Fabrication and Optimization of the Thermo-Sensitive Hydrogel Carboxymethyl Cellulose/Poly(N-isopropylacrylamide-co-acrylic acid) for U(VI) Removal from Aqueous Solution

Progress in the Application of Hydrogels in Intervertebral Disc Repair: A Comprehensive Review

PURPOSE OF REVIEW

Intervertebral disc degeneration (IVDD) is a common orthopaedic disease and an important cause of lower back pain, which seriously affects the work and life of patients and causes a large economic burden to society. The traditional treatment of IVDD mainly involves early pain relief and late surgical intervention, but it cannot reverse the pathological course of IVDD. Current studies suggest that IVDD is related to the imbalance between the anabolic and catabolic functions of the extracellular matrix (ECM). Anti-inflammatory drugs, bioactive substances, and stem cells have all been shown to improve ECM, but traditional injection methods face short half-life and leakage problems.

RECENT FINDINGS

The good biocompatibility and slow-release function of polymer hydrogels are being noticed and explored to combine with drugs or bioactive substances to treat IVDD. This paper introduces the pathophysiological mechanism of IVDD, and discusses the advantages, disadvantages and development prospects of hydrogels for the treatment of IVDD, so as to provide guidance for future breakthroughs in the treatment of IVDD.

Preparation and characterization of photosensitive methacrylate-grafted sodium carboxymethyl cellulose as an injectable material to fabricate hydrogels for biomedical applications

Injectable materials have attracted great attention in the manufacture of in situ forming hydrogels for biomedical applications. In this study, a facile method to prepare methacrylic anhydride (MA)-modified sodium carboxymethyl cellulose (CMC) as an injectable material for the fabrication of hydrogels with controllable properties is reported. The chemical structure of the series of MA-grafted CMC (CMCMAs) with different MA contents was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopy, and the properties of CMCMAs were characterized. Then, the CMCMAs gel (CMCMAs-G) was fabricated by crosslinking of MA under blue light irradiation. The gelation performances, swelling behaviors, transmittance, surface porous structures and mechanical properties of CMCMAs-G can be controlled by varying the content of MA grafted on the CMC. The compressive strength of CMCMAs-G was measured by mechanical compressibility tests and up to 180 kPa. Furthermore, the in vitro cytocompatibility evaluation results suggest that the obtained CMCMAs-G exhibit good compatibility for cell proliferation. Hence, our strategy provides a facile approach for the preparation of light-sensitive and an injectable CMC-derived polymer to fabricate hydrogels for biomedical applications.

Gold nanorod-chitosan based nanocomposites for photothermal and chemoembolization therapy of breast cancer

Gold nanorods (AuNR) have received significant attention in tumor thermo-chemotherapy. However, insufficient thermal availability limits the in vivo highly efficient applications of AuNR in photothermal therapy. In this study, we have fabricated N-isopropylacrylamide grafted O-carboxymethyl chitosan nanoparticles (NCMC NPs) with thermo-responsive properties for co-encapsulating AuNR and doxorubicin (DOX), forming AuNR@NCMC/DOX nanocomposites (NCs). As a result of the thermo- and photothermal-responsiveness, AuNR@NCMC/DOX NCs exhibited irreversible aggregation at high temperature and under near-infrared (NIR) irradiation with an increase of size to 3 μm. When AuNR@NCMC/DOX NCs reached tumor sites following intravenous administration, they were located in the tumor vessels under NIR irradiation due to an embolization effect. This response enhanced tumor targeting, on-demand release, and the thermal performance of AuNR@NCMC/DOX NCs. We have observed higher tumor accumulation of DOX and AuNR with subsequent stronger inhibition of tumor growth than that achieved without NIR irradiation. The development of AuNR-based NCs with multiple smart responsivenesses at tumors can provide a promising paradigm for solid tumor treatment via the cooperative effects of photothermal therapy and chemoembolization.

Regulated Self-Folding in Multi-Layered Hydrogels Considered with an Interfacial Layer

Multi-layered hydrogels consisting of bi- or tri-layers with different swelling ratios are designed to soft hydrogel actuators by self-folding. The successful use of multi-layered hydrogels in this application greatly relies on the precise design and fabrication of the curvature of self-folding. In general, however, the self-folding often results in an undesired mismatch with the expecting value. To address this issue, this study introduces an interfacial layer formed between each layered hydrogel, and this layer is evaluated to enhance the design and fabrication precision. By considering the interfacial layer, which forms through diffusion, as an additional layer in the multi-layered hydrogel, the degree of mismatch in the self-folding is significantly reduced. Experimental results show that as the thickness of the interfacial layer increases, the multi-layered hydrogel exhibits a 3.5-fold increase in its radius of curvature during the self-folding. In addition, the diffusion layer is crucial for creating robust systems by preventing the separation of layers in the muti-layered hydrogel during actuation, thereby ensuring the integrity of the system in operation. This new strategy for designing multi-layered hydrogels including an interfacial layer would greatly serve to fabricate precise and robust soft hydrogel actuators.

Selective, rapid extraction of uranium from aqueous solution by porous chitosan-phosphorylated chitosan-amidoxime macroporous resin composite and differential charge calculation

Herein, a new porous chitosan-phosphorylated chitosan-amidoxime macroporous resin composite (PCAR) was designed and synthesized for the rapid and selective extraction of uranium resources from aqueous solution. This study showed that PCAR exhibited excellent adsorption toward uranium in a pH range of 5-9. The dynamic adsorption process aligned with the quasi-second-order kinetic model and corresponded to the chemical adsorption process. The maximum adsorption capacity was 561.28 mg·g-1 at pH 6 and 308 K. Mechanism analysis showed that the synergistic effect of the amidoxime group (-(NH2)C=N-OH), PO, and -NH2 on the PCAR surface improved the uranium adsorption performance. The differential charge density indicated that the amidoxime and phosphate groups provide lone-pair electrons for the adsorption of UO22+ and their synergistic effect improves the UO22+ adsorption performance of PCAR. The uranium distribution coefficients of PCAR and CAR are 4.6 and 2.4 times those of vanadium, respectively. These results indicate that phosphorylation can ameliorate the disadvantage of competitive vanadium adsorption of the amidoxime adsorbent. In addition, PCAR exhibits good reusability and stable adsorption capacity after five adsorption-desorption cycles. Hence, PCAR has excellent potential for uranium extraction from aqueous solution.

A comprehensive performance evaluation of the cement-based expanded perlite plastering mortar

A single performance evaluation does not cover all the situations encountered in cement-based plastering mortar applications in walls. This paper proposes a comprehensive performance evaluation method for assessing the cement-based plastering mortar by comprehensively considering the physical characteristics, microstructures, thermal performances, mechanical properties and adsorbability of materials. The relative performances of each test item were compared with standards and previous studies, and the calculation equation of the comprehensive performance value was obtained. In this study, the common cement plastering mortar (CM) and lightweight mortar were mixed with expanded and vitrified beads as aggregates mortar (EVBM), wood fibres, sepiolite and expanded perlite-based plastering mortar (WM) and three types of homemade optimized mortars were moulded as testing specimens. The reference material was marked as CM, and the weights of each parameter in the equation were artificially set according to the applied conditions of the building and restricted by the comprehensive performance value of the ideal plastering mortar at the same time. Through the evaluation of the comprehensive performance and the calculation of these mortars from a case setting of weights, the combined mixing of diatomite, sepiolite with fly ash is better than each single material mixed in mortars, and the comprehensive performance value of mortars with a single function is functional, such as thermal insulation mortar. This paper provides an evaluation method for the comprehensive application of cement-based plastering mortar on the wall.

Dually-Thermoresponsive Hydrogel with Shape Adaptability and Synergetic Bacterial Elimination in the Full Course of Wound Healing

Incomplete contact between a pre-formed hydrogel and irregular wound limits the therapeutic effect of the dressing and increases the risk of infection; while great concerns have remained regarding the potential toxicity of the residual additives of chemical crosslinking for in situ forming hydrogels. Therefore, it is desirable to develop a self-adaptive hydrogel in response to skin temperature with shape adaptability and efficient antibacterial properties to prevent microbial invasion. Herein, a dually-thermoresponsive hydrogel composed of poly(N-isopropylacrylamide) (PNIPAm) and methacrylated κ-carrageenan (MA-κ-CA) is designed with compliance at physiological temperature to realize shape adaptability for completely covering irregular wounds. Furthermore, the hydrogel with near-infrared (NIR)-responsive polypyrrole-polydopamine nanoparticles (PPy-PDA NPs) and Zn²⁺ -derived zeolitic imidazolate framework (ZIF-8) can generate localized heat and gradually release Zn²⁺ to realize safe, effective synergetic photothermal-chemical bactericidal capability. In addition, the release rate of Zn²⁺ can be accelerated by NIR-induced heating, and thus a more efficient sterilization can be provided to severely infected wounds. Therefore, the proposed hydrogel would serve as a promising wound dressing for the full course of wound healing, with the abilities of perfectly covering the wound and adapting to regenerating tissue, and controllable photothermal-chemical antibacterial capability to reach high bactericidal efficiency and long-term release of antibacterial agents.

Mesoporous Magnetic Cysteine Functionalized Chitosan Nanocomposite for Selective Uranyl Ions Sorption: Experimental, Structural Characterization, and Mechanistic Studies

Nuclear power facilities are being expanded to satisfy expanding worldwide energy demand. Thus, uranium recovery from secondary resources has become a hot topic in terms of environmental protection and nuclear fuel conservation. Herein, a mesoporous biosorbent of a hybrid magnetic–chitosan nanocomposite functionalized with cysteine (Cys) was synthesized via subsequent heterogeneous nucleation for selectively enhanced uranyl ion (UO₂²⁺) sorption. Various analytical tools were used to confirm the mesoporous nanocomposite structural characteristics and confirm the synthetic route. The characteristics of the synthesized nanocomposite were as follows: superparamagnetic with saturation magnetization (M_S: 25.81 emu/g), a specific surface area (S_BET: 42.56 m²/g) with a unipore mesoporous structure, an amine content of ~2.43 mmol N/g, and a density of ~17.19/nm². The experimental results showed that the sorption was highly efficient: for the isotherm fitted by the Langmuir equation, the maximum capacity was about 0.575 mmol U/g at pH range 3.5–5.0, and Temperature (25 ± 1 °C); further, there was excellent selectivity for UO₂²⁺, likely due to the chemical valent difference. The sorption process was fast (~50 min), simulated with the pseudo-second-order equation, and the sorption half-time (t_1/2) was 3.86 min. The sophisticated spectroscopic studies (FTIR and XPS) revealed that the sorption mechanism was linked to complexation and ion exchange by interaction with S/N/O multiple functional groups. The sorption was exothermic, spontaneous, and governed by entropy change. Desorption and regeneration were carried out using an acidified urea solution (0.25 M) that was recycled for a minimum of six cycles, resulting in a sorption and desorption efficiency of over 91%. The as-synthesized nanocomposite’s high stability, durability, and chemical resistivity were confirmed over multiple cycles using FTIR and leachability. Finally, the sorbent was efficiently tested for selective uranium sorption from multicomponent acidic simulated nuclear solution. Owing to such excellent performance, the Cys nanocomposite is greatly promising in the uranium recovery field.

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.

Knee Osteoarthritis Therapy: Recent Advances in Intra-Articular Drug Delivery Systems

Drug delivery for osteoarthritis (OA) treatment is a continuous challenge because of their poor bioavailability and rapid clearance in joints. Intra-articular (IA) drug delivery is a common strategy and its therapeutic effects depend mainly on the efficacy of the drug-delivery system used for OA therapy. Different types of IA drug-delivery systems, such as microspheres, nanoparticles, and hydrogels, have been rapidly developed over the past decade to improve their therapeutic effects. With the continuous advancement in OA mechanism research, new drugs targeting specific cell/signaling pathways in OA are rapidly evolving and effective drug delivery is critical for treating OA. In this review, recent advances in various IA drug-delivery systems for OA treatment, OA targeted strategies, and related signaling pathways in OA treatment are summarized and analyzed based on current publications.

Water treatment using stimuli-responsive polymers

Stimuli-responsive polymers are a new category of smart materials used in water treatment via a stimuli-induced purification process and subsequent regeneration processes.

Smart Adsorbents for Aquatic Environmental Remediation

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.

A nappies management by-product for the treatment of uranium-contaminated waters

The direct disposal of municipal solid waste such as nappies to the environment may create serious pollution problems. Based on the circular economy and waste management concepts, the conversion of nappies and/or their ingredients (such as super absorbent polymer (SAP)) to high added value products is of great importance. In this work, a modified SAP (MSAP) was examined as an adsorbent for treatment of contaminated waters and uranium recovery. Batch experiments and spectroscopic techniques were used to examine the effect of various parameters (pH, contact time, temperature, initial concentration, and ionic strength), and the mechanism of adsorption U(VI) and desorption process. The U(VI) concentration was determined by alpha spectroscopy after addition of ²³²U standard tracer solution to account for possible interferences during electrodeposition and alpha particle counting. The maximum adsorption monolayer capacity was found to be 217.4 mg/g at pH 4.0 and at 298 K. The adsorption of U(VI) on MSAP seems to occur mainly via the formation of inner-sphere surface complexes between U(VI) and the carboxylic surface moieties of MSAP. The MSAP could satisfactorily be regenerated with 0.1 M Na₂CO₃ (>90%) and it also shows a promising applicability to real wastewaters contaminated with U(VI).

Experimental Study on Thermosensitive Hydrogel Used to Extinguish Class A Fire

Hydrogels are crosslinked polymers that become fully swollen when placed in aqueous environments. They are widely used in the field of firefighting because they can remarkably increase the viscosity and wettability of water. In this study, a thermosensitive hydrogel used to effectively suppress class A fire was synthesized by using methylcellulose, sodium polyacrylate, and magnesium chloride. The structure, surface activity and viscosity of the hydrogel were characterized. Fire extinguishing performance was evaluated based on small-scale and large-scale experiments. The results showed that a phase transition of the hydrogel occurred when the temperature rose from 50 °C to 80 °C. After the phase transition, the hydrogel showed a higher viscosity and lower surface tension, which was conducive to attach to the surface of the burning material and acting as an effective barrier to isolate oxygen. The small-scale fire extinguishing tests indicated that the concentration of the hydrogel solution has an eminent influence on fire extinguishing performance. The optimum concentration for extinguishing performance was around 6 wt%. The large-scale experiments demonstrated that the fire-extinguishing performance of this thermosensitive hydrogel was superior to the two other commercial water-based fire extinguishing agents, as it prevented re-ignition highly efficiently.

Crosslinked Carboxymethyl Sago Starch/Citric Acid Hydrogel for Sorption of Pb2+, Cu2+, Ni2+ and Zn2+ from Aqueous Solution

In the present study, CMSS (carboxymethyl sago starch)-based hydrogel was synthesized by crosslinking with citric acid via esterification and then applied as a metal sorbent to overcome excessive heavy metal pollution. The CMSS/CA (carboxymethyl sago starch/citric acid) hydrogel was characterized by Fourier Transform Infrared (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The absorption band at 1726 cm⁻¹ was observed in the FT-IR spectrum of CMSS/CA hydrogel and indicated ester bonds formed. Further findings show that the cross-linkages in the CMSS/CA hydrogel increased the thermal stability of CMSS and various sizes of pores were also shown in the SEM micrograph. Conversely, the removal of heavy metals was analyzed using Inductively Coupled Plasma-Optic Emission Spectra (ICP-OES). The effects of the pH of the metal solution, contact time, initial concentration of the metal ions and temperature on the sorption capacity were investigated. Under optimum condition, the sorption capacity of Pb²⁺, Cu²⁺, Ni²⁺ and Zn²⁺ onto CMSS/CA hydrogel were 64.48, 36.56, 16.21, 18.45 mg/g, respectively. The experiments demonstrated that CMSS/CA hydrogel has high selectivity towards Pb²⁺ in both non-competitive and competitive conditions. In conclusion, the CMSS/CA hydrogel as a natural based heavy metal sorption material exhibited a promising performance, especially in the sorption of Pb²⁺ for wastewater treatment.

Preparation and Photochromic Performance of Homogeneous Phase Nitrocellulose Membrane Grafting Spirooxazine Moieties

The synthesis of 1,3,3-trimethyl-9′-acryloxyspiro[indoline-2,3′(3H)naphtho[2,1-b][l,4]-oxazine] (AISO) was carried out by catalytic esterification of 1,3,3-trimethyl-9′-hydroxyspiro-[indoline-2,3′(3H)naphtho[2,1-b][l,4]oxazine] (SO–OH) and acrylic acid in the presence of 1,3-dicyclohexylcarbodiimide (DCC) and N-dimethylaminopyridine (DMAP). Then, the synthesis of the target copolymer (NC-g-AISO) was was carried out by benzoyl peroxide (BPO)-induced graft copolymerization of the AISO monomer onto nitrocellulose (NC) in a homogeneous methyl isobutyl ketone medium. The structure of NC-g-AISO was characterized by Fourier transform infrared (IR) spectroscopy, 13C Nuclear Magnetic Resonance (NMR) spectra and thermogravimetric (TG) analysis. The photochromic properties of NC-g-AISO were investigated by examining UV–Vis spectra in ethyl acetate solution and solid membrane. Compared with the AISO monomer in ethyl acetate solution, the thermal color decay stability of the colored form of NC-g-AISO in ethyl acetate solution and in solid membrane improved significantly. The thermal color decay reaction rate constants in ethyl acetate solution and membrane at 25 °C were 1.77 × 10–2 and 1.36 × 10–3 s–1, respectively, fitted using the first-order reaction equation. After ten photochromic cycles, the relative absorption intensity of the colored form of NC-g-AISO decreased by 0.85%, indicating that the NC-g-AISO membrane has good reversible photochromic behavior.

An Active and Soft Hydrogel Actuator to Stimulate Live Cell Clusters by Self-folding

The hydrogels are widely used in various applications, and their successful uses depend on controlling the mechanical properties. In this study, we present an advanced strategy to develop hydrogel actuator designed to stimulate live cell clusters by self-folding. The hydrogel actuator consisting of two layers with different expansion ratios were fabricated to have various curvatures in self-folding. The expansion ratio of the hydrogel tuned with the molecular weight and concentration of gel-forming polymers, and temperature-sensitive molecules in a controlled manner. As a result, the hydrogel actuator could stimulate live cell clusters by compression and tension repeatedly, in response to temperature. The cell clusters were compressed in the 0.7-fold decreases of the radius of curvature with 1.0 mm in room temperature, as compared to that of 1.4 mm in 37 °C. Interestingly, the vascular endothelial growth factor (VEGF) and insulin-like growth factor-binding protein-2 (IGFBP-2) in MCF-7 tumor cells exposed by mechanical stimulation was expressed more than in those without stimulation. Overall, this new strategy to prepare the active and soft hydrogel actuator would be actively used in tissue engineering, drug delivery, and micro-scale actuators.