Artificial biological cells

The lipid molecule is the main constituent of biological cell membranes. In aqueous solutions amphiphilic lipid molecules form self-assembled structures such as bilayer vesicles, inverse hexagonal and multi-lamellar patterns, and so on. Among these lipid assemblies, construction of the lipid bilayer on a solid substrate has long attracted much attention due to the many possibilities it presents for scientific and practical applications [4]. Use of an artificial lipid bilayer often gives insight into important aspects ofbiological cell membranes [5-7]. The wealth of functionality of this artificial structure is the result of its own chemical and physical properties, for example, two-dimensional fluidity, bio-compatibility, elasticity, and rich chemical composition. 

Figure 1. Multi-core microcapsules mimic biological cells and are sometimes called artificial cells. (Coletica )...

Artificial cells were prepared to contain biological cells... 

The biological cell Is the fundamental unit of all organs. It Is thus not too surprising that Its synthetic counterpart, the artificial cell. Is playing an Increasing role In artificial organs. The present paper only briefly describes a few examples to Illustrate the application of artificial cells In medicine, biotechnology and other areas. 

The main question is if - and to what extent - a reaction occurring inside a micrometric or submicrometric compailments differs from the same reaction in the bulk, and whether the formation of the compartment itself brings about novel effects. Clearly, these theoretical questions have great relevance in basic science, since the basic unit of life is itself a compartment (the biological cell), as well as in applications of compartmentalized systems for biotechnology (e.g. artificial cells, biosensors, etc.). ... 

Like biological cells, artificial cells contain biologically active materials. However, the content of artificial cells can be more varied than biological cells (Figure 41.1). The membranes of artificial cells also can be extensively varied using synthetic or biological materials. Permeability can be controlled over a wide range, and this allows the enclosed material to be retained and separated from... 

FIGURE 41.2 Basic principle of artificial cells Artificial cells are prepared to have some of the properties of biological cells. Like biological cells, artificial cells contain biologically active materials (I). The enclosed material (I) can be retained and separated from undesirable external materials, such as antibodies, leukocytes, and destructive substances. The large surface area and the ultra-thin membrane allow selected substrates (X) and products (Y) to permeate rapidly. Mass transfer across 100 mL of artificial cells can be 100 times higher than that for a standard hemodialysis machine. The synthetic membranes are usually made of ultrathin synthetic polymer membranes for this type of artificial cell. (From Chang, T.M.S., Artif. Cells Blood Substit. ImmobU. Biotechnol., 22(1), vii, 1994.)... 

Most enzymes in biological cells function as complex enzyme systems. We have prepared artilicial cells that contain multienzyme systems with cofactor recycling." This approach can convert metabolic wastes such as urea and ammonia into essential amino acids such as leucine, isoleucine, and valine, which are required by the body." We have also prepared artificial cells containing hanoglo-bin with pseudoperoxidase activity and glucose oxidase to ranove bilirubin." " ... 

A few years ago, Vincent Noireaux (now at the University of Minnesota) and Albert Libchaber (of Rockefeller University in New York) published an article with a telling title A vesicle bioreactor as a step toward an artificial cell assembly they reported data of a series of experiments in which they used a vesicle like the one in Figure 5.1 / and tried to equip it with at least the elements of bare necessity for a simplest biological cell. They succeeded in implanting some of the proteins into the artificial membrane, placing some DNA inside the cell, and making a few more steps towards artificial cell. 

One future prospect for microfluidic control will be the development of tailor-made vesicles with more complex geometries, triple, quadruple, multiple emulsions and artificial cells (artificiells), i.e. liposomes containing hposomes with each a different functionality, closely mimicking a biological cell structure, all designed for optimal performance for the specific function demanded from the vesicle. Double emulsions had already been made in a microfluidic device in a very controlled way [60, 61] (Figures 19.7 and 19.8). The number of secondary droplets inside the primary droplet... 

We are currently investigating the ability of the honeycomb-patterned film of polymer 22 and its derivatives as artificial extracellular matrices for biological cell culture [102]. 

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