Electrostatic Droplet Generator with 3-Coaxial-Nozzle Head for Microencapsulation of Living Cells in Hydrogel Covered by Synthetic Polymer Membranes

Abstract

The current methods allow for encapsulation of cells inside spherical microcapsules made of a matrix covered by a permselective membrane using an electrostatic droplet generator with 1-nozzle or 2-nozzle heads. However, some potentially useful materials for the outer membranes cannot be put into direct contact with hydrophilic core filled by cells during the manufacturing process. Therefore, we designed a novel 3-coaxial-nozzle head that allows for the third fluid to separate the core material from the membrane material. The equipment was applied for manufacturing spherical microcapsules comprised of cell-friendly alginate core surrounded by semipermeable polyethersulfone membrane. The obtained microcapsules had a diameter between 0.84 mm and 1.79 mm, and the diameter correlated negatively with the applied electric voltage. The thickness of the membrane varied from 171 µm to 450 µm. The SEM images of the interior of microcapsules revealed highly porous membrane structure typical for synthetic membranes obtained by a wet phase inversion method. Bakery yeast cells encapsulated inside the alginate-polyethersulfone microcapsules retained their proliferation ability proving the effectiveness and safety of this encapsulation technique.

Keywords:

• alginate
• electrostatic technique
• microcapsule
• microencapsulation
• polyethersulfone

ACKNOWLEDGEMENTS

The authors would like to thank Mr. Krzysztof Matuszak from the KENDRO Lim., Mrs. Jasmin Adler and Mr. Marcus Brückner from the Leica Microsystems Nussloch GmbH for the kind help with the microcapsule specimens’ preparation.

Notes

*The AGP-33 sample was made under different pressure conditions: P1 = 12.16, P2 = 70.91 and P3 = 2.03 kPa.

Abbreviations: U – electric voltage, D_A – microcapsule average diameter, VC D_A – variation coefficient of microcapsule average diameter: A – the minimum thickness of the membrane, B – the average thickness of the membrane, N – the maximum thickness of the membrane.

Abbreviations: f – frequency of electric impulses, τ - impulse duration, v₃ – flow rate of polyethersulfone solution.

Additional information

Notes on contributors

A. Weryński†

†Deceased – Andrzej Weryński, Nate¸cz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences