Alginate bead fabrication and encapsulation of living cells under centrifugally induced artificial gravity conditions

Abstract

This study presents a novel method for the direct, centrifugally induced fabrication of small, Ca²⁺-hardened alginate beads at polymer-tube micronozzles. The bead diameter can arbitrarily be adjusted between 180–800 µm by the nozzle geometry and spinning frequencies between 5–28 Hz. The size distribution of the main peak features a CV of 7–16%, only. Up to 600 beads per second and channel are issued from the micronozzle through an air gap towards the curing agent contained in a standard lab tube (‘Eppi’). Several tubes can be mounted on a ‘flying bucket’ rotor where they align horizontally under rotation and return to a vertical position as soon as the rotor is at rest. The centrifugally induced, ultra-high artificial gravity conditions (up to 180 g) even allow the micro-encapsulation of alginate solutions displaying viscosities up to 50 Pa s, i.e. ∼50 000 times the viscosity of water! With this low cost technology for microencapsulation, HN25 and PC12 cells have successfully been encapsulated while maintaining vitality.

Key Words: :

• Centrifugal
• micronozzle
• droplet formation
• alginate bead
• cell encapsulation