Encapsulation of S. cerevisiae in Poly(glycerol) Silicate Derived Matrices: Effect of Matrix Additives and Cell Metabolic Phase on Long-Term Viability and Rate of Gene Expression

Abstract

Bioencapsulation of living cells into silica materials derived from the sol–gel process has resulted in novel hybrid living materials with exciting functionalities. Despite the many successes in this field, long-term viability and activity of the encapsulated cells remain a significant obstacle to producing practical and robust devices, e.g., whole-cell-based biosensors. We report the first study on the effects of various media additives and the metabolic phase of encapsulated cells on long-term viability and the rate of inducible gene expression. Saccharomyces cerevisiae (S. cerevisiae) cells, genetically engineered to produce yellow fluorescent protein (YFP) in response to galactose, were encapsulated in poly(glycerol) silicate derived matrices. Surprisingly, we find that addition of media components to the glycerol-silica matrix adversely impacted long-term viability in all cases studied, with a 1.3, 1.4, or 5.4 fold decrease in viability after only 9 days of storage in matrices containing yeast peptone dextrose (YPD), yeast peptone (YP, no glucose), or Synthetic Complete (SC) +2% glucose media, respectively. These findings are attributed to the media components inducing exit of the cells from the more robust quiescent state, and the metabolic production of toxic byproducts. Encapsulated cells from exponential culture exhibited inducible reporter gene expression rates approximately 33% higher than cells from stationary cultures. Addition of media components to the silica matrix increased gene expression rates under certain conditions. These results further elaborate on other silica matrix encapsulated living cell studies, and provide important design parameters for developing effective living cell-based biosensors for case-specific detection applications.

Spray-Dried Multiscale Nano-biocomposites Containing Living Cells

“…There is also the potential that the more rigid NBC nanostructure could exert significant mechanical stress upon the bacteria during spray drying, where capillary (drying) stresses and continued condensation of the silica framework would impose compressive stresses on the cells. 3 We hypothesized that this profound three-dimensional mechanical constraint might induce unique physiological responses in the encased bacteria. It has been shown that a complex relationship exists between mechanical stress and the viable but not culturable (VBNC) state: VBNC can be induced by mechanical stresses such as high pressure, 58 while a pre-existing VBNC state can cause resistance to mechanical stress-induced killing.…”

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

“…The lack of distinguishable structural order of silica species in Fig. 4, along with x-ray diffraction data (data not shown), indicates that overall, SG-CViL conducted at 1 hour TMOS deposition time does not lead to bulk gelation as in other systems, 13, 15 but generates silica species with amorphous structure.…”

Implementation of a Simple Nanostructured Bio‐electrode with Immobilized Rhus Vernicifera Laccase for Oxygen Sensing Applications

“…The enzyme immobilization was performed in polyglycerol silicate (PGS) polymer synthetized accordingly to Harper et al. (2011) . Laccase solution (25 mg ml −1 in distilled water) was mixed in the same proportion with carbon additive solution and 10 μl were dropcasted over the reduced graphene surface and left to dry for 1 hour at ambient temperature.…”