Ethosomes: A Promising Drug Delivery Platform for Transdermal Application

Abstract

In recent years, transdermal drug delivery systems have gained considerable attention for their ability to enhance patient compliance and provide consistent drug release. However, the barrier function of the skin’s outermost layer remains the foremost challenge in these systems. As a result, there is a growing interest in the use of ethosomes as a cutting-edge nanocarrier in drug delivery. This review presents the concept and mechanism of action of ethosomes as well as the numerous types and preparation techniques available. It also discusses the significance of characterization methods and how they impact ethosomal properties along with recent advancements and applications in the realm of transdermal drug delivery. Ethosomes exhibit tremendous potential for the pharmaceutical industry, and optimizing preparation methods, performing comprehensive property studies, and exploring their applications are critical areas for future research.

1. Introduction

Transdermal drug delivery is a significant area of research in drug delivery due to its convenience, safety, and effectiveness as a non-invasive method of drug administration. It provides various benefits such as bypassing the first-pass effect linked to gastrointestinal absorption, improved patient compliance, sustained and controlled release, and reduced drug metabolism [1,2,3]. However, the skin’s natural barrier significantly restricts drug penetration and absorption during transdermal administration, which limits the usefulness of certain drugs. To overcome this limitation, researchers strive to improve drug permeability and absorption for effective transdermal delivery [4,5].

In recent years, novel nanocarriers have shown significant potential for drug delivery [2,6,7,8,9]. Ethosomes are drug complexes formed by combining a drug with a carrier, typically an alcohol or its derivatives. This carrier contains an active alcohol component that provides better permeability and drug loading capacity than traditional liposomes [10,11]. Ethosomes have demonstrated two major benefits: enhancing drug–skin interactions by improving drug absorption and penetration and being easily adaptable to various drug types, including water-soluble, fat-soluble, and unstable drugs. As a result, using ethosomes can increase drug stability and reduce systemic side effects and drug wastage [12]. Furthermore, ethosomes have various advantages in the realm of transdermal drug administration and have potential uses across sectors such as pharmaceuticals, biotechnology, veterinary medicine, cosmetics, and nutrition, among others [13]. Most of the products marketed to date are pharmaceuticals. A specific instance is the Decorin cream from Genomic Cosmetics, based in Pennsylvania, the USA, which aims to tackle anti-aging and pigmentation issues [14]. Noicellex and Supravir are topical creams created by Novel Therapeutic Technologies and Trima, respectively. Noicellex is an anti-cellulite cream designed to enhance the effectiveness of its active ingredient by deepening its penetration. In contrast, Supravir is a cream that encases acyclovir, a drug employed to treat herpes infections by disrupting lipids [15], whereas Cellutight EF is a topical anti-cellulite cream manufactured by Hampden Health (USA). The lotion is formulated with a potent combination of components that enhance metabolic rates and decrease fat by penetrating deeper into the skin [16].

The purpose of this review is to present a comprehensive analysis of existing research pertaining to ethosomes, a contemporary drug delivery technology employed in the field of transdermal drug delivery. The review largely centers on the many classifications of ethosomes, their underlying mechanisms, methods of manufacturing, influential variables, and clinical investigations. In this discourse, we shall explore the obstacles and opportunities related to the facilitation and enhancement of ethosomes as a mechanism for delivering drugs via the skin in transdermal drug delivery. The objective of this study is to offer a thorough comprehension of the research on transdermal medication delivery using ethosomes while also providing valuable insights and suggestions for future researchers in this particular field of study.

2. The Type of the Ethosomes

Ethosomes can be classified according to their composition into several categories, including classical ethosomes, binary ethosomes, transethosomes, composite phospholipid ethosomes, and active targeting ethosomes. Each of these categories possesses distinct traits and advantages (Figure 1).

2.1. Classical Ethosomes

Classical ethosomes are stable vehicles for delivering drugs and composed of phospholipids, cholesterol, ethanol, and water in varying concentrations. These vehicles can be used to transport active ingredients effectively and efficiently [17]. Compared to common liposomes, classical ethosomes have a high concentration of ethanol, resulting in better permeability. For instance, Yucel et al. developed ethosomes and liposomes loaded with rosmarinic acid. The study showed that ethosomal formulations could enhance drug permeation across human skin and had a higher transdermal flux than liposomes [18]. Feng et al. prepared ethosomes and liposomes of psoralen. The transdermal flow and skin deposition of psoralen in ethosomes were found to be 38.89 ± 0.32 mg/cm²/h and 3.87 ± 1.74 mg/cm², respectively. These values were observed to be 3.50 and 2.15 times higher than those observed with liposomes [19]. The above results have all shown that the ethosomes have a better permeability compared to the ordinary liposomes.

2.2. Binary Ethosomes

Binary ethosomes are produced through enhancements to classical ethosomes by using a propylene glycol and ethanol mixture in the preparation process instead of single ethanol. This reduces the amount of ethanol and its volatility, increasing drug solubility and formulation stability as well as promoting drug penetration [20,21,22]. Many researchers have prepared binary ethosomes to increase formulation stability and improve skin penetration. For example, Wu et al. prepared ethosomes, binary ethosomes, and transfersomes containing terbinafine hydrochloride. The study’s findings indicated that binary ethosomes composed of ethanol and propylene glycol in a 7:3 (w/w) ratio were the most effective in enhancing drug permeation through the skin. Additionally, rhodamine B exhibited a greater depth of penetration and fluorescence intensity when delivered through binary ethosomes compared to ethosomes and transfersomes [17]. Akhtar et al. prepared ethosomal gel and binary ethosomal soy lecithin and binary mixture (1:1) gel formulations of triamcinolone. The vesicles exhibited higher zeta potential and EE and improved Rhodamine B penetration than the reference ethosomal gel [23].

2.3. Transethosomes (TEs)

TEs represent a newer generation of ethosomal systems, initially introduced by Song et al. [24]. This vesicle type has been developed to merge the advantages of both ethosomes and TEs into a single composition [10]. The formulation of TEs involves the incorporation of a penetration enhancer or surfactant, such as Tween 20, Span 60, sodium cholate, or deoxycholic acid sodium, into traditional ethosomes [25]. The surfactant is inserted into the phospholipid bilayer, which increases the distance between the phospholipid molecules, disrupts the sequence of the phospholipid bilayer and increases the fluidity of the ethosomes. Upon skin hydration, the ethosomes undergo deformation and squeeze into the stratum corneum, thus facilitating the transdermal absorption of the drug. For example, Moolakkadath et al. prepared fisetin TEs that showed better penetration than conventional fisetin gel [26]. Albash et al. prepared olmesartan TEs that showed higher permeability than drug suspensions in dermal delivery studies of Olmesartan [27].

2.4. Composite Phospholipid Ethosomes (CE)

Compared to conventional ethosomes, CE consists of both saturated and unsaturated phospholipids (soybean lecithin, phosphatidylcholine (PC), hydrogenated lecithin). This composition effectively inhibits unsaturated phospholipid oxidation [28]. For example, Chen et al. prepared a curcumin-loaded CE to improve the stability and transdermal absorption of the conventional ethosomes. The curcumin CE prepared with a 1:1 ratio of PC/hydrogenated phosphatidylcholine (HPC) demonstrates superior vesicle stability and flexibility compared to traditional ethosomes. The high stability is because of the interaction between saturated phospholipids and unsaturated phospholipids in the phospholipids, which can effectively inhibit the oxidation of unsaturated phospholipids [29].

2.5. Actively Targeted Ethosomes

Actively targeted ethosomes are prepared by modifying certain ligands, including galactosylated chitosan, hyaluronic acid (HA), polyethyleneimine, and sodium cholate, on the surface of conventional ethosomes [30]. Zhang et al. prepared ethosomes modified with hyaluronic acid (HA) to enhance their therapeutic efficacy through specific targeting of the CD44 protein, which is known to be upregulated in inflamed psoriatic skin [31]. Sagar et al. prepared a study in which they formulated ethosomes loaded with hepatitis B surface antigen (HBsAg). Their findings revealed that these ethosomes exhibited superior internalization capabilities and immunogenicity when compared to elastic liposomes [32,33].

3. Mechanisms for Penetration of Ethosomes

The skin, a vital organ of the body, comprises the epidermis, dermis, and subcutaneous layers. It plays a crucial role in the process of transdermal absorption. It is commonly accepted that drugs transported through the epidermis are quickly removed from the capillaries without an absorption barrier forming. The epidermis is made up of multiple layers, such as the outermost SC layer and the viable epidermal layer, consisting of the hyaline, granular, spiny, and basal layers. The SC layer, with a thickness of approximately 10~20 microns and no phospholipids, is regarded as a non-living layer of dead cells that facilitates drug penetration through a passive diffusion process regulated by physicochemical laws. Therefore, the outermost stratum corneum (SC) layer of the skin functions as the principal barrier for the process of transdermal absorption.

There are two distinct routes for drugs to penetrate the skin and enter the systemic circulation: the epidermal route and the appendage route. The drug, when applied to the skin via the epidermal route, is released from the preparation onto the skin surface. Drugs dissolve and pass through either the intercellular lipid (intercellular route), keratinocytes and intercellular lipids (transcellular route), or both (Figure 2). It then diffuses into the active epidermis and distributes to the water-active epidermis before finally diffusing into the dermis, where it is eventually absorbed by capillaries. The primary method of drug absorption through the skin is through the epidermal route. Drugs have the ability to permeate the skin appendages at an accelerated pace; these appendages only comprise about 0.1% of the skin’s total surface area, making them a less common pathway for drug absorption in most scenarios. For certain ionic medications and macromolecules that are water soluble, passage through the stratum corneum, which is lipid-rich, is a challenging task.

The high permeability of ethosomes is connected to the large amount of ethanol they contain, and the disruption of the lipid structure of the stratum corneum can occur. This results in an active stratum corneum, larger gaps between cells, and the increased flexibility and fluidity of the phospholipid layer. Ethosomes may potentially aid drug penetration during transdermal penetration by disrupting the skin barrier through the following mechanisms: (1) The disruption of the skin barrier through the presence of surfactants within ethosomes, which has the potential to disrupt the barrier function of the stratum corneum, hence enhancing the permeation of drugs into the skin. (2) Ethosomes contain water-soluble polymers that can form hydrates with water molecules present in the skin, augmenting the solubility and permeability of the drug in the skin. (3) Ethosomes act as a carrier for the drug. Alcohol plasmas act as drug carriers, stably encapsulate drugs within microparticles, protect against skin metabolizing enzymes, and enhance drug permeability and residence time [34,35,36,37]. The pliable and adaptable ethosomal vesicles display amplified permeability across the unordered lipid bilayers of the stratum corneum, a commonly acknowledged occurrence referred to as the “ethanol effect” (Figure 3A) [28,38,39]. The fusion of phospholipids present in ethosomes with the skin layers underneath produces the “ethosomes effect”, which aids in the improved penetration of the unbound medication (Figure 3B) [28,38,40,41]. In summary, the impact of ethanol on the lipids of the stratum corneum and the fluidity of vesicles, along with the potential for interaction between ethosomes and the stratum corneum, may result in enhanced drug delivery.

4. Methods of Ethosomal Penetration Mechanisms

The studies typically elucidate the penetration mechanisms of ethosomes through molecular conformation, thermodynamic properties, ultrastructure, and fluorescent labeling at present. The researcher employed various analytical methods, such as attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), and imaging techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM) [34,42,43].

4.1. ATR-FTIR and Raman Spectroscopy

ATR-FTIR is a method utilized for molecular-level characterization of skin SC groups. The vibrations of CH₂, including the asymmetric stretching at 2920 cm⁻¹, symmetric stretching at 2850 cm⁻¹, and shear vibration at 1460–1470 cm⁻¹, can be linked to the intercellular lipids of the stratum corneum [28]. The CH₂ shear bands indicate the barrier effect of the orthogonal lattice on lipids, the ratio between the maximum intensity of υsym CH₂ and υasym CH₂ (H_2920/2850), which is thought to be a measure of the lateral interaction between acyl chains in the stratum corneum [44]. After treating skin with DPH ethosomes, Xiao-Qian Niu et al. observed a notable increase in the values of both symmetric and asymmetric methylene stretching bands when compared to the control samples, with a CH₂ cleavage width of 66.85 ± 2.13, indicating an ordered–disordered lipid transition. The treatment of pig skin with a formulation containing vesicles showed a significant decrease in H_2920/2850 values and an increase in A₂₈₅₀ values compared to the control [38]. The study conducted by Virginia Campani revealed that EthoVK1 resulted in a noteworthy reduction in H2920/2850 values by 1.71 ± 0.03 compared to the untreated group. The use of ATR-FTIR spectroscopy indicates that ethosomes penetrate the stratum corneum, enhancing lipid fraction enrichment and ordered structure formation in the skin, facilitating further drug penetration [45].

Raman spectroscopy can be used to study the molecular structure and chemical properties of ethosomes to understand the effect of ethosomes on drug stability and bioavailability. Aika Sekine et al. utilized Raman spectroscopy to examine the interaction between DSPC liposomes and polyols. The results exhibited broader peaks and slightly lower wave numbers of DSPC liposomes–BG and DSPC liposomes–PG compared to DSPC liposomes–Gly. This suggests that the inclusion of BG and PG in DSPC liposomes leads to a compact stacking arrangement of the compound in the bilayer [46].

4.2. DSC

In recent years, ethosomes have been extensively studied by researchers using DSC techniques, and some important results have been obtained. The investigation of the phase change characteristics of ethosomes within the spectrum of skin temperature allows for a comprehensive comprehension of the underlying mechanism governing the interaction between ethosomes and the skin. This study aims to enhance the comprehension of the transdermal transport mechanism of ethosomes and to optimize the design and application of these ethosomes [47].

J Xiaowei et al. designed KP-loaded functionalized single-walled carbon nanotube composite ethosomes (f-SWCNTs-KP-ES). DSC indicated that KP was present in an amorphous state following adsorption and loading onto f-SWCNTs. Moreover, ethosomes were found to enhance transdermal absorption and increase the bioavailability of KP [48]. Yu Li et al. formulated and subsequently compared ethosomes loaded with curcumin (referred to as CE) that possessed varying phospholipid compositions. The use of differential scanning calorimetry (DSC) revealed a noteworthy interaction between unsaturated phosphatidylcholine (PC) and saturated hydrogenated phosphatidylcholine (HPC). This interaction led to a decrease in PC peroxidation when HPC was present, hence disturbing the lipid domain of SC [29].

4.3. SEM and TEM

SEM and TEM allow for the macroscopic observation and microstructural analysis of the skin to further visualize the inner layers of the skin and thus evaluate the potential of ethosomes for transdermal drug delivery [49,50].

Xiaoqian Niu et al. observed by SEM that there were almost no detached SC fragments in the skin samples treated with PBS and diphenhydramine (DPH) aqueous solution; a significant number of fragments were observed to detach. Conversely, in the pig skin samples treated with DPH ethosomes and DPH ethanol, a substantial amount of fragments were also observed to detach. Thus, when porcine skin was soaked in DPH ethosomes and 30% ethanol enhancer solution, intercellular lipids were dissolved and extracted, resulting in separation from intact SC and desquamation. The ultrastructure of porcine skin was observed by TEM. The results showed that compared with the dense SC cells in the control group, the keratinocyte was destroyed, the SC cell layer was further expanded, and the intercellular gap between the cells in the stratum corneum appeared to be expanded; the results are shown in Figure 4 [38].

4.4. CLSM

CLSM is a comprehensive technique that provides high-resolution three-dimensional images and has fluorescent dye labeling technology, which is commonly used to observe and analyze the transdermal transfer process of ethosomes. By observing the distribution of ethosomes and fluorescent dyes, the distribution of ethosomes on the skin surface, the degree of penetration, and the interaction with the stratum corneum can be determined [51,52].

CLSM with dual-fluorescent labeled ethosomes was performed to investigate the depth of penetration of lipophilic substances contained in ethosomes into the skin’s underlying layers. The localization of the fluorescent tracer gradually increased through the skin layer over time (1, 2, 4, and 8 h) for all formulations. In addition, the three lipid vesicles facilitated the penetration of RhB into the skin compared to the plain RhB hydrogel and improved the penetration of rhodamine-loaded nanovesicles through skin layers with a wider distribution and higher fluorescence intensity; the results are shown in Figure 5 [53]. Yi-Ping Fang et al. used the CLSM technique to examine the intensity and depth of protoporphyrin IX (PpIX) in order to gain insights into the penetration behavior of PpIX synthesis produced by 5-aminolevulinic acid (ALA) in both normal skin and overproliferating mouse skin models. The findings of the study indicated that the overall concentration of ALA in an aqueous solution of ALA and ALA encapsulated in an ethosome carrier (PE) in the skin of the mice was measured to be 255.25 ± 42.09 and 930.07 ± 96.32, respectively. Furthermore, it was observed that the PpIX molecules exhibited a maximum depth of penetration of 30 μm into the skin of the mice, with an extension of around 80 μm [54].

5. The Method of Preparation of Ethosomes

Researchers have used different methods to obtain the optimal vesicle of ethosomes. The preparation method of ethosomes is relatively simple compared to liposomes because ethosomes do not require the removal of organic solvents. The most common methods for preparing ethosomes include the ethanol injection method, rotary film evaporation, vortex sonication, the pH gradient method, and the microfluidic technique.

5.1. Thin Film Dispersion Method

The recommended quantity of phospholipids and cholesterol is dissolved in a limited quantity of suitable organic solvents. This solution is then subjected to a rotary evaporator to eliminate the solvents, resulting in the formation of a consistent lipid film on the inner surface of the container. The drug was first dissolved in a volume of water–ethanol mixture, then, with the rotation of the lipid film hydration, left at room temperature and filtered via ultrasound to obtain a suspension ethosomes [55,56,57]. The ethosomes prepared by this method have a large particle size, which requires an ultrasonic probe to make the particle size smaller and more uniform, but it is not easy to produce precipitation, and the system is stable.

5.2. Ethanol Injection Method

The ethanol injection method has the following steps: dissolve phospholipids and cholesterol in ethanol, place them in a closed container, slowly add the water phase while stirring, continue stirring for a certain period of time, and filter it through the microporous membrane to obtain the solution. In general, lipophilic drugs can be dissolved in ethanol first. Ursolic acid, paeonol, and benzocaine ethosomes are prepared by this method [58,59,60]. Hydrophilic drugs are first dissolved in water during preparation, phospholipids and cholesterol are dissolved in an alcohol solution, and then the aqueous solution is slowly added to the ethanol solution, stirred for a certain period of time, and cooled to obtain ethosomes [61,62,63]. Vancomycin hydrochloride and anthralin ethosomes are prepared by this method [5,64]. The ethosomes prepared by this method are difficult to pass through the microporous filter membrane, and the prepared particle size is relatively large, which is easy to adsorb and causes precipitation and delamination.

5.3. Injection–Ultrasound Combination Method

A certain amount of phospholipid and the main drug are dissolved in ethanol, placed on a magnetic stirrer, and slowly injected into the phosphate buffer while stirring under airtight conditions at room temperature; the stirring is continued for a certain period of time, and then, the probe is ultrasonicated in an ice water bath and passed through the micropore to obtain the ethosomes [65]. Compared with the injection method, the combined injection–ultrasound method adds the step of ultrasound, which may be related to the reduction in the particle size distribution of the ethosomes. The ethosomes prepared after the ultrasound probe have a small and uniform particle size, which is advantageous for permeating the microporous membrane and is not easily precipitated, and the system is stable.

5.4. pH Gradient Method

Under airtight stirring conditions, the buffer is injected into the phospholipid-dissolved ethanol solution; after the injection is completed, stirring is continued for a certain period of time, and the solution is cooled at room temperature to obtain blank ethosomes. The drug is added while stirring to dissolve it completely, and then, NaOH is added to adjust the pH of the outside of the vesicles so that a pH gradient is formed inside and outside the vesicles, and then, the whole system is fully incubated at a certain temperature. After a period of time, the main drug passes through the lipid bilayer and enters the vesicles to yield ethosomes [20,59,66]. This method involves changes in pH during the preparation process, so it is only suitable for drugs whose physical and chemical properties are not affected by pH [67]. The encapsulation rate of water-soluble drugs is very low because hydrophilic drugs are not easily adsorbed on the surface of lecithin. Therefore, the pH gradient method is suitable for lipophilic drugs.

5.5. Microfluidic Techniques

Phospholipids and cholesterol are dissolved in a certain concentration of ethanol and stirred thoroughly, followed by dissolving the drug in a lipid ethanol solution on a magnetic stirrer; the organic ethanol solution was mixed with water in a certain ratio and finally prepared by NanoAssemblr [68]. Dexamethasone-loaded liposomes were prepared by this method [69]. The liposomes prepared by microfluidics have a monolayer structure, and the liposomes obtained by this method have higher assembly capacity and efficiency. The liposomes prepared by this method had uniform, tunable, and reproducible particle size [70].

6. Factors Affecting Properties of Ethosomes

During the pursuit of an optimum formulation of ethosomes, several process variables may exert an influence on the characteristics of the ethosomes. These variables mostly pertain to the formulation preparation of ethosomal formulations, which are classified as follows.

6.1. Effect of Ethanol

Ethanol assumes a significant function within ethosomal systems, as it bestows distinctive characteristics upon the vesicles, encompassing size, zeta potential, stability, encapsulation efficiency (EE), and skin permeability. Reportedly, the percentage of ethanol in ethosomal systems typically varies between 20% and 45% (w/w). It has been observed that when the ethanol concentration decreases, the size of the vesicles in these systems tends to rise [71]. In addition, ethanol makes the vesicles negatively charged to improve the stability of the vesicles and avoid the accumulation of the vesicle system due to static electricity. A high concentration of ethanol can not only increase the solubility of the drug in the stratum corneum of the skin but also promote the penetration of the drug. In the process of transdermal penetration, the ethosomes can deform, pass through the cell gap smaller than its own particle size, and reach the deep layer of the skin [72]. Therefore, the penetration depth of ethosomes is deeper than that of liposomes, which significantly improves the efficiency of drug transdermal penetration. The presence of a high concentration of ethanol has the potential to decrease the thickness of the vesicle membrane layer, thereby impacting the EE [73].

6.2. Effect of Phospholipids

The phospholipid concentration in an ethosomal formulation falls within the range of 0.5% to 5%. It could influence the size and EE of the ethosomes [74,75]. The vesicle size increased slightly or moderately with the increase in phospholipid concentration, and the EE of ethosomes first increased and then decreased with the increase in phospholipid concentration [76]. The phospholipids also play an important role in the process of transdermal penetration. The phospholipids could fuse with the lipids in the skin stratum corneum to disrupt the dense and ordered structure of the skin stratum corneum, allowing for the drug to be released from the ethosomes and enter the skin in a free state [77].

6.3. Effect of Propylene Glycol

It was found that propylene glycol could affect the size, EE, skin permeation, and stability of the ethosomes. The incorporation of propylene glycol into the ethosomal systems could further reduce the particle size of the vesicles [72]. Propylene glycol may also improve the volatility and skin irritation of the ethanol and increase the stability of the vesicles. At the same time, when propylene glycol is used in combination with other accelerators, it can not only increase the solubility of the drug and the accelerator but also can synergistically promote the penetration of the drug. The presence of ethanol and propylene glycol in ethosomes can also increase the EE of the drug and improve the distribution of the drug in the vesicle [75,78].

6.4. Effect of Cholesterol

The use of cholesterol has been observed to enhance the EE of ethosomes while concurrently augmenting the skin penetration capability of liposomes by promoting membrane fluidity. Excessive cholesterol will result in a decrease in the ability of vesicles to encapsulate drugs. Cholesterol can also increase the spatial stability of the ethosomal system, thereby reducing vesicle aggregation and particle size [79,80].

6.5. Effect of Edge Activators

The careful choice of an appropriate edge activator or penetration enhancer is a crucial aspect in the formulation of ethosomes since it significantly impacts the characteristics of the ethosomal system. After the edge activator is inserted into the phospholipid bilayer, it can increase the distance between the phospholipid molecules, interfere with the sequence of the phospholipid phthalide chain, and increase the fluidity of the ethosomes. Under the hydration of the skin, the ethosomes deform and pass through the stratum corneum, thereby promoting the transdermal absorption of the drug [81,82]. Previous studies have indicated that the inclusion of Tween 80 in ethosomal formulations leads to a decrease in vesicle size, enhancement of system stability, and improvement of skin permeability characteristics [72,83].

7. Characterization of the Ethosomes

Various methodologies have been documented in the literature for the determination of characterisation criteria pertaining to ethosomes, including vesicle size and shape, size distribution, and polydispersity index (PDI), EE, zeta potential, stability, loading capacity and vesicle fluidity, drug release, and drug content, which are useful for optimizing the ethosomal formulation. Each of these characterization methods is discussed in detail in other articles and is not listed here [61,84].

8. Different Applications of Ethosomes

Compared with ordinary liposomes, ethosomes have many advantages, such as large drug loading, high EE, small particle size, better flexibility, high transdermal efficiency, and large skin retention. The ethosomes as transdermal drug delivery systems have been used in dermatological drugs, non-steroidal anti-inflammatory drugs, antifungal and antiviral drugs, hormone drugs, and other drugs [22,85].

8.1. Delivery of Antifungal and Antibacterial Drug

Numerous pathogenic microorganisms responsible for angioinvasive fungal infections are widely distributed in the environment and typically do not result in clinical infection among individuals with a fully functional immune system [86]. When the antifungal and antibacterial drugs are made into ethosomes, the increase in transdermal permeation can achieve the goal of maintaining a constant plasma drug concentration while reducing the number of administrations [41,65,77]. For example, Shetty S. et al. developed an ethosomal gel loaded with clove oil. The antifungal activity of the ethosomal gel against the fungus Candida albicans was found to be satisfactory in comparison to the pure clove oil [87]. Maheshwai et al. also showed that clotrimazole-loaded ethosomes have a stronger penetration enhancing effect and a higher inhibitory effect against Candida species than liposome formulations [88]. Bagchi et al. developed ethosomes loaded with psoralen. The resulting PSO–ethosomes demonstrated effective antimicrobial activity against Staphylococcus aureus and facilitated psoralen transport through the biological barrier; the results are shown in Figure 6 [89]. Zhu et al. also prepared hexyl aminolevulinate (HAL)-loaded ethosomes (HAL-ES). The application of antimicrobial photodynamic therapy (aPDT) using a 0.5% concentration of HAL resulted in a significant reduction in C. albicans biofilm activity by 69.71%. However, when aPDT was administered with 0.5% HAL-ES, an even greater reduction in biofilm activity was observed, reaching 92.95 ± 0.16%. Additionally, this treatment inhibited hyphal growth by 25.71 ± 1.61% within a 48 h timeframe. These findings were found to be associated with a 3-fold increase in C. albicans plasma membrane permeabilization [90]. In addition, there are many other drugs (terbinafine hydrochloride, vancomycin hydrochloride, griseofulvin, ketoconazole, luliconazole, eugenol, and silver sulfadiazine) that have been encapsulated in ethosomes to enhance antifungal and antibacterial activity (

Table 1. Examples of applications of ethosomes as transdermal delivery systems of antifungal and antibacterial drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Terbinafine hydrochloride	pH gradient method	Antifungal	Ethosomes, binary ethosomes	The penetration depth and fluorescence intensity ↑ (binary ethosomes compared with other formulations)	[17]
Vancomycin hydrochloride	Ethanol injection method, cold method	Antibiotic	Ethosomes	The minimum inhibitory concentration of infected pathogen ↑	[5]
Clove oil	Mechanical-dispersion method	Antifungal	Ethosomal gel	Antifungal activity against the fungus C. albicans ↑ (compared with pure clove oil)	[87]
Clotrimazole	Mechanical-dispersion method	Antifungal	Ethosomes	Zone of inhibition (34.6 ± 0.57 mm) ↑ (compared with ultradeformable liposome)	[88]
Psoralen	NA	Antimicrobial	Ethosomes	Improved antimicrobial activity ↑, biomass for both bacteria 30% ↓	[89]
Hexyl-Aminolevulinate	NA	Recurrent Candida albicans infections	Ethosomes	The sessile minimum inhibitory concentration 50 ↓ and survival rate of C. albicans biofilm-infected mice ↑ (compared with Hexyl-aminolevulinate)	[90]
Griseofulvin	Mechanical-dispersion method	Antifungal	Ethosomes	GRF-loaded ethosomes have an adequate profile and drug skin retention ↑	[91]
Ketoconazole	Thin-film evaporation and hydration method	Antifungal	Ethosomes	Improved antifungal activity ↑	[92]
Luliconazole	Ultrasound injection method	Antifungal	Ethosomal gel	Inhibits the activity of Candida parapsilosis ↑ (compared with Aspergillus niger)	[93]
Clotrimazole encapsulated Cavamax W7	Ethanol injection method	Antifungal	Ethosomal gel	Stable and efficacious ↑ (composite ethosomes than ethosomal formulation)	[94]
Eugenol	Injection homogenization method	Antibacterial	Ethosomes	Antibacterial activity (>93%) ↑ (compared with free eugenol)	[95]
Silver sulfadiazine	Cold method	Antibacterial	Ethosomal gel	Wound contraction rate of 96.83% (compared with free drug)	[96]

Note: “↑”: increase; “↓”: decrease; NA: Not applicable.

).

8.2. Delivery of Anticancer Drug

Mettlesome have emerged as a highly promising transdermal delivery technology for the treatment of skin cancer due to their non-invasive nature and low occurrence of notable adverse effects. The researchers Yu et al. formulated an ethosomal gel containing mitoxantrone (MTO) for the purpose of treating cancer. The ethosomes exhibited considerably more permeability in vitro across rat skin and demonstrated notable cytotoxicity. Furthermore, they displayed a heightened anti-melanoma impact in vivo compared to MTO solutions, achieved through the enhancement of calreticulin membrane translocation in B16 cells. F Amr Gamal et al. prepared a VMD-loaded ethosomal gel containing 65% isopropyl alcohol and 35% ethanol for the management of basal cell skin carcinoma [97]. The ethosomal gel that exhibited the highest level of effectiveness demonstrated a notable decrease in both the quantity and size of papillomas when compared to the oral VMD suspension and the ethosomal gel loaded with VMD but containing no isopropyl alcohol (IPA). Raj et al. prepared a nano-sized cytarabine-loaded ethosome to optimize the transdermal administration of drugs for the treatment of leukemia [98]. The formulation exhibited a reduced lag time and increased transdermal penetration of cytarabine within 3–12 h after injection through the skin, attributed to the flexibility of nanovesicles and the impact of ethanol on the tight junction of the lipid layer. Lin et al. formulated a co-loaded system consisting of berberine chloride and evodiamine ethosomes for the purpose of treating melanoma [99]. The results of the cell viability experiments indicated that the ethosomes that were optimized had an enhanced inhibitory effect on B16 melanoma cells. Moolakkadath et al. prepared a binary ethosomal gel formulation containing fisetin for the purpose of treating skin cancer through dermal application on mice exposed to ultraviolet radiation [100]. The results of the in vivo investigation demonstrated that mice who received pre-treatment with fisetin binary ethosomal gel had a notable reduction in the levels of TNF-α and IL-1α in comparison to the mice that were solely exposed to UV radiation. Furthermore, the group of mice treated with binary ethosomal gel had a lower percentage of tumor incidence (49%) compared to mice treated with UV only (96% tumor incidence). Cristiano et al. designed an ethosomal formulation including sulforaphane for the purpose of treating skin cancer [101]. The present study aimed to evaluate the anti-proliferative activity of ethosomes loaded with sulforaphane on SK-MEL 28 cells. The results demonstrated an enhanced anticancer effect when compared to the unencapsulated medication. El-Kayal et al. prepared (-)-epigallocatechin-3-gallate-loaded ethosomes and transethosomes for the treatment of skin cancer [102]. These two formulations showed an inhibitory effect on the epidermoid carcinoma cell line A431 and also reduced tumor size in mice. Bragagni et al. developed celecoxib-loaded transfersomes and ethosomes to improve anticancer efficacy against skin tumors [103]. These two formulations significantly improved the amount of drug penetrating the skin compared to an aqueous suspension, from 6.5- to 9.0-fold for transfersomes and ethosomes, respectively. Paolino et al. prepared a paclitaxel-loaded ethosome for the treatment of squamous cell carcinoma [104]. The results of the in vitro investigation demonstrated that the application of paclitaxel-loaded ethosomes onto the skin surface resulted in enhanced absorption of paclitaxel in a model representing the outermost layer of the skin (stratum corneum–epidermis membrane). Furthermore, this dermal application also led to greater anti-proliferative and anti-apoptotic effects of paclitaxel in DJM-1 cells as compared to the effects observed with the free form of the drug. In addition, the researchers created a new transcutaneous tumor vaccine patch (TTVP) using electrospun silk fibroin and polyvinyl alcohol nanofibrous patches. This patch included mannosylated polyethyleneimine-modified ethosome. The percutaneous injection of the Eth-PEIman chemical specifically targeted dendritic cells, inhibiting B16F10 tumor development. TTVP and aPD-1 also had a synergistic anti-melanoma effect. This effect is due to increased CD4+ and CD8+ T cell infiltration and IL-12 production in tumor tissue. This study’s findings are shown in Figure 7 [105]. Nayak et al. prepared a bioengineered ethosome with AgNPs and Tasar silk sericin proteins. This formulation was tested for treating non-melanoma skin cancer. Sericin helps wound healing by adding functional groups to AgNPs and chitosan. The main role of ethosomes is to transport encapsulated medicines. Silver nanoparticles (AgNPs) then rapidly produce reactive oxygen species (ROS), which disrupt cancer cell homeostatic equilibrium and degrade mitochondria and DNA machinery; the results are shown in Figure 8 [106]. The applications of ethosomes as transdermal delivery systems for anticancer drugs are shown in

Table 2. Examples of applications of ethosomes as transdermal delivery systems of anticancer drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Mitoxantrone (MTO)	Thin film dispersion method	Anti-melanoma	Ethosomal gel	The calreticulin membrane translocation of B16 cells ↑ (compared with MTO solutions)	[57]
Vismodegib (VMD)	Hot method	Basal cell carcinoma	Binary ethosomal gel	Anti-tumour activity (papilloma number and diameter) ↑ (compared with oral VMD and VMD-loaded ethosome gel containing 0% IPA) VMD permeated in the epidermis ↑ (compared with VMD-loaded ethosomal gel containing 0% IPA)	[97]
Cytarabine	Thin layer evaporation	Acute myeloid leukemia (AML)	Ethosomes	Percutaneous penetration of cytarabine ↑	[107]
Berberine chloride and evodiamine	The single step injection technique	Melanoma	Ethosomes	The inhibitory effect on B16 melanoma cells ↑	[99]
Fisetin	The thin-film hydration method	Skin cancer	Binary ethosomal gel	TNF-α ↓, IL-1α ↓, tumour incidences ↓ (compared to the mice exposed to UV only)	[108]
Sulforaphane	The ethanol injection method	Skin Cancer	Ethosomes	Anticancer activity on SK-MEL 28 after 24 h ↑ (compared with free drug)	[101]
(-)-epigallocatechin-3-gallate	Thin film hydration technique	Skin cancer	Ethosomes and transethosomes	Tumor sizes, glutathione, superoxide dismutase, catalase and lipid peroxidation ↓ an inhibitory effect on epidermoid carcinoma cell line A431	[109]
Celecoxib	Thin layer evaporation technique	Anticancer	Transfersomes and ethosomes	Drug penetration ↑ (compared with suspension and liposomes)	[103]
Paclitaxel	The ethanol injection method	Squamous cell carcinoma	Ethosomes	The anti-proliferative and anti-apoptotic activity ↑ (compared with the free drug)	[104]
Transcutaneous tumor vaccine/anti-programmed death-1 monoclonal antibody	The thin layer evaporation Method	Transcutaneous immunization (inhibit melanoma)	Electrospun silk fibroin and polyvinyl alcohol composite nanofibrous patch loaded with mannosylated polyethyleneimine-modified ethosome (Eth-PEIman) (TTVP)	Target dendritic cells (DCs) and induce DC maturation; inhibit the growth of melanoma; the combined of the TTVP and anti-programmed death-1 monoclonal antibody (aPD-1) produced a synergistic antitumor effect (the infiltration of more CD4+ and CD8+ T cells in the tumor tissues ↑, IL-12 ↑)	[105]
AgNPs and tasar silk sericin proteins	The ethanol injection method	Non-melanoma skin carcinoma	Bioengineered ethosomes	AgNPs stimulate the production of ROS, alter the ΔΨm and trigger a cascade of events for apoptotic and necrotic cell death, break the DNA double helix	[106]

Note: “↑”: increase; “↓”: decrease.

.

8.3. Delivery of Anti-Psoriasis Drug

The chronic, non-infectious autoimmune skin disease psoriasis has red, scaly plaques. Ethosomes may improve the efficacy and reduce the side effects of psoriasis treatments. Fathalla et al. created liposomal and ethosomal Pluronic^® F-127 gels with anthralin. These formulations were then tested for psoriasis efficacy and safety. The clinicaltrials.gov study ID was NCT03348462. Liposomes and ethosomes had average PASI changes of −68.66% and −81.84%, respectively, after treatment. Ethosomes were more effective than liposomes, according to these studies. No negative effects were found in either group. Anthralin ethosomes may treat psoriasis [64]. Negi et al. prepared an ethosomal hydrogel with thymoquinone as an anti-psoriatic agent in a mouse tail model. Compared to Nigella sativa extract, thymoquinone alone, and tazarotene gel, thymoquinone-loaded ethosomal gel had higher orthokeratosis and drug activity rates [110]. For simultaneous psoriasis treatment, Guo et al. prepared a unique drug delivery method. They created Cur@GA-TPGS-ES multifunctional ethosomes using curcumin (Cur) loaded with glycyrrhetinic acid-D-α-tocopherol acid-polyethylene glycol succinate (GA-TPGS). Cur@GA-TPGS-ES was effective when applied topically to imiquimod-induced psoriasis mice. Curcumin inhibited inflammatory infiltration, GA had glucocorticoid-like effects, and d-alpha-tocopheryl polyethylene glycol 1000 succinate had anti-lipid peroxidation capabilities [111]. The applications of ethosomes as transdermal delivery systems of anti-psoriasis drugs are shown in

Table 3. Examples of applications of ethosomes as transdermal delivery systems of anti-psoriasis drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Psoralen	The ethanol injection method	Psoriasis	Ethosomes	Biocompatibility ↑ (compared with free drug)	[19]
Anthralin	The thin-film hydration method	Psoriatic	Ethosomal gel	Psoriasis Area and Severity Index (PASI), liposomes: 68.66%, ethosomes: 81.84%; no adverse effects	[64]
Thymoquinone	Cold method	Psoriasis	Ethosomal gel	The % Orthokeratosis and % drug activity ↑ (compared with other studied test formulations)	[110]
Curcumin	The ethanol injection method	Psoriasis	Multifunctional ethosomes	Synergistic anti-inflammatory effects, glucocorticoid-like effects and anti-oxidative effects	[111]

Note: “↑”: increase.

.

8.4. Delivery of Anti-Hypertrophic Scar (HS) Drug

A hypertrophic scar (HS), a common and unavoidable problem after cutaneous skin injury, has a much thicker fibrotic dermis than normal skin. HS management is clinically challenging. Ethosomal vesicles are a novel way to improve hypertrophic scar treatment.

Yu Z. et al. developed novel nano-photosensitizer IR-808-loaded nanoethosomes (IR-808-ES) to enhance synergistic transdermal photodynamic/photothermal therapy (PDT/PTT) for improving the therapeutic efficacy of an HS. The results showed that IR-808 hydroalcoholic solution (IR-808-HA) gel and IR-808-ES gel were uniformly distributed throughout the dermis in the IR-808-ES group after topical administration and accumulated in HS tissues. In the IR-808-HA group, IR-808 accumulated in the epidermis mainly because of its lipid solubility due to the disruption of lipid organization in the SC by ethanol. Twelve times more IR-808 accumulated in the dermis in the IR-808-ES group than in the IR-808-HA group, suggesting a significant transdermal drug delivery capacity of IR-808ES. Furthermore, in vivo delivery histology also observed that IR-808-ES crossed dense collagen fibers into the deep dermis, possibly due to the significant deformability and fluidity of the vesicle membrane and the intercellular pathway for transdermal permeation. The intact ES structure after transdermal permeation played a key role in ameliorating the PDT/PTT effect and inducing HSF apoptosis [112]. Mao et al. prepared 65 nm-diameter 5-fluorouracil (5-FU) ethosomes. Ethosomes with fluorescence penetration could penetrate the deep dermal layer of hypertrophic scars [113]. Zhang et al. demonstrated that 24 h 5-FU penetration into an HS and skin was as follows: ethosomes via HS (E-Scar) > hydroethanolic solution via an HS (H-Scar) > ethosomes via skin (E-Skin) > hydroethanolic solution via skin; ethosomes are very efficient vehicles for penetrating an HS [114]. Wo et al. also prepared ethosomal gels loaded with 5-FU (5-FU EGs). Using CLSM, rhodamine-6G-labeled ethosomal gels penetrated into the deep dermis of an HS within 24 h in the rabbit ear hypertrophic model. In addition, the Scar Elevation Index (SEI) value of the 5-FU EG group was lower than that of the 5-FU PBS gel; 5-FU EGs may be a suitable drug for hypertrophic scarring [115].

In hypertrophic scar treatment, a fractional CO₂ laser may improve drug absorption. A CO₂ fractional laser increases the stratum corneum permeability of 5-FU-encapsulated ethosomes according to a study. Permeability increased rapidly due to this improvement. The combined group showed significantly a decreased relative thickness and scar elevation index (SEI) of rabbit ear hypertrophic scars after 7 days of therapy compared to the group treated with 5-FU encapsulated ethosomes. Furthermore, the process by which HSs (hypertrophic scars) improved was associated with the decrease in collagen I/III levels and the suppression of TGF-β1 expression [116]. Xie et al. prepared a hyaluronic acid-containing ethosomal (HA-ES) formulation and used RB as a model medication. HA-ES-RB penetrated the deepest dermis layer better than ES-RB. HA-ES-RB’s transdermal drug delivery efficacy is due to its small size, hyaluronic acid’s hydration capabilities, and liposomal carriers’ ability to target the skin and appendages. The HA-ES delivery system was biocompatible because it did not affect normal cells [117]. The applications of ethosomes as transdermal delivery systems for anti-hypertrophic drugs are shown in

Table 4. Examples of applications of ethosomes as transdermal delivery systems of anti-hypertrophic scar drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Near-infrared heptamethine cyanine dye (IR-808)	Thin layer evaporation technique	Hypertrophic scar	Ethosomal gel	The special structure of IR-808 aggregate distribution in the ES lipid membrane enhances ROS gene- ration and hyperthermia.	[112]
5-fluorouracil	The ethanol injection method	Hypertrophic scar	Ethosomes	E-Scar > H-Scar > E-Skin > H- Skin	[114]
5-fluorouracil	The ethanol injection method	Hypertrophic scar	Ethosomal gel	SEI ↓ (compared with 5-FU Phosphate Buffered Saline gel).	[115]
5-fluorouracil	The film dispersion	Hypertrophic scar	Ethosomal gel	collagen I/III ↓ TGF-β1 expression ↓	[116]
5-fluorouracil	The ethanol injection method	Hypertrophic scar (HS)	Ethosome	ALA and AuNPs penetration ↑ (compared with hydroethanolic solution).	[117]

Note: “↑”: increase; “↓”: decrease.

.

8.5. Delivering Drugs for Chronic Diseases

Chronic diseases are the primary contributor to global mortality, sometimes evading early detection and typically not being detected until severe stages [118]. The treatment and application of ethosomes in chronic diseases is beginning to attract the interest of researchers. Ammar et al. prepared ethosomes loaded with vardenafil hydrochloride. CLSM studies demonstrated their ability to deeply penetrate rat skin. In addition, C_max was lower, T_max was delayed, and AUC_0–24h was greater in adults and geriatrics after the transdermal application of the ethosomal system [119]. Ibrahim et al. prepared a carvedilol-loaded ethosomal gel for the treatment of hypertension. Compared with pure carvedilol gel, the ethosomal gel showed a significant reduction in mean arterial pressure in rats (p < 0.01) at the second hour of the experiment (146.11 mmHg) and a further significant reduction at 6 h (p < 0.001) (98.88 mmHg) [56]. Liu et al. prepared a transdermal ligustrazine ethosomal patch for the treatment of myocardial ischemia. The drug patch can maintain a steady blood drug concentration, increase medication availability, and shorten drug administration. These compounds may reduce hemorheological parameters associated with myocardial ischemia in rats and protect acutely ischemic and ischemia-reperfusion-wounded myocardium [120]. Bhosale et al. prepared ethosomes filled with repaglinide (RPG) for diabetes treatment. When applied to excised rat skin, the ethosome penetrated 64% to 97% of the dose better than the free drug and its hydroalcoholic solution. Researchers found that RPG has a much longer anti-diabetic effect than oral doses [121]. Shi et al. prepared a transdermal ethosomal system containing ligustrazine phosphate (LP) as a potential therapeutic approach for the management of Alzheimer’s disease. The findings of the study indicated that the LP ethosomal system exhibited superior penetrating ability and drug deposition in the skin compared to the aqueous system. The researchers successfully reinstated the functioning of antioxidant enzymes and the levels of MDA in the brains of amnesic rats to a comparable state as that of normal rats [122]. Liu et al. prepared the pharmacokinetics of intragastric, transdermal, and standard transdermal ligustrazine patches. The ligustrazine ethosomal patch group had a 2.09-fold larger area under the curve (AUC) than the oral medication group and a 2.12-fold higher AUC than the traditional patch group. Compared to oral administration, ligustrazine ethosomes had a 209.45% relative bioavailability, while the standard transdermal patch had 98.63%. This study suggests that ligustrazine ethosomal patches may improve medicine absorption and bioavailability compared to the other two alternatives [123]. Bhosale et al. prepared ethosomal carrier-based transdermal VLT delivery. The study found that transdermal ethosomal VLT delivered better and longer-lasting antihypertensive benefits to Wistar rats than oral VLT suspension. This is because the VLT penetrates Wistar rats’ skin transdermally. The ethosome solubilized epidermal intercellular lipids to penetrate the skin but did not change its cellular architecture. In conclusion, this ethosomal formulation has improved transdermal VLT absorption, making it better than oral administration for antihypertensive therapy [124]. The applications of ethosomes as transdermal delivery systems of drugs for chronic diseases are shown in

Table 5. Examples of applications of ethosomes as a transdermal delivery system of chronic disease drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Vardenafil hydrochloride	Ethanol injection technique	Pulmonary arterial hypertension	Ethosomes	Cmax values ↓, delayed Tmax estimates	[119]
Carvedilol	The ethanol injection Method	Antihypertensive	Ethosomal gel	Mean arterial pressure of rats ↓ (146.11 mmHg) after 6 h ↓ (98.88 mmHg).	[56]
Ligustrazine	The ethanol injection Method	Anti-myocardial ischemia	Ethosomal patch	The scope of myocardial infarction induced by long-term ischemia ↓.	[120]
Repaglinide	The cold method	Antidiabetic	Ethosomes	Antidiabetic effect of time ↑ (compared with the equivalent oral dose).	[121]
Ligustrazine phosphate	The ethanol injection method	Alzheimer	Ethosome	Recover the activities of the antioxidant enzymes and MDA (compared with the aqueous one)	[122]
Ligustrazine	The ethanol injection-sonication method	Angina pectoris	Ethosomal patch	Drug absorption and bioavailability ↑ (Compared with conventional ligustrazine)	[123]
Valsartan	The ethanol injection method	Antihypertensive	Ethosomes	Antihypertensive activity ↑ (comparison to orally administered VLT suspension)	[124]

Note: “↑”: increase; “↓”: decrease.

.

8.6. Delivery of Other Drug from Ethosomal Systems

Ethosomes have also been used to treat other conditions such as acne, androgenic alopecia, malaria, ageing, fever and pain, menopausal syndromes, acne vulgaris, UV radiation, and so on (

Table 6. Examples of applications of ethosomes as transdermal delivery systems of other drugs.

Drug	Preparation Methods	Application	Form/Type	Remarks	References
Cryptotanshinone	Ethanol injection technique	Acne	Ethosomal gel	Transdermal flux 2.5 times and skin deposition 2.1 times (compared with conventional gel)	[8]
Finasteride (FIN)	Cold method	Androgenic alopecia	Ethosomes	Permeation across rat skin and frontal scalp skin of human cadaver ↑ (compared with the unencapsulated FIN)	[127]
Triamcinolone acetonide	Infusion method	Atopic dermatitis	Binary nanoethosomes	Topical delivery ↑, EE ↑, and stability ↑ (compared with reference ethosomal vesicles)	[23]
Artemisinin	Injection method.	Antimalarial	Ethosomal cataplasm	The accumulated permeation quantity 1.57 times (compared with conventional cataplasm)	[39]
Tramadol	By thin layer evaporation technique	Analgesic	Ethosomal gel	Increase bioavailability (7.51 times)	[125]
Testosterone propionate (TP)	Ethanol injection method	Testosterone deficient therapy	Ethosomal gel	Transdermal flux: 7.64 ± 1.4 mg/cm2/h ↑ Lag time of across rat skin ↓ (compared with other formulations)	[128]
Zolmitriptan	The ethanol injection Method	Migraine	Nanoethosomes	Size: (171.67 nm) EE: (66%)	[129]
Rosmarinic acid	The thin-film hydration Method	Anti-aging	Ethosomes	Size: (138 ± 1.11 nm) EE: (55 ± 1.8)%	[53]
Lidocaine	The modified ethanol injection method	Anesthetics	Nanoethosomes	Size: 105.4 ± 7.9 nm, Zeta: −33.6 ± 2.4 mv, EE: 40.14 ± 2.5%	[130]
Thymosin β-4	Ethanol infusion	Wound repair	Ethosomal gel	The percutaneous absorption protein drugs ↑ recovery time ↓ (compared with the free drug)	[131]
Eugenol and cinnamaldehyde	The ethanol injection method	Ulcerative colitis	Ethosomes	increasing the number of ICCs and restoring the function of ICCs ↑ (compared with ethosomes)	[126]
Betahistine dihydrochloride	The ethanol injection method	Weight gain control	Ethosomal gel	H3 antagonist action and H1 agonist action, brain histamine ↑ (compared with control, placebo, and BDH gel)	[132]
Heparin	The ethanol injection method	Anticoagulant	Flexosomes	Skin permeation and bioavailability ↑ (compared with ethosomes)	[133]
Ibuprofen	The ethanol injection method	Fever and pain	Ethosomal gel	Relative bioavailability ↑ present in plasma of time ↑ (compared to the oral administration)	[134]
Vitamin K1	The ethanol injection method	Suppress pigmentation and resolve bruising	Ethosomes	Accumulation into/permeation through the skin ↑.	[135]
Buspirone	The ethanol injection method	Menopausal syndromes	Ethosomes	A Frel value of 0.89 was estimated for transdermal vs. Oral buspirone.	[136]
Phenylethyl resorcinol	Thin-film hydration method	Skin lightening	Ethosomes	Tyrosinase activity ↓ and melanin content ↓	[137]
karanjin	The film hydration method	Acne vulgaris	Ethosome-based gel	Compared to the hydro-ethanolic solution: penetration ↑, against Propionibacterium acnes and Staphylococcus epidermidis inhibition 30.0 ± 1.52 mm and 36.22 ± 0.57 mm	[138]
Cetirizine	The ethanol injection method	Atopic dermatitis	Ethosomes	Permeation flux and skin retention ↑ (compared to conventional formulations)	[139]
Melatonin	Na	Prevention of UV radiation	Ethosomal gel	Zeta: −12.4 mV to −27.4 mV EE: 49.61–78.047%	[140]

Note: “↑”: increase; “↓”: decrease.

). Feng et al. designed a modified ethosomal system using hyaluronic acid (HA) to specifically target the CD44 protein, which is known to be upregulated in inflamed psoriatic skin. This approach aimed to enhance the transport of drugs to the intended site, resulting in increased curcumin accumulation within the inflamed skin [31]. Ahmed et al. prepared an ethosomal system to enhance the transdermal activity of tramadol to significantly prolong the analgesic effect [125]. Yongtai Zhang et al. prepared EUG/CAH-loaded HA-immobilized ethosomes (HA-ES) with the aim of possessing excellent deformability and showed improved efficacy against UC compared to ES; the results are shown in Figure 9 [126].

9. Discussion and Prospects

Ethosomes, a novel drug carrier with numerous benefits such as enhanced drug penetration into the skin, reduced dosage and side effects, and improved user-friendliness, have attracted significant attention in both pharmaceutical and cosmetic fields. This paper reviews the research progress on the types, mechanisms of action, preparation methods, influencing factors, and clinical applications of ethosomes, aiming to provide a reference for their development and application. Compared to traditional liposomes, ethosomes exhibit better encapsulation efficiency, exhibit higher skin penetration potential, and can overcome the challenge of low macromolecular drug transport efficiency. Despite rapid development in recent years, ethosomes still face several challenges. Ethosomes are less stable during long-term storage, affecting their drug content. The particle size of ethosomes, ranging from ten to several hundred nanometers, is a key factor affecting their skin penetration. Therefore, a suitable particle size is likely to improve transdermal efficiency and drug delivery. These factors will be the main challenges and opportunities for future research in this field. It is hoped that more researchers will conduct studies in this field, enabling ethosomes to realize their potential as a multifunctional material in material science and bioengineering. Moreover, ‘‘Chemistry’’ plays a crucial role in ethosomal technology. Continuous innovation can lead to more opportunities and breakthroughs in drug delivery. Therefore, it is worthwhile to discuss how chemistry will advance ethosomal technology and applications.