Formulation and Evaluation of Ethosomal Hydrogel Containing Vitamin A, Vitamin E and Ginger Extract for Enhanced Dermal Delivery

Figure 1 Skin Anatomy and Barrier Function

Table 1. Major Layers of Human Skin and Their Functions

Table 2. Advantages and Limitations of Topical Drug Delivery

3. Ethosomes: A Novel Vesicular Drug Delivery System

Ethosomes are advanced phospholipid-based nanovesicular carriers specifically designed to enhance the dermal and transdermal delivery of therapeutic agents. Introduced by Touitou and co-workers in 2000, ethosomes consist primarily of phospholipids, a relatively high concentration of ethanol (20–45%), water, and optional additives such as glycols or cholesterol [16]. Unlike conventional liposomes, the high ethanol content imparts remarkable flexibility and deformability to the vesicular membrane, allowing ethosomes to penetrate the compact lipid architecture of the stratum corneum more effectively.

The unique combination of ethanol and phospholipids enables ethosomes to transport both hydrophilic and lipophilic drugs into deeper skin layers without causing irreversible damage to the skin barrier. Ethosomes have demonstrated significant success in delivering corticosteroids, antifungal agents, antibiotics, antioxidants, anti-inflammatory drugs, herbal extracts, peptides, and cosmetic ingredients [17].

The increasing interest in ethosomal drug delivery is attributed to their high encapsulation efficiency, improved drug stability, controlled release behavior, and enhanced patient compliance. Recent developments have focused on integrating ethosomes into semisolid dosage forms such as hydrogels, creams, and emulgels to further improve topical retention and therapeutic efficacy [18].

3.1 Composition of Ethosomes

Ethosomes are composed of four major components, each contributing a distinct function to the vesicular system.

Phospholipids

Phospholipids constitute the structural framework of ethosomal vesicles. Commonly used phospholipids include: Soy phosphatidylcholine, Egg phosphatidylcholine, Hydrogenated phosphatidylcholine & Phosphatidylserine.

These amphiphilic molecules self-assemble into bilayer vesicles capable of encapsulating both hydrophilic and lipophilic therapeutic agents.

Ethanol

Ethanol is the most important component of ethosomes and is generally present at concentrations ranging from 20–45%. Ethanol performs multiple functions:

• Increases membrane flexibility
• Fluidizes phospholipid bilayers
• Disrupts intercellular lipid organization within the stratum corneum
• Enhances drug solubility
• Improves drug permeation

Water

Purified water forms the continuous phase of the vesicular dispersion and hydrates phospholipid molecules.

Polyols

Propylene glycol or Transcutol® may be incorporated to improve vesicle stability, enhance skin hydration, and further increase drug permeation

Table 3. Major Components of Ethosomes and Their Functions

3.2 Preparation Methods of Ethosomes

Several preparation methods have been reported depending upon drug characteristics and formulation requirements.

3.2.1 Cold Method

The cold method is the most widely employed technique for laboratory-scale preparation.

Procedure

1. Phospholipids are dissolved in ethanol under continuous stirring.
2. Propylene glycol is added to the ethanolic phase.
3. The aqueous phase is heated separately to approximately 30°C.
4. Water is slowly added to the ethanolic mixture under vigorous stirring.
5. The resulting dispersion is sonicated or extruded to reduce vesicle size.

3.2.2 Hot Method

• In this method, phospholipids are dispersed in warm water while ethanol is heated separately. Both phases are mixed at controlled temperature to obtain ethosomal vesicles.
• Although relatively less common, the hot method may improve the solubilization of certain lipid components

3.2.3 Thin Film Hydration Method

• A thin phospholipid film is first prepared by solvent evaporation under reduced pressure. Hydration of the lipid film with hydroethanolic solution results in ethosomal vesicles.
• This method generally provides uniform vesicle formation but requires additional processing time

Table 4. Comparison of Ethosome Preparation Methods

3.3 Mechanism of Skin Penetration

The superior skin penetration ability of ethosomes is primarily attributed to the synergistic action of ethanol and phospholipid vesicles.

Step 1: Ethanol Interaction

Ethanol penetrates the stratum corneum and disrupts the highly ordered lipid arrangement by increasing lipid fluidity.

Step 2: Vesicle Softening

The presence of ethanol makes phospholipid bilayers highly flexible and deformable.

Step 3: Enhanced Vesicle Penetration

Soft vesicles squeeze through the disrupted lipid domains and migrate into deeper epidermal layers.

Step 4: Drug Release

Once inside viable skin layers, the vesicles gradually release encapsulated drug molecules, producing prolonged therapeutic action.

This mechanism results in significantly greater drug deposition compared with conventional liposomes.

3.4 Factors Affecting Ethosomal Characteristics

Several formulation variables influence the physicochemical properties and performance of ethosomes.

Ethanol Concentration

Increasing ethanol concentration decreases vesicle size and increases flexibility. However, concentrations above approximately 45% may destabilize vesicles.

Phospholipid Concentration

Higher phospholipid concentration generally increases vesicle size and entrapment efficiency.

Cholesterol Content

Cholesterol enhances membrane rigidity but excessive amounts may reduce drug release

Sonication Time

Longer sonication reduces particle size but excessive sonication may result in drug leakage.

Storage Temperature

Refrigerated storage (4–8°C) generally improves vesicle stability

3.5 Advantages of Ethosomes

Ethosomes possess several advantages over conventional topical formulations:

• Excellent skin penetration
• High drug entrapment efficiency
• Controlled drug release
• Enhanced bioavailability
• Improved stability
• Non-invasive administration
• Reduced dosing frequency
• Better patient compliance
• Suitable for hydrophilic and lipophilic drugs
• Lower systemic toxicity

3.6 Limitations of Ethosomes

Despite numerous advantages, ethosomes also exhibit certain limitations:

• Phospholipid oxidation during storage
• Possible ethanol evaporation
• Relatively high production cost
• Limited long-term stability
• Scale-up challenges
• Requirement for specialized characterization techniques

Table 5. Comparison of Liposomal Nanocarriers

4. Hydrogel-Based Drug Delivery Systems

Hydrogels are three-dimensional crosslinked polymeric networks capable of absorbing large quantities of water while maintaining their structural integrity. Owing to their hydrophilic nature, excellent biocompatibility, softness, and controlled drug release behavior, hydrogels have become one of the most widely investigated semisolid dosage forms for topical drug delivery [19].

Hydrogels provide a moist environment at the site of application, improving skin hydration and facilitating enhanced drug permeation. Their non-greasy texture, cooling sensation, ease of washing, and patient acceptability make them superior to conventional ointments and creams for many dermatological applications.

When ethosomal dispersions are incorporated into hydrogel matrices, the resulting ethosomal hydrogel combines the penetration-enhancing capability of ethosomes with the prolonged residence time and controlled release properties of hydrogels. Such hybrid systems improve formulation stability, reduce vesicle aggregation, enhance skin retention, and increase therapeutic efficacy [20].

4.1 Ideal Characteristics of Hydrogels

An ideal hydrogel intended for topical application should possess the following characteristics:

• Biocompatible and non-toxic
• Non-irritant and non-sensitizing
• Appropriate viscosity
• Good spreadability
• Easy extrudability
• High drug-loading capacity
• Controlled drug release
• Good mechanical strength
• Stable during storage
• Easily washable with water
  2. Polymers Used in Ethosomal Hydrogels

Common polymers include: Carbopol 934, Carbopol 940, Carbopol 971, Hydroxypropyl methylcellulose (HPMC), Sodium carboxymethyl cellulose (NaCMC),Poloxamer 407, Chitosan, Xanthan gum, Sodium alginate and Polyvinyl alcohol (PVA).

Among these, Carbopol 934 and Carbopol 940 are the most extensively used owing to their excellent gelling ability, transparency, bioadhesion, and compatibility with ethosomal dispersions.

5. Vitamin A in Dermal Drug Delivery

Vitamin A is a fat-soluble vitamin that plays an indispensable role in maintaining skin integrity, cellular differentiation, epithelial growth, immune regulation, and collagen synthesis. It belongs to the retinoid family, which includes retinol, retinaldehyde, retinoic acid, and retinyl esters. Among these, retinol and retinoic acid are the most extensively utilized in dermatological and cosmetic formulations due to their proven efficacy in improving skin texture, reducing wrinkles, stimulating collagen production, and treating various hyperproliferative skin disorders [21].

Topically applied Vitamin A promotes epidermal renewal by regulating keratinocyte proliferation and differentiation through interaction with nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs). Activation of these receptors modulates the expression of genes responsible for collagen synthesis, epidermal turnover, and extracellular matrix remodeling [22].

Vitamin A also inhibits matrix metalloproteinases (MMPs), enzymes responsible for collagen degradation during aging and photoaging. Consequently, topical Vitamin A formulations improve skin elasticity, reduce fine wrinkles, accelerate wound healing, and restore epidermal barrier function [23].

Despite its remarkable therapeutic potential, Vitamin A exhibits several pharmaceutical limitations including poor aqueous solubility, sensitivity to light and oxygen, rapid degradation, and skin irritation at higher concentrations. Nano-vesicular carriers such as ethosomes provide protection against oxidative degradation while significantly improving dermal penetration and sustained release [24].

6. Vitamin E in Dermal Drug Delivery

Vitamin E represents a family of lipid-soluble antioxidants consisting of tocopherols and tocotrienols, among which α-tocopherol exhibits the highest biological activity. Vitamin E is naturally present within the epidermis and sebaceous glands where it protects cellular membranes against oxidative damage induced by ultraviolet radiation and environmental pollutants [25].

Oxidative stress generated by reactive oxygen species (ROS) accelerates lipid peroxidation, collagen degradation, inflammation, and premature skin aging. Vitamin E interrupts these oxidative chain reactions by donating hydrogen atoms to lipid radicals, thereby preventing membrane damage and preserving cellular integrity [26].

Topical Vitamin E also enhances epidermal hydration by stabilizing intercellular lipids within the stratum corneum. Moreover, it exhibits anti-inflammatory activity through inhibition of prostaglandin synthesis and suppression of inflammatory cytokines

Nanoencapsulation of Vitamin E within ethosomal vesicles protects it against oxidation and enhances penetration into deeper skin layers, providing prolonged antioxidant protection.

7. Ginger Extract in Dermal Drug Delivery

Ginger (Zingiber officinale Roscoe) is one of the oldest medicinal plants belonging to the family Zingiberaceae. Its rhizome contains numerous pharmacologically active phytoconstituents including: 6-Gingerol, 8-Gingerol, 10-Gingerol, 6-Shogaol, Zingerone, Paradols, Essential oils, Flavonoids and Terpenoids

These compounds exhibit broad-spectrum biological activities including antioxidant, anti-inflammatory, antimicrobial, analgesic, anticancer, and wound-healing effects [28].

Among these constituents, 6-gingerol is considered the principal bioactive compound responsible for most pharmacological actions

8. Synergistic Therapeutic Effects of Vitamin A, Vitamin E and Ginger Extract

• The simultaneous incorporation of Vitamin A, Vitamin E, and ginger extract into an ethosomal hydrogel provides a multifunctional therapeutic platform with complementary mechanisms of action. Each component contributes distinct pharmacological benefits while enhancing the efficacy of the others.
• Vitamin A promotes epidermal regeneration and collagen synthesis, Vitamin E protects against oxidative stress and stabilizes cellular membranes, whereas ginger extract suppresses inflammation and microbial growth. Their combined use may therefore improve wound healing, reduce oxidative damage, enhance skin hydration, and restore epidermal barrier function more effectively than individual agents [29].
• Furthermore, Vitamin E protects Vitamin A from oxidative degradation during storage and after topical application, thereby improving formulation stability. Ginger-derived antioxidants further reinforce this protective effect by scavenging reactive oxygen species generated during inflammatory skin conditions.

Table 6. Comparative Pharmacological Activities of Vitamin A, Vitamin E and Ginger Extract

Table 7. Major Bioactive Components and Their Pharmacological Activities

9. Rationale for Developing an Ethosomal Hydrogel Containing Vitamin A, Vitamin E and Ginger Extract

Despite the established therapeutic benefits of these bioactive agents, their clinical application is often limited by poor aqueous solubility, instability, susceptibility to oxidation, and inadequate penetration across the stratum corneum. Incorporating these compounds into an ethosomal hydrogel addresses these limitations by combining the penetration-enhancing properties of ethosomes with the sustained-release and patient-friendly characteristics of hydrogels. Such a formulation has the potential to improve drug stability, increase dermal retention, reduce dosing frequency, and enhance patient compliance. This integrated strategy may therefore offer a promising approach for the topical management of inflammatory skin disorders, wound healing, photoaging, and other dermatological conditions

10. Formulation Development of Ethosomal Hydrogel

The development of an ethosomal hydrogel containing Vitamin A, Vitamin E, and ginger extract requires careful optimization of formulation variables to ensure high encapsulation efficiency, desirable vesicle size, stability, controlled drug release, and enhanced skin permeation. A systematic approach involving pre-formulation studies, vesicle preparation, hydrogel incorporation, and physicochemical evaluation is essential for obtaining a stable and effective topical formulation.

10.1 Pre-formulation Studies

Pre-formulation studies provide essential information regarding the physicochemical properties of the active ingredients and excipients. Parameters commonly evaluated include:

• Organoleptic characteristics
• Solubility profile
• Melting point
• Partition coefficient (Log P)
• pKa determination
• UV-visible spectroscopic analysis
• Fourier Transform Infrared Spectroscopy (FTIR) for compatibility studies
• Differential Scanning Calorimetry (DSC)
• X-ray Diffraction (XRD)

These studies help identify potential incompatibilities and guide the selection of suitable formulation components.

10.2 Preparation of Drug-Loaded Ethosomes

The cold method is generally preferred for preparing ethosomes containing heat-sensitive vitamins and herbal extracts.

Typical formulation composition

After preparation, the ethosomal suspension is incorporated into a pre-neutralized Carbopol hydrogel under gentle stirring to obtain a homogeneous ethosomal hydrogel.

11. Evaluation of Ethosomal Hydrogel

Comprehensive characterization is essential to ensure formulation quality, stability, and therapeutic performance

11.1 Physical Appearance

The hydrogel should be evaluated for:

• Color
• Homogeneity
• Clarity
• Presence of phase separation
• Grittiness
• Consistency

A smooth, homogeneous, translucent gel without phase separation is generally considered acceptable.

11.2 pH Determination

Skin-compatible pH is essential to minimize irritation.

• Instrument: Digital pH meter
• Ideal pH range: 5.0–6.5

Maintaining physiological pH helps preserve skin barrier integrity and enhances patient acceptability

11.3 Vesicle Size and Polydispersity Index (PDI)

Particle size significantly influences skin penetration.

Measurement:

• Dynamic Light Scattering (DLS)

Ideal values:

• Particle size: 100–300 nm
• PDI: <0.30

Smaller and uniformly distributed vesicles exhibit superior dermal penetration.

11.4 Zeta Potential

Zeta potential indicates colloidal stability.

Ideal value:

• Greater than ±30 mV

High absolute zeta potential prevents vesicle aggregation during storage.

11.5 Entrapment Efficiency

Entrapment efficiency determines the proportion of active compounds encapsulated within the ethosomes.

Entrapment Efficiency (%)=Total Drug - Free DrugTotal Drug×100

Higher entrapment efficiency generally correlates with improved sustained release and therapeutic efficacy.

11.6 Drug Content

Drug content is determined using UV-visible spectrophotometry or High-Performance Liquid Chromatography (HPLC) to ensure uniform distribution of active ingredients within the formulation

11.7 Viscosity

Viscosity affects spreadability, patient compliance, and residence time.

Instrument:

• Brookfield Viscometer

An optimized viscosity ensures easy application without runoff.

11.8 Spreadability

Spreadability determines the ease of application over the skin surface.

S=M×LT

Where:

• S = Spreadability
• M = Weight tied to upper slide
• L = Length moved
• T = Time taken

Good spreadability enhances patient compliance and uniform drug distribution.

11.9 Extrudability

Extrudability evaluates the ease with which gel can be expelled from a collapsible tube.

Excellent extrudability indicates convenient patient use.

11.10 In Vitro Drug Release

Drug release studies are generally performed using:

• Franz Diffusion Cell

Membrane:

• Cellophane membrane
• Dialysis membrane

Release media:

• Phosphate buffer pH 7.4

Drug release kinetics may be analyzed using:

• Zero-order model
• First-order model
• Higuchi model
• Korsmeyer–Peppas model

11.11 Ex Vivo Skin Permeation Study

Animal skin (rat, porcine, or goat skin) mounted on a Franz diffusion cell is commonly used to assess:

• Drug permeation
• Drug deposition
• Flux
• Permeability coefficient

These studies simulate topical drug delivery under physiological conditions.

11.12 Stability Studies

Stability studies should follow ICH Q1A(R2) guidelines to evaluate formulation robustness under different storage conditions.

Parameters monitored include: Appearance, pH, Particle size, Entrapment efficiency,Drug content & Viscosity.

Table 8. Evaluation Parameters of Ethosomal Hydrogel