Advances in islet encapsulation technologies
TL;DR: Although encapsulation technology has met several challenges, the convergence of expertise in materials, nanotechnology, stem cell biology and immunology is allowing the goal of encapsulated islet cell therapy for humans to be closer.
Abstract: Type 1 diabetes is an autoimmune disorder in which the immune system attacks and destroys insulin-producing islet cells of the pancreas. Although islet transplantation has proved to be successful for some patients with type 1 diabetes, its widespread use is limited by islet donor shortage and the requirement for lifelong immunosuppression. An encapsulation strategy that can prevent the rejection of xenogeneic islets or of stem cell-derived allogeneic islets can potentially eliminate both of these barriers. Although encapsulation technology has met several challenges, the convergence of expertise in materials, nanotechnology, stem cell biology and immunology is allowing us to get closer to the goal of encapsulated islet cell therapy for humans.
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TL;DR: A review of hydrogel-based biomaterial inks and bioinks for 3D printing can be found in this paper, where the authors provide a comprehensive overview and discussion of the tailorability of material, mechanical, physical, chemical and biological properties.
Abstract: 3D printing alias additive manufacturing can transform 3D virtual models created by computer-aided design (CAD) into physical 3D objects in a layer-by-layer manner dispensing with conventional molding or machining. Since the incipiency, significant advancements have been achieved in understanding the process of 3D printing and the relationship of component, structure, property and application of the created objects. Because hydrogels are one of the most feasible classes of ink materials for 3D printing and this field has been rapidly advancing, this Review focuses on hydrogel designs and development of advanced hydrogel-based biomaterial inks and bioinks for 3D printing. It covers 3D printing techniques including laser printing (stereolithography, two-photon polymerization), extrusion printing (3D plotting, direct ink writing), inkjet printing, 3D bioprinting, 4D printing and 4D bioprinting. It provides a comprehensive overview and discussion of the tailorability of material, mechanical, physical, chemical and biological properties of hydrogels to enable advanced hydrogel designs for 3D printing. The range of hydrogel-forming polymers covered encompasses biopolymers, synthetic polymers, polymer blends, nanocomposites, functional polymers, and cell-laden systems. The representative biomedical applications selected demonstrate how hydrogel-based 3D printing is being exploited in tissue engineering, regenerative medicine, cancer research, in vitro disease modeling, high-throughput drug screening, surgical preparation, soft robotics and flexible wearable electronics. Incomparable by thermoplastics, thermosets, ceramics and metals, hydrogel-based 3D printing is playing a pivotal role in the design and creation of advanced functional (bio)systems in a customizable way. An outlook on future directions of hydrogel-based 3D printing is presented.
427 citations
TL;DR: This Review summarizes the current status, latest updates and future prospects for delivery of peptides, proteins and other biologics, including subcutaneous, transdermal, oral, inhalation, nasal and buccal routes.
Abstract: Biologics now constitute a significant element of available medical treatments. Owing to their clinical and commercial success, biologics are a rapidly growing class and have become a dominant therapeutic modality. Although most of the successful biologics to date are drugs that bear a peptidic backbone, ranging from small peptides to monoclonal antibodies (~500 residues; 150 kDa), new biologic modalities, such as nucleotide-based therapeutics and viral gene therapies, are rapidly maturing towards widespread clinical use. Given the rise of peptides and proteins in the pharmaceutical landscape, tremendous research and development interest exists in developing less-invasive or non-invasive routes for the systemic delivery of biologics, including subcutaneous, transdermal, oral, inhalation, nasal and buccal routes. This Review summarizes the current status, latest updates and future prospects for such delivery of peptides, proteins and other biologics.
341 citations
TL;DR: The article presents the most important structures of microparticles (microspheres, microcapsules, coated pellets, etc.), interpreted with microscopic images too, as well as the drug release mechanisms and commonly used excipients.
Abstract: Microparticles, microspheres, and microcapsules are widely used constituents of multiparticulate drug delivery systems, offering both therapeutic and technological advantages. Microparticles are generally in the 1–1000 µm size range, serve as multiunit drug delivery systems with well-defined physiological and pharmacokinetic benefits in order to improve the effectiveness, tolerability, and patient compliance. This paper reviews their evolution, significance, and formulation factors (excipients and procedures), as well as their most important practical applications (inhaled insulin, liposomal preparations). The article presents the most important structures of microparticles (microspheres, microcapsules, coated pellets, etc.), interpreted with microscopic images too. The most significant production processes (spray drying, extrusion, coacervation, freeze-drying, microfluidics), the drug release mechanisms, and the commonly used excipients, the characterization, and the novel drug delivery systems (microbubbles, microsponges), as well as the preparations used in therapy are discussed in detail.
257 citations
University of Illinois at Chicago1, Massachusetts Institute of Technology2, Boston Children's Hospital3, North Carolina State University4, University of Virginia5, Joslin Diabetes Center6, University of Massachusetts Medical School7, Norwegian University of Science and Technology8, Slovak Academy of Sciences9
TL;DR: Transplantation of pancreatic islet cells encapsulated in alginate microspheres into the omental bursa of the peritoneal cavity of NHPs significantly reduces FBRs and extends the longevity of the cells.
Abstract: The transplantation of pancreatic islet cells could restore glycaemic control in patients with type-I diabetes. Microspheres for islet encapsulation have enabled long-term glycaemic control in diabetic rodent models; yet human patients transplanted with equivalent microsphere formulations have experienced only transient islet-graft function, owing to a vigorous foreign-body reaction (FBR), to pericapsular fibrotic overgrowth (PFO) and, in upright bipedal species, to the sedimentation of the microspheres within the peritoneal cavity. Here, we report the results of the testing, in non-human primate (NHP) models, of seven alginate formulations that were efficacious in rodents, including three that led to transient islet-graft function in clinical trials. Although one month post-implantation all formulations elicited significant FBR and PFO, three chemically modified, immune-modulating alginate formulations elicited reduced FBR. In conjunction with a minimally invasive transplantation technique into the bursa omentalis of NHPs, the most promising chemically modified alginate derivative (Z1-Y15) protected viable and glucose-responsive allogeneic islets for 4 months without the need for immunosuppression. Chemically modified alginate formulations may enable the long-term transplantation of islets for the correction of insulin deficiency.
221 citations
TL;DR: Current efforts aimed at generating a sustainable source of functional human stem cell-derived insulin-producing islet cells for cell transplantation are described and state-of-the-art efforts to protect such cells via immune modulation and encapsulation strategies are presented.
181 citations
Cites background from "Advances in islet encapsulation tec..."
...Most importantly, few, if any, encapsulation strategies have been able to protect islets long-term from both an allogeneic and autoimmune response in a spontaneously autoimmune setting (Desai and Shea, 2017)....
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...However, the use of a suitable encapsulation membrane as a physical barrier between the recipient and hESC-derived beta cells could enable the safe use of these therapies while reducing or eliminating the need for immunosuppression (de Vos et al., 2010; Desai and Shea, 2017; Vaithilingam and Tuch, 2011; Vegas et al., 2016)....
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References
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TL;DR: The observations in patients with type 1 diabetes indicate that islet transplantation can result in insulin independence with excellent metabolic control when glucocorticoid-free immunosuppression is combined with the infusion of an adequate islet mass.
Abstract: Background Registry data on patients with type 1 diabetes mellitus who undergo pancreatic islet transplantation indicate that only 8 percent are free of the need for insulin therapy at one year. Methods Seven consecutive patients with type 1 diabetes and a history of severe hypoglycemia and metabolic instability underwent islet transplantation in conjunction with a glucocorticoid-free immunosuppressive regimen consisting of sirolimus, tacrolimus, and daclizumab. Islets were isolated by ductal perfusion with cold, purified collagenase, digested and purified in xenoprotein-free medium, and transplanted immediately by means of a percutaneous transhepatic portal embolization. Results All seven patients quickly attained sustained insulin independence after transplantation of a mean (±SD) islet mass of 11,547±1604 islet equivalents per kilogram of body weight (median follow-up, 11.9 months; range, 4.4 to 14.9). All recipients required islets from two donor pancreases, and one required a third transplant from tw...
4,913 citations
Book•
01 Jan 1991
TL;DR: Part 1 BASIC STRUCTURAL PRINCIPLES: The Building Blocks and Motifs of Protein Structure and Part 2 STRUCTURE, FUNCTION and ENGINEERING: Structure, Function and Engineering.
Abstract: PART 1 BASIC STRUCTURAL PRINCIPLES 1. The Building Blocks 2. Motifs of Protein Structure 3. alpha-Domain Structures 4. alpha/ss Structures 5. ss Structures 6. Folding and Flexibility 7. DNA Structures PART 2 STRUCTURE, FUNCTION AND ENGINEERING 8. DNA Recognition in Procaryotes by Helix-Turn-Helix Motifs 9. DNA Recognition by Eukaryotic Transcription Factors 10. Specific Transcription Factors Belong to a Few Families 11. An Example of Enzyme Catalysis: Serine Proteinases 12. Membrane Proteins 13. Signal Transduction 14. Fibrous Proteins 15. Recognition of Foreign Molecules by the Immune System 16. The Structure of Spherical Viruses 17. Prediction, Engineering, and Design of Protein Structures 18. Determination of Protein Structures
3,714 citations
TL;DR: The targets and mechanisms of M SC-mediated immunomodulation and the possible translation of MSCs to new therapeutic approaches are discussed.
Abstract: Mesenchymal stem cells (MSCs) are a heterogeneous subset of stromal stem cells that can be isolated from many adult tissues. They can differentiate into cells of the mesodermal lineage, such as adipocytes, osteocytes and chondrocytes, as well as cells of other embryonic lineages. MSCs can interact with cells of both the innate and adaptive immune systems, leading to the modulation of several effector functions. After in vivo administration, MSCs induce peripheral tolerance and migrate to injured tissues, where they can inhibit the release of pro-inflammatory cytokines and promote the survival of damaged cells. This Review discusses the targets and mechanisms of MSC-mediated immunomodulation and the possible translation of MSCs to new therapeutic approaches.
3,142 citations
TL;DR: The main functions of polarized macrophages are reviewed and the perspectives of this field are discussed, which include high endocytic clearance capacities and trophic factor synthesis, accompanied by reduced pro-inflammatory cytokine secretion.
Abstract: Macrophages are widely distributed immune system cells that play an indispensable role in homeostasis and defense. They can be phenotypically polarized by the microenvironment to mount specific functional programs. Polarized macrophages can be broadly classified in two main groups: classically activated macrophages (or M1), whose prototypical activating stimuli are IFNgamma and LPS, and alternatively activated macrophages (or M2), further subdivided in M2a (after exposure to IL-4 or IL-13), M2b (immune complexes in combination with IL-1beta or LPS) and M2c (IL-10, TGFbeta or glucocorticoids). M1 exhibit potent microbicidal properties and promote strong IL-12-mediated Th1 responses, whilst M2 support Th2-associated effector functions. Beyond infection M2 polarized macrophages play a role in resolution of inflammation through high endocytic clearance capacities and trophic factor synthesis, accompanied by reduced pro-inflammatory cytokine secretion. Similar functions are also exerted by tumor-associated macrophages (TAM), which also display an alternative-like activation phenotype and play a detrimental pro-tumoral role. Here we review the main functions of polarized macrophages and discuss the perspectives of this field.
2,836 citations
TL;DR: The microencapsulated islets remained morphologically and functionally intact throughout long-term culture studies lasting over 15 weeks.
Abstract: Single implantation of microencapsulated islets into rats with streptozotocin-induced diabetes corrected the diabetic state for 2 to 3 weeks. The microencapsulated islets remained morphologically and functionally intact throughout long-term culture studies lasting over 15 weeks.
2,344 citations