Gels, Volume 9, Issue 10 (October 2023) – 71 articles

Polypyrrole-gelatin aerogels, containing magnetic barium ferrite (BaFe) particles, (PPy-G-BaFe) were synthesized by oxidative cryopolymerization and used as adsorbents for the removal of Cr(VI) from aqueous media. The removal was performed at pH 4, which was shown to be the optimal value, due to HCrO₄⁻ being the dominant species in these conditions and its more favorable adsorption and reduction compared to CrO₄²⁻, present at pH > 4. It was found that the presence of magnetic BaFe particles had no effect on the adsorption performance of PPy aerogels in terms of capacity and kinetics, which was attributed to its relatively low content in the composite. After the adsorption, the presence of chromium in the composites was confirmed by EDX and its electrostatic interaction with the adsorbent was pointed at by vibrational spectroscopy, corresponding to the accepted adsorption mechanism. The adsorption kinetics followed the pseudo-second-order model pointing at chemisorption being the rate-limiting step. The adsorption isotherm data was best fitting with the Temkin model. The maximum adsorption capacity, calculated using the Langmuir model, was 255.8 mg g⁻¹ (the maximum experimental value was 161.6 mg g⁻¹). Additionally, the possibility of Cr(VI) adsorption in the presence of Cl⁻, Br⁻, NO₃⁻ and SO₄²⁻ as interfering ions was shown. Full article

Aerogels emerge as captivating contenders within the realm of high-temperature thermal resistance and thermal insulation. Nevertheless, their practical applications are usually constrained by their inherent brittleness when subjected to rigorous conditions. Herein, employing hafnium dichloride oxide octahydrate (HfOCl₂·8H₂O) as the hafnium source and resorcinol–formaldehyde (RF) as the carbon precursor, hafnium carbide (HfC) aerogels are fabricated via the sol-gel method complemented with carbothermal reduction reaction. Investigations are conducted into the effects of various molar ratios, duration, and temperatures of calcination on the microstructural features and physico-chemical characteristics of the as-prepared HfC aerogel. The aerogel shows a high BET-specific surface area (601.02 m²/g), which is much larger than those of previously reported aerogels. Furthermore, the HfC aerogel exhibits a low thermal conductivity of 0.053 W/(m·K) and a compressive strength of up to 6.12 MPa after carbothermal reduction at 1500 °C. These excellent thermal insulation and mechanical properties ensure it is ideal for the utilization of high-temperature thermal resistance and thermal insulation in the fields of aerospace. Full article

In recent years, significant advancements in the field of advanced materials and hydrogel engineering have enabled the design and fabrication of smart hydrogels and nanogels that exhibit sensitivity to specific signals or pathological conditions, leading to a wide range of applications in drug delivery and disease treatment. This comprehensive review aims to provide an in-depth analysis of the stimuli-responsive principles exhibited by smart hydrogels in response to various triggers, such as pH levels, temperature fluctuations, light exposure, redox conditions, or the presence of specific biomolecules. The functionality and performance characteristics of these hydrogels are highly influenced by both their constituent components and fabrication processes. Key design principles, their applications in disease treatments, challenges, and future prospects were also discussed. Overall, this review aims to contribute to the current understanding of gel-based drug delivery systems and stimulate further research in this rapidly evolving field. Full article

To treat certain vitreoretinal diseases, the vitreous body, a hydrogel composed of mostly collagen and hyaluronic acid, must be removed. After vitrectomy surgery, the vitreous cavity is filled with an endotamponade. Previously, pre-clinical hydrogel-based vitreous body substitutes either made from uncrosslinked monomers (1st generation), preformed crosslinked polymers (2nd generation), or in situ gelating polymers (3rd generation) have been developed. Forward light scattering is a measure of Stray light induced by optical media, when increased, causing visual disturbance and glare. During pinhole surgery, the hydrogels are injected into the vitreous cavity through a small 23G-cannula. The aim of this study was to assess if and to what extent forward light scattering is induced by vitreous body replacement hydrogels and if Stray light differs between different generations of vitreous body hydrogel replacements due to the different gelation mechanisms and fragmentation during injection. A modified C-Quant setup was used to objectively determine forward light scattering. In this study, we found that the 1st and 3rd generation vitreous body replacements show very low stray light levels even after injection (2.8 +/− 0.4 deg²/sr and 0.2 +/− 0.2 deg²/sr, respectively) as gel fragmentation and generation of interfaces is circumvented. The 2nd generation preformed hydrogels showed a permanent increase in stray light after injection that will most likely lead to symptoms such as glare when used in patients (11.9 +/− 0.9 deg²/sr). Stray light of the 2nd generation hydrogels was 3- and 2-fold increased compared to juvenile and aged vitreous bodies, respectively. In conclusion, this significant downside in the forward light scattering of the 2nd generation hydrogels should be kept in mind when developing vitreous body replacement strategies, as any source of stray light should be minimized in patients with retinal comorbidities. Full article

The changes in storage loss, water distribution status, gel characteristics, thiobarbituric acid reactive substances (TBARSs), total volatile basic nitrogen, and total plate count of cooked reduced-phosphate silver carp surimi batter during cold storage at 4 °C were investigated. The storage loss, content of free water, pH, hardness, TBARSs, total volatile basic nitrogen value, and total plate count of all cooked silver carp surimi batters significantly increased (p < 0.05) with an increase in cold storage time. Meanwhile, the content of immobilized water, whiteness, springiness, and cohesiveness significantly decreased (p < 0.05). At the same cold storage time, the sample of cooked reduced-phosphate silver carp surimi batter had lower water mobility, darker color, and better texture characteristics than the cooked silver carp surimi batter without potassium bicarbonate; however, the values of TBARSs, total volatile basic nitrogen, and total plate count were not significantly different (p > 0.05). This meant that there was no difference between potassium bicarbonate and sodium tripolyphosphate in antioxidant and antibacterial activity during the cold storage of silver carp surimi batter. To summarize, the use of potassium bicarbonate instead of sodium tripolyphosphate could produce cooked reduced-phosphate silver carp surimi batter with better water-holding capacity and gel characteristics during cold storage. Full article

Transparent soil (TS) was specifically designed to support root growth in the presence of air, water, and nutrients and allowed the time-resolved phenotyping of roots in vivo. Nevertheless, it is imperative to further optimize the reagent cost of TS to enable its wider utilization. We substituted the costly Phytagel obtained from Sigma with two more economical alternatives, namely Biodee and Coolaber. TS beads from each brand were prepared using 12 different polymer concentrations and seven distinct crosslinker concentrations. A comprehensive assessment encompassing transparency, mechanical characteristics, particle size, porosity, and stability of TS was undertaken. Compared to the Sigma Phytagel brand, both Biodee and Coolaber significantly reduced the transparency and collapse stress of the TS they produced. Consequently, this led to a significant reduction in the allowable width and height of the growth box, although they could still simultaneously exceed 20 cm and 19 cm. There was no notable difference in porosity and stability among the TS samples prepared using the three Phytagel brands. Therefore, it is feasible to consider replacing the Phytagel brand to reduce TS production costs. This study quantified the differences in TS produced using three Phytagel brands at different prices that will better promote the application of TS to root phenotypes. Full article

Decellularized extracellular matrix (dECM) hydrogels have emerged as promising materials in tissue engineering. The steps to produce dECM hydrogels containing the bioactive epitopes found in the native matrix are often laborious, including the initial harvesting and decellularization of the animal organ. Furthermore, resulting hydrogels often exhibit weak mechanical properties that require the use of additional crosslinkers such as genipin to truly simulate the mechanical properties of the desired study tissue. In this work, we have developed a protocol to readily obtain tens of thin dECM hydrogel cryosections attached to a glass slide as support, to serve as scaffolds for two-dimensional (2D) or three-dimensional (3D) cell culture. Following extensive atomic force microscopy (AFM)-based mechanical characterization of dECM hydrogels crosslinked with increasing genipin concentrations (5 mM, 10 mM, and 20 mM), we provide detailed protocol recommendations for achieving dECM hydrogels of any biologically relevant stiffness. Given that our protocol requires hydrogel freezing, we also confirm that the approach taken can be further used to increase the mechanical properties of the scaffold in a controlled manner exhibiting twice the stiffness in highly crosslinked arrays. Finally, we explored the effect of ethanol-based short- and long-term sterilization on dECM hydrogels, showing that in some situations it may give rise to significant changes in hydrogel mechanical properties that need to be taken into account in experimental design. The hydrogel cryosections produced were shown to be biocompatible and support cell attachment and spreading for at least 72 h in culture. In brief, our proposed method may provide several advantages for tissue engineering: (1) easy availability and reduction in preparation time, (2) increase in the total hydrogel volume eventually used for experiments being able to obtain 15–22 slides from a 250 µL hydrogel) with a (3) reduction in scaffold variability (only a 17.5 ± 9.5% intraslide variability provided by the method), and (4) compatibility with live-cell imaging techniques or further cell characterization of cells. Full article

In this review, we focused on recent efforts in the design and development of materials with biomimetic properties. Innovative methods promise to emulate cell microenvironments and tissue functions, but many aspects regarding cellular communication, motility, and responsiveness remain to be explained. We photographed the state-of-the-art advancements in biomimetics, and discussed the complexity of a “bottom-up” artificial construction of living systems, with particular highlights on hydrogels, collagen-based composites, surface modifications, and three-dimensional (3D) bioprinting applications. Fast-paced 3D printing and artificial intelligence, nevertheless, collide with reality: How difficult can it be to build reproducible biomimetic materials at a real scale in line with the complexity of living systems? Nowadays, science is in urgent need of bioengineering technologies for the practical use of bioinspired and biomimetics for medicine and clinics. Full article

Background: Dermatitis is skin disorder that is complicated by recurrent infections of skin by bacteria, viruses, and fungi. Spilanthol is an active constituent of Spilanthes acmella, which possess strong anti-bacterial properties. The purpose of this study was to develop a herbal emulgel for the treatment of dermal bacterial infections, as microscopic organisms have created solid resistance against anti-microbials. Methods: Emulgels were prepared and characterized for parameters such as physical examination, rheological studies, spreading coefficient, bio-adhesive strength measurement, extrudability study, antibacterial activity, FTIR analysis, in vitro drug dissolution, and ex vivo permeation studies. Result: With a statistically significant p-value = 0.024, 100% antibacterial activity was observed by F4 against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli (mean ± S.D) (25.33 ± 0.28, 27.33 ± 0.5, and 27 ± 0.5). However, maximum antibacterial effect 100% formulations produced zones of inhibitions against E. colip-value = 0.001. The mean zone of inhibition produced by F4 was greatest among all at 26.44 ± 0.37 mm (mean ± S.D). The F4 formulation produced a maximum percentage dissolution, permeation, and flux of 86.35 ± 0.576, 55.29 ± 0.127%, and 0.5532 ug/cm²/min, respectively. Conclusions: The present study therefore, suggests the use of S. acmella extract and olive oil containing emulgel for treating bacterial skin infections. Full article

Strychnine (STCN) has demonstrated an exceptional anticancer effect against various cancers. However, the STCN clinical utility has been hampered by its low water solubility, restricted therapeutic window, short half-life, and significant toxicity. The objective of this investigation was to design and optimize a formulation of strychnine-loaded transliposomes (STCN–TLs) for dermal administration of STCN to treat skin cancer. The formulations of STCN–TL were examined in terms of vesicle size (VS), polydispersity index (PDI), entrapment efficiency (EE), and in vitro delivery. The improved STCN–TL formulation exhibited VS, PDI, EE, and in vitro delivery of 101.5 ± 2.14 nm, 0.218 ± 0.12, 81.74 ± 1.43%, and 85.39 ± 2.33%, respectively. In an ex vivo penetration, the created STCN–TL formulation demonstrated a 2.5-fold increase in permeability compared to the STCN solution. CLSM pictures of skin (rat) revealed that the rhodamine B-loaded transliposome preparation penetrated deeper than the rhodamine B hydroalcoholic mixture. Additionally, rat skin managed with STCN–TL nanogel exhibited a significant increase in C_{skin max} and AUC_0-8 compared to rat skin treated with traditional STCN gel. The findings demonstrated that the transliposome preparation might be a suitable nanocarrier for the cutaneous distribution of STCN in the amelioration of skin cancer. Full article

The current research aims to create a sol-gel-based nanocarrier containing terbinafine formulated for transdermal delivery of the drug into the skin. Sol-gel-based nanocarriers were prepared via the cold method using poloxamer-188, poloxamer-407, and distilled water. The prepared formulation was examined for pH, gelation temperature, Fourier transform infrared spectrophotometer (FTIR) analysis, thermal stability analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis, zeta potential, and anti-microbial activity. The in-vitro drug release study of F1 was found to be 94%, which showed greater drug release as compared to F2 and F3. The pH of the formulation was found to be within the range applicable to the skin. The gelation temperature was detected at 28 °C. The SEM images of formulations have spotted various particles well-segregated from each other. Analysis of formulations showed a mean globule size diameter of 428 nm, zeta potential values of 0.04 mV, refractive index (1.329), and viscosity (5.94 cP). FTIR analysis confirmed various functional groups’ presence in the prepared formulation. Thermal analysis has confirmed the stability of the drug within the prepared formulation. The growth of inhibition was found to be 79.2% in 60 min, which revealed that the prepared formulation has shown good permeation from the membrane. Hence, the sol-gel-based nanocarrier formulation of terbinafine was successfully developed and evaluated. Full article

In this study, we report the fabrication and characterization of self-healing and shape-memorable hydrogels, the mechanical properties of which can be tuned via post-polymerization crosslinking. These hydrogels were constructed from a thermo-responsive poly(N-acryloyl glycinamide) (NAGAm) copolymer containing N-acryloyl serine methyl ester (NASMe) units (5 mol%) that were readily synthesized via conventional radical copolymerization. This transparent and free-standing hydrogel is produced via multiple hydrogen bonds between PNAGAm chains by simply dissolving the polymer in water at a high temperature (~90 °C) and then cooling it. This hydrogel exhibited moldability and self-healing properties. The post-polymerization crosslinking of the amino acid-derived vinyl copolymer network with glutaraldehyde, which acts as a crosslinker between the hydroxy groups of the NASMe units, tuned mechanical properties such as viscoelasticity and tensile strength. The optimal crosslinker concentration efficiently improved the viscoelasticity. Moreover, these hydrogels exhibited shape fixation (~60%)/memory (~100%) behavior owing to the reversible thermo-responsiveness (upper critical solution temperature-type) of the PNAGAm units. Our multifunctional hydrogel, with moldable, self-healing, mechanical tunability via post-polymerization crosslinking, and shape-memorable properties, has considerable potential for applications in engineering and biomedical materials. Full article

Any thermoset resin’s processing properties and end-use performance are heavily influenced by the gel time. The complicated viscosity of resin as a function of temperature is investigated in this work, with a particular emphasis on identifying the gel point and comprehending polymerization. Rheology studies carried out using a plate-plate controlled stress rheometer under isothermal conditions were used to compare three experimental techniques for figuring out an epoxy resin’s gel point. We also look at the basic modifications that take place during polymerization. We verify the reliability of the three strategies by including Principal Component Analysis (PCA), an unsupervised machine learning methodology. PCA assists in uncovering hidden connections between these methods and various affecting factors. PCA serves a dual role in our study, confirming method validity and identifying patterns. It sheds light on the intricate relationships between experimental techniques and material properties. This concise study expands our understanding of resin behavior and provides insights that are essential for optimizing resin-based processes in a variety of industrial applications. Full article

Toxic metal ions present in industrial waste, such as Pb(II), introduce deleterious effects on the environment. Though the adsorptive removal of Pb(II) is widely reported, there is a dearth of research on the suitable utilization and disposal of the Pb(II)-adsorbed adsorbent. In this work, an MXene-grafted terpolymer (MXTP) hydrogel has been designed for the adsorption of Pb(II) under ambient conditions of pH and temperature. The hydrogel MXTP was synthesized by facile one-pot polymerization in aqueous solvent, and the detailed structural characterization of terpolymer (TP), MXTP, and Pb(II)-loaded MXTP, i.e., Pb(II)-MXTP, was carried out by a combination of proton nuclear magnetic resonance (¹H NMR), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometric (XRD), thermogravimetric/differential thermogravimetric (TG/ DTG), and field emission scanning electron microscopic (FESEM) analyses. The specific capacitance and conductivities of Pb(II)-MXTP were studied with cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS), which unambiguously indicate successful post-adsorption application. The specific capacitance of MXTP decreased after Pb(II) adsorption, whereas the conductivity increased significantly after Pb(II) adsorption, showing that MXTP can be successfully deployed as a solid electrolyte/anode after Pb(II) adsorption. This study covers the synthesis of a novel MXene-grafted terpolymer hydrogel for adsorptive exclusion of Pb(II) and assessment of the as-adsorbed Pb(II)-loaded hydrogel as a solid electrolyte/anode material and is the first demonstration of such post-adsorptive application. Full article

Surgical site infections (SSIs) are among the most frequent healthcare-associated infections, resulting in high morbidity, mortality, and cost. While correct hygiene measures and prophylactic antibiotics are effective in preventing SSIs, even in modern healthcare settings where recommended guidelines are strictly followed, SSIs persist as a considerable problem that has proven hard to solve. Surgical procedures involving the implantation of foreign bodies are particularly problematic due to the ability of microorganisms to adhere to and colonize the implanted material and form resilient biofilms. In these cases, SSIs may develop even months after implantation and can be difficult to treat once established. Locally applied antibiotics or specifically engineered implant materials with built-in antibiotic-release properties may prevent these complications and, ultimately, require fewer antibiotics compared to those that are systemically administered. In this study, we demonstrated an antimicrobial material concept with intended use in artificial vascular grafts. The material is a silicone–hydrogel interpenetrating polymer network developed earlier for drug-release catheters. In this study, we designed the material for permanent implantation and tested the drug-loading and drug-release properties of the material to prevent the growth of a typical causative pathogen of SSIs, Staphylococcus aureus. The novelty of this study is demonstrated through the antimicrobial properties of the material in vitro after loading it with an advantageous combination, minocycline and rifampicin, which subsequently showed superiority over the state-of-the-art (Propaten) artificial graft material in a large-animal study, using a novel porcine tissue-implantation model. Full article

Fixed-bed columns packed with chitosan-magnetite (ChM) hydrogel and chitosan (Ch) hydrogel were used for the removal of arsenate ions from aqueous solutions at a pH of 7.0. The effect of flow rate (13, 20, and 25 mL/h), height of the columns (13 and 33 cm), and initial arsenate concentration (2, 5 and 10 mg/L) on the column’s efficiency for the removal of As(V) is reported. The maximum adsorption capacity (q_b), obtained before the allowed concentration of contaminant is exceeded, the adsorption capacity (q_e) when the column is exhausted, and the mass transfer zone were determined. With this information, the efficiency of the column was calculated, which is given by the H_L/H_LUB ratio. The higher this ratio, the higher the efficiency of the column. The highest efficiency and the highest uptake capacity value at breakthrough point were obtained when using the lower flow rate, lower initial arsenate concentration, and longer bed length. When 33 cm-high columns were fed with a 10 mg As(V)/L solution at 13 mL/h, the maximum uptake capacity values at exhaustion obtained for Ch and ChM were 1.24 and 3.84 mg/g, respectively. A pH increase of the solution at the column’s exit was observed and is attributed to the proton transfer from the aqueous solution to the amino and hydroxyl groups of chitosan. The incorporation of magnetite into Ch hydrogels significantly increases their capacity to remove As(V) due to the formation of complexes between arsenic and the magnetite surface. Experimental data were fitted to the Thomas model, the Yoon–Nelson model and the Bohart–Adams model using non-linear regression analysis. Full article

Increased prevalence of cardiovascular disease and potentially life-threatening complications of myocardial infarction (MI) has led to emerging therapeutic approaches focusing on myocardial regeneration and restoration of physiologic function following infarction. Extracellular vesicle (EV) technology has gained attention owing to the biological potential to modulate cellular immune responses and promote the repair of damaged tissue. Also, EVs are involved in local and distant cellular communication following damage and play an important role in initiating the repair process. Vesicles derived from stem cells and cardiomyocytes (CM) are of particular interest due to their ability to promote cell growth, proliferation, and angiogenesis following MI. Although a promising candidate for myocardial repair, EV technology is limited by the short retention time of vesicles and rapid elimination by the body. There have been several successful attempts to address this shortcoming, which includes hydrogel technology for the sustained bioavailability of EVs. This review discusses and summarizes current understanding regarding EV technology in the context of myocardial repair. Full article

Under certain conditions, ultrasonic treatment of certain foods and ingredients can contribute to the appearance of an extraneous odor, which is not usual for them, especially in fat-containing products. Since the food sector uses high-intensity ultrasound to control the crystallization of fats, the development of foreign smells and secondary fat oxidation products may impact the quality and safety of such items. In this work, we studied the volatile compounds’ profiles of oleogels structured with individual fractions of beeswax using ultrasonic treatment. For this work, six samples of oleogels were obtained. Sunflower oil was used as a fatty base, and three fractions of beeswax were used as gelators: hydrocarbon fraction (>99%), monoester fraction (>95%), and a mixture fraction of wax di- and triesters (10.1%), free fatty acids (40.1%), and free fatty alcohols (49.8%). The influence of ultrasonic treatment on the properties of oleogels was assessed using light microscopy in polarized light, texture analysis, gas chromatography with flame ionization, and mass spectrometric detection. Ultrasonic treatment affected the crystallization of oleogels and led to the formation of smaller crystals. At the same time, sonication led to both an increase and a decrease in the firmness of oleogels, depending on the composition of the gelator. As regards volatile compounds, a total of 121 fragrant substances were identified in all samples, including such groups as alkanes, alkenes, alkadienes, alkynes, alkadiynes, alcohols, ketones, aldehydes, terpenes, alkyl alkane, and alkyl benzene derivatives. Ultrasonic treatment caused formation of new volatile unsaturated compounds. Some of them are known to have an unpleasant odor and thus might be responsible for the extraneous odor formation in studied fatty systems. Those were mainly (E)-2-octene, 1-heptene, 1,3-butadiene, and 1,3-octadiene in all oleogel samples. Sonicated samples B and C additionally had but-1-en-3-yne, pentenyne, and 1,3-butadiyne, whose odor can also be characterized as extraneous and distasteful. Several volatile compounds, supposed to be products of lipid oxidation, were also identified. Here we assume a reasonable approach is needed when selecting sonication conditions to prevent undesirable taste and flavor in oleogels and oleogel-based food products. Full article

The usage of a highly efficient, low-cost, and sustainable adsorbent material as an industrial wastewater treatment technique is required. Herein, the usage of the novel, fully sustainable tannin-5-(hydroxymethyl)furfural (TH) aerogels, generated via a water-based sol–gel process, as compatible biosorbent materials is presented. In particular, this study focusses on the surface modification of the tannin biosorbent with carboxyl or amino functional groups, which, hence, alters the accessible adsorption sites, resulting in increased adsorption capacity, as well as investigating the optimal pH conditions for the adsorption process. Precisely, highest adsorption capacities are acquired for the metal cations and cationic dye in an alkaline aqueous environment using a carboxyl-functionalized tannin biosorbent, whereas the anionic dye requires an acidic environment using an amino-functionalized tannin biosorbent. Under these determined optimal conditions, the maximum monolayer adsorption capacity of the tannin biosorbent ensues in the following order: Cu²⁺ > RB > Zn²⁺ > MO, with 500, 244, 192, 131 mg g⁻¹, respectively, indicating comparable or even superior adsorption capacities compared to conventional activated carbons or silica adsorbents. Thus, these functionalized, fully sustainable, inexpensive tannin biosorbent materials, that feature high porosity and high specific surface areas, are ideal industrial candidates for the versatile adsorption process from contaminated (heavy) metal or dye solutions. Full article

Balsam poplar buds have been used for wound healing and treating irritated skin in traditional medicine. Balsam poplar buds extracts exhibit anti-inflammatory, antioxidant, and antimicrobial effects. In recent years, scientific research has begun to validate some of these traditional uses, leading to an increased interest in balsam poplar buds as a potential source of natural remedies in modern medicine. The study aims to simulate semi-solid pharmaceutical forms with balsam poplar buds extract and evaluate their quality through biopharmaceutical research. The active compounds identified in Lithuanian poplar buds were p-coumaric acid, cinnamic acid, caffeic acid, galangin, pinocembrin, pinobanksin, and salicin. In gels, pH values ranged from 5.85 ± 0.05 to 5.95 ± 0.07. The determined pH values of emulgels ranged from 5.13 ± 0.05 to 5.66 ± 0.15. After 6 h, the release of active compounds from gels and emulgels ranged from 47.40 ± 2.41% to 71.17 ± 3.54. p-coumaric acid dominates in the balsam poplar buds extracts. The pH values of the prepared sem-solid pharmaceutical forms are suitable for use on the skin. The viscosity of the formulations depends on the amount of gelling agent. All formulations showed antioxidant activity. It is relevant to conduct a more extensive study on the influence of the chosen carrier on the release of active compounds from semi-solid formulations with an extract of balsam poplar buds. Full article

Structure and reversibility of cross-link junctions play pivotal roles in determining the nature of thermoreversible gelation and dynamic mechanical properties of the produced polymer networks. We attempt to theoretically explore new types of sol–gel transitions with mechanical sharpness by allowing cross-links to grow without upper bound. We consider thermoreversible gelation of the primary molecules R{A${}_f$} carrying the number f of low molecular weight functional groups (gelators) A. Gelators A are assumed to form supramolecular assemblies. Some examples are: telechelic polymers ($f=2$) carrying $\pi$–$\pi$ stacking benzene derivatives at their both ends, and trifunctional star molecules ($f=3$) bearing multiple hydrogen-bonding gelators. The sol–gel transition of the primary molecules becomes sharper with the cooperativity parameter of the stepwise linear growth of the cross-links. There is a polymerization transition (crossover without singularity) of the junctions in the postgel region after the gel point is passed. If the gelator A tends to form supramolecular rings competitively with linear chains, there is another phase transition in the deep postgel region where the average molecular weight of the rings becomes infinite (Bose–Einstein condensation of rings). As a typical example of binary cross-links where gelators A and B form mixed junctions, we specifically consider metal-coordinated binding of ligands A by metal ions B. Two types of multi-nuclear supramolecular complexes are studied: (i) linear stacking (ladder) of the sandwich A${}_2$B units, and (ii) linear train of egg-box A${}_4$B units. To find the strategy towards experimental realization of supramolecular cross-links, the average molecular weight, the gel fraction, the average length of the cross-link junctions are numerically calculated for all of these models as functions of the functionality f, the concentration of the solute molecules, and the temperature. Potential candidates for the realization of these new types of thermoreversible gelation are discussed. Full article

Polybenzoxazine (PBZ) exhibits excellent heat resistance, and PBZ derivatives have been designed and synthesized to achieve high performance. However, the application range of PBZ is limited by the strong interactions between molecular chains and its low solubility in organic solvents, thereby limiting its processability. This study focused on the benzoxazine structure as the molecular backbone of new hydrogel materials that can be applied as electrolyte materials and prepared functional gel materials. Here, we prepared hydrogels by water-solubilizing PBZ derivatives, which typically exhibit low solubility in organic solvents. Although studies on the hydrophilization of PBZ and its complexation with hydrophilic polymers have been conducted, no studies have been performed on the hydrogelation of PBZ. First, the phenol in the organic solvent-insoluble PBZ thin film obtained after the thermal ring-opening polymerization of the monomer was transformed into sodium phenoxide by immersion in a NaOH aqueous solution to water-solubilize it and obtain a hydrogel thin film. Although the hydrogel thin film exhibited low mechanical strength, a free-standing hydrogel film with improved strength was obtained through the double network gelation method with an acrylamide monomer system. The physical properties of the polymer composite hydrogel thin film were evaluated. The ionic conductivity of the hydrogel thin films was in the order of 10⁻⁴ S cm⁻¹, indicating the potential of PBZ as an electrolyte hydrogel material. However, improving its ionic conductivity will be undertaken in future studies. Full article

The present study aimed to prepare, characterize, and evaluate a thermo-responsive sol–gel for intranasal delivery of lamotrigine (LTG), which was designed for sustained drug delivery to treat epilepsy. LTG sol–gel was prepared using the cold method by changing the concentrations of poloxamer 407 and poloxamer 188, which were used as thermo-reversible polymers. The optimized formulations of sol–gel were analyzed for clarity, pH, viscosity, gelation temperature, gelation time, spreadability, drug content, in vitro drug release studies, ex vivo permeation studies, and in vivo toxicological studies. FTIR, XRD, and DSC were performed to determine the thermal stability of the drug and polymers. The prepared formulations had a clear appearance in sol form; they were liquid at room temperature and became gel at temperatures between 31 °C and 36 °C. The pH was within the range of the nasal pH, between 6.2 and 6.4. The drug content was found to be between 92% and 94%. In vitro drug release studies indicated that the formulations released up to 92% of the drug within 24 h. The FTIR, DSC, and XRD analyses showed no interaction between the drug and the polymer. A short-term stability study indicated that the formulation was stable at room temperature and at 4–8 °C. There was a slight increase in viscosity at room temperature, which may be due to the evaporation of the vehicle. A histological study indicated that there were no signs of toxicity seen in vital organs, such as the brain, kidney, liver, heart, and spleen. It can be concluded from the above results that the prepared intranasal sol–gel for the delivery of LTG is safe for direct nose-to-brain delivery to overcome the first-pass effect and thus enhance bioavailability. It can be considered an effective alternative to conventional drug delivery for the treatment of epilepsy. Full article

This study aimed to develop a film-forming gel containing honey aromatic water (HW) and royal jelly (RJ) for cosmetic applications as a facial peel-off mask. HW, which is industrial waste from the water-reduction process of honey, was sterilized by autoclaving and filtration through a 0.22 µm membrane. The film-forming gels were developed using various types of film-forming polymers, including polyvinyl alcohol (PVA 117), carboxymethyl cellulose (CMC), and hydroxyethyl cellulose (HEC). The gel formulations were characterized in terms of their external appearance, viscosity, pH, and drying time, whereas the films generated were characterized by a texture analyzer, microscopic investigation, Fourier transform infrared, and an X-ray diffractometer. The findings highlighted that HW has short storage shelf life due to microbial contamination. Sterilizations were required before further product development. The film-forming gel was created by using the combination of PVA 117, CMC, and HEC. HW and RJ were successfully incorporated into the film-forming gel. However, HW resulted in a decrease in the gel viscosity and mechanical properties of its film. Interestingly, the drying time was dramatically decreased, which would be more desirable for its use as a peel-off mask. Furthermore, incorporation of royal jelly enhanced the viscosity of the gels as well as improved the mechanical properties of the film. No effect on the chemical and crystal structure of the films was detected after the incorporation. Therefore, the film-forming gels containing HW and RJ, possessing aesthetic attributes that extended to both the gels themselves and the resultant films, were suitable for use as a peel-off mask. Full article

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal–organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal–ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes. Full article

Silica aerogels are high-performance thermal insulation materials that can be used to provide unique solutions in the envelopes of buildings when space is limited. They are most often applied in historic buildings due to thin insulation thicknesses and since they are compatible with historic structures. In 2021, the first Aerogel Architecture Award was held at Empa in Switzerland in order to collect, evaluate and award outstanding uses of this relatively new building material. From the submitted projects, three were selected for an award by an expert jury. They showcased applications in which heritage protection and the conservation of a building’s character and expression were reconciled with significant improvements in the energy efficiency of the building. The submissions also showed that a broader communication of these types of solutions is important in order to provide more information and security to planners and heritage offices and to facilitate the application of these materials in the future so that they can contribute to the protection of cultural heritage and reductions in the operational and embodied emissions of our building stock by extending the life expectancy and energy efficiency of existing buildings. Full article

Autologous fat grafting is hampered by unpredictable outcomes due to high tissue resorption. Hydrogels based on enzymatically pretreated tunicate nanocellulose (ETC) and alginate (ALG) are biocompatible, safe, and present physiochemical properties capable of promoting cell survival. Here, we compared in situ and ex situ crosslinking of ETC/ALG hydrogels combined with lipoaspirate human adipose tissue (LAT) to generate an injectable formulation capable of retaining dimensional stability in vivo. We performed in situ crosslinking using two different approaches; inducing Ca²⁺ release from CaCO₃ microparticles (CMPs) and physiologically available Ca²⁺ in vivo. Additionally, we generated ex situ-crosslinked, 3D-bioprinted hydrogel-fat grafts. We found that in vitro optimization generated a CMP-crosslinking system with comparable stiffness to ex situ-crosslinked gels. Comparison of outcomes following in vivo injection of each respective crosslinked hydrogel revealed that after 30 days, in situ crosslinking generated fat grafts with less shape retention than 3D-bioprinted constructs that had undergone ex situ crosslinking. However, CMP addition improved fat-cell distribution and cell survival relative to grafts dependent on physiological Ca²⁺ alone. These findings suggested that in situ crosslinking using CMP might promote the dimensional stability of injectable fat-hydrogel grafts, although 3D bioprinting with ex situ crosslinking more effectively ensured proper shape stability in vivo. Full article

Incisional hernia is a frequent complication after abdominal surgery. A previous study on rats evaluated the use of a Pectin–Honey Hydrogel (PHH)-coated polypropylene (PP) mesh for the healing of acute hernias. However, there are no studies investigating the use of PHH in association with PP mesh in chronic contaminated hernia. The aims of this study are to assess the effectiveness of PHH in promoting abdominal hernia repaired with PP mesh and in counteracting infection. Twenty Sprague Dawley male rats were enrolled and a full thickness defect was made in the abdominal wall. The defect was repaired after 28 days using a PP mesh, and a culture medium (Tryptone Soy Broth, Oxoid) was spread onto the mesh to contaminate wounds in both groups. The rats were randomly assigned to a treated or untreated group. In the treated group, a PHH was applied on the mesh before skin closure. At euthanasia—14 days after surgery—macroscopical, microbiological and histopathological evaluations were performed, with a score attributed for signs of inflammation. An immunohistochemical investigation against COX-2 was also performed. Adhesions were more severe (p = 0.0014) and extended (p = 0.0021) in the untreated group. Bacteriological results were not significantly different between groups. Both groups showed moderate to severe values (score > 2) in terms of reparative and inflammatory reactions at histopathological levels. The use of PHH in association with PP mesh could reduce adhesion formation, extension and severity compared to PP mesh alone. No differences in terms of wound healing, contamination and grade of inflammation were reported between groups. Full article