Mechanical Stability Of Microcapsules Research Articles

Benefits of cryopreservation as long-term storage method of encapsulated cardiosphere-derived cells for cardiac therapy: A biomechanical analysis

Cardiosphere-derived cells (CDCs) encapsulated within alginate-poly-L-lysine-alginate (APA) microcapsules present a promising treatment alternative for myocardial infarction. However, clinical translatability of encapsulated CDCs requires robust long-term preservation of microcapsule and cell stability, since cell culture at 37 °C for long periods prior to patient implantation involve high resource, space and manpower costs, sometimes unaffordable for clinical facilities. Cryopreservation in liquid nitrogen is a well-established procedure to easily store cells with good recovery rate, but its effects on encapsulated cells are understudied. In this work, we assess both the biological response of CDCs and the mechanical stability of microcapsules after long-term (i.e., 60 days) cryopreservation and compare them to encapsulated CDCs cultured at 37 °C. We investigate for the first time the effects of cryopreservation on stiffness and topographical features of microcapsules for cell therapy. Our results show that functionality of encapsulated CDCs is optimum during 7 days at 37 °C, while cryopreservation seems to better guarantee the stability of both CDCs and APA microcapsules properties during longer storage than 15 days. These results point out cryopreservation as a suitable technique for long-term storage of encapsulated cells to be translated from the bench to the clinic.

Formulation & stability of Lactobacillus acidophilus microcapsules with a clinical trial for treatment and eradication of Helicobacter pylori infections

Probiotics are live microorganisms that administered through the digestive tract, have a positive impact on the hosts health. In this study research has shown that extraction method (encapsulation in alginate systems) can be used as an effective method for preparation of immobilized Lactobacillus acidophilus. All formulas were studied, from characterization, encapsulation yield, particle size measurement and mechanical stability of microcapsules in simulated gastric conditions which resulted that alginate – starch microcapsules gave the best results. based on this finding that starch – alginate can be used to protect living microbes, alginate starch microcapsules has been further studied for: efficacy of cell release, thermal stability ( refrigeration and shelf life ) which achieved good results. Finally the selected formula was added to standard anti- Helicobacter pylori therapy (triple therapy) in a parallel clinical study (42 patients) which showed that the addition of Lactobacillus acidophilus has a significant effect in increasing the eradication rate of Helicobacter pylori.

Alginate encapsulation of genetically engineered mammalian cells: Comparison of production devices, methods and microcapsule characteristics

Primary objective: Microencapsulation is a novel method for in vivo immunoprotection of genetically engineered mammalian cells. This study aimed at optimizing alginate/poly-L-lysine/alginate (APA) microencapsulation of mammalian cells in small size (<300μm) hollow core microcapsules and at evaluating some of the physical characteristics of APA microcapsules produced by different devices and with different alginate preparations.Methods and procedures: Alginate preparations with higher or lower viscosity were used with three different methods: (i) vibrating nozzle, (ii) coaxial gas flow extrusion (AirJet) and (iii) laminar jet break-up (JetCutter). Parameters and device settings for the production of microcapsules with specific characteristics were defined for all three methods. Mechanical stability of APA microcapsules and cell viability of encapsulated cells were investigated in long-term culture and in an animal model.Main results: Uniform spherical beads with a mean diameter <300μm could be produced by all three encapsulation methods. For the production of uniform microcapsules with a small diameter (<300μm) the vibrating nozzle technique required a relatively low viscosity of alginate (<0.2 Pa/s), while the AirJet and JetCutter devices performed equally well with alginate of higher viscosity. In all cases, alginate with a lower molar mass was inferior to higher molar mass alginate in terms of mechanical stability of the microcapsules. Microcapsules with optimized mechanical properties were injected intravascularly in rats and shown to maintain their shape and the viability of encapsulated cells.Conclusions: The described methods and devices are able to produce APA microcapsules of small size and uniform shape which are mechanically stable in culture and may maintain the viability of the enclosed cells over extended periods of time. These microcapsules seem to be suitable for further therapeutic studies in an animal model of human disease.

Purification of polymeric biomaterials.

Employing a combined filtration and precipitation method, the endotoxin concentration in sodium alginate (SA) and sodium cellulose sulfate (SCS) was reduced to a value of 200 EU/g polymer. This is one tenth of the regulatory threshold calculated, for example, for an appropriate bioartificial pancreas that consists of approximately 420,000 encapsulated islets of Langerhans. The low endotoxin (ET) levels were maintained below this threshold during a six-month storage period. The purification procedure of the polymers did not negatively influence the final microcapsule properties. The mechanical stability of microcapsules from purified material is even slightly higher than that of microcapsules from the original polymers. A second approach to avoid endotoxin release from the device is its direct complexation during the bead or capsule formation process. The durability of endotoxin binding in binary, ternary, and quaternary complexes could be demonstrated for storage in culture medium and saline. Very low total endotoxin release from the complexes was detected after three months in culture medium and five months in saline. This complexation is primarily based on electrostatic interactions with the participating cationic components and provides additional security for the final bioartificial organ or delivery device.