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PubMedDate not supplied

Assessment of the reproducibility of alginate encapsulation of pancreatic islets using the MTT colorimetric assay.

Radioisotope diffusion experiments demonstrate that alginate/polyaminoacid encapsulation can prevent antibody and cytotoxic cell contact in vitro. The unpredictable outcome of xenotransplantation of encapsulated islets may reflect incomplete encapsulation. We have assessed a cytotoxic/MTT (tetrazolium) assay to test antibody permeability of capsules. Samples of free porcine islet tissue, and islet tissue encapsulated in alginate/poly-L-lysine/alginate microspheres were incubated with fresh autologous pig serum or normal human serum overnight. Cell metabolism was assessed by the MTT assay. Data from eight experiments (10 replicates/experiment) were analyzed using the Mann-Whitney U-test. Values were deemed significant when p < 0.05. Free islets cultured in human serum showed a significant reduction in metabolism when compared with islets cultured in pig serum: percentage reduction 52 +/- 23% (mean +/- SD). The differences in formazan production were significant in all experiments (p < 0.05). Alginate encapsulation of islets or removal of xenoreactive antibodies in human serum by adsorption was shown to prevent the effects of complement-mediated lysis. However, in one of the eight experiments, there was a significant reduction in islet metabolism after exposure of encapsulated porcine islets to human serum. In conclusion, it has been shown that alginate encapsulation can prevent complement-mediated lysis. However, the encapsulation process employed was imperfect and did not prevent complement-mediated lysis of porcine islets in all experiments. The cytotoxicity/MTT assay allows investigation of the permeability of capsules to serum antibodies and could be performed to determine the viability of the islets and the integrity of microcapsules prior to transplantation.

Alginates↗
PubMedDate not supplied

Studies on small (< 300 microns) microcapsules: II--Parameters governing the production of alginate beads by high voltage electrostatic pulses.

The size of microcapsules is a critical parameter in the immunoisolation of islets of Langerhans by microencapsulation. The use of smaller capsules decreases the total implant volume and improves insulin kinetics and oxygen supply. A high voltage electrostatic pulse system was used for the production of small (< 300 microns) alginate beads, the first step of the encapsulation technique. However, islets often protruded from capsules that were too small, further emphasizing the need for a method to control bead size. A study of 7 parameters [electrostatic pulse amplitude (A), duration (D) and wavelength (lambda), pump flow rate (P), needle gauge, alginate viscosity and distance between electrodes] showed that P (r = 0.981, p = 0.003) and lambda (r = 0.988, p = 0.0002) were the principal determinants of bead size. To detect potential interactions between parameters, 270 combinations of different levels of A, D, lambda, and P were studied. A multivariate regression analysis of these data confirmed that P and lambda are the prime determinants of bead size, and showed that a 2-parameter (P, lambda) model could be used to precisely predict bead size (R2 = 0.84), while keeping the application simple. The precision of the predictive model is only slightly improved by the use of additional parameters. The reliability of the data used to elaborate this model was demonstrated (p = 0.6226) by comparing them with a second data set obtained under the same conditions. A third set of experiments confirmed the applicability of the model. This work has major implications on the preclinical application of microencapsulation since it showed that it is possible to predetermine the bead size.

Alginates↗
PubMed2002

Chitosan and sodium alginate-based bioadhesive vaginal tablets.

Metronidazole was formulated in mucoadhesive vaginal tablets by directly compressing the natural cationic polymer chitosan, loosely cross-linked with glutaraldehyde, together with sodium alginate with or without microcrystalline cellulose (MCC). Sodium carboxymethylcellulose (CMC) was added to some of the formulations. The drug content in tablets was 20%. Drug dissolution rate studies from tablets were carried out in buffer pH 4.8 and distilled water. Swelling indices and adhesion forces were also measured for all formulations. The formula (FIII) containing 6% chitosan, 24% sodium alginate, 30% sodium CMC, and 20% MCC showed adequate release properties in both media and gave lower values of swelling index compared with the other examined formulations. FIII also proved to have good adhesion properties with minimum applied weights. Moreover, its release properties (% dissolution efficiency, DE) in buffer pH 4.8, as well as release mechanism (n values), were negligibly affected by aging. Thus, this formula may be considered a good candidate for vaginal mucoadhesive dosage forms.

Alginates↗
PubMed1994

Chitosan and sodium alginate based bioadhesive tablets for intraoral drug delivery.

Bioadhesive tablets for intraoral drug delivery were prepared by directly compressing the drug with a mixture of chitosan and sodium alginate in weight ratios of 4:1, 1:1 and 1:4, and the adhesion and release characteristics of the prepared systems were evaluated in vitro and in vivo. Ketoprofen was used as a model drug. The magnitudes of the adhesion force of chitosan/alginate tablets were observed to be comparable to that of Aftach, which is a typical commercial preparation of an oral mucosal adhesive tablet. Increasing the chitosan content in the tablets resulted in a decrease in the release rate of ketoprofen. When the tablets were administered to the sublingual site of rabbits, ketoprofen from the tablets with chitosan/alginate was rapidly absorbed without an initial sharp peak. Furthermore, the plasma concentration curves for the tablet with a 1:4 chitosan/alginate ratio showed a sustained release 3 h after administration. The data presented suggest that tablets prepared from chitosan and alginate are potential candidates for intraoral drug delivery.

Adhesiveness↗
PubMed2004

Properties of calcium-induced gel beads prepared with alginate and hydrolysates.

Calcium-induced alginate gel beads (Alg-Ca) containing alginate hydrolysate, such as the guluronic acid block (GB), was prepared and the drug release profiles were investigated under simulated gastrointestinal conditions. The addition of GB to Alg-Ca altered its rheological properties. A model drug (hydrocortisone) was incorporated at 78% of its theoretical yield within the dried Alg-Ca containing 5% GB and it was gradually released from the beads in JP XIV 1st medium for disintegration test (pH 1.2), while it was rapidly released with disintegration of the gel matrix in JP XIV 2nd medium (pH 6.8). In contrast, for Alg-Ca containing GB and chitosan, disintegration was not observed in these media and the drug release rate was markedly different. These results demonstrate that the release profiles of drugs incorporated into Alg-Ca can be controlled by adding these polysaccharides.

Alginates↗
PubMed2003

Root growth-promoting activity of unsaturated oligomeric uronates from alginate on carrot and rice plants.

The root elongation activity of unsaturated oligomeric uronates from alginate on carrot and rice plants was investigated. Unsaturated oligomeric uronates were prepared by digesting polymannuronate (PM) and polyguluronate (PG) with an alginate lyase purified from Pseudoalteromonas sp. strain No. 272. The root elongation activity was measured by elongation in length of carrot- and rice-excised root incubated in the B5-medium containing 0.8% agar in the dark. PM and PG showed no activity, but the enzymatic digestion mixtures of PG had promoting activity on roots of both plants at a final concentration of 0.5 mg/ml. The maximum activity was obtained at 0.75 mg/ml. The dependence of activity on degree of polymerization of the uronates was tested and the pentamer was most active, but the mechanism of the action of unsaturated uronates on the cells remains to be solved.

Alginates↗
PubMed2005

Making the most of teams in the mentorship of students.

Community nurses are rightly expected to act as mentors. This role offers students valuable opportunities to gain insight into community care and contributes to the development of future services and the professional growth of individual mentors. There can be tension, however between the demand of nurses' clinical roles and the need to support students. This article identifies ways in which teams can get the most out of mentoring, focusing on the importance of strong clinical leadership and the need for nurses to "own" the mentorship role and to work with other stakeholders. Finally, examples of initiatives from one inner-London trust are offered to demonstrate robust ways of enabling practice-based education.

Community Health Nursing↗
PubMedDate not supplied

Melgisorb: a highly absorbent calcium/sodium alginate dressing.

Alginates have been used in wound care for many years. In recent years alginate dressings have developed to provide an extremely cost-effective way of managing wounds with a moderate to high level of exudate. The dressing gel has traditionally been either soft or firm on removal, but with new technology softness and fast gelling may now be combined with high integrity in a single product. An example of such a product is Melgisorb from Mölnlycke Health Care (the makers of Mepore). Melgisorb is just one dressing in their range of chronic wound care products.

Alginates↗
PubMedDate not supplied

Algosteril calcium alginate dressing for moderate/high exudate.

Algosteril is a new alginate dressing manufactured by Les Laboratoires BROTHIER and distributed by Beiersdorf Medical. It is a natural, pure, non-woven dressing made from calcium alginate fibres. It complements other products in the Beiersdorf wound care family such as Cutinova, Cutifilm and Cutisorb. Algosteril rapidly absorbs and retains wound fluid to form an integral gellified structure, thereby maintaining an ideal moist wound healing environment. It traps and immobilizes pathogenic bacteria in the network of gellified fibres, stimulates macrophage activity and activates platelets, resulting in haemostasis and accelerated wound healing.

Alginates↗
PubMed2005

Making a good impression: (a 'how to' paper on dental alginate).

Approximately 20,000 impressions are made with alginate annually at the University Dental Hospital of Manchester alone, and countless more wherever clinical dentistry is practised. A proportion of these are considered unsatisfactory for clinical use. The reason for these 'failures' is often poor operator technique, rather than an inherent problem of the material. With improved handling of the material and better clinical technique, failures can be avoided. This paper provides an overview of the use of alginate impression material in clinical dentistry.

Alginates↗
PubMed2000

A comparison of hydrofibre and alginate dressings on open acute surgical wounds.

This study aimed to compare the performance of a hydrofibre (Aquacel) and an alginate (Sorbsan) dressing on acute surgical wounds left to heal by secondary intention. A total of 100 patients were prospectively randomised pre-operatively to receive either the hydrofibre or the alginate dressing. Dressing performance was measured at operation, at 24 hours and seven days. Parameters measured included ease of: application and removal of the first dressing; re-application on the first postoperative day; and removal and re-application one week postoperatively. The hydrofibre dressing received higher scores for all of these categories. Patients in this group also experienced less pain (mild or none) on removal of the first dressing and at one week. However, these results did not achieve statistical significance, and should be seen as a trend. Nevertheless, the authors recommend the use of hydrofibre dressings on open acute surgical wounds.

Acute Disease↗
PubMedDate not supplied

Continuous production of extracellular L-glutaminase by Ca-alginate-immobilized marine Beauveria bassiana BTMF S-10 in packed-bed reactor.

L-Glutamine amidohydrolase (L-glutaminase, EC 3.5.1.2) is a therapeutically and industrially important enzyme. Because it is a potent antileukemic agent and a flavor-enhancing agent used in the food industry, many researchers have focused their attention on L-glutaminase. In this article, we report the continuous production of extracellular L-glutaminase by the marine fungus Beauveria bassiana BTMF S-10 in a packed-bed reactor. Parameters influencing bead production and performance under batch mode were optimized in the order-support (Na-alginate) concentration, concentration of CaCl2 for bead preparation, curing time of beads, spore inoculum concentration, activation time, initial pH of enzyme production medium, temperature of incubation, and retention time. Parameters optimized under batch mode for L-glutaminase production were incorporated into the continuous production studies. Beads with 12 x 10(8) spores/g of beads were activated in a solution of 1% glutamine in seawater for 15 h, and the activated beads were packed into a packed-bed reactor. Enzyme production medium (pH 9.0) was pumped through the bed, and the effluent was collected from the top of the column. The effect of flow rate of the medium, substrate concentration, aeration, and bed height on continuous production of L-glutaminase was studied. Production was monitored for 5 h in each case, and the volumetric productivity was calculated. Under the optimized conditions for continuous production, the reactor gave a volumetric productivity of 4.048 U/(mL x h), which indicates that continuous production of the enzyme by Ca-alginate-immobilized spores is well suited for B. bassiana and results in a higher yield of enzyme within a shorter time. The results indicate the scope of utilizing immobilized B. bassiana for continuous commercial production of L-glutaminase.

Alginates↗
PubMed1976

Accuracy of casts produced from alginate and hydrocolloid impression materials.

It is recognized that alginate impression materials have been used to obtain casts from which castings have been fabricated for a number of years. This study indicates that more dimensionally accurate casts are produced from hydrocolloid compared with casts produced from alginate. The most accurate casts were produced from the polyether impression material.

Alginates↗
PubMed1990

Microencapsulation of single, multiple, and zona pellucida-free mouse preimplantation embryos in sodium alginate and their development in vitro.

Preimplantation embryos obtained from immature superovulated B6D2F1 female mice were microencapsulated in sodium alginate singly, in multiples of 2 or 3, or denuded of their zona pellucida. Encapsulated embryos developed in vitro at a rate similar to control embryos. Development of zona pellucida-free embryos was significantly less than that of intact embryos, but there was no difference between encapsulated and non-encapsulated zona pellucida-free embryos. Development of 2- and 4-cell embryos in sodium alginate was independent of cell stage. This report demonstrates the usefulness of a viable, biodegradable embedding material for the microencapsulation of manipulated preimplantation mammalian embryos.

Alginates↗
PubMed2006

Human dental pulp cell culture and cell transplantation with an alginate scaffold.

Many studies on tissue stem cells have been conducted in the field of regenerative medicine, and some studies have indicated that cultured dental pulp mesenchymal cells secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured human dental pulp cells subcutaneously into the backs of nude mice. We found that when beta-glycerophosphate was added to the culture medium, dentin sialophosphoprotein mRNA coding dentin sialoprotein (DSP) was expressed. An increase in alkaline phosphatase, which is an early marker for odontoblast differentiation, was also demonstrated. At 6 weeks after implantation the subcutaneous formation of radio-opaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants. Isolated odontoblast-like cells initiated dentin-like hard tissue formation and scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured dental pulp cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold.

Alginates↗
PubMed2006

Isolated rat dental pulp cell culture and transplantation with an alginate scaffold.

Many studies have been conducted on tissue stem cells in the field of regenerative medicine, and cultured dental pulp mesenchymal cells have been reported to secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured rat dental-pulp-derived cells subcutaneously into the back of nude mice. We found that when beta-glycerophosphate was added to the culture medium, the mRNA of the dentin sialophosphoprotein (DSPP) gene coding dentin sialoprotein (DSP) and dentin phosphoprotein (DPP) was expressed, and an increase in alkaline phosphatase, an early marker of odontoblast differentiation, was also demonstrated. Six weeks after implantation, subcutaneous formation of radiopaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants, and isolated odontoblast-like cells began to form dentin-like hard tissue formation. Scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured rat dental-pulp-derived cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold.

Alginates↗
PubMedDate not supplied

Effect of cellulose derivatives on alginate microspheres prepared by emulsification.

Generally discrete and spherical calcium alginate microspheres with a high drug encapsulation efficiency were readily prepared by an emulsification process. They were found to release drug rapidly. In the present study, co-polymer in the form of cellulose derivatives was added to sodium alginate in an attempt to modify the drug release profiles of the microspheres. The effects of cellulose derivatives on the morphology and drug encapsulation efficiency of the microspheres were also evaluated. The cellulose derivatives increased the degree of agglomeration of the microspheres. Small and spherical microspheres were produced from cellulose derivatives of low viscosity while larger microspheres which tended to be elongated were produced from cellulose derivatives of high viscosity. The drug encapsulation efficiency and the drug release profiles were influenced by the chemical nature of the cellulose derivative as well as its viscosity. The efficiency of drug encapsulation generally increased while the rate of drug release decreased with increasing viscosity of the cellulose derivatives. Less hydrophilic cellulose derivatives such as methyl cellulose and hydroxypropylmethyl cellulose were found to increase the efficiency of encapsulating sulphaguanidine, while more hydrophilic cellulose derivatives such as hydroxypropyl cellulose and carboxymethyl cellulose had the opposite effect. Among the cellulose derivatives used, only hydroxypropyl cellulose retarded the drug release of the microspheres.

Alginates↗
PubMedDate not supplied

Retention of trypsin activity in spermine alginate microcapsules.

We have previously shown virus particles encapsulated in aqueous spermine alginate constructs retain immunogenicity and infectivity both in vitro and in vivo. However, because virions are complex structures with multiple reinforcing components, it was uncertain if isolated single proteins would retain functional integrity when similarly encapsulated. To examine this question trypsin, used as a model protein, was blended with aqueous sodium alginate and the blend was dispersed as fine droplets in aqueous spermine hydrochloride to generate self-assembling, trypsin-containing microcapsules. Trypsin was assayed spectrophotometrically for retention of enzymatic activity using N-alpha-p-tosyl-L-arginine methyl ester as substrate. Neither of the encapsulating reagents alone inhibited enzyme activity. Enzyme that escaped capture was assayed directly in the manufacturing supernatant. In mass balance studies we found that about 20-30% of activity was retained in intact capsules with the remainder resident in the aqueous manufacturing supernatant and washes. However, we found that the capsule wall appeared to inhibit enzyme activity by retarding substrate diffusion into and product diffusion out from the capsules, as evidenced by an increase in activity on lysis. Thus, it is clear that a single protein, as represented by trypsin, can retain functional integrity when encapsulated in this all aqueous system.

Alginates↗