Quantitative study of the production and properties of alginate/poly-L-lysine microcapsules

Abstract

Alginate-polylysine-alginate (APA) microcapsules are of particular interest for their application as implants or for bioreactor cultures. Although their formation has been widely studied, there is still a lack of quantitative data describing resistance, membrance thickness and permeability. In this study, the quantitative application of a Texture Analyser for the measurement of capsule deformation yielded important results that permit comparison with other polymer systems used for encapsulation. Furthermore, single-membrane and multi-membrane capsules were formed in order to improve the modulation of the capsule properties. For single-membrane capsules, resistance was mostly a ected by the incubation time in poly-l-lysine (PLL), the PLL molecular weight and concentration. The increase in resistance from 0:1 § 0:01 g/capsules to 2 § 0:2 g/capsules was linked to a membrane thickening (35±120 mm) and a decrease in permeability (150 to 40 kD). Thus, it was not possible to modify resistance and membrane permeability independently. Multi-membrane capsules with a resistance comparable to single-membrane capsules could be formed using various combinations of PLL molecular weights, and enabled uncoupling of permeability and resistance properties.

Poly(vinyl alcohol)-heparin biosynthetic microspheres produced by microfluidics and ultraviolet photopolymerisation

“…32, 45, and 46) depending on the composition. Much effort has gone into increasing the mechanical strength of alginate based spheres by increasing the number of layers of alginate-PLL coatings 47 and also subsequent covalent crosslinking with chemical agents such as glutaraldehyde. 48 While all of these approaches have increased the strength to a degree, they all require multiple steps, which complicate the encapsulation process or introduce toxic crosslinking agents (e.g., glutaraldehyde), which have a detrimental effect on encapsulated cells.…”

Alginate Composition Effects on a Neural Stem Cell–Seeded Scaffold

“…26 Poly-L-lysine (PLL) coating is commonly employed as a means of strengthening the alginate bead and providing a barrier to immune system components such as IgG. 27,28 However, the PLL coating layer may itself cause an unfavorable foreign body response and slight toxicity to encapsulated cells, and its use remains controversial. 19,20,22,23,[29][30][31] In light of the extensive research indicating a relationship between alginate composition and encapsulated cell function, as well as the limited amount of data on NSC encapsulation in alginate, the effects of M=G content and PLL coating on entrapped cortical NSCs were investigated.…”

“…51 Therefore, although the G capsules may not burst, they may swell during exposure to an osmotic challenge, likely changing diffusion properties (which may, in turn, be related to their permissiveness to neurotrophic factor release). 27 The capsules in this study may be particularly vulnerable to swelling and saline effects due to the relatively low weight percentage used (1%); increased alginate concentration improves resistance to swelling. 50 Finally, the way in which mechanical stability is measured (i.e., rheology in the in vivo study and osmotic pressure in the in vitro study) is likely to affect results.…”

Development of a Blood Analog for the Hemodynamic Efficiency Evaluation of Cardiovascular Devices

“…The effects of a change in calcium concentration or a change of ions having a higher affinity such as barium (Ba 2+ ) and Strontium (Sr 2+ ) have not been covered in this work. Although it was not thoroughly studied in the present work, the presence of Na + ions may also contribute to the reduction of the elastic modulus of the microparticles [26] of about 63 %. A reduction the elastic modulus may contribute in a reduction of viscosity at shear rates >100s -1 (increased elastic deformation of the particles).…”

“…One is attributed to the fact that a suspension is generally non-Newtonian shear-thinning and the second is the presence of Ca 2+ ions that contribute to the aggregation of the micoparticles. From literature [26], once the crosslink between the Ca 2+ and alginic acid is made, there are still unlinked carboxylic binding sites where loose calcium ions can bind and unbind randomly. It is assumed that the presence of additional Ca 2+ ions produces a bridging effect between two or more particles.…”