Mata Gujri College of Pharmacy; Kishanganj, Bihar-855107.
Biodegradable polymer materials (known as biocomposites) are widely used for manufacturing of drug delivery technology for controlled and sustained release pattern. The building blocks of plastic materials are polymers, which are constantly being used in an increasing number of applications. Because of this, a lot of researchers are devoting their efforts to creating innovative polymer composites using components that exist naturally as well as changing conventional materials to make them more user-friendly. The utilisation of biopolymers and biofibers as raw materials is done with consideration for the environment. These days, scientists are adding tiny amounts of a novel type of substance called a nanofiller to a variety of biopolymer-based composites. These nanofillers will function as additives, improving the mechanical, thermal, flame-retardant, and water-absorption behaviour of the nano composite materials while preserving their ideal density. An overview of the many biodegradable polymers that are now in use, their characteristics, and recent advancements in their synthesis and uses are provided in the review that follows.
Many scientists are still interested in the development of novel biopolymer materials, which has been going on for a while because synthetic plastics do not break down easily, there is a worldwide drive to develop biodegradable polymers in order to dispose of them. As these materials continue to be developed, industry needs to find innovative applications for them. [1]
Biodegradable polymers are frequently used to lower the amount of waste produced. Biopolymers offer several qualities in addition to being biodegradable, such as air permeability, low temperature seal ability, availability, and affordability. A variety of biopolymers are utilised in packaging, including chitosan, starch, cellulose, PLA, PCL, and PHB. The usage of mixes of various biopolymers, such as starch-PLA and starch-PCL blends, is currently popular in food packaging. [11]
Biodegradable polymer-based nanoparticles have proven to be a valuable tool in the treatment of neurodegenerative diseases due to their high drug-loading capacity and ability to cross the blood-brain barrier. [26] Additionally, their size, shape, and available surface area for biomolecule conjugation make them useful in the diagnosis and treatment of cardiovascular disease. In the event that an unstable active ingredient is present, polymeric nanoparticles can preserve the integrity of drug molecules for more effective distribution because of their capacity for long-term protection. For instance, nitric oxide molecules can be contained in PLGA nanoparticles by employing (trans- [RuCl ([15] ane) (NO)]2+) as a nitric oxide donor; PLGA-poly (ethylene glycol) (PEG) shields curcumin from macrophages; and PEG lessens the toxicity and makes gold nanoparticles more stable.[4][27]
The purpose of this review of the literature is to give information about the developments made in the field of biodegradable polymer materials. We'll look at biodegradability, component materials, uses, biodegradation processes, and the materials' effects on the environment and the economy.
Classification:
Figure 1: Classification of biodegradable polymer
Starch: One well-known hydrocolloid biopolymer is starch. It is one of the most affordable biodegradable polymers and a low-cost polysaccharide that is widely accessible. Typically, starch is utilised as a thermoplastic. Agricultural plants synthesise hydrophilic starch in the form of granules. The primary sources of starch extraction include potatoes, corn, wheat, and rice. It is made up of two types of polymers: amylopectin (poly-?-1, 4-Dglucopyranoside and ?-1, 6D-glucopyranoside) and amylose (poly-?-1, 4-Dglucopyranoside), which is a branching and amorphous polymer. Depending on the source, starch contains varying amounts of amylose and amylopectin, ranging from 10–20% amylase and 80–90% amylopectin. Amylose has a helical shape and dissolves in water. [11]
Polylactic acid (PLA): Typically, lactide, a cyclic dimer of lactic acid, is polymerized by ring opening polymerization or polycondensation of D- or L-lactic acid to produce PLA. There are two types of lactide: L-lactide and D-lactide. L-lactide is the natural isomer, and DL-lactide is the synthetic mix. Various other synthetic techniques have also been investigated. Because PLA has –CH3 side groups, it is a hydrophobic polymer. Because of the methyl side groups' steric shielding effect, it is more resistant to hydrolysis than PGA.[11] By using ring opening polymerization, high molecular weight PLAs can be synthesised. By changing the ratios of the two enantiomers, this method also enables control over the final PLA characteristics. Additional pathways include chain extension reactions, solution polymerization, and melt/solid state polymerization. PLA with a high molecular weight exhibits superior mechanical qualities. [5]
Collagen: It is derived from a variety of animals, including humans, horses, pigs, and cows, and it has numerous biological uses. Fibroblasts, which are derived from pluripotent adventitial cells or reticulum cells, synthesise collagen. Collagen can be divided into several groups, such as classical fibrillar and network-forming collagens, collagens associated with fibrils that have interrupted triple helices, collagens connected with membranes that have interrupted triple helices, and collagens with multiple triple-helix domains and interruptions. Selecting a specific collagen for a certain application is aided by its amino acid content and sequencing. [2][28-30]
Plant oil nanocomposites: The creation of plant oil/clay nanocomposites through the curing of epoxidized soybean oils (ESO) in the presence of organophilic MMT is the greatest example.In order to boost the thermal stability of the nanocomposites, it was discovered that the additive was randomly mixed and intercalated into the polymer matrix. The additive also resulted in a homogenous structure of organic and inorganic materials. Following dynamic viscoelasticity analysis (DVA), it was established how clay incorporation's reinforcing effect resulted from silica nanolayers' increased surface area and high aspect ratio. [19]
Polyhydroxybutyrate (PHB): PHB is an uncommon instance of a biocompatible and biodegradable hydrophobic polymer. Its crystalline degree is almost 80%, and it has a high melting point of 170-180 °C. PHB is brittle and stiff; the degree of fragility depends on the polymer's microstructure, glass transition temperature, and recrystallization. It grows increasingly brittle the longer it is stored. Its broader application is restricted by thermal instability that arises from continuous high-temperature polymer manufacturing as well as its propensity to fracture. Addition of various nucleation agents improves the mechanical and thermal properties. The most often used technique for altering the initial characteristics of PHB is unquestionably the mixing of the main polymer component with additives or other polymers. PHB is generally available for use since it can be processed using standard technological procedures for processing plastics. [9,31,32]
Polycaprolactone (PCL): PCL is a semicrystalline aliphatic polyester that has a high degree of biocompatibility and a delayed rate of biodegradation. Ring opening polymerization of ?-caprolactone using a variety of anionic and cationic catalysts yields PCL. It is appropriate for the creation of prolonged-release delivery systems because of its delayed biodegradation.
Its hydrophobicity is the primary issue, but it can be resolved by mixing it with other man-made or natural polymers to enhance its mechanical characteristics and biocompatibility. [9]
Biological Materials & Biodegradable Plastics: Four major feedstock categories provide naturally existing biopolymers (Tharanathan 2003). Collagen and gelatine come from animal sources, whereas chitin, which is converted to chitosan, comes from marine sources. Scientists are focusing their attention primarily on the remaining two feedstock categories, which are seen the most promising for future growth and development. Polyhydroxy alkenoates (PHA) and polylactic acid (PLA) can be produced from microbial biopolymer feedstocks. The last class of agricultural feedstocks is the biopolymer source that the University of Saskatchewan in Saskatoon, Canada, is now studying. This type of polymer belongs to the lipid and fat and hydrocolloid groups.
Fibres that serve as reinforcing fillers are another type of agricultural feedstock utilised in the biopolymer industry. This category contains cellulose, the primary structural element of hemp and flax fibres and a highly polar substance (Bismarck 2002). Strong mechanical qualities, low cost, and biodegradability characterise natural cellulose fibres. Because of these qualities, cellulose fibres are the most often used natural filler in plastic polymers. The second common biopolymer that is created by microbial fermentation is polylactic acid. Lactic acid, which is obtained through fermentation processes, condenses to generate it (Jopski, 1993). A thermoformed, all-natural plastic container made of PLA derived from corn has just been made commercially accessible by Wilkinson Manufacturing Co. (Fort Calhoun, Nebraska, USA). Natural plant sugars are produced by breaking down the carbon contained in plant starches. The PLA is created via separation and fermentation. Because they are not present in nature, PHA and PLA are both regarded as synthetic polymers. But they are completely biodegradable. (Stevens, 2003). [1]
Figure 2 Analytical methods of biodegradable polymers
Analyses methods of biodegradable polymers:[6]
Blends:
Biodegradation of Biopolymers: The polymer first breaks down into its monomers, which are then mineralized, during breakdown. Many factors influence biodegradation, such as the type of organism, the pre-treatment type, and the properties of the polymers. The list of variables influencing the polymer biodegradation rate is displayed in. The properties of the polymer, including its molecular weight, mobility, tacticity, crystallinity, and substitutions in its structure, as well as any plasticizers or additives put to it, all have a significant impact on how quickly the polymer degrades. The following types illustrates the reactions that take place when polymers biodegrade. [36, 37]
Tests for Biodegradation:
Biodegradable Alternatives To Conventional Plastics: Many bioplastics may be processed using methods commonly employed in the polymer industry, such as compounding, film processing, and moulding, and have mechanical qualities comparable to those of their conventional equivalents, such as PP, PS, and PE. Their use has been observed in numerous applications with short service lives where biodegradability is a crucial benefit, such as consumer packaging (e.g., trays, pots, films, and bottles in food packaging), disposables for convenience food (e.g., cutlery and tableware), bags (for shopping, gardening, or household waste), mulch films for agriculture, personal care disposals (e.g., nappies), and even golf tees. [41, 42]
PLA is 100% biobased, completely biodegradable (although only in specific situations), and may be composted in an industrial setting. It is also environmentally benign. Additionally biocompatible, PLA shouldn't have any harmful or carcinogenic consequences when applied locally to tissues. Its thermal processibility is superior than that of other biopolymers, such PCL. PLA degrades slowly and is also comparatively hydrophobic. Tensile strength and elastic modules are similar to PET. [9]
Self-healing antimicrobial biopolymer film for food packaging: When dynamic molecules like antimicrobial chemicals are infused into food products, their antimicrobial qualities become even more crucial in controlling undesirable microbes. Films have also been modified to include antimicrobial substances for use in active packaging. Because these films rely on dispersion through the packing media rather than a triggered release of antimicrobials via responsive polymers, they are regarded as active. Films infused with antibacterial/antifungal substances like sodium benzoate and benomyl were used in early studies in this field. It has been investigated to use natural antibacterial compounds such as clove, pepper, cinnamon, coffee, and others in both edible and inedible films. Another biologically generated substance, chitosan, has also been extensively studied because of its inherent antibacterial properties and lack of toxicity. According to Rhim et al., chitosan-based nanocomposite films with Ag-Ion and Nano-silver incorporation exhibit antibacterial qualities and improve food safety and quality by lowering the growth of contaminating microorganisms following post-processing. [12,43, 44]
Nanofillers on biodegradable polymer: Nanoparticles are being incorporated into newly developed composite materials for a range of application levels. In the matrix where the bio fibre is chosen as reinforcement, nanoparticles must be added. This particular nanoparticle serves to enhance the material properties of the resultant composite materials, including their optical, mechanical, conductivity, energetics, and surface morphology.
Our forests and farmlands provide the necessary biofibre. The separated portions of the plant biomass, cellulose derived from bacteria, cellulose chemically regenerated from cellulose that is naturally present, and cellulose created by tunicates are all referred to as biofibres. Additionally, these fibres are taken from animals in the form of wool, silk, feathers, and hairs. [17]
Properties of Polymer Nanocomposites:
Biodegradable Polymer-Based Drug-Delivery Systems for Ocular Diseases: A wide range of conditions that could impair vision can affect the anterior and posterior portions of the eye. Notably, the anterior segment is primarily affected by diseases such as glaucoma, anterior uveitis, and ocular surface ailments like keratoconjunctivitis and dry eye disease. On the other hand, disorders such as diabetic retinopathy, age-related macular degeneration, and retinal vascular occlusions often impair the posterior region. Biodegradable DDSs have garnered increased interest recently, which is indicative of their potential for treating a range of ocular ailments. They offer opportunities for focused and targeted drug delivery, enhance drug stability and bioavailability, and enable a tailored and sustained release of therapeutic substances. As a result, there is a decrease in systemic side effects and an overall improvement in medication efficacy.[16]
Manufacturing of biobased food packaging: Understanding the processing and material characteristics of the polymers is necessary for the engineering of a biobased package or packaging material. A specific modification of the polymer is necessary if the original biopolymer's characteristics differ from the necessary ones or if the polymer isn't naturally thermoplastic. Even after adjustments, it is doubtful that one polymer will be able to supply all the necessary qualities for highly particular needs (very low gas permeability or strong water resistance). As a result, a composite, laminate, or co-extruded material must contain a variety of components. [11]
Possible products produced of biobased materials: Most biobased polymers that have been previously discussed have the same basic repeating chemical units as a large portion of conventional plastics. Therefore, in the broadest sense, proteins (repeating peptide functionality) can be thought of as the synthetic polyamides, polylactic acid is just one example of the diverse group of polyesters, and poly-saccharides with repeating acetal functionality can be thought of as the naturally occurring analogues of the synthetic polyacetals.
Since the 18th century, when the food business first emerged, the packaging sector has undergone significant advancements, with the most significant and clever changes taking place in the last century. Food safety and quality have increased as a result of these developments. The majority of inventions have been fueled by shifting customer tastes, however some have come from unexpected places. The majority of the recent developments have gone towards slowing down oxidation and managing moisture migration, microbial development, respiration rates, and volatile flavours and scents. This focus is similar to that of food packaging distribution, which has sparked changes in the important domains of sustainable packaging, competitive advantage via the utilisation of packaging value chain interactions, and the changing role of food service packaging. Biopolymers have had a significant impact on packaging.
Biodegradable and biocompatible polymers in bone and muscle tissue engineering: The body has a variety of tissue types, each with distinct ECM compositions and structural traits. The capacity to tailor the scaffold's properties is particularly beneficial when considering the type of tissue that has to be replaced. Bones provide more strong physical stability and a greater ECM:cell ratio, mostly composed of collagen, supporting and shielding the body. However, the requirement for skin and muscles to stretch as opposed to exerting such mechanical strength results in an increase in the ECM's elastin component. To improve the efficiency of movement, ligaments and tendon flexibly transfer loads between muscles and bones by expanding and contracting. They must have high mechanical and tensile strength, which may be achieved with plenty of collagen structures that are aligned. [13, 53, 54] The unique requirements of tissue scaffolds in terms of biocompatibility and biodegradability, as well as the intricate relationships between them inside the human body, present unique challenges for this field of study. Not only should a scaffold function and decompose appropriately, but it should also do so for the appropriate tissue type, as each has unique mechanical and morphological requirements. While a low dispersion is desirable, the kind of tissue affects other characteristics as well, such as strain values, Tg, and crystallinity. The kinetics of polymer breakdown need to be controlled to avoid breaks and inflammation throughout the healing process. [55, 56]
CONCLUSIONS:
Biodegradable polymers with the essential qualities of both biodegradability and biocompatibility have demonstrated their versatility and great potential in the biomedical arena. The market's move towards biomaterials is a reflection of the enormous amount of work that has gone into creating these polymers. The significance of these remarkable materials is demonstrated by their applications in a wide range of fields, including tissue regeneration, enzyme immobilisation, controlled medication administration, gene transfer, and surgical sutures and wound dressing. The development of innovative approaches for a range of therapies is facilitated by the introduction of biomaterials based on biodegradable polymers and their ability to overcome related drawbacks. Significant advancements in this field, such as Nab technology, and the ongoing growth of research in this area are examples of the important contributions these polymers have made.
REFERENCE
Tanmay Mohanta*, Shubhra Tarafdar, Shivani Raj, An Overview on Biodegradable Polymer: Environmental Protection And The Maintenance of Physical Health, Int. J. of Pharm. Sci., 2024, Vol 2, Issue 7, 1044-1057. https://doi.org/10.5281/zenodo.12739641
10.5281/zenodo.12739641
