PubMed · 11199630
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R Giordano. Impression materials: basic properties.. https://pubmed.ncbi.nlm.nih.gov/11199630/
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Among the different approaches to achieve protein delivery, the use of polymers, specifically biodegraded, holds great promise. In this work, a new microsphere delivery system composed of alginate microcores surrounded by a biodegradable poly-DL-lactide-poly(ethylene glycol (PELA) was designed to improve the loading efficiency and stability of proteins. Alginate was solidified by calcium (MS-1), polylysine (MS-2) and chitosan (MS-3), respectively, to form different microcores. Human Serum Albumin (HSA), used as a model protein, was efficiently entrapped within the alginate microcores using a high-speed stirrer and then microencapsulated into PELA copolymer using a w/o/w solvent extraction method. DSC analysis of the microspheres revealed the efficient encapsulation of the alginate microcores, while the microcores were dispersed in the PELA matrix. SDS-PAGE results showed that HSA kept its structural integrity during encapsulation and release procedure. Microspheres were characterized in terms of morphology, size, loading efficiency, in vitro degradation and protein release. The degradation profiles were characterized by measuring the loss of microsphere mass, the decrease of polymer intrinsic viscosity and the reduction of PEG content of PELA coat. The release profiles were investigated from the measurement of protein presented in the release medium at various intervals. The results were that the degradation rate of these core-coated microspheres was MS-2>MS-1>MS-3. The extent of burst release from the core-coated microspheres in the initial protein release was lower than the 27% burst release from the conventional microspheres. In conclusion, the work presents a new approach for macromolecular drugs (such as protein, peptide drugs) delivery. The core-coated microspheres system may have potential use as a carrier for drugs that are poorly absorbed after oral administration.
Immobilization of salt-tolerant yeasts considerably decreases the total time required for the flavour development in soy-sauce processes. For immobilization of cells, alginate gel is mostly used as support material. However, alginate is not very suitable for use in soy-sauce processes because alginate is sensitive to abrasion and chemically unstable towards the high salt content of the soy-sauce medium. In contrast, a newly developed polyethylene-oxide gel seems to be more suitable, but this gel has not been used so far for flavour production in a bioreactor with a high salt content. Therefore, this gel was applied with immobilized salt-tolerant yeasts in a continuous stirred-tank reactor, containing more than 12.5% (w/v) salt. In this reactor, the polyethylene-oxide gel particles did not show any abrasion for several days, while alginate gel beads were already destroyed within 1 day. In addition, the polyethylene-oxide gel particles with immobilized salt-tolerant yeasts Candida versatilis and Zygosaccharomyces rouxii showed a good flavour production. From this work, it was concluded that the application of polyethylene-oxide gel in long-term soy-sauce processes is attractive in the case the sticking together of polyethylene-oxide gel particles can be controlled.
Porcine neonatal pancreatic cell clusters (NPCCs) may be a suitable source of insulin producing tissue for transplantation in diabetic patients. The possible beneficial effect of serum on maturation of NPCCs in vitro is difficult to achieve because of cell clumping, which can be avoided by immobilization in alginate hydrogel matrix. Collagenase treated pancreata, cultured for 4 days, formed NPCCs that were embedded in alginate cross-linked with CaCl2 and cultured in modified Ham's F10 medium with 10% fetal calf serum (FCS) for 10 days. NPCCs cultured as suspension in F10+ with 0.5% bovine serum albumin or with 10% FCS were used as control. To prevent the aggregation when cultured with serum, NPCCs were kept as a very diluted suspension. At the beginning and end of the culture, samples were taken for insulin and DNA content and immunostained for beta and non-beta cells. The culture of NPCCs immobilized in alginate resulted with 3-fold increase in insulin content and 9-fold increase in insulin/DNA ratio. Histology revealed evident increase of number of insulin- and other hormone-positive cells compared with the control. Even though 2 weeks in culture resulted in impaired glucose-induced insulin release, the amount of insulin secreted by clusters cultured in the presence of serum was 4-fold higher than in serum-free conditions. After transplantation, NPCCs retrieved from alginate reversed hyperglycemia similarly to NPCCs cultured in standard conditions. In conclusion, this study shows the feasibility of in vitro immobilization of NPCCs in alginate three-dimensional matrix, allowing cell clusters to be cultured at least two times higher density compared with culture in suspension.