Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition – a facile method for encapsulation of diverse cell types in silica matrices

Abstract

In nature, cells perform a variety of complex functions such as sensing, catalysis, and energy conversion which hold great potential for biotechnological device construction. However, cellular sensitivity to ex-vivo environments necessitates development of bio-nano interfaces which allow integration of cells into devices and maintain their desired functionality. In order to develop such an interface, the use of a novel Sol Generating Chemical Vapor into Liquid (SG-CViL) deposition process for whole cell encapsulation in silica was explored. In SG-CViL, the high vapor pressure of tetramethyl orthosilicate (TMOS) is utilized to deliver silica into an aqueous medium, creating a silica sol. Cells are then mixed with the resulting silica sol, facilitating encapsulation of cells in silica while minimizing cell contact with the cytotoxic products of silica generating reactions (i.e. methanol), and reduce exposure of cells to compressive stresses induced from silica condensation reactions. Using SG-CVIL, Saccharomyces cerevisiae (S. cerevisiae) engineered with an inducible beta galactosidase system were encapsulated in silica solids and remained both viable and responsive 29 days post encapsulation. By tuning SG-CViL parameters thin layer silica deposition on mammalian HeLa and U87 human cancer cells was also achieved. The ability to encapsulate various cell types in either a multi cell (S. cerevisiae) or a thin layer (HeLa and U87 cells) fashion shows the promise of SG-CViL as an encapsulation strategy for generating cell-silica constructs with diverse functions for incorporation into devices for sensing, bioelectronics, biocatalysis, and biofuel applications.

Control over Silica Particle Growth and Particle–Biomolecule Interactions Facilitates Silica Encapsulation of Mammalian Cells with Thickness Control

“…Silica sols were generated by performing SG-CViL for 20 min at 23°C in 1× PBS pH 7.4, adding 1 μM Rhodamine B to the sample chamber prior to SG-CViL initiation to fluorescently label silica. 23 Spermidine coated S. cerevisiae and Jurkat cells were resuspended in 1 mL fluorescently labeled silica sol for 10 min at 30°C in a shaking incubator. Cells were washed twice via centrifugation and resuspension in 1 mL 1× PBS and imaged using Olympus FE10i laser scanning confocal microscope system using a 60× water objective.…”

“…Post staining, cells were washed twice with 1× PBS and incubated with 1× PBS, pH 7.4, containing 200 μM spermidine for 5 min at 30 °C in a shaking incubator. Silica sols were generated by performing SG-CViL for 20 min at 23 °C in 1× PBS pH 7.4, adding 1 μM Rhodamine B to the sample chamber prior to SG-CViL initiation to fluorescently label silica . Spermidine-coated S. cerevisiae and Jurkat cells were resuspended in 1 mL of fluorescently labeled silica sol for 10 min at 30 °C in a shaking incubator.…”

“…23–24 In SG-CViL, silica sols are generated via deposition of an alkoxysilane vapor into buffer, and then aged. Aging allows evaporation of harmful reaction constituents (i.e.…”

“…One encapsulation process with the potential to meet this need is the Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition approach. , In SG-CViL, silica sols are generated via deposition of an alkoxysilane vapor into buffer and then aged. Aging allows evaporation of harmful reaction constituents (i.e., methanol) and polymerization of cytotoxic tetramethyl­orthosilicate (TMOS) monomers, greatly increasing sol biocompatibility.…”

“…Aging allows evaporation of harmful reaction constituents (i.e., methanol) and polymerization of cytotoxic tetramethyl­orthosilicate (TMOS) monomers, greatly increasing sol biocompatibility. Subsequent mixing of aged silica sols with cell suspensions results in cell encapsulation in either large silica species, or deposition of thin silica films on cell surfaces, with maintained cell viability and functionality . The encapsulation of cells in distinct silica morphologies through variation of SG-CViL parameters indicates the ability; to control the thickness of the cell encapsulating matrix; however, leveraging this ability requires understanding the mechanisms governing SG-CViL silica particle generation and subsequent interaction with phospholipid assemblies.…”