Nanoemulsions: stability and evaluation methods

1. NANOEMULSIONS: STABILITY
AND EVALUATION METHODS
NAME: ISHIKA CHOUDHARY
M.PHARMA

2. INTRODUCTION TO NANOEMULSIONS
• DEFINITION: NANOEMULSIONS ARE COLLOIDAL DISPERSIONS OF OIL AND WATER, STABILIZED BY
SURFACTANTS, WITH DROPLET SIZES TYPICALLY RANGING FROM 20 TO 200 NM.
• KEY FEATURES:
• SMALL DROPLET SIZE: NANOMETER SCALE, ENSURING HIGHER SURFACE AREA.
• THERMODYNAMICALLY STABLE: NANOEMULSIONS ARE STABLE OVER TIME DUE TO THE FORMULATION
OF FINE DROPLETS.
• CLEAR AND TRANSPARENT: NANOEMULSIONS ARE USUALLY TRANSPARENT OR SLIGHTLY OPALESCENT.
• APPLICATIONS: DRUG DELIVERY, COSMETICS, FOOD PRODUCTS, AND MORE.

3. COMPONENTS OF NANOEMULSIONS
1. OIL PHASE: HYDROPHOBIC PHASE, OFTEN CONTAINING LIPOPHILIC DRUGS OR ACTIVE INGREDIENTS.
1. EXAMPLES: MEDIUM-CHAIN TRIGLYCERIDES (MCT), MINERAL OIL, OR PLANT OILS.
2. AQUEOUS PHASE: WATER SERVES AS THE CONTINUOUS PHASE IN NANOEMULSION SYSTEMS.
1. EXAMPLES: DISTILLED WATER, SALINE.
3. SURFACTANTS: STABILIZE THE OIL-WATER INTERFACE AND PREVENT DROPLET COALESCENCE.
1. EXAMPLES: NONIONIC SURFACTANTS LIKE TWEEN 80, SPAN 80, OR POLOXAMERS.
4. CO-SURFACTANTS: USED TO ENHANCE STABILITY BY REDUCING INTERFACIAL TENSION.
1. EXAMPLES: ETHANOL, PROPYLENE GLYCOL.

4. STABILITY OF NANOEMULSIONS
• FACTORS AFFECTING STABILITY:
• DROPLET SIZE DISTRIBUTION: LARGER DROPLETS CAN LEAD TO SEPARATION, WHILE SMALL AND
UNIFORM DROPLETS CONTRIBUTE TO STABILITY.
• SURFACTANT CONCENTRATION: ADEQUATE SURFACTANT CONCENTRATIONS ARE NEEDED TO
MAINTAIN THE STABILITY OF NANOEMULSIONS.
• TEMPERATURE AND PH: EXTREME CONDITIONS MAY DESTABILIZE THE SYSTEM BY ALTERING
DROPLET SIZE OR CAUSING PHASE SEPARATION.
• IONIC STRENGTH: HIGH IONIC STRENGTH MAY CAUSE AGGREGATION OR PHASE INVERSION.
• VISCOSITY: HIGHER VISCOSITY MAY STABILIZE NANOEMULSIONS BY REDUCING DROPLET MOBILITY.

5. TYPES OF INSTABILITY:
• COALESCENCE: DROPLETS MERGE INTO LARGER DROPLETS, LEADING TO PHASE SEPARATION.
• OSTWALD RIPENING: LARGER DROPLETS GROW AT THE EXPENSE OF SMALLER ONES DUE TO
DIFFUSION.
• FLOCCULATION: DROPLETS AGGREGATE WITHOUT MERGING.
• CENTRIFUGATION: SEPARATION OF PHASES DUE TO DENSITY DIFFERENCES.

6. TYPES OF STABILITY IN NANOEMULSIONS
1. THERMODYNAMIC STABILITY:
1. NANOEMULSIONS ARE THERMODYNAMICALLY STABLE AND DO NOT REQUIRE EXTERNAL ENERGY FOR LONG-
TERM STORAGE.
2. KINETIC STABILITY:
1. INVOLVES THE PREVENTION OF SEPARATION PHENOMENA LIKE COALESCENCE OR CREAMING. NANOEMULSIONS
CAN BE KINETICALLY STABLE IF THE DROPLET SIZE IS SMALL AND THE FORMULATION IS WELL-BALANCED.
3. PHYSICAL STABILITY:
1. RETAINING THE APPEARANCE AND PROPERTIES OF THE SYSTEM OVER TIME (NO PHASE SEPARATION OR
AGGREGATION).

7. METHODS TO ENHANCE STABILITY
1.OPTIMAL SURFACTANT-TO-OIL RATIO:
1. ENSURING SUFFICIENT SURFACTANT IS PRESENT TO COVER THE SURFACE OF EACH DROPLET AND
PREVENT COALESCENCE.
2.USE OF CO-SURFACTANTS:
1. REDUCES INTERFACIAL TENSION, ENHANCING STABILITY.
3.ELECTROSTATIC STABILIZATION:
1. USE OF CHARGED SURFACTANTS TO PREVENT AGGREGATION BY ELECTROSTATIC REPULSION.

8. •Steric Stabilization:
•Surfactants and co-surfactants prevent droplet aggregation by forming a physical barrier around
the droplets.
•Increase Viscosity:
•Adding thickening agents or polymers can help stabilize nanoemulsions by slowing droplet
movement.

9. EVALUATION METHODS OF NANOEMULSIONS
1. DROPLET SIZE AND SIZE DISTRIBUTION:
1. TECHNIQUES:
1. DYNAMIC LIGHT SCATTERING (DLS)
2. LASER DIFFRACTION
3. TRANSMISSION ELECTRON MICROSCOPY (TEM)
2. IMPORTANCE: ENSURES CONSISTENCY IN THE FORMULATION AND STABILITY.
2. ZETA POTENTIAL:
1. DEFINITION: MEASURES THE SURFACE CHARGE OF THE DROPLETS. A HIGH ZETA POTENTIAL (POSITIVE OR NEGATIVE) INDICATES STABILITY DUE
TO ELECTROSTATIC REPULSION.
2. TECHNIQUE: ZETA POTENTIAL ANALYSIS USING A ZETASIZER.
3. VISCOSITY:
1. TECHNIQUES:
1. BROOKFIELD VISCOMETER
2. ROTATIONAL VISCOMETRY
2. IMPORTANCE: HELPS IN DETERMINING THE FLOW PROPERTIES AND STABILITY OF NANOEMULSIONS.

10. ADDITIONAL EVALUATION TECHNIQUES
1. TURBIDITY AND CLARITY:
1. TECHNIQUE: MEASURE THE OPTICAL CLARITY OR TURBIDITY OF THE NANOEMULSION.
2. IMPORTANCE: CLARITY INDICATES SMALL AND UNIFORM DROPLET SIZE.
2. STABILITY TESTING:
1. ACCELERATED STABILITY STUDIES:
1. HEAT/COOL CYCLING, CENTRIFUGATION, FREEZE-THAW CYCLES.
2. OBSERVING PHASE SEPARATION OR AGGREGATION AFTER THESE CONDITIONS HELPS PREDICT LONG-TERM STABILITY.
3. THERMAL STABILITY:
1. TECHNIQUE: STORE NANOEMULSIONS AT ELEVATED TEMPERATURES AND OBSERVE ANY CHANGES IN APPEARANCE OR PHASE
SEPARATION.
4. FREEZE-THAW STABILITY:
1. TECHNIQUE: FREEZE AND THAW THE FORMULATION MULTIPLE TIMES TO TEST ITS ABILITY TO WITHSTAND TEMPERATURE FLUCTUATIONS.

11. DRUG RELEASE STUDIES
1. IN-VITRO DRUG RELEASE TESTING:
1. METHOD: USE OF DIFFUSION CELLS (E.G., FRANZ DIFFUSION CELL) TO STUDY DRUG RELEASE BEHAVIOR
FROM NANOEMULSIONS.
2. DISSOLUTION STUDIES:
1. TECHNIQUES: USP DISSOLUTION APPARATUS FOR MONITORING DRUG DISSOLUTION RATE AND
BIOAVAILABILITY ENHANCEMENT.
3. DRUG-EXCIPIENT INTERACTIONS:
1. IMPORTANCE: ENSURE THE DRUG IS NOT CHEMICALLY INTERACTING WITH OTHER EXCIPIENTS, LEADING
TO INSTABILITY OR REDUCED BIOAVAILABILITY.

12. LONG-TERM STABILITY STUDIES
1.STORAGE CONDITIONS: ASSESS NANOEMULSION STABILITY AT VARIOUS TEMPERATURES
(ROOM TEMPERATURE, REFRIGERATED, ACCELERATED CONDITIONS).
2.VISUAL OBSERVATION: LOOK FOR SIGNS OF PHASE SEPARATION, CREAMING, OR
AGGREGATION.
3.PARTICLE SIZE MEASUREMENT: MONITOR DROPLET SIZE CHANGES OVER TIME.

13. CONCLUSION
• STABILITY OF NANOEMULSIONS: ACHIEVING LONG-TERM STABILITY IN NANOEMULSIONS IS
CRUCIAL FOR THEIR PRACTICAL APPLICATIONS, INCLUDING DRUG DELIVERY AND COSMETICS.
• EVALUATION METHODS: DROPLET SIZE, ZETA POTENTIAL, VISCOSITY, AND STABILITY TESTING
ARE ESSENTIAL FOR DETERMINING THE FORMULATION'S EFFECTIVENESS AND SAFETY.
• FUTURE DIRECTIONS: ADVANCEMENTS IN SURFACTANT DESIGN, CO-SURFACTANTS, AND
ENCAPSULATION TECHNIQUES WILL IMPROVE THE STABILITY AND PERFORMANCE OF
NANOEMULSIONS IN VARIOUS FIELDS.

14. THANK YOU