SEARCH · Search PubMed

Results for “Alginates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,171 records · Page 65Linked to original sources

PubMed1994

Symptomatic foreign body reaction to haemostatic alginate.

Kaltostat, a haemostatic wound dressing made from non-woven sodium calcium alginate fibres is becoming more frequently and widely used by practitioners. We report a florid foreign body giant cell reaction elicited by Kaltostat which had been used to obtain haemostasis in an apicectomy cavity on an upper lateral incisor approximately 7 months earlier. The case demonstrates that alginate fibres left in situ may elicit a long-lasting and symptomatic adverse foreign body reaction. This material should be reserved for problematic haemorrhage and be removed from the tooth socket soon after haemostasis.

Alginates↗

PubMed1989

An in vitro study of the antiviral properties of an alginate impression material impregnated with disinfectant.

The antiviral properties of a new alginate impression material impregnated with a disinfectant (didecyldimethyl ammonium chloride) were evaluated in vitro against herpes simplex virus type I and poliovirus type I. The material was exposed to the virus suspension for periods of up to 60 min. The impregnated alginate material showed no clinically acceptable effect against either virus, although log reductions of 1.0 and 1.7 plaque-forming units of herpes virus were obtained after exposure to the material containing the disinfectant for 5 and 60 min, respectively.

Alginates↗

PubMed1996

Electron-transfer function of NAD+-immobilized alginic acid.

Polymerized NAD+ (Alg-NAD+) was prepared and its electrochemical properties were investigated. NAD+ has been covalently immobilized at the carboxyl group of alginic acid using water soluble carbodiimide (EDC) and then Alg-NAD+s of various NAD+ density were obtainable depending on NAD+ concentration in the reaction mixture. Absorbance of 260 nm of Alg-NAD+s showed that 3.4 to 17.6% of carboxyl groups of alginic acid were coupled with NAD+. The coenzyme activity of immobilized NAD+ has reached 80 to 90% on each Alg-NAD+. A cathodic peak in the cyclic voltammogram of Alg-NAD+ appeared at -1.2 V (vs. SCE) corresponding to the reduction wave of free NAD+. The anodic wave of NAD dimer was not observed in the presence of 2.0 mM methyl viologen and 5 units of diaphorase and NAD+ immobilized on the composite electrode could be reduced to the normal NADH. The ratio of apparent diffusion coefficient (Dapp.) of Alg-NAD+ and free NAD+ was evaluated from the variation of ipc with the square root of sweep rate (v 1/2). Despite the high molecular weight of Alg-NAD+, Dapp. Alg-NAD+/Dapp. free NAD+ are larger than that expected. These results indicate that electron transfer occurred effectively between each NAD+ molecule immobilized onto the polymer chain. It is also confirmed by a conjugated redox enzyme reaction with Alg-NAD+.

Alginates↗

PubMed1992

Signal transduction in exopolysaccharide alginate synthesis: phosphorylation of the response regulator AlgR1 in Pseudomonas aeruginosa and Escherichia coli.

Synthesis of alginate by Pseudomonas aeruginosa correlates with its pathogenicity in the lungs of patients suffering from cystic fibrosis (CF). Alginate synthesis-encoding genes (alg) in P. aeruginosa are normally silent, but are specifically triggered in the CF lung environment. The promoter for the algD gene, located at the upstream end of the alg cluster, is activated by environmental factors such as high osmolarity, nutrient limitation and dehydration. Several regulatory proteins are known to control transcription from the algD promoter. Among these proteins is AlgR1 which is homologous to the phosphorylation-dependent response regulators of the two-component signal transduction system. In this paper, we report that AlgR2, an 18-kDa protein which in cooperation with AlgR1 regulates the algD promoter, undergoes phosphorylation in the presence of ATP. The phosphate group acquired by AlgR2 is then transferred to AlgR1. In addition, we show that AlgR1 can be phosphorylated by an AlgR2-analog in Escherichia coli. AlgR1 is isolated in a phosphorylatable 80-kDa complex in association with AlgR2 in P. aeruginosa and the AlgR2-analog in E. coli.

Alginates↗

PubMed1996

Ion transport studies in calcium alginate gels by magnetic resonance microscopy.

Polyelectrolyte biopolymers such as calcium alginate are becoming increasingly important for the recovery of heavy metals from aqueous solutions. To understand the mechanism of ion transport in these biopolymer systems, the transport of copper ions into calcium alginate gels was investigated using proton nuclear magnetic resonance (NMR) microscopy. Copper ion transport was imaged using an inversion recovery technique which utilizes the paramagnetic effect of copper on water proton relaxation times. Diffusion experiments were performed in a diffusion cell designed to approximate a semi-infinite slab geometry at temperatures between 278 and 313 K using copper reservoir concentrations between 10 and 60 mM. The diffusion coefficient of copper in these gels was calculated from the NMR data to fit a combined diffusion-reaction model involving a diffusion term (D) and a kinetic binding term (k). At 23 degrees C, the diffusion coefficients in 1, 2, and 3% (w/v) gels were 3.1 x 10(10), 2.0 x 10(10), and 1.4 x 10(10) m2/s, respectively. The activation energy for diffusion in the 2% (w/v) gel was 28 kJ/mol.

Alginates↗

PubMed2004

Motility and fertility of alginate encapsulated boar spermatozoa.

Ejaculated boar spermatozoa are vulnerable to cold shock. Prolonged storage of boar spermatozoa at low temperatures reduces survival rate, resulting in a bottleneck for the extension of artificial insemination in pig husbandry. This study evaluated whether alginate microencapsulization processing can improve the longevity of boar spermatozoa stored at 5 degrees C and the fertility of microencapsulated spermatozoa in vivo. Sperm-rich fraction semen from three purebred boars were concentrated and microencapsulated using alginate at 16-18 degrees C, and then were stored at 5 degrees C. Following storage for 1, 3 and 7 days, the microcapsule was taken out to assess sperm release under 37 degrees C incubation with or without 110 rpm stirring. The percentage of sperm released from microcapsules with 110 rpm stirring was higher than without stirring (81 versus 60%) after 24h of incubation. In another experiment, semen was also microencapsulated to evaluate the sperm motility. The motility of spermatozoa was assessed at 10 min, 8, 24, 32, 48, 56 and 72 h following incubation at 37 degrees C for nine consecutive days. The fertility of the free and microencapsulated semen was assessed by inseminating sows, and the reproductive traits (conception rate, farrowing rate, and litter size) were recorded. The motility of encapsulated spermatozoa was significantly higher than that of free semen after 8h incubation at 37 degrees C after storing for over three days (P<0.05). No significant difference existed in conception rate, farrowing rate, and litter size between the microencapsulated and non-encapsulated semen after four days of storage. In conclusion, microencapsulation can increase the longevity of boar spermatozoa and may sustain in vivo ova fertilization ability.

Alginates↗

PubMed2006

In vitro evaluation of alginate encapsulated adipose-tissue stromal cells for use as injectable bone graft substitute.

This study aims to investigate the survival and osteogenic behavior of murine-derived adipose-tissue stromal cells (ATSCs) encapsulated in alginate microcapsules thereby instigating further studies in this cell delivery strategy for in vivo osteogenesis. Cell viability was quantified using a tetrazolium-based assay and osteogenic differentiation was evaluated by both alkaline-phosphatase (ALP) histochemistry and osteocalcin mRNA analysis. Following microencapsulation, cell numbers increased from 3.9 x 10(3) on day 1 to 7.8 x 10(3) on day 7 and maintained excellent viability in the course of 21-day culture. ALP was 6.9, 5.5, and 3.2 times higher than monolayer cultures on days 7, 14, and 21, respectively. In addition, osteocalcin mRNA was detectable in encapsulated cultures earlier (day 14) than monolayer cultures. We conclude that alginate microcapsules can act as three-dimensional matrix for ATSC proliferation and has potential for use as injectable, biodegradable scaffold in bone tissue engineering.

Adipocytes↗

PubMed2005

Biochemical analysis of alginate biosynthesis protein AlgX from Pseudomonas aeruginosa: purification of an AlgX-MucD (AlgY) protein complex.

AlgX was found to be an essential protein for alginate biosynthesis, but its function is unknown. In this study, an isogenic, marker-free algX-knock out mutant was generated. In-frame fusions of algX with phoA and lacZ were analysed, respectively. No LacZ-activity was detected, but the PhoA fusion showed alkaline phosphatase activity. These data indicated that the C-terminus of AlgX is located in the periplasm, but is not required for protein function. Accordingly, AlgX with C-terminal fusion of strep tag II restored alginate production in the algX-negative mutant and was purified under native conditions from periplasmic and crude cell extracts, respectively. AlgX was identified by MALDI/TOF-MS analysis of tryptic peptides. TritonX-100 mediated solubilisation of cytoplasmic membrane and subsequent strep tag II affinity chromatography led to purification of an AlgX-MucD (AlgY) protein complex as identified by MALDI/TOF-MS analysis. This data suggested a protein-protein interaction between AlgX and MucD (AlgY) with a 1:1 stoichiometry. Thus AlgX might exert its function via interaction with MucD (AlgY). Immunoelectron microscopic localisation of AlgX-strep tag II suggested a localisation close to the cytoplasmic membrane.

Alginates↗

PubMed2004

Towards a fully-synthetic substitute of alginate: development of a new process using thermal gelation and chemical cross-linking.

We have previously described a gelation process based on the occurrence of both physical and a chemical mechanisms ('tandem process'), in which a telechelic linear poly(propylene glycol)-bl-poly(ethylene glycol)-bl-poly(propylene glycol) is first thermally gelled and subsequently covalently cross-linked by the reaction of polymer end groups at the termini of the copolymer. The quick kinetics of the reverse thermal gelation and the harmless character of the Michael-type addition between two sets of terminal groups, acrylates on one set and thiols on the other, allows irreversibly cross-linked hydrogels to be obtained in a rapid and biocompatible fashion, even when gelation was conducted in direct contact with cells. This allows in principle for an application of the tandem process in cell encapsulation. In the present work, we have optimized the macromolecular architecture and functionality of the precursors for allowing the use of the tandem process in encapsulation devices designed for calcium alginate. The mechanical, diffusional and biocompatibility properties of these materials were characterized; the comparison of mass transport properties of the tandem gels with those of calcium alginate suggests a similar or even better immunoisolation effect.

Acrylates↗

PubMed2006

Alginate-whey protein granular microspheres as oral delivery vehicles for bioactive compounds.

Alginate (AL)-whey protein isolate (WPI) microspheres of varied WPI/AL ratio, particle diameter and concentration of polymer bead forming solution (C(AL+WPI)) were prepared in order to develop a biocompatible vehicle for oral administration of bioactive compounds. Microscopy revealed a special matrix/granular structure for microspheres with a WPI/AL ratio of 8:2, 100 microm diameter and C(AL+WPI) of 5% (AL-WPI A2), featuring WPI granules 3-10 microm in diameter homogeneously distributed within an AL spherical matrix. The compound release properties of these microspheres were investigated in simulated gastric and intestinal fluids (SGF and SIF). They demonstrated the desirable property of retarding riboflavin release in SGF and underwent alginate matrix erosion together with liberation of WPI granules in SIF, followed by complete release of the riboflavin. Riboflavin release in SGF and in SIF without pancreatin followed the Higuchi diffusion model while release in SIF in the presence of pancreatin was attributed to WPI granule degradation.

Administration, Oral↗

PubMed2006

Biosorption of no-carrier-added radionuclides by calcium alginate beads using 'tracer packet' technique.

The aim of this study was to determine the adsorption behaviour of various micronutrient elements e.g., (61)Cu, (62,63)Zn, (66,67,68)Ga, (66,67,69)Ge, (71,72)As present in no-carrier-added state, with calcium alginate (CA) using 'tracer packet' technique. High Ge and Ga and moderate Cu removal were achieved at pH 7 and pH 5, respectively. Results on the studies to recover all the three radionuclides from the calcium alginate beads using desorbing reagents, HCl, thiourea, ammonium oxalate and sodium nitrite showed that 0.1 M HCl and 0.1 M ammonium oxalate removed Cu and Ge moderately. The amount of Ga desorbed by all the washing liquids was almost negligible, except sodium nitrite.

Adsorption↗

PubMed2006

Sequestration of biogenic amines by alginic and fulvic acids.

The interaction of natural (alginic and fulvic acids) and synthetic (polyacrylic acid 2.0 kDa) polyelectrolytes with some protonated polyamines [diamines: ethylendiamine, 1,4-diaminobutane (or putrescine), 1,5-diaminopentane (or cadaverine); triamines: N-(3-aminopropyl)-1,4-diaminobutane (or spermidine), diethylenetriamine; tetramine: N,N'-bis(3-aminopropyl)-1,4-diaminobutane (or spermine); pentamine: tetraethylene-pentamine; hexamine: pentaethylenehexamine] was studied at T=25 degrees C by potentiometry and calorimetry. Measurements were performed without supporting electrolyte, in order to avoid interference, and results were reported at I=0 mol L(-)(1). For all the systems, the formation of (am)L(2)H(i) species was found (am=amine; L=polyelectrolyte; i=1...4, depending on the amine considered). The stability of polyanion-polyammonium cation complexes is always significant, and for high-charged polycations, we observe a stability comparable to that of strong metal complexes. For example, by considering the formation reaction (am)H(i)+2L=(am)L(2)H(i) we found log K(i)=6.0, 6.5 and 10.8 for i=1, 2 and 3, respectively, in the system alginate-spermidine. Low and positive formation DeltaH(degrees) values indicate that the main contribution to the stability is entropic in nature. The sequestering ability of polyelectrolytes toward amines was modelled by a sigmoid Boltzman type equation. Some empirical relationships between stability, charges and DeltaG(degrees) and TDeltaS(degrees) are reported. Mean values per salt bridge of formation thermodynamic parameters (DeltaX(degrees) (n)) are DeltaG(degrees) (n)=-5.8+/-0.4, DeltaH degrees (n)=0.7+/-0.5 and TDeltaS(degrees) (n)=6.5+/-0.5 kJmol(-)(1) for all the systems studied in this work.

Alginates↗

PubMed2005

Factors affecting protein release from microcapsule prepared by liposome in alginate.

A new type of drug delivery system that microcapsule was prepared by liposome in alginate on this paper, bovine serum albumin (BSA) as an model drug. Influences of liposomes composition and multivalent cations on morphology, enveloped rate, integrality and release in vitro from microcapsule were investigated. The results are showed that Ca2+ and Ba2+ made hydrogels form easier than Al3+ and particle size were uniform, circular, but microcapsule prepared by Al3+ was flat circular and easily adhere to each other. Particle size of all microcapsules was 200-300 microm after dryness, measured by vernier calliper. BSA enveloped rate prepared by PC/PG/Chol and Ba2+ was highest, 77.65%, and also correlative to concentration of lipid. At the other hand, Ba2+ microcapsule prepared by liposome in alginate has not an initial burst and have a good performance on delivering protein. Integrality of protein was not destroyed after encapsulated.

Alginates↗

PubMed2006

Preparation and characterization of liposomes-in-alginate (LIA) for protein delivery system.

This paper describes the preparation and characterization of a novel drug delivery system for protein, liposomes-in-alginate (LIA) of biodegradable polymers, which is conceived from a combination of the polymer and the lipid-based delivery systems. LIA were prepared by first entrapping bovine serum albumin (BSA), a model protein within multivesicular liposomes (MVLs) by double emulsification process, which are then encapsulated within alginate hydrogel microcapsule, with untrapped BSA which are added during preparation of MVLs. Factors impacting encapsulation efficiency of MVLs are investigated and release of protein from the microcapsules in vitro is studied. At the same time, characterization of MVLs, microcapsules encapsulated protein formulation and integrality analyse of BSA in microcapsules are also studied, with the aim of improving the entrapment efficiency and prolonging release time. It is found that encapsulation efficiency and size of MVLs are affected by the composition and fabrication parameters of LIA. The data also show LIA have high encapsulation efficiency (up to 95%), little chemical change in drug caused by the formulation process, narrow particle size distribution and spherical particle morphology. Drug release assays conducted in vitro indicates that these formulations provide sustained release of encapsulated drug over a period, about 2 weeks.

Alginates↗

PubMed2005

Release property of temperature-sensitive alginate beads containing poly(N-isopropylacrylamide).

The graft copolymer (APN) of alginate and poly(N-isopropylacrylamide) (PNIPAM) were synthesized and APN beads were prepared by dropping the aqueous solution of the copolymer into an aqueous solution of Ca(2+) solution. Alginate chains were employed to play a role in forming beads by electrostatic interactions with a multivalent ion, Ca(2+). Grafted PNIPAM segments were adopted to act as a valve for the pores of the beads, since they exhibit the properties of thermal contraction and expansion. The percent of release of blue dextran from APN beads was higher at 40 degrees C than at 25 degrees C. The difference in the release between two temperatures became more distinguishable when the content of PNIPAM in APN beads is higher. Below lower critical solution temperature (LCST), the expanded PNIPAM would close the pores of the beads, resulting in a lower release rate. Above LCST, the thermally contracted polymer would open the pores, resulting in a higher release rate. The percent of release from APN beads were investigated when the temperature of the release medium is altered. The release rate was relatively low at 25 degrees C. The temperature, however, changed up to 40 degrees C, a marked increase in the release rate was observed. These trends were found to be reproducible when the temperature was repeatedly altered between 25 and 40 degrees C. As a result, a stepwise response to the temperature alteration was obtained.

Acrylic Resins↗

PubMed2026

Alginate-based edible coating incorporating green tea extract for preserving postharvest quality and safety of white mushrooms (Agaricus bisporus).

This study aimed to evaluate the effects of a sodium alginate based edible coating incorporated with green tea extract (GTE) (Camellia sinensis) on the postharvest quality attributes and antimicrobial activity against Listeria monocytogenes in white mushrooms during refrigerated storage. The phenolic profile of GTE was characterized, and its minimum inhibitory concentration (MIC) against L. monocytogenes (1.6 mg/mL) was determined. Sodium alginate coatings, with (ALG-GTE) or without GTE (ALG) at MIC (1.6 mg/mL), were characterized (functional groups, solubility in water, moisture, thickness, water contact angle and color) for their chemical and physical properties. The effects of ALG-GTE coatings on quality parameters (firmness, weight loss, color, pH, sugars and organic acids), enzymatic activity [polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME)], antimicrobial activity against L. monocytogenes (5 log CFU/g), and surface characteristics (3D optical profilometry) were assessed in white mushrooms (Agaricus bisporus) during refrigerated storage (8 days, 4 ± 1 °C, 90-95% RH). The ALG-GTE coatings preserved sugar composition, particularly rhamnose, reduced organic acids accumulation and delayed weight and firmness loss, reduced color changes, and decreased PME activity in coated white mushrooms. L. monocytogenes counts decreased by 1.4 log CFU/g after 1 day, and no viable cells were detected after 2 days (< 1.5 log CFU/g) in ALG-GTE coated white mushrooms. In addition, ALG-GTE coated white mushrooms exhibited smoother surfaces than uncoated samples. These findings highlight the potential of ALG-GTE coatings as a sustainable alternative capable of improving the microbiological safety and delaying the postharvest changes in fresh mushrooms.

Agaricus↗

PubMed2005

Binary immobilization of tyrosinase by using alginate gel beads and poly(acrylamide-co-acrylic acid) hydrogels.

The use of the immobilized and the stable enzymes has immense potential in the enzymatic analysis of clinical, industrial and environmental samples. However, their widespread uses are limited due to the high cost of their production. In this study, binary immobilization of tyrosinase by using Ca-alginate and poly(acrylamide-co-acrylic acid) [P(AAm-co-AA)] was investigated. Maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were determined for the free and binary immobilized enzymes. The effects of pH, temperature, storage stability, reuse number and thermal stability on the free and immobilized tyrosinase were also examined. For the free and binary immobilized enzymes on Ca-alginate and P(AAm-co-AA), optimum pH was found to be 7 and 5, respectively. Optimum temperature of the free and immobilized enzymes was observed to be 30 and 35 degrees C, respectively. Reuse number, storage and thermal stability of the free tyrosinase were increased by a result of binary immobilization.

Agaricales↗

PubMed2006

Preparation of alginate-quaternary ammonium complex beads and evaluation of their antimicrobial activity.

Alginate-quaternary ammonium complex beads with antimicrobial activity were prepared by the reaction of sodium alginate (SA) with 3-(trimethoxysilyl)propyl-octadecyldimethylammonium chloride (TSA) in acid solution, followed by crosslinking with CaCl(2). FTIR spectroscopy analysis showed that the resulting complex was formed mainly through covalent bonds between the hydroxyl groups of SA and the methoxysilyl groups of TSA. The complex beads exhibited a maximum swelling of 20% in water at 37 degrees C and were not hydrolyzed in water during experiments lasting for 30 days. The in vitro antimicrobial activity of the complex beads was evaluated against four species of bacteria and fungi. The test microorganisms were completely eliminated within 20 min when treated with 5% (v/v) complex beads, which showed a wide spectrum of excellent antimicrobial activity. The antimicrobial activity of the complex beads was retained after 10 cycles of washing and drying. The present results indicate that these SA-TSA complex beads are a new type of insoluble cationic polymer that can kill or remove microorganisms in water by mere contact without releasing the reactive agent.

Alginates↗