Artificial cell

An artificial cell or minimal cell is an engineered particle that mimics one or many functions of a biological cell. The term does not refer to a specific physical entity, but rather to the idea that certain functions or structures of biological cells can be replaced or supplemented with a synthetic entity. Often, artificial cells are biological or polymeric membranes which enclose biologically active materials. As such, nanoparticles, liposomes, polymersomes, microcapsules and a number of other particles have qualified as artificial cells. Micro-encapsulation allows for metabolism within the membrane, exchange of small molecules and prevention of passage of large substances across it. The main advantages of encapsulation include improved mimicry in the body, increased solubility of the cargo and decreased immune responses. Notably, artificial cells have been clinically successful in hemoperfusion. An artificial cell or minimal cell is an engineered particle that mimics one or many functions of a biological cell. The term does not refer to a specific physical entity, but rather to the idea that certain functions or structures of biological cells can be replaced or supplemented with a synthetic entity. Often, artificial cells are biological or polymeric membranes which enclose biologically active materials. As such, nanoparticles, liposomes, polymersomes, microcapsules and a number of other particles have qualified as artificial cells. Micro-encapsulation allows for metabolism within the membrane, exchange of small molecules and prevention of passage of large substances across it. The main advantages of encapsulation include improved mimicry in the body, increased solubility of the cargo and decreased immune responses. Notably, artificial cells have been clinically successful in hemoperfusion. In the area of synthetic biology, a 'living' artificial cell has been defined as a completely synthetically made cell that can capture energy, maintain ion gradients, contain macromolecules as well as store information and have the ability to mutate. Such a cell is not technically feasible yet, but a variation of an artificial cell has been created in which a completely synthetic genome was introduced to genomically emptied host cells. Although not completely artificial because the cytoplasmic components as well as the membrane from the host cell are kept, the engineered cell is under control of a synthetic genome and is able to replicate. The first artificial cells were developed by Thomas Chang at McGill University in the 1960s. These cells consisted of ultrathin membranes of nylon, collodion or crosslinked protein whose semipermeable properties allowed diffusion of small molecules in and out of the cell. These cells were micron-sized and contained cell, enzymes, hemoglobin, magnetic materials, adsorbents and proteins. Later artificial cells have ranged from hundred-micrometer to nanometer dimensions and can carry microorganisms, vaccines, genes, drugs, hormones and peptides. The first clinical use of artificial cells was in hemoperfusion by the encapsulation of activated charcoal. In the 1970s, researchers were able to introduce enzymes, proteins and hormones to biodegradable microcapsules, later leading to clinical use in diseases such as Lesch-Nyhan syndrome. Although Chang's initial research focused on artificial red blood cells, only in the mid-1990s were biodegradable artificial red blood cells developed. Artificial cells in biological cell encapsulation were first used in the clinic in 1994 for treatment in a diabetic patient and since then other types of cells such as hepatocytes, adult stem cells and genetically engineered cells have been encapsulated and are under study for use in tissue regeneration. On December 29, 2011, chemists at Harvard University reported the creation of an artificial cell membrane. By 2014, self-replicating, synthetic bacterial cells with cell walls and synthetic DNA had been produced. In January of that year researchers produced an artificial eukaryotic cell capable of undertaking multiple chemical reactions through working organelles. In September 2018, researchers at the University of California developed artificial cells that can kill bacteria. The cells were engineered from the bottom-up — like Lego blocks — to destroy bacteria. Membranes for artificial cells be made of simple polymers, crosslinked proteins, lipid membranes or polymer-lipid complexes. Further, membranes can be engineered to present surface proteins such as albumin, antigens, Na/K-ATPase carriers, or pores such as ion channels.Commonly used materials for the production of membranes include hydrogel polymers such as alginate, cellulose and thermoplastic polymers such as hydroxyethyl methacrylate-methyl methacrylate (HEMA- MMA), polyacrylonitrile-polyvinyl chloride (PAN-PVC), as well as variations of the above-mentioned. The material used determines the permeability of the cell membrane, which for polymer depends on the molecular weight cut off (MWCO). The MWCO is the maximum molecular weight of a molecule that may freely pass through the pores and is important in determining adequate diffusion of nutrients, waste and other critical molecules.Hydrophilic polymers have the potential to be biocompatible and can be fabricated into a variety of forms which include polymer micelles, sol-gel mixtures, physical blends and crosslinked particles and nanoparticles. Of special interest are stimuli-responsive polymers that respond to pH or temperature changes for the use in targeted delivery. These polymers may be administered in the liquid form through a macroscopic injection and solidify or gel in situ because of the difference in pH or temperature. Nanoparticle and liposome preparations are also routinely used for material encapsulation and delivery. A major advantage of liposomes is their ability to fuse to cell and organelle membranes.