surrounded by a single ultrathin membrane of polymer (reservoir systems for controlled release of drug) as depicted in Figure 5. The degradable polymers are ruptured into biologically suitable molecules that are assimilated and discarded from the body through normal route. The formulation is simple, which is totally free of organic solvent. Core is formed by hydrophobic block polymer blocks (poly-(propene glycol), poly-(caprolactone) etc.) Current polymers like Poly 2-hydroxy ethyl methacrylate, polyvinyl alcohol, Polyethylene glycol are used because of their inert characteristics and also they are free of leachable impurities [3] . These issues may include site specific drug delivery in subcellular organelles, harnessing chemical, physical and biological properties efficiently to optimize drug administrations. Hydrogels can be made both from natural and synthetic polymers. The major advantage of a controlled release drug delivery system is that it allows the release of drugs at controlled rates over long periods; it can be from days to months. Together they succeeded in preparing a cross-linking gel which absorbed up to 40% of water, exhibited suitable mechanical properties and was transparent. The responses vary widely from swelling/contraction to disintegration. Polymers span from their use as films or binders covering agents in tablets to flow managing agent in liquids or emulsions for improving drug security and to alter the delivering characteristics. Polymers are being used extensively in drug delivery due to their surface and bulk properties. Polymer selection greatly influences the performance of the drug delivery system. In hydrogels like drug delivery systems, the properties of polymer materials like PEG,(the easy polymer used to design hydrogels), can be managed to enhance features like size of the pore, which is used to manage rate of diffusion of the conveyer drugs. In these systems, a drug core is surrounded by a polymer film, and the drug release rate is controlled by the properties of the polymer (e.g., polymer composition and molecular weight), the thickness of the coating, and the physicochemical properties of the enclosed drug, such as solubility, drug … Reservoir based polymers is advantageous in various ways like it increase the solubility of incompetently soluble drugs and it lowers the antagonistic side effects of drugs [2] . Novel strategies like dendrimer synthesis and controlled polymerisation techniques are now well established. These systems introduced the following advantages compared with other methods of delivery: (1) the possibility of maintaining plasma drug levels in the optimal therapeutic range, (2) the eventuality to remove or decrease damaging side effects from systemic drug delivery by the local administration from a controlled release system, (3) drug execution may be improved and facilitated in organs that are not … Some polymeric systems conjugated with antibodies/specific biomarkers help in detecting molecular targets specifically in cancers. Polyglycolic acid (PGA) is a biodegradable, thermoplastic polymer and the simplest linear, aliphatic polyester. 15. Biodegradable systems can be made either by natural polymers (e.g. Silicone, cross-linked Polyvinyl Alcohol, and Ethyl Vinyl Acetate are mostly used in drug formulations. The total dose of a drug is lower than other drug delivery systems. Polymers have become an integral part of drug delivery systems due to their improved pharmacokinetic properties. The distribution of the size should be as narrow as possible since the rate at which the drug will be released as well as syringability depends on the size of the sphere directly. The cell division may be efficiently stopped near the center in solid tumor cells because of which chemotherapeutic agents become insensitive to chemotherapy. The cross linking density affects the permeability of the solute inversely, the higher the cross linking density, the lower the permeability [27] . Polymeric drug delivery has defined as a formulation or a device that enables the introduction of a therapeutic substance into the body. It is possible to reproduce the distribution of size of the microsphere particles but the result is not uniform generally and the standard deviation that we get is equal to half of the average size. Like other dendrimers, PAMAMs have a sphere-like shape overall, and are typified by an internal molecular architecture consisting of tree-like branching, with each outward “layer”, or generation, containing exponentially more branching points. Most of the times chemotherapeutic agents cannot penetrate and reach the core of solid tumors because of which they fail to kill the cancerous cells. oxidized iron or magnetite (dextran coated) and are injected into blood stream. Polypyrroles are conductin polymers, related members being polythiophene, polyaniline, and polyacetylene. Chitosan is a polysaccharide polymer. It reduces fluctuations in drug levels in the blood. Non toxic, biodegradable and biocom- This review discusses various mechanisms by which polymer systems are assembled in situ to form implanted devices for sustained release of therapeutic macromolecules, and highlights various applications in the field of advanced drug delivery.Download : Download full-size image. 8. Surface coating with hydrophilic polymers like Polyethylene glycol (PEG) minimizes their uptake by liver and enhances bioavailability. Production and hosting by Elsevier B.V. https://doi.org/10.1016/j.apsb.2014.02.005. With this as a goal, the rapid and successful translation of emerging polymeric drug delivery systems in the future can be derived by interdisciplinary and open-minded approach. PANAM (polyamidoamine) dendrimers are also being used as carrier of genetic material. Also, advances in polymer science and technology have enabled the economic manufacture and reproducible performance characteristics of drug devices. 10. Ozurdex, is a biodegradable sustained release intravitreal implant that delivers dexamethasone to the vitreous humor and retina in order to treat macular edema and noninfectious posterior uveitis. A high power magnetic field is generated outside the bodies which pull these drugs out of suspension and deliver the drug to a localized disease site. Polymers serving as drug carrier should be water soluble, nontoxic and non-immunogenic. Solvent activated systems like hydrogels swell and release the drug when exposed to aqueous environment; this mechanism is depicted in Figure 2. 16. A hindrance to oral administration of some classes of drugs, mainly peptides and proteins is caused due to hepatic first-pass metabolism [12] and degradation by enzymes within the gastrointestinal tract. Difficult to scale the process up and production in high amounts is expensive as microspheres are batch operations inherently [9] . A number of polymers have been studied systematically from this point of view and there is every indication that the systems described have the potential to become clinically valuable and therefore marketable drug delivery systems. Biggest benefit of utilizing polymers in drug delivery is their control (manipulation) on their properties (e.g. Mechanism and time taken for drug delivery system for a particular tissue or cellular compartment still needs to be studied. These polymers exhibit a non-linear response to a small stimulus leading to a macroscopic alteration in their structure/properties. The reservoir-based system is one of the most common controlled drug delivery systems to date. In these systems, a drug core is surrounded by a polymer film, and the drug release rate is controlled by the properties of the polymer (e.g., polymer composition and molecular weight), the thickness of the coating, and the physicochemical properties of the enclosed drug, such as solubility, drug … In biodegradable implants, drug release occurs during polymer degradation. This is quite common. They are being used in drug formulations and in drug delivery devices. 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