水凝胶联合藻酸盐银敷料在面部深Ⅱ度烧伤创面治疗中的应用研究

目的 探讨水凝胶联合藻酸盐银敷料在面部深Ⅱ度烧伤治疗中的应用效果.方法 选取2017年2月至2020年2月新疆维吾尔自治区人民医院烧伤创面修复科收治的82例面部深Ⅱ度烧伤患者,使用随机数字表法将患者分为干预组和对照组,每组各41例.2组患者均于治疗前根据临床操作规范去除创面失活组织,0.9％氯化钠溶液冲洗创面后使用无菌...     

Chondrogenesis of hMSC in affinity-bound TGF-beta scaffolds

Herein we describe a bio-inspired, affinity binding alginate-sulfate scaffold, designed for the presentation and sustained release of transforming growth factor beta 1 (TGF-β1), and examine its effects on the chondrogenesis of human mesenchymal stem cells (hMSCs). When attached to matrix via affinity interactions with alginate sulfate, TGF-β1 loading was significantly greater and its initial release from the scaffold was attenuated compared to its burst release (>90%) from scaffolds lacking alginate-sulfate. The sustained TGF-β1 release was further supported by the prolonged activation (14 d) of Smad-dependent (Smad2) and Smad-independent (ERK1/2) signaling pathways in the seeded hMSCs. Such presentation of TGF-β1 led to hMSC chondrogenic differentiation; differentiated chondrocytes with deposited collagen type II were seen within three weeks of in vitro hMSC seeding. By contrast, in scaffolds lacking alginate-sulfate, the effect of TGF-β1 was short-term and hMSCs could not reach a similar differentiation degree. When hMSC constructs were subcutaneously implanted in nude mice, chondrocytes with deposited type II collagen and aggrecan typical of the articular cartilage were found in the TGF-β1 affinity-bound constructs. Our results highlight the fundamental importance of appropriate factor presentation to its biological activity, namely - inducing efficient stem cell differentiation.     

Young porcine endocrine pancreatic islets cultured in fibrin and alginate gels show improved resistance towards human monocytes

Aim

To investigate the protective function of alginate and fibrin gels used to embed porcine endocrine pancreatic islets towards human monocytes.

Methods

Groups of 200 islet equivalents from young pigs were embedded in either a fibrin or in an alginate gel, and as a control seeded in tissue culture polystyrene (TCPS) well plates. The islet cultures were incubated with 2 × 10⁵ human monocytes for 24 h. In addition, both islets and monocytes were separately cultured in TCPS, fibrin and alginate. Islet morphology, viability and function were investigated as well as the secretion of cytokines TNFα, IL-6, and IL-1β.

Results

When freely-floating in TCPS, non-encapsulated islets were surrounded by monocytes and started to disperse after 24 h. In fibrin, monocytes could be found in close proximity to embedded islets, indicating monocyte migration through the gel. In contrast, after 24 h, few monocytes were found close to islets in alginate. Immunofluorescence staining and manual counting showed that integrin expression was higher in fibrin-embedded islet cultures. A TUNEL assay revealed elevated numbers of apoptotic cells for islets in TCPS wells compared to fibrin and alginate cultures. Insulin secretion was higher with islets embedded in fibrin and alginate when compared to non-encapsulated islets. TNFα, IL-6 and IL-1β were found in high concentrations in the media of co-cultures and monocyte mono-culture in fibrin.

Conclusion

Both alginate and fibrin provide key structural support and offer some protection for the islets towards human monocytes. Fibrin itself triggers the cytokine secretion from monocytes.     

Single and dual crosslinked oxidized methacrylated alginate/PEG hydrogels for bioadhesive applications

A degradable, cytocompatible bioadhesive can facilitate surgical procedures and minimize patient pain and post-surgical complications. In this study a bioadhesive hydrogel system based on oxidized methacrylated alginate/8-arm poly(ethylene glycol) amine (OMA/PEG) has been developed, and the bioadhesive characteristics of the crosslinked OMA/PEG hydrogels evaluated. Here we demonstrate that the swelling behavior, degradation profiles, and storage moduli of crosslinked OMA/PEG hydrogels are tunable by varying the degree of alginate oxidation. The crosslinked OMA/PEG hydrogels exhibit cytocompatibility when cultured with human bone marrow-derived mesenchymal stem cells. In addition, the adhesion strength of these hydrogels, controllable by varying the alginate oxidation level and measured using a porcine skin model, is superior to commercially available fibrin glue. This OMA/PEG hydrogel system with controllable biodegradation and mechanical properties and adhesion strength may be a promising bioadhesive for clinical use in biomedical applications, such as drug delivery, wound closure and healing, biomedical device implantation, and tissue engineering.     

Matrix replenishment by intervertebral disc cells after chemonucleolysis in vitro with chondroitinase ABC and chymopapain

BACKGROUND CONTEXT: One of the advantages of chemonucleolysis for the treatment of a herniated intervertebral disc is the potential for the disc to self-repair. It has been suggested that the enzymes used for chemonucleolysis differentially affect the potential of the disc cells to promote repair. PURPOSE: To test the ability of nucleus pulposus and anulus fibrosus cells to repair the extracellular matrix degraded in vitro by either chondroitinase ABC or chymopapain. STUDY DESIGN: An alginate cell culture system was used to monitor the progress of matrix repair after chemonucleolysis in vitro. METHODS: Rabbit nucleus pulposus or anulus fibrosus cells precultured for 10 days in alginate gel were briefly exposed to low concentrations of chondroitinase ABC or chymopapain and then returned to normal culture conditions for up to 4 weeks. At each time point, the contents of DNA and matrix macromolecules and proteoglycan synthesis were measured. RESULTS: The DNA content of enzyme-treated alginate beads during the following 4 weeks of culture was higher in the chondroitinase ABC group than in the chymopapain group (NP, p<.01, and AF, p<.05). The content of proteoglycan in beads containing nucleus pulposus and anulus fibrosus cells in the chondroitinase ABC group was higher than that in the chymopapain group (NP and AF, p<.001). The rate of proteoglycan synthesis and the content of collagen did not, however, differ between those two groups. CONCLUSIONS: Intervertebral disc cells exposed to chondroitinase ABC reestablish a matrix richer in proteoglycan than cells exposed to chymopapain. This may be because of differences in the substrate spectrum of each enzyme. Although these results cannot be translated directly to the in vivo situation, they suggest the possibility that cells in discs subjected to chondroitinase ABC-induced chemonucleolysis retain a greater ability to replenish their extracellular matrix with proteoglycans than cells in discs exposed to chymopapain.     

Alginate-based aerogels as wound dressings for efficient bacterial capture and enhanced antibacterial photodynamic therapy

The development of novel wound dressings, such as aerogels, with rapid hemostasis and bactericidal capacities for pre-hospital care is necessary. To prevent the occurrence of bacterial resistance, antibacterial photodynamic therapy (aPDT) with broad-spectrum antibacterial ability and negligible bacterial resistance has been intensively studied. However, photosensitizers often suffer from poor water solubility, short singlet oxygen (¹O₂) half-life and restricted ¹O₂ diffusion distance. Herein, sodium alginate was covalently modified by photosensitizers and phenylboronic acid, and cross-linked by Ca(II) ions to generate SA@TPAPP@PBA aerogel after lyophilization as an antibacterial photodynamic wound dressing. Afterwards, its photodynamic and bacterial capture activities were intensively evaluated. Furthermore, its hemostasis and bactericidal efficiency against Staphylococcus aureus were assessed via in vitro and in vivo assays. First, chemical immobilization of photosensitizers led to an enhancement of its solubility. Moreover, it showed an excellent hemostasis capacity. Due to the formation of reversible covalent bonds between phenylboronic acid and diol groups on bacterial cell surface, the aerogel could capture S. aureus tightly and dramatically enhance aPDT. To sum up, the prepared aerogel illustrated excellent hemostasis capacity and antibacterial ability against S. aureus. Therefore, they have great potential to be utilized as wound dressing in clinical trials.     

Synthesis and characterization of both ionically and enzymatically cross-linkable alginate

Alginate with phenol moieties in the polymer side chains was synthesized through the conjugation reaction of alginate and tyramine. Immersing an aqueous solution of the alginate containing horseradish peroxidase into a solution containing H(2)O(2) caused the solution to gel via peroxidase-catalyzed oxidative coupling of the phenols. In addition, alginate prepared under appropriate reaction conditions retained the attractive properties associated with unmodified alginate; spherical gel beads were formed by dropping an aqueous alginate solution (1.0wt.%) into a solution containing calcium ions. The oxidative coupling of the phenols was effective for suppressing the destabilization of the alginate gel resulting from a loss of bonding between the divalent cations and alginate. The mechanical properties of the resultant gels were influenced by the preparation conditions of the alginate and the type of cross-linking.     

藻酸盐对家兔肺组织的免疫损伤作用

目的：建立藻酸盐免疫性肺炎动物模型，研究藻酸盐对肺组织的致病作用；以探讨细菌生物被膜对呼吸系统的致病机制。方法：本实验用乙醇沉淀法提取细菌藻酸盐；A组用生理盐水作对照，B组、C组分别用海藻藻酸盐、细菌藻酸盐免疫家兔。比较三组家兔的体温、血象及血循环免疫复合物(CIC)水平；比较支气管肺泡灌洗液(BALF)细菌计数；观察肺组织的病理改变。结果：两种藻酸盐免疫组家兔的血CIC水平皆较处理前及生理盐水对照组显著增高，BALF培养无细菌生长。经两种藻酸盐免疫后皆出现细支气管旁淋巴细胞浸润、淋巴小结形成及细支气管管腔狭窄等病理改变。结论：海藻藻酸盐和细菌藻酸盐都能导致家兔肺组织非感染性免疫损伤，其主要病理改变为细支气管旁淋巴细胞浸润及淋巴小结形成；这种免疫损伤是呼吸道生物被膜病的致病机制之一。     

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。     

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.