyme is encapsulated within a triazine-based hydrogel that exhibits intrinsic blue fluorescence. Upon hydrolysis of the substrate p-nitrophenyl-α-D-glucopyranoside (p-NPG) by α-glucosidase, the fluorescence is quenched due to the release of p-nitrophenol (PNP). However, when exposed to potential antidiabetic drugs, the enzyme's activity is inhibited, and the hydrogel's fluorescence remains intact. This ON/OFF fluorescence-based assay enables rapid screening of drug candidates by evaluating their ability to inhibit α-glucosidase enzymatic activity. Sensor optimization involves conducting swelling studies, fluorescent assays, reusability tests and a trial with a real antidiabetic drug. This innovative approach holds potential for enhancing antidiabetic drug screening and management, offering a more accessible and efficient solution compared to traditional biosensors.

Hexagonal boron nitride (hBN) is a promising two-dimensional (2D) material of interest to the scientific community and industry due to its revolutionary physico-chemical features. Skin contact is one of the most feasible exposure routes both for workers, producing hBN, and consumers, using hBN-enabled nanotechnologies. Hence, the toxic potential of hBN at the cutaneous level was evaluated following an in vitro approach with different degree of complexity, using a simplified cell model (HaCaT keratinocytes), and a more predictive and complete skin tissue (a 3D model of human epidermis). Despite its significant uptake by keratinocytes, hBN exerted only weak adverse effects, such as slight alterations of cells parameters indices of cytotoxicity (cell viability, cell mass and plasma membrane integrity) and mitochondrial-related dysfunctions (mitochondrial depolarization, ATP depletion and reactive oxygen species production), detectable only at high concentrations (>25 µg/mL) and mainly after a long exposure (72 h). In addition, adoption of the OECD TG 431 and 439 on the 3D reconstructed human epidermis model demonstrated hBN as a non-corrosive and non-irritant material, with an extremely low pro-inflammatory potential. These results denote a good biocompatibility of hBN at the skin level.

The assembly of nanomaterials into larger, functional frameworks is a growing area of nanotechnology. This study focuses on the reversible aggregation of carbon nanohorns (CNHs) functionalized with quaternary ammonium salts (Q-CNHs) using negatively charged azobenzenes as ionic glue. CNHs, characterized by high surface area were modified through a three-step process to enhance their aqueous dispersibility. A series of azobenzenes with varying numbers of carboxylate groups were synthesized to investigate their effect on Q-CNHs aggregation. The synthesis involved reductive coupling and the Mills reaction. Aggregation experiments demonstrated that the efficiency of Q-CNHs precipitation correlated with the azobenzene charge. Notably, the [2,2] azobenzene, with four carboxylate groups, was the most effective, forming frameworks around 1 mu m in size. The reversibility of the assemblies was confirmed through multiple sonication and stirring cycles, with no significant fatigue observed. This dynamic behavior was monitored using scanning electron microscopy and dynamic light scattering, highlighting the potential for creating recyclable nanomaterial frameworks. This study underscores the importance of molecular charge in nanoparticle assembly and paves the way for designing responsive and reconfigurable nanostructures.

The development of graphene-enabled products in a variety of industrial sectors like medical devices, textiles, aerospace, or food contact materials has raised significant regulatory challenges with regards to risk assessment. The work performed under the Graphene Flagship Work Package SH11 termed SafeGraph, aimed to identify challenges while implementing regulation as well as to develop a regulatory roadmap addressing these issues. This study explores and discusses the regulatory gaps and safety assessment challenges associated with graphene-enabled products and based on regulatory requirements with a particular focus on risk assessment, exposure concerns, and potential environmental impacts. Through case studies involving skin sensors, drinking water filters, wearable electronics, and de-icing systems for aircrafts, we identified critical safety and compliance issues across various sectors. The work used four Graphene Flagship case studies as showcases to address the above markets (CHEMsens, GRAPHIL, WEARgraph and GICE). These case studies underscore the need for updated regulatory guidelines tailored to graphene’s unique properties. This study provides insights into current challenges of assessing risks and proposes steps to ensure safe and sustainable commercialisation of graphene-based products, advocating for harmonised regulatory frameworks.