Encapsulation of Cells in Alginate Gels. In: Guisan JM, editor. Immobilization of Enzymes and Cells. Totowa: Humana Press; 2006. pp. 345-55. [DOI: 10.1007/978-1-59745-053-9_30]

An Atmosphere-Breathing Refillable Biphasic Device for Cell Replacement Therapy

Cell replacement therapy is emerging as a promising treatment platform for many endocrine disorders and hormone deficiency diseases. The survival of cells within delivery devices is, however, often limited due to low oxygen levels in common transplantation sites. Additionally, replacing implanted devices at the end of the graft lifetime is often unfeasible and, where possible, generally requires invasive surgical procedures. Here, the design and testing of a modular transcutaneous biphasic (BP) cell delivery device that provides enhanced and unlimited oxygen supply by direct contact with the atmosphere is presented. Critically, the cell delivery unit is demountable from the fixed components of the device, allowing for surgery-free refilling of the therapeutic cells. Mass transfer studies show significantly improved performance of the BP device in comparison to subcutaneous controls. The device is also tested for islet encapsulation in an immunocompetent diabetes rodent model. Robust cell survival and diabetes correction is observed following a rat-to-mouse xenograft. Lastly, nonsurgical cell refilling is demonstrated in dogs. These studies show the feasibility of this novel device for cell replacement therapies.

Effects of pH on the Shape of Alginate Particles and Its Release Behavior

A vast majority of alginate particles exist as spheres in most practical uses, and both the particle shape and size are the key factors dominating the applications and performance of alginate gels. Therefore, it becomes an issue of great interest to investigate the aspheric alginate particles. As the first step, various shaped alginate particles were formed due to various pH values in gelation solutions. It was experimentally demonstrated that a low pH brought about an oblate shape, and particularly lower concentrations of both alginate and divalent cations resulted in a flattened oblate shape. Ba2+acting as a cross-linker had a less impact on the particle shape than Ca2+due to a higher affinity in alginate intermolecular cross-linking. With a larger surface area, an oblate particle offered a higher release rate than a spheric one.

The effect of alginate and chitosan concentrations on some properties of chitosan-coated alginate beads and survivability of encapsulated Lactobacillus rhamnosus in simulated gastrointestinal conditions and during heat processing

BACKGROUND

In this study, chitosan-coated alginate beads were produced with different concentrations of chitosan and alginate to evaluate the survival of encapsulated Lactobacillus rhamnosus GG during exposure to adverse conditions in gastrointestinal simulated juice and heat processing.

RESULTS

The encapsulation yield of different encapsulation treatments was between 25 and 53.2%. Although there was a drastic decrease in pH within 48 h of incubation in MRS medium inoculated with free and encapsulated bacteria, no significant changes (P > 0.05) in bacterial count were observed among different encapsulation treatments. Moreover, the survival rate after gastrointestinal juice exposure of all prepared beads was 10-87 times greater than that of free cells and was significantly enhanced by increasing chitosan and alginate concentrations. The encapsulated bacteria survived significantly (P < 0.05) better than the free cells during heat exposure at 55, 60 and 65 °C: free cells experienced about 5 log cycles reduction after heat treatment at 65 °C for 30 min, whereas 40 g L(-1) alginate/10 g L(-1) chitosan-encapsulated L. rhamnosus was reduced by only 2.55 log cycles.

CONCLUSION

Encapsulation effectively protected L. rhamnosus against heat treatment and gastrointestinal conditions, and this effect is important in delivering sufficient numbers of viable probiotic bacteria to the gastrointestinal tract.

Behaviour and ultrastructure of human bone marrow-derived mesenchymal stem cells immobilised in alginate-poly-l-lysine-alginate microcapsules

CONTEXT

Human bone marrow mesenchymal stem cells (hBM-MSCs) show a great promise for the treatment of a variety of diseases. Despite the previous trials to encapsulate hBM-MSCs in alginate-poly-l-lysine-alginate (APA) systems, the various changes that follow immobilisation have not been ascertained yet.

OBJECTIVE

Determine the various consequences derived from entrapment on cell behaviour, putting special emphasis on the ultrastructure.

METHODS

hBM-MSCs were immobilised in APA microcapsules to further characterise their viability, metabolic activity, proliferation, VEGF-secretability, and morphology.

RESULTS

The VEGF produced by monolayer hBM-MSCs increased significantly 1 d post-encapsulation, and was maintained for at least 4  weeks. TEM imaging of cells revealed well preserved ultrastructure indicating protein synthesis and high metabolic activity.

CONCLUSION

Although APA microencapsulation did not support 100% of fully viable hBM-MSCs for long-term cultures, it was conceived to enhance both VEGF secretion and metabolic activity while not losing their stemness characteristics.

Utilizing core-shell fibrous collagen-alginate hydrogel cell delivery system for bone tissue engineering

Three-dimensional matrices that encapsulate and deliver stem cells with defect-tuned formulations are promising for bone tissue engineering. In this study, we designed a novel stem cell delivery system composed of collagen and alginate as the core and shell, respectively. Mesenchymal stem cells (MSCs) were loaded into the collagen solution and then deposited directly into a fibrous structure while simultaneously sheathing with alginate using a newly designed core-shell nozzle. Alginate encapsulation was achieved by the crosslinking within an adjusted calcium-containing solution that effectively preserved the continuous fibrous structure of the inner cell-collagen part. The constructed hydrogel carriers showed a continuous fiber with a diameter of ~700-1000 μm for the core and 200-500 μm for the shell area, which was largely dependent on the alginate concentration (2%-5%) as well as the injection rate (20-80 mL/h). The water uptake capacity of the core-shell carriers was as high as 98%, which could act as a pore channel to supply nutrients and oxygen to the cells. Degradation of the scaffolds showed a weight loss of ~22% at 7 days and ~43% at 14 days, suggesting a possible role as a degradable tissue-engineered construct. The MSCs encapsulated within the collagen core showed excellent viability, exhibiting significant cellular proliferation up to 21 days with levels comparable to those observed in the pure collagen gel matrix used as a control. A live/dead cell assay also confirmed similar percentages of live cells within the core-shell carrier compared to those in the pure collagen gel, suggesting the carrier was cell compatible and was effective for maintaining a cell population. Cells allowed to differentiate under osteogenic conditions expressed high levels of bone-related genes, including osteocalcin, bone sialoprotein, and osteopontin. Further, when the core-shell fibrous carriers were implanted in a rat calvarium defect, the bone healing was significantly improved when the MSCs were encapsulated, and even more so after an osteogenic induction of MSCs before implantation. Based on these results, the newly designed core-shell collagen-alginate fibrous carrier is considered promising to enable the encapsulation of tissue cells and their delivery into damaged target tissues, including bone with defect-tunability for bone tissue engineering.

Nutraceutical use of garlic sulfur-containing compounds

Garlic is one of the world's oldest medicines that has been employed not only for flavouring but also as a medical herb for its prophylactic and therapeutic actions. Most garlics' beneficial effects are due to the presence of the organosulphate molecule allicin. Allicin is a highly unstable molecule and, during processing, is rapidly transformed into a variety of organosulfur components. The enzyme alliinase, which is responsible for the conversion of alliin to allicin, is irreversibly destroyed at the acidic environment of stomach. This is the reason why most garlic supplements contain garlic powder or granules, but do not contain allicin itself. Garlic alliinase could be encapsulated and coated with materials which would protect it in the harsh conditions of the stomach. The objective of this chapter is to summarize the most important garlic health benefits and to discuss promising encapsulation/stabilization approaches.

Alginate immobilization of recombinant Escherichia coli whole cells harboring L-arabinose isomerase for L-ribulose production

Recombinant Escherichia coli whole cells harboring Bacillus licheniformis L-arabinose isomerase (BLAI) were immobilized with alginate. The operational conditions for immobilization were optimized with response surface methodology. Optimal alginate concentration, Ca(2+) concentration, and cell mass loading were 1.8% (w/v), 0.1 M, and 44.5 g L(-1), respectively. The interactions between Ca(2+) concentration, alginate concentration, and initial cell mass were significant. After immobilization of BLAI, cross-linking with 0.1% glutaraldehyde significantly reduced cell leakage. The half-life of immobilized whole cells was 150 days, which was 50-fold longer than that of free cells. In seven repeated batches for L-ribulose production, the productivity was as high as 56.7 g L(-1) h(-1) at 400 g L(-1) substrate concentration. The immobilized cells retained 89% of the initial yield after 33 days of reaction. Immobilization of whole cells harboring BLAI, therefore, makes a suitable biocatalyst for the production of L-ribulose, particularly because of its high stability and low cost.