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PubMed2005

Removal of organic compounds by alginate gel beads with entrapped activated carbon.

The adsorption of alginate gel (AG) beads and AG with activated carbon entrapped (AG-AC) beads prepared using different types of metal ions were investigated by measuring the removal of several organic compounds with different charges and size. AG-AC beads prepared in a CaCl2 solution adsorbed strongly positively charged compounds as well as electrically neutral and low molecular weight compounds such as p-chlorophenol. However, a high molecular weight humic acid was not adsorbed by AG-AC. The AG-AC selectively adsorbed p-chlorophenol from a humic acid solution. The adsorption capacity obtained from the adsorption isotherm of AC entrapped in AG was compared with that of AC. The AG-AC beads prepared in a solution of FeCl3 were able to specifically adsorb negatively charged gallic acid. Thus, entrapping AC into AG resulted in the selective adsorption.

Adsorption↗
PubMed2005

Internal mass transfer effect on biodegradation of phenol by Ca-alginate immobilized Ralstonia eutropha.

Phenol biodegradation by free and Ca-alginate immobilized Ralstonia eutropha was performed in batch system. Optimum initial pH and temperature were determined as 7 and 30 degrees C, respectively for free cells, while a wide pH and temperature range were obtained for immobilized cells. Phenol had a strong inhibitory effect on the microbial growth and Haldane model was used to describe the substrate inhibition. Model parameters were determined as mumax=0.89 h(-1), KS=55.11 mg dm(-3) and KI=257.94 mg dm(-3) by non-linear regression analysis. The effective diffusion coefficient of phenol in immobilized particles was calculated. For this purpose, using biodegradation rates experimental effectiveness factors were determined for different sized immobilized particles. The Thiele modulus was evaluated from experimental effectiveness factors. Then the average effective diffusion coefficient was calculated as 1.21 x 10(-7)cm2 s(-1). These results showed that intraparticle diffusion resistance was important for this system and could not be ignored.

Alginates↗
PubMed2006

Enhanced Overhauser contrast in proton-electron double-resonance imaging of the formation of an alginate hydrogel.

Proton-electron double-resonance imaging (PEDRI) was recently employed to monitor the process of formation of a calcium alginate hydrogel at a field of 16mT. Here, under the same experimental conditions, images obtained through this technique are compared to images obtained by conventional T(2)-weighted method. The results confirm that the image contrast obtained using PEDRI, thanks to the Overhauser effect, exhibits an improved sensitivity with respect to changes in water mobility as previously suggested in the literature. Furthermore, by increasing the echo time interval for the T(2)-weighted images, important features of the gelling dynamics obtained via PEDRI could not be reproduced.

Alginates↗
PubMed2006

Synergistic effect of IGF-1 and OP-1 on matrix formation by normal and OA chondrocytes cultured in alginate beads.

OBJECTIVE: Growth factor therapy may be useful for stimulation of cartilage matrix synthesis and repair. Thus, the purpose of our study was to further understand the effect of combined insulin-like growth factor-1 (IGF-1) and osteogenic protein-1 (OP-1) treatment on the matrix synthesized by human adult normal and osteoarthritic (OA) chondrocytes. DESIGN: Chondrocytes were isolated post-mortem from articular cartilage from tali of normal human donors and femoral condyles of OA patients undergoing knee replacement surgery. Cells were cultured in alginate beads for 21 days in four experimental groups: (1) "mini-ITS" control; (2) 100 ng/ml IGF-1; (3) 100 ng/ml OP-1; (4) IGF-1+OP-1, each at 100 ng/ml. Beads were processed for histological (Safranin O and fast green), morphometrical and immunohistochemical (aggrecan, decorin, type I, II, VI, and X collagens, and fibronectin accumulation) analyses. RESULTS: Histology showed that IGF-1 alone did not induce substantial matrix production. OP-1 alone caused a considerable matrix formation, but the highest matrix accumulation by normal and OA chondrocytes was found when OP-1 and IGF-1 were added together. Morphometrical analysis indicated larger matrices produced by OA chondrocytes than by normal cells under the combined treatment. All tested matrix proteins were more abundant in the combination group. Type X collagen was detected only under the combined OP-1 and IGF-1 treatment and was present at very low levels. Type I collagen was found only in OA chondrocytes. CONCLUSIONS: The results obtained in the current study suggest that combined therapy with IGF-1 and OP-1 may have a greater potential in treating cartilage defects seen in OA than use of either growth factor alone.

Alginates↗
PubMed2004

Viability of equine articular chondrocytes in alginate beads exposed to different oxygen tensions.

Ischaemia and reperfusion are suspected to alter chondrocyte metabolism. Here, we studied the effects of three oxygen (O2) tensions on the viability of equine articular chondrocytes isolated from the cartilage of the distal interphalangeal joint of horses. Chondrocytes were cultured in alginate beads under 1%, 5% or 21% gas phase O2 concentration for 14 days, cellular growth kinetics were measured (n=6), and the cells were observed by light microscopy after staining for necrotic and apoptotic cell detection. For information about the metabolic status, the intracellular adenosine triphosphate (ATP) content was measured. The number of chondrocytes remained stable for the first eight days, then decreased especially at 1% and 21% O2. At 21% O2, normal cells decreased and necrotic cells increased at the end of the 14 day-period. No significant variations were found at 5% O2 except for a decrease in necrotic cells at day 14. Most apoptotic cells were found at 1% O2 from days 5 to 11, and normal cells decreased during the same period. But an unexpected increase in normal cells and decrease in apoptotic cells were observed at day 14. The intracellular ATP content remained stable. It was concluded that, in a three-dimensional culture model of equine articular chondrocytes, O2 tension affected the viability of the cells after an 11-day period, with the most important effects observed at 21% and 1% O2 conditions.

Alginates↗
PubMed2005

Sorptive removal of trivalent and hexavalent chromium from binary aqueous solutions by composite alginate-goethite beads.

In this study, the removal of hexavalent and trivalent chromium ions from binary aqueous solutions by composite alginate-goethite beads was investigated in a batch mode. Equilibrium sorption experiments were carried out at different temperatures and pH values. The data were correlated with Langmuir and Freundlich equations. The thermodynamic parameters calculated were: change in free energy, in enthalpy, in entropy and the heat of adsorption. The influence of mixing rate, sorbent concentration and sorbent particle size was studied at kinetic runs. The effective diffusion coefficients were evaluated by employing the homogeneous diffusion model and the shrinking core model for hexavalent and trivalent chromium, respectively. Desorption experiments were conducted by employing various eluants showed that the loaded material could be regenerated satisfactorily.

Absorption↗
PubMed2006

Nickel adsorption by magnetic alginate microcapsules containing an extractant.

The adsorption of heavy metals on biomaterials was investigated by studying the potential of alginate microcapsules containing an extractant (Cyanex 272) and magnetic nanoparticles (gamma-Fe2O3) for the adsorption of nickel (II) from aqueous solutions. A two-stage kinetics behaviour was observed with 70% of the maximum sorption capacity achieved within 8 h. An increase in nickel removal with increase in pH occurred, the maximum uptake capacity being around 0.42 mmol g-1 at pH 8. The adsorption isotherm (pH about 5.3) was obtained in a wide range of initial nickel concentrations; the experimental data were fitted by a Langmuir model and the qmax value was estimated to be 0.52 mmol g-1. Moreover, including magnetic particles in the microcapsules allowed easy isolation of the beads from the aqueous solutions after the sorption process. Magnetic microcapsules are then suitable for the development of efficient biosorbents for removal and recovery of heavy metals from wastewater using magnetic separation.

Adsorption↗
PubMed2003

A fluorescence study of the interactions between sodium alginate and surfactants.

The interactions between the polysaccharide alginate with charged ionic surfactants (anionic and cationic) in aqueous solution have been investigated using pyrene as a photophysical probe. Static fluorescence determinations have been used to obtain information about the new microenvironments arising by these interactions. Micropolarity studies using the I(1)/I(3) ratio of the vibronic bands and I(E)/I(M) ratio between the excimer and monomer emissions of pyrene shows the formation of hydrophobic domains. The interactions between the natural polyelectrolytes and the oppositely charged surfactants lead to the formation of pre-micelles at surfactant concentrations lower than the CMC of the surfactants. The aggregation process is assumed to be due to electrostatic attraction. On the other side, systems containing an anionic surfactant do not show the same behaviour at low concentrations.

Alginates↗
PubMed2002

Purification of a bacterial pullulanase on a fluidized bed of calcium alginate beads.

Pullulanase from Bacillus acidopullulyticus was purified on a packed bed and a fluidized bed of calcium alginate beads. The binding of enzyme activity to the medium was found to follow Langmuir isotherm pattern. The maximum binding capacity was 1476 U ml(-1) matrix and the dissociation constant was 142 U ml(-1). The dynamic binding capacities at 5% breakthrough in the packed and fluidized beds were 472 U ml(-1) and 644 U ml(-1), respectively. In the packed bed as well as the fluidized bed, an activity recovery of more than 95% with fold purification in the range of 46-59 was observed. The elution with a competitive inhibitor, viz. maltose, and high-fold purification indicate an affinity-based process. The purification process worked equally well with columns of bed volumes of 3.8 and 10 ml.

Adsorption↗
PubMed1994

Endoscopic treatment of vesicoureteral reflux with a chondrocyte-alginate suspension.

Injection of polytetrafluoroethylene (Teflon) or collagen has been used in the endoscopic treatment of vesicoureteral reflux. Although the principle of an endoscopic treatment is valid, there are concerns regarding the long-term safety and effectiveness of these substances. In search of a different injectable material we conducted experiments using chondrocytes in a biodegradable polymer solution for the treatment of vesicoureteral reflux in an animal model. Reflux was created in 4 mini-pigs and confirmed with a cystogram. Cartilage was obtained from the auricular surface of each animal. Chondrocytes were harvested and expanded in vitro. The cells were individually quantitated and concentrated to 40 million cells per cc. The cell suspensions were mixed with a sodium alginate and calcium sulfate solution. Each pig was injected unilaterally in the subureteral region with the autologous chondrocyte suspension. The opposite ureter served as an internal control in all animals. Cystograms showed resolution of reflux in the treated side and persistence of reflux in the opposite untreated side in each instance. Excretory urograms revealed no evidence of obstruction. Histological examination of the subureteral region demonstrated cartilage. Autologous chondrocytes can be readily harvested, expanded in vitro and injected cystoscopically. The cells survive and form a cartilage nidus that is nonantigenic. This system is able to correct reflux without any evidence of obstruction.

Alginates↗
PubMed2002

Removal of ammonium and phosphorus ions from synthetic wastewater by the microalgae Chlorella vulgaris coimmobilized in alginate beads with the microalgae growth-promoting bacterium Azospirillum brasilense.

Coimmobilization of the freshwater microalga Chlorella vulgaris in alginate beads with the microalgae growth-promoting bacterium Azospirillum brasilense under semi-continuous synthetic wastewater culture conditions significantly increased the removal of ammonium and soluble phosphorus ions compared to immobilization of the microalgae alone. In continuous or batch cultures removal of these ions followed a similar trend but was less efficient than in semi-continuous culture. It is proposed that coimmobilization of a microalgae with microalgae growth-promoting bacteria can serve as a tool in devising novel wastewater treatments.

Alginates↗
PubMed2003

Removal of chromium and reduction of toxicity to Microtox system from tannery effluent by the use of calcium alginate beads containing humic acid.

Removal of chromium (Cr) from tannery effluents by recovery of metal also reduces the ecotoxicological impact. To develop such a process, columns packed with calcium alginate (CA) beads with or without humic acid (HA) have been used as an adsorbent and tannery effluent was passed through it. Concentration of Cr in beads and in different fractions collected after adsorption was measured. Change in total organic carbon content during the process was also noticed. The fractions were also tested for toxicity towards Microtox assay. EC(50) values were determined with the help of Microtox analyser 500. Data showed that the CA beads along with HA could be effectively utilised in removal of 54% Cr and also in reducing the toxicity (EC(50) (%) in 5 min=>100 in fractions collected after 72 h).

Adsorption↗
PubMed2004

Boar spermatozoa encapsulated in barium alginate membranes: a microdensitometric evaluation of some enzymatic activities during storage at 18 degrees C.

The customary dilution of boar semen for subsequent artificial insemination (AI) procedures damages the cell membrane of spermatozoa, resulting in a loss of enzymes and other cytoplasmic contents and acrosomal reactions. We encapsulated non-diluted boar semen in barium alginate membranes to optimize AI procedures and to improve the functional integrity of spermatozoal membranes during storage. The percentage of non-reacted acrosomes (NRA) and measurements of enzyme leakage (cytochrome c oxidase (COX), lactate dehydrogenase (LDH), and glucose-6-phosphate dehydrogenase (G6PDH)) were used as indices of the functional status of diluted, unencapsulated and encapsulated spermatozoa, stored for 72 h at 18 degrees C. Enzymatic activity was assessed in situ by microdensitometry, and non-reacted acrosomes were microscopically determined by staining. The percentage of acrosome integrity and the intracellular enzymatic activities during storage were different for unencapsulated and encapsulated semen. Semen dilution caused a rapid decline in enzymatic activities and concomitant acrosomal reactions. Encapsulated spermatozoa had significantly higher acrosome integrity (77% versus 55%; P < 0.01 after 72 h) and an overall higher in situ enzymatic activity. For cytochrome c oxidase and lactate dehydrogenase the greatest differences between encapsulated and unencapsulated spermatozoa were present after 72 h whereas for glucose-6-phosphate dehydrogenase significant differences were found within 24h of storage. The encapsulation process maintains a better preservation environment for boar spermatozoa and could be a promising, innovative technique to improve storage of these cells.

Acrosome Reaction↗
PubMed2000

Controlled release of swine semen encapsulated in calcium alginate beads.

A quick and successful encapsulation method of swine spermatozoa is described: hydroxypropylmethylcellulose and calcium chloride were added to the sampled ejaculate swine sperm (sperm-rich fraction: creamy white) and then this suspension was dropped into an aqueous solution of sodium alginate. In order to obtain different capsule thicknesses, different calcium chloride concentrations were used. The influence of different formulations on in vitro spermatozoa release behavior and on the mechanical properties has been studied. In vitro sperm kinetics (motility and average velocity) have been determined. The results obtained from motility and average velocity tests of treated seminal material are promising, especially if the difficulty of preservation of swine spermatozoa compared to bovine sperm is considered. The different membranes obtained from the different calcium concentrations have had an influence on mechanical properties and on the release profile of spermatozoa from the capsules, and therefore, it is possible to modulate the release rate of the cells.

Alginates↗
PubMed1999

The effect of alginate and hyaluronate on the viability and function of immunoisolated neonatal rat islets.

Recent observations suggest that the extracellular matrix plays a role as regards the viability and morphological integrity in long-term culture of Langerhans islets. For the present study we encapsulated neonatal rat islets without extracellular matrix (WEM), with alginate solution (AL) and with hyaluronate solution (HY) into cuprophane hollow fibers. Function was tested after week 1 and 5. The insulin release of WEM encapsulated islets decreased significantly during the culture period. In contrast to this, AL and HY embedded islets had stable secretion values throughout the whole cultivation. Histological examination confirmed that viability of HY and of AL embedded islets differed significantly from that of WEM encapsulated islets. Furthermore, HY seems to be a more advantageous environment to immunoisolated islets than AL. Both the insulin secretion values and the viability of HY embedded islets were higher than of AL embedded islets. We conclude that an extracellular matrix is important for immunoisolated islets, to maintain their function and morphological integrity and that HY is especially suitable for this application.

Alginates↗
PubMed2000

Using a green fluorescent protein gene-labeled p-nitrophenol-degrading Moraxella strain to examine the protective effect of alginate encapsulation against protozoan grazing.

A gfp-labeled p-nitrophenol-degrading Moraxella strain G21 was used to study grazing of a Tetrahymena thermophila strain in liquid medium. This allowed visualization of the feeding process. Under an epifluorescent microscope, individual G21 fluorescent cells could be seen in vacuoles within the protozoans. Most of the G21 cells appeared to be lysed by T. thermophila and green fluorescent protein released from the bacteria yielded brightly fluorescent food vacuoles inside the protozoans, Examination of population dynamics of a mixed culture of T. thermophila and Moraxella sp. G21 showed that the protozoan reduced the bacterial density from 7.6 to 5.8 log CFU/ml in 2 days. Encapsulating the bacteria in alginate prevented grazing by the protozoans and the density of G21 cells in the beads increased steadily from about 8.3 to 8.9 log CFU/ml in 15 days regardless of the presence of the protozoans.

Alginates↗
PubMed2001

Experimental determination of the theophylline diffusion coefficient in swollen sodium-alginate membranes.

In this paper attention is focused on the determination of the drug diffusion coefficient in a swollen polymeric membrane referring to a recent mathematical model (linear model). The main advantage deriving from its use is that, despite its analytical nature and its ability to account for the most important aspects characterising a permeation experiment, it can also be applied in the case of thick membranes. To check the model reliability, a comparison is made with a more complex numerical model and with a largely employed model in terms of data fitting quality. To this purpose, particular care is devoted to the experimental and theoretical tools employed to calculate the auxiliary parameters required by the three models, and with the aim of getting a drug diffusion coefficient value as accurate as possible. Theophylline was chosen as model drug owing to its wide employment in the pharmaceutical field. Membranes were prepared with sodium alginates hydrogels at three different polymer concentrations. The present analysis demonstrates the reliability of the linear model and reveals that the theophylline diffusion coefficient is not significantly affected by the polymer concentration. Indeed, such a parameter is reflected in different membrane thicknesses rather than in different mesh sizes of the polymeric network.

Alginates↗
PubMed2000

Glutaraldehyde crosslinked sodium alginate beads containing liquid pesticide for soil application.

This paper presents experimental results on the successful encapsulation of a natural liquid pesticide 'neem (Azadirachta Indica A. Juss.) seed oil' hereafter designated as NSO, using sodium alginate (Na-Alg) as a controlled release (CR) polymer after crosslinking with glutaraldehyde (GA). The NSO-containing beads have been prepared by changing the experimental variables such as the extent of crosslinking and the amount of loading in order to optimize the process variables. The absence of chemical interactions between active ingredients and polymer as well as crosslinking agent was confirmed by FTIR spectral measurements. The SEM data indicated that the structure of the walls of the beads are smooth and nonporous. The swelling results indicated that swelling of the polymeric beads decreases with increasing exposure time to the crosslinking agent. However, no significant variation in swelling was observed with different amounts of NSO loading. In order to understand the crosslinkability and its effect on the NSO release patterns of the beads, an attempt was made to calculate the molar mass between crosslinks using the Flory-Rehner equation. The release data have been fitted to an empirical equation to estimate the kinetic parameters.

Alginates↗