Characterization of Core-Shell Alginate Capsules

Abstract

A new droplets millifluidic/inverse gelation based process was used to produce core-shell alginate milli-capsules. Water-in-oil (W/O) emulsion dispersed phase containing Ca 2+ ions was directly injected into a continuous alginate phase to generate a secondary W/O/W emulsion. Due to the cross-linking of alginate molecules by Ca 2+ ions release, core-shell milli-capsules were formed with a very high oil loading. The influence of the curing time and of the storage conditions on capsules physico-chemical properties were investigated. It was first found as expected that alginate membrane thickness increased with curing time in the collecting bath. However, a plateau was reached for the higher curing times, in close relation with previous observations (Martins, Poncelet, Marquis, Davy, & Renard, 2017b) that an external oil layer surrounded the surface of W/O emulsion drops that acted as a barrier and hindered the release of aqueous CaCl 2 droplets during curing time. Compression experiments on individual capsules revealed that alginate membrane thickness was inversely related to its mechanical properties, i.e. the thicker membrane, the lower surface Young modulus. Surface Young modulus ranged from 61 to 26 N/m at curing times of 3 and 45 min, respectively. This result was explained in terms of enhanced swelling properties of alginate membrane with curing time or storage conditions. Drying capsules led to much more resistant membranes due to the loss of water. Oil loading of 80 wt% was obtained for dry capsules whatever the conditions used.

Alginate Core–Shell Capsules for 3D Cultivation of Adipose-Derived Mesenchymal Stem Cells

“…Capsules produced with a CMC core had an outer diameter of 3.10 ± 0.13 mm and an inner diameter of 2.39 ± 0.12 mm directly after casting, which were both significantly larger than those of the produced XG capsules, with an outer diameter of 2.86 ± 0.11 mm and inner diameter of 1.85 ± 0.11 mm (see Figure 3 ). Although the same Ca 2+ and alginate concentrations were used, which have been shown to determine shell thickness [ 31 , 32 ], XG samples presented a significantly thicker shell of 0.51 ± 0.04 mm compared to 0.36 ± 0.05 mm for CMC. Alginate has previously been reported to swell during cultivation; therefore, we compared the sizes of the capsules directly after production and 4 days at culture conditions (100 RPM, 37 °C, 5% CO 2 ).…”

Hydrogel capsules as new delivery system for Trichoderma koningiopsis Th003 to control Rhizoctonia solani in rice (Oryza sativa)

“…Pectin have provided desiccation tolerance to several types of cells, including conidia of Trichoderma strains (Cortés et al 2021). Similarly, dried alginate-based capsules mitigated dehydration stress on cells due to resistant membranes, and they dried essentially as a water droplet (Pereda et al 2019). These properties could contribute to the microbial survival within the capsules by creating a microenvironment that isolates the conidia from water vapor or reactive oxygen agents.…”

CLytA-DAAO Chimeric Enzyme Bound to Magnetic Nanoparticles. A New Therapeutical Approach for Cancer Patients?

“…The enzyme has also been immobilized by alginate capsules trapping. Alginate is one of the most widely used polymers in encapsulation due to its high versatility and biocompatibility and because the gel capsules generated protect the immobilized component, increasing its stability and bioavailability [ 44 ]. This method has been proven to be less effective retaining CLytA-DAAO activity than MNPs ( Figure 1 A), maybe because the alginate trap interferes with the interaction between the enzyme and the cells, or because part of the H 2 O 2 produced is trapped in the alginate and do not reach the cells.…”