Biopolymers in Body
Biopolymers are natural polymers or polymeric biomolecules produced by the cells of the living body. They are monomeric units that are covalently bonded to form larger molecules. Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, and carbohydrates are the most common biopolymer materials produced in the cells of the living body. The name biopolymer originates from the Greek words bio meaning nature and polymer meaning living body.
Biopolymers are the organic substances found in natural sources such as plants, animals, microorganisms, and agricultural wastes. Therefore, most biopolymers are safe to use because they are non-toxic, biodegradable, and excellent film-forming materials.
Synthetic Polymers and Biopolymers
- A major difference between synthetic polymers and biopolymers can be found in their structures. Synthetic polymers can have either simple or complex structures while most biopolymers found in our body can form complex structures.
- Biopolymers are the natural materials found inside our body formed by biological reactions while synthetic polymers are man-made materials that can be synthesized artificially by polymerization reactions.
- Most synthetic polymers are non-degradable in nature whereas biopolymers are degradable in nature.
- Biopolymers can be melted and shaped in the same way as synthetic polymers.
Biopolymers Types
Biopolymers are types of polymers that can be synthesized chemically from biological materials or biosynthesized by the living body. Plants, animals, microorganisms, and agricultural wastes are common natural biological sources of biopolymer materials.
Polynucleotides, polypeptides, and polysaccharides are the three main types of biopolymers found in the living body. Other examples of biopolymer molecules may include natural rubbers, polyphenolic polymers (suberin and lignin), and polymers of long-chain fatty acids (cutin and cutan).
The sequences, size, hydrophilicity, and hydrophobicity of biopolymer can be determined by various analytical methods. Biopolymer chromatography is a branch of liquid chromatography that is used for rapid and high-resolution chromatographic separations of these biomolecules.
Polynucleotides
They are the long-chain polymers of nucleotides found in the nucleic acids of living organisms. Polynucleotides consist of 13 or more nucleotide monomers joined to form a chain-like structure.
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are examples of polynucleotides that carry genetic information from one body to another. DNA contains two long chains of polynucleotides that have four nucleotide subunits.
The nucleic acid sequence can be determined using gel permeation chromatography, size exclusion chromatography, electrophoresis, ion exchange chromatography, etc.
Polypeptides
A polypeptide is a continuous, unbranched biopolymer of amino acids joined together by peptide bonds. A peptide bond in a polypeptide is formed when the carboxyl group of one amino acid joins the amino group of another amino acid with the removal of one water molecule. Mass spectrometry techniques can also be used for the identification and separation of proteins.
Polypeptides differ from peptides in the number of amino acid molecules. Peptides are made up of shorter chains (less than 10 amino acids) of amino acids but polypeptides are made up of longer chains of amino acids. Therefore, polypeptides are biomolecules of amino acids that are the fundamental unit of proteins (collagen, actin, fibrin, etc).
Polysaccharides
Polysaccharides are linear or branched chains of sugar carbohydrates such as starch, cellulose, chitin, insulin, glycogen, hyaluronic acid, etc. They are the polymers of monosaccharide units with high molecular weight.
Polysaccharides contain repeated units of monosaccharides or their derivatives held together by glycosidic bonding. These are linear or branched biopolymers found in living bodies.
Examples of Biopolymers
Proteins, carbohydrates, and nucleic acids (DNA and RNA) are examples of biopolymers found in the living body. The most common proteins, carbohydrates, and nucleic acids-based biopolymers are:
- Starch
- Glycogen
- Gelatin
- Cellulose
- Collagen
- Fibrin
- Hyaluronic acid
- Alginate
Starch
Starch is a carbohydrate-based biopolymer found in plants. It is the most important dietary source for higher animals, including man. Starch consists of two polysaccharide components: water-soluble amylose (15−20%) and amylopectin (80−85%).
Chemically, amylose is a long unbranched chain biopolymer with 200−1000 D−glucose units held by α (1→4) glycosidic linkage.
On the other hand, in amylopectin, a long-branched chain biopolymer of D−glucose units held by α (1→6) glycosidic bonds at the branching points and α (1→4) linkages everywhere else. It contains a few thousand glucose units that look like a branched tree where 20−30 glucose units per branched.
Uses of Starch
Starch is one of the most useful and promising biodegradable polymers used in food packaging due to its many advantageous properties, such as biodegradability, low cost, abundance, transparency, colorlessness, flavorlessness, and tastelessness. It also reduces water sensitivity and has excellent oxygen barrier properties, renewability, and edibility.
Starch is an excellent film-forming biopolymer. However, starch alone is not a suitable food packaging material due to a lack of basic important properties such as a vapour barrier, mechanical, and thermal properties. We use two main techniques the dry process and the wet process for the development of starch biofilms.
Glycogen
Glycogen is a carbohydrate-based biopolymer found mostly in the liver, muscle, brain, etc. It is also found in plants (yeast and fungi) that do not contain chlorophyll. It is the storage form of glucose and is mostly found in the liver and muscles of animals.
The structure of glycogen is similar to that of amylopectin with more branches. The glucose unit in glycogen joins together by α (1→4) glycosidic bonds and α (1→6) glycosidic bonds at branching points.
The prime function of liver glycogen is to maintain blood glucose levels during meals. Muscle glycogen supplies ATP during muscle contraction. It generates energy in the absence of oxygen.
Gelatin
Gelatin is an animal-based protein biopolymer obtained by boiling the skin, tendons, ligaments, and bones of domesticated cattle, chickens, pigs, and fish in water. Type A and Type B are the two types of gelatin obtained from collagen by two different processes. Type A is obtained from collagen by acid hydrolysis while Type B is obtained from alkaline hydrolysis.
Gelatin is beneficial for health because this biopolymer is rich in protein with amino acids. It may reduce joint and bone pain, increase brain function, and help to reduce skin aging signs.
Uses of Gelatin
Gelatin is used in the food, medicine, and photographic industries because it is a non-toxic, renewable, biodegradable, and excellent film-forming material.
Gelatin is used mostly as a raw material for making biodegradable films and edible films. However, alone gelatin biopolymer is unsuitable for food packaging material due to its poor mechanical properties.
Cellulose
Cellulose is the most abundant organic substance or biopolymer found exclusively in plants. It is a predominant constituent of plant cells but is totally absent in animal bodies. It contains β−D−glucose units linked by β (1→4) glycosidic bonding.
Cellulose cannot be digested by mammals including humans, but it has great importance in human nutrition. It is a constituent of fiber, a non-digestible carbohydrate. The functions of dietary fiber can decrease the absorption of glucose and cholesterol from the intestine and increase the bulk of feces.
Uses of Cellulose
Cellulose is the most abundant natural organic biopolymer that is widely found in plants and bacteria. It is a raw material for biodegradable films and edible films because cellulose is a renewable, low-cost, nontoxic, biocompatible, biodegradable, odorless, tasteless, and chemically stable biopolymer.
The most common cellulose derivatives used in food packaging include methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), and carboxymethyl cellulose (CMC).
Collagen
Collagen is the most abundant protein biopolymer found in mammals. Such biopolymer molecule contains approximately one-third of the total body protein. It is the major component of connective tissue and gives strength, support, and shape to the tissues.
Collagen is not a single homogeneous protein but a group of structurally related protein molecules. In humans, different types of collagens are composed of distinct polypeptide chains. The synthesis of collagen occurs mainly in fibroblasts and related cells such as osteoblasts in bones, chondroblasts in cartilage, and odontoblasts in teeth.
Uses of Collagen
Collagen is industrially prepared from the skin and bones of swine, cattle, and fish skin. It has a great film-forming ability, antioxidant properties, moisture and oxygen barrier ability, and structural integrity.
However, due to high water vapour transmission rates and poor mechanical properties, collagen material has limited applications in the food packaging industry.
Fibrin
Fibrin is a fibrous biopolymer and non-globular protein involved mainly in blood clotting. It is formed from fibrinogen, a soluble glycoprotein that constitutes two to three percent of plasma proteins.
Fibrinogen undergoes proteolytic cleavage catalyzed by thrombin to release small fibrinopeptides. Therefore, in the formation of fibrin monomers, they can stick together to form hard clots. Clot formation is further stabilized by covalent cross-linking between glutamine and lysine residues.
Actin
Actin is a major constituent of the thin filaments of the sarcomere. It exists in two forms − monomeric G−actin and polymeric F−actin. G−actin constitutes 25 percent of the muscle proteins by weight. In the presence of magnesium ions (Mg+2), G−actin polymerizes to form an insoluble double helical biopolymer of F−actin.
Hyaluronic Acid
Hyaluronic acid is an important biopolymer found in the ground substance of synovial fluids of joints and vitreous humor of the eyes. It is also present in a ground substance in connective tissues and forms a gel around the ovum. Hyaluronic acid serves as a lubricant and synovial fluid, and facilitates smooth joint movements.
Hyaluronic acid is composed of alternate units of D-glucuronic acid and N-acetyl D-glucosamine. These two molecules form disaccharide units held together by a β (1→3) glycosidic bond. Hyaluronic acid contains about 250 − 25000 disaccharide units with a molecular weight of up to 4 million.
The enzyme hyaluronidase is present at high concentrations in testes, seminal fluid, and in certain snake and insect venoms. Hyaluronidase present in semen plays an important role in fertilization. It clears the gel around the ovum allowing better penetration of sperm into the ovum.
Uses of Hyaluronic Acid
Hyaluronic acid is a remarkable biomolecule because it has some common benefits and uses in our bodies. It is a proven substance that helps wounds heal faster and can reduce scarring.
Hyaluronic acid is used for making moisturizing creams, lotions, ointments, and serums. Such beauty products make your skin flexible and stretch-free. It also reduces your skin’s wrinkles and lines.
Alginate
Alginate is a natural polysaccharide or biopolymer extracted from brown algae or brown seaweed. It is a biopolymer that has a wide range of applications in the packaging, textile, and food industries.
Uses of Alginate
Such a type of polymer is used in biomedical and chemical engineering due to its biocompatibility, low toxicity, relatively low cost, and mild gelation properties.
Commercially, alginate-based biopolymer is used as a thickener, stabilizer, and gelling agent in foods such as deserts, sauces, and beverages.
Uses of Biopolymers
Biopolymers are a class of polymers produced from the monomers of the living body. They can control various biological activities in the living body. Starch, proteins and peptides, DNA, and RNA are the most common examples of biopolymers, in which the monomer units are sugars, amino acids, and nucleotides.
In addition to their biological activities, biopolymers have enormous uses in the fields of the food industry, manufacturing, packaging, and biomedical engineering or medicine.
Biopolymers Uses in Food
Biopolymers are commonly used in the food industry for packaging materials, making edible encapsulation films, and coating foods.
Packaging of Materials
Starch, cellulose, and polylactic acid (PLA) are the most common biopolymer materials that are used widely for packaging food items. Biopolymers are biodegradable materials obtained from renewable sources and do not cause any environmental pollution.
However, the main disadvantages of biopolymer materials in food packaging are their weak mechanical strength and high sensitivity to moisture.
Edible Films and Coating
Edible films and coatings are made from edible biopolymeric sources such as polysaccharides and proteins. They are used in the food industry because they encapsulate food products and provide antioxidants, enzymes, probiotics, minerals, and vitamins which are needed for a healthy life.
Cellulose products are a common raw material for biodegradable coating and edible films because they are renewable, low-cost, nontoxic, biocompatible, biodegradable, odorless, tasteless, and chemically stable biopolymer materials.
Biomedical Application of Biopolymers
Owing to their superior biodegradability and lack of cytotoxicity, biopolymers are good alternatives to commonly utilized synthetic materials. Collagen, gelatin, dextran, agarose/alginate, hyaluronic acid, cellulose, and fibrin gels are the most common examples of biopolymers that are used extensively in the biomedical industry.
Such types of natural polymers are commonly used in tissue engineering, medical devices, and the pharmaceutical industry.
Biopolymers Uses in Medicine
In medicine and drug delivery systems, biopolymers are used for suturing, fixing, adhesion, covering, occlusion, isolation, contact inhibition, cell proliferation, tissue guiding, and controlled drug administration.
Tissue engineering
Natural biopolymers are very useful materials in tissue engineering due to their natural abundance, sustainability, and biocompatibility/biodegradability. Such types of biopolymer materials are commonly used for wound dressing and implant materials.
Biopolymers (silk, gelatin, alginate, chitosan, etc) are chosen in tissue engineering due to their special durability, stretchability, and swellability.
Biopolymers in Medical Devices
Medical manufacturers have used biopolymers for making medical devices because they are preferred materials due to their biocompatibility, functionality, and biodegradability.
Some common examples of such devices may include soft-tissue replacement vascular grafts, intraocular lenses, artificial hearts, contact lenses, plasmapheresis units, dialyzers, cardiac assist devices, implantable pumps, pacemakers, encapsulations, heart valves, artificial blood vessels, etc.
Uses of Biopolymer Materials
Many biopolymers such as polyglyconic acid (PLA), naturally occurring zein, and poly-3-hydroxybutyrate are used for making bioplastics to replace polystyrene or polyethylene-based plastics. These biopolymers come from the biomass of crops such as sugar beet, potatoes, or wheat.
Biopolymers are renewable resources because they are obtained from biomass and used widely in packaging materials in industry. Unlike plastics, biopolymer materials are biocompatible and biodegradable within a short period of time. Therefore, biopolymer materials are used because they are environmentally friendly and biodegradable.
Biopolymers Removal
Biopolymer removal is a surgical procedure that is used to remove hazardous substances from your body. Removing silicone from the buttocks by the buttock lift procedure is the most common type of biopolymer removal procedure.
Uses of Bioplastics
Bioplastics are biodegradable biopolymer materials that come from renewable sources. Almost all biopolymers are biodegradable in the natural environment because they are broken down into carbon dioxide (CO2) and water by microorganisms
Bioplastics are an alternative to reduce the problem of plastic waste and save the planet from environmental pollutants. Therefore, bioplastics are extensively used biopolymer materials for manufacturing bottles, cups, pots, bowls, flexible films, and other useful packaging products.
