Gels | Special Issue : Physical and Mechanical Properties of Polymer Gels

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11 pages, 740 KiB

Open AccessArticle

Formulation of Entandrophragma utile into an Herbal Emulgel for the Management of Inflammation

by Adeola Tawakalitu Kola-Mustapha, Haneefat Folashade Ibraheem, Suleiman Taiwo, Ismail O. Ishola, Sukurat Olasumbo Usman and Yusuf Oluwagbenga Ghazali

Gels 2023, 9(12), 956; https://doi.org/10.3390/gels9120956 - 06 Dec 2023

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Abstract

Introduction: Globally, the incidence of inflammation and inflammatory disorders has continued to rise at an alarming rate. Entandrophragma utile is a species of flowering plant widely distributed in Africa and has been used for the management of sickle cell disease, rheumatism, ocular inflammation, [...] Read more.

Introduction: Globally, the incidence of inflammation and inflammatory disorders has continued to rise at an alarming rate. Entandrophragma utile is a species of flowering plant widely distributed in Africa and has been used for the management of sickle cell disease, rheumatism, ocular inflammation, duodenal and stomach ulcers. This research aims to formulate and evaluate an anti-inflammatory herbal emulgel using an extract from Entandrophragma utile stem bark (EUB). Method: Using a carrageenan-induced paw oedema model, the anti-inflammatory efficacy of EUB the extract was assessed. The formulated Entandrophragma utile emulgels (EUE) were characterized, and their anti-inflammatory activity was demonstrated, by utilizing diclofenac emulgel-treated rats with complete Freund’s adjuvant (CFA)-induced arthritis model as the positive control group. Results: The emulgels formulated had characterization results within acceptable ranges; pH (4.25–5.80), viscosity (418.9–112.8 mPas), spreadability (25.00–31.82 gcm/s), extrudability (30.86–51.02 g/cm²), and a swelling index of (30–60%). The emulgel produced a concentration-dependent inflammatory inhibition with a peak effect (117.97%) at the end of the 4th week which was comparable to that of commercial diclofenac (127.19%). The phytochemical analysis led to the identification of saponins, flavonoids, phenols, and tannins as active secondary metabolites. Conclusions: The stem bark extract of E. utile possessed noteworthy (p < 0.05) reduction in inflammation in comparison to diclofenac and its emulgel formulation showed enormous potential for treating inflammation and pain. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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17 pages, 2115 KiB

Open AccessArticle

The Formulation and Evaluation of Melaleuca alternifolia Cheel and Cymbopogon flexuosus Linn Essential Oils Emulgel for the Treatment of Vulvovaginal Candidiasis

by Adeola Tawakalitu Kola-Mustapha, Miracle Halima Aliu, Ronke Hadiyat Bello, Oluwakorede Joshua Adedeji and Yusuf Oluwagbenga Ghazali

Gels 2023, 9(12), 949; https://doi.org/10.3390/gels9120949 - 03 Dec 2023

Viewed by 1105

Abstract

The global concern regarding the occurrence of antifungal resistance to synthetic conventional azoles used for treating vulvovaginal candidiasis, along with the associated side effects, is significant. Consequently, the pursuit for substitutes such as natural therapies has ensued. Essential oils, derived from plants, have [...] Read more.

The global concern regarding the occurrence of antifungal resistance to synthetic conventional azoles used for treating vulvovaginal candidiasis, along with the associated side effects, is significant. Consequently, the pursuit for substitutes such as natural therapies has ensued. Essential oils, derived from plants, have been extensively researched and found to possess antibacterial and antifungal properties. This study aimed to assess the antifungal efficacy of two essential oils, both alone and in combination, against Candida albicans. Essential oils were formulated into an emulgel separately and as combinations. The essential oils of Melaleuca alternifolia and Cymbopogon flexuosus were used in this study. The resulting emulgel formulations were characterized for their antifungal activity against Candida albicans. Physiochemical properties such as pH, viscosity, and appearance were also determined. The prepared emulgels were thereafter observed for stability over a period of 1 month. The MIC of Melaleuca alternifolia was seen to be 50 µL/mL while Cymbopogon flexuous was seen to be more potent at 25 µL/mL against C. albicans exhibiting strong synergistic effect at 0.4. The emulgel formed was white in color, smooth on skin, and had the odor of the essential oils, which is sweet to the nose. The pH of the formulations with the essential oils were acidic in the range of 3.70–3.83, making them suitable for vagina application. The emulgels had viscosities ranging from 4417.6 to 8968.7 mPas, owing to the thickness of the essential oils contained. The emulgel formulation with the combination of essential oils was more potent that the two with individual essential oils; furthermore, the one with Cymbopogon flexuous was more potent than the one with Melaleuca alternifolia. Based on the properties of the formulated emulgels and their activity against the test organism, the preparations have significant potential in the management of vulvovaginal candidiasis. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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13 pages, 6067 KiB

Open AccessArticle

Tough, Stretchable, and Thermoresponsive Smart Hydrogels

by Yi Luo, Werner Pauer and Gerrit A. Luinstra

Gels 2023, 9(9), 695; https://doi.org/10.3390/gels9090695 - 28 Aug 2023

Cited by 1 | Viewed by 923

Abstract

Self-healing, thermoresponsive hydrogels with a triple network (TN) were obtained by copolymerizing N-isopropyl acryl amide (NiPAAm) with polyvinyl alkohol (PVA) functionalized with methacrylic acid and N,N′-methylene bis(acryl amide) crosslinker in the presence of low amounts (<1 wt.%) of tannic acid (TA). The final [...] Read more.

Self-healing, thermoresponsive hydrogels with a triple network (TN) were obtained by copolymerizing N-isopropyl acryl amide (NiPAAm) with polyvinyl alkohol (PVA) functionalized with methacrylic acid and N,N′-methylene bis(acryl amide) crosslinker in the presence of low amounts (<1 wt.%) of tannic acid (TA). The final gels were obtained by crystalizing the PVA in a freeze-thaw procedure. XRD, DCS, and SEM imaging indicate that the crystallinity is lower and the size of the PVA crystals is smaller at higher TA concentrations. A gel with 0.5 wt.% TA has an elongation at a break of 880% at a tension of 1.39 MPa. It has the best self-healing efficiency of 81% after cutting and losing the chemical network. Step-sweep strain experiments show that the gel has thixotropic properties, which are related to the TA/PVA part of the triple network. The low amount of TA leaves the gel with good thermal responsiveness (equilibrium swelling ratio of 13.3). Swelling-deswelling loop tests show enhanced dimensional robustness of the hydrogel, with a substantial constancy after two cycles. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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16 pages, 2192 KiB

Open AccessArticle

Characteristics of a Lipid Hydrogel and Bigel as Matrices for Ascorbic Acid Stabilization

by Noèlia Loza-Rodríguez, Aina Millán-Sánchez and Olga López

Gels 2023, 9(8), 649; https://doi.org/10.3390/gels9080649 - 11 Aug 2023

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Abstract

Ascorbic acid (AA) has many health benefits, including immune and cardiovascular deficiency protection, prenatal problems, and skin diseases. Unfortunately, AA is easily oxidized and has limited bioavailability. Thus, the development of formulations that stabilize and enhance the efficacy of AA is a challenge. [...] Read more.

Ascorbic acid (AA) has many health benefits, including immune and cardiovascular deficiency protection, prenatal problems, and skin diseases. Unfortunately, AA is easily oxidized and has limited bioavailability. Thus, the development of formulations that stabilize and enhance the efficacy of AA is a challenge. In this study, 4% AA was encapsulated in two recently developed gels, a hydrogel and a bigel. The hydrogel was formed exclusively with lipids and water, and the bigel was a combination of the hydrogel with an oleogel formed with olive oil and beeswax. The effect of AA in gel microstructures was determined using X-ray scattering, rheology, and texture analysis. Additionally, the capacity of these materials to protect AA from degradation upon temperature and sunlight was studied. Results showed that the incorporation of AA into both materials did not affect their microstructure. Moreover, hydrogel-protected AA showed only 2% degradation after three months at 8 °C, while in aqueous solution, it degraded by 12%. Regarding sunlight, bigel showed a good shielding effect, exhibiting only 2% AA degradation after 22 h of exposure, whereas in aqueous solution, AA degraded by 10%. These results suggest that both proposed gels could be used in biomedical applications and the field of food. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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12 pages, 680 KiB

Open AccessArticle

“Gloppiness” Phenomena and a Computer Vision Method to Quantify It

by Shijian Wu, Mark Mintel, Baran Teoman, Stephanie Jensen and Andrei Potanin

Gels 2023, 9(7), 532; https://doi.org/10.3390/gels9070532 - 30 Jun 2023

Viewed by 887

Abstract

In this study, we present a rapid, cost-effective Python-driven computer vision approach to quantify the prevalent “gloppiness” phenomenon observed in complex fluids and gels. We discovered that rheology measurements obtained from commercial shear rheometers do show some hints, but do not exhibit a [...] Read more.

In this study, we present a rapid, cost-effective Python-driven computer vision approach to quantify the prevalent “gloppiness” phenomenon observed in complex fluids and gels. We discovered that rheology measurements obtained from commercial shear rheometers do show some hints, but do not exhibit a strong correlation with the extent of “gloppiness”. To measure the “gloppiness” level of laboratory-produced shower gel samples, we employed the rupture time of jetting flow and found a significant correlation with data gathered from the technical insight panelist team. While fully comprehending the “gloppiness” phenomenon remains a complex challenge, the Python-based computer vision technique utilizing jetting flow offers a promising, efficient, and affordable solution for assessing the degree of “gloppiness” for commercial liquid and gel products in the industry. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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12 pages, 2956 KiB

Open AccessArticle

Mechanical and Physical Properties of an Experimental Chemically and Green-Nano Improved Dental Alginate after Proven Antimicrobial Potentials

by Lamia Singer and Christoph Bourauel

Gels 2023, 9(5), 429; https://doi.org/10.3390/gels9050429 - 21 May 2023

Cited by 3 | Viewed by 1505

Abstract

Objectives: Impression materials could be a source of cross-contamination due to the presence of microorganisms from blood and saliva inside the oral cavity. Nevertheless, routinely performed post-setting disinfection could compromise the dimensional accuracy and other mechanical properties of alginates. Thus, this study aimed [...] Read more.

Objectives: Impression materials could be a source of cross-contamination due to the presence of microorganisms from blood and saliva inside the oral cavity. Nevertheless, routinely performed post-setting disinfection could compromise the dimensional accuracy and other mechanical properties of alginates. Thus, this study aimed to evaluate detail reproduction, dimensional accuracy, tear strength, and elastic recovery of new experimentally prepared self-disinfecting dental alginates. Methods: Two antimicrobial-modified dental alginate groups were prepared by mixing alginate powder with 0.2% silver nitrate (AgNO₃ group) and a 0.2% chlorohexidine solution (CHX group) instead of pure water. Moreover, a third modified group was examined by the extraction of Boswellia sacra (BS) oleoresin using water. The extract was used to reduce silver nitrate to form silver nanoparticles (AgNPs), and the mixture was used as well in dental alginate preparation (BS + AgNP group). Dimensional accuracy and detail reproduction were examined as per the ISO 1563 standard guidelines. Specimens were prepared using a metallic mold engraved with three parallel vertical lines 20, 50, and 75 µm wide. Detail reproduction was evaluated by checking the reproducibility of the 50 µm line using a light microscope. Dimensional accuracy was assessed by measuring the change in length between defined reference points. Elastic recovery was measured according to ISO 1563:1990, in which specimens were gradually loaded and then the load was released to allow for recovery from the deformation. Tear strength was evaluated using a material testing machine until failure at a crosshead speed of 500 mm/min. Results: The recorded dimensional changes between all tested groups were insignificantly different and within the reported acceptable values (between 0.037–0.067 mm). For tear strength, there were statistically significant differences between all tested groups. Groups modified with CHX (1.17 ± 0.26 N/mm) and BS + AgNPs (1.11 ± 0.24 N/mm) showed higher tear strength values compared to the control (0.86 ± 0.23 N/mm) but were insignificant from AgNO₃ (0.94 ± 0.17 N/mm). All tested groups showed elastic recovery values that met both the ISO standard and ADA specifications for elastic impression materials and tear strength values within the acceptable documented ranges. Discussion: The CHX, silver nitrate, and green-synthesized silver nanoparticles could be promising, inexpensive alternatives for the preparation of a self-disinfecting alginate impression material without affecting its performance. Green synthesis of metal nanoparticles could be a very safe, efficient, and nontoxic method, with the advantage of having a synergistic effect between metal ions and active chemical constituents of plant extracts. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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33 pages, 16921 KiB

Open AccessArticle

Colloidal and Sedimentation Behavior of Kaolinite Suspension in Presence of Non-Ionic Polyacrylamide (PAM)

by Aref Abbasi Moud

Gels 2022, 8(12), 807; https://doi.org/10.3390/gels8120807 - 09 Dec 2022

Cited by 4 | Viewed by 1484

Abstract

Colloidal behavior of kaolinite particles in water was investigated in this manuscript, without and with the addition of a polymer flocculant (non-anionic polyacrylamide (PAM)), using diverse imaging techniques in addition to LUMisizer. The addition of PAM was found to be causing the formation [...] Read more.

Colloidal behavior of kaolinite particles in water was investigated in this manuscript, without and with the addition of a polymer flocculant (non-anionic polyacrylamide (PAM)), using diverse imaging techniques in addition to LUMisizer. The addition of PAM was found to be causing the formation of bridges among particles thus increasing their settling rates to the bottom of the container. To assess the size of flocs and the potential morphology of PAM around particles and their clusters, the state of flocs formation and polymer distribution was analyzed through various microscopical techniques, namely scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM results revealed that, in the absence of PAM, the floc structure of the sediment was loose and irregularly distributed, while the presence of PAM made the sediment structures greatly denser. Later, using LUMisizer, dynamic light scattering (DLS) and the zeta potential of kaolinite, sedimentation, and colloidal behavior of suspension came under scrutiny. Using LUMisizer, the maximum packing and settling rates of the particles were experimentally obtained as roughly 44 vol%; settling rates were estimated in 63–352 µm/s when centrifugal force varied and, using maximum packing values, compressive yield was estimated to vary between 48–94 kPa. The results of this study are instructive in choosing appropriate polymers and operating conditions to settle clay minerals in tailing ponds. Additionally, the maximum packing of kaolinite particles was simulated with spherical particles with varied polydispersity to connect DLS data to the maximum packing values obtained using LUMisizer; the little discrepancy between simulation and experimental values was found to be encouraging. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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21 pages, 21697 KiB

Open AccessArticle

Jetting Dynamics of Burning Gel Fuel Droplets

by Janmejai Sharma, Ankur Miglani, Jerin John, Purushothaman Nandagopalan, Javed Shaikh and Pavan Kumar Kankar

Gels 2022, 8(12), 781; https://doi.org/10.3390/gels8120781 - 29 Nov 2022

Cited by 2 | Viewed by 1397

Abstract

Jetting in burning gel fuel droplets is an important process which, in addition to pure vaporization, enables the convective transport of unreacted fuel vapors from the droplet interior to the flame envelope. This aids in accelerating the fuel efflux and enhancing the mixing [...] Read more.

Jetting in burning gel fuel droplets is an important process which, in addition to pure vaporization, enables the convective transport of unreacted fuel vapors from the droplet interior to the flame envelope. This aids in accelerating the fuel efflux and enhancing the mixing of the gas phase, which improves the droplet burn rates. In this study, Schlieren imaging was used to characterize different jetting dynamics that govern the combustion behavior of organic-gellant-laden ethanol gel fuel droplets. To initiate jetting, the gellant shell of the burning gel fuel droplet was subjected to either oscillatory bursting or isolated bursting, or both. However, irrespective of the jetting mode, the jets interacted with the flame envelope in one of three possible ways. Based on the velocity and the degree to which a jet disrupts the flame envelope, it is classified as either a flame distortion, a fire ball outside the flame or a pin hole jet (localized flame extinction), where the pin hole jets have the highest velocity (1000–1550 mm/s), while the flame distortion events have the lowest velocity (500–870 mm/s). Subsequently, the relative number of the three types of jetting events during the droplet lifetime was analyzed as a function of the type of organic gellant. It was demonstrated that the combustion behavior of gel fuels (hydroxypropyl methylcellulose: HPMC at 3 wt.%) that tend to form thin-weak-flexible shells is dominated by low-velocity flame distortion events, while the gel fuels (methylcellulose: MC at 9 wt.%) that facilitate the formation of thick-strong-rigid shells are governed by high-velocity fire ball and pin hole jets. Overall, this study provides critical insights into the jetting behavior and its characterization, which can help us to tune the droplet gasification and the gas phase mixing to achieve an effective combustion control strategy for gel fuels. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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18 pages, 2689 KiB

Open AccessArticle

Spontaneous and Electrically Induced Anisotropy of Composite Agarose Gels

by Alexandar M. Zhivkov and Svetlana H. Hristova

Gels 2022, 8(11), 753; https://doi.org/10.3390/gels8110753 - 21 Nov 2022

Viewed by 1258

Abstract

Agarose gels containing and not bacteriorhodopsin purple membranes (incorporated before gelling) manifest spontaneous optical anisotropy. The dependencies of the anisotropy on the agarose concentration and time have been studied. The rise in the anisotropy is explained by the predominant orientation of the agarose [...] Read more.

Agarose gels containing and not bacteriorhodopsin purple membranes (incorporated before gelling) manifest spontaneous optical anisotropy. The dependencies of the anisotropy on the agarose concentration and time have been studied. The rise in the anisotropy is explained by the predominant orientation of the agarose fibers during the gelling and subsequent deformation of the gel net. In the electric field, additional optical anisotropy rises, which is caused by the orientation of the membranes. A procedure has been developed to separate electrically induced and spontaneous anisotropy in composite gels. The isoelectric points and surface electric potential of bacteriorhodopsin trimer and purple membranes are calculated by the method of protein electrostatics to explain their electric asymmetry, which leads to perpendicular orientation in the direct electric field and longitudinal in the kilohertz sinusoidal field. The results allow for an increase in the separation capability of composite gels of electrophoresis for macromolecules with different sizes by applying an appropriate electric field to modulate the effective pore size. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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15 pages, 3009 KiB

Open AccessArticle

Comparative Study of Donepezil-Loaded Formulations for the Treatment of Alzheimer’s Disease by Nasal Administration

by Lupe Carolina Espinoza, Diana Guaya, Ana Cristina Calpena, Rodolfo Miguel Perotti, Lyda Halbaut, Lilian Sosa, Adriel Brito-Llera and Mireia Mallandrich

Gels 2022, 8(11), 715; https://doi.org/10.3390/gels8110715 - 05 Nov 2022

Cited by 5 | Viewed by 2159

Abstract

Alzheimer’s disease is characterized by a progressive deterioration of neurons resulting in a steady loss of cognitive functions and memory. Many treatments encounter the challenge of overcoming the blood–brain barrier, thus the intranasal route is a non-invasive effective alternative that enhances the drug [...] Read more.

Alzheimer’s disease is characterized by a progressive deterioration of neurons resulting in a steady loss of cognitive functions and memory. Many treatments encounter the challenge of overcoming the blood–brain barrier, thus the intranasal route is a non-invasive effective alternative that enhances the drug delivery in the target organ–the brain–and reduces the side effects associated with systemic administration. This study aimed at developing intranasal gels of donepezil as an approach to Alzheimer’s disease. Three different gels were elaborated and characterized in terms of pH, morphology, gelation temperature, rheology, and swelling. An in vitro release study and an ex vivo permeation in porcine nasal mucosa were conducted on Franz diffusion cells. The tolerability of the formulations was determined by the cytotoxicity in human nasal cells RPMI 2650. Results showed that pluronic gels exhibit the higher release rate and enhanced permeation compared to chitosan gel. Moreover, the combination of Pluronic F-127 and Transcutol^® P exerted a synergic effect on the permeation of donepezil through the nasal mucosa. The resulting gels showed suitable tolerance in the RPMI 2650 cell line and physicochemical characteristics for intranasal delivery, and thus gel formulations administered by nasal mucosa could be an alternative strategy to improve the bioavailability of donepezil. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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16 pages, 5137 KiB

Open AccessArticle

Evaluation of Physically and/or Chemically Modified Chitosan Hydrogels for Proficient Release of Insoluble Nystatin in Simulated Fluids

by Andra-Cristina Enache, Corneliu Cojocaru, Petrisor Samoila, Adrian Bele, Andra-Cristina Bostanaru, Mihai Mares and Valeria Harabagiu

Gels 2022, 8(8), 495; https://doi.org/10.3390/gels8080495 - 10 Aug 2022

Cited by 5 | Viewed by 1751

Abstract

To avoid fungal spreading in the bloodstream and internal organs, many research efforts concentrate on finding appropriate candidiasis treatment from the initial stage. This paper proposes chitosan-based physically or chemically cross-linked hydrogels aimed to provide sustained release of micronized nystatin (NYSm) antifungal drug, [...] Read more.

To avoid fungal spreading in the bloodstream and internal organs, many research efforts concentrate on finding appropriate candidiasis treatment from the initial stage. This paper proposes chitosan-based physically or chemically cross-linked hydrogels aimed to provide sustained release of micronized nystatin (NYSm) antifungal drug, known for its large activity spectrum. Nystatin was demonstrated itself to provide hydrodynamic/mechanic stability to the chitosan hydrogel through hydrophobic interactions and H-bonds. For chemical cross-linking of the succinylated chitosan, a non-toxic diepoxy-functionalized siloxane compound was used. The chemical structure and composition of the hydrogels, also their morphology, were evidenced by infrared spectroscopy (FTIR), by energy dispersive X-ray (EDX) analysis and by scanning electron microscopy (SEM), respectively. The hydrogels presented mechanical properties which mimic those of the soft tissues (elastic moduli < 1 MPa), necessary to ensure matrix accommodation and bioadhesion. Maximum swelling capacities were reached by the hydrogels with higher succinic anhydride content at both pH 7.4 (429%) and pH 4.2 (471%), while higher amounts of nystatin released in the simulative immersion media (57% in acidic pH and 51% in pH 7.4) occurred from the physical cross-linked hydrogel. The release mechanism by non-swellable matrix diffusion and the susceptibility of three Candida strains make all the hydrogel formulations effective for NYSm local delivery and for combating fungal infections. Full article

(This article belongs to the Special Issue Physical and Mechanical Properties of Polymer Gels)

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