Abstract
Nanoemulsions are an isotropical mixture of oil, surfactant, and water with droplet diameter approximately in the range of 10-100 nm. They are being exponentially used for drug delivery systems for the influential administration of therapeutical agents because of their potential advantages over other approaches. Nanoemulsions can be used to design delivery systems that have increased drug loading, enhanced drug solubility, increased bioavailability, controlled drug release, and enhanced protection against chemical or enzymatic degradation. Moreover, nanoemulsions have better thermodynamical stability to flocculation, sedimentation, and creaming than conventional emulsions. Their small droplet dimensions and large droplet surface area positively influence drug transport and delivery, along with allowing targeting to specific sites. This chapter focuses on recent applications of nanoemulsions in the area of drug delivery.
TopIntroduction
Nanotechnology manipulates the molecular structure of materials to change their intrinsic properties and obtain the optimal materials with revolutionary applications. The use of nanotechnology techniques in the medical and pharmaceutical industry has gained momentum in recent years. Traditonally, nanoemulsions have been commonly used in clinics for over five decades as parenteral nutrition formula. The nanotechnology-driven pharmaceuticals are usually termed as “nanopharmaceuticals”. Nanoemulsions are oil-in-water (o/w) or water in oil (w/o) emulsions with mean droplet diameters usually ranging from approximately 50 to 500 nm. Submicron emulsions, ultrafine emulsions and miniemulsions can be also used to refer the nanoemulsions (McClements 2012).
Nanoemulsions possess the following advantages;
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Nanoemulsions possess a considerably higher free energy and surface area than that of other emulsions which allow them an effective transport system.
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Nanoemulsions is a primary method of encapsulation.
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When compared to dispersal systems, nanoemulsions are thermodynamically stable systems. Nanoemulsions for the delivery of bioactive molecules have a high kinetic stability.
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Nanoemulsions are biocompatible. Therefore, they are suitable for human and veterinary therapeutic purposes.
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The problems of inherent creaming, flocculation, coalescence and sedimentation are not issues for nanoemulsions.
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Nanoemulsions can be formulated in various formulations e.g. liquids, foams, creams and sprays.
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Nanoemulsions are non-toxic, non-irritant and non-allergic.
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Once nanoemulsions are formulated with surfactants, approved for human consumption (GRAS), they can be taken by enteric route (Shah et al., 2010)
Besides the advantages mentioned above, nanoemulsions also have some disadvantages:
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Advanced (=expensive) equipment and privite procedures are needed to prepare smaller size nanoemulsions.
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High concentrations of surfactant and cosurfactant for stability are needed.
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Surfactants can have toxic effect.
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Prepared nanoemulsions have storage problems.
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It is affected by environmental parameters such as temperature and pH.
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It has limited solubility for substances with high melting points.
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Organic solvents are difficult to remove from this formulation.
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Little is known about interfacial chemistry in nanoemulsion preparation.
It is estimated that the portion of nanoemulsions in the pharmaceutical market will increase by 8.6% until 2024 (Global Market, 2019). In order to actualize this expectation in the nanoemulsion market, the problems that appears during the nanoemulsion production process and storage stages should be eliminated and the biosafety of the product should be increased.
It is recommended to use Plan Do Check At (PDCA) and seven quality control (seven QC) tools together for impeccable production and protection of real-time product quality in industrial scale production of nanoemulsions (Fig 1).
Figure 1. PDCA cycle, B. Seven quality control tools (Rai and Sharma, 2021).
Key Terms in this Chapter
Surfactant: A compound that lower the interfacial tension between two liquids, between a gas and a liquid, or between a liquid and a solid.
Zeta Potential: It is the electrical potential at the slipping plane.
Drug Delivery: It refers to drug preparation, route of administration, site-specific targeting, metabolism, and toxicity are used to optimize efficacy and safety, and to improve patient convenience and compliance.
Chemical Stability: It refers to the potential changes in composition in the product due to chemical reactions that may occur, such as oxidation, polymerization, and hydrolysis.
Polydispersity Index: A numeric value gives information about the droplet size dispersion in the nanoemulsion.
Flocculation: It is a reversible phenomenon in which droplets dispersed in an emulsion clustered after random collision.
Nanoemulsions: A colloidal particulate system in the submicron size and their sizes varied from 10 to 1.000 nm.