Characterization and swelling–deswelling properties of wheat straw cellulose based semi-IPNs hydrogel

Anti-freezing, long-term-usability conductive organo-hydrogels containing lignin for the manufacture of high-performance flexible strain and temperature sensors

The development of an all-in-one hydrogel that possesses the desired characteristics of multiple sensing modalities, exceptional electrical conductivity, and high strain sensing performance remains a significant challenge. Here, we employed calcium ions to crosslink and chelate sodium alginate and sodium lignosulfonate within a polyacrylic acid hydrogel network. Additionally, we introduced a conductive polyaniline network through in situ polymerization and performed a solvent exchange with glycerol to produce a multifunctional conductive organo-hydrogel. The resulting hydrogels exhibited remarkable mechanical properties, with a strength of 268 kPa at a tensile strain of 400 %. They also demonstrated resistance to drying and freezing, remaining unfrozen at low temperatures of -60 °C, as well as temperature sensitivity. The incorporation of polyaniline and Ca2+ ions contributed to enhanced electrical conductivity and sensing capabilities, evidenced by gauge factors of 1.39 and 2.13 in the strain ranges of 0-210 % and 210-400 %, respectively. Furthermore, the temperature sensing properties were characterized by a temperature coefficient of resistance of -4.49 % °C-1 and -0.92 % °C-1 in the temperature ranges of -25 to 25 °C and 25 to 60 °C, respectively. Leveraging these advantageous properties, this hydrogel is anticipated to serve as a real-time motion detection device for human activities in extreme conditions.

Counter-intuitive discovery in the formulation of poorly water-soluble drugs: Amorphous small-molecule gels

Amorphous strategies have been extensively used in improving the dissolution of insoluble drugs for decades due to their high free energy. However, the formation of amorphous small-molecule gels (ASMGs) presents a counter-intuitive discovery that significantly limits their practical application. Recently, ASMGs have garnered attention because of their noncovalent structures, excellent biodegradability, and significant potential in various drug delivery systems in the pharmaceutical field. Hence, a comprehensive review is necessary to contribute to a better understanding of recent advances in ASMGs. This review aimed to introduce the main formation mechanisms, summarize possible influencing factors, generalize unique properties, outline elimination strategies, and discuss clinical application potential with preclinical cases of ASMGs. Moreover, few ASMGs are advanced to clinical stages. Intensive clinical research is needed for further development. We hope that this review can provide more efficient and rational guidance for exploring further clinical applications of ASMGs.

Study on the structure characterization and swelling properties of the Fe3O4/CMS composite membrane

In order to improve the functionality of cellulosic materials research and development of high performance soluble materials. Therefore, the Fe3O4/CMS composite membrane was prepared by using carboxymethyl salix powder (CMS) and Fe3O4 as raw materials, 1-propenyl-3-methylimidazolium chloride and dimethyl sulfoxide as dissolution system. The effects of swelling time, swelling temperature, pH and ionic strength on the swelling performance of Fe3O4/CMS composite membranes and the swelling kinetics of the composite membranes were studied. The structure of the composite membrane was characterized by SEM, FT-IR, XRD and TG. The results showed that the swelling degree reached 5.54 g·g-1, when the swelling time was 45 min, the swelling temperature was 65°C, the pH was 5 and the ionic strength was 0.08 mol·L-1. The initial phase of dissolution of the composite membrane fits well with the Fickian diffusion model, and the whole dissolution process belongs to the Schott model, indicating that the main role of the dissolution process is the diffusion of water molecules, while the composite membrane can be preserved for a long time at high temperature, which provides sustainability for the composite membrane. The characterization results showed that the surface of Fe3O4/CMS composite film was rough with small grooves. The O-H effect was enhanced and the Fe-O absorption peak appeared at 600 cm-1, indicating that Fe3O4 had been successfully loaded onto the cellulose membrane. The Fe3O4/CMS composite membrane belonged to cellulose type II structure, meanwhile, the composite membrane had good thermal stability.

Development and characterization of pH-responsive Delonix regia/mucin co-poly (acrylate) hydrogel for controlled drug delivery of metformin HCl

This study introduces a pH-responsive hydrogel developed from Delonix regia and mucin co-poly(acrylate) through free radical polymerization to enhance controlled drug delivery systems. Characterization using FTIR, DSC, TGA, SEM, PXRD, and EDX spectroscopy detailed the hydrogel's amorphous and crystalline structures, thermal stability, surface characteristics, and elemental composition. Tested at a pH of 7.4-mimicking intestinal conditions-the hydrogel demonstrated significant swelling, indicating its capability for targeted drug release. With Metformin HCl as a model drug, the hydrogel exhibited a promising sustained release profile, underscoring its potential for oral administration. Safety and biocompatibility were assessed through acute oral toxicity studies in albino rabbits, encompassing biochemical, hematological, and histopathological evaluations. X-ray imaging confirmed the hydrogel's navigability through the gastrointestinal tract, affirming its application in drug delivery. By potentially mitigating gastrointestinal side effects, enhancing patient compliance, and improving therapeutic efficacy, this Delonix regia/mucin co-poly(acrylate) hydrogel represents a step in pharmaceutical sciences, exploring innovative materials and methodologies for drug delivery.

Preparation and characterization of ternary polysaccharide hydrogels based on carboxymethyl cellulose, carboxymethyl chitosan, and carboxymethyl β-cyclodextrin

A series of ternary polysaccharide hydrogels were facile prepared by incorporating carboxymethyl cellulose (CMC) into the carboxymethyl chitosan/carboxymethyl β-cyclodextrin (CMCS/CMCD) complex solution based on multiple physical interactions. Structure properties of the CMC/CMCS/CMCD hydrogels were revealed by FTIR, XRD, SEM, and TG. The rheological and texture properties, temperature/pH-response behaviors, biocompatablity, and antimicrobial activity of the hydrogels were determined in detail. These results showed that the existence of electron force and hydrogen bond among three components leading to formation of the hydrogels, displaying good mechanical characteristic, stable solid-like rheological properties, controllable swelling and degradation behaviors, and excellent biocompatibility. Additionally, the swelling kinetics can be well described by the Schott's pseudo second order model. Moreover, the hydrogels loaded with cinnamic acid (CA) exhibited good antimicrobial activity against both Staphylococcus aureus and Escherichia coli, and the antimicrobial activity was related to the composition of the prepared hydrogels. The novel ternary polysaccharide hydrogels may have good application prospects in food and bio-medicine.

Gel properties and interactions of hydrogels constructed with low acyl gellan gum and puerarin

To develop composite hydrogels based on low acyl gellan gum (GG), the effect of puerarin (PUE) on the gel properties of GG was investigated. The results showed that the maximum storage modulus (G') of the 1.2 % GG/0.8 % PUE composite hydrogel was 377.4 Pa at 0.1 Hz, which was enhanced by 4.7-fold compared with that of 1.2 % GG. The melting temperature of this composite hydrogel increased from 74.1 °C to >80.0 °C. LF-NMR results showed that a significant amount of free water was present in the hydrogel matrix. The surface structure aggregation and the shrinkage of the honeycomb meshes in the composite hydrogel proved the cross-linking of PUE and GG. XRD, FTIR and molecular simulation results illustrated that hydrogen bonds were the most important factor controlling the interaction between GG and PUE. Thus, the GG/PUE composite hydrogel has good elasticity, thermal stability and water retention, which lays a good foundation for further application in the food industry.

Improving the Physical Properties of Starch-Based Powders for Potential Anti-Adhesion Applications

Postoperative adhesion is one of the most common complications that occur during and after surgery; thus, materials that can prevent adhesion are often applied. Starch powders with a high water absorption capacity are preferred, and many studies have focused on increasing the water absorption of modified starches, as native starch powders display poor water-holding capacities. The effects of salts on the physical properties of acetylated distarch phosphate potato starch powders were investigated here. Changes in functional groups, the crystal structures of modified starch, particle morphologies, water absorption, viscosity, and in vivo adhesion were investigated. The results showed that salts greatly improved the water absorption and viscosity of acetylated distarch phosphate potato starch powders. Among the three different salt-modified starch powders, NaCl-modified starch powders displayed higher water absorption and viscosity and demonstrated better in vivo anti-adhesion performance. The results of this study propose a potential biomaterial that may function as an anti-adhesive, potentially leading to reduced surgical risks and a better quality of life for patients.

A Comprehensive Review of Polysaccharide-Based Hydrogels as Promising Biomaterials

Polysaccharides have emerged as a promising material for hydrogel preparation due to their biocompatibility, biodegradability, and low cost. This review focuses on polysaccharide-based hydrogels' synthesis, characterization, and applications. The various synthetic methods used to prepare polysaccharide-based hydrogels are discussed. The characterization techniques are also highlighted to evaluate the physical and chemical properties of polysaccharide-based hydrogels. Finally, the applications of SAPs in various fields are discussed, along with their potential benefits and limitations. Due to environmental concerns, this review shows a growing interest in developing bio-sourced hydrogels made from natural materials such as polysaccharides. SAPs have many beneficial properties, including good mechanical and morphological properties, thermal stability, biocompatibility, biodegradability, non-toxicity, abundance, economic viability, and good swelling ability. However, some challenges remain to be overcome, such as limiting the formulation complexity of some SAPs and establishing a general protocol for calculating their water absorption and retention capacity. Furthermore, the development of SAPs requires a multidisciplinary approach and research should focus on improving their synthesis, modification, and characterization as well as exploring their potential applications. Biocompatibility, biodegradation, and the regulatory approval pathway of SAPs should be carefully evaluated to ensure their safety and efficacy.

Cationic Modified PVA Hydrogels Provide Low Friction and Excellent Mechanical Properties for Potential Cartilage and Orthopedic Applications

Poly(vinyl alcohol) (PVA) hydrogel is a promising candidate for articular cartilage repair yet restrained by its mechanical strength and tribological property. Current work reports a newly designed PVA-based hydrogel modified by glycerol (g), bacterial cellulose (BC), and a cationic polymer poly (diallyl dimethylammonium chloride) (PDMDAAC), which is a novel cationic strengthening choice. The resultant PVA-g-BC-PDMDAAC hydrogel proves the effectiveness of this modification scheme, with a confined compressive modulus of 19.56 MPa and a friction coefficient of 0.057 at a joint-equivalent load and low sliding speed. The water content, swelling property, and creep behavior of this hydrogel are also within a cartilage-mimetic range. The properties of PVA-based hydrogels before PDMDAAC addition are likewise studied as a cross-reference. Besides, PDMDAAC-modified PVA hydrogel realizes ideal mechanical and lubrication properties with a relatively low PVA concentration (10 wt.%) and facile fabrication process, which lays a foundation for mass production and marketization in the future.

Nanocomposite conductive tough hydrogel based on metal coordination reinforced covalent Pluronic F-127 micelle network for human motion sensing

The design of conductive hydrogels integrating anti-fatigue, high sensitivity, strong mechanical property and good sterilization performance remains a challenge. We innovatively introduced metal coordination in covalently crosslinked Pluronic F-127 micelle network and synthesized nanocomposite conductive tough hydrogel through the combination of covalent crosslinking, metal coordination and silver nanowire reinforcement. Compared with pure diacylated PF127 hydrogel (PF127), the tensile strength of PF-AA-AM-Al³⁺/Ag0.25 hydrogel reaching 1.4 MPa was about 10 times than that of PF127. The toughness of PF-AA-AM-Al³⁺/Ag0.25 reaches 1.88 MJ/m³. Compared with PF-AA-AM-Al³⁺, the introduction of silver nanowires increased the fatigue life of PF-AA-AM-Al³⁺/Ag0.25 by 200% (31837 cycles), 170% (12804 cycles) and 1022% (511 cycles) under 100%, 120% and 150% ultimate tensile strains, respectively. Besides, the PF-AA-AM-Al³⁺/Ag0.25 showed strain sensitivity to small deformation (Gauge factor = 2.42) in wearable tests on hands and knees. In addition, the PF-AA-AM-Al³⁺/Ag0.25 had good cytocompatibility and antibacterial performance that bacteria killing ratio of 98% to S. aureus and 99% to E. coli. Finally, a viscoelastic numerical constitutive model was established based on finite element method to study the damage failure history of the material. Comparative analysis showed that local stress concentration was the main factor leading to the failure of hydrogel.

Combined Strategy of Wound Healing Using Thermo-Sensitive PNIPAAm Hydrogel and CS/PVA Membranes: Development and In-Vivo Evaluation

Past studies have shown that the hot spring effect can promote wound healing. Mild thermal stimulation and metal ions can promote angiogenesis. In this study, the hot spring effect was simulated by thermosensitive PNIPAAm hydrogel loaded with copper sulfide nanoparticles. Heat stimulation could be generated through near-infrared irradiation, and copper ions solution could be pulsed. On the other hand, the CS/PVA nanofiber membrane was attached to the bottom of the hydrogel to simulate the extracellular matrix structure, thus improving the wound healing ability. The CS/PVA nanofiber membrane was prepared by electrospinning, and the appropriate prescription and process parameters were determined. The nanofiber membrane has uniform pore size, good water absorption and permeability. The poor mechanical properties of PNIPAAm hydrogel were improved by adding inorganic clay. The temperature of the hydrogel loaded with CuS nanoparticles reached 40 °C under near-infrared light irradiation for 20 min, and the release rate of Cu²⁺ reached 26.89%. The wound-healing rate of the rats in the combined application group reached 79.17% at 13 days, demonstrating superior results over the other control groups. Histological analyses show improved inflammatory response at the healed wound area. These results indicate that this combined application approach represents a promising wound treatment strategy.

Preparation of a low-cost and eco-friendly superabsorbent composite based on wheat bran and laterite for potential application in Chinese herbal medicine growth

A low-cost and eco-friendly superabsorbent composite is prepared through the free-radical graft co-polymerization of wheat bran (WB), acrylic acid (AA) and laterite (LA) in an aqueous solution. Elemental map, scanning electron microscopy and Fourier transform infrared spectra revealed that the LA evenly distributed in the superabsorbent composite and wheat bran-g-poly(acrylic acid)/laterite (WB-g-PAA/LA) formed successfully. Thermogravimetric analysis confirmed that the WB-g-PAA/LA had high thermal stability. Furthermore, the properties of the WB-g-PAA/LA, such as swelling in saline solutions and degradation, are also assessed. The final WB-g-PAA/LA (5 wt%) superabsorbent composite attained an optimum water absorbency of 1425 g g^-1 in distilled water and 72 g g^-1 in 0.9 wt% NaCl solution. The water absorbency of WB-g-PAA/LA (10 wt%) is even greater than that of the WB-g-PAA. Moreover, the water-retention capacity of WB-g-PAA/LA (5 wt%) is high, and the water-retention process followed a zero-order reaction. The reaction rate constant is 8.2428 × 10⁵ exp(-E_a/RT) and the apparent activation energy (E_a) is 35.11 kJ mol^-1. Furthermore, WB-g-PAA/LA (5 wt%) may regulate the release of urea, indicating that the superabsorbent composite could provide a promising application as a urea fertilizer carrier. Additionally, it increased the germination and growth rates of Glycyrrhiza uralensis Fisch, suggesting it could influence the growth of Chinese herbal medicine.

Stimuli-Responsive Hydrogels Based on Polyglycerol Crosslinked with Citric and Fatty Acids

Polyglycerol-based hydrogels from biodegradable raw materials were synthesized by crosslinking reactions of polyglycerol with citric and fatty acids. Three hydrogels were studied varying molar ratios of crosslinking agent. It was found that crosslink amount, type, and size play a crucial role in swelling, thermal, mechanical, and stimuli-responsive properties. The hydrogels absorption capacity changed in response to temperature and pH external stimuli. The hydrogel with the highest swelling capacity absorbed more than 7 times its own weight at room temperature and pH 5. This material increased 14 times its own weight at pH 10. Creep-recovery tests were performed to study the effect of crosslinking agent on mechanical properties. Deformation and percentage of recovery of synthesized hydrogels were obtained. Formation of hydrogels was confirmed using FTIR, and physicochemical properties were analyzed by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetric (DSC), and Dynamic Mechanical Analysis (DMA). This paper aims to give a contribution to biobased hydrogel knowledge from chemical, physicochemical, and mechanical point of view.

Self-powered hydrogels induced by ion transport

Electroactive hydrogels are needed to enable stretchable electronics because of their flexible mechanical characteristics and electrical conductive properties. We describe a class of viscoelastic, porous, ion-conductive, and self-powered hydrogels that are fabricated based on a PHEMA hydrogel (poly(2-hydroxyethyl methacrylate)) and PPy (polypyrrole). They are capable of creating synchronous ionic current in electrolyte solution when enduring mechanical deformation. The conditions that impact the electric response of the hydrogel, such as stress, strain rate, pH of electrolyte solution, and concentration of ions in the electrolyte solution, have been investigated and reported in this paper. The mechanism of creating ionic current under deformation is elaborated through numerical simulation and experimental tests. Moreover, by embedding the electrically self-powered hydrogel into a movable object, such as a sports shoe, the patterns of mechanical actions (e.g. walking, running, or jumping) can be identified from the generated electrical current without any assistance of external batteries or power sources. It presents the outstanding potential of this hydrogel in building self-powered soft devices including active sensors and artificial skins.

A wheat straw cellulose based semi-IPN hydrogel reactor for metal nanoparticles preparation and catalytic reduction of 4-nitrophenol

A wheat straw cellulose-g-poly(acrylic acid)/poly(vinyl alcohol) semi-IPN hydrogel (WSC-g-PAA/PVA) was synthesized.

Structure and properties of semi-interpenetrating network hydrogel based on starch

Starch-g-P(acrylic acid-co-acrylamide)/PVA semi-interpenetrating network (semi-IPN) hydrogels were prepared by aqueous solution polymerization method. Starch grafting copolymerization reaction, semi-IPN structure and crystal morphology were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The PVA in the form of partial crystallization distributing in the gel matrix uniformly were observed by Field emission scanning electron microscope (FESEM). The space network structure, finer microstructure and pore size in the interior of hydrogel were presented by biomicroscope. The results demonstrated that absorption ratio of water and salt generated different degree changes with the effect of PVA. In addition, the mechanical strength of hydrogel was improved.