Bacteria Inside Semiconductors as Potential Sensor Elements: Biochip Progress

Abstract

It was discovered at the beginning of this Century that living bacteria—and specifically the extremophile Pseudomonas syzgii—could be captured inside growing crystals of pure water-corroding semiconductors—specifically germanium—and thereby initiated pursuit of truly functional “biochip-based” biosensors. This observation was first made at the inside ultraviolet-illuminated walls of ultrapure water-flowing semiconductor fabrication facilities (fabs) and has since been, not as perfectly, replicated in simpler flow cell systems for chip manufacture, described here. Recognizing the potential importance of these adducts as optical switches, for example, or probes of metabolic events, the influences of the fabs and their components on the crystal nucleation and growth phenomena now identified are reviewed and discussed with regard to further research needs. For example, optical beams of current photonic circuits can be more easily modulated by integral embedded cells into electrical signals on semiconductors. Such research responds to a recently published Grand Challenge in ceramic science, designing and synthesizing oxide electronics, surfaces, interfaces and nanoscale structures that can be tuned by biological stimuli, to reveal phenomena not otherwise possible with conventional semiconductor electronics. This short review addresses only the fabrication facilities' features at the time of first production of these potential biochips.

Interactions between Metal Oxides and Biomolecules: from Fundamental Understanding to Applications

“…Interest in GeO 2 has also developed from the biological point of view, where the aim is to understand the influence of microorganisms on mineral synthesis. The discovery of GeO 2 crystals templated by bacteria is suggested to have great potential in the sensor technology sector . As an example, biocrystals were grown from a Ge surface in the presence of Pseuodomonas syzygii bacteria submitted to a flow of water and UV light that allowed oxidation of Ge into GeO 2 , where the bacteria served as nucleation sites for square GeO 2 crystals …”

“…The stirring process during the synthesis has been shown to lead to a morphological elongation effect on amorphous GeO 2 particles, Figure C; however, this does not apply for crystalline materials, Figure I . The use of templating biomolecules that are able to form microemulsions, such as polyamines, leads to the formation of well-defined dispersed GeO 2 spherical particles, Figure (panels B and D). , Slight variations in precursor concentration and the presence of biomolecules has been shown to produce crystalline NPs of different morphologies, Figure (panels G and H). , Generally, germanium alkoxides are used as precursor molecules for directing GeO 2 condensation in the presence of biomolecules; however, the element itself, Ge has also been used to prepare crystalline GeO 2 using bacteria as the templating element, Figure Q …”

“…Copyright 2009 SAGE Publishing. (Q) Bacteria, reprinted with permission from ref . Copyright 2014 MDPI.…”

“…The discovery of GeO 2 crystals templated by bacteria is suggested to have great potential in the sensor technology sector. 633 As an example, biocrystals were grown from a Ge surface in the presence of Pseuodomonas syzygii bacteria submitted to a flow of water and UV light that allowed oxidation of Ge into GeO 2 , where the bacteria served as nucleation sites for square GeO 2 crystals. 633 One of the critical parameters for determining the interaction between metal oxides (or its precursor) and biomolecules is the surface charge.…”

“…633 As an example, biocrystals were grown from a Ge surface in the presence of Pseuodomonas syzygii bacteria submitted to a flow of water and UV light that allowed oxidation of Ge into GeO 2 , where the bacteria served as nucleation sites for square GeO 2 crystals. 633 One of the critical parameters for determining the interaction between metal oxides (or its precursor) and biomolecules is the surface charge. Several studies suggest that anionic germanate species resulting from an hydrolyzed precursor can interact with cationic groups like poly(allylamine hydrochloride), 97 phospholipids, 624 or chitin, 90 leading to precipitates of germania.…”