Search Results (282)

A thermoreversible dynamic covalent network was constructed in recycled polyethylene terephthalate (RPET) via Diels–Alder (DA) chemistry to enhance mechanical performance, reprocessability, and self-healing. Furan-functionalized RPET (RPET-3F) was first prepared from maleated RPET (RPET-MA), followed by crosslinking with bismaleimide (BMI) at different feed ratios. FTIR spectra confirmed the successful grafting of furan groups and the formation of DA adducts. With increasing BMI content, the gel fraction and crosslink density increased substantially, whereas the swelling ratio decreased, indicating the progressive development of a three-dimensional network. RPET-3F-2B showed the highest network integrity among all samples. DSC analysis revealed a distinct retro-DA dissociation peak at 143 °C and a recrosslinking peak near 124 °C, confirming the thermal reversibility of the DA network. Owing to the optimized network structure, RPET-3F-2B exhibited the best mechanical properties and excellent reprocessability, retaining stable performance after three hot-pressing cycles. After repeated reprocessing, its tensile strength remained 74% higher than that of RPET-MA, while the elongation at break was still improved by about 10%. Moreover, the sample showed efficient thermally induced self-healing at 150 °C, with surface cracks nearly disappearing after 4 h. These results demonstrate that DA chemistry offers a promising route to the high-value reutilization of RPET into recyclable, multifunctional polymer materials. Full article

Transforming existing structural surfaces into sensing interfaces offers a promising route for scalable hydrogen monitoring in hydrogen-handling facilities, where leakage poses significant safety risks, addressing the limitations of conventional point-based sensors. In this study, a surface-integrated ZnFe₂O₄–CNT (ZFC) composite coating is developed as a potentially retrofit-compatible sensing solution to enable hydrogen sensing directly on cementitious materials, combining material-level functionality with data-driven concentration prediction. The ZFC composite was synthesized via a hydrothermal method followed by CNT functionalization and composite formation, and was then applied onto cement-based substrates using a thickness-controlled coating approach. Structural and morphological characterization (XRD, FESEM, TEM, BET) confirmed the formation of a hierarchical, porous architecture, while hydrogen sensing performance was evaluated under controlled thermo-hygrometric conditions (24–72 °C, 32–87% RH) at 10,000 ppm H₂. The sensor exhibited stable and reversible responses, with optimal performance at 39–52 °C and a minimum response time of 18 s. An XGBoost model enabled accurate prediction of hydrogen concentration, achieving R² ≈ 0.92 and RMSE ≈ 820 ppm under dynamic exposure. These results demonstrate that coupling redox-active oxide surfaces with conductive CNT networks enables effective surface-based chemiresistive sensing under realistic conditions. The proposed system transforms conventional cementitious materials into smart, surface-integrated hydrogen sensing systems, offering a scalable and retrofit-compatible approach for real-time monitoring in hydrogen-related infrastructure. Full article

Background: Overexpression of immune cell populations leads to self-amplifying cytokine loops, contributing to chronic inflammation in both allograft rejection and autoimmune conditions. Tacrolimus (TAC), despite being a potent immunosuppressant, has limitations; its systemic adverse effects include nephrotoxicity, neurotoxicity, and high variability in tissue exposure in patients. Currently available therapeutic options are limited by the lack of targeted and localized drug delivery systems, resulting in ineffective control over drug-release behavior. Moreover, TAC being highly lipophilic poses challenges for formulation development. To address these gaps, this study focuses on developing a thermoresponsive hydrogel platform comprising distinct nanocarriers for localized delivery of TAC. The nanocarriers include nanoemulsion (NE) and micelles as TAC carriers, and their particle sizes are specifically engineered at the nanoscale for differential release behavior and to support immune cell targeting (macrophages and T-cells). Incorporation into a thermoresponsive hydrogel matrix enables it to act as a local depot at the injection site and deliver TAC with a slow, extended-release profile. Methods: TAC was loaded into a coconut-rich lipid-phase-based NE via high-pressure microfluidization. Simultaneously, TAC-loaded micelles were optimized using a full-factorial design of experiments (DoE) and manufactured via the thin-film hydration method. Both nanocarriers were evaluated for long-term colloidal stability assessments. Hydrogels were produced maintaining aseptic conditions for sterile batch production. Rheological characterization was performed to assess sol-gel transition, thermoreversibility, and injectability, and in vitro release studies were conducted to evaluate TAC diffusion from the developed nanoformulations. Results: Developed nanocarriers resulted in distinct particle sizes in NE (80–85 nm) and micelles (15–17 nm) with successful TAC loading maintaining long-term colloidal stability. The developed TAC-loaded dual-nanocarrier hydrogel (Dual-HG) showed thermoresponsive behavior and gelation at 37 °C, forming as a local depot. In vitro release studies showed slow and extended tacrolimus release from hydrogels and demonstrated particle size-dependent release behavior between the NE and micelle. Conclusions: Therefore, our study highlights a novel dual nanocarrier hydrogel platform combining TAC-NE and TAC-micelle for localized delivery. The findings support that nanocarriers can be engineered to modulate drug diffusion behavior. Notably, the dual nanocarrier within a thermoresponsive hydrogel platform can be used to deliver one or multiple drugs locally, minimizing systemic exposure when sustained local immunosuppression is required. The 25 mL scale sterile batch production of hydrogels emphasizes their suitability for future translational applications. Full article

The swelling-regulated transport properties of modified and cross-linked HPC-based hydrogel formulations containing NaCMC and citric acid were studied as stimuli-responsive polymeric membranes under various conditions, including deionized water. Physiological conditions were simulated by evaluating various pH conditions (1.2, 6.8, and 7.4). The pseudo-second-order kinetic model best described the swelling process, suggesting that both solvent uptake capacity and polymer network relaxation contribute to the extent of swelling. The swelling behavior of the hydrogel formulations was significantly influenced by salt concentration. The modified HPC hydrogel system exhibited stimuli-responsive swelling–switching behavior under saline, water/ethanol, and acidic/basic environments, demonstrating reversible swelling–deswelling cycles. Maximum swelling was observed in water at pH 7.4. In contrast, abrupt deswelling in an ethanol solution at pH 1.2 reduced hydrogel swelling and water uptake. The effect of temperature on the swelling behavior of the hydrogel and its thermo-responsive swelling behavior was also evaluated. Drug release behavior suggested diffusion-mediated release through the swelling hydrogel matrix. These findings suggest that the modified HPC-based hydrogel system may be useful for pH-responsive oral drug delivery applications. Full article

To address the large deviation in annular trapped pressure prediction during testing and production stages of deepwater high-temperature and high-pressure wells, conventional models neglect the elastic uplift effect of the wellhead. This study overcomes the limitations of the plane strain model and establishes a three-dimensional thermos–hydro–mechanical coupled annular pressure prediction model based on the longitudinal stiffness constraint of the subsea wellhead. The deepwater wellbore–formation system is treated as a composite elastic structure. A generalized plane strain assumption is introduced to define the elastic boundary conditions and longitudinal segmentation characteristics of the wellhead. Based on generalized Hooke’s law, the three-dimensional stress–strain constitutive equation of casing is modified. A displacement model incorporating axial–radial coupling is derived, and an equivalent longitudinal stiffness coefficient of the wellhead is introduced. A coupled axial force equilibrium equation and a three-dimensional annular volume compatibility equation are established. Considering multi-annulus coupling, a volume compatibility matrix equation is formulated, and a successive approximation iterative algorithm with a relaxation factor is developed. Using a deepwater high-temperature, high-pressure gas well in the South China Sea as a case study, the effects of wellhead stiffness, free section length, and annular temperature rise on annular pressure are investigated via a single-variable method and compared with traditional rigid models. Results show that the subsea wellhead exhibits elastic uplift behavior. Its longitudinal stiffness has a reverse S-shaped nonlinear influence on annular pressure. Increasing the free section length significantly reduces annular pressure. The proposed model predicts values 17–21% lower than traditional rigid models, providing a more realistic representation of annular pressure evolution. The findings offer theoretical support and engineering guidance for deepwater well integrity design and annular pressure risk management. Full article

Acrylated epoxidized soybean oil (AESO) is a bio-based, biocompatible, and biodegradable photopolymerizable resin that exhibits shape-memory behavior, making it attractive for a wide range of biomaterial applications. Despite various strategies to fabricate porous AESO scaffolds for tissue regeneration, achieving high pore interconnectivity remains challenging. Herein, we demonstrate the utility and versatility of thermoreversible terpenes as porogens in AESO to enable the formation of highly aligned and interconnected pore architectures. More specifically, a blend of 90 wt% camphene and 10 wt% camphor was employed as the terpene system, since it could be completely melted at 70 °C, uniformly mixed with liquid AESO, and subsequently crystallized at −20 °C. This process generated a bicontinuous network comprising terpene crystals and liquid AESO, thereby enabling efficient UV photopolymerization of AESO. Following terpene removal via freeze-drying, highly aligned pore networks with excellent pore interconnectivity were obtained, which are hardly achievable using conventional liquid or solid porogens. The porosity and mechanical properties of the AESO scaffolds were tuned by adjusting terpene content. Porosity increased from 61.5 to 81.5% as terpene content rose from 60 to 80 vol%. As a result, tensile strength decreased from 0.29 ± 0.045 to 0.17 ± 0.017 MPa, while elongation at break increased from 20.2 ± 4.9 to 35.5 ± 1.34%. Furthermore, this approach is compatible with vat photopolymerization (VP), a 3D printing technique. As a proof of concept, dual-scale porous AESO scaffolds, composed of unidirectional channels surrounded by highly aligned porous frameworks, were successfully fabricated. These results indicate that a variety of dual-scale porous AESO scaffolds, with greatly enhanced mechanical properties at given porosities coupled with outstanding tissue regeneration, can be produced through VP using terpene porogens, in contrast to conventional porous scaffolds comprising uniform porous frameworks. Full article

Background: Pinellia ternata is a major medicinal herb widely utilized in traditional medicine, but is sensitive to high temperature, which often triggers a severe “sprout tumble” phenomenon. Methods: To elucidate the molecular mechanisms of heat tolerance in P. ternata, we screened two contrasting germplasms: the heat-tolerant JBX1 and the heat-sensitive XBX4. In the present study, a combined analysis of physiology, transcriptome, and metabolome was performed on JBX1 and XBX4 under heat stress at 40 °C. Results: JBX1 exhibited significantly greater leaf thickness, higher basal chlorophyll content, more stable antioxidant enzyme activities, and lower oxidative damage than XBX4 under heat stress. Transcriptomically, JBX1 maintained elevated basal expression of genes encoding key enzymes in carbon fixation, amino acid metabolism, and phenylpropanoid biosynthesis, as well as those encoding heat shock transcription factors (HSFs), heat shock proteins (HSPs), and the thermosensor Thermo-With ABA-Response 1 (TWA1). Metabolomically, JBX1 accumulated higher levels of key primary metabolites, antioxidants, and protective phenylpropanoids under both control and heat conditions. Notably, a “polarity reversal” emerged in nitrogen metabolism, where core amino acids accumulated in JBX1 but were depleted in XBX4. Integrated analysis revealed a more coordinated gene–metabolite network in JBX1 involving the phenylpropanoid, ATP-binding cassette (ABC) transporter, and glutathione pathways. Conclusions: Our findings demonstrate that JBX1 possessed stronger basal thermotolerance, which is derived from coordinated establishment of higher constitutive metabolic reserves and efficient dynamic metabolic reprogramming. This study provides insights into the molecular mechanisms of heat stress in P. ternata. Full article

Kappa-carrageenan (κ-CRG) forms thermo-reversible physical hydrogels via a coil–helix transition and helix bundling, but its sulfate-driven electrostatic repulsion limits mechanical robustness and control over aqueous disintegration. Here, we show that plant-derived polyphenols reprogram κ-CRG gel through sulfate-directed binding in a structure-dependent manner. Tannic acid (TA) selectively engages κ-CRG sulfate groups, yielding transparent gels and a >5-fold increase in storage modulus, whereas the same TA triggers turbidity and precipitation in sulfate-free agarose, supporting sulfate-mediated specificity. Using monomeric pyrogallol as a galloyl analogue, we demonstrate that monovalent interactions partially reinforce κ-CRG but lack cooperative stabilization. Intervention timing further separates mechanism. Pyrogallol produces pathway-dependent mechanics and gelation temperature, while TA is stage-insensitive, consistent with multivalent network annealing. In simulated gastric/intestinal fluids, pyrogallol/κ-CRG gels retain morphology longer, whereas TA/κ-CRG ones disintegrate rapidly yet exhibit strong adhesion to rough substrates and human skin. These findings provide a fully food-grade route to tune κ-CRG mechanics, thermal behavior, adhesion and programmed disintegration. Full article

Inspired by their biocompatibility and thermoreversible gelation—transitioning from room temperature liquids to body temperature gels—Pluronic hydrogels were employed in this study to optimize intracanal penetration and ensure medicament stability. We developed a silver nanoparticle (AgNP)-loaded Pluronic gel (AgNPs-P-gel) as a biocompatible, easily removable intracanal medicament. Following PRILE 2021 guidelines, AgNPs-P-gels (F127/F68) were evaluated for gelation, AgNP release, and antibacterial activity against Enterococcus faecalis and Streptococcus mutans via minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and growth curves. Biofilms in bovine teeth were quantified using CFUs and scanning electron microscope (SEM) imaging. Biocompatibility was tested in L-929 fibroblasts using MTT assays and RT-qPCR for pro-inflammatory cytokines (IL-6, TNF-α, IL-1β). Removal efficacy from bovine canals was microscopically scored. The optimized formulation (20% F127, 7.5% F68) gelled at 34 °C with sustained release over 168 h. AgNPs-P-gel showed strong antibacterial activity (MIC: 25–50 µg/mL). In ex vivo models, 100 µg/mL AgNPs-P-gel (AgNPs-100-P-gel) reduced bacterial counts comparably to calcium hydroxide and chlorhexidine, but with lower cytotoxicity. Although inducing cytokine expression similar to conventional medicaments, AgNPs-P-gel demonstrated significantly superior removability. Thermoreversible AgNPs-P-gel offers sustained antimicrobial action, favorable biocompatibility, and superior removability, potentially improving endodontic disinfection predictability as a calcium hydroxide alternative. Full article

Oleuropein, the principal secoiridoid phenolic compound of olive leaves (Olea europaea L.), is recognized for its broad-spectrum antimicrobial, antibiofilm, antioxidant, and tissue-regenerative properties. However, its effective local therapeutic application remains challenging due to rapid clearance from the site of administration and limited residence time. In this study, an oleuropein-rich aqueous olive leaf extract was incorporated into a thermoresponsive sol–gel delivery system designed for localized application. The formulation was engineered to remain in a low-viscosity sol state at room temperature and to undergo a temperature-triggered sol-to-gel transition near physiological temperature (~33 °C), enabling in situ gel formation. Oleuropein content was quantified using a validated HPLC method, and the formulation was characterized with respect to physicochemical parameters, thermoreversible gelation behavior, particle size distribution, mechanical properties, and spreadability. Biological performance was evaluated through in vitro cytocompatibility (MTT assay), fibroblast migration (scratch assay), and collagen deposition (Sirius Red staining) in L929 fibroblasts, as well as antibiofilm activity against representative Gram-positive and Gram-negative bacterial strains. The developed sol–gel system demonstrated stable physicochemical characteristics, rapid and reversible thermogelation, suitable mechanical and spreading properties, concentration-dependent inhibition of biofilm formation, and acceptable cytocompatibility within the tested concentration range. Notably, the formulation supported fibroblast viability and collagen-associated responses at optimized concentrations. Overall, the results indicate that the proposed thermoresponsive sol–gel formulation represents a promising strategy for the localized delivery of oleuropein-rich olive leaf extract, combining physicochemical stability with dual wound-healing and antibiofilm functionality. Full article

This review comprehensively examines the influence of clay plasticity on thermally induced volume changes in saturated clays, which is a critical factor in the design and performance of energy geostructures, nuclear waste repositories, and thermal ground improvement systems. This study synthesises experimental and theoretical findings, demonstrating that the plasticity index and mineralogical composition significantly govern the magnitude and nature of volume change during heating and cooling cycles, with stress history playing a pivotal role. Unlike previous review papers that primarily discuss general thermo-mechanical behaviour or constitutive modelling frameworks, this review explicitly focuses on plasticity as the central unifying parameter influencing thermally induced volume change. It further provides a structured synthesis that integrates plasticity, stress history, and microstructural mechanisms. Normally consolidated clays exhibit irreversible thermal contraction, which intensifies with plasticity, whereas highly overconsolidated clays typically exhibit reversible expansion. Lightly overconsolidated clays exhibit transitional behaviour characterised by initial expansion followed by collapse. This review links these macroscopic responses to microstructural mechanisms, including interparticle physicochemical forces, diffuse double-layer dynamics, and bound water behaviour, highlighting the limitations of idealised electrochemical models and emphasising the importance of micromechanical processes. It further explores how plasticity modulates temperature-dependent reductions in preconsolidation pressure, thermal softening, cyclic thermal deformation, and time-dependent thermal creep, with higher plasticity clays showing greater sensitivity and longer stabilisation periods. The findings underscore the necessity of incorporating plasticity and stress history into constitutive models to accurately predict the thermo-mechanical behaviour of clays under service conditions, with significant implications for the long-term reliability of thermal geotechnical applications. Full article

The 4D printing of thermo-responsive shape-memory multicomponent polymer composites, which possess the ability to change shape by exposure to heat, has attracted much attention in recent years because of their scientific and technological significance. In the present study, we investigate shape memory performance of a polylactic acid-polycaprolactone-graphene nanocomposite activated directly by increasing the environmental temperature and indirectly, by Joule heating. The incorporation of graphene within the shape-memory biopolymer blend allowed formation of a programmable conduction path, whose electric properties are intimately coupled to thermo-mechanical processes. Advanced rheological, thermal, and thermo-mechanical properties were evaluated and related to the structure of nanocomposite. The electrically and thermally stimulated shape memory and self-healing behavior of the nanocomposite based on polycaprolactone/poly(lactic) acid blend reinforced with graphene nanoplatelets (PCL/PLA/GNP) were investigated. The shape memory tests revealed a good reversibility of 76% between the temporary and permanent states of the samples bent to 180 degrees and a high healing efficiency of 96% if stimulated by Joule heating. The highly electroactive nanocomposite demonstrated a great potential for 4D-printing of objects with complex structures, shapes, and electrically-stimulated shape-memory and self-healing functions. The nanocomposite is biodegradable, recyclable, and reusable, which may reduce the carbon footprint of the rapidly developing additive technology. Full article

This review presents a comprehensive analysis of modern thermosensitive polymer systems for in situ systems (ISSs) which are used for targeted drug delivery in situ. The main classes of polymers used to create “smart” hydrogels that undergo a “sol–gel” phase transition in response to a temperature stimulus in the physiological range are considered. Key representatives of thermosensitive matrices are described in detail: synthetic block copolymers (poloxamers, block copolymers of polylactic-co-polyglycolic acid with polyethyleneglycol, etc.) and natural, modified natural, and semi-synthetic polymers (chitosan, including in combination with β-glycerophosphate, xyloglucan, etc.). This paper systematizes the advantages and disadvantages of various thermosensitive systems and highlights the key risks in their pharmaceutical development, including the influence of the nature and concentration of the active pharmaceutical ingredients and excipients on the rheological properties and phase transition temperature. Particular attention is paid to the difference between thermoreversible and irreversible gel-forming systems. Modern in vitro, ex vivo, and in vivo methods for evaluating critical quality parameters of thermosensitive systems, such as gelation temperature and time, gel strength, mucoadhesive properties, and release kinetics, are discussed. The need to develop standardized and biologically relevant methods to improve the reproducibility and success of preclinical studies is emphasized. The review is intended to help researchers to make informed choices about polymer matrices and optimize compositions for successful pharmaceutical development. Full article

The aim of this study was to investigate the effect of hemp protein addition on the structural, rheological, textural, color, and bioactive properties of gelatin hydrogels. Composite systems containing 0–20% hemp protein were analyzed to clarify the mechanism of interaction with the gelatin matrix and to determine whether hemp protein acts as a passive filler or an active structure-forming component. In all formulations, the gelatin concentration was kept constant at 5% (w/w), while hemp protein was added at increasing levels without replacing the gelatin phase, resulting in systems with increasing total solid content. The addition of hemp protein significantly enhanced water-holding capacity and gel strength, as confirmed by rheological measurements and texture profile analysis. Thermorheological analysis revealed a gradual transition from a classic thermoreversible gelatin gel to reinforced composite networks, with the viscoelastic response increasingly governed by the hemp protein structure at higher concentrations (15–20%). Frequency- and amplitude-sweep tests demonstrated improved mechanical stability and reduced frequency dependence. FTIR analysis indicated reorganization of hydrogen bonding and an increasing contribution of hydrophobic interactions related to the lipid fraction of hemp protein. Furthermore, the addition of hemp protein led to a marked increase in antioxidant activity (ABTS and FRAP) and significant changes in color parameters. These results demonstrate that hemp protein functions as an active structural and functional component in gelatin hydrogels, enabling the development of materials with tailored mechanical properties and enhanced bioactivity. Full article

The formation of recyclable polyethylene materials is significantly limited by traditional crosslinking methods, which involve solvent-heavy processes and permanent chemical bonds that cannot be undone. Herein, we report an environmentally friendly and scalable approach to construct a thermo-reversible polyethylene network (PE-g-DA) via solvent-free, one-step melt processing based on furan–maleimide Diels–Alder (D–A) dynamic covalent chemistry. Furan-functionalized polyethylene was dynamically crosslinked with bismaleimide during melt mixing, fully compatible with conventional polyolefin processing techniques. FTIR spectroscopy, temperature-dependent solubility, and differential scanning calorimetry collectively confirm the reversible formation and dissociation of D–A adducts, enabling thermal switching of the network structure. Equilibrium swelling experiments based on the Flory–Rehner model indicate that the crosslink density can be precisely controlled by varying the bismaleimide content. As a result, PE-g-DA exhibits significantly enhanced tensile strength while maintaining high ductility at moderate crosslink densities. Notably, the dynamic network allows efficient thermal reprocessing, with recycled samples retaining approximately 93% and 80% of their original tensile strength after the first and second reprocessing cycles, respectively. Moreover, intrinsic thermal self-healing behavior is directly visualized by scanning electron microscopy at 120 °C. This work demonstrates that combining dynamic Diels–Alder chemistry with solvent-free melt processing offers a practical and sustainable route to recyclable, reprocessable, and self-healable polyethylene materials with clear potential for large-scale industrial production. Full article