Nanoemulsion best material by shreya Document Transcript
Nano-EmulsionSubmitted to-Dr. Mansingh SirSubmitted ByShreya M. Modi M.Phil./Ph.D. inNano science and Nanotechnology,Central University of GujaratNANOEMULSIONAn emulsion is a mixture of two or more liquids that are normally immiscible (nonmixable orunblendable). Emulsions are part of a more general class of two-phase systems of mattercalledcolloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsionshould be used when both the dispersed and the continuous phase are liquids. In an emulsion,one liquid (the dispersed phase) is dispersed in the other (the continuous phase).Examples of emulsions include vinaigrettes, milk, mayonnaise, and some cutting fluidsformetal working. The photo-sensitive side of photographic film is also an example of a colloid.
The word "emulsion" comes from the Latin word for "to milk",as milk is (among other things)an emulsion of milk fat and water.http://www.emulsifiers.org/Images/MsImages/60-normal.jpgEmulsions are dispersions of droplets of a liquid phase in a different immiscible liquid [2–4]. Oildroplets dispersed in water are known as “direct emulsions”, whereas water droplets dispersed inoil are called “inverse emulsions”.Without shear, emulsions would never form, since the thermodynamic lowest energy state of twoimmiscible liquids is simply a layer of the liquid having lower density on top of a layer of theliquid having higher density.In order to create emulsions, shearmust be applied in a way that causes thedroplets of one phase to stretch andrupture, through a capillaryinstability, into smaller droplets.Stretching and rupturing the droplets is possible if the applied shear stress is greater than thecharacteristic Laplace pressure scale, _/a, where _ is the liquid- liquid surface tension and a is thedroplet‟s radius.
A surfactant, usually soluble in the continuous phase, coats the surfaces of the newly formeddroplets and provides a stabilizing repulsion between droplet interfaces that strongly inhibitssubsequent recombination, or coalescence, of the droplets.Microscale emulsions can be commonly made in the kitchen using shear stresses generated bywhisks, spatulas, and blenders; mayonnaise is a common food emulsion of oil droplets in waterstabilized by egg protein.However, obtaining nanoscale emulsions having droplet diameters less than 100 nm with thesemethods is generally not possible since the applied shear stresses are too low.http://www.dowcorning.com/images/discover/FS-chemcorner-water-oil-illust.jpgDue to their small droplet size,nano-emulsions may appear transparent, and Brownian motionprevents sedimentation or creaming, hence offering increased stability. In contrast tomicroemulsions, nanoemulsions are metastable and can be diluted with water without changingthe droplet size distribution .Microemulsion NanoemulsionMicroemulsions (ME) Nanoemulsion (NE) is kinetically stable.are thermodynamically stableLess globule size Higher globule sizeME have long term stability NE have less term stabilityPHYSICAL PROPERTY OF NANOEMULSIONNanoemulsions appear visibly different from microscale emulsions since the droplets can bemuch smaller than optical wavelengths of the visible spectrum.Microscale emulsions multiply scatter visible light  and unless the refractive index of thecontinuous and dispersed phases are matched by specifically altering the composition to achievethis, they appear white.
By contrast, nanoemulsions can appear nearly transparent in the visible spectrum and exhibitvery little scattering despite significant refractive index contrast. Quantitative measurements ofthe optical transparency of nanoemulsions in the visible and ultraviolet wavelengths are shownthrough transmission measurements.Nanoemulsions having a = 40 nm at several different φ have been loaded into 0.2 mm pathlengthquartz cells, and the percent transmission intensity has been measured as a function of lightwavelength. For all φ, the transmission in the visible spectrum is near 100%, especially towardred wavelengths, indicating a high degree of transparency.By contrast, in the ultraviolet(UV) part of the spectrum, as the wavelength of light begins toapproach the droplet radius, thenanoemulsions scatter light significantly.In the limit when the nanodroplets are much smaller than the wavelength of the incident light,one encounters the regime of „Rayleigh scattering‟.Nanoemulsions appear transparent, yet a bit bluish due to the dominance of low-wavelength lightscattered from them, and, when looking through them towards a white light source, they appeartransparent with a reddish tinge since the blue light is preferentially scattered away. The relativetransparency of Nano emulsions makes them ideal candidates for probe-based optical studies,such as micro rheology.Likewise, nanoemulsions exhibit enhanced shelf stability against gravitationally driven creamingover microscale emulsions at the same φ. Brownian motion, caused by entropic driving forces,keeps the droplets suspended even over very long periods of time.FORMATION OF NANOEMULSIONSONICATION METHODOne method for producing nanoemulsions is through ultrasonic agitation of a premixed emulsionof microscale droplets . The premixed emulsion has been made in advance usingunsophisticated mixing methods to fix the composition of the emulsion (i.e. C and φ). In theultrasonic method, a vibrating solid surface agitates the premixed emulsion at ultrasonicfrequencies, typically 20 kHz or larger, and high power, causing extreme shear and cavitationthat breaks up droplets.High-power ultrasonic devices include focusing horns and pointed tips. Since the emitted soundfield is typically inhomogeneous, in most ultrasonic schemes, it is necessary to recirculate theemulsion through the region of high power so that all droplets experience the highest shear rate.Reasonably uniform droplet size distributions at dilute concentrations can be obtained if theemulsion is re-circulated many times through the region of high shear.
HIGH PRESSURE HOMOGENIZERhttp://www.pharmainfo.net/files/images/stories/article_images/Nanoemulsions_image1.jpgA second high-throughput method for producing uniform nanoemulsions involves using high-pressure microfluidic devices to rupture droplets in concentrated emulsions .Rapidly flowing streams of a premixed emulsion are forced through rigid stainless steelmicrochannels, which have been fabricated using lithography and micromachining, to create anextremely strong extensional flow. The droplet sizes in the premixed emulsion are typically lessthan 10 μm, and the channel dimensions are typically closer to 100 μm.High-pressure air (typically around 100 psi) is mechanically amplified by a piston, whichoperates in a pulsed mode, to produce liquid pressures that can reach as high as about 30 000 psi.There are some problems which are associated with homogenizer such as poor solubility,component deterioration due to difficult mass production and generation of much heat.With this method only oil in water(O/W) liquid nanoemulsion of less than 20% oil phase can beprepared and cream nanoemulsion of high viscocity or hardness with a mean droplet diameterlower than 200nm cannot be preparedPHASE INVERSION METHOD
http://www.rsc.org/ej/SM/2011/c0sm00549e/c0sm00549e-f6.gifIn this method fine dispersion is obtained by chemical energy resulting of phase transitionstaking place through emulsification path.The adequate phase transitions are produced by varying the composition at constant temperatureor by varying the temperature at constant composition, phase inversion temperature(PIT) methodwas introduced by Shinoda et al. based on the changes of solubility of polyoxyethelene –typesurfactant with temperature.This surfactants becomes lipophilic with increase in temperature due to dehydration of polymerchain. But at low temperature, the surfactant nanolayer has a large positive spontaneouscurvature forming oil-swollen micellar solution phase.CHARACTERIZATION OF NANOPARTICALSNano-emulsions are not thermodynamically stable, and because of that, their characteristics willdepend on preparation method. Here some parameters are discussed which should be analysed atthe time of preparation of nanoemulsion.Phase Behavior StudyThis study is necessary in characterization and optimization of ingredients. This is used in caseof NE formulation prepared by phase inversion temperature method and self-emulsificationmethod.Particle Size AnalysisGenerally Dynamic Light Scattering(DLS) method are used.Surface Charge MeasurementSurface zeta potential of NE droplets should be measured with the help of mini electrode topredict the surface properties of NEs.
Transmission Electron MicroscopyTEM is used to observe the morphology in Nano-emulsionDrug ContainVarious methods especially Western Blot Method are used to determine the amount of drugcontained in formulation.ViscosityViscosity should be measured to ensure the better delivery of the formulation.Preliminary characterization: Cracking Observed for 48The stages of emulsions such as hours(maintained atCreaming constant conditions) Phase separationMorphology & structureMorphology and structure of nanoemulsion can be studied using TEM. The study of globuleshape and surface can be observed by TEM. To perform TEM observations, a drop of thenanoemulsion is deposited on the holey film grid and observed after drying.Advantages of nanoemulsion Reduction of globules:Increase surface area, Enhance solubility, Increase bioavailability They do not show the problems of flocculation, coalescence and sedimentation. They are non-toxic ,non-irritantLimitations OfNanoemulsionsAlthough this formulation provide great advantages as a delivery system for the consumers butsometimes the reduced size of droplets are responsible for the limited use of nanoemulsionformulation. Some limitations of nanoemulsion are as follows .The manufacturing of nanoemulsion formulation is an expensive process because size reductionof droplets is very difficult as it required a special kind of instruments and process methods.For example, homogenizer (instruments required for the nanoemulsion formulation)arrangements is an expensive process. Again microfludization and ultrasonication(manufacturing process) required high amount of financial support.Stability of nanoemulsion is quite unacceptable and creates a big problem during the storage offormulation for longer time of period. Ostwald ripening is the main factorassociated
withunacceptability of nanoemulsion formulations. This is due to high rate of curvature of smalldroplets show greater solubility as compared to large drop with a low radius of curvature.Less availability of surfactant and cosurfactant required for the manufacturing of nanoemulsionis another factor which marks as a limitation to nanoemulsion manufacturing.APPLICATIONS OF NANO-EMULSIONSThe compositional flexibility of nanoemulsions offers a wide range of applications.The incorporation of fluorescent dyes and other molecules into nanoemulsions makes theminterestingprobes for exploring properties of living cells and for drug delivery.Nanoemulsion vaccine could inactivate and kill the virus and then subsequently induce immunityto the virus that includes cellular immunity, antibody immunity and mucosal immunity.The deformable and liquid nature of the droplets may lead to discoveries of new pathways forcellular uptake and dispersal. Both oil-soluble and water-soluble drug molecules can beincorporated into the nanodroplets of direct and inverse nanoemulsions for potentialpharmaceutical uses.In the personal care and food industries, nanoemulsions may provide interestingalternatives aspleasantly transparent and soft solids that possess plastic-like rheologicalproperties. Whilebeing appealing from an optical and rheological point of view, nanoemulsionsalso can delivermoisturizers to the skin quite efficiently and also block ultraviolet lightwithout leaving a whiteresidue.The small size of the nanodroplets will likely increase transport efficiency of any active drugs orother molecules inside the droplets across biological membranes, including the skin. Thus,nanoemulsions may have significant applications in medical patches.In the printing and data storage industries, one may imagine the resolution of usingzeptolitredroplets instead of picolitre droplets.The precise manipulation and deposition ofsuch tiny droplets pose many technological hurdles,but the potential exists for creating piezodriven and thermally-driven printers usingnanoemulsion inks.The few examples covered in this section only begin to scratch the surface of the manypotential scientific discoveries and applications that will arise from nanoemulsion research.High-throughput production methodologies make nanoemulsions a realistic commercial-scalealternative for diverse areas, including lotions and pharmaceuticals.
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