Barium-cross-linked alginate beads: a simple,one-step method for successful immunoisolated transplantation of islets of Langerhans

Transplantation of xenogeneic islets in immunoisolating membranes may solve the problems of the availability of human donor organs and long-term immunosuppression. Alginates are widely used for microencapsulation of isolated islets. This study presents data of a new method in which alginate was cross-linked with barium ions. In the perifusion experiment microencapsulated rat islets showed a biphasic insulin release with a short delay of the first phase. During static glucose challenge the insulin release ranged from 40% to 70% compared to free floating controls. In 3 of 11 diabetic mice, transplantation of 800 barium-alginate-bead encapsulated rat islets resulted in a non-fasting normoglycaemia at least up to 70 days. In the same model, transplantation of 3000 encapsulated porcine islets resulted in 6 of 10 recipients in normoglycaemia up to day 70, while 3 animals were still normoglycaemic on day 100. On day 21 after transplantation of encapsulated rat and porcine islets and intraperitoneal glucose tolerance test revealed rapid glucose assimilation in both groups. Histological examination demonstrated well-preserved islets at the end of the experiments. Immunohistological B-cell staining revealed the absence of recruitment of -cells in the recipient's own pancreas. The barium-alginate microencapsulation method represents a simple one-step method for effective immunoisolated transplantation of large-scale islet preparations.     

藻酸盐影响庆大霉素对铜绿假单胞菌生物被膜渗透性及杀菌活性的研究

目的:探讨藻酸盐对氨基糖苷类抗生素庆大霉素对铜绿假单胞菌的渗透性及杀菌活性的影响。方法:选择经典突变黏液菌株(PDO300)和标准非黏液菌株(PAO1)作为实验菌株,PIA平板观察细菌的黏液表型;色氨酸反应法测定其胞外多糖蛋白复合物的产量;NCCLS推荐的琼脂稀释法测定两菌株对庆大霉素的MIC;分别检测两菌株在浮游状态和生物被膜状态对庆大霉素的敏感性;"三明治夹心法"检测两菌株生物被膜状态下对庆大霉素的渗透性。结果:PDO300表现出明显的黏液表型,较PAO1的多糖蛋白复合物产量明显增高。两者对庆大霉素的MIC均为2μg/ml,浮游状态下两者对20μg/ml庆大霉素敏感性一致。生物被膜24h的渗透率PAO1为90%,而PDO300为50%。PDO300对20μg/ml庆大霉素的敏感性明显降低。结论:藻酸盐可以显著降低庆大霉素对铜绿假单胞菌生物被膜的渗透性及杀菌活性。     

Evaluation of different RGD ligand densities in the development of cell-based drug delivery systems

Background: The inclusion of the tripeptide Arg-Gly-Asp (RGD) in otherwise inert biomaterials employed for cell encapsulation has been observed to be an effective strategy to provide the immobilized cells with a more suitable microenvironment.

Purpose: The objective of this study was to determine the impact of different RGD densities on the behavior of baby hamster kidney (BHK) fibroblasts able to secrete vascular endothelial growth factor (VEGF) encapsulated in alginate microcapsules.

Methods: Alginate was modified by varying the concentration of RGD peptides in the coupling reaction. After obtaining four different types of alginate, cells were encapsulated in alginate-poly-l-lysine-alginate (APA) microcapsules.

Results and discussion: The results obtained after viability, cell proliferation and VEGF secretion assays showed that the inclusion of RGD in alginate enhances the functionality of immobilized cells, obtaining the highest values with the intermediate RGD density.

Conclusion: These results put in evidence that alginate modification influences the behavior of immobilized cells but even more that the employed density of the tripeptide is of crucial importance, obtaining in some cases even excessive activity of the encapsulated cells.     

Cranioplasty Using Presurgically Fabricated Presterilised Polymethyl Methacrylate Plate by a Simple,Cost-Effective Technique on Patients With and Without Original Bone Flap: Study on 29 Patients

Objectives

The purpose of the study was to assess the clinical effectiveness of presurgically fabricated pre-sterilized polymethyl methacrylate (PMMA) plate as a cranioplasty material.

Materials and Methods

The study group consisted of 29 patients with skull defect following decompressive craniectomy. Some patients had their original bone flap preserved and some were without it. In either group pre-sterilized prefabricated PMMA plate was used. On each visit, patients were clinically assessed; CT scans were taken in immediate follow up period but if needed more films were taken in subsequent follow ups. Post-op complications that include infection, post-op hematoma, chronic pain, aesthetic, biocompatibility, post-op dimensional changes of prosthesis were evaluated.

Results

Mean follow up was 7 1/2 months. Five patients developed swelling and pain in the subsequent follow ups. One patient was treated conservatively with antibiotics. Tapping was performed in couple of patients. Surgical evacuation of hematoma was performed in one patient. Of the five infected plates, one demanded removal from the patient. One complained of chronic pain. Post-op follow up assessed clinically and by CT scan confirmed good aesthetic result, biocompatibility and dimensional stability of prosthesis.

Conclusion

The result of this study support the view that the use of prefabricated pre-sterilized PMMA plate as cranioplasty material is a simple, reliable, convenient way that brings acceptable function and aesthetics to patients who underwent decompressive craniectomy, in an inexpensive way.     

海藻酸钠微球的制备及其在药物载体中的应用进展

海藻酸钠因其具有独特的物理、化学及生物学特性,目前已成为十分理想的制备缓释和控释制剂的天然高分子材料,海藻酸钠载药微球作为新型缓控释制剂也受到越来越多的关注。现综述海藻酸钠微球的制备方法,释药机制及其在药物载体研究中的应用进展。     

藻酸盐敷料结合微波辐射促进肛瘘术后创面愈合的疗效观察

目的观察藻酸盐敷料结合微波辐射促进肛瘘术后创面愈合的临床疗效。方法将56例肛瘘术后患者随机分为治疗组和对照组各28例;治疗组采用藻酸盐敷料结合微波辐射,对照组用凡士林油纱条换药。观察两组肛瘘术后创面疼痛程度、渗液量及创面愈合时间。结果治疗组较对照组术后创面疼痛轻、渗液量少、愈合快（P〈0.05）。结论藻酸盐敷料结合微波辐射能减轻肛瘘术后创面疼痛,减少渗液量,促进愈合。     

Calcium alginate microparticles for oral administration: I: effect of sodium alginate type on drug release and drug entrapment efficiency

The natural polymers alginate and chitosan were used for the preparation of controlled release nicardipine HCl gel microparticles. The effect of the mannuronic/guluronic acid content and the alginate viscosity on the prolonged action of the microparticles, which were prepared with different types of alginates, were investigated. The mean particle sizes and the swelling ratios of the microparticles were also determined. The in vitro release studies were carried out with a flow-through cell apparatus in different media (pH 1.2, 2.5, 4.5, 7 and 7.5 buffer solutions). The release of nicardipine was extended with the alginate gel microparticles prepared with guluronic acid rich alginate. After the determination of the most appropriate alginate type, the effect of alginatechitosan complex formation was studied on the release pattern of drug incorporated. It was observed that the alginate-chitosan complex formation reduced the erosion of the alginate-chitosan matrix at pH 7-7.5. The release of drug from the chitosan-alginate gel microparticles took place by both diffusion through the swollen matrix and relaxation of the polymer at pH 1.2-4.5     

Formation of alginate microspheres produced using emulsification technique

This study investigated the formative process of alginate microspheres produced using an emulsification technique. The alginate microspheres were produced by cross-linking alginate globules dispersed in a continuous organic phase using various calcium salts: calcium chloride, calcium acetate, calcium lactate and calcium gluconate. The size, shape, drug content and Ca²⁺ content of the microspheres were evaluated. The tack, viscosity and pH of the calcium salt solution and percentage of Ca²⁺ partitioned into the organic phase were determined. Microscopic examination of the test emulsion at various stages of the emulsification process was also carried out. The propensity of cross-linking reaction was found to be dependent on successful collision between alginate and calcium salt globules. Examination of the characteristics of microspheres indicated that the formed microsphere was a resultant product of alginate globule clustering. The growth propensity of microspheres was promoted by the higher rate and extent of cross-linkage which was governed by the pH, tack and/or Ca²⁺ content of the cross-linking solution, as well as the dissociation constant and diffusivity of the calcium salt. Overall, the amount of free Ca²⁺ cross-linked with alginate in the formed microspheres was in the following order: calcium acetate > calcium chloride + calcium acetate > calcium chloride + calcium gluconate; calcium chloride + calcium lactate > calcium chloride. In microencapsulation by emulsification, the mean size of the microspheres produced can be modified by varying the tack, pH and Ca²⁺ content of the cross-linking solution and through the use of a combination of calcium salts. The shape of the microspheres produced was, nonetheless, unaffected by the physicochemical properties of the cross-linking solution.