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Effect of Carbopol and polyvinylpyrrolidone on the mechanical, rheological, and release properties of bioadhesive polyethylene glycol gels

Tan YT, Peh KK, Al-Hanbali O

AAPS PharmSciTech, 2000;1(3):E24.
PMID: 14727910

This study examined the mechanical (hardness, compressibility, adhesiveness, and cohesiveness) and rheological (zero-rate viscosity and thixotropy) properties of polyethylene glycol (PEG) gels that contain different ratios of Carbopol 934P (CP) and polyvinylpyrrolidone K90 (PVP). Mechanical properties were examined using a texture analyzer (TA-XT2), and rheological properties were examined using a rheometer (Rheomat 115A). In addition, lidocaine release from gels was evaluated using a release apparatus simulating the buccal condition. The results indicated that an increase in CP concentration significantly increased gel compressibility, hardness, and adhesiveness, factors that affect ease of gel removal from container, ease of gel application onto mucosal membrane, and gel bioadhesion. However, CP concentration was negatively correlated with gel cohesiveness, a factor representing structural reformation. In contrast, PVP concentration was negatively correlated with gel hardness and compressibility, but positively correlated with gel cohesiveness. All PEG gels exhibited pseudoplastic flow with thixotropy, indicating a general loss of consistency with increased shearing stress. Drug release T50% was affected by the flow rate of the simulated saliva solution. A reduction in the flow rate caused a slower drug release and hence a higher T50% value. In addition, drug release was significantly reduced as the concentrations of CP and PVP increased because of the increase in zero-rate viscosity of the gels. Response surfaces and contour plots of the dependent variables further substantiated that various combinations of CP and PVP in the PEG gels offered a wide range of mechanical, rheological, and drug-release characteristics. A combination of CP and PVP with complementary physical properties resulted in a prolonged buccal drug delivery.

Matched MeSH terms: Gels/chemistry*
Thermoreversible Carbamazepine In Situ Gel for Intranasal Delivery: Development and In Vitro, Ex Vivo Evaluation

Mohananaidu K, Chatterjee B, Mohamed F, Mahmood S, Hamed Almurisi S

AAPS PharmSciTech, 2022 Oct 21;23(8):288.
PMID: 36271212 DOI: 10.1208/s12249-022-02439-x

Over the past decade, intranasal (IN) delivery has been gaining attention as an alternative approach to conventional drug delivery routes targeting the brain. Carbamazepine (CBZ) is available as an orally ingestible formulation. The present study aims to develop a thermoreversible in situ gelling system for delivering CBZ via IN route. A cold method of synthesis has been used to tailor and optimize the thermoreversible gel composition, using poloxamer 407 (P407) (15-20% w/v) and iota carrageenan (ɩ-Cg) (0.15-0.25% w/v). The developed in situ gel showed gelation temperatures (28-33°C), pH (4.5-6.5), rheological properties (pseudoplastic, shear thinning), and mucoadhesive strength (1755.78-2495.05 dyne/cm2). The in vitro release study has shown sustained release behavior (24 h) for gel, containing significant retardation of CBZ release. The release kinetics fit to the Korsmeyer-Peppas model, suggesting the non-Fickian diffusion type controlled release behavior. Ex vivo permeation through goat nasal mucosa showed sustained release from the gel containing 18% P407 with the highest cumulative drug permeated (243.94 µg/cm2) and a permeation flux of 10.16 µg/cm2/h. After treatment with CBZ in situ gel, the barrier function of nasal mucosa remained unaffected. Permeation through goat nasal mucosa using in situ gel has demonstrated a harmless nasal delivery, which can provide a new dimension to deliver CBZ directly to the brain bypassing the blood-brain barrier.

Matched MeSH terms: Gels/chemistry
Fulltext The Effect of Cross-linking Efficiency of Drug-Loaded Novel Freeze Gelated Chitosan Templates for Periodontal Tissue Regeneration

Qasim SSB, Nogueria LP, Fawzy AS, Daood U

AAPS PharmSciTech, 2020 Jun 16;21(5):173.
PMID: 32548717 DOI: 10.1208/s12249-020-01708-x

Innovative strategies for periodontal regeneration have been the focus of research clusters across the globe for decades. In order to overcome the drawbacks of currently available options, investigators have suggested a novel concept of functionally graded membrane (FGM) templates with different structural and morphological gradients. Chitosan (CH) has been used in the past for similar purpose. However, the composite formulation of composite and tetracycline when cross-linked with glutaraldehyde have received little attention. Therefore, the purpose of the study was to investigate the drug loading and release characteristics of novel freeze gelated chitosan templates at different percentages of glutaraldehyde. These were cross-linked with 0.1 and 1% glutaraldehyde and loaded with doxycycline hyclate. The electron micrographs depicted porous morphology of neat templates. After cross-linking, these templates showed compressed ultrastructures. Computerized tomography analysis showed that the templates had 88 to 92% porosity with average pore diameter decreased from 78 to 44.9 μm with increasing concentration. Fourier transform infrared spectroscopy showed alterations in the glycosidic segment of chitosan fingerprint region which after drug loading showed a dominant doxycycline spectral composite profile. Interestingly, swelling profile was not affected by cross-linking either at 0.1 and 1% glutaraldehyde and template showed a swelling ratio of 80%, which gained equilibrium after 15 min. The drug release pattern also showed a 40 μg/mL of release after 24 h. These doxycycline-loaded templates show their tendency to be used in a functionally graded membrane facing the defect site.

Matched MeSH terms: Gels
Haemoglobin E-hereditary elliptocytosis in Malayan aborigines

Lie-Injo LE, Fix A, Bolton JM, Gilman RH

Acta Haematol., 1972;47(4):210-6.
PMID: 4625303
Matched MeSH terms: Gels
Aceclofenac topical dosage forms: in vitro and in vivo characterization

Dua K, Pabreja K, Ramana MV

Acta Pharm, 2010 Dec;60(4):467-78.
PMID: 21169138 DOI: 10.2478/v1007-010-0036-5

Aceclofenac is a new generation non-steroidal anti-inflammatory drug showing effective anti-inflammatory and analgesic properties. It is available in the form of tablets of 100 mg. Importance of aceclofenac as a NSAID has inspired development of topical dosage forms. This mode of administration may help avoid typical side effects associated with oral administration of NSAIDs, which have led to its withdrawal. Furthermore, aceclofenac topical dosage forms can be used as a supplement to oral therapy for better treatment of conditions such as arthritis. Ointments, creams, and gels containing 1% (m/m) aceclofenac have been prepared. They were tested for physical appearance, pH, spreadability, extrudability, drug content uniformity, in vitro diffusion and in vitro permeation. Gels prepared using Carbopol 940 (AF2, AF3) and macrogol bases (AF7) were selected after the analysis of the results. They were evaluated for acute skin irritancy, anti-inflammatory and analgesic effects using the carrageenan-induced thermal hyperalgesia and paw edema method. AF2 was shown to be significantly (p < 0.05) more effective in inhibiting hyperalgesia associated with inflammation, compared to AF3 and AF7. Hence, AF2 may be suggested as an alternative to oral preparations.

Matched MeSH terms: Gels
Proteomes of the female salivary glands of Simulium nigrogilvum and Simulium nodosum, the main human-biting black flies in Thailand

Hempolchom C, Reamtong O, Sookrung N, Srisuka W, Sakolvaree Y, Chaicumpa W, et al.

Acta Trop, 2019 Jun;194:82-88.
PMID: 30922801 DOI: 10.1016/j.actatropica.2019.03.026

Although several studies have reported pharmacological and immunological activity, as well as the role of black flies in transmitting pathogens to vertebrate hosts through salivary glands (SG) during blood feeding, SG proteomes of the anthropophilic black flies in Thailand have never been reported. Therefore, this study determined the SG proteomes of female S. nigrogilvum and S. nodosum. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional (2-DE) gels containing separated SG proteins of individual species were subjected to liquid chromatography-tandem mass spectrometry (LCMS/MS) and an orthologous protein search from eukaryotic organism, nematocera and simuliidae databases for total protein identification. SDS-PAGE and protein staining revealed at least 13 and 9 major protein bands in the SGs of female S. nigrogilvum and S. nodosum, respectively, as well as several minor ones. The 2-DE demonstrated a total of 56 and 41 protein spots for S. nigrogilvum and S. nodosum, respectively. Most of the proteins obtained in both species were enzymes involved in blood feeding, including proteases, apyrases, hyaluronidases, aminopeptidase and elastase. The results obtained in this study provided a new body of knowledge for a better understanding on the role of salivary gland proteins in these black fly species in Thailand.

Matched MeSH terms: Gels
Stacked films immobilization of MBTH in nafion/sol-gel silicate and horseradish peroxidase in chitosan for the determination of phenolic compounds

Abdullah J, Ahmad M, Heng LY, Karuppiah N, Sidek H

Anal Bioanal Chem, 2006 Nov;386(5):1285-92.
PMID: 17031625

The stacked-film immobilization of 3-methyl-2-benzothiazolinone hydrazone (MBTH) in hybrid nafion/sol-gel silicate film and horseradish peroxidase (HRP) in chitosan, performed in order to allow the determination of phenolic compounds, was investigated via an optical method. The stacked films were deposited onto a microscope glass slide by a spin-coating technique. The quinone or free radical product formed by the enzymatic reactions of phenolic compounds interacts with MBTH to form azo-dye products, which can be measured spectrophotometrically at a wavelength of 500 nm. The color intensity of the product was found to increase in proportion to the phenolic concentration after 5 min of exposure. The response of the biosensor was linear over concentration ranges of 0.025-0.500, 0.010-0.070 and 0.050-0.300 mM for guaiacol, resorcinol and o-cresol, respectively, and gave detection limits of 0.010, 0.005 and 0.012 mM. The sensor exhibited good sensitivity and stability for at least two months.

Matched MeSH terms: Gels
Development and anti-microbial potential of topical formulations containing Cocos nucifera Linn

Sheshala R, Ying LT, Hui LS, Barua A, Dua K

Antiinflamm Antiallergy Agents Med Chem, 2013;12(3):253-64.
PMID: 23746224

In order to achieve better treatment for local wounds and bacterial infections, topical formulations containing Cocos nucifera Linn. were developed. These formulations were evaluated for their physicochemical properties and antimicrobial efficacy against various strains of microorganisms. Semisolid formulations containing 5% w/w of Cocos nucifera Linn. were prepared by employing different dermatological bases and were evaluated for their physical appearance, pH, rheological properties, FTIR-spectroscopic analysis, thermodynamic stability and stability studies. The antimicrobial activity of each prepared formulation was determined using disk-diffusion method against various strains of microorganisms. All the prepared formulations were found to be stable and exhibited suitable physicochemical characteristics including pH, viscosity and spreadability which are necessary for an ideal topical preparation, in addition to strong antimicrobial activity. Carbopol gel base was found to be the most suitable dermatological base for Cocos nucifera Linn. in comparsion to other bases. Cocos nucifera Linn. formulations showed great potential for wounds and local bacterial infections. Moreover, carbopol gel base with its aesthetic appeal was found to be a suitable dermatological base for Cocos nucifera Linn. semisolid formulation as it had demonstrated significant physicochemical properties and greater diffusion when assessed using disk- diffusion method.

Matched MeSH terms: Gels/chemistry*
Hydrolysis of native and heat-treated starches at sub-gelatinization temperature using granular starch hydrolyzing enzyme

Uthumporn U, Shariffa YN, Karim AA

Appl Biochem Biotechnol, 2012 Mar;166(5):1167-82.
PMID: 22203397 DOI: 10.1007/s12010-011-9502-x

The effect of heat treatment below the gelatinization temperature on the susceptibility of corn, mung bean, sago, and potato starches towards granular starch hydrolysis (35°C) was investigated. Starches were hydrolyzed in granular state and after heat treatment (50°C for 30 min) by using granular starch hydrolyzing enzyme for 24 h. Hydrolyzed heat-treated starches showed a significant increase in the percentage of dextrose equivalent compared to native starches, respectively, with corn 53% to 56%, mung bean 36% to 47%, sago 15% to 26%, and potato 12% to 15%. Scanning electron microscopy micrographs showed the presence of more porous granules and surface erosion in heat-treated starch compared to native starch. X-ray analysis showed no changes but with sharper peaks for all the starches, suggested that hydrolysis occurred on the amorphous region. The amylose content and swelling power of heat-treated starches was markedly altered after hydrolysis. Evidently, this enzyme was able to hydrolyze granular starches and heat treatment before hydrolysis significantly increased the degree of hydrolysis.

Matched MeSH terms: Gels
Characterisation of a Ferrous Agarose Xylenol (FAX) gel for radiotherapy dose measurement

Leong LH, Kandaiya S, Seng NB

Australas Phys Eng Sci Med, 2007 Jun;30(2):135-40.
PMID: 17682403

The oxidation of ferrous to ferric ions due to ionizing radiation has been used for chemical dosimetry since 1927. The introduction of metal indicator dye xylenol orange (XO) sensitises the measurement of ferric ion yield. A ferrous sulphate- agarose- xylenol orange (FAX) gel was prepared and the gel then exposed to dose ranging from 0.2 to 10 Gy using various high energy photon and electron beams from a linear accelerator. Some general characteristics of FAX such as energy dependence, optical density (OD)-dose relationship, reproducibility and auto-oxidation of ferrous ions were analysed. The radiation yield G of the gel was calculated for gels prepared in oxygen and in air and the values were 46.3 +/- 2.1 and 40.9 +/- 1.4 Fe3+ per 100 eV for photons respectively. However for stock gel which was kept for 5 days pre-irradiation the G value decreased to 36.6 +/- 1.1. The gel shows linearity in OD-dose relationship, energy independence and reproducibility over the dose range investigated. Auto-oxidation of ferrous ions resulted in optical density changes of less than 1.5% per day.

Matched MeSH terms: Gels
Fulltext Talcum powder or aqueous gel to aid external cephalic version: a randomised controlled trial

Vallikkannu N, Nadzratulaiman WN, Omar SZ, Si Lay K, Tan PC

BMC Pregnancy Childbirth, 2014 Jan 28;14:49.
PMID: 24468078 DOI: 10.1186/1471-2393-14-49

BACKGROUND: External cephalic version (ECV) is offered to reduce the number of Caesarean delivery indicated by breech presentation which occurs in 3-4% of term pregnancies. ECV is commonly performed aided by the application of aqueous gel or talcum powder to the maternal abdomen. We sought to compare gel with powder during ECV on achieving successful version and increasing tolerability.
METHOD: We enrolled 95 women (≥ 36 weeks gestation) on their attendance for planned ECV. All participants received terbutaline tocolysis. Regional anaesthesia was not used. ECV was performed in the standard fashion after the application of the allocated aid. If the first round (maximum of 2 attempts) of ECV failed, crossover to the opposing aid was permitted.
RESULTS: 48 women were randomised to powder and 47 to gel. Self-reported procedure related median [interquartile range] pain scores (using a 10-point visual numerical rating scale VNRS; low score more pain) were 6 [5-9] vs. 8 [7-9] P = 0.03 in favor of gel. ECV was successful in 21/48 (43.8%) vs. 26/47 (55.3%) RR 0.6 95% CI 0.3-1.4 P = 0.3 for powder and gel arms respectively. Crossover to the opposing aid and a second round of ECV was performed in 13/27 (48.1%) following initial failure with powder and 4/21 (19%) after failure with gel (RR 3.9 95% CI 1.0-15 P = 0.07). ECV success rate was 5/13 (38.5%) vs. 1/4 (25%) P = 0.99 after crossover use of gel or powder respectively. Operators reported higher satisfaction score with the use of gel (high score, greater satisfaction) VNRS scores 6 [4.25-8] vs 8 [7-9] P = 0.01.
CONCLUSION: Women find gel use to be associated with less pain. The ECV success rate is not significantly different.
TRIAL REGISTRATION: The trial is registered with ISRCTN (identifier ISRCTN87231556).

Matched MeSH terms: Gels/administration & dosage
Fulltext Interaction between Metarhizium anisopliae and Its Host, the Subterranean Termite Coptotermes curvignathus during the Infection Process

Syazwan SA, Lee SY, Sajap AS, Lau WH, Omar D, Mohamed R

Biology (Basel), 2021 Mar 25;10(4).
PMID: 33806225 DOI: 10.3390/biology10040263

Metarhizium anisopliae (Metchnikoff) Sorokin, a pathogenic fungus to insects, infects the subterranean termite, Coptotermes curvignathus Holmgren, a devastating pest of plantation trees in the tropics. Electron microscopy and proteomics were used to investigate the infection and developmental process of M. anisopliae in C. curvignathus. Fungal infection was initiated by germ tube penetration through the host's cuticle as observed at 6 h post-inoculation (PI), after which it elongated into the host's integumental tissue. The colonization process continued as seen from dissemination of blastospores in the hemocoel at 96 h PI. At this time point, the emergent mycelia had mummified the host and forty-eight hours later, new conidia were dispersed on the termites' body surface. Meanwhile, hyphal bodies were observed in abundance in the intercellular space in the host's body. The proteomes of the pathogen and host were isolated separately using inoculated termite samples withdrawn at each PI-time point and analyzed in two-dimensional electrophoresis (2-DE) gels. Proteins expressed in termites showed evidence of being related to cell regulation and the immune response, while those expressed in M. anisopliae, to transportation and fungal virulence. This study provides new information on the interaction between termites and its entomopathogen, with potential utilization for developing future biopesticide to control the termite population.

Matched MeSH terms: Gels
The mechanisms of fibroblast-mediated compaction of collagen gels and the mechanical niche around individual fibroblasts

Feng Z, Wagatsuma Y, Kikuchi M, Kosawada T, Nakamura T, Sato D, et al.

Biomaterials, 2014 Sep;35(28):8078-91.
PMID: 24976242 DOI: 10.1016/j.biomaterials.2014.05.072

Fibroblast-mediated compaction of collagen gels attracts extensive attention in studies of wound healing, cellular fate processes, and regenerative medicine. However, the underlying mechanism and the cellular mechanical niche still remain obscure. This study examines the mechanical behaviour of collagen fibrils during the process of compaction from an alternative perspective on the primary mechanical interaction, providing a new viewpoint on the behaviour of populated fibroblasts. We classify the collagen fibrils into three types - bent, stretched, and adherent - and deduce the respective equations governing the mechanical behaviour of each type; in particular, from a putative principle based on the stationary state of the instantaneous Hamiltonian of the mechanotransduction system, we originally quantify the stretching force exerted on each stretched fibrils. Via careful verification of a structural elementary model based on this classification, we demonstrate a clear physical picture of the compaction process, quantitatively elucidate the panorama of the micro mechanical niche and reveal an intrinsic biphasic relationship between cellular traction force and matrix elasticity. Our results also infer the underlying mechanism of tensional homoeostasis and stress shielding of fibroblasts. With this study, and sequel investigations on the putative principle proposed herein, we anticipate a refocus of the research on cellular mechanobiology, in vitro and in vivo.

Matched MeSH terms: Gels/chemistry
A fibril-based structural constitutive theory reveals the dominant role of network characteristics on the mechanical behavior of fibroblast-compacted collagen gels

Feng Z, Ishiguro Y, Fujita K, Kosawada T, Nakamura T, Sato D, et al.

Biomaterials, 2015 Oct;67:365-81.
PMID: 26247391 DOI: 10.1016/j.biomaterials.2015.07.038

In this paper, we present a general, fibril-based structural constitutive theory which accounts for three material aspects of crosslinked filamentous materials: the single fibrillar force response, the fibrillar network model, and the effects of alterations to the fibrillar network. In the case of the single fibrillar response, we develop a formula that covers the entropic and enthalpic deformation regions, and introduce the relaxation phase to explain the observed force decay after crosslink breakage. For the filamentous network model, we characterize the constituent element of the fibrillar network in terms its end-to-end distance vector and its contour length, then decompose the vector orientation into an isotropic random term and a specific alignment, paving the way for an expanded formalism from principal deformation to general 3D deformation; and, more important, we define a critical core quantity over which macroscale mechanical characteristics can be integrated: the ratio of the initial end-to-end distance to the contour length (and its probability function). For network alterations, we quantitatively treat changes in constituent elements and relate these changes to the alteration of network characteristics. Singular in its physical rigor and clarity, this constitutive theory can reproduce and predict a wide range of nonlinear mechanical behavior in materials composed of a crosslinked filamentous network, including: stress relaxation (with dual relaxation coefficients as typically observed in soft tissues); hysteresis with decreasing maximum stress under serial cyclic loading; strain-stiffening under uniaxial tension; the rupture point of the structure as a whole; various effects of biaxial tensile loading; strain-stiffening under simple shearing; the so-called "negative normal stress" phenomenon; and enthalpic elastic behaviors of the constituent element. Applied to compacted collagen gels, the theory demonstrates that collagen fibrils behave as enthalpic elasticas with linear elasticity within the gels, and that the macroscale nonlinearity of the gels originates from the curved fibrillar network. Meanwhile, the underlying factors that determine the mechanical properties of the gels are clarified. Finally, the implications of this study on the enhancement of the mechanical properties of compacted collagen gels and on the cellular mechanics with this model tissue are discussed.

Matched MeSH terms: Gels/metabolism*
Ice-templated graphene oxide/chitosan aerogel as an effective adsorbent for sequestration of metanil yellow dye

Lai KC, Hiew BYZ, Lee LY, Gan S, Thangalazhy-Gopakumar S, Chiu WS, et al.

Bioresour Technol, 2019 Feb;274:134-144.
PMID: 30502604 DOI: 10.1016/j.biortech.2018.11.048

Graphene oxide/chitosan aerogel (GOCA) was prepared by a facile ice-templating technique without using any cross-linking reagent for metanil yellow dye sequestration. The adsorption performance of GOCA was investigated by varying the adsorbent mass, shaking speed, initial pH, contact time, concentration and temperature. The combined effects of adsorption parameters and the optimum conditions for dye removal were determined by response surface methodology. GOCA exhibited large removal efficiencies (91.5-96.4%) over a wide pH range (3-8) and a high adsorption capacity of 430.99 mg/g at 8 mg adsorbent mass, 400 mg/L concentration, 35.19 min contact time and 175 rpm shaking speed. The adsorption equilibrium was best represented by the Langmuir model. GOCA could be easily separated after adsorption and regenerated for re-use in 5 adsorption-desorption cycles thereby maintaining 80% of its adsorption capability. The relatively high adsorption and regeneration capabilities of GOCA render it an attractive adsorbent for treatment of azo dye-polluted water.

Matched MeSH terms: Gels/chemistry
Fulltext DNA horizontal polyacrylmide gel electrophoresis

Elsie Yee, Y. S., Zainal Zahari, AHMAD ISMAIL, YAP, C.K., TAN, S. G

Buletin Persatuan Genetik Malaysia, 2010;16(1):19-22.
MyJurnal

Electrophoresis is a crucial step for the studies of proteins, allozymes, DNAs and RNAs. Two commonly used electrophoresis systems are agarose gel and polyacrylmide gel. Agarose gel is frequently used for DNAs and RNAs studies whereas polyacrylmide gel is widely used for the studies of other macromolecules such as proteins, allozymes (isozymes), DNAs and RNAs. The banding patterns of the gels, rather than the numbers of bands appearing on the gels are important for scoring in fingerprinting, footprinting and in population genetic studies.

Matched MeSH terms: Gels
Chitin nanocrystals based complex fluids: A green nanotechnology

Kumar S, Foroozesh J

Carbohydr Polym, 2021 Apr 01;257:117619.
PMID: 33541647 DOI: 10.1016/j.carbpol.2021.117619

Chitin biopolymer has received significant attention recently by many industries as a green technology. Nanotechnology has been used to make chitin nanocrystals (ChiNCs) that are rod-shaped natural nanomaterials with nanoscale size. Owing to the unique features such as biodegradability, biocompatibility, renewability, rod-shape, and excellent surface and interfacial, physiochemical, and thermo-mechanical properties; ChiNCs have been green and attractive products with wide applications specifically in medical and pharmaceutical, food and packaging, cosmetic, electrical, and electronic, and also in the oil and gas industry. This review aims to give a comprehensive and applied insight into ChiNCs technology. It starts with reviewing different sources of chitin and their extraction methods followed by the characterization of ChiNCs. Furthermore, a detailed investigation into various complex fluids (dispersions, emulsions, foams, and gels) stabilized by ChiNCs and their characterisation have been thoroughly deliberated. Finally, the current status including ground-breaking applications, untapped investigations, and future prospective have been presented.

Matched MeSH terms: Gels
Pectin as a rheology modifier: Origin, structure, commercial production and rheology

Chan SY, Choo WS, Young DJ, Loh XJ

Carbohydr Polym, 2017 Apr 01;161:118-139.
PMID: 28189220 DOI: 10.1016/j.carbpol.2016.12.033

Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of α-1,4-linked d-galacturonic acids in common. They have been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and/or thickeners in food, pharmaceutical, personal care and polymer products. Commercial pectin is classified as high methoxy pectin (HMP) with a degree of methylation (DM) >50% and low methoxy pectin (LMP) with a DM <50%. Amidated low methoxy pectins (ALMP) can be obtained through aminolysis of HMP. Gelation of HMP occurs by cross-linking through hydrogen bonds and hydrophobic forces between the methyl groups, assisted by a high co-solute concentration and low pH. In contrast, gelation of LMP occurs by the formation of ionic linkages via calcium bridges between two carboxyl groups from two different chains in close proximity, known as the 'egg-box' model. Pectin gels exhibit Newtonian behaviour at low shear rates and shear-thinning behaviour when the shear rate is increased. An overview of pectin from its origin to its physicochemical properties is presented in this review.

Matched MeSH terms: Gels/chemistry
Synthesis of chitosan aerogels as promising carriers for drug delivery: A review

Wei S, Ching YC, Chuah CH

Carbohydr Polym, 2020 Mar 01;231:115744.
PMID: 31888854 DOI: 10.1016/j.carbpol.2019.115744

Chitosan with abundant functional groups is regarded as important ingredients for preparing aerogel materials in life science. The biocompatibility and biodegradability of chitosan aerogels, coupled to the variety of chemical functionalities they include, result in them promising carriers for drug delivery. Moreover, chitosan aerogels as drug delivery vehicles can offer improved drug bioavailability and drug loading capacity due to their highly porous network, considerably large specific surface area and polycationic feature. The major focus of this review lies in preparation methods of chitosan aerogels from acidic aqueous solution and chitosan solution in Ionic Liquids (ILs). In addition, chitosan aerogels as drug delivery carriers are introduced in detail and expected to inspire readers to create new kind of drug delivery system based on chitosan aerogels. Finally, growing points and perspectives of chitosan aerogels in drug delivery system are given.

Matched MeSH terms: Gels/chemical synthesis; Gels/therapeutic use; Gels/chemistry*
Physical methods of reducing the transmission of nosocomial infections via ultrasound and probe

Abdullah BJ, Mohd Yusof MY, Khoo BH

Clin Radiol, 1998 Mar;53(3):212-4.
PMID: 9528873

Nosocomial infections are posing an increasingly serious problem in the hospital setting. With the increasing use of ultrasound in medical diagnosis, there is the potential for transmission of nosocomial infections via the ultrasound transducer and coupling gel. We evaluated the use of different membranes (three types of commercially available household cling film, condom, surgical glove and Opsite) applied over the ultrasound probe to determine if these were safe, convenient, cost-effective and did not impair the performance parameters of the ultrasound probe. None of the membranes impaired the physical scanning parameters using a Multi-Purpose Tissue/Cyst Phantom. The cling film was ideal for general use in terms of cost and convenience as well as safety. For sterile use the Opsite was better overall compared to the surgical glove, though it costs significantly more. The condom and surgical glove, though safe, were not very convenient to use for scanning.

Matched MeSH terms: Gels

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