Nanoemulsions an Emerging Trend a Review

IJPRD, 2011; Vol 4(06): August-2012 (137 152) International Standard Serial Number 0974 9446

Available online on www.ijprd.com

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NANOEMULSIONS AN EMERGING TREND: A REVIEW

R.B.Desi reddy*1,

Ch.T. Lalitha kumari1, G.Naga sowjanya

1, S.L.Sindhuri

1, P.Bandhavi

1

1 Nalanda Institute of Pharmaceutical sciences, Kantepudi, Sattenapalli, India

ABSTRACT

Nanoemulsions are one of the emerging trends in targeted &

controlled drug delivery systems . Nanoemulsions are clear,

thermodynamically stable, isotropic liquid mixtures of oil,

water,surfactant and co-surfactant. These are oil-in-water (o/w)

type of emulsions with the average droplet size ranging from 5nm

to 100 nm. Reduction in droplet size to nanoscale leads to change

in physical properties such as optical transparency & unusual

elastic behavior. Nanoemulsions have widespread applications in

different fields such as pharmaceutics, food technology .

Nanoemulsion offers a promising vehicle for increasing the

aqueous solubility of poorly water-soluble drugs considerably,

which is usually necessary for parenteral application.

Nanoemulsions have many advantages, for instance, enhance

drug solubility, perfect thermodynamic stability, ease of

manufacturing and permeation over conventional formulations

that convert them to important drug delivery systems.

Nanoemulsion can improve transdermal delivery of lipophilic and

hydrophilic compound with different mechanisms. The design &

development of nanoemulsions aimed at controlling or improving

required bioavailability levels of therapeutic agents.. This review

mainly discussed about the importance of nanoemulsions over

other dosage forms, preparation methods ,current state of

nanoemulsions in the delivery of drugs and other bioactives and

characterization of nanoemulsions, applications.

KEYWORDS : Nanoemulsion, parenteral, Preparation,

Characterization, Application in Drug Delivery.

Correspondence to Author

R.B.Desi reddy

Nalanda Institute of Pharmaceutical

sciences, Kantepudi, Sattenapalli,

India

Email: [email protected]

International Journal of Pharmaceutical Research & Development ISSN: 0974 9446


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INTRODUCTION

Nanoemulsions are non-toxic lipid droplets with a

few hundred nanometers in diameter and made

from surfactants approved for human consumption

and common food substances that are 'Generally

Recognized as Safe' (GRAS) by the FDA. These

emulsions are easily produced in large quantities

by mixing a water-immiscible oil phase into an

aqueous phase with a high-stress, mechanical

extrusion process that is available worldwide. This

process yields a uniform population of droplet

particles that are stable for years even at elevated

temperatures.

The various nanoformulations are : Nanoemulsions

(NE) (submicron sized emulsions), nanosuspensions

(submicron sized suspensions), nanospheres (drug

nanoparticles in polymer matrix), nanotubes

(sequence of nanoscale C60 atoms arranged in a

long thin cylindrical structure), nanoshells

(concentric sphere nanoparticles consisting of a

dielectric core and a metal shell), nanocapsules

(encapsulated drug nanoparticles), lipid

nanoparticles (lipid monolayer enclosing a solid

lipid core) and dendrimers (nanoscale three-

dimensional macromolecules of polymer).

Nanoemulsions are submicron sized emulsions that

are under extensive investigation as drug carriers

for improving the delivery of therapeutic agents.

The small size of the particles in these kinds of

delivery systems (r < 100 nm) means that they have

a number of potential benefits for certain

applications: enhanced long-term stability, high

optical clarity and increased bioavailability.

Nanoemulsions are increasingly being utilized in

food and pharmaceutical industries to encapsulate,

protect, and deliver lipophilic bioactive

components.

Nanoemulsions are formed when the interfacial

tension at the oil/water interface is brought to a

very low level and the interfacial layer is kept

highly flexible and fluid. These two conditions are

usually met by a careful and precise choice of the

components and of their respective proportions

and by the use of a co-surfactant which brings

flexibility to the oil/water interface. These

conditions lead to a thermodynamically optimised

structure, which is stable as opposed to

conventional emulsions and does not require high

input of energy (i.e. through agitation) to be

formed.

Components of Nano Emulsion

The three main components of Nanoemulsions are

as follows:

1. Oil (Table 1)

2. Surfactant/Co-surfactant (Table 2)

3. Aqueous phase (Table 3)

Table 1. List of oils used in nanoemulsions

Name Chemical Name

Captex 355 Glyceryl

Tricaorylate/Caprate

Captex 200 Propylene

Dicaprylate/Dicaprate Glycol

Captex 8000 Glyceryl Tricaprylate

(Tricaprylin)

Witepsol 90:10 % w/w c12 Glyceride

tri: diesters

Myritol 318 c8/c10 triglycerides

Isopropyl myristate Myristic acid isopropyl ester

Table 2. List of Surfactant used in nanoemulsions

S.No Solubilizing agents, surfactants, emulsifying

agents adsorption enhancers

1 Capryol 90

2 Gelucire 44/14, 50/13

3 Cremophor RH 40

4 Imwitor 191, 308(1), 380, 742, 780 K, 928,

988

5 Labrafil M 1944 CS, M 2125 CS

6 Lauroglycol 90

7 PEG MW > 4000

8 Plurol Oleique CC 497

9 Poloxamer 124 and 188

10 Softigen 701, 767

11 Tagat TO

12 Tween 80



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Table 3. List of Co-Surfactant used in

nanoemulsions

Microemulsions are used for controlled release and

targeted delivery of different pharmaceutics

agents. For instance, microemulsions were used to

deliver oligonucleotides (small fragments of DNA)

specifically to ovarian cancer cells. In contrast to

microemulsions, Nanoemulsions consist in very

fine oil-in-water dispersions, having droplets

diameter smaller than 100 nm. Compared to

microemulsions, they are in a metastable state and

their structure depends on the history of the

system. Nanoemulsions are very fragile systems.

The nanoemulsions can find applications in skin

care due to their good sensorial properties (rapid

penetration, merging textures) and their

biophysical properties (especially their hydrating

power). This technology has a great advantage over

the other dosage forms that the formulation can be

delivered by various routes including oral , ocular

and transdermal .

Nanoemulsions have broad-spectrum

antimicrobial activity against bacteria, enveloped

viruses, fungi, protozoa and spores, due to their

ability to lyse these organisms. In contrast, studies

of nanoemulsions in animals have shown these

compounds to be very well tolerated on the skin

and mucous membranes. These attributes provide

a broad therapeutic index when the nanoemulsions

are used in humans as topical treatments for

disorders including Herpes Labialis, cutaneous

fungal infections, vaginitis, and respiratory

infections. This material holds such unique promise

and low risk that the FDA allowed Phase II Clinical

Trials for the treatment of Herpes Labialis with

Good Manufacturing Procedures (GMP)

nanoemulsion to be conducted.

A B

A:Microemulsions,B:Nanoemulsions

Preparation methods of Nanoemulsions

Several methods have been suggested for the

preparation of nanoemulsion. The basic objectives

of the nanoemulsion preparation is to achieve the

droplet size range of 100-600 nm and another is to

provide the stability condition. Formation of

nanoemulsion system required a high amount of

energy. This energy can be provided either by

mechanical equipment or the chemical potential

inherent within the component . Here some

methods are discussed which are freely used for

the nanoemulsion preparation.

1. Phase inversion method :

In this method fine dispersion is obtained by

chemical energy resulting of phase transitions

taking place through emulsification path. The

adequate phase transitions are produced by

varying the composition at constant temperature

or by varying the temperature at constant

composition. Phase inversion temperature (PIT)

method was introduced by Shinoda et al. based on

the changes of solubility of polyoxyethylene type

surfactant with temperature. This surfactant

becomes lipophilic with increase in temperature

due to dehydration of polymer chain. But at low

temperature, the surfactant monolayer has a large

positive spontaneous curvature forming oil-swollen

S.No Co Surfactant

1 TranscutolP

2 Glycerin,Ethyle

ne glycol

3 Propylene

glycol

4 Ethanol

5 Propanol



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micellar solution phase .

2.Sonication method:

Sonication method is another best way to prepare

nanoemulsion. In this method the droplet size of

conventional emulsion are reduced with the help

of sonication mechanism. This method is not

suitable for large batches, only small batches of

nanoemulsion can be prepared by this method .

Sonication method

3.Highpressurehomogenizer:

This method is performed by applying a high

pressure over the system having oil phase, aqueous

phase and surfactant or co-surfactant. The

pressure is applied with the help of a special

equipment know as homogenizer. There are some

problems which are associated with homogenizer

such as poor productivity, 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 be prepared and cream

nanoemulsion of high viscosity or hardness with a

mean droplet diameter lower than 200 nm cannot

be prepared .

4.Microfluidization:

Microfluidization is a patented mixing technology,

which makes use of a device called microfluidizer.

This device uses a high-pressure positive

displacement pump (500-20000 psi), which forces

the product through the interaction

chamber,consisting of small channels called

"microchannels." The product flows through the

microchannels on to an impingement area resulting

in very fine particles of submicron range. The two

solutions (aqueous phase and oily phase) are

combined together and processed in an inline

homogenizer to yield a coarse emulsion. The

coarse emulsion is into a microfluidizer where it is

further processed to obtain a stable nanoemulsion.

The coarse emulsion is passed through the

interaction chamber of the microfluidizer

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.

Production With High-Amplitude Ultrasound

High-amplitude ultrasound is a viable alternative to

high-pressure homogenization. Intense shear

forces necessary for the nanoemulsification are

generated by ultrasonic cavitation, which produces

violently and asymmetrically imploding vacuum

bubbles and causes micro-jets that disperse and

break up particles down to the nanometer scale.

Known for many decades, this effect has been

extensively studied and successfully used in small-

scale production of pharmaceutical nanoemulsions

and liposomes. However, prior to the introduction

of Barbell Horn Ultrasonic Technology (BHUT),

ultrasonic liquid processors could not effectively

compete with high-pressure homogenizers in this

market because they were not able to generate

sufficiently high-amplitude (70 - 120 microns)

ultrasonic vibrations on the industrial scale.

Conventional high-power ultrasonic technology

inherently forces all processes to run either at a

small scale and high amplitude or a large scale and

low amplitude, not allowing for the possibility of

implementing high amplitudes on industrial scale.

Thus, despite its potential, the ultrasonic method

has mainly been restricted to laboratory

investigations.

Ultrasonic Technology:



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Industrial Sonomechanics, LLC, (ISM) has

successfully overcome the aforementioned

limitation by developing BHUT, which permits

constructing industrial ultrasonic systems able to

operate at extremely high ultrasonic amplitudes

(up to about 200 microns). The output tip areas of

the incorporated Barbell horns and the resulting

productivity rates of the systems are more than 10

times higher than those of any conventional

ultrasonic device operating at high amplitudes.

ISM's Barbell horn-based high-amplitude industrial

ultrasonic processors can be used for the

commercial-scale production of the highest-quality

nanoemulsions and liposomes, while offering many

advantages over high-pressure homogenizers.

These include significantly lower equipment costs,

smaller number of wetted parts (easier cleaning,

less wear and simpler servicing), no need to use a

separate rotor-stator high-shear mixer to prepare a

preliminary emulsion, as well as a much more

practicable aseptic processing. In addition, it is

much easier to create an ultrasonic system design

that eliminates the need for multiple passes of the

liquid through the system, which has not been

possible with any high-pressure homogenizer.

ISM offers directly scalable bench-top and

industrial ultrasonic processors for the

manufacture of high-quality pharmaceutical

nanoemulsions and liposomes. Our patented

ultrasonic devices utilize high-gain Barbell horns,

which make it possible to reproduce any high-

amplitude laboratory-optimized process in a

commercial production setting. These flow-through

processors provide extremely high ultrasonic

amplitudes and very uniform exposure patterns,

ensuring that all treated liquid is exposed to

tremendous ultrasonic cavitation-induced shear

forces and that no part of the liquid is able to

bypass the active cavitation zone in the reactor.

Each ISMs industrial ultrasonic processor

incorporates a calibrated amplitude sensor and is

able to display and record ultrasonic amplitudes in

microns peak to peak during operation.

Characterization of nanoparticles

Nanoemulsions are not thermodynamically stable,

because of that their characteristics will depend on

preparation method. Here some parameters are

discussed which should be analyzed at the time of

preparation of nanoemulsion .

(i) Phase behaviour study: This study is a

characterization and optimization of ingredients

(surfactant, oil phase and aqueous phase).

Generally the study is necessary in case of

nanoemulsion formulation prepared by phase

inversion temperature method and self

emulsification method in order to determine the

phase of nanoemulsion and dispersibility. Study is

done by placing the different ingredients of

nanoemulsion by varying the concentration in glass

ampules and thoroughly homogenized at a certain

temperature for a time until equilibrium.

Anisotropic phase can be identified by polarized

light.

(ii) Particle Size Analysis: Formulated

nanoemulsion should be analyzed for their

hydrodynamic particle size and particle size

distribution. Generally in case of nanoemulsion

dynamic light scattering (DLS) method are used for

the measurement of particles and further particle

size distribution.

ISMs Ultrasonic Processor



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(iii) Surface charge measurement: Surface zeta

potential of nanoemulsion droplets will be

measured with the help of mini electrode to

predict the surface properties of nanoemulsion.

(iv) Transmission Electron Microscopy (TEM): This

method is used to observe the morphology in the

nanoemulsion.

(v) Drug content: This method is used to determine

the amount of drug contained in the formulation.

Various methods (especially Western Blot method)

are used in this order.

(vi) Viscosity: Viscosity will be measured to ensure

the better delivery of the formulation.

Stability of Nanoemulsions :

Stability of a dosage form refers to the chemical

and physical integrity of the dosage unit and when

appropriate, the ability of the dosage unit to

maintain protection against microbiological

contamination . Stability of drug product is one of

the problems associated with the development of

emulsions, microemulsions and nanoemulsions.

Nanoemulsions have been known to enhance the

physical as well as chemical stability of drugs .

Stability studies are performed on

nanoemulsions by storing them at refrigerator and

room temperatures over a number of months. The

viscosity, refractive index and droplet size are

determined during this period of storage.

Insignificant changes in these parameters indicate

formulation stability. Accelerated stability studies

can also performed. In this instance, nanoemulsion

formulation are kept at accelerated temperatures

and samples withdrawn at regular intervals and

analyzed for drug content by stability indicating

HPLC methods . The amount of drug degraded and

remaining in nanoemulsion formulation is

determined at each time interval.

Morphology of Nanoemulsions

The morphology of nanoemulsions can be

determined by transmission electron microscopy

(TEM) and scanning electron microscopy (SEM).

SEM gives a three-dimensional image of the

globules . The samples are examined at suitable

accelerating voltage, usually 20 kV, at different

magnifications. A good analysis of surface

morphology of disperse phase in the formulation is

obtained through SEM. Image analysis software,

(e.g., Leica Im- aging systems, Cambridge, UK), may

be employed to obtain an automatic analysis result

of the shape and surface morphology .

ApplicationsOfNanoemulsions:

Parenteral Delivery:

Parenteral administration (especially via the

intravenous route) of drugs with limited solubility is

a major problem in industry because of the

extremely low amount of drug actually delivered to

a targeted site. Nanoemulsion formulations have

distinct advantages over macroemulsion systems

when delivered parenterally because of the fine

particle size. Nanoemulsion is cleared more slowly

than the coarse particle emulsion and , therefore,

have a longer residence time in the body. Both

O/W and W/O nanoemulsions can be used for

parenteral delivery. The literature contains the

details of the many nanoemulsion systems, few of

these can be used for the parenteral delivery

because the toxicity of the surfactant and

parenteral use. An alternative approach was taken

by Von Corsewant and Thoren in which C3-C4

alcohols were replaced with parenterally

acceptable co-surfactants, polyethylene glycol

(400) / polyethylene glycol (660) 12-

hydroxystearate / ethanol, while maintaining a

flexible surfactant film and spontaneous curvature

near zero to obtain and almost balanced middle

phase nanoemulsion. The middle phase structure

was preferred in this application, because it has

been able to incorporate large volumes of oil and

water with a minimal concentration of surfactant.

Oral Delivery:



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Nanoemulsion formulations offer the several

benefits over conventional oral formulation for oral

administration including increased absorption,

improved clinical potency and decreased drug

toxicity. Therefore, Nanoemulsion have been

reported to be ideal delivery of drugs such as

steroids, hormones, diuretic and antibiotics.

Pharmaceutical drugs of peptides and proteins are

highly potent and specific in their physiological

functions. However, most are difficult to

administer orally. With on oral bioavailability in

conventional (i.e. non-Nanoemulsion based)

formulation of less than 10%, they are usually not

therapeutically active by oral administration.

Because of their low oral bioavailability, most

protein drugs are only available as parenteral

formulations. However, peptide drugs have an

extremely short biological half life when

administered parenterally, so require multiple

dosing. A Nanoemulsion formulation of

cyclosporine, named Neoral has been introduced

to replace Sandimmune, a crude oil-in-water

emulsion of cyclosporine formulation. Neoral is

formulated with a finer dispersion, giving it a more

rapid and predictable absorption and less inter and

intra patient variability.

Topical Delivery:

Nanoemulsion formulation provides a rapid

penetration of active ingredients through skin due

to the large surface area of droplets. Even

sometimes it is found that nanoemulsion penetrate

easily through rough skin. This property of

nanoemulsion minimizes the additional utilization

of special penetration enhancer which is re-

sponsible for incompatibility of formulation.

Topical administration of drugs can have

advantages over other methods for several

reasons, one of which is the avoidance of hepatic

first pass metabolism of the drug and related

toxicity effects. Another is the direct delivery and

targetability of the drug to affected area of the skin

or eyes. Both O/W and W/O Nanoemulsions have

been evaluated in a hairless mouse model for the

delivery of prostaglandin E1. The Nanoemulsions

were based on oleic acid or Gelucire 44/14 as the

oil phase and were stabilized by a mixture of

Labrasol (C8 and C10 polyglycolysed glycerides)

and Plurol Oleique CC 497 as surfactant. Although

enhanced delivery rates were observed in the case

of the O/W Nanoemulsion, the authors concluded

that the penetration rates were inadequate for

practical use from either system. The use of

lecithin/IPP/water Nanoemulsion for the

transdermal transport of indomethacin and

diclofenac has also been reported. Fourier

transform infra red (FTIR) spectroscopy and

differential scanning calorimetry (DSC) showed the

IPP organogel had disrupted the lipid organisation

in human stratum corneum after a 1 day

incubation. The transdermal delivery of the

hydrophilic drug diphenhydramine hydrochloride

from a W/O Nanoemulsion into excised human skin

have also been investigated. The formulation was

based on combinations of Tween 80 and Span 20

with IPM. However two additional formulations

were tested containing cholesterol and oleic acid,

respectively. Cholesterol increased drug

penetration whereas oleic acid had no measurable

effect, but the authors clearly demonstrated that

penetration characteristics can be modulated by

compositional selection.

Ocular and Pulmonary Delivery:

For the treatment of eye diseases, drugs are

essentially delivered topically. O/W Nanoemulsions

have been investigated for ocular administration,

to dissolve poorly soluble drugs, to increase

absorption and to attain prolong release profile.

The Nanoemulsions containing pilocarpine were

formulated using lecithin, propylene glycol and PEG

200 as co-surfactant and IPM as the oil phase. The

formulations were of low viscosity with a refractive

index lending to ophthalmologic applications. The

formation of a water-in-HFA propellent

Nanoemulsion stabilized by fluorocarbon non-ionic

surfactant and intended for pulmonary delivery has

been described.

Nanoemulsions in Biotechnology:



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Many enzymatic and biocatalytic reactions are

conducted in pure organic or aqua-organic media.

Biphasic media are also used for these types of

reactions. The use of pure apolar media causes the

denaturation of biocatalysts. The use of water-

proof media is relatively advantageous. Enzymes in

low water content display and have

Increased solubility in non-polar reactants.

Possibility of shifting thermodynamic

equilibria in favour of condensations.

Improvement of thermal stability of the

enzymes, enabling reactions to be carried

out at higher temperatures.

Many enzymes, including lipases, esterases,

dehydrogenases and oxidases often function in the

cells in microenvironments that are hydrophobic in

nature. In biological systems many enzymes

operate at the interface between hydrophobic and

hydrophilic domains and these usually interfaces

are stabilized by polar lipids and other natural

amphiphiles. Enzymatic catalysis in Nanoemulsions

has been used for a variety of reactions, such as

synthesis of esters, peptides and sugar acetals

transesterification; various hydrolysis reactions and

steroid transformation. The most widely used class

of enzymes in microemulsion-based reactions is of

lipase.

Nanoemulsions in vaccine development:

Nanoemulsions can be used as a mucosal vaccine

adjuvant. Nasal spray nanoemulsion vaccine fuses

with antigen and is then sprayed into a nostril.

Nanoemulsion droplets with antigen penetrate the

nasal mucosa. Diagram of nanoemulsion droplet

with antigen in its interface. Blue dots are antigen

present in emulsion. Antigen delivery by

nanoemulsion into nasal submucosa where fusion

with dendritic cells delivers the antigen to the

immune system. Dendritic cells can then transport

the antigen to other parts of the body to trigger the

desired immune response.

Antimicrobialnanoemulsions:

Antimicrobial NEs are oil-in-water droplets that

range from 200 to 600 nm. They are composed of

oil and water and are stabilized by surfactants and

alcohol. The NE has a broad-spectrum activity

against bacteria (e.g.E.coil, salmonella, S. aureus),

enveloped viruses (e.g. HIV, Herpes simplex), fungi

(e.g. Candida, Dermatophytes), and spores (e.g.

anthrax). The NE particles are thermodynamically

driven to fuse with lipid-containing organisms.

This fusion is enhanced by the electrostatic

attraction between the cationic charge of the

emulsion and the anionic charge on the pathogen.

When enough nanoparticles fuse with the

pathogens, they release part of the energy trapped

within the emulsion. Both the active ingredient and

the energy released destabilize the pathogen lipid

membrane, resulting in cell lysis and death. In the

case of spores, additional germination enhancers

are incorporated into the emulsion. Once initiation

of germination takes place, the germinating spores

become susceptible to the antimicrobial action of

the NE. A unique aspect of the NEs is their selective

toxicity to microbes at concentrations that are non-

irritating to skin or mucous membrane. The safety

margin of the NE is due to the low level of

detergent in each droplet, yet when acting in

concert, these droplets have sufficient energy and

surfactant to destabilize the targeted microbes

without damaging healthy cells. As a result, the NE

can achieve a level of topical antimicrobial activity

that has only been previously achieved by systemic

antibiotics.



145

Nanoemulsions as a mucosal vaccines .:

Nanoemulsions are being used to deliver either

recombinant proteins or inactivated organisms to a

mucosal surface to produce an immune response.

The first applications, an influenza vaccine and an

HIV vaccine, can proceed to clinical trials. The

Nanoemulsions causes proteins applied to the

mucosal surface to be adjuvanted and it facilitates

uptake by antigen-presenting cells. This results in a

significant systemic and mucosal immune response

that involves the production of specific IgG and IgA

antibody as well as cellular immunity. Initial work

in influenza has demonstrated that animals can be

protected against influenza after just a single

mucosal exposure to the virus mixed with the

emulsion. Research has also demonstrated that

animals exposed to recombinant gp120 in NE on

their nasal mucosa develop significant responses to

HIV, thus providing a basis to examine the use of

this material as an HIV vaccine. Additional research

is ongoing to complete the proof of concept in

animal trials for other vaccines including Hepatitis

B and anthrax A novel technique for vaccinating

against a variety of infectious diseases-using an oil-

based emulsion placed in the nose, rather than

needles-has proved able to produce a strong

immune response against smallpox and HIV in two

new studies.

Nanoemulsion as non-toxic disinfectant cleaner :

A breakthrough nontoxic disinfectant cleaner for

use in commercial markets that include healthcare,

hospitality, travel, food processing, and military

applications has been developed by EnviroSystems,

Inc. that kills tuberculosis and a wide spectrum of

viruses, bacteria and fungi in 5-10 min without any

of the hazards posed by other categories of

disinfectants. The product needs no warning labels.

It does not irritate eyes and can be absorbed

through the skin, inhaled, or swallowed without

harmful effects. The disinfectant formulation is

made up of nanospheres of oil droplets #106 mm

that are suspended in water to create a NE

requiring only miniscule amounts of the active

ingredient, PCMX (parachlorometaxylenol). The

nanospheres carry surface charges that efficiently

penetrate the surface charges on microorganisms'

membranes much like breaking through an electric

fence. Rather than "drowning" cells, the

formulation allows PCMX to target and penetrate

cell walls. As a result, PCMX is effective at

concentration levels 1-2 orders of magnitude lower

than those of other disinfectants; hence, there are

no toxic effects on people, animals, or the

environment. Other microbial disinfectants require

large doses of their respective active ingredients to

surround pathogen cell walls, which cause them to

disintegrate, fundamentally "drowning" them in

the disinfectant solution. The formulation is a

broad-spectrum disinfectant cleaner that can be

applied to any hard surface, including equipment,

counters, walls, fixtures, and floors. One product

can now take the place of many reducing product

inventories and saving valuable storage space.

Chemical disposal costs can be eliminated, and

disinfection and cleaning costs can be reduced. It is

marketed as a EcoTru (EnviroSystems, Inc.)

Nanoemulsions in cell culture technology

Cell cultures are used for in vitro assays or to

produce biological compounds, such as antibodies

or recombinant proteins. To optimize cell growth,

the culture medium can be supplemented with a

number of defined molecules or with blood serum.

Up to now, it has been very difficult to supplement

the media with oil-soluble substances that are

available to the cells, and only small amounts of

these lipophilic compounds could be absorbed by

the cells. NEs are a new method for the delivery of

oil-soluble substances to mammalian cell cultures.

The delivery system is based on a NE, which is

stabilized by phospholipids. These NEs are

transparent and can be passed through 0.1 mm

filters for sterilization. NE droplets are easily taken

up by the cells. The encapsulated oil-soluble

substances therefore have a high bioavailability to

cells in culture. The advantages of using NEs in cell

culture technology are better uptake of oil-soluble

supplements in cell cultures; improve growth and

vitality of cultured cells, and allowance of toxicity

studies of oil-soluble drugs in cell cultures.



146

Nanoemulsion in cancer therapy and in targeted

drug delivery :

It is also reported that nanoemulsion may be used

for the target delivery of active ingredient

especially in cancer therapy.The effects of the

formulation and particle composition of gadolinium

(Gd)-containing lipid NE (Gd-nanoLE) on the

biodistribution of Gd after its intravenous (IV)

injection in D1-179 melanoma-bearing hamsters

were evaluated for its application in cancer

neutron-capture therapy. Biodistribution data

revealed that Brij 700 and HCO-60 prolonged the

retention of Gd in the blood and enhanced its

accumulation in tumors. Among the core

components employed, soybean oil yielded the

highest Gd concentration in the blood and tumor,

and the lowest in the liver and spleen. When each

Gd-nanoLE was IV injected once or twice at a 24-h

interval, the Gd concentration in the tumor

correlated well with the total dose of Gd, and it

reached a maximum of a 189 mg/g wet tumor. This

maximum Gd level was greater than the limit

required for significantly suppressing tumor growth

in neutron-capture therapy. In order to achieve

penetration of Paclitaxel (PCL) into deeper skin

layers while minimizing the systemic escape, a NE

(NE) was formulated and its in

vivo pharmacokinetic performance was evaluated.

Further, the same formulation was explored for

peroral bioavailability enhancement of PCL. Upon

dermal application, the drug was predominantly

localized in deeper skin layers, with minimal

systemic escape. This has amounted to an absolute

bioavailability of 70.62%. Inhibition of P-

glycoprotein efflux by D-tocopheryl

polyethyleneglycol 1000 succinate and labrasol

would have contributed to the enhanced peroral

bioavailability of PCL. This investigation provides

direct evidence on the localization of high-

molecular-weight, lipophilic drug, PCL, in dermis.

Further, the NE formulation has enhanced the

peroral bioavailability significantly to more than

70%. The developed NE formulation was safe and

effective for both.

Camptothecin is a topoisomerase I inhibitor that

acts against a broad spectrum of cancers. However,

its clinical application is limited by its insolubility,

instability, and toxicity. The aim of the present

study was to develop acoustically active NEs for

camptothecin encapsulation to circumvent these

delivery problems. The NEs were prepared using

liquid perfluorocarbons and coconut oil as the

cores of the inner phase. These NEs were stabilized

by phospholipids and/or Pluronic F68 (PF68). The

NEs were prepared at high drug loading of

approximately 100% with a mean droplet diameter

of 220-420 nm. Camptothecin in these systems

showed retarded drug release. Camptothecin in

NEs with a lower oil concentration exhibited

cytotoxicity against melanomas and ovarian cancer

cells. Confocal laser scanning microscopy

confirmed NE uptake into cells. Using a 1 MHz

ultrasound, an increased release of camptothecin

from the system with lower oil concentration could

be established, illustrating a drug-targeting effect.

The advantages of formulating various lipophilic

anti-cancer drugs in submicron O/W emulsion are

obvious. The oil phase of the emulsion systems can

act as a solubilizer for the lipophilic compound.

Therefore, solubility of lipophilic drugs can be

significantly enhanced in an emulsion system,

leading to smaller administration volumes

compared to an aqueous solution. In addition,

because lipophilic drugs are incorporated within

the innermost oil phase, they are sequestered from

direct contact with body fluids and tissues. Lipid

emulsions can minimize the pain associated with

intravenously administered drugs by exposing the

tissues to lower concentrations of the drug or by

avoiding a tissue-irritating vehicle. This has been

demonstrated with propofol, diazepam,

methohexital, clarithromycin, and etomidate.

Another study reported the formulation of filter

sterilizable emulsion formulation of paclitaxel using

-tocopherol as the oil phase and -

tocopherylpolyethyleneglycol-1000 succinate

(TGPS) and poloxamer 407 as emulsifiers. The

formulation exhibited better efficacy and was more



147

tolerable when studied in B16 melanoma tumor

model in mice.

Emulsion formulations also show promise in cancer

chemotherapy as vehicles for prolonging the drug

release after intramuscular and intratumoral

injection (W/O systems) and as a means of

enhancing the transport of anti-cancer drugs via

the lymphatic system.

The perfluorochemical Nanoemulsions (PFCE) have

opened interesting opportunities in cancer

therapy. It is suggested that fluorocarbon

emulsions might find a role in photodynamic

therapy, both as carriers for sensitizing dyes and to

maintain tissue oxygenation in hypoxic regions of

solid tumors. The high solubility of oxygen in

fluorocarbon emulsions maintains solution oxygen

tension, optimizing photo-oxidative damage. The

hydrophobic anti-cancer drugs can be delivered to

the tumor mass by dissolving them in a

hydrophobic core of the emulsion. Furthermore,

PFCE can be used as an adjuvant to radiation

therapy and/or chemotherapy in the treatment of

solid tumors.

The preclinical studies have shown very positive

effects with single dose and fractionated radiation

in several rodent solid tumor models. Many widely

used anticancer drugs, including anti-tumor

alkylating agents and doxorubicin, have shown

improved response by PFCE coadministration. Also,

local application of toxic doses of PFCEs resulted in

the necrosis of cancer cells. This is especially

promising in the treatment of cancers of the head

and neck regions that are currently difficult to

treat.

Nanoemulsion in the treatment of various other

disease conditions:

Pharmos' (US-based company) has developed the

nanoemulsion topical diclofenac cream as a

potential treatment for osteoarthritis (OA) pain.

Topical diclofenac is also being considered as

treatment for soft tissue injuries, sprains, and

strains. It is estimated that 20% of OA patients are

not receiving treatment, mainly due to

gastrointestinal side effects of oral NSAIDs and

cardiovascular risk of COX-2 inhibitors. A topical

NSAID offering adequate pain relief targeted to the

site of injury with an improved safety profile could

become a treatment alternative for these patients.

One of the unique characteristics of the

Nanoemulsion technology is the relatively high

percentage of total particle volume occupied by

the internal hydrophobic oil core of the droplets.

This provides high solubilization capacity for

lipophilic compounds compared to other lipoidal

vehicles such as liposomes. Viscosity-imparting

agents are used for nanoemulsion thickening to

produce creams with the desired semisolid

consistency for application to the skin. The skin

penetrative properties of the solvent-free NE

delivery technology and its low irritancy make this

novel topical nanovehicle a promising candidate for

effective transcutaneous delivery of lipophilic

drugs. A topical application of the nanotechnology

has already demonstrated excellent targeted

delivery of lipophilic drugs to muscle and joints in

animal models. Preclinical data using a paw edema

animal model showed enhanced anti-inflammatory

activity with NSAIDs encapsulated in nanoemulsion

creams compared to commercial formulations.

Pharmacokinetic studies using nanoemulsion

topical creams containing radiolabeled diclofenac

and ketoprofen were performed to assess drug

penetration through skin and to determine local

tissue (muscle and joint) and plasma levels of drugs

following topical administration. Compared to oral

administration, diclofenac and ketoprofen

administered via nanoemulsion topical creams

demonstrated 4- to 6-fold lower drug

concentration in plasma, 60-to 80-fold more drug

in muscle tissue, and about 9-fold more drug in

jointsThe NE technology consists of spheric oily

droplets (in the range of 100-200 nm) uniformly

dispersed in an aqueous medium. The emulsion

droplet size reduction is essential to generate drug

formulations with high stability. The NE technology

has been successfully applied in the formulation of

ophthalmic preparations showing improved drug

delivery and reduced ocular irritation in humans in



148

Phase I/II clinical studies.

Primaquine (PQ) is one of the most widely used

antimalarial and is the only available drug till date

to combat relapsing form of malaria especially in

case of Plasmodium vivax and Plasmodium ovale.

Primaquine acts specifically on the pre-erythrocytic

schizonts that are concentrated predominantly in

the liver and causes relapse after multiplication.

However, application of PQ in higher doses is

limited by severe tissue toxicity including

hematological and GI-related side effects that are

needed to be minimized. Lipid NE has been widely

explored for parenteral delivery of drugs.

Primaquine when incorporated into oral lipid NE

having a particle size in the range of 10-200 nm

showed effective antimalarial activity

against Plasmodium bergheii infection in Swiss

albino mice at a 25% lower dose level as compared

to conventional oral dose. Lipid NE of primaquine

exhibited improved oral bioavailability and was

taken up preferentially by the liver with drug

concentration higher at least by 45% as compared

to the plain drug.

Nanoemulsion formulations for improved oral

delivery of poorly soluble drugs :

NE formulations were developed to enhance oral

bioavailability of hydrophobic drugs. Paclitaxel was

selected as a model hydrophobic drug. The oil-in-

water (o/w) Nanoemulsions were made with pine

nut oil as the internal oil phase, egg lecithin as the

primary emulsifier, and water as the external

phase.

Stearylamine and deoxycholic acid were used to

impart positive and negative charge to the

emulsions,respectively.

Coenzyme Q10 (CoQ10), also known as

ubiquinone, is used for energy production within

cells and acts as an anti-oxidant. Since CoQ10 is

highly lipophilic, the topical and oral bioavailability

is very low. Several attempts have been made to

improve absorption. Latest technical developments

reveal that encapsulation of CoQ10 in NEs results

in a significantly enhanced bioavailability. The

application of CoQ10 has been further improved by

the development of novel CoQ10 double NEs

containing tocopherol and CoQ10 in individual

nanodroplets. In addition, the CoQ10

concentration in these NEs could be increased by

the development of a supersaturated CoQ10 NE.

Nanoemulsions as a vehicle for transdermal

delivery:

From in vitro and in vivo data, it was concluded

that the developed NEs have great potential for

transdermal drug delivery of aceclofenac. The NEs

of the system containing ketoprofen evidenced a

high degree of stability. Ketoprofen-loaded NEs

enhanced the in vitro permeation rate through

mouse skins as compared to the control.

The study was developed to evaluate the potential

of NEs for increasing the solubility and the in

vitro transdermal delivery of carvedilol. The

prepared NEs were subjected to physical stability

tests. Transdermal permeation of carvedilol

through rat abdominal skin was determined with

the Keshary-Chien diffusion cell. Significant

increase (P < 0.05) in the steady state flux (Jss) and

permeability coefficient (Kp) was observed in NE

formulations as compared to control or drug-

loaded neat components. The irritation studies

suggested that the optimized NE was a non-irritant

transdermal delivery system.

Celecoxib, a selective cyclo-oxygenase-2 inhibitor,

has been recommended orally for the treatment of

arthritis and osteoarthritis. Long-term oral

administration of celecoxib produces serious

gastrointestinal side effects. Skin permeation

mechanism of celecoxib from NE was evaluated by

FTIR spectral analysis, DSC thermogram, activation

energy measurement, and histopathological

examination. The optimized NE was subjected to

pharmacokinetic (bioavailability) studies on Wistar

male rats. Photomicrograph of a skin sample

showed the disruption of lipid bilayers as distinct

voids and empty spaces were visible in the



149

epidermal region. Results of skin permeation

mechanism and pharmacokinetic studies indicated

that the NEs can be successfully used as potential

vehicles for enhancement of skin permeation and

bioavailability of poorly soluble drugs.

Solid self-nanoemulsifying delivery systems as a

platform technology for formulation of poorly

soluble drugs :

New drug discovery programs produce molecules

with poor physico-chemical properties, making

delivery of these molecules at the right proportion

into the body, a big challenge to the

formulationscientist. The various options available

to overcome the hurdle include solvent

precipitation, micronisation or nanonization using

high-pressure homogenization or jet milling, salt

formation, use of microspheres, solid dispersions,

cogrinding, complexation, and many others. Self-

nanoemulsifying systems (SNES) form one of the

most popular and commercially viable approaches

for delivery of poorly soluble drugs exhibiting

dissolution rate limited absorption, especially those

belonging to the Biopharmaceutics Classification

System II/IV. SNES are essentially an isotropic blend

of oils, surfactants, and/or cosolvents that emulsify

spontaneously to produce oil in water NE when

introduced into aqueous phase under gentle

agitation. Conventional SNES consist of liquid forms

filled in hard or soft gelatin capsules, which are

least preferred due to leaching and leakage

phenomenon, interaction with capsule shell

components, handling difficulties, machinability,

and stability problems. Solidification of these liquid

systems to yield solid self-nanoemulsifying systems

(SSNES) offer a possible solution to the mentioned

complications, and that is why these systems have

attracted wide attention.

Use of nanoemulsions in cosmetics:

NEs have recently become increasingly important

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, NEs 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. Another

advantage is the small-sized droplet with its high

surface area allowing effective transport of the

active to the skin. Furthermore, NEs gain increasing

interest due to their own bioactive effects. This

may reduce the trans-epidermal water loss (TEWL),

indicating that the barrier function of the skin is

strengthened. NEs are acceptable in cosmetics

because there are no inherent creaming,

sedimentation, flocculation, or coalescence that

are observed with macroemulsions. The

incorporation of potentially irritating surfactants

can often be avoided by using high-energy

equipment during manufacturing.

NanoGel technology provides a simple process and

system to create submicron emulsions from an

easy-to-use, oil-in-water concentrate. The formula

is particularly suited to minimizing transepidermal

water loss, enhanced skin production, and

penetration of active ingredient. These

characteristics suggest that it would be particularly

useful for sun care products as well as moisturizing

and anti-aging creams-particular areas where

nanotechnology is already being incorporated into

a host of products currently on the market.

Likewise, it is also highlighted that it helps to give

skin care formulations a good skin feel, an

increasingly important characteristic for

formulators.

NEs have attracted considerable attention in recent

years for application in personal care products as

potential vehicles for the controlled delivery of

cosmetics and the optimized dispersion of active

ingredients in particular skin layers.

Evaluation of Nanoemulsions:

In Vitro Skin Permeation Studies (for transdermal

drug delivery system):



150

Franz diffusion cell is used to obtain the drug

release profile of the nanoemulsion formulation in

the case of formulations for transdermal

application. The extent or depth of skin

penetration by the released content can be

visualized by confocal scanning laser microscopy. In

vitro drug release can be determined by dispersing

an amount of the preparation in the donor

compartment of a Franz cell having a membrane as

barrier and monitoring the appearance of the

encapsulated drug in the reception medium,

usually PBS (pH 7.4) and stirring on a magnetic

stirrer at 100 rpm at 37C 1C. Samples (1 ml) of

the dispersion are withdrawn from the medium

and replaced with an equivalent amount of the

medium at definite intervals. The withdrawn

sample is then filtered using a 0.22 - 50 m filter

(e.g., Millipore, USA) and the drug released then

analyzed using UV-visible spectroscopy at

wavelength of peak absorption of the drug . An

alternative and popular method of ex-vivo release

study is performed using diffusion cell. The skin is

cut from the ear or abdomen and underlying

cartilage and fats care- fully removed. Appropriate

size of skin is cut and placed on the diffusion cell

which had earlier been filled with receptor

solution. Samples of the vesicular preparation are

then applied on the dorsal surface of the skin and

the instrument started. At intervals, up to 24 h,

samples are withdrawn from the receptor medium

and replaced with equal amounts of the medium

and the withdrawn samples analyzed for the drug

permeated using HPLC or UV spectroscopy. Semi-

permeable membrane such as regenerated

cellulose could be used in place of skin for in vitro

release studies. The flux J, of the drug across the

skin or membrane is calculated from the formula:

J = D dc/dx (2)

where D is the diffusion coefficient and is a

function of the size, shape and flexibility of the

diffusing molecule as well as the membrane

resistance, c is the concentration of the diffusing

species, x is the spatial coordinate .

In vivo release study otherwise referred to as

dermatopharmacokinetics, is carried out by

applying or admin- istering the preparation to

whole live animal. Blood samples are then

withdrawn at intervals, centrifuged and the plasma

analyzed for the drug content using HPLC. Results

obtained from in vitro and in vivo studies are

extrapolated to reflect bioavailability of the drug

formulation.

ADVANTAGES OF NANOEMULSIONS OVER OTHER

DOSAGE FORMS

Increase the rate of absorption.

Eliminates variability in absorption.

Helps solublize lipophilic drug.

Provides aqueous dosage form for water

insoluble drugs.

Increases bioavailability.

Various routes like tropical, oral and

intravenous can be used to deliver the product.

Rapid and efficient penetration of the drug

moiety.

Helpful in taste masking.

Provides protection from hydrolysis and

oxidation as drug in oil phase in O/W

Nanoemulsion is not exposed to attack by

water and air.

Liquid dosage form increases patient

compliance.

Less amount of energy requirement.

Nanoemulsion has a transparent and fluidy

property which improves the formulation

patient compliance and safe for administration

due to the absence of any thickening agent and

colloidal particles.

Nanoemulsions are thermodynamically stable

system and the stability allows self-

emulsification of the system .

Nanoemulsion formulation required low

amount of surfactant compared to

microemulsion. For example about 20- 25 %

surfactant is required for the preparation of

microemulsion but 5-10 % surfactant is suffi-

cient in case of nanoemulsion.



151

Limitations of nanoemulsions:

Even though nanoemulsions provide great

advantages as a delivery system, but sometimes

the re duced size of droplets are responsible for

the limited use of nanoemulsion formulation. Some

limitations of nanoemulsions are as follows :

The manufacturing process of nanoemulsion

formulation is expensive, because size

reduction of droplets is very difficult as it

required a special kind of instruments and

process methods. For example, homogenizer

arrangement, microfluidization

&ultrasonification require high financial

support.

Nanoemulsion stability creates a big problem

during the storage of formulation for the longer

time period. Ostwald ripening is the main factor

associated with unacceptability of

nanoemulsion formulations. This is due to the

high rate of curvature of small droplet show

greater solubility as compared to large drop

with a low radius of curvature.

Less availability of surfactant and co-surfactant

required for the manufacturing of

nanoemulsion is another factor which marks as

a limitation to nanoemulsion manufacturing.

Limited solubilizing capacity for high-melting

substances.

CONCLUSION:

Nanoemulsions have now-a-days become an

answer for the questions regarding targeted

delivery . Because of their submicron size , they can

be easily targeted . Moreover, the possibility of

surface functionalization with a targeting moiety

has opened new avenues for targeted delivery of

drugs, genes, photosensitizers& other molecules of

tumer area. So,nanoemulsions can set a better

mark for targeted drug delivery system

.

REFERENCES

1. Lachman L, Lieberman HA, Kanig JL. The

Theory and Practice of Industrial Pharmacy; 3 rd

ed. p. 510-1.

2. P.shah e tal , Nanoemulsion: A

pharmaceutical review , article info, Volume : 1 ,

Issue : 1 , Page : 24-32, Feb:2010

3. Nitin Sharma, Mayank Bansal, Sharad Visht,

PK Sharma, GT Kulkarni, Chron Young Sci;1:2-6, oct

2010

4. Charles Lovelyn, Anthony A. Attama,

Current State of Nanoemulsions in Drug Delivery,

Journal of Biomaterials and Nanobiotechnology,

Nov2011, 2, 626-639.

5. Koewn JH, Chi SC and Park ES. Transdermal

delivery of diclofenac using nanoemulsions. Arch.

Pharm. Res. 2004) 27: 351-356.

6. Lawrence MJ and Rees GD. Nanoemulsion-

based media as novel drug delivery systems.Adv.

Drug Del. Rev. (2000) 45: 89-121.

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for Drug Delivery through Different Routes,

Research in Bio-technology, Vol. 2, No. 3, 2011, pp.

1-13.

Commercial

nanoemulsion

formulations.

Drug/Bioactive

Category

Palmitate alprostadil Vasodilator, platelet

inhibitor

Ibuprofen non-steroidal anti-

inflammatory drug

(NSAID)

Dexamethasone Steroid

Indomethacin, (IND) NSAID

Propofol Anaesthetic

Flurbiprofenaxtil NSAID

Vitamins A, D, E and K Parenteral nutrition



152

8. N. Anton and T. Vandamme, The

Universality of Low- Energy Nano-Emulsification,

International Journal Phar- maceutics, Vol. 377, No.

1-2, 2009, pp. 142-147.

9. T. G. Mason, S. M. Graves, J. N. Wilking and

M. Y. Lin, Extreme Emulsification: Formation and

Structure of Nanoemulsions, Journal of Physics

and Condensed Matter, Vol. 9, No. 1, 2006, pp.

193-199.

10. C. Quin and D. J. Mc Clement, Formation of

Nano- emulsions Stabilized by Model Food Grade

Emulsifiers Using High Pressure Homogenization:

Factors Effecting Particle Size, Food Hydrocolloids,

Vol. 25, No. 5, 2011, pp. 1000-1008.

11. I. Sole, C. M. Pey, A. Maestro, C. Gonzalez,

M. Porras, C. Solans and J. M. Gutierrez,

Nanoemulsions Prepared by Phase Inversion

Composition Method: Preparation Vari-ables and

Scale up, Journal of Colloid and Interface Science,

Vol. 344, No. 2, 2010, pp. 417-423.

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