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Nerve Guidance Conduit
A nerve guidance conduit (also referred to as an artificial nerve conduit or artificial nerve graft, as opposed to an autograft) is an artificial means of guiding axonal regrowth to facilitate nerve regeneration and is one of several clinical treatments for nerve injuries. When direct suturing of the two stumps of a severed nerve cannot be accomplished without tension, the standard clinical treatment for peripheral nerve injuries is autologous nerve grafting. Due to the limited availability of donor tissue and functional recovery in autologous nerve grafting, neural tissue engineering research has focused on the development of bioartificial nerve guidance conduits as an alternative treatment, especially for large defects. Similar techniques are also being explored for nerve repair in the spinal cord but nerve regeneration in the central nervous system poses a greater challenge because its axons do not regenerate appreciably in their native environment. The creation of artificia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autograft
Autotransplantation is the transplantation of organs, tissues, or even particular proteins from one part of the body to another in the same person ('' auto-'' meaning "self" in Greek). The autologous tissue (also called autogenous, autogeneic, or autogenic tissue) transplanted by such a procedure is called an autograft or autotransplant. It is contrasted with allotransplantation (from other individual of the same species), syngeneic transplantation (grafts transplanted between two genetically identical individuals of the same species) and xenotransplantation (from other species). A common example is the removal of a piece of bone (usually from the hip) and its being ground into a paste for the reconstruction of another portion of bone. Autotransplantation, although most common with blood, bone, or skin, can be used for a wide variety of organs. One of the rare examples is autotransplantation of a kidney from one side of the body to the other. Kidney autotransplantation is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogels
A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still diffuse through this system. A gel has been defined phenomenologically as a soft, solid or solid-like material consisting of two or more components, one of which is a liquid, present in substantial quantity. By weight, gels are mostly liquid, yet they behave like solids because of a three-dimensional cross-linked network within the liquid. It is the crosslinking within the fluid that gives a gel its structure (hardness) and contributes to the adhesive stick (tack). In this way, gels are a dispersion of molecules of a liquid within a solid medium. The word ''gel'' was coined by 19th-century Scottish chemist Thomas Graham by clipping from ''gelatine''. The process of forming a gel is called gelation. IUPAC definition } Com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chitin
Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chitin are produced each year in the biosphere. It is a primary component of cell walls in fungi (especially basidiomycetes and filamentous fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and gladii of molluscs and in some nematodes and diatoms. It is also synthesised by at least some fish and lissamphibians. Commercially, chitin is extracted from the shells of crabs, shrimps, shellfishes and lobsters, which are major by-products of the seafood industry. The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin. Chitin has proved useful for several medicinal, industrial and biotechnological purpos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour. Acetone is miscible with water and serves as an important organic solvent in its own right, in industry, home, and laboratory. About 6.7 million tonnes were produced worldwide in 2010, mainly for use as a solvent and production of methyl methacrylate (and from that PMMA) as well as bisphenol A.Acetone World Petrochemicals report, January 2010Stylianos Sifniades, Alan B. Levy, "Acetone" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. It is a common building block in |
(Hydroxyethyl)methacrylate
Hydroxyethylmethacrylate (also known as glycol methyacrylate) is the organic compound with the chemical formula . It is a colorless viscous liquid that readily polymerizes. Hydroxyethylmethacrylate is a monomer that is used to make various polymers. Synthesis Hydroxyethylmethacrylate was first synthesized around 1925. Common methods of synthesis are: * reaction of methacrylic acid with ethylene oxide; * esterification of methacrylic acid with a large excess of ethylene glycol. Both these methods give also some amount of ethylene dimethacrylate. During polymerization of hydroxyethylmethacrylate, it works as crosslinking agent. Properties Hydroxyethylmethacrylate is completely miscible with water and ethanol, but its polymer is practically insoluble in common solvents. Its viscosity is 0.0701 Pa⋅s at 20°C and 0.005 Pa⋅s at 30°C. During polymerization, it shrinks by approximately 6%. Applications Contact lenses In 1960, O. Wichterle and D. Lím described its use in synthes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polycaprolactone
Polycaprolactone (PCL) is a biodegradable polyester with a low melting point of around 60 °C and a glass transition temperature of about −60 °C. The most common use of polycaprolactone is in the production of speciality polyurethanes. Polycaprolactones impart good resistance to water, oil, solvent and chlorine to the polyurethane produced. This polymer is often used as an additive for resins to improve their processing characteristics and their end use properties (e.g., impact resistance). Being compatible with a range of other materials, PCL can be mixed with starch to lower its cost and increase biodegradability or it can be added as a polymeric plasticizer to polyvinyl chloride (PVC). Polycaprolactone is also used for splinting, modeling, and as a feedstock for prototyping systems such as fused filament fabrication 3D printers. Synthesis PCL is prepared by ring opening polymerization of ε-caprolactone using a catalyst such as stannous octoate. A wide r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Nitrogen
Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is widely used as a coolant. Physical properties The diatomic character of the N2 molecule is retained after liquefaction. The weak van der Waals interaction between the N2 molecules results in little interatomic interaction, manifested in its very low boiling point. The temperature of liquid nitrogen can readily be reduced to its freezing point by placing it in a vacuum chamber pumped by a vacuum pump. Liquid nitrogen's efficiency as a coolant is limited by the fact that it boils immediately on contact with a warmer object, enveloping the object in an insulating layer of nitrogen gas bubbles. This effect, known as the Leidenfrost effect, occurs when any liquid comes in contact with a surface which is significantly hotter than its boiling ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetic Acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component of vinegar apart from water and other trace elements. Acetic acid is the second simplest carboxylic acid (after formic acid). It is an important Reagent, chemical reagent and industrial chemical, used primarily in the production of cellulose acetate for photographic film, polyvinyl acetate for wood Adhesive, glue, and synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is controlled by the E number, food additive code E260 as an acidity regulator and as a condiment. In biochemistry, the acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. The global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lyophilization
Freeze drying, also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product and lowering pressure, removing the ice by sublimation. This is in contrast to dehydration by most conventional methods that evaporate water using heat. Because of the low temperature used in processing, the rehydrated product retains much of its original qualities. When solid objects like strawberries are freeze dried the original shape of the product is maintained. If the product to be dried is a liquid, as often seen in pharmaceutical applications, the properties of the final product are optimized by the combination of excipients (i.e., inactive ingredients). Primary applications of freeze drying include biological (e.g., bacteria and yeasts), biomedical (e.g., surgical transplants), food processing (e.g., coffee) and preservation. History The Inca were freeze drying potatoes into chuño from the 13th century. The process involved mult ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microtubule
Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nm and have an inner diameter between 11 and 15 nm. They are formed by the polymerization of a dimer of two globular proteins, alpha and beta tubulin into protofilaments that can then associate laterally to form a hollow tube, the microtubule. The most common form of a microtubule consists of 13 protofilaments in the tubular arrangement. Microtubules play an important role in a number of cellular processes. They are involved in maintaining the structure of the cell and, together with microfilaments and intermediate filaments, they form the cytoskeleton. They also make up the internal structure of cilia and flagella. They provide platforms for intracellular transport and are involved in a variety of cellular processes, including the movement of secretory vesicles, organell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurite
A neurite or neuronal process refers to any projection from the cell body of a neuron. This projection can be either an axon or a dendrite. The term is frequently used when speaking of immature or developing neurons, especially of cells in culture, because it can be difficult to tell axons from dendrites before differentiation is complete. Neurite development The development of a neurite requires a complex interplay of both extracellular and intracellular signals. At every given point along a developing neurite, there are receptors detecting both positive and negative growth cues from every direction in the surrounding space. The developing neurite sums together all of these growth signals in order to determine which direction the neurite will ultimately grow towards. While not all of the growth signals are known, several have been identified and characterized. Among the known extracellular growth signals are netrin, a midline chemoattractant, and semaphorin, ephrin and collaps ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poly-lysine
Polylysine refers to several types of lysine homopolymers, which may differ from each other in terms of stereochemistry (D/L; the L form is natural and usually assumed) and link position (α/ε). Of these types, only ε-poly-L-lysine is produced naturally. Chemical structure The precursor amino acid lysine contains two amino groups, one at the α-carbon and one at the ε-carbon. Either can be the location of polymerization, resulting in α-polylysine or ε-polylysine. Polylysine is a homopolypeptide belonging to the group of cationic polymers: at pH 7, polylysine contains a positively charged hydrophilic amino group. α-Polylysine is a synthetic polymer, which can be composed of either L-lysine or D-lysine. "L" and "D" refer to the chirality at lysine's central carbon. This results in poly-L-lysine (PLL) and poly-D-lysine (PDL) respectively. ε-Polylysine (ε-poly-L-lysine, EPL) is typically produced as a homopolypeptide of approximately 25–30 L-lysine residues. According ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
