The microencapsulation of cells within alginate poly-L-lysine microcapsules prepared with the standard single step drop technique: histologically identified membrane imperfections and the associated graft rejection

Poly-L-Lysine Induces Fibrosis on Alginate Microcapsules via the Induction of Cytokines

Alginate – poly-l-lysine (PLL) microcapsules can be used for transplantation of insulin-producing cells for treatment of type I diabetes. In this work we wanted to study the inflammatory reactions against implanted microcapsules due to PLL. We have seen that by reducing the PLL layer, less overgrowth of the capsule is obtained. By incubating different cell types with PLL and afterwards measuring cell viability with MTT, we found massive cell death at concentrations of PLL higher than 10 μg/ml. Staining with annexin V and propidium iodide showed that PLL induced necrosis but not apoptosis. The proinflammatory cytokine, tumor necrosis factor (TNF), was detected in supernatants from monocytes stimulated with PLL. The TNF response was partly inhibited with antibodies against CD14, which is a well-known receptor for lipopolysaccharide (LPS). Bactericidal permeability increasing protein (BPI) and a lipid A analogue (B-975), which both inhibit LPS, did not inhibit PLL from stimulating monocytes to TNF production. This indicates that PLL and LPS bind to different sites on monocytes, but because they both are inhibited by a p38 MAP kinase inhibitor, they seem to have a common element in the signal transducing pathway. These results suggest that PLL may provoke inflammatory responses either directly or indirectly through its necrosis-inducing abilities. By combining soluble PLL and alginate both the toxic and TNF-inducing effects of PLL were reduced. The implications of these data are to use alginate microcapsules with low amounts of PLL for transplantation purposes.

Living Cell Factories - Electrosprayed Microcapsules and Microcarriers for Minimally Invasive Delivery

Minimally invasive delivery of "living cell factories" consisting of cells and therapeutic agents has gained wide attention for next generation biomaterial device systems for multiple applications including musculoskeletal tissue regeneration, diabetes and cancer. Cellular-based microcapsules and microcarrier systems offer several attractive features for this particular purpose. One such technology capable of generating these types of systems is electrohydrodynamic (EHD) spraying. Depending on various parameters, including applied voltage, biomaterial properties (viscosity, conductivity) and needle geometry, complex structures and arrangements can be fabricated for therapeutic strategies. The advances in the use of EHD technology are outlined, specifically in the manipulation of bioactive and dynamic material systems to control size, composition and configuration in the development of minimally invasive micro-scaled biopolymeric systems. The exciting therapeutic applications of this technology, future perspectives and associated challenges are also presented.

Designing anti-diabetic β-cells microcapsules using polystyrenic sulfonate, polyallylamine, and a tertiary bile acid: Morphology, bioenergetics, and cytokine analysis

PURPOSE

Recently sodium alginate (SA)-poly-l-ornithine (PLO) microcapsules containing pancreatic β-cells that showed good morphology but low cell viability (<27%) was designed. In this study, two new polyelectrolytes, polystyrenic sulfonate (PSS; at 1%) and polyallylamine (PAA; at 2%) were incorporated into a microencapsulated-formulation, with the aim of enhancing the physical properties of the microcapsules. Following incorporation, the structural characteristics and cell viability were investigated. The effects of the anti-inflammatory bile acid, ursodeoxycholic acid (UDCA), on microcapsule morphology, size, and stability as well as β-cell biological functionality was also examined.

METHODS

Microcapsules were prepared using PLO-PSS-PAA-SA mixture and two types of microcapsules were produced: without UDCA (control) and with UDCA (test). Microcapsule morphology, stability, and size were examined. Cell count, microencapsulation efficiency, cell bioenergetics, and activity were also examined.

RESULTS

The new microcapsules showed good morphology but cell viability remained low (29% ± 3%). UDCA addition improved cell viability post-microencapsulation (42 ± 5, P < 0.01), reduced swelling (P < 0.01), improved mechanical strength (P < 0.01), increased Zeta-potential (P < 0.01), and improved stability. UDCA addition also increased insulin production (P < 0.01), bioenergetics (P < 0.01), and decreased β-cell TNF-α (P < 0.01), IFN-gamma (P < 0.01), and IL-6 (P < 0.01) secretions.

CONCLUSIONS

Addition of 4% UDCA to a formulation system consisting of 1.8% SA, 1% PLO, 1% PSS, and 2% PAA enhanced cell viability post-microencapsulation and resulted in a more stable formulation with enhanced encapsulated β-cell metabolism, bioenergetics, and biological activity with reduced inflammation. This suggests potential application of UDCA, when combined with SA, PLO, PSS, and PAA, in β-cell microencapsulation and diabetes treatment. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:501-509, 2016.

Characterization of a novel bile acid-based delivery platform for microencapsulated pancreatic β-cells

INTRODUCTION

In a recent study, we confirmed good chemical and physical compatibility of microencapsulated pancreatic β-cells using a novel formulation of low viscosity sodium alginate (LVSA), Poly-L-Ornithine (PLO), and the tertiary bile acid, ursodeoxycholic acid (UDCA). This study aimed to investigate the effect of UDCA on the morphology, swelling, stability, and size of these new microcapsules. It also aimed to evaluate cell viability in the microcapsules following UDCA addition.

MATERIALS AND METHODS

Microencapsulation was carried out using a Büchi-based system. Two (LVSA-PLO, control and LVSA-PLO-UDCA, test) pancreatic β-cells microcapsules were prepared at a constant ratio of 10:1:3, respectively. The microcapsules' morphology, cell viability, swelling characteristics, stability, mechanical strength, Zeta potential, and size analysis were examined. The cell contents in each microcapsule and the microencapsulation efficiency were also examined.

RESULTS

The addition of UDCA did not affect the microcapsules' morphology, stability, size, or the microencapsulation efficiency. However, UDCA enhanced cell viability in the microcapsules 24 h after microencapsulation (p < 0.01), reduced swelling (p < 0.05), reduced Zeta potential (- 73 ± 2 to - 54 ± 2 mV, p < 0.01), and increased mechanical strength of the microcapsules (p < 0.05) at the end of the 24-h experimental period.

DISCUSSION AND CONCLUSION

UDCA increased β-cell viability in the microcapsules without affecting the microcapsules' size, morphology, or stability. It also increased the microcapsules' resistance to swelling and optimized their mechanical strength. Our findings suggest potential benefits of the bile acid UDCA in β-cell microencapsulation.

Core-shell hydrogel microcapsules for improved islets encapsulation

Islets microencapsulation holds great promise to treat type 1 diabetes. Currently used alginate microcapsules often have islets protruding outside capsules, leading to inadequate immuno-protection. A novel design of microcapsules with core-shell structures using a two-fluid co-axial electro-jetting is reported. Improved encapsulation and diabetes correction is achieved in a single step by simply confining the islets in the core region of the capsules.

Improving cell encapsulation through size control

Capsules based on the polyelectrolyte complexation between the polyanions sodium alginate and sodium cellulose sulphate with the polycation poly(methylene-co-guanidine) hydrochloride in the presence of calcium chloride have previously shown important advantages for cell encapsulation. However, in vivo long-term applications require capsule features that are well suited for the functionality of encapsulated cells. These should be targeted to the site of implantation with an appropriate size, a relative stability, and suitable diffusion properties. This study shows the effect of capsule size reduction, from 1 mm to 400 microm, on capsule quality control, mechanical stability, diffusion properties, and in vitro activities of the encapsulated cells. Following a controlled preparation, it was determined that the capsule mechanical stability was largely dependent on the volume ratio of the capsule over the membrane. The molecule diffusion time was related to the surface/volume ratio of the capsule even for the capsules exhibiting an identical cut-off towards the proteins and the dextran molecules. Finally, the in vitro cellular activities, for both primary cultures of rat islets and murine hepatocytes, were improved for cells encapsulated into the 400 microm capsules compared with those in the 1 mm capsules. All of these findings suggest that the smaller capsules present better properties for future clinical applications, at the same time widening the choice of implantation site, and strengthen the notion that slight changes in the capsular morphological parameters can largely influence the graft function in vivo.

Influence of Process Conditions During Impulsed Electrostatic Droplet Formation on Size Distribution of Hydrogel Beads

In the medical applications of microencapsulation of living cells there are strict requirements concerning the high size uniformity and the optimal diameter, the latter dependent on the kind of therapeutic application, of manufactured gel beads. The possibility of manufacturing small size gel bead samples (diameter 300 microm and below) with a low size dispersion (less than 10%), using an impulsed voltage droplet generator, was examined in this work. The main topic was the investigation of the influence of values of electric parameters (voltage U, impulse time tau and impulse frequency f) on the quality of obtained droplets. It was concluded that, owing to the implementation of the impulse mode and regulation of tau and f values, it is possible to work in a controlled manner in the jet flow regime (U> critical voltage UC). It is also possible to obtain uniform bead samples with the average diameter, deff, significantly lower than the nozzle inner diameter dI (bead diameters 0.12-0.25 mm by dI equal to 0.3 mm, size dispersion 5-7%). Alterations of the physical parameters of the process (polymer solution physico-chemical properties, flow rate, distance between nozzle and gellifying bath) enable one to manufacture uniform gel beads in the wide range of diameters using a single nozzle.

Artificial cell bioencapsulation in macro, micro, nano, and molecular dimensions: keynote lecture

Artificial cells now ranges from macro-dimensions, to micron-dimensions, to nano-dimensions, and to molecular dimensions. Those in the macro-dimensions are suitable for use in the bioencapsulation of cells, tissues, microorganisms, and bioreactants. Those in the micron-dimensions are suitable for the bioencapsulation of enzymes, microorganisms, peptides, drugs, vaccine, and other materials. Those in the nano-dimension are being used for blood substitutes and carriers for enzymes, peptides, drugs, etc. Those in the molecular-dimensions are used as blood substitutes, crosslinked enzymes etc.

Artificial Cells for Cell and Organ Replacements

The artificial cell is a Canadian invention (Chang, Science, 1964). This principle is being actively investigated for use in cell and organ replacements. The earliest routine clinical use of artificial cells is in the form of coated activated charcoal for hemoperfusion for use in the removal of drugs, and toxins and waste in uremia and liver failure. Encapsulated cells are being studied for the treatment of diabetes, liver failure, and kidney failure, and the use of encapsulated genetically-engineered cells is being investigated for gene therapy. Blood substitutes based on modified hemoglobin are already in Phase III clinical trials in patients, with as much as 20 units being infused into each patient during trauma surgery. Artificial cells containing enzymes are being developed for clinical trial in hereditary enzyme deficiency diseases and other diseases. The artificial cell is also being investigated for drug delivery and for other uses in biotechnology, chemical engineering, and medicine.

Increased viability of transplanted hepatocytes when hepatocytes are co-encapsulated with bone marrow stem cells using a novel method

This study is to investigate the viability of hepatocytes when transplanted into Wistar rats using co-encapsulated hepatocytes and bone marrow stem cells. Hepatocytes and bone marrow stem cells, isolated from Wistar rats, are co-encapsulated using either the standard single-step method or a novel two-step cell encapsulation method (www.artcell.mcgill.ca). After intraperitoneal transplantation into Wistar rats, the histology, fate of recovered microcapsules and viability of encapsulated hepatocytes are studied. When prepared using the standard method, there is excellent viability but only for up to 3 weeks. After this, there is extensive fibrous coating and severe fibrous adhesion and no microcapsules can be recovered. On the other hand, using the new two-step encapsulation method, the viability of the encapsulated hepatocytes can be followed for more than 4 months after transplantation. Even up to 4 months, there is significantly less host reaction when using the two-step encapsulation method and 50% of the microcapsules can be recovered. Co-encapsulated with bone marrow stem cells resulted in further increase in viability of the hepatocytes when followed up to 4 months after transplantation. This new approach may improve the potential feasibility of using co-encapsulation of hepatocytes and bone marrow stem cells in bio-artificial liver support for the treatment of liver failure, especially for acute liver failure.

Artificial cells and bioencapsulation in bioartificial organs

The most common use of artificial cells is for bioencapsulation of biologically active materials. Many combination of materials can be bioencapsulated. The permeability, composition and configurations of artificial cell membrane can be varied using different types of synthetic or biological materials. These possible variations in contents and membranes allow for large variations in the properties and functions of artificial cells.

The capsular overgrowth on microencapsulated pancreatic islet grafts in streptozotocin and autoimmune diabetic rats

This study investigates whether capsular overgrowth on alginate-polylysine microencapsulated islets is influenced by (1) the presence of islet tissue, (2) MHC incompatibility between donor and recipient, or (3) the presence of autoimmune diabetes. Encapsulated Albino Oxford (AO, n = 6, isografts) and Lewis (n = 6, allografts) rat islets, and encapsulated human islets (n = 5, xenografts) were implanted intraperitoneally into streptozotocin-diabetic AO rats. Also, encapsulated AO islets were implanted into autoimmune diabetic Bio Breeding/Organon (BB/O) rats (n = 5, allografts). Five isografts, five allografts, and three xenografts in AO recipients and five allografts in BB/O recipients resulted in normoglycemia. Two weeks after implantation, islets containing capsules were retrieved by peritoneal lavage, after which all animals that had become normoglycemic after transplantation returned to a state of hyperglycemia. Recovery rates of the capsules of these successful grafts, expressed as percentages of the initially implanted graft volume, varied from 72% +/- 7% to 80% +/- 9%. The associated pericapsular infiltrates (PCI) were similar in all groups and varied from 3.2% +/- 1.4% to 8.3% +/- 2.6%. Similar recovery rates and PCI were also found with empty capsules. However, the recovery rates of recipients with graft failures were lower and showed more PCI. Immunohistological staining of PCI showed no differences in the types of cells in the PCI on capsules with or without islets. We conclude that this early PCI is a capsule-induced foreign body reaction that is not influenced by MHC incompatibility or by the presence of autoimmune diabetes, and it should be avoided by improving the biocompatibility of the capsules.

Artificial cells in immobilization biotechnology

Artificial cells contain biologically active materials. Artificial cells containing adsorbents have been a routine form of treatment in hemoperfusion for patients. This includes acute poisoning, high blood aluminum and iron, and supplement to dialysis in kidney failure. Artificial cells are being tested for use as red blood cell substitutes. Artificial cells encapsulated cell culture are being tested in animals for the treatment of diabetes and liver failure. A novel 2 step method has prevented xenograft rejection. Artificial cells containing enzymes are being studied for treatment in hereditary enzyme deficiency diseases and other diseases. Recent demonstration of extensive enterorecirculation of amino acids in the intestine has allowed its oral administration to deplete specific amino acids. Artificial cells containing complex enzyme system convert wastes like urea and ammonia into essential amino acids. Artificial cell is being used for the production of monoclonal antibodies, interferons and other biotechnological products. It is also being investigated for drug delivery, and for use in other applications in biotechnology, chemical engineering and medicine.