- © The Mineralogical Society Of America
In the past few years, many efforts have been made to take advantage of the biological activities of living cells to design functional materials. Applications in biotechnology and biomedical devices include the development of biosensors, i.e., the detection of analytes through the specific response of cells, and biocatalysts or bioreactors, i.e., the transformation or production of specific medical molecules by cells. In many cases, living cells cannot be used as such and need to be stabilized via encapsulation in suitable host matrices. Although polymer-based matrices have long been used for such applications, recent studies indicate that mineral hosts, and more specifically oxide gels, may also be suitable for cell encapsulation. Not only can cell viability be maintained over weeks within such matrices, but inorganic materials present enhance chemical and mechanical stability when compared to organic networks. In this chapter, we will provide a brief history on the development of sol-gel chemistry, followed by a review of the most recent advances in methods for cell immobilization in oxide gels. We will also briefly compare these synthetic routes to naturally-occurring silica fossilization of cells and laboratory experiments mimicking fossilization.
According to the Roman historian Pliny, glasses were discovered by Egyptian sailors about 5000 years ago. They were making fire on a beach when they saw that the sand under the fire was melting, giving a kind of glassy material. Actually, some sodium carbonate rocks (a glass modifier) were mixed with the silica sand (a glass former) decreasing the melting temperature of the SiO2-Na2O eutectic below 1000 °C. Egyptian glasses were very rough materials, but much progress has been made since then. Large pieces of highly transparent glasses are now currently produced via the so-called “float-glass process” discovered about fifty years ago. However, glasses are still made from a …