Nanoemulsion

THE IDEA Proposed by Richard Feynman

in his book titled There’s Plenty of Room at the Bottom

Feynman considered the possibility of direct manipulation of individual atoms as a more powerful form of synthetic chemistry than those used at the time.

The idea of nanotechnology was born.

contents:

• contents • Introduction • Advantages & Disadvantages • Formulation aspect of nanoemulsion • Preparation of nanoemulsions • Characterization of nanoemulsion • Applications of nanoemulsion• Marketed formulations • Conclusion

INTRODUCTION

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The term "Nanoemulsion" refers to a thermodynamically stable isotropically clear dispersion of two immiscible liquids, such as oil and water, stabilized by an interfacial film of surfactant molecules. A Nanoemulsion is considered to be a thermodynamically or kinetically stable liquid dispersion of an oil phase and a water phase, in combination with a surfactant.

The dispersed phase typically comprises small particles or droplets, with a size range of 5 nm-200 nm, and has very low oil/water interfacial tension.

NANOEMULSION• Nanoscale emulsion having size less than 100nm.• Due to their small droplet size, nano-emulsions may

appear transparent, and Brownian motion prevents sedimentation or creaming, hence offering increased stability.

• In contrast to microemulsions, nanoemulsions are metastable and can be diluted with water without changing the droplet size distribution.

• Nanoemulsion are thermodynamically stable system in which the two immiscible liquid (water and oil) are mix to form a single phase by means of appropriate surfactant .

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Nanoemulsions Emulsion

Microemulsion

Nanoemulsion

Thermodynamically unstable Opaque High energy required to form

Thermodynamically stable Clear It forms spontaneously

Thermodynamically or kinetically stable Clear High shear application to form

Int. J. Nanomed. 2014,9,pp 1-8

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The key difference between emulsion,microemulsion and

nanoemulsionEmulsion Microemulsion NanoemulsionThermodynamically unstable

Appearance: cloudy

Form only after application of the large input energy

Thermodynamically stable

Appearance: clear or translucent

It forms spontaneously

Thermodynamically stable Or Kinetically stable

Appearance: clear or translucent

Form only after application of the higher shear

Nanoemulsions - Classification Depending on the composition :

O/W : oil droplets dispersed in continuous aqueous phase

W/O : water droplets are dispersed in continuous oil phase

Bi-continuous : microdomains of oil and water are dispersed within the system

J. Mat. Chem. 2012, 22, pp 9767-9773

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Nanoemulsion: Lipid monolayer enclosing a liquid lipid core.

Liposome: Lipid bilayer enclosing an aqueous core.

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• Internal structures depend on relative component amounts, concentrations and other characteristics.

• The relative oil and water domains that form in nanoemulsion systems are usually so small (about 10-20 nm or less in diameter) that they do not scatter light.

Nanoemulsions and Subnanoemulsions

(1)nanoemulsion: d 10-100nm, thermodynamic stability system

appearance high Concentration of emulsifiers (20-30% of

dispersed phase) mix with water and oil within certain ranges low viscosity low surface tensionFormation mechanism has not been clear completely.

(2)subnanoemulsion: d 100-500nm, better stability when compared with common emulsions while poorer stability when compared with nanoemulsion

both can be used as drug vehicles! sustained

and prolonged release!

• Macro emulsions are dispersions of at least two non-miscible liquids.

• They are thermodynamically unstable systems that are stabilized kinetically.

• Consequently, the stability of an emulsion depends both on its composition and the size the emulsion droplets.

• Depending on the preparation method, different droplet size distribution might be achieved, explaining why the route of preparation can have an influence on the emulsion stability.

• Due to their small droplet size, nanoemulsion may appear transparent and Brownian motion prevents sedimentation or creaming, hence, offering increased stability.

• The preparation of emulsions with droplet sizes in the sub micrometer range may be performed mechanically, which involves high-shear stirring, high-pressure homogenizers or ultrasound generators.

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MACROEMULSION NANOEMULSION

Thermodynamically Unstable but stabilized kinetically.

Stable

Loading dose Good Poor

Preparation Method

Bottle method, wet gum method, etc.,

high-shear stirring, ultrasound generators

Problems Creaming, flocculation and sedimentation is observed.

No creaming, flocculation and sedimentation is observed.

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• DIFFERENCE BETWEEN MACROEMULSION & NANOEMULSION

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Method of preparation1)High pressure homoginization:• By high pressure homoginizer or piston homoginizer which

produce NEs of exrtemly low particle size upto 1 nm.2)Microfluidization:• This make use of microfluidizer.• This device use high pressure positive displacement

pump(500-20000 psi) which force the product through the interaction chamber which consist of small micro channel.

• Product flow throgh the micro channel on to the impigment resulting in the formation of nano size droplet.

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CHARACTERIZATION OF NANOPARTICALS • Nano-emulsions are not thermodynamically stable, and because of

that, their characteristics will depend on preparation method. Here some parameters are discussed which should be analysed at the time of preparation of nanoemulsion.

• Phase Behavior Study

This study is necessary in characterization and optimization of ingredients. This is used in case of NE formulation prepared by phase inversion temperature method and self-emulsification method.

• Particle Size Analysis

Generally Dynamic Light Scattering(DLS) method are used.• Surface Charge Measurement

Surface zeta potential of NE droplets should be measured with the help of mini electrode to predict the surface properties of NEs. 

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• Transmission Electron MicroscopyTEM is used to observe the morphology in Nano-emulsion.

• ViscosityViscosity should be measured to ensure the better delivery of the formulation.

• Morphology & structureMorphology and structure of nanoemulsion can be studied using TEM. The study of globule shape and surface can be observed by TEM. To perform TEM observations, a drop of the nanoemulsion is deposited on the holey film grid and observed after drying.

Contd…

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Advantages of nanoemulsion • Nanoemulsions have a much higher surface area and free energy than

macroemulsions that make them an effective transport system. • Are metastable and can be diluted with water without changing

droplet size distribution. • Do not show problems of inherent creaming, flocculation, coalescence

and sedimentation which are commonly with marcoemulsions . • Can be formulated in variety of formulations such as foams, creams,

liquids and sprays. • Are non-toxic and non-irritant, hence, can be easily applied to skin and

mucous membranes. • Since nanoemulsions are formulated with surfactants, which are

approved for human consumption (generally regarded as safe), they can be taken by enteric route.

• Do not damage healthy human and animal cells, hence, are suitable for human and veterinary therapeutic purposes.

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Limitations Of Nanoemulsions

• The manufacturing of nanoemulsion formulation is an expensive process because size reduction of 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 microfluidization and ultrasonication (manufacturing process) required high amount of financial support.

• Stability of nanoemulsion is quite unacceptable and creates a big problem during the storage of formulation for longer time of period.

• Ostwald ripening is the main factor associated with unacceptability of nanoemulsion formulations. This is due to high rate of curvature of small droplets show greater solubility as compared to large drop with a low radius of curvature.

Disadvantages

• Nanoemulsions show poor drug loading capacity.

• Show drug expulsion after polymeric transition during storage.

• Relatively high water content of the dispersions (70-99.9%) is observed in nanoemulsion.

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Nanoemulsions - Drug DeliveryAdvantages Increase drug loading Enhance drug solubility Bioavailability Controlled drug delivery Protection of drug

Disadvantages Expensive process Stability Solubility Lack of understanding of interfacial chemistry More proofs about more benefits compared to classical macroemulsions

J. Phys. Chem. C 2008, 112 (33), 12669-12676.

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Formulation additives

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A Typical Formulation

Emulsifiers and coemulsifiers(1)emulsifiers natural ones: acacia, mucilage tragacanth,

gelatine, albumin, casein, lecithin, SP, cholesterol

synthetic ones: Tweens, poloxamers, Spans(2)coemulsifiers: n-butanol, ethylene glycol,

ethanol, propylene glycol, glycerin, poly-glyceride

Preparation of nanoemulsion(1)formation comditionsEmulsifiers : 20-30% of oil adding coemulsifiers: adjust the HLB value, insert the interfacial film, form

complex aggregate film, enhance the degree of rigidity and flexibility, further reduce the interfacial tension, increase the stability of nanoemulsions

(2)steps of preparation determine the formulation: ternary phase diagram (p358) note: keep constant temperature mixing according to the determined ratios

preparation of subnanoemulsion key instrument: high pressure emulsifier impact factors stabilizer: oleic acid enhance the strength of interfacial film increase the solubility of drug increase the absolute value of ξ potential complex emulsifiers: lecithin+poloxamer

Method of preparation

High pressure homogeniserMicrofluidizationPhase inversion temperature technique

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Preparation of nanoemulsions

1. High pressure homogenization • High pressure homogenization technique was initially used

for the production of solid lipid nanodispersions. • This technique makes use of high pressure

homogenizer/piston homogenizer to produce nanoemulsions of extremely low particle size (up to 1nm).

• There are two methods in high pressure homogenization, i.e. hot homogenization and cold homogenization.

• Higher stirring rates did not significantly change the particle size, but slightly improved the polydispersity index.

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High -pressure homogenization

• This technique makes use of high-pressure homogenizer/piston homogenizer to produce NEs of extremely low particle size (up to 1nm)

2. Micro fluidization is a patented mixing technology, which makes use of a device called micro fluidizer.

• This device uses a high-pressure positive displacement pump (500-20000 per square inch), which forces the product through the interaction chamber, which consists of small channels called “micro-channels”.

• The product flows through the micro-channels which resulting in very fine particles of sub-Micron range.

• Micro fluidization The two solutions (aqueous phase and oily phase) are combination together and processed in an inline homogenizer to yield a coarse emulsion.

• The coarse emulsion is into a micro fluidizer where it is further processed to obtain a stable nanoemulsion.

• The coarse emulsion is passed through the interaction chamber of the micro fluidizer repeatedly until desired particle size is obtained.

• The bulk emulsion is then filtered through a filter under nitrogen to remove large droplets resulting in a uniform nanoemulsion .

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MICROFLUIDIZATION: It involves the use of device that is micro fluidizer It uses high-pressure positive displacement pump

of (500-20000)psi, which forces the product through the interaction chamber, which consists of small channels called “micro channels”.

The product flows through the micro channels on to an impingement area resulting in very fine particles of submicron range. The two solutions (aq. Phase and oily phase) are combined together and processed to obtain a stable nanoemulsion.

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Microfluidization

www.ttlindia.com/images/microfluidics1.jpg

3. Phase inversion temperature technique: It involves 2 steps• STEP 1 result in the formation of a suitable system. This

procedure consists of magnetic stirring of all the components-the ternary system- prepared in suitable proportions of salt water(salt and water),non-ionic surfactant and oil, with a rise from room temperature to 85 o c at a rate of 4 o c/minute.

• A progressive cooling from 85 o c to 60 o c at a rate of 4 o c/minute is performed.

• Three temperature cycles (85-60-85-60-85 o c) are applied to reach the inversion process.

• STEP 2 is an irreversible shock induced by dilution with cold water to the mixture maintained at the previously at a defined temperature.

• This fast cooling dilution process with cold distilled water leads to nano objects. Afterwards, a slow magnetic stirring is applied to the suspension for 5 minutes. 37

Quality evaluation size and size distribution drug concentration stability

Nanoemulsions – Characterization/Evaluation

Morphology

Size, PDI

Viscosity

Skin permeation

Surface characterization

Refractive Index

Characterization of NEs:• Transmission eletron microscopy• Drolet size analysis• Viscosity• Refractive index• Skin irritation test• Thermodynamic stability study• Surface characteristics

04/22/2023 Shakti Suthar

Characterization of nanoemulsion

• Preliminary characterization such as creaming, cracking or phase separation can be observed visually for over 48 hours time period in undisturbed standing conditions.

• Morphology and structure Morphology and structure of nanoemulsion can be studied using TEM.

• The study of globule shape and surface can be observed by TEM.

• To perform TEM observations, a drop of the nanoemulsion is deposited on the holey film grid and observed after drying.

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Nanoemulsion droplet size analysis

• 0.1ml of nanoemulsion is dispersed in 50 ml (500 times dilution) of double distilled water in a volumetric flack and gently mixed by inverting the flask.

• Dynamic light scattering can be performed at 25 o C, using helium-neon laser having particular wavelength at an angle of 90 o on a digital correlate.

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• Refractive index The refractive index of nanoemulsion formulation is determined using abbe type refractometer.

• Viscosity determination The viscosity of the nanoemulsion can be measured using Brookfield digital rheometer temperature at 25 o C.

• The surface charge can be determined by measuring the zeta potential of the preparations . This is done by using an aqueous phase containing NaCl and HCl and sodium hydroxide to adjust the conductivity and the pH, respectively. Zeta potential characterizes the surface charge of particle and, thus, it gives information about repulsive forces between particles and droplets. To obtain stable nanoemulsions by preventing flocculation and coalescence of the nano-droplets, zeta potential should usually reach a value about 30mV.

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Invitro skin permeation studies

• Franz diffusion cell44

• Stability of nanoemulsion: A stability study of the nanoemulsion can be performed as per ICH guidelines. The samples were kept at fore different conditions of temperature and relative humidity (%RH) as 40 o C/75% RH, 30 o C/65% RH, 25 o C/60% RH and refrigeration condition. The stability is observed over a period of 3 months. The samples are evaluated for particle size, viscosity, drug content, surface charge, drug release, etc. Surface charge .

• Freeze-thaw cycling test can be carried out at five alternative cycles each of 24 hour storage at ambient and freezing conditions, high speed centrifugation at various speeds starting from 2000 up to 5000 rpm each for 10 minutes.

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Nanoemulsions - Applications

Agriculture

Cleaning products

Cosmetic

Pharmaceutic

Biomedical

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APPLICATIONS OF NANO-EMULSIONS

The compositional flexibility of nanoemulsions offers a wide range of applications.

The incorporation of fluorescent dyes and other molecules into nanoemulsions makes the interesting probes for exploring properties of living cells and for drug delivery.

Nanoemulsion vaccine could inactivate and kill the virus and then subsequently induce immunity to 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 for cellular uptake and dispersal. Both oil-soluble and water-

soluble drug molecules can be incorporated into the nanodroplets of direct and inverse nanoemulsions for potential pharmaceutical uses.

In the printing and data storage industries, one may imagine the resolution of droplets.

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In the personal care and food industries, nanoemulsions may provide interesting alternatives as pleasantly transparent and soft solids that possess plastic-like rheological properties. While being appealing from an optical and rheological point of view, nanoemulsion also can deliver moisturizers to the skin quite efficiently and also block ultraviolet light without leaving a white residue.

The small size of the nano droplets will likely increase transport efficiency of any active drugs or other molecules inside the droplets across biological membranes, including the skin. Thus, nanoemulsions may have significant applications in medical patches.

High-throughput production methodologies make nanoemulsions a realistic commercial-scale alternative for diverse areas, including lotions and pharmaceuticals.

Contd…

• Applications Of Nanoemulsion • Use of nanoemulsions in cosmetics Nanoemulsions

as potential vehicles for the controlled delivery of cosmetics and for the optimized dispersion of active ingredients, in particular, skin layers.

• Due to their lipophilic interior, they are more suitable for the transport of lipophilic compounds than liposomes.

• Similar to liposomes, they support the skin penetration of active ingredients and thus, increase their concentration in the skin.

• Antimicrobial nanoemulsions49

• Prophylactic in bio-terrorism attack • Nanoemulsions as mucosal vaccine • Nanoemulsions as non-toxic disinfectant cleaner • Nanoemulsions in cell culture technology • Nanoemulsions in cancer therapy and in targeted

drug delivery • Nanoemulsions in the treatment of various disease

conditions • Nanoemulsions formulations for imported oral

delivery of poorly soluble drugs • Nanoemulsions as vehicle for transdermal delivery

SNEDDS(self nano-emulsifying drug delivery systems)50

Patented Nanoemulsions :• Some important patents related to nanoemulsions : Patent name: Method of

Preventing and Treating Microbial Infections.• Assignee: NanoBio Corporation (US). • US Patent number:6,506,803. • Patent name: nanoemulsions based on phosphoric acid fatty acid esters and its uses

in the cosmetics, dermatological, pharmaceutical, and/or ophthalmological fields. Assignee: L'Oreal (Paris, FR).

• US Patent number:6,274,150. Patent name: nanoemulsions based on ethylene oxide and propylene oxide block copolymers and its uses in the cosmetics, dermatological and/or ophthalmological fields.

• Assignee: L'Oreal (Paris, FR). US Patent number: 6,464,990. nanoemulsions of 5-aminolevulinic acid (6,559,183).

• Assignee: ASAT AG Applied Science and Technology (Zug, CH). PCT number: PCT/ EP99/08711. nanoemulsions of poorly soluble pharmaceutical active ingredients and methods of making the same. Patent no.: WO/2007/103294

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Marketed formulations

• Some commercially available nanoemulsion formulations are:

• Propofol (Dipivan); • Vitamins A,D,E,K (Vitalipid).

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Marketed products:

Drug Brand Manufacturer Indication

Propofol Diprivan Astra zeneca Anesthatic

Dexamethazone Limethasonn Mitsubishi pharmaceutical, Japan

Steroids

Palmitate alprostadil

Liple Mitsubishi pharmaceutical, Japan

Vasodilator

Flubriprofen axetil Ropion Kaken pharmaceutical, Japan

NSAIDS

Vitamines A,D,E,K Vitalipid Fresenius kabi,Europe

Parenteral nutrition

Commercially Available Nanoemulsions

Conclusions

Nanoemulsions are receiving increasing attention as drug carrier

Applicable for almost all routes of delivery

Wide range of molecules can be loaded

New technology could be developed to overcome the poor absorption and miscibility of some phytopharmaceutical

Conclusion cont.

• Nanoemulsion formulations offer several advantages for not only the delivery of drugs, but biological or diagnostic agents also.

• Nanoemulsions can be formulated in a variety of formulations such as foams, creams, liquids and sprays.

• Recently, nanoemulsions have been used in several drug delivery applications such as targeted drug delivery, mucosal vaccines, In cell culture technology, anti-cancer, anti-HIV therapy and diagnostic agents.

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