Encapsulation of 5. cerevisiae in Poly(glycerol) Silicate Derived Matrices: Effect of Matrix Additives and Cell Metabolic Phase on Long-Term Viability and Rate of Gene Expression

摘要

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 Irving cell studies, and provide important design parameters for developing effective living cell-based biosensors for case-specific detection applications.