Polyglycolide
Encyclopedia
Polyglycolide or Polyglycolic acid (PGA) is a biodegradable, thermoplastic
polymer
and the simplest linear, aliphatic polyester
. It can be prepared starting from glycolic acid
by means of polycondensation
or ring-opening polymerization
. PGA has been known since 1954 as a tough fiber
-forming polymer. Owing to its hydrolytic
instability, however, its use has initially been limited. Currently polyglycolide and its copolymers (poly(lactic-co-glycolic acid)
with lactic acid
, poly(glycolide-co-caprolactone) with ε-caprolactone
, and poly (glycolide-co-trimethylene carbonate) with trimethylene carbonate) are widely used as a material for the synthesis of absorbable sutures and are being evaluated in the biomedical
field.
is reported to be in the range of 225-230 °C. PGA also exhibits an elevated degree of crystallinity
, around 45-55%, thus resulting in insolubility in water. The solubility
of this polyester is somewhat unique, in that its high molecular weight form is insoluble in almost all common organic solvents (acetone
, dichloromethane
, chloroform
, ethyl acetate
, tetrahydrofuran
), while low molecular weight oligomer
s sufficiently differ in their physical properties to be more soluble. However, polyglycolide is soluble in highly fluorinated
solvents like hexafluoroisopropanol
(HFIP) and hexafluoroacetone sesquihydrate
, that can be used to prepare solutions of the high MW polymer for melt spinning
and film preparation. Fibers of PGA exhibit high strength and modulus
(7 GPa
) and are particularly stiff.
Polycondensation of glycolic acid is the simplest process available to prepare PGA, but it is not the most efficient because it yields a low molecular weight product. Briefly, the procedure is as follows: glycolic acid is heated at atmospheric pressure and a temperature of about 175-185°C is maintained until water ceases to distill
. Subsequently, pressure is reduced to 150 mm Hg, still keeping the temperature unaltered for about two hours and the low MW polyglycolide is obtained.
The most common synthesis used to produce a high molecular weight form of the polymer is ring-opening polymerization of "glycolide", the cyclic diester of glycolic acid. Glycolide can be prepared by heating under reduced pressure low MW PGA, collecting the diester by means of distillation. Ring-opening polymerization of glycolide can be catalyzed
using different catalysts, including antimony
compounds, such as antimony trioxide
or antimony trihalides, zinc
compounds (zinc lactate) and tin
compounds like stannous octoate (tin(II) 2-ethylhexanoate) or tin alkoxides. Stannous octoate is the most commonly used initiator, since it is approved by the FDA
as a food stabilizer. Usage of other catalysts has been disclosed as well, among these are aluminum isopropoxide, calcium
acetylacetonate, and several lanthanide
alkoxides (e.g. yttrium isopropoxide). The procedure followed for ring-opening polymerization is briefly outlined: a catalytic amount of initiator is added to glycolide under a nitrogen
atmosphere at a temperature of 195°C. The reaction is allowed to proceed for about two hours, then temperature is raised to 230°C for about half an hour. After solidification the resulting high MW polymer is collected.
Another procedure consists in the thermally induced solid-state polycondensation of halogenoacetates with general formula
X-—CH2COO-M+ (where M is a monovalent metal like sodium
and X is a halogen
like chlorine
), resulting in the production of polyglycolide and small crystal
s of a salt
. Polycondensation is carried out by heating an halogenoacetate, like sodium chloroacetate
, at a temperature between 160-180°C, continuously passing nitrogen through the reaction vessel. During the reaction polyglycolide is formed along with sodium chloride
which precipitates within the polymeric matrix; the salt can be conveniently removed by washing the product of the reaction with water.
PGA can also be obtained by reacting carbon monoxide, formaldehyde or one of its related compounds like paraformaldehyde
or trioxane
, in presence of an acidic catalyst. In a carbon monoxide atmosphere an autoclave
is loaded with the catalyst (chlorosulfonic acid), dichloromethane
and trioxane, then it is charged with carbon monoxide until a specific pressure is reached; the reaction is stirred and allowed to proceed at a temperature of about 180°C for two hours. Upon completion the unreacted carbon monoxide is discharged and a mixture of low and high MW polyglycolide is collected.
linkage in its backbone. The degradation process is erosive and appears to take place in two steps during which the polymer is converted back to its monomer glycolic acid: first water diffuses into the amorphous (non-crystalline) regions of the polymer matrix, cleaving the ester bonds; the second step starts after the amorphous regions have been eroded, leaving the crystalline portion of the polymer susceptible to hydrolytic attack. Upon collapse of the crystalline regions the polymer chain dissolves.
When exposed to physiological conditions, polyglycolide is degraded by random hydrolysis and apparently it is also broken down by certain enzyme
s, especially those with esterase
activity. The degradation product, glycolic acid, is non toxic and it can enter the tricarboxylic acid cycle after which it is excreted as water and carbon dioxide
. A part of the glycolic acid is also excreted by urine
.
Studies undergone using polyglycolide-made sutures have shown that the material loses half of its strength after two weeks and 100% after four weeks. The polymer is completely resorbed by the organism in a time frame of four to six months. Degradation is faster in vivo
than in vitro
, this phenomenon thought to be due to cellular enzymatic activity.
when compared with other synthetic polymers. However in 1962 this polymer was used to develop the first synthetic absorbable suture which was marketed under the tradename of Dexon by the Davis & Geck
subsidiary of the American Cyanamid Corporation. It is sold today as Surgicryl.
PGA suture is classified as a synthetic, absorbable, braided multifilament. It is coated with N-laurin and L-lysine
, which render the thread extremely smooth, soft and safe for knot
ting. It is also coated with magnesium
stearate
and finally sterilized with ethylene oxide
gas. It is naturally degraded in the body by hydrolysis
and is absorbed as water-soluble monomers, completed between 60 and 90 days. Elderly, anemic
and malnourished
patients may absorb the suture more quickly. Its color is either violet
or undyed and it is sold in sizes USP 6-0 (1 metric) to USP 2 (5 metric). It has the advantages of high initial tensile strength, smooth passage through tissue, easy handling, excellent knotting ability, and secure knot tying. It is commonly used for subcutaneous sutures, intracutaneous closures, abdominal and thoracic surgeries.
The traditional role of PGA as a biodegradable suture material has led to its evaluation in other biomedical fields. Implantable medical devices have been produced with PGA, including anastomosis
rings, pins, rods, plates and screws. It has also been explored for tissue engineering
or controlled drug delivery. Tissue engineering scaffolds made with polyglycolide have been produced following different approaches, but generally most of these are obtained through textile
technologies in the form of non-woven meshes
.
The Kureha Corporation has announced its commercialization of high molecular weight polyglycolide for food packaging applications under the tradename of Kuredux®. Production is at Belle, West Virginia, with an intended capacity of 4000 annual metric tons, according to a Chemicals Technology report. Its attributes as a barrier material result from its high degree of crystallization, the basis for a tortuous path mechanism for low permeability. It is anticipated that the high molecular weight version will have use as an interlayer between layers of polyethylene terephthalate
to provide improved barrier protection for perishable foods, including carbonated beverages and foods that lose freshness on prolonged exposure to air. Thinner plastic bottles which still retain desirable barrier properties may also be enabled by this polyglycolide interlayer technology. A low molecular weight version (approximately 600 amu) is available from the DuPont Co. and is purported to be useful in oil and gas applications.
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
and the simplest linear, aliphatic polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...
. It can be prepared starting from glycolic acid
Glycolic acid
Glycolic acid is the smallest α-hydroxy acid . This colorless, odorless, and hygroscopic crystalline solid is highly soluble in water. It is used in various skin-care products. Glycolic acid is found in some sugar-crops...
by means of polycondensation
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
or ring-opening polymerization
Ring-opening polymerization
In polymer chemistry, ring-opening polymerization is a form of chain-growth polymerization, in which the terminal end of a polymer acts as a reactive center, where further cyclic monomers join to form a larger polymer chain through ionic propagation...
. PGA has been known since 1954 as a tough fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....
-forming polymer. Owing to its hydrolytic
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
instability, however, its use has initially been limited. Currently polyglycolide and its copolymers (poly(lactic-co-glycolic acid)
PLGA
PLGA or poly is a copolymer which is used in a host of Food and Drug Administration approved therapeutic devices, owing to its biodegradability and biocompatibility. PLGA is synthesized by means of random ring-opening co-polymerization of two different monomers, the cyclic dimers of glycolic...
with lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
, poly(glycolide-co-caprolactone) with ε-caprolactone
Caprolactone
ε-Caprolactone or simply caprolactone is a cyclic ester, a member of the lactone family, with a seven-membered ring with the formula 5CO2. This colorless liquid is miscible with most organic solvents...
, and poly (glycolide-co-trimethylene carbonate) with trimethylene carbonate) are widely used as a material for the synthesis of absorbable sutures and are being evaluated in the biomedical
Biomedical engineering
Biomedical Engineering is the application of engineering principles and design concepts to medicine and biology. This field seeks to close the gap between engineering and medicine: It combines the design and problem solving skills of engineering with medical and biological sciences to improve...
field.
Physical properties
Polyglycolide has a glass transition temperature between 35-40 °C and its melting pointMelting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
is reported to be in the range of 225-230 °C. PGA also exhibits an elevated degree of crystallinity
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...
, around 45-55%, thus resulting in insolubility in water. The solubility
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
of this polyester is somewhat unique, in that its high molecular weight form is insoluble in almost all common organic solvents (acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
, dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
, chloroform
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
, ethyl acetate
Ethyl acetate
Ethyl acetate is the organic compound with the formula CH3COOCH2CH3. This colorless liquid has a characteristic sweet smell and is used in glues, nail polish removers, and cigarettes...
, tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
), while low molecular weight oligomer
Oligomer
In chemistry, an oligomer is a molecule that consists of a few monomer units , in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers, and tetramers are oligomers. Many oils are oligomeric, such as liquid paraffin...
s sufficiently differ in their physical properties to be more soluble. However, polyglycolide is soluble in highly fluorinated
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
solvents like hexafluoroisopropanol
Hexafluoro-2-propanol
Hexafluoroisopropanol, commonly abbreviated HFIP, is the organic compound with the formula 2CHOH. This fluorinated alcohol finds use as solvent and synthetic intermediate. It appears as a colorless, volatile liquid that is characterized by a strong, pungent odor...
(HFIP) and hexafluoroacetone sesquihydrate
Hexafluoroacetone
Hexafluoroacetone is a chemical compound with the formula CF3-CO-CF3. It is structurally similar to acetone, however its reactivity is markedly different. It comes in the form of a colourless, hygroscopic, nonflammable, highly reactive gas characterized by a musty odour...
, that can be used to prepare solutions of the high MW polymer for melt spinning
Melt spinning
Melt spinning is a technique used for rapid cooling of liquids. A wheel is cooled internally, usually by water or liquid nitrogen, and rotated. A thin stream of liquid is then dripped onto the wheel and cooled, causing rapid solidification. This technique is used to develop materials that require...
and film preparation. Fibers of PGA exhibit high strength and modulus
Young's modulus
Young's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...
(7 GPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
) and are particularly stiff.
Synthesis
Polyglycolide can be obtained through several different processes starting with different materials:- polycondensation of glycolic acid;
- ring-opening polymerization of glycolide;
- solid-stateSolid-state chemistrySolid-state chemistry, also sometimes referred to as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, particularly, but not necessarily exclusively of, non-molecular solids...
polycondensation of halogenoacetates
Polycondensation of glycolic acid is the simplest process available to prepare PGA, but it is not the most efficient because it yields a low molecular weight product. Briefly, the procedure is as follows: glycolic acid is heated at atmospheric pressure and a temperature of about 175-185°C is maintained until water ceases to distill
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....
. Subsequently, pressure is reduced to 150 mm Hg, still keeping the temperature unaltered for about two hours and the low MW polyglycolide is obtained.
The most common synthesis used to produce a high molecular weight form of the polymer is ring-opening polymerization of "glycolide", the cyclic diester of glycolic acid. Glycolide can be prepared by heating under reduced pressure low MW PGA, collecting the diester by means of distillation. Ring-opening polymerization of glycolide can be catalyzed
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
using different catalysts, including antimony
Antimony
Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
compounds, such as antimony trioxide
Antimony trioxide
Antimony trioxide is the inorganic compound with the formula Sb2O3. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite...
or antimony trihalides, zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
compounds (zinc lactate) and tin
Tin
Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
compounds like stannous octoate (tin(II) 2-ethylhexanoate) or tin alkoxides. Stannous octoate is the most commonly used initiator, since it is approved by the FDA
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...
as a food stabilizer. Usage of other catalysts has been disclosed as well, among these are aluminum isopropoxide, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
acetylacetonate, and several lanthanide
Lanthanide
The lanthanide or lanthanoid series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium...
alkoxides (e.g. yttrium isopropoxide). The procedure followed for ring-opening polymerization is briefly outlined: a catalytic amount of initiator is added to glycolide under a nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
atmosphere at a temperature of 195°C. The reaction is allowed to proceed for about two hours, then temperature is raised to 230°C for about half an hour. After solidification the resulting high MW polymer is collected.
Another procedure consists in the thermally induced solid-state polycondensation of halogenoacetates with general formula
X-—CH2COO-M+ (where M is a monovalent metal like sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
and X is a halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
like chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
), resulting in the production of polyglycolide and small crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s of a salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
. Polycondensation is carried out by heating an halogenoacetate, like sodium chloroacetate
Sodium chloroacetate
Sodium chloroacetate is the sodium salt of chloroacetic acid....
, at a temperature between 160-180°C, continuously passing nitrogen through the reaction vessel. During the reaction polyglycolide is formed along with sodium chloride
Sodium chloride
Sodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
which precipitates within the polymeric matrix; the salt can be conveniently removed by washing the product of the reaction with water.
PGA can also be obtained by reacting carbon monoxide, formaldehyde or one of its related compounds like paraformaldehyde
Paraformaldehyde
Paraformaldehyde is the smallest polyoxymethylene, it is the condensation reaction product of formaldehyde with a typical degree of polymerization of 8–100 units. Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition...
or trioxane
Trioxane
Trioxane refers to a pair of isomeric organic compounds having the molecular formula C3H6O3. Each contains a six membered ring with three carbon atoms and three oxygen atoms.The two isomers are...
, in presence of an acidic catalyst. In a carbon monoxide atmosphere an autoclave
Autoclave
An autoclave is an instrument used to sterilize equipment and supplies by subjecting them to high pressure saturated steam at 121 °C for around 15–20 minutes depending on the size of the load and the contents. It was invented by Charles Chamberland in 1879, although a precursor known as the...
is loaded with the catalyst (chlorosulfonic acid), dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
and trioxane, then it is charged with carbon monoxide until a specific pressure is reached; the reaction is stirred and allowed to proceed at a temperature of about 180°C for two hours. Upon completion the unreacted carbon monoxide is discharged and a mixture of low and high MW polyglycolide is collected.
Degradation
Polyglycolide is characterized by hydrolytic instability owing to the presence of the esterEster
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
linkage in its backbone. The degradation process is erosive and appears to take place in two steps during which the polymer is converted back to its monomer glycolic acid: first water diffuses into the amorphous (non-crystalline) regions of the polymer matrix, cleaving the ester bonds; the second step starts after the amorphous regions have been eroded, leaving the crystalline portion of the polymer susceptible to hydrolytic attack. Upon collapse of the crystalline regions the polymer chain dissolves.
When exposed to physiological conditions, polyglycolide is degraded by random hydrolysis and apparently it is also broken down by certain enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s, especially those with esterase
Esterase
An esterase is a hydrolase enzyme that splits esters into an acid and an alcohol in a chemical reaction with water called hydrolysis.A wide range of different esterases exist that differ in their substrate specificity, their protein structure, and their biological function.- EC classification/list...
activity. The degradation product, glycolic acid, is non toxic and it can enter the tricarboxylic acid cycle after which it is excreted as water and carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
. A part of the glycolic acid is also excreted by urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
.
Studies undergone using polyglycolide-made sutures have shown that the material loses half of its strength after two weeks and 100% after four weeks. The polymer is completely resorbed by the organism in a time frame of four to six months. Degradation is faster in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
than in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
, this phenomenon thought to be due to cellular enzymatic activity.
Uses
While known since 1954, PGA had found little use because of its sensitivity to hydrogenolysisHydrogenolysis
Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes "lysis" by hydrogen. The heteroatom may vary, but it usually is oxygen, nitrogen, or sulfur. A related reaction is hydrogenation, where hydrogen is added to the molecule, without...
when compared with other synthetic polymers. However in 1962 this polymer was used to develop the first synthetic absorbable suture which was marketed under the tradename of Dexon by the Davis & Geck
Davis & Geck
Davis & Geck was a surgical/medical device company founded in 1909 by Charles T. Davis and Fred A. Geck originally located in Brooklyn, NY.It specialized in the development and manufacture of surgical sutures along with various other products in the wound closure, surgical technique, and aseptic...
subsidiary of the American Cyanamid Corporation. It is sold today as Surgicryl.
PGA suture is classified as a synthetic, absorbable, braided multifilament. It is coated with N-laurin and L-lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
, which render the thread extremely smooth, soft and safe for knot
Knot
A knot is a method of fastening or securing linear material such as rope by tying or interweaving. It may consist of a length of one or several segments of rope, string, webbing, twine, strap, or even chain interwoven such that the line can bind to itself or to some other object—the "load"...
ting. It is also coated with magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
stearate
Stearate
Stearateis the anion form of stearic acid.Formula is C17H35COO−.-Examples:* Sodium stearate, Na* Calcium stearate, Ca2* Magnesium stearate, Mg2...
and finally sterilized with ethylene oxide
Ethylene oxide
Ethylene oxide, also called oxirane, is the organic compound with the formula . It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape . This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered...
gas. It is naturally degraded in the body by hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
and is absorbed as water-soluble monomers, completed between 60 and 90 days. Elderly, anemic
Anemia
Anemia is a decrease in number of red blood cells or less than the normal quantity of hemoglobin in the blood. However, it can include decreased oxygen-binding ability of each hemoglobin molecule due to deformity or lack in numerical development as in some other types of hemoglobin...
and malnourished
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
patients may absorb the suture more quickly. Its color is either violet
Violet (color)
As the name of a color, violet is synonymous with a bluish purple, when the word "purple" is used in the common English language sense of any color between blue and red, not including either blue or red...
or undyed and it is sold in sizes USP 6-0 (1 metric) to USP 2 (5 metric). It has the advantages of high initial tensile strength, smooth passage through tissue, easy handling, excellent knotting ability, and secure knot tying. It is commonly used for subcutaneous sutures, intracutaneous closures, abdominal and thoracic surgeries.
The traditional role of PGA as a biodegradable suture material has led to its evaluation in other biomedical fields. Implantable medical devices have been produced with PGA, including anastomosis
Anastomosis
An anastomosis is the reconnection of two streams that previously branched out, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....
rings, pins, rods, plates and screws. It has also been explored for tissue engineering
Tissue engineering
Tissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...
or controlled drug delivery. Tissue engineering scaffolds made with polyglycolide have been produced following different approaches, but generally most of these are obtained through textile
Textile
A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...
technologies in the form of non-woven meshes
Nonwovens
Nonwoven fabric is a fabric-like material made from long fibres, bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing industry to denote fabrics, such as felt, which are neither woven nor knitted. Nonwoven materials typically lack...
.
The Kureha Corporation has announced its commercialization of high molecular weight polyglycolide for food packaging applications under the tradename of Kuredux®. Production is at Belle, West Virginia, with an intended capacity of 4000 annual metric tons, according to a Chemicals Technology report. Its attributes as a barrier material result from its high degree of crystallization, the basis for a tortuous path mechanism for low permeability. It is anticipated that the high molecular weight version will have use as an interlayer between layers of polyethylene terephthalate
Polyethylene terephthalate
Polyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
to provide improved barrier protection for perishable foods, including carbonated beverages and foods that lose freshness on prolonged exposure to air. Thinner plastic bottles which still retain desirable barrier properties may also be enabled by this polyglycolide interlayer technology. A low molecular weight version (approximately 600 amu) is available from the DuPont Co. and is purported to be useful in oil and gas applications.