Nanoemulsion of Water Insoluble Vitamins - Term Paper Example

Nanoemulsion of Water Insoluble Vitamins By Introduction Nanoemulsion is among the contemporary technologies used especially in pharmaceutical and food industries for production of drugs and materials such as fatty acids, colors, and flavors. The main benefits of nanoemulsion are good stability, optical clarity, coalescence, and flocculation. Nanoemulsion also improves bioavailability and absorption. A better understanding of the characteristics of nanoemulsion provides important information to guide in formation and application of nanoemulsion to water insoluble vitamins. Considering the importance of general application of nanoemulsions, clucidating procedures that govern the stability and formation of flavor would be essential. Typically, an emulsion is formed of two insoluble liquids whereby one of the liquids disperses as tiny droplets into the other liquid. There are different terms that are used to describe various forms of emulsions. This paper aims at discussing the formation, characterization, and application of nanoemulsion in water insoluble vitamins. The paper will begin by defining basic theories in nanoemulsion formation, characterization, and potential application of nanoemulsion in water insoluble vitamins. Formation of nanoemulsions Since nanoemulsion is a non-equilibrium system, it can be spontaneously formulated. Energy is a mandatory input during formation of nanoemulsion of water insoluble vitamins (A, D, E, and K). This energy is derived from chemical potential from compounds or from mechanical devices (Tal‐Figiel, & Figiel, 2008). The oil droplets contained in nanoemulsions are of nano-ranged sizes of between ten to hundred nm. These droplets are dispersed in an aqueous phase that is continuous and each oil droplet is bounded by surfactant particles. There are different methods used to formulate nanoemulsions (McClements, 2011). These methods are categorized into two broad groups; i) high energy approach, and ii) low energy approach. High-energy emulsification approach The formation of nanoemulsions using energy is generally done using mechanical shear like the energy produced by high-pressure homogenizers, high-shear stirring, and ultrasound generators. There are several processes that take place during the formation of water insoluble vitamins (especially vitamins A, D, E and K). These processes include the breakup of oil droplets, surfactant molecule absorption, and collisions of droplets, which may result in larger droplets and coalescence. These processes take place simultaneously because the timescale for each process is usually small (microseconds). For instance, the breaking of the vitamin A is sometimes feasible if the force of deforming is higher than the Laplace pressure, Pl (difference between droplet’s inside pressure and the droplets outside pressure). This is an interfacial pressure that acts to prevent droplet deformation. The smaller the size of vitamin A in a system, the higher the amount of energy or surfactant required. Consequently, the formation of nanoemulsions like vitamin A can cost higher than formation of conventional emulsions (macroemulsions). The effect of inputing energy on oil droplet size reduces the size of the droplet decreasing the ration of surfactant or oil or increasing the homogenization pressure. At high ratio of surfactant/oil the size of vitamin A depends on energy input since there is insufficient surfactant concentration to stabilize the small droplets. It is evident that the apparatus that supply available energy within the shortest duration and with the most flow of homogeneous produces smallest sizes of vitamins. Homogenizers with high pressure meet these requirements. Due to this factor, they are the widely used forms of emulsifying machines in preparation of nanoemulsions (Skiff, Baaklini & Vlad, 2006). Although ultrasonic is also another efficient emulsification in reduction of droplet’s size, it is appropriately for only small batches. Considering the aspects of mechanical energy, formation of nanoemulsion should be considerably expensive. However, it is understood that when the advantage of physicochemical properties is taken, there can be spontaneous production of dispersions. This is a similar case with low-energy emulsification approach. In practice, these two types of emulsification are usually combined together (Solans et al, 2005). Formation of vitamin D During the formation of vitamin D, the size of droplets and stability characteristic in vitamin D enables it to be prepared through spontaneous emulsification (SE). Spontaneous emulsification centers on formation small vitamin droplets when a surfactant/oil mixture is titrated to form an aqueous solution. Nanoemulsions with small vitamin D droplets diameters can be formed using Tween 80 at a very high stirring speed of approximately 800 rpm. The thermal stability of vitamin D during formation is increased by adding more surfactant such as sodium dodecyl sulphate. The spontaneous emulsification formation method is inexpensive ad simple to form vitamin D and therefore it can be widely used in delivery systems for personal care, food, and pharmaceutical applications (Skiff, Baaklini & Vlad, 2006). The same spontaneous emulsification formation method is used in preparation of other water-insoluble vitamins such as vitamin E and vitamin K. Formation of vitamin E Vitamin E is commonly formed using emulsion phase inversion method (EPI) due to its low cost advantage. This emulsification method simply means titrating water into a liquid mixture that contains surfactant and oil. This initially results in formation of “water-in-oil” emulsion and later inverts into “oil-in-water” emulsion. This method produces vitamin E particles with mean diameter of 40 nm and final composition of 8 wt% of vitamin E acetate. Due to its bioactive factor, Vitamin E is particularly encapsulated using emulsion-based delivery method that is mainly used for bioactive lipids (Qian & McClements, 2011). For instance, vitamin E emulsions can be formed by adding vitamin E acetate into an OS (octenylsuccinic starch solution mixed with distilled water and homogenized in a micro fluidizer at approximately 20,000 psi. Formation of vitamin A The useful formula used during formation of vitamin in emulsions is O/W/O (oil-in-water-in-oil). This is due to its stability characteristics. The formation of vitamin A involves several processes (degradation process and addition of antioxidants whose main purpose is to stabilize vitamin A droplets. All forms of vitamin A are accelerated through increment of the content of oil in the emulsion and therefore, dehydration for anhydrovitamin A is highly preferred with increasing the content of water (Maali & Mosavian, 2013). The O/W/O method is highly preferred because of its potential application in cosmetic, chemical, agricultural, and pharmaceutical industries. Formation of vitamin K Because vitamin K is a water insoluble vitamin, there are several solubilization methods that can be used for its formation. The vitamin K droplets contained in nanoemulsions are of nano-ranged sizes of between ten to hundred nm. These vitamin droplets are dispersed in an aqueous phase that is continuous and each oil droplet is bounded by surfactant particles. Since the vitamin particles are insoluble in water they are then separated from the liquid through a titration (Lennon et al, 2003). This is widely used method for formation of vitamin K because it is cost effective. Comparison Vitamin A, D, E, and K appear much smaller than micro scale emulsions because their size can be even smaller than visible spectrum optical wavelengths. Micro scale emulsions increase the visible light and unless the dispersed and continuous phases are matched through alteration of the composition in order to attain this, they have a white appearance (Cueman & Zatz, 2008). In contrast, insoluble vitamins can appear almost transparent and have less dispersion despite important contrast of refractive index. Stability of water insoluble vitamins The key instability mechanisms that are applied to complete emulsions’ separation phase include coalescence, creaming, Ostwald ripening, and flocculation. However, insoluble vitamins do not sediment or cream due to the Brownian motion that is larger compared to the rate of creaming that is induced by gravity (Solans & Solé, 2012). In practical, the creaming of vitamin droplets that are smaller than 1 um is terminated by their diffusion rate which is always faster. Based on flocculation of vitamins of nanoemulsions, it is unclear whether small vitamin droplets can adhere and result in thin flat films as it is the case with large droplets. Due to their small size, they have very high curvature and Laplace pressure helps to oppose deformation (Mason et al, 2006). On the other hand, the Brownian motion (thermal agitation) of the small droplets can increase collisions thus enhancing deformation. Anyway, there is spontaneous flocculation achieved if the interaction energy is deep enough to enable it to overcome the droplet’s thermal energy (Qian & McClements, 2011). There are two key interaction potentials that are considered in the systems that are stabilized through nonionic surfactants. The vitamin droplets are attracted by interaction of van der Waals, which can be stabilized due to barrier of energy because of repulsion of steric (McClements, 2012). The repulsion of steric, Ws, is discussed in details by many authors. Vitamins with Brownian motion which steadied by nonionic surfactants remain un-flocculated in case the minimum Ostwald rate increases the coefficient diffusion. However, this is a relatively small effect because micro emulsion particles have small diffusion coefficients compared to molecules (Maali & Mosavian, 2013). The theory of LSW assumes these droplets have separation distance that is larger than diameter, and it is molecular diffusion that causes transportation of the separated components. The concentration of dissolved particles is constant but not when they are adjacent to the boundaries of droplets (Kang et al, 2008). These assumptions might be invalid for nanoemulsions since Brownian motion due to its strength may cause convective diffusion increasing the rate of diffusion. However, convective diffusion does not cause changes to the Ostwald ripening processes fundamental nature. Physical characterization of nanoemulsions Insoluble vitamins (A, D, E, and K) have numerous physical characteristics that are different from those of large micro scale emulsions. In this section, the discussion is going to be focused on some of the physical characteristics that differentiate nanoemulsions from larger micro-scale emulsions. This will be done by examining their relative transparency, how they respond to mechanical shear (rheology), and the stability they have against gravitationally based creaming (Friberg, Goldsmith & Hilton, 2008). Although there are other characteristics, this view serves as the main ones. Some rheological or mechanical shear characteristics of nanoemulsions are affected by the size of the vitamin droplets. As with larger emulsions, the mechanical shear characteristics are based on the interaction of the droplets, which can be either attractive or repulsively (Cheong & Tan, 2010). For all dilute ǿ, the mechanical shear viscosity of nanoemulsions that are repulsive resemble that of large emulsions or hard spheres. The reason behind this is that the Einstein interaction of dilute dispersion viscosityof hard domains depends on ǿ. In contrast, when there is high when the droplets starts to deform, the elastic modulus are proportional to Laplace pressure of all undeformed droplets. Thirdly, nanoemulsion exhibit higher shelf stability against creaming of gravitation over large emulsions. Entropic forces causes Brownian motion that keeps the emulsion droplets suspended for a very long duration. The height of gravity which is associated with atmospheres colloidal law in nanoemulsions is achieved by equating the potential energy of gravity of the droplets that are above the surface. Therefore, the volume of nanoemulsions of small droplets remains homogenous indefinitely, even when they are stored in large and tall containers. In contrast, micro scale emulsions have a height of 1cm, therefore, these droplets will definitely cream and turn inhomogeneous if stored for a long duration (Bielecki & Kalinowska, 2008). If the interaction between the droplets is changed to a more attractive this results in rapid creaming than with individual droplets resulting in inhomogeneous. Therefore, a strong attractive nanoemulsion creaming as a strong attractive emulsions (Zhang, 2011). Application of nanoemulsions of water insoluble vitamins There are many exciting possibilities that exist for scientific applications and directions in the contemporary field of nanoemulsions. These scientific directions include the essential structures as well as physical characteristics of foams, dispersions, and aggregates. Applications of nanoemulsions of water insoluble vitamins include food products, personal care products, and in pharmaceuticals (Morgan, Hosken & Davis, 2000). The understanding of the structure of disperse foam over a wider фrange of between volume fraction of glass transition and limit of dry-foam-like still remains as an open problem (Solans et al, 2003). Scientists devised a structure of highly deformed droplets with minimal structure that packs ordered lattice in dry limit with its neighbors. Although people thought that this type of structure had small surface area, when the deformed droplets are packed in a proper manner with two different shapes, one shape can obtain the lower surface area (McClements & Rao, 2011). Currently, a simulation of disperse foam in dry limit provided numerous essential details on distribution of facet sizes and edge lengths in disperse disordered foam that contain bubbles with identical volumes. Because many scattering light causes problems to micro scale and large droplets and bubbles experiments, neutron scattering can easily be brought into one scattering regime. This is a promising approach of probing this structural transition (Uson, Garcia & Solans, 2004). More research is required to help in thorough understanding of the structure deformable objects interfaces over a broad range of surface, whereby nanoemulsions can play a very essential role in the exploration. The nanoemulsions compositional flexibility provides a broad range of their applications. The incorporation of molecules and fluorescent dyes into nanoemulsions makes them suitable for exploration of properties of drug delivery and of living cells. The liquid and deformable nature of these vitamin droplets leads to discovery of new pathways for dispersal and cellular uptake. Both water-soluble drugs and oil-soluble molecules can be combined into droplets of both inverse and direct nanoemulsions of potential pharmaceutical applications (HamedMosavian, 2013). In food industries and personal care, nanoemulsions provide significant alternatives as soft solids and pleasant transparent solids that have plastic-like rheological characteristics (Nielsen et al, 2004). In addition, nanoemulsions are appealing from a rheological and optical point of view, and therefore, they can be used to produce skin moisturizers that are quite efficiently as well as blocking ultraviolet light from affecting the skin without leaving any white residue. The small size gives nanodroplets ability to increase efficiency in transportation of active drugs or any other molecules that are inside droplets of biological membranes such as the skin (Gutiérrez et al, 2008). Therefore, nanoemulsions have important applications in the field of medical patches. In addition, in the data storage and printing industries, many people prefer using droplets of zeptoliter instead of droplets of picolitre. The precise deposition and manipulation of these tiny droplets cause numerous technological challenges, however, there is potentiality of creating thermally-driven and piezo-driven printers that use nanoemulsion inks (Bouchemal, Briançon, Perrier & Fessi, 2004). The few examples that have been given in this paper represents the many potential discoveries of scientists and applications of nanoemulsions that arise from their research. A large group of production methodologies make use of nanoemulsions as a realistic general-scale alternative in many different production areas that include pharmaceuticals and lotion production (Meleson, Graves & Mason, 2004). Nanoemulsions represent a flexible policy for production of soft materials easily for tailoring due to their stability, optical, and rheological characteristics (Chanamai, 2006). Through fractionation, nanoemulsions can also be used to make material models that provide vital scientific understanding of main structure of attractive gels and disordered glasses. In general, nanoemulsions is one of the intriguing current classes of dispersion that will be widely used for commercial importance in future (Garti, Jacobs, Lane & Zakharia, 2003). Emulsions are broadly used in production of beverages because it is necessary to mix water insoluble flavors to form aqueous beverages. However, the beverages are always desired to have clear appearance and this can only be achieved through nanoemulsification. The main solution for this clear appearance is the use of cosolvent specifically alcohol, which is introduced as solvent or flavor carrier. However, flavors that are alcohol-based have transportation issues because of their flash. The usage of alcohol disqualifies products from obtaining Halal certificates, which are desirable in several countries. Nanoemulsion can address this issue because emulsions with MDD that are below hundred nm have the capability of providing transparent appearance to beverages without clarity loss (Wooster, Golding & Sanguansri, 2008). In addition, nanoemulsion has unique application, which is non-weighted flavors. For emulsion of conventional flavors, weighing agents such as brominated vegetable oil and ester gum are mainly used in weighing of the phase of oil and reduction of contrast of density between aqueous and oil phases. These weighing agents effectively decrease the creaming of droplets velocity (Anton, Benoit & Saulnier, 2008). However, they have strict consumption limits because of their toxicity. The weighing agents also can be produced through nanoemulsion process because of their higher stability against creaming. This higher stability offers a cleaner label (Tadros, Izquierdo, Esquena & Solans, 2004). The pharmaceutical field is the dominant industry, which makes use of nanoemulsion application. Researches have been conducted on systems of drug delivery with advance solubilization of water insoluble drugs and enhanced bioavailability due to incorporation of nanoemulsions. In the food production industries, many bioactive compounds show effective health advantages when used in high concentrations (Jenning, Schäfer-Korting& Gohla, 2000). Unfortunately, a large number of these compounds show poor solubility in foods that are aqueous-based. Conclusion In conclusion, this paper has provided the current activities that surround the formation, characterization, and application of nanoemulsion of water insoluble vitamins. The paper also emphasizes for more applications and research of nanoemulsions. Just the same way dispersion of particulates such as nanoscale have been given much attention, nanoemulsions of water insoluble vitamins is beginning to gain significant attention as well. Although there are already known emulsification basic principles for isolated droplets, the current emulsification principles govern coalescence and rupturing of nanodroplets in a broad shear are being discovered. There is sorely requirement of quantitative theoretical assumptions of distribution of droplets that include combination of the above effects. Once nanoemulsions are formed, there are precise ways in which they can be controlled and manipulated. References Anton, N., Benoit, J. P., &Saulnier, P. (2008). 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