Bioactive Long-Term Release from Biodegradable Microspheres Preserves Implanted ALG-PLO-ALG Microcapsules from In Vivo Response to Purified Alginate (original) (raw)
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Purpose. To assess whether prevention of unexpected in vivo adverse inflammatory and immune responses to biohybrid organ grafts for the treatment of Type I Diabetes Mellitus (T1DM) is possible by superoxide dismutase and ketoprofen controlled release. Methods. Superoxide dismutase and ketoprofen-loaded polyester microspheres were prepared by W/O/ W and O/W methods, embodied into purified alginate-poly-L-ornithine-alginate microcapsules and intraperitoneally implanted into CD1 mice. The microspheres were characterized for morphology, size, encapsulation efficiency, enzyme activity and in vitro release. Purified alginate contaminants were assayed, and the obtained microcapsules were investigated for size and morphology before and after implantation over 30 days. Cell pericapsular overgrowth and expression were evaluated by optical microscopy and flow cytometry. Results. Superoxide dismutase and ketoprofen sustained release reduced cell pericapsular overgrowth in comparison to the control. Superoxide dismutase release allowed preserving the microcapsules over 30 days. Ketoprofen-loaded microspheres showed some effect in the immediate post-grafting period. A higher macrophage and T-cell expression was observed for the control group. Conclusions. Microspheres containing superoxide dismutase and ketoprofen may represent novel tools to limit or prevent unpredictable adverse in vivo response to alginate, thus contributing to improve cell transplantation success rates in T1DM treatment.
Journal of Materials Science-materials in Medicine, 2005
The concept of encapsulated-cell therapy is very appealing, but in practice a great deal of technology and know-how is needed for the production of long-term functional transplants. Alginate is one of the most promising biomaterials for immunoisolation of allogeneic and xenogeneic cells and tissues (such as Langerhans islets). Although great advances in alginate-based cell encapsulation have been reported, several improvements need to be made before routine clinical applications can be considered. Among these is the production of purified alginates with consistently high transplantation-grade quality. This depends to a great extent on the purity of the input algal source as well as on the development of alginate extraction and purification processes that can be validated. A key engineering challenge in designing immunoisolating alginate-based microcapsules is that of maintaining unimpeded exchange of nutrients, oxygen and therapeutic factors (released by the encapsulated cells), while simultaneously avoiding swelling and subsequent rupture of the microcapsules. This requires the development of efficient, validated and well-documented technology for cross-linking alginates with divalent cations. Clinical applications also require validated technology for long-term cryopreservation of encapsulated cells to maintaining a product inventory in order to meet end-user demands. As shown here these demands could be met by the development of novel, validated technologies for production of transplantation-grade alginate and microcapsule engineering and storage. The advances in alginate-based therapy are demonstrated by transplantation of encapsulated rat and human islet grafts that functioned properly for about 1 year in diabetic mice.
Biomaterials, 2012
Application of alginate-polylysine (PLL) capsules for immunoisolation of living cells are suffering from a varying degree of success and large lab-to-lab variations. In this study we show that these differences in success rates can be attributed to alginate dependent essential physicochemical changes of the properties of capsules in vivo that will render the capsules more susceptible to inflammatory responses. Capsule properties were studied before and after implantation by XPS, by immunocytochemistry, and by measuring zeta potentials. We studied a capsule type which provokes for unknown reasons a strong inflammatory response, i.e. high-guluronic (G) alginate capsules and a capsule type with near identical physicochemical properties but which evokes a minimal inflammatory response, i.e. intermediate-G alginate capsules. The cause of the difference in response was a decrease in nitrogen content on high-G capsules due to detachment of PLL in vivo and an increase of the zeta-potential. Our data illustrate an important overlooked phenomena; the physicochemical properties are not necessarily the properties after exposure to the in vivo microenvironment and might induce undesired inflammatory responses and failure of encapsulated cellular grafts.
Journal of controlled …, 2005
Cell encapsulation technology raises hopes in medicine and biotechnology. Encapsulated pancreatic islets is a promising approach for the final solution of Type 1 diabetes. Unfortunately, evidence of long-term encapsulated islet graft survival and functional competence lies behind expectancy. Failure was often ascribed to the lack of biocompatibility generating inflammatory response, or limited immunobarrier competence or hypoxia or finally, low h-cell replication. In order to prevent severe inflammation at early stages after implantation, composite microcapsules were designed. Biodegradable microspheres containing ketoprofen were enveloped into the well established alginate/poly-l-ornithine/alginate capsules. Polyester microspheres were prepared, by solvent evaporation, and characterized for encapsulation efficiency, particle size and in vitro release. Biocompatibility and efficacy to prevent the inflammatory response were studied in vivo. Good encapsulation efficiency and the desired particle size were achieved. In vitro release studies evidenced a high burst effect probably due to a plasticizing effect of both water and ketoprofen. The composite systems showed good biocompatibility and capacity to completely avoid the inflammatory response and the pericapsular cell overgrowth. In conclusion, the inflammatory response in the immediate posttransplant period can be circumvented using multicompartment microcapsules releasing non-steroidal anti inflammatory drugs. D 2005 Published by Elsevier B.V.
Alginate-Based Cell Microencapsulation for Tissue Engineering and Regenerative Medicine
Current Pharmaceutical Design, 2017
Increasing numbers of requests for transplantable organs and their scarcity has led to a pressing need to find alternative solutions to standard transplantation. An appealing but challenging proposal came from the fields of tissue engineering and regenerative medicine, the purpose of which is to build tissues/organs from scratch in the laboratory and use them as either permanent substitutes for direct implantation into the patient's body, or as temporary substitutes to bridge patients until organ regeneration or transplantation. Using bioartificial constructs requires administration of immunosuppressant therapies to prevent rejection by the recipient. Microencapsulation has been identified as promising technology for immunoisolating biological materials from immune system attacks by the patient. It is based on entrapping cellular material within a spherical semipermeable polymeric scaffold. This latter defines the boundary between the internal native-like environment and the external "aggressive" one. The scaffold thus acts like a selective filter that makes possible an appropriate supply of nutrients and oxygen to the cellular constructs, while blocking the passage for adverse molecules. Alginate, which is a natural polymer, is the main biomaterial used in this context. Its excellent properties and mild gelation ability provide suitable conditions for supporting viability and preserving the functionalities of the cellular-engineered constructs over long periods. Although much remains to be done before bringing microencapsulated constructs into clinical practice, an increasing number of applications for alginate-based microencapsulation in numerous medical areas confirm the considerable potential for this technology in providing a cure for transplant in patients that excludes immunosuppressive therapies.
Insights in Behavior of Variably Formulated Alginate-Based Microcapsules for Cell Transplantation
BioMed Research International, 2015
Alginate-based microencapsulation of live cells may offer the opportunity to treat chronic and degenerative disorders. So far, a thorough assessment of physical-chemical behavior of alginate-based microbeads remains cloudy. A disputed issue is which divalent cation to choose for a high performing alginate gelling process. Having selected, in our system, high mannuronic (M) enriched alginates, we studied different gelling cations and their combinations to determine their eventual influence on physical-chemical properties of the final microcapsules preparation, in vitro and in vivo. We have shown that used of ultrapure alginate allows for high biocompatibility of the formed microcapsules, regardless of gelation agents, while use of different gelling cations is associated with corresponding variable effects on the capsules' basic architecture, as originally reported in this work. However, only the final application which the capsules are destined to will ultimately guide the selection of the ideal, specific gelling divalent cations, since in principle there are no capsules that are better than others.
Transplantation of Alginate Microcapsules
Transplantation, 1999
Background. Microencapsulation of islets of Langherhans in alginate poly-L-lysine capsules provides an effective protection against cell-mediated immune destruction, and ideally should allow the transplantation of islets in the absence of immunosuppression. It has previously been suggested that alginate rich in mannuronic acid (high M) is more immunogenic than alginate rich in guluronic acid (high G). The ability of these alginates to induce an antibody response in the recipient or act as an adjuvant to antibody responses against antigens leaked from the capsule was investigated in the present study.
Alginate Microcapsules as Nutrient Suppliers: An In Vitro Study
Volume 20, Number 1, Spring 2018, Serial Number: 77, 2018
Objective: Alginate, known as a group of anionic polysaccharides extracted from seaweeds, has attracted the attention of researchers because of its biocompatibility and degradability properties. Alginate has shown beneficial effects on wound healing as it has similar function as extracellular matrix. Alginate microcapsules (AM) that are used in tissue engineering as well as Dulbecco's modified Eagle's medium (DMEM) contain nutrients required for cell viability. The purpose of this research was introducing AM in medium and nutrient reagent cells and making a comparison with control group cells that have been normally cultured in long term. Materials and Methods: In this experimental study, AM were shaped in distilled water, it was dropped at 5 mL/hours through a flat 25G5/8 sterile needle into a crosslinking bath containing 0.1 M calcium chloride to produce calcium alginate microspheres. Then, the size of microcapsules (300-350 µm) were confirmed by Scanning Electron Microscopy (SEM) images after the filtration for selection of the best size. Next, DMEM was injected into AM. Afterward, adipose-derived mesenchymal stem cells (ADSCs) and Ringer's serum were added. Then, MTT and DAPI assays were used for cell viability and nucleus staining, respectively. Also, morphology of microcapsules was determined under invert microscopy. Results: Evaluation of the cells performed for spatial media/microcapsules at the volume of 40 µl, showed ADSCs after 1-day cell culture. Also, MTT assay results showed a significant difference in the viability of sustained-release media injected to microcapsules (P<0.05). DAPI staining revealed living cells on the microcapsules after 1 to 7-day cell culture. Conclusion: According to the results, AM had a positive effect on cell viability in scaffolds and tissue engineering and provide nutrients needed in cell therapy.
Frontiers in Bioengineering and Biotechnology, 2014
Islets encapsulated in immunoprotective microcapsules are being proposed as an alternative for insulin therapy for treatment of type 1 diabetes. Many materials for producing microcapsules have been proposed but only alginate does currently qualify as ready for clinical application. However, many different alginate-based capsule systems do exist. A pitfall in the field is that these systems are applied without a targeted strategy with varying degrees of success as a consequence. In the current review, the different properties of alginate-based systems are reviewed in view of future application in humans. The use of allogeneic and xenogeneic islet sources are discussed with acknowledging the different degrees of immune protection the encapsulation system should supply. Also issues such as oxygen supply and the role of danger associated molecular patterns (DAMPS) in immune activation are being reviewed. A common property of the encapsulation systems is that alginates for medical application should have an extreme high degree of purity and lack pathogen-associated molecular patterns (PAMPs) to avoid activation of the recipient's immune system. Up to now, non-inflammatory alginates are only produced on a lab-scale and are not yet commercially available. This is a major pitfall on the route to human application. Also the lack of predictive pre-clinical models is a burden. The principle differences between relevant innate and adaptive immune responses in humans and other species are reviewed. Especially, the extreme differences between the immune system of non-human primates and humans are cumbersome as non-human primates may not be predictive of the immune responses in humans, as opposed to the popular belief of regulatory agencies. Current insight is that although the technology is versatile major research efforts are required for identifying the mechanical, immunological, and physico-chemical requirements that alginate-based capsules should meet for successful human application.