Factors influencing alginate gel biocompatibility.

Alginate remains the most popular polymer used for cell encapsulation, yet its biocompatibility is inconsistent. Two commercially available alginates were compared, one with 71% guluronate (HiG), and the other with 44% (IntG). Both alginates were purified, and their purities were verified.

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.

Direct effect of alginate purification on the survival of islets immobilized in alginate-based microcapsules.

Alginate purification has been shown to decrease the host immune response to implanted alginate-based microcapsules, but the direct effect of contaminants on islet cell survival remains unknown. Wistar rat islets were immobilized in calcium alginate beads made with crude vs. purified alginate and then incubated in CMRL culture medium.

Adsorption of human immunoglobulin to implantable alginate-poly-L-lysine microcapsules: effect of microcapsule composition.

Alginate-poly-L-lysine-alginate (APA) microcapsules continue to be the most widely studied device for the immuno-protection of transplanted therapeutic cells. Producing APA microcapsules having a reproducible and high level of biocompatibility requires an understanding of the mechanisms of the immune response towards the implants. Here, we investigate the adsorption of immunoglobulins (IgG, IgM, and IgA) onto the surface of APA microcapsules in vitro after their exposure to human serum and peritoneal fluid.

Biocompatibility of alginate-poly-L-lysine microcapsules for cell therapy.

Cell microencapsulation holds promise for the treatment of many diseases by the continuous delivery of therapeutic products. The biocompatibility of the microcapsules and their biomaterials components is a critical issue for the long-term efficacy of this technology. The objective of this paper is to provide detailed information about the principal factors affecting the biocompatibility of alginates and alginate-poly-l-lysine microcapsules, which are the most frequently employed biomaterials and encapsulation devices for cell immobilization, respectively.

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.