Biomod/2015/Tianjin/Idea

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Contents

Artificial cells

1. Evolution
Biology is underscored by two great principles: that all life is interconnected through a Darwinian evolution of random variation and selective retention, and that cellularity is the fundamental and universal organizational unit of life. But all current knowledge of biology

cannot explain how the origin of life appeared and the base of the reconstructed tree of life is still impenetrable and mysterious.

So there are left with two momentous challenges: how did the transition from inanimate matter to the first forms of living matter occur on the early earth? And can a similar transition be realized ex novo in the laboratory?

Scientist kept working on artificial cells based on the compartmentalization with the ability of metabolism and self-replication to explore the origin of life.


Figure 1. Roadmap of artificial life


2.Micro biochemical reactor

The artificial cells have a lot of unique advantages as micro biochemical reactors. The size can be made in micrometer as the same as the mammalian cells. The workspace is relatively independent due to the compartmentalization feature. And the structure and function is really simple compared with the real cells. By rational design the composite of the cytoplasm, the artificial cells can be highly controlled and programmed.



Figure 2. Microfluidic droplets based artificial cell


Cell-free system


Cell-free system is emerging as a powerful tool aimed to understand, simulate, and expand the capabilities of natural biological systems without using intact cells.

Cell-free systems offer several advantages over traditional cell-based expression methods, including the easy modification of reaction conditions to favor protein folding, decreased sensitivity to product toxicity and suitability for high-throughput strategies because of reduced reaction volumes and process time.

Significant improvements made to the configuration, energetics and robustness of reactions have led to productivities that far surpass the milligram levels of product per milliliter of reaction. Also, the ability to easily manipulate the reaction components and conditions makes in vitro protein synthesis particularly amenable to automation and miniaturization, enabling application to the fields of protein arrays, in vitro evolution and multiplexed real-time labeling, among others.

Although any organism could potentially be used as a source for the preparation of a cell-free protein expression system, the most popular are those based on Escherichia coli, wheat germ and rabbit reticulocytes. The protein yields of E. coli-based systems range from a few micrograms up to several milligrams per milliliter of reaction, depending on the protein and the reaction format.


Type Advantages Disadvantages
E.coli extract High protein synthesis yield Limited post-translational modification
Simple and cost-effective
High rate of protein synthesis
Research clearly, easy to genetic modification
Able to fold complex protein
Wheat-germ extract Widely-spectrum expression of eukaryotic protein Low yield of extract from cells
High yield of complex protein Extract preparation is hard and complex
Poor genetic modification tools
Rabbit reticulocyte lysate Eukaryotic post-translational modification Poor genetic modification tools
Easy and quick preparation of extract Narrow spectrum of protein expressed and low protein synthesis yield
Insect cell extract Easy and quick preparation of extract Cell cultivation is expensive and time-cosuming
Eukaryotic post-translational modification Poor genetic modification tools
Signal sequence processing

Droplet


Droplet-based microfluidic system a potent high throughput platform for biomedical research and applications. Microfluidic technology can perform typical laboratory operations using a fraction of the volume of reagents in significantly less time. Reagents can be significantly reduced from milliliters and microliters to nanoliters and femtoliters whereas hours of reaction time could be decreased to mere seconds or less. Droplet microfluidics however, has the ability to perform a large number of reactions without increasing device size or complexity.

The uniform size and shape of microdroplets are obtained in a single-step process using microfluidic device. The size of microdroplets can be controlled through the changing continuous flow rate. The combination of microdroplet generation and chemical polymerization techniques provide unique environment to produce non-toxic ways of fabricating microorganism- encapsulated hydrogel microbeads.

Furthermore, non-toxic, gentle, and outstanding biocompatibility of microbeads, the encapsulated E. coli can be used in various applications including biotransformation, biosensing, bioremediation, and engineering of artificial cells.



Figure 3. Generation of microfluidic droplets


Motivation


This year, Tianjin Biomod team wants to construct a basic kind of artificial cell with the ability of transcription and translation in the cell-sized droplets. We want to achieve our goal by exploring two platforms—IVTT and microfluidic. We construct membrane-free compertmentalization uniformed diameter about 30μm by using droplets. To imitate cells in functions, we choose high efficiency E.coli lysate system and design different DNA molecules to express varies proteins. In order to control the yield of protein level, we want to optimize the composites and make our artificial cells more robust and program.


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