Gels

Hydrogels are composed of a three-dimensional network of cross-linked hydrophilic polymer chains and large amounts of water. The physicochemical properties of the polymer-water interface in hydrogels draw our attention. Due to the complex structure of hydrogel systems, it is still a challenge to investigate the interfacial layer properties of hydrogels through experiments. In this work, we investigate the properties of the covalently bonded chitosan-based ice-hydrogels interfacial layer by dielectric relaxation spectroscopy (DRS) techniques in the presence of avoided electrode polarization. The DRS data exhibit that the polymer-water interfacial layer has a strong dielectric signal response, which indicates that a large number of polar electric dipoles or polar molecules may be contained in the interfacial layer. The variable temperature dielectric relaxation behavior of a series of chitosan-base ice-hydrogels showed that the value of dielectric activation energy for different water contents is about 180 kJ/mol, which is much larger than that of the polymer and ice phases, suggesting a strong coupling of polar electric dipoles within the interfacial layer. This work demonstrates the important role of the polymer-water interface in covalently bonded hydrogels, which will provide assistance in the design and application of covalently bonded hydrogels. Full article

The sol-gel technology allows for the development of materials for nonlinear optics and photonics through the synthesis of multifunctional ceramic materials. Although the nature of the amorphous matrix allows the material to be doped with a large amount of the active components without quenching, it may affect the spectroscopic characteristics of the dye (e.g., result in a shift of absorption and emission peaks with drying time, presumably with a change of concentration). This study presents the material (SiO₂ impregnated with organic dyes—Rhodamine 6G and 19) with tunable emissions obtained by the authors upon annealing at different temperatures within the range of 100–300 °C. Possible observed effects were discussed based on spectroscopic properties and thermal studies of the synthesized material. Concerning annealing at different temperatures, an effect on concentration was observed. At the same time, a longer heating process at 300 °C revealed a protective function of sol-gel-derived silica for the organic dye; the longer heating did not cause any further significant changes in the dye’s emission, which indicates the preservative role of the sol-gel layers. Furthermore, etching tests of thin layers were conducted, resulting in smooth side edges of the waveguide. The tests have shown that it is possible to use dye-doped sol-gel layers as active components in photonics platforms. Full article

Hydrogel is a kind of soft and wet matter, which demonstrates favorable fouling resistance owing to the hydration anti-adhesive surfaces. Different from conventional hydrogels constructed by hydrophilic or amphiphilic polymers, the recently invented “hydrophobic hydrogels” composed of hydrophobic polymers exhibit many unique properties, e.g., surface hydrophobicity and high water content, suggesting promising applications in anti-fouling. In this paper, a series of hydrophobic hydrogels were prepared with different chemical structures and water content for anti-fouling investigations. The hydrophobic hydrogels showed high static water contact angles (WCAs > 90°), indicating remarkable surface hydrophobicity, which is abnormal for conventional hydrogels. Compared with the conventional hydrogels, all the hydrophobic hydrogels exhibited less than 4% E. coli biofilm coverage, showing a contrary trend of anti-fouling ability to the water content inside the polymer. Typically, the poly(2-(2-ethoxyethoxy)ethyl acrylate) (PCBA) and poly(tetrahydrofurfuryl acrylate) (PTHFA) hydrogels with relatively high surface hydrophobicity showed as low as 5.1% and 2.4% E. coli biofilm coverage even after incubation for 7 days in bacteria suspension, which are about 0.32 and 0.15 times of that on the hydrophilic poly(N,N-dimethylacrylamide) (PDMA) hydrogels, respectively. Moreover, the hydrophobic hydrogels exhibited a similar anti-adhesion ability and trend to algae S. platensis. Based on the results, the surface hydrophobicity mainly contributes to the excellent anti-fouling ability of hydrophobic hydrogels. In the meantime, the too-high water content may be somehow detrimental to anti-fouling performance. Full article

Ibuprofen is an antipyretic and analgesic drug used for the management of different inflammatory diseases, such as rheumatoid arthritis and osteoarthritis. Due to a short half-life and rapid elimination, multiple doses of ibuprofen are required in a day to maintain pharmacological action for a long duration of time. Due to multiple intakes of ibuprofen, certain severe adverse effects, such as gastric irritation, bleeding, ulcers, and abdominal pain are produced. Therefore, a system is needed which not only prolongs the release of ibuprofen but also overcomes the drug’s adverse effects. Hence, the authors have synthesized chondroitin sulfate/sodium polystyrene sulfonate–co-poly(acrylic acid) hydrogels by the free radical polymerization technique for the controlled release of ibuprofen. Sol-gel, porosity, swelling, and drug release studies were performed on the fabricated hydrogel. The pH-responsive behavior of the fabricated hydrogel was determined by both swelling and drug release studies in three different pH values, i.e., pH 1.2, 4.6, and 7.4. Maximum swelling and drug release were observed at pH 7.4, as compared to pH 4.6 and 1.2. Similarly, the structural arrangement and crosslinking of the hydrogel contents were confirmed by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) evaluated the hard and irregular surface with a few macrospores of the developed hydrogel, which may be correlated with the strong crosslinking of polymers with monomer content. Similarly, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated the high thermal stability of the formulated hydrogel, as compared to pure polymers. A decrease in the crystallinity of chondroitin sulfate and sodium polystyrene sulfonate after crosslinking was revealed by powder X-ray diffraction (PXRD). Thus, considering the results, we can demonstrate that a developed polymeric network of hydrogel could be used as a safe, stable, and efficient carrier for the controlled release of ibuprofen. Full article

Worldwide aquaculture production is increasing, but with this increase comes quality and safety related problems. Hence, there is an urgent need to develop potent technologies to extend the shelf life of fish. Xanthan gum is commonly used in the food industry because of its high-water solubility, stability of its aqueous solutions in a wide pH range, and high viscosity. One of its modern food applications is its use as a gelling agent in edible coatings building. Therefore, in this study, the effect of xanthan coating containing various concentrations (0, 1, 2%; w/v) of ethanolic extract of propolis (EEP) on physicochemical, microbial, and sensory quality indices in mackerel fillets stored at 2 °C for 20 days was evaluated. The pH, peroxide value, K-value, TVB-N, TBARS, microbiological and sensory characteristics were determined every 5 days over the storage period (20 days). Samples treated with xanthan (XAN) coatings containing 1 and 2% of EEP were shown to have the highest level of physicochemical protection and maximum level of microbial inhibition (p < 0.05) compared to uncoated samples (control) over the storage period. Furthermore, the addition of EEP to XAN was more effective in notably preserving (p < 0.05) the taste and odor of coated samples compared to control. Full article

Drug-induced liver injury (DILI) is a leading cause of attrition in drug development or withdrawal; current animal experiments and traditional 2D cell culture systems fail to precisely predict the liver toxicity of drug candidates. Hence, there is an urgent need for an alternative in vitro model that can mimic the liver microenvironments and accurately detect human-specific drug hepatotoxicity. Here, for the first time we propose the fabrication of an albumin methacryloyl cryogel platform inspired by the liver’s microarchitecture via emulating the mechanical properties and extracellular matrix (ECM) cues of liver. Engineered crosslinkable albumin methacryloyl is used as a protein-based building block for fabrication of albumin cryogel in vitro models that can have potential applications in 3D cell culture and drug screening. In this work, protein modification, cryogelation, and liver ECM coating were employed to engineer highly porous three-dimensional cryogels with high interconnectivity, liver-like stiffness, and liver ECM as artificial liver constructs. The resulting albumin-based cryogel in vitro model provided improved cell–cell and cell–material interactions and consequently displayed excellent liver functional gene expression, being conducive to detection of fialuridine (FIAU) hepatotoxicity. Full article

Biosurfactants are eco-friendly surface-active molecules recommended for enhanced oil recovery techniques. In the present study, a potential lipopeptide (biosurfactant) encoding the iturin A gene was synthesized from Bacillus aryabhattai. To improvise the yield of the lipopeptide for specific applications, current research tends toward engineering and expressing recombinant peptides. An iturin A gene sequence was codon-optimized, amplified with gene-specific primers, and ligated into the pET-32A expression vector to achieve high-level protein expression. The plasmid construct was transformed into an E. coli BL21 DE3 host to evaluate the expression. The highly expressed recombinant iturin A lipopeptide was purified on a nickel nitrilotriacetic acid (Ni-NTA) agarose column. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the purity and molecular mass of iturin A was 41 kDa. The yield of recombinant iturin A was found to be 60 g/L with a 6.7-fold increase in comparison with our previously published study on the wild strain. The approach of cloning a functional fragment of partial iturin A resulted in the increased production of the lipopeptide. When motor oil was used, recombinant protein iturin A revealed a biosurfactant property with a 74 ± 1.9% emulsification index (E24). Purified recombinant protein iturin A was characterized by mass spectrometry. MALDI-TOF spectra of trypsin digestion (protein/trypsin of 50:1 and 25:1) showed desired digested mass peaks for the protein, further confirming the identity of iturin A. The iturin A structure was elucidated based on distinctive spectral bands in Raman spectra, which revealed the presence of a peptide backbone and lipid. Recombinant iturin A was employed for enhanced oil recovery through a sand-packed column that yielded 61.18 ± 0.85% additional oil. Hence, the novel approach of the high-level expression of iturin A (lipopeptide) as a promising biosurfactant employed for oil recovery from Bacillus aryabhattai is not much reported. Thus, recombinant iturin A demonstrated its promising ability for efficient oil recovery, finding specific applications in petroleum industries. Full article

The current study depicts the comparative effects of nanogel using Withania coagulans extract, pregabalin alone, and a co-combination gel. The gels prepared were then analyzed for conductivity, viscosity, spread ability, globule size, zeta potential, polydispersity index, and TEM. The globule size of the co-combination gel, determined by zeta sizer, was found to be (329 ± 0.573 nm). FTIR analysis confirms the successful development of gel, without any interaction. Drug distribution at the molecular level was confirmed by XRD. DSC revealed no bigger thermal changes. TEM images revealed spherical molecules with sizes of 200 nm for the co-combination gel. In vivo studies were carried out by infliction of third degree burn wounds on rat skin, and they confirmed that pregabalin and Withania coagulans heals the wound more effectively, with a wound contraction rate of 89.95%, compared to remaining groups. Anti-inflammatory activity (IL-6 and TNF-α), determined by the ELISA technique, shows that the co-combination gel group reduces the maximum inflammation with TNF-α value (132.2 pg/mL), compared to the control (140.22 pg/mL). Similarly, the IL-6 value was found to be (78 pg/mL) for the co-combination gel and (81 pg/mL) in the case of the control. Histopathologically, the co-combination gel heals wounds more quickly, compared to individual gel. These outcomes depict that a co-combination gel using plant extracts and drugs can be successfully used to treat burn injury. Full article

Chitosan-capped silver nanoparticle (CS-capped AgNPs)-incorporated Poly(vinyl alcohol) (PVA) hybrid membranes were prepared by a solution-casting technique for ethanol dehydration via pervaporation. The incorporation of CS-capped AgNPs into the PVA membrane and its influence on membrane properties and pervaporation-separation process of azeotropic water/ethanol mixture was studied. The addition of CS-capped AgNPs into the PVA membrane reduced the crystallinity, thereby increasing the hydrophilicity and swelling degree of the hybrid membrane, supported by contact angle (CA) analyzer and swelling degree experiments, respectively. Fourier transform infrared spectroscopy (FTIR) demonstrated the formation of polymeric matrix between PVA and CS and also the binding of AgNPs onto the functional group of CS and PVA, which was also reflected in the microstructure images demonstrated by scanning electron microscopy (SEM) and by 2θ angle of wide-angle X-ray diffraction (WAXD). The effect of CS-capped AgNPs on the thermal stability of the hybrid membrane was demonstrated by differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). These characteristics of the hybrid membrane positively impact the efficiency of the dehydration of ethanol, as indicated by pervaporation experiments. The best performances in total flux (12.40 ± 0.20 × 10⁻² kg/m² h) and selectivity (3612.33 ± 6.03) at 30 °C were shown for CS-capped AgNPs PVA hybrid membrane containing 2 wt.% CS-capped AgNPs (M-4). This confirms that the developed hybrid membranes can be efficiently used to separate water from azeotropic aqueous ethanol. Full article

Regulated drug delivery is an important direction in the field of medicine and healthcare research. In recent years, injectable hydrogels with good biocompatibility and biodegradability have attracted extensive attention due to their promising application in controlled drug release. Among them, DNA hydrogel has shown great potentials in local drug delivery and immunotherapy. DNA hydrogel is a three-dimensional network formed by cross-linking of hydrophilic DNA strands with extremely good biocompatibility. Benefiting from the special properties of DNA, including editable sequence and specificity of hybridization reactions, the mechanical properties and functions of DNA hydrogels can be precisely designed according to specific applications. In addition, other functional materials, including peptides, proteins and synthetic organic polymers can be easily integrated with DNA hydrogels, thereby enriching the functions of the hydrogels. In this review, we first summarize the types and synthesis methods of DNA hydrogels, and then review the recent research progress of injectable DNA hydrogels in local drug delivery, especially in immunotherapy. Finally, we discuss the challenges facing DNA hydrogels and future development directions. Full article

This study focuses on understanding the effect of ionic strength on the mechanical and microstructural properties of novel composite gels containing 13% whey protein isolate (WPI) and 4% de-structured waxy potato starch (DWPS). The DWPS is a physically modified waxy potato starch treated at 140 °C for 30 min under constant shear. Thermodynamic incompatibility between WPI and DWPS was observed upon the addition of NaCl (~75 mM) or CaCl₂ (10–75 mM). The combined effects of such thermodynamic incompatibility with the changes in protein connectivity induced by varied ionic strength led to the formation of distinctive gel structures (inhomogeneous self-supporting gels with a liquid centre and weak gels with paste-like consistency) that were different from thermodynamic compatible homogeneous self-supporting gels (pure WPI and WPI + maltodextrin gels). At ≥ 250 mM NaCl, instead of a paste-like texture, a recovered soft and creamy self-supporting gel structure was observed when using DWPS. The ability to generate a range of textures in WPI gelation-based foods by using DWPS under different ionic conditions, is a feasible strategy for formulating high-protein foods for dysphagia—aimed to be either thickened fluids or soft solids. Additionally, this acquired knowledge is also relevant when formulating food gels for 3-D printing. Full article

The Antheraea Pernyi silk gland protein originates from natural organisms and synthesized by tussah silk glands and has widely potential biomaterial applications due to the superior biocompatibility. This study investigates the Antheraea Pernyi silk gland protein-based drug-loaded bio-hydrogels for bioengineered tissue fabricated by using an eco-friendly method without the harsh extracting process and the usage of toxic chemicals. The drug-loaded bio-hydrogels exhibited a porous structure and interconnected pore walls. The swelling ratio and water absorption of drug-loaded bio-hydrogels were, respectively, above 95% and 1.5 × 10³%. The cumulative release of drug loaded hydrogels all reached more than 90% within 4 h, and this indicates the potential of drug-loaded hydrogels as future drug-carrying biomaterials. RSC96 Schwann cells cultured on drug-loaded hydrogels for 72 h under cell culture medium show no toxic effects and more pro-proliferative effects. The results suggest the suitability of drug-loaded bio-hydrogels as natural biopolymer for the potential in vitro RSC96 cell culture platform and other biomaterial applications. Full article

The unique bactericidal mechanism of metal nanoparticles (MNPs) is considered to be an effective strategy to deal with antibiotic resistance, but the oxidative stress damage caused by excessive accumulation of MNPs to normal cells cannot be ignored. Achieving on-demand release of nano-drugs in specific infection environments is highly attractive. Herein, we constructed a “core-shell” nanogel ([email protected]) based on a copper sulfide (CuS) antimicrobial agent and gelatin for targeted drug release and bacterial clearance in a gelatinase infected microenvironment. [email protected] produced heat and reactive oxygen species (ROS) under the irradiation of a laser, which together with the released Cu²⁺ cause irreversible and efficient physical damage to the bacteria. Moreover, the encapsulation of gelatin not only limits the biotoxicity of CuS nanodots (NDs), but also effectively promotes the proliferation of mammalian cells. Under the synergy of multiple mechanisms, [email protected] eradicated the colonized bacteria in the wound of mice infected with Staphylococcus aureus (S. aureus) and accelerated wound healing. The proposed application strategy of nanogel is expected to provide a new idea for clinical transformation. Full article

The existing plugging removal operation in JZ9-3 oilfield has the disadvantages of small amount of plugging remover, fast injection speed, and short construction time. Under the condition of injection well suction profile reversal, plugging remover is difficult to enter the low permeability part and play the role of deep plugging removal. In order to improve the plugging removal effect, this paper used the physical simulation method to carry out the experimental study and mechanism analysis on the effect of water flooding, chemical flooding, and plugging removal measures of the multi-layer system combination model. The results showed that the recovery of general plugging removal after chemical flooding increases by only 0.70%, while the recovery of ‘profile control + plugging removal’ increases by ‘9.34% + 2.59%’, and the amount of produced liquid decreases by more than 40%. It can be seen that the combined operation of profile control and plugging removal has dual effects of plugging and dredging and synergistic effect, which not only expands the swept volume, but also reduces the inefficient and ineffective cycles. On this basis, the optimization design and effect prediction of the target well W4-2 plugging removal scheme were carried out by using the numerical simulation method. Recommended scheme: inorganic gel profile control agent volume 13,243.6 m³, produced by the main agent (Na₂O·nSiO₂), isolation fluid (Water), and auxiliary agent (CaCl₂) through multiple rounds of alternating injection into the reservoir. The plug removal agent (K₂S₂O₈) injection volume is 100 m³, the concentration is 0.8%. The post-implementation ‘Output/Input’ ratio is expected to be 3.7. Full article

The purpose of the current investigation was to formulate, assess, and optimize oral in situ gels of buspirone hydrochloride (BH) with the specific end goal of expanding the time the medication spends in the stomach, thereby ensuring an extended medication discharge. This would allow the use of a once-a-day dose of liquid BH formulations, which is ideal for the treatment of pediatric anxiety. In situ gels loaded with BH were prepared using various concentrations of sodium alginate (Na alg.), calcium chloride (CaCl₂), and hydroxypropyl methylcellulose (HPMC K15M). The in situ gels exhibited the desired consistency, drug distribution, pH, ability to form gel, and prolonged drug release in vitro. The (3³) full factorial design was utilized for the revealing of the ideal figures for the selected independent variables, Na alg. (X₁), HPMC (X₂), and CaCl₂ (X₃) based on measurements of the viscosity (Y₁) and percentage drug release after 6 h (Y₂). A pharmacokinetic study of the optimum formulation on rabbits was also performed. The formulation containing 2% of Na alg., 0.9% of HPMC-K15M, and 0.1125% of CaCl₂ was selected as the ideal formulation, which gave the theoretical values of 269.2 cP and 44.9% for viscosity and percentage of drug released after 6 h, respectively. The pharmacokinetic study showed that the selected oral Na alg. in situ gel formulation displayed a prolonged release effect compared to BH solution and the marketed tablet (Buspar^®), which was confirmed by the low C_max and high T_max values. The optimum oral Na alg. in situ gel showed a 1.5-fold increment in bioavailability compared with the drug solution. Full article

Hydrogels are cross-linked polymer networks swollen in water. The large solvent content enables hydrogels to have unique physical properties and allows them to be used in diverse applications such as tissue engineering, drug delivery, and absorbents. Gel properties are linked to internal dynamics. While bulk gel dynamics have been studied extensively, how gel networks respond locally to deformation has yet to be understood. Here, poly(vinyl alcohol) (PVA) gels have been stretched to study the effects of deformation on gel dynamics parallel and perpendicular to the stretching direction using dynamic small angle light scattering (DSALS). The implementation of DSALS is described and compared to traditional DLS for PVA gels with different crosslink densities, ranging from 0.75–2%. Despite the orders of magnitude difference in the scattering vector, q, range of the techniques, the dynamics match, and the apparent elastic diffusion coefficient, D_A increases linearly with the crosslink density for unstretched gels at a constant 2 wt% concentration. We observe that the elastic motion depends on the direction of stretch, decreasing perpendicular to stretching and increasing at parallel direction. Using DSALS can therefore be an effective tool to evaluate local hydrogel response to deformation. Full article

Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (M_w) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications. Full article

In this work, silica aerogel composites reinforced with reticulated polyurethane (PU) foams have been manufactured having densities in the range from 117 to 266 kg/m³ and porosities between 85.7 and 92.3%. Two different drying processes were employed (ambient pressure drying and supercritical drying) and a surface modification step was applied to some of the silica formulations. These composites, together with the reference PU foam and the monolithic silica aerogels, were fully characterized in terms of their textural properties, mechanical properties and thermal conductivities. The surface modification with hexamethyldisilazane (HMDZ) proved to improve the cohesion between the reticulated foam and the silica aerogels, giving rise to a continuous network of aerogel reinforced by a polyurethane porous structure. The samples dried under supercritical conditions showed the best interaction between matrixes as well as mechanical and insulating properties. These samples present better mechanical properties than the monolithic aerogels having a higher elastic modulus (from 130 to 450 kPa), a really exceptional flexibility and resilience, and the capacity of being deformed without breaking. Moreover, these silica aerogel-polyurethane foam (Sil-PU) composites showed an excellent insulating capacity, reaching thermal conductivities as low as 14 mW/(m·K). Full article

Circulating tumor cells (CTCs) are indicators for the detection, diagnosis, and monitoring of cancers and offer biological information for the development of personalized medicine. Techniques for the specific capture and non-destructive release of CTCs from millions of blood cells remain highly desirable. Here, we present a CTC capture-and-release system using a disulfide-containing poly(carboxybetaine methacrylate) (pCB) hydrogel. The non-fouling characteristic of pCB prevents unwanted, nonspecific cell binding, while the carboxyl functionality of pCB is used for the conjugation of anti-epithelial cell adhesion molecule (anti-EpCAM) antibodies for the capture of CTCs. The results demonstrated that the anti-EpCAM-conjugated pCB hydrogel captured HCT116 cells from blood, and the capture ratio reached 45%. Furthermore, the captured HCT116 cells were released within 30 min from the dissolution of the pCB hydrogel by adding cysteine, which breaks the disulfide bonds of the crosslinkers. The cells released were viable and able to grow. Our system has potential in the development of a device for CTC diagnosis. Full article