What are Biodegradable Polymers? Before answering this question, let us see what are polymers, first. The polymers are the substances with large molecules or a chain of molecules. They can be further divided into natural polymers and synthetic polymers. You may not believe that all the plants and the animals are made out of polymers. Proteins, DNA and cellulose (a kind of protein in plants) are some of the polymers we can find in living beings. Synthetic polymers are the most widely used type of polymers. Polythene, PVC and synthetic rubber are the examples of synthetic polymers. The firsthand issue in using synthetic polymers is that they are utilized for short term usages, but they last for a long period as synthetic polymers are by products of petrochemicals. This situation leads to many environmental problems such as soil erosion, water pollution, and toxic-gas emission.
Biodegradable Polymers – Definition
Every polymer is degradable. They degrade in mass, strength and molecular weight with time. Most of the polymers that we already knew, have a period of 100-1000 years to degrade in fully. The specialties in biodegradable polymers are, they degrade quickly when comparing to non- biodegradable polymers and their byproducts are eco-friendly (biocompatible) such as CO2, water, methane, and inorganic compounds or biomass that is easily scavenged by microorganisms.
Biodegradable Polymers – Types
Biodegradable polymers can be categorized under two main topics according to their formation method.
- Agro polymers
polymers obtained by microbial productions
conventional synthesis from bio-derived monomers
Biomass products can be again divided into two subcategories as Polysaccharides and Proteins. The agro polymers are obtained from agro-materials such as polysaccharides. Polysaccharides (complex carbohydrates) are the most abundant macromolecules in the biosphere. Starch is the most well-known type of polysaccharides, which are extracted from cereals and tubers. Chitin, Chitosan, and Pectin are some other types of polysaccharides.
The second type of agro polymers are proteins that are made out of amino acids. The most significant feature in proteins is that they are renewable. The proteins are widely used in the food industry. Soy protein, corn protein and wheat protein are among the plant proteins and Casein, Collagen, gelatin and keratin are the types of extensively used animal proteins. Lactate dehydrogenase, chymotrypsin, and fumarase are the main bacterial proteins. Even though these types of polymers are mainly used in the food industry, still the packaging industry did not find a way to replace conventional plastics with agro polymers.
Bio-polyesters are the second type of the biodegradable polymers. They can be produced either through living resources as well as non-living resources (synthetics).
Examples of Biodegradable Polymers
Lactic acid is a well-known, widely used biopolymer in many industries. It exists in two forms as L- lactic acid and d-lactic acid. They can be produced by two different ways, either biologically or chemically. In the biological method, the carbohydrates fermentation is done by Lactobacillus ( bacteria) or fungi. Lactic acid can also be produced through chemical chain reactions. We can also experience this reaction in our body when having tired muscles. Industrially lactic acid is mainly used to produce cosmetics.
Polyhdroxyalkanoates (PHA) are a family of intracellular biopolymers synthesized by many bacteria as intracellular carbon and energy storage granules. PHAs are utilized in the industry of packaging and medical due to their biodegradability.
Most of the biodegradable polymers are sub-products of petroleum resources. Polycaprolactone, aliphatic co-polyesters, and aromatic co-polyesters are such types of petroleum-based polyesters. All these polyesters are soft materials at room temperature.
Biodegradable Polymers in Biomedical Applications
Biodegradable polymers opened a way to integrate with many medical issues as a biocompatible material. Using biodegradable polymers in the medical field is their less harmfulness when compared with other materials. Unlike in general applications of biodegradable polymers, there are many facts to be concerned when using the bio-degradable as bio-materials. These facts are non-toxicity, sterilizability, effectiveness and bio-compatibility. It is a difficult thing to find out all the facts in most of the biodegradable polymers, but scientists, clinicians and engineers have found certain biodegradable polymers to be used as bio-materials.
Biomaterials directly contact living cells. There are two typical uses in biomaterials. The first one is biomaterials as disposal products such as blood bags, catheters and syringes. The second usage is as materials supporting surgical operations. It can be either for prosthesis for tissue replacement such as lens, dental and breast replacements or as artificial organs such as artificial hearts and artificial kidneys.
There are many surgical uses in biodegradable polymers. The bio-absorbable quality in biodegradable polymers is used for bonding, closure, separation, scaffold and capsulation. The biodegradable polymers are consumed for surgeries for sealing and adhesion to tissues. Liquid type polymers are used in this case. Immediately after applying the liquid to the defective tissue, the liquid will become gel and stop bleeding. When the defective tissue heals, the gelled material will slowly degrade and absorb into the body. The same steps happen in bone fixation using biodegradable pins, screws and wires.
Drug delivery systems use biodegradable polymers for their task. Both invasive and non-invasive methods of drug delivering can be taken into this. In this case these polymers just act as a transporter and after delivering the drug to the desired part they will quickly absorb into the body without a harmful effect. The simplest case you may have seen is the pill covers and the coatings in different colors. The drug is included inside the cover and that cover should be excreted without affecting the body. These covers and coatings are made out of biodegradable polymers.
Biodegradable Polymers – Summary
• Biodegradable polymers are the types of polymers that degrade within a short time and their byproducts are eco-friendly.
• It is a good solution for the environmental pollution occurred due to the non-degradable plastics.
• There are two main types of biodegradable polymers.
• They are agro polymers and bio-polyesters.
• Nowadays biodegradable polymers are widely used in medical applications considering their bio compatibility.