User:Dgund/Inorganic biology

Inorganic biology is an interdisciplinary branch of chemistry and engineering with the goal of developing self-replicating and evolving cells from inorganic chemicals. This interdisciplinary field encompasses the effort to create complex chemical cells with lifelike properties, combining disciplines such as biochemistry, inorganic chemistry, molecular biology, supramolecular chemistry, and synthetic biology. The existence of inorganic life is unprecedented, as all known forms of life, studied within biology and organic chemistry, contain organic chemicals.

Inorganic biology, with its objective of creating living architectures, stands to redefine evolutionary biology by proving that evolution is more than a biological process and that the definition of life can extend to inorganic material. This would also impact the engineering of metamaterials by introducing the idea of evolutionary design where complex and smart materials are grown and evolved through self-assembly, a process cheaper and easier than direct manufacturing. Additionally, lifelike inorganic cells and materials would advance fields that rely on intelligent and easily-produced technologies, including architecture, biotechnology, computing, medicine, and nanotechnology.

History
Inorganic biology has only appeared recently as a field, stemming from advancements in self-assembly of chemical networks and the growth of knowledge about molecular processes. The first use of the term appears in the opening lecture by Professor Leroy Cronin at a TEDGlobal conference in 2011 in Edinburgh. In his presentation, Cronin detailed his team's work at the University of Glasgow to create inorganic life:"Now this may seem a bit ambitious, but when you look at yourself, you look at your hands, you realize that you're alive. So this is a start. Now this quest started four billion years ago on planet Earth. There's been four billion years of organic, biological life. And as an inorganic chemist, my friends and colleagues make this distinction between the organic, living world and the inorganic, dead world. And what I'm going to try and do is plant some ideas about how we can transform inorganic, dead matter into living matter, into inorganic biology."Established in 2002, the Cronin Group has been focused on developing "complex chemical systems derived from non biological building blocks to have a major impact on our fundamental understanding of the interplay of chemical systems and to revolutionise modern technologies." The group works within the research areas of hybrid devices, led by Dr. Marie Hutin, inorganic biology, led by Dr. Geoff Cooper, molecular fundamentals, led by Dr. De-Liang Long, and synthetic systems, led by Dr. Haralampos Miras. The group contains over 50 members within the WestCHEM Research School of Chemistry and has spawned external research projects by others.

Research
Research efforts within inorganic biology consist of focused experimentation into the different components and assembly methods for a potential inorganic cell or architecture. In all, the field aims to create "an inorganic Lego kit of molecules" that can be combined into larger macromolecules that function as proteins and nucleic acids, forming the building blocks for life. This toolbox of inorganic components, containing hybrid polyoxometalates in multiple forms, molecular metal oxides, and other coordination compounds, would allow for the engineering of a variety of complex chemical systems. These systems would have emergent properties stemming from their different components, giving rise to living inorganic material.

In order for a system to be considered as living, the general consensus is that it requires some form of containment such as a membrane, some means of obtaining material from the environment to facilitate growth and replication, some form of information storage, and the ability to pass that information into subsequent generations in a form of evolution. Inorganic biologists envision utilizing the various molecules in their toolbox to meet these constraints, developing metal oxide membranes for containment, osmotically-driven morphogenesis for growth and replication, molecular metal oxides for information storage. The overarching goal is an inorganic chemical cell capable of lifelike function.

Inorganic chemical cells
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Molecular metal oxides
Molecular metal oxides (MMOs) are a new class of metal oxides that are structured as molecules rather than polymers. Their properties can differ radically from their bulk metal oxide analogues. Traditional bulk metal oxides, including titanium dioxide and indium tin oxide, have a multitude of contemporary uses, including electronics, transparent conducting oxides, and catalysis. Metal oxides are valued for their applications, but there are significant costs attached to their production, such as the need for high temperature processing. Molecular-level processing aims to lower the costs and difficulty of construction. The goal is to develop MMO building blocks with controllable sizes and elemental compositions, which can be manipulated and doped later on to induce specific functionality such as electrical conductivity, host-guest chemistry, redox potential, and magnetism. These MMOs can be used as transferable kit of synthons for the construction of larger functional architectures.

Polyoxometalate self-assembly
Polyoxometalates (POMs) are a subclass of metal oxides that consist of three or more transition metal oxyanions linked by shared oxygen atoms to form closed three-dimensional frameworks. POMs exhibit diverse physical properties and the ability to form structures that can range in size from the nano to the micrometer scale. In particular, the metal atoms composing the POM, usually molybdenum, tungsten, vanadium, or niobium, influence its properties. POMs exhibit many traits that make them attractive for applications in catalysis, including chemical transformation, molecular conductivity, magnetism, luminescence, photochromism, and electrochromism. As a result, they have been found to be extremely versatile building blocks for the construction of an inorganic living architecture.

Polyoxometalate-based tubular architectures
POM crystals are notable for their property of spontaneously self-assembling into micrometer-scale tubular architectures when immersed in an aqueous solution containing a low concentration of a cationic, or positively-charged, component. The POM crystals are anionic, or negatively-charged, and only somewhat soluble, so as the outer layers of the crystals begin to dissolve, a semipermeable membrane is formed around the crystal shell. The membrane allows for the diffusion of water, while preventing the entrance of the cation-containing solute or escape of any anionic POM material. Within minutes, the increasing pressure and electrostatic differential ruptures the membrane, ejecting pressurized jet of a POM-enriched solvent. This polyanionic material is precipitated by the cationic component in the solvent, forming a tubular channel. The osmotic pressure within the crystal generates a continuous flow of dissolved material along this tube, driving growth until only a hollow shell remains. This self-assembly of the tubular architecture occurs via a deposition process, as the combination of the anionic and cationic components at the end of the tube results in further growth, while the continuous flow of new material prevents closure.

POM-based tubular architectures tubes have potential applications in many areas, including microfluidic devices and the development of metal oxide-based semipermeable membranes. In a potential inorganic cell, they could serve as a fluid-carrying component as well as mimicking structural microtubules in our own cells. Their ability to self-assemble is extremely valuable in that this bottom-up growth on the molecular level results from natural processes and requires no artificial interaction. The tubular architecture growth rate and diameter can be controlled in real-time through manipulation of the concentration of the cationic component within the system. Physical manipulation of the growing tubular architecture with a micromanipulator allows for controlled branching, and the injection of fluorescent dye has proven that the microtubes remain hollow and leak-free after growth.

There has been no one established method for directing tubular architectures growth. Under normal circumstances, all of the microtubes in the system collectively grow in the arbitrary direction of flows existing within the system.

Evolutionary biology
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Information storage
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Parallel computing
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Smart materials and design
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