Dual Crosslinking Research Articles

Waterborne polyurethane based on dual crosslinked structure with excellent mechanical properties, water and corrosion resistance

Due to the increased presence of hydrophilic groups in waterborne polyurethane (WPU) coatings, consequently leading to compromised corrosion resistance and reduced service life. To solve the problem, a series of waterborne polyurethanes were synthesized via internal emulsification using dicyclohexylmethane diisocyanate (HMDI) and polytetrahydrofuran ether diol (PTMG) as the primary raw materials. The triethanolamine (TEOA) was used as a crosslinking agent and corrosion inhibitor, while N- (β-aminoethyl) -γ-aminopropyl trimethyl-(ethyl) oxy-silane (KH-792) was introduced as a coupling agent to establish a system with a dual crosslinking structure. The crosslinking degree of the double network structure can be adjusted by changing the amount of KH-792. Then the influence of KH-792 content on the performance of SWPU dispersions and film were studied. The research shows that the waterborne polyurethane with a KH-792 content of 3 wt% exhibits exceptional mechanical strength, reaching 34.64 MPa, with only 3.32 % water absorption and an adhesion strength of 2.64 MPa. Furthermore, it exhibited a high impedance modulus (2976.4 Ω/cm2) at low frequencies. Therefore, this compound holds promising potential for application in anti-corrosion coatings field.

Using tannin as a biological curing agent to design fully bio-based epoxidized natural rubber/polylactic thermoplastic vulcanizates with mechanical robustness and multi-stimuli-responsive shape memory properties

To effectively mitigate carbon emissions and promote sustainability in the polymer field, biological macromolecules have emerged as a prominent strategy for fabricating functional materials. Herein, tannin (TA) was used as a biological curing agent to design fully bio-based polylactic/epoxidized natural rubber thermoplastic vulcanizates (PLA/ENR TPVs) with mechanical robustness and multi-stimuli-responsive shape memory properties. A dual cross-linking network, comprising both covalent bonds and hydrogen bonds, was successfully constructed in the ENR phase. A special co-continuous morphology was concomitantly constructed in the TPVs, which promoted effective stress transfer between the PLA and ENR phases, endowing the TPVs with balanced stiffness-toughness and shape memory properties. Moreover, the photothermal effect of TA also made it respond to near-infrared light and sunlight, which achieved the non-contact multistage shape memory performance, revealing the significant potential of the TPVs in the field of actuators.

Facile fabrication of a starch-based wood adhesive showcasing water resistance, flame retardancy, and antibacterial properties via a dual crosslinking strategy

The demand for non-toxic, environmentally friendly, easily processable, water-resistant, flame-retardant and antimicrobial adhesives in the wood processing industry is becoming increasingly urgent. Few adhesives can both simultaneously possess these functions and synthesis easily. This paper presents a one-pot process utilizing corn starch, sodium hypochlorite, itaconic acid, and borax to synthesize a starch-based adhesive with dual crosslinking. Initial crosslinking takes place between the carboxyl groups of itaconic acid and hydroxyl groups on oxidized starch due to the formation of ester bonds. Secondary crosslinking occurs borate ester bonds between starch hydroxyl groups and boric acid. The entire reaction process is environmentally benign, generating no waste, with all reactants converted into final products, aligning with “green” chemistry principles. When used to bond wooden boards, this adhesive achieved a dry shear strength of 5.34 ± 0.24 MPa, and a wet shear strength of 1.22 ± 0.06 MPa after soaking in water. Additionally, this starch-based adhesive exhibited antibacterial properties against Escherichia coli (ATCC 8739) and Staphylococcus aureus. Moreover, with borax incorporated, the adhesive demonstrated flame-retardancy. The limiting oxygen index for bonded wooden boards was 30.9 %, qualifying it as a flame-retardant material. These multiple functions render it promising for applications in the wood processing industry.

3D-printed artificial cornea featuring aligned fibrous structure and enhanced mechanical strength

The global shortage of donor eye bank tissue has significantly impeded advancements in biomaterial for corneal implantation. To address this issue, we have developed a 3D-printed artificial cornea using a composite hydrogel of sodium alginate (SA) and cellulose nanofibers (CNF), crosslinked with poly-L-lysine-co-L-glutamic acid (PLL80GA20, PG) and calcium chloride (CaCl2, CC). The 2 wt% SA/CNF composite hydrogel offers several advantages, including low toxicity, cost-effectiveness, excellent printability, and high mechanical strength, even with low crosslinker concentrations. The PG was synthesized via ring-opening polymerization of L-glutamate N-carboxyl anhydride (BGNCA) and L-lysine N-carboxyl anhydride (CBZNCA). The purity of the monomers was verified through DSC analysis, revealing a melting point of 97 ℃. The molecular weight of the synthesized PG was determined to be 47 kDa. A dual crosslinking strategy was employed, starting with electrostatic crosslinking, followed by ionic crosslinking using varying concentrations of PG and CC at different effective charge concentrations of 6.25 mM, 12.25 mM, and 25 mM. The hydrogel and 3D-printed cornea were comprehensively evaluated for chemical structure, surface functional groups, water content, mechanical strength, orientation, cytotoxicity, biocompatibility, and transparency. Notably, the inclusion of PG significantly enhanced the mechanical properties of the 3D-printed cornea, with the hydrogel achieving a storage modulus of 2,360 kPa at 6.25 mM of PG/CC, while maintaining over 95% water content. The artificial cornea demonstrated 86% transparency, and the cell viability showed 96% viable on Day 7 with degradation rate of 35.9% in 28 days. The superior hydrophilicity, transparency, and mechanical strength of the printed hydrogel highlights its potential for the development of full-thickness corneal structures, making it a promising candidate for future corneal implants.

Enhancing refrigerated chicken breasts preservation: Novel composite hydrogels incorporated with antimicrobial peptides, bacterial cellulose, and polyvinyl alcohol

Microbial contamination annually leads to substantial food resource loss. Effective food packaging can mitigate food contamination and waste, yet conventional materials such as plastics often lack bacteriostatic activity. This study aimed to synthesise FengycinA-M3@bacterial cellulose@polyvinyl alcohol composite hydrogels via dual cross-linking with hydrogen and borate bonding, with the goal of enhancing antibacterial properties and prolonging the preservation period of refrigerated chicken breast. The composite hydrogel was subjected to comprehensive characterisation for structural, mechanical, water absorption, slow peptide release, antimicrobial capacity, biocompatibility, and chicken breast freshness preservation. The results showed that the composite hydrogel had a porous network structure and excellent gel elasticity and biocompatibility. It was effective in inhibiting Staphylococcus aureus and Escherichia coli, and prolonged the storage time of frozen chicken breast for up to 12 days. These findings emphasise the potential of hydrogel food packaging to prolong storage periods and its suitability for food industry applications due to ease of manufacture.

Comparative evaluation of adsorptive and repulsive separation using cellulose nanofiber/calcium alginate composite hydrogel filtration membranes with improved degradability

Among several approaches to address hard-to-manage dye wastewater, adsorption is one of the widely used methods, but the usage of these adsorbents can be constrained by their high material and process costs depending on the adsorbent materials as well as handling a large amount of adsorbents in a bulk solution. To overcome the problems, hydrogel membranes have recently attracted much attention because they can provide several strengths such as adsorption removal, confined adsorption sites, and filtration separation. However, to the best of our knowledge, it is still quite rare to find an in-depth comparative evaluation of adsorptive removal and repulsive separation in hydrogel membrane filtration. Herein, this study aims to bridge the gap between existing knowledge and undisclosed phenomena. Through a thorough comparative evaluation of adsorptive removal and repulsive separation in hydrogel membrane filtration, we found that repulsive separation was more suitable and sustainable than adsorptive removal because it was free from internal membrane fouling, adsorption sites’ saturation, and the cake layer formation on the surface. As a result, the hydrogel membranes could maintain excellent real-time separation performance while mitigating severe flux and rejection decline. Furthermore, we significantly improved the degradability of the spent hydrogel membrane under high saline conditions by 6.3 times compared to the control membrane by fine-tuning the structural properties via dual crosslinking, while maintaining the mechanical properties during filtration. It was possible due to the extended distance between polymer chains by dual crosslinking, reducing the burden imposed by plastic waste generated from the spent membrane.

Chitosan-based composite featuring dual cross-linking networks for the removal of aqueous Cr(VI)

To avoid the environmental detriment caused by Cr(VI) waste, this study constructs a dual cross-linking network structure using sodium alginate (SA) and polyvinyl alcohol (PVA). Chitosan (CS) is further introduced through electrostatic attraction and hydrogen bonding and SA/PVA/CS (SPC) composite with porous structure is successfully prepared for the removal of Cr(VI) from wastewater. Batch adsorption experiments show that SPC has excellent adsorption capacity and practical usability with a broad pH applicability range. Under optimal adsorption conditions (pH = 2, t = 150 min, T = 35 °C, m/V = 2 g/L, C0 = 10 mg/L), the Cr(VI) removal rate of SPC achieves 89.2 %. Adsorption kinetics and isotherm models indicate that the adsorption process is primarily multi-layer and chemical adsorption. Additionally, FT-IR and XPS reveal that the adsorption mechanism of SPC for Cr(VI) involves a synergy of electrostatic attraction, reduction, ion exchange and complexation. Density functional theory (DFT) simulations also confirm the dominant role of CS in the Cr(VI) adsorption. In summary, SPC shows great potential for Cr(VI) wastewater treatment.

Mechanical and Biological Characterization of Ionic and Photo-Crosslinking Effects on Gelatin-Based Hydrogel for Cartilage Tissue Engineering Applications.

Articular cartilage degeneration poses a significant public health challenge; techniques such as 3D bioprinting are being explored for its regeneration in vitro. Gelatin-based hydrogels represent one of the most promising biopolymers used in cartilage tissue engineering, especially for its collagen composition and tunable mechanical properties. However, there are no standard protocols that define process parameters such as the crosslinking method to apply. To this aim, a reproducible study was conducted for exploring the influence of different crosslinking methods on 3D bioprinted gelatin structures. This study assessed mechanical properties and cell viability in relation to various crosslinking techniques, revealing promising results particularly for dual (photo + ionic) crosslinking methods, which achieved high cell viability and tunable stiffness. These findings offer new insights into the effects of crosslinking methods on 3D bioprinted gelatin for cartilage applications. For example, ionic and photo-crosslinking methods provide softer materials, with photo-crosslinking supporting cell stretching and diffusion, while ionic crosslinking preserves a spherical stem cell morphology. On the other hand, dual crosslinking provides a stiffer, optimized solution for creating stable cartilage-like constructs. The results of this study offer a new perspective on the standardization of gelatin for cartilage bioprinting, bridging the gap between research and clinical applications.

Dual effect of pH and X-ray irradiation on properties of gelatin/trans-cinnamaldehyde-based composite films for sustainable packaging

Gelatin (Gel) based water-insoluble films with antimicrobial properties were developed by the green method using trans-cinnamaldehyde (TCA) and low-energy X-ray irradiation as dual crosslinkers. The Gel/TCA composite films (GTCF) were prepared at different pH (4, 6, 8, and 10) and crosslinked by incorporating 5 % (w/w, based on Gel) TCA and X-ray irradiation (350 kV and 11.4 mA) with doses of 0, 5, 10 and 15 kGy. The presence of TCA in GTCF forms dense, flexible, and strong films when exposed to X-ray irradiation. The GTCF at pH 6, incorporated with 5 wt% TCA and irradiated with 10 kGy X-ray, displayed the highest degree of crosslinking (DOC) (93.4 ± 3.4 %), tensile strength, excellent UV-barrier (> 99.9 %), antimicrobial (inhibitory capacity of >50 %), and water vapor permeability (4.1 ± 0.6 g.mm/m2.day. kPa), and low solubility in water (0.5 ± 0.3 %), and oxygen permeability. The GTCF, crosslinked with X-ray irradiation, has multifunctional properties and strong potential in the sustainable packaging industry to augment the shelf life of food and reduce food waste. To the best of our information, this is the first and novel report investigating the effects of pH on the properties of GTCF crosslinked with X-ray.

Hierarchical H-bonding and metal coordination bonds enabled supramolecular dual networks for high-performance energy-dissipation

Natural organisms have superior material properties such as mechanical adaptability, impact protection, and self-healing to protect the body from complicated external environments, fascinating the development of functional supramolecular elastic materials with biomimetic protective features. Herein, a dual physically crosslinked supramolecular polyurethane (PU) network with strain-hardening effect is synthesized by incorporating hierarchical hydrogen bonds (H-bond) and metal coordination bonds into an elastomer matrix. A moderate content of quadruple H-bonds is critical for achieving a prominent toughness and a considerable strain-at-break owing to the strain hardening effect enabled by the hierarchical H-bonds. When the Zn-to-pyridine coordination bonds were introduced to the supramolecular PU, the strength, toughness, and energy dissipation properties were further enhanced attributing to the dual physical crosslinking networks. The dynamic dissociation and association of the sacrificial H-bonds and Zn-to-pyridine coordination bonds induced significant strain hardening effect and enabled tremendous energy absorption and self-healing properties. Besides, the supramolecular PU elastomers and their blends were foamed via scCO2 foaming to produce supramolecular foams containing dynamic bonds. The composite foam could effectively reduce the impact force from 6085 N to 373 N and achieve an outstanding energy absorption efficiency of 93.87% owing to the synergistic effect of porous structure and dual physically crosslinked networks. This work provides an innovative strategy for designing high-performance energy absorbing supramolecular elastomers and cushioning foams with reversible bonds.

Building covalent crosslinks of carboxymethyl konjac glucomannan with boronic ester bonds for fabricating multimodal hydrogel sensor

As the derivative of konjac glucomannan (KGM), carboxymethyl konjac glucomannan (CMK) has attracted increasing attention in the polysaccharide hydrogel fields with the aim of improving the performance related to drug delivery and release. In this study, we prepared a CMK-based hydrogel with dual characteristic crosslinks, and unlocked new applications of this type of hydrogel in soft sensor fields. CMK and poly (vinyl alcohol) were used as substrates, and physical crosslinks were constructed via the freeze-thawing treatments and covalent crosslinks were built via the boronic ester bonding. As-prepared hydrogel possessed significantly improved mechanical performance because the boronic ester bonding, on the one hand, well associated the two kinds of polymer chains, and on the other hand, played the role of ‘sacrificial crosslinks’. Furthermore, the occurrence of dynamic boronic ester bonding gave the hydrogel strain- and temperature-sensitive ionic conductivity, and therefore, the hydrogels could be used to identify human motions and as-resulted environmental temperature alterations, and worked well in various scenarios. This work activates new application of CMK in the multimodal sensing field, and also proposes an intriguing way of building multiple crosslinks in the KGM derivative-based hydrogels.

Long-lasting anti-corrosion direct-to-metal polyurethane NP-GLIDE coatings based on the coordination effect and dual cross-linking of polyphenol

Aluminum and its alloys have been widely used in our lives. However, Aluminum and its alloys is prone to corrosion, especially in harsh environment. In recent years, hydrophobic coatings were used in the corrosion protection of metal. But, the low surface tension of resins made them have a worse wettability on metal which had high surface tension, resulting in a worse adhesion of these coatings. Herein, we developed a long-lasting anti-corrosion direct-to-metal polyurethane NP-Glide coating based on the coordination effect of polyphenol and dual cross-linking. In comparative evaluation, the corrosion protection and anti-contamination performances of direct-to-metal polyurethane NP-Glide coating are significantly improved by the introduction of functional monomer dopamine methacrylamide (DMA) and TEMAc-8. The PU coatings with 10 wt% TEMAc-8 possesses high impedance value (|Z|0.01Hz > 109 Ω•cm2) after 40 days of immersion in 3.5 wt% NaCl solution, exhibiting a great pull-off adhesion both in dry and wet coating, and a long-term anti-corrosion performance for aluminum alloy protection.

Fabrication of dual dynamic crosslinking polyurethane networks towards self-healing, resist fatigue, and highly stretchable ionic skins

The limited anti-fatigue performance of self-healing polyurethane elastomers under high-strain conditions restricts their application in high-performance ionic skins. Herein, a polyurethane network (PU-DDN) synergistically reversibly crosslinked by dynamic thiourethane bonds and hydrogen bonds was synthesized successfully. This dual reversibly crosslinking strategy not only endowed the polyurethane network with an excellent fatigue resistance (showing a residual strain of only 63 % after 10 uninterrupted cyclic tensile tests at 400 % strains), but also imparted it with a high strength (6.12 MPa) and stretchability (611.42 %). Owing to the thermo-reversibility of dual dynamic networks, the damaged PU-DDN heated at 100 °C for 3h could fully restore its initial mechanical properties. Subsequently, transparent stretchable ionic skins were fabricated by mixing the PU-DDN with ionic liquids. A resulting highly-sensitive ionic skin (GF1 = 1.25, GF2 = 2.01) named PU-DDN/IL20 demonstrated exceptional durability, which could produce repeatable electrical signals even after 2000 cycles of stretching to an extensive deformation of 400 %. Meanwhile, it can also monitor human motions, showcasing its promising potential in the realm of intelligent wearable applications.

A dual crosslinking strategy to tailor rheological properties of gelatin methacryloyl

3D bioprinting is an emerging technology that enables the fabrication of three-dimensional organised cellular constructs. One of the major challenges in 3D bioprinting is to develop a material to meet the harsh requirements (cell-compatibility, printability, structural stability post-printing and bio-functionality to regulate cell behaviours) suitable for printing. Gelatin methacryloyl (GelMA) has recently emerged as an attractive biomaterial in tissue engineering because it satisfies the requirements of bio-functionality and mechanical tunability. However, poor rheological property such as low viscosity at body temperature inhibits its application in 3D bioprinting. In this work, an enzymatic crosslinking method triggered by Ca2+-independent microbial transglutaminase (MTGase) was introduced to catalyse isopeptide bonds formation between chains of GelMA, which could improve its rheological behaviours, specifically its viscosity. By combining enzymatic crosslinking and photo crosslinking, it is possible to tune the solution viscosity and quickly stabilize the gelatin macromolecules at the same time. The results showed that the enzymatic crosslinking can increase the solution viscosity. Subsequent photo crosslinking could aid in fast stabilization of the structure and make handling easy.

Dual thermally crosslinked hollow fiber membranes for plasticization-resistant helium recovery from natural gas

Membrane-based helium recovery from natural gas faces a major challenge due to membrane plasticization, which increases permeances but reduces selectivities. Thermal crosslinking has emerged as a promising approach to enhance the plasticization resistance of membranes by restricting segmental mobility and creating well-defined microporosity for gas separation. Herein, we develop novel dual thermally crosslinked asymmetric hollow fiber membranes (HFMs) using a 4,4′-diamino-2,2′-biphenyldicarboxylic acid-containing copolyimide. Decarboxylation-based dual crosslinking is achieved through heat treatment at various temperatures, resulting in the generation of C–C covalent bonds. The interchain distance increases from 5.33 to 5.76 Å, and the hierarchical pore size distributions exhibit ultra-micropore size between 5.6 and 6.8 Å as well as micropore size between 7.0 and 9.5 Å. Notably, the formation of stable C–C covalent bonds through dual crosslinking and the existence of bulky −CF3 groups in the 2,2′-bis(trifluoromethyl)-4,4′-biphenyldiamine moiety prevent substructure collapse by enhancing the chain rigidity and rotational barrier. Gas transport properties of the crosslinked HFMs are effectively tuned by adjusting the heat treatment temperatures. Particularly, the PI-TFMB-HF@400 membrane exhibits a He permeance of 25 GPU and He/CH4 selectivity of 269. Additionally, the crosslinked HFMs exhibit enhanced plasticization resistance. The PI-TFMB-HF@400 membrane, for instance, shows only a 24 % decrease in mixed-gas CO2/CH4 selectivity and an 80 % increase in mixed-gas [He/(CO2 + CH4)] selectivity when exposed to a high-pressure (40 bar) ternary mixed-gas feed of He/CO2/CH4 (0.3/49.7/50, v/v/v), and the mixed-gas [He/(CO2 + CH4)] selectivity increases with temperature. The dual thermally crosslinked HFMs in this study demonstrate the potential for helium recovery from aggressive natural gas.

Study the effect of different concentrations of polydopamine as a secure and bioactive crosslinker on dual crosslinking of oxidized alginate and gelatin wound dressings

Alginate hydrogels are commonly used in wound care due to their ability to maintain a moist environment, absorb fluids, and aid wound healing. However, their stability and mechanical properties can sometimes limit their effectiveness. This study explores a new approach by creating a dual network system of oxidized alginate and gelatin hydrogel crosslinked with polydopamine in a single step, with the goal of improving the mechanical properties of these hydrogels. The unique aspect of this research is the comprehensive examination of different polydopamine concentrations in dual crosslinking systems. First, alginate was modified with sodium periodate to create additional active groups on its backbone, and various polydopamine concentrations were then tested to assess their impact on the dual crosslinking network and hydrogel properties. The study involved a range of tests, including FTIR, H-NMR, SEM, gelation time, rheology, adhesion, antioxidant activity, swelling ratio, weight loss, drug release, and cell viability. The addition of polydopamine was found to enhance the crosslinking density (0.859 × 109 mol.cm−3). Additionally, the results indicated improvements in properties such as reduced weight loss, enhanced antioxidant and adhesive qualities, and better mechanical properties (2240 kPa). However, the optimal concentration of polydopamine must be determined to achieve the best properties for a wound dressing. Excessive polydopamine can increase the space between polymer chains, leading to a reduction in crosslinking density and storage modulus. Nevertheless, it can also increase the swelling ratio, degradation rate, pore size, porosity, antioxidant activity, and dopamine release. Therefore, identifying the optimal concentration for a functional hydrogel is crucial. Notably, the hydrogel containing 0.5 mg.mL−1 polydopamine exhibited outstanding cell viability (108 % on the third day), swelling capacity (480 %), storage modulus (2240 kPa), gelation time (3 min), antioxidant activity (42.27 %), and skin adherence (11 kPa), making it an optimal choice for advanced wound management. According to the findings, it is emphasized that the application of this particular hydrogel expedites wound healing, as indicated by wound closure and histological studies. AbbreviationsUnlabelled TableOALoxidized alginateGELgelatinPDApolydopamineEDCsodium meta periodate 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochlorideNHSN-hydroxysuccinimide

Enhancing the mechanical properties of self‐healing polyurethane via chemical crosslinking

AbstractSelf‐healing research based on commercial polymeric materials (such as polyurethane) is beneficial to sustainable development by prolonging the life of materials. However, developing polymeric materials that integrate robust mechanical properties with self‐healing ability at ambient temperature remains a formidable challenge. The formation of polymeric materials by physically and chemically dual crosslinking structures is a powerful method to improve mechanical properties. Herein, a series of dual crosslinking self‐healing polyurethane have been designed and successfully synthesized by incorporating 2‐ureido‐4[1H]‐pyrimidinone (UPy) units and triethanolamine (TEOA) into the polymer networks. Relying on the reinforcement of chemical crosslinking which is induced by TEOA, the resulting polyurethane exhibited robust strength of 10.3 MPa and elongation at break of 569.4%, which are quite prominent compared with previous reports. At the same time, the recombination of hydrogen bonds makes the polyurethane with UPy structure achieve rapid self‐healing after 24 h at 40°C and the strength recovered to 4.98 MPa. This work provided a novel way to fabricate sustainable polyurethane with robust mechanical properties.

A dual cross-linking strategy enables fully bio-based epoxy thermosets with superior low dielectric properties and mechanical properties

Bio-based epoxy resins with superior low dielectric properties and mechanical properties is of great significance for sustainable development and environmental protection. Herein, a bio-based active ester curing agent with large free volume was synthesized through a substitution reaction between magnolol and cinnamoyl chloride following by curing epoxidized linseed oil for fully bio-based epoxy thermosets. The curing kinetics of the curing behavior and the curing condition was systematic studied and optimized. The relationship between chemical structure and properties (thermo-mechanical, mechanical, dielectric, and etc.) of the resulting fully bio-based epoxy thermosets was discussed in-depth. The results showed that free radical polymerization and epoxy ring-opening reactions simultaneously occurred in the curing reaction led to a dual cross-linked structure of the resulting fully bio-based epoxy thermosets. The unique structures and the introduction of the rigid benzene groups rendered the tensile strength and the thermal stability of the resulting fully bio-based epoxy thermosets high up to 33.63 MPa and 332.40 °C, respectively. The absence of the secondary hydroxyl groups and the presence of the low polar fatty acid chains in the backbone of the epoxy resins resulted in the dielectric constant and dielectric loss low to 3.19 and 0.012, which was much lower than those of the polymer previously reported. This study provides a simple and facile strategy for the design of environmentally friendly fully bio-based epoxy resins for microelectronics and electronic packaging application.

Dual cross-linking mechanism of sodium alginate composite hydrogel for adhesive microneedle patch preparation

The introduction of microneedles has revolutionized transdermal drug delivery. However, solid microneedle patches often fail to conform to the epidermis and adapt to changes in skin curvature, limiting their effectiveness. Using sodium alginate hydrogel to create flexible microneedle patches can address this issue, but conventional sodium alginate hydrogels suffer from inhomogeneous structure, dehydration, and poor mechanical properties. These drawbacks result in reduced drug delivery efficacy and insufficient mechanical robustness. To enhance the performance of sodium alginate hydrogels, this study presents a novel sodium alginate composite hydrogel with a dual cross-linking mechanism. The hydrogel, with a gelatin to sodium alginate ratio of 1:1, exhibited optimal surface morphology and mechanical properties suitable for microneedle patch preparation. The resulting microneedle patch demonstrated excellent water adhesion, securely attaching to skin and oral mucosa surfaces. In vitro experiments confirmed the microneedle's ability to puncture and release the drug, dissolving and releasing the drug within 15 minutes. The patch also showed superior piercing and dissolution properties on the mouth palate, highlighting it may serve as a potential delivery location for more efficient microneedle patch drug administration. In the future, this technology will show great potential in expanding the scope of drug administration for transdermal drug delivery and in reducing the work pressure of healthcare professionals.

Dually-crosslinked ionic conductive hydrogels reinforced through biopolymer gellan gum for flexible sensors to monitor human activities

Human-machine interactions, monitoring of health equipment, and gentle robots all depend considerably on flexible strain sensors. However, making strain sensors have better mechanical behavior and an extensive sensing range remains an urgent difficulty. In this study, poly acrylamide-co-butyl acrylate with gellan gum (poly(AAm-co-BA)@GG) hydrophobic association networks and intermolecular hydrogen bonding interactions are used to fabricate dual cross-linked hydrogels for wearable resistive-type strain sensors. This could be an acceptable way to minimize the limitations in hydrogels previously identified. The robust fracture strength (870 kPa) and exceptional stretchability (1297 %) of the hydrogel arise from the collaborative action of intermolecular hydrogen bonding and hydrophobic associations. It also demonstrates exceptional resilience to repeated cycles of uninterrupted stretching and relaxation, retaining its structural integrity. The response and restoration times are 110 and 120 ms respectively. Furthermore, a wide sensing range (0–900 %), notable sensitivity across various strain levels, and an impressive gauge factor (GF) of 31.51 with high durability were observed by the dual cross-linked (DC) hydrogel-based strain sensors. The measured conductivity of the hydrogel was 0.32 S/m which is due to the incorporation of NaCl. Therefore, the hydrogels can be tailored to function as wearable strain sensors that can detect subtle human gestures like speech patterns, distinguish between distinct words, and recognize vibrations of the larynx during drinking, as well as large joint motions like wrist, finger, and elbow. Furthermore, these hydrogels are capable of reliably distinguishing and reproducing various printed text. These findings imply that any electronic device that demands strain-sensing functionality might make use of these developed materials.