Development and Evaluation of Sprayable Nanoemulsion For Skin Cancer Using 5- Fluorouracil and Tretinoin

5-Fluorouracil (5-FU) is a widely used topical chemotherapeutic agent that acts by inhibiting thymidylate synthase, thereby interfering with DNA synthesis and leading to apoptosis in rapidly dividing cancer cells. However, its clinical utility is often limited by poor skin penetration, instability, and irritation at the site of application. Tretinoin, a derivative of vitamin A, is known to promote skin turnover, enhance permeability of active agents, and has shown synergistic effects when used in combination with other anticancer agents, including 5-FU. The use of nano emulsion -based drug delivery systems has emerged as a promising approach to overcome the limitations of conventional topical formulations. Nano emulsions, with droplet sizes in the Nano meter range (typically 20–200 nm), offer advantages such as increased drug solubility, enhanced skin permeation, controlled drug release, physical stability, and better cosmetic acceptability. Furthermore, incorporating such systems into a sprayable dosage form offers ease of application, uniform dosing, and improved patient compliance.

Nano emulsion: -

A nano emulsion is a thermodynamically or kinetically stable colloidal dispersion consisting of two immiscible liquids (typically oil and water), stabilized by surfactants and/or co-surfactants, with droplet sizes ranging from 20 to 200 nanometers. Unlike conventional emulsions, nano emulsions have ultra-small droplet sizes, which impart them with unique physicochemical and biological advantages, especially in pharmaceutical and cosmetic formulations.

Key Characteristics of Nano emulsions:

1. Droplet Size: Typically, between 20–200 nm, leading to a transparent or slightly bluish appearance.
2. High Surface Area: The small droplet size offers a large surface area for drug absorption.
3. Thermodynamic/Kinetic Stability: Some nano emulsions are thermodynamically stable, while others are kinetically stable with high resistance to coalescence, creaming, or phase separation.
4. Enhanced Solubility: Nano emulsions can solubilize poorly water-soluble drugs, increasing their bioavailability.
5. Improved Skin Permeation: Their nanometric size and composition enhance drug permeation through the skin, making them ideal for topical and transdermal delivery.
6. Controlled Release: They offer the possibility of sustained or controlled drug release at the site of action.

Components of a Nano emulsion:

1. Oil Phase: Solubilizes lipophilic drugs (e.g., isopropyl myristate, castor oil).
2. Aqueous Phase: Usually purified water.
3. Surfactant: Stabilizes the emulsion by reducing interfacial tension (e.g., Tween 80).
4. Co-surfactant: Enhances the flexibility of the surfactant film (e.g., Transcutol P, PEG 400).