Production of monodisperse silica gel microspheres for bioencapsulation by extrusion into an oil cross-flow

Abstract

Silica gel microspheres are ideal materials for bioencapsulation due to their mechanical properties, biocompatibility, and stability. Encapsulated cells are isolated from the environment and protected from predators, changes in pH, and osmotic stress. However methods for the production of silica gel microspheres suitable for bioencapsulation are not well established. This paper describes a method for the production of monodisperse silicon alkoxide cross-linked silica nanoparticle (SNP) gel microspheres for bioencapsulation in which silica gel precursor is extruded from a needle into a cross-flowing stream of mineral oil. Microspheres produced ranged from 1.3 to 2.9 mm in diameter with coefficients of variation ranging from 2 to 6%. Microsphere size was mainly controlled by the flowrate of the cross-flowing oil and smaller microspheres generally had larger coefficients of variation. The method described in this paper can be optimised to produce silica gel microspheres with a diverse range of compositions and properties.

Keywords:

• Silica gel
• microsphere
• sol-gel
• emulsion
• bioencapsulation

Acknowledgements

The authors thank Ms. Sujin Yeom for growing the bacteria used in this research.

Disclosure statement

This research has been funded through a University of Minnesota IonE Discovery grant and a MnDRIVE Transdisciplinary Initiative of the University of Minnesota. Dr. Aksan and Wackett own equity in, and are entitled to royalties from, Minnepura Technologies Inc., a company involved in the development, commercialisation and marketing of patented encapsulated biological platforms for water treatment. The University of Minnesota also has equity and royalty interest in Minnepura. These interests have been reviewed and managed by the University of Minnesota in accordance with its conflict of interest policies.