Biogenic Silica: An Inspiration to Nanotechnology

Biogenic Silica: An Inspiration to Nanotechnology

Silica is an inorganic amorphous oxide formed by polymerization processes and makes up opal phytoliths in plants. Opal phytoliths are one of several kinds of natural artifacts formed by nature to preserve its most beautiful creations in a green and environmental friendly way.

The presence of biogenic silica during the life cycle of a plant is dependent on the uptake of monosilicic acid from groundwater, its super saturation, polymerization and subsequent deposition as amorphous, hydrated, polymerized silicic acid at sites within the inter- or intra-cellular vegetative structure of a plant, resulting in three-dimensional positive or negative forms. These phytoliths may remain on the ground surface to become incorporated into the soil horizon and subsequently be buried to form part of the stratigraphic matrix. These buried phytoliths survive well in many environments, so they can inform on past vegetation and are particularly important when reconstructing economic plant resources using material from archaeological sites.  The present work elucidates siliceous deposition in monocots especially plants of poaceae and musaceae family, being a rich source of opal silica have potentials to provide basic biogenic technology to nanomaterial synthesis. We prepared a phytolith reference collection of modern plants mostly belonging to family Poaceae and Musaceae that includes qualitative information on phytolith morphological assemblages. The comparison indicates that some aspects of phytolith production are probably genetically controlled, whereas others are environmentally controlled. Silica bodies can be created in the cells of any part of any plant--the roots, the leaves, the stem, the fruit--and in any kinds of cells--hair follicles, skin and sub-skin cells, the works. Different species and families of plants deposit the silica in different places, so that some species have most of their silica bodies in the skin cells of leaves, while others deposit them in the hair cells of their roots. Still others don't produce silica bodies at all.

There has been much research to gain new insights into its biochemistry and to mimic biosilicification. Studies carried out on plant silica bodies, silica uptake mechanisms and applications; suggest possible ways of producing plant silica bodies with new functions. Silica bodies offer complementary properties to diatoms for nanotechnology, including large-scale availability from crop wastes, lack of organic impurities (in some), microencapsulation and microcrystalline quartz with possibly unique optical properties. Silica nanoparticles have proven to be important for several biotechnological and biomedical applications, such as biosensor design, drug delivery, cell labeling, cell separation, contrast agents for magnetic resonance and ultrasound medical imaging, and as a targeting and therapeutic platform for drug- or enzyme-released systems. Also, the various shapes formed by silica deposition in plants laid the foundation of what we call bio mimicry. Plants and other biological organisms make silica in amounts of gigatons per annum, whereas industrial processes only produce mere megatons.

The biogenetic production is now of high interest due to simplicity of the procedures and their versatility and involves pure green chemistry. The production of nanoparticles is environmentally friendly, because this involves natural phenomena that take place in the biological systems. Moreover, the biologically fabricated nanostructures offer substantially better properties. 

Credits: Article contributed by Soumya Jain