Role of protein contaminants in the immunogenicity of alginates.

Alginate is widely used for cell microencapsulation and transplantation. There is a lack of standardization of alginate purity and composition. In a previous study, we compared different alginate purification methods and concluded that polyphenol and endotoxin contaminants were eliminated efficiently but residual protein contaminants persisted with all of the methods under evaluation.

The effect of covalent cross-links between the membrane components of microcapsules on the dissemination of encapsulated malignant cells.

Stem cells and immortalized cells have considerable therapeutic potential but present risks of malignant transformation. Cell microencapsulation allows transplantation without immunosuppression. We have developed a method for microencapsulating living cells within covalently cross-linked membranes that are chemically and mechanically extremely resistant.

Evaluation of alginate purification methods: effect on polyphenol, endotoxin, and protein contamination.

Alginate, a polysaccharide extracted from brown seaweed, is widely used for the microencapsulation of islets of Langerhans, allowing their transplantation without immunosuppression. This natural polymer is known to be largely contaminated. The implantation of islets encapsulated using unpurified alginate leads to the development of fibrotic cell overgrowth around the microcapsules and normalization of the blood glucose is restricted to a very short period if it is achieved at all.

Impact of residual contamination on the biofunctional properties of purified alginates used for cell encapsulation.

Alginate is frequently used for cell encapsulation, but its biocompatibility is neither optimal nor reproducible. Purifying the alginate is critical for achieving a suitable biocompatibility. However, published purification methods vary in efficiency and may induce changes in polymer biofunctionality.

Physicochemical model of alginate-poly-L-lysine microcapsules defined at the micrometric/nanometric scale using ATR-FTIR, XPS, and ToF-SIMS.

Alginate-poly-L-lysine-alginate (APA) microcapsules are currently being investigated as a means to immuno-isolate transplanted cells, but their biocompatibility is limited. In this study, we verified the hypothesis that poly-L-lysine (PLL), which is immunogenic when unbound, is exposed at the APA microcapsule surface. To do so, we analysed the microcapsule membrane at the micrometric/nanometric scale using attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry.

Effect of poly-L-lysine coating on macrophage activation by alginate-based microcapsules: assessment using a new in vitro method.

The characteristics of the microcapsule surface, which interacts directly with the host macrophages, may have a role in the biocompatibility of alginate-poly-L-lysine (PLL)-alginate (APA) microcapsule. The objectives of the study were: 1) to develop and validate a simple, rapid, and sensitive in vitro method for assessing microcapsule biocompatibility, based on microcapsule coincubation with macrophages and measurement, by reverse transcriptase-polymerase chain reaction, of cytokine mRNA expression, and 2) to evaluate the effect of alginate purification and PLL coating on macrophage activation. The mRNA expression of tumor necrosis factor-alpha and interleukin-1beta was significantly higher when macrophages were coincubated with beads made with nonpurified compared with purified alginate (p<0.

Microencapsulation of living cells in semi-permeable membranes with covalently cross-linked layers.

Microencapsulation in semi-permeable membranes protects transplanted cells against immune destruction. Microcapsule strength is critical. We describe a method to microencapsulate living cells in alginate-poly-L-lysine (PLL)-alginate membranes with covalent links between adjacent layers of microcapsule membranes, while preserving the desired membrane molecular weight cut-off (MWCO) and microencapsulated cell viability.

Novel purification method for mammalian seminal plasma phospholipid-binding proteins reveals the presence of a novel member of this family of protein in stallion seminal fluid.

A family of bull seminal plasma (BSP) phospholipid-binding proteins (BSP proteins), potentiate heparin- and HDL-induced capacitation. The homologous proteins have been purified from stallion and boar seminal plasma, and detected in low concentrations in other mammalian seminal plasma. In this study, we developed a new isolation method for mammalian seminal plasma choline phospholipid-binding proteins wherein they are present in low concentrations.

Major proteins of bovine seminal plasma bind to the low-density lipoprotein fraction of hen's egg yolk.

Over the past 60 years, egg yolk (EY) has been routinely used in both liquid semen extenders and those used to cryopreserve sperm. However, the mechanism by which EY protects sperm during liquid storage or from freezing damage is unknown. Bovine seminal plasma contains a family of proteins designated BSP-A1/-A2, BSP-A3, and BSP-30-kDa (collectively called BSP proteins).