INTRODUCTION:

Skin is a constitutional and the most easily manageable organ of the body which accounts around 15% of total adult body weight. It implements multiple roles such as defending or shielding against peripheral somatic, chemical, biological assailants and anticipation of water loss. It also plays a major role in thermoregulation⁽¹⁾. Skin is encircled by three layers i.e. Epidermis, dermis and hypodermis. Epidermis being the outer layer of skin consists of the Stratum corneum which pretends to be a resistible barrier to drug penetration across the skin.

This phenomena confines the external application i.e. rate of drug reaching the blood. Distinctive carriers are needed to warfare the barrier of skin for the drug molecules to be delivered into the systemic circulation with diverse physicochemical properties⁽²⁾. The skin offers a pain-free interface for systemic administration of drugs and former molecules of therapeutic value via transdermal delivery⁽³⁾^,⁽⁴⁾^,⁽⁵⁾.

Among the growing demand of therapies with good patient adequacy, the most emerging delivery system is the transdermal drug delivery system when compared to the customary drug delivery has voluminous number of advantages inclusive of lower dosage of drugs, promoting patients' compliance and convenience with its non-invasive and averting gastrointestinal disturbances and first pass metabolism⁽⁶⁾^,⁽⁷⁾. Non-invasiveness being the foremost advantage empowers administration of a drug for a protracted treatment repeatedly at the same region. Stratum corneum is the most arduous hurdle for the drugs to elapse through the skin. Habitually drugs with molecular weight ˂ 500 Daltons i.e. highly lipophilic drugs diffuse via the hydrophobic stratum corneum⁽⁸⁾. In order to surpasses this barrier multitudinous techniques are available complex physical enhancement strategies, such as iontophoresis, sonophoresis, microneedle, and electroporation, and lipid vesicular systems such as emulsions, micro emulsions, and liposomal-based delivery systems, ethosomal drug delivery systems⁽⁹⁾^,⁽¹⁰⁾^,⁽⁵⁾.

Ethosome is a leading-edge vesicular system which was developed by Touitou et al with good attributes combined with high durability. Ethosomes are encircled with three main components such as the lipid which acts as the spine of this delivery system in addition to water and ethanol with enormous number of chemical applications. Ethanol is an adjuvant which imparts flexibility to permeate promptly through the deeper layer such as the stratum corneum of human skin with a steady state flux of 1mg/cm2/h⁽¹¹⁾^,⁽¹²⁾. The high concentration of ethanol directs its exclusivity where the lipid membrane is packed less tightly than conventional vesicles. It has equivalent stability in which ethanol has proven to increase the drug distribution in the stratum corneum ad also has malleable structure⁽¹³⁾^,⁽¹⁴⁾. Ethanol increases the flexibility and fluidity of lipid and loosens the tight junction of stratum corneum by interacting with the polar head region of lipid molecules which reduces the melting point of lipid which thereby increases the permeability of skin and also the penetration of disorganized lipid bilayers. Ethanol concentration is also responsible for stearic stabilization because of its negative charge which leads to deeper drug penetration in skin with high transdermal flux. Since incorporation of high ethanol concentration confers a negative charge to the liposomes which causes the size of vesicles to decrease, and that in turn eventually leads to enhanced bioavailability of therapeutic agents⁽¹⁵⁾^,⁽¹⁶⁾.

Ethosomes are able to imbue through pores within stratum corneum by eminent and self-amplifying deformability. Ethosomes with the size range of 200–300nm can pierce in intact skin with ease. These vesicles grant access to a meticulous transdermal delivery system and furthermore aid for the solubilization hindrance of drugs that are less soluble. Though ethosomal systems are abstractly refined, they are categorized by efficacy, safety and easiness in fabrication – a combination that can vastly inflate their application⁽¹⁷⁾. Through the skin and cellular membranes the bioactive molecules can be delivered efficiently by one of the prominent approach such as ethosomal carrier which brings about copious challenges and prospects for certain upcoming research work and imminent progression in novel upgraded therapies. Ethosomal fabrication encompasses pharmaceutically sufficient excipients which relies on modest scale up and does not necessitate any elaborative measures⁽¹⁸⁾. Ethosomes are decomposable and accustomed biologically which renders more prominent surface area signifying that condensed size of the vesicles are equated to other vesicular systems⁽¹⁹⁾^,⁽²⁰⁾^,⁽²¹⁾.

Figure 1. Structure of ethosomes

ADVANTAGES OVER LIPOSOMES:

Ethosomes bid a promising tactic for improving skin drug delivery and have engrossed much importance in recent years due to their prominent vantages⁽²²⁾^,⁽²³⁾. Several analyzes over the past epoch have extensively documented the benefits of ethosomes as carriers for local delivery of drugs over conventional liposomes and ultraflexible liposomes which take account of the following

· Transportation of active agents by ethosomes via the stratum corneum into deeper strata of the skin more meritoriously and subsequent retention in the skin layers than traditional liposomes.

· Compatibility with barriers is found to be better compared to ultraflexible liposomes containing bilayer fluidizing agent such as sodium cholate.

· Ethosomal systems were found to be superordinate in delivering drugs and fluorescent probe over the skin in terms of both extent and deepness when equated to liposomes and hydroalcoholic solution.

· Compared with liposomes, ethosomes could effectively conveyance drugs through the SC into deeper layers of skin, even into the blood circulation.

· Ethosomes are intended to escalate the transdermal perviousness of loaded drug as paralleled to liposomes or the ethanolic drug solution⁽²⁴⁾^,⁽³⁾^,⁽²⁵⁾.

MERITS OF ETHOSOMES:

· Ethosomes are convenient for use and harmlessness to skin.

· Ethosomes delivers eminent patient acquiescence as they can be formulated in semisolid dosage forms (Gel or Cream) in divergence to impediments associated with iontophoresis and phonophoresis.

· Ethosomal system abides no outsized scale drug development risk since the toxicological description of ethosomalelements is finely accredited is scientific literature.

· The ethosomal vector has been shown to be capable of augmenting intracellular delivery of both molecules that have affinity towards water and lipids, and to escalate the permeation of an antibiotic peptide⁽²⁶⁾⁽²⁷⁾.

DEMERITS OF ETHOSOMES

· Input through bolus type cannot be achieved by ethosomal formulation because it is designed for slow and prolonged delivery of drug.

· In both aqueous and lipid environment sufficient amount of solubility is required for the drug to reach the systemic circulation and dermal microcirculation.

· Molecular size of drug should be in such a way that it is suitable for transdermal delivery.

· Adhesives maynot be suitable for all types of skin.

· Expensive

· Yield will be very poor.

· Chances of dermatitis or irritation in skin due to use of permeation enhancers and other excipients for better delivery of drug.

· Product wastage while transferring organic media to water media⁽²⁶⁾^,⁽²⁷⁾.

PREPARATION OF ETHOSOMES⁽²⁸⁾^,⁽²⁹⁾^,⁽³⁰⁾^,⁽³¹⁾^,⁽³²⁾^,⁽³³⁾:

Mechanical dispersion method:⁽³⁴⁾

Soy PC was dissolved in Chloroform; Methanol mixture in 2:1 ratio in a wholly desiccated RB flask

Using rotary evaporator the organic solvent was detached (90 rpm – 15 min at 45°C)

A thin lipid film is obtained in the surface of flask which was kept under vacuum overnight to detach the traces of solvent

The dried film was hydrated using a hydroethanolic mixture in an orbital shaker (100-120 rpm – 1h) at room temperature

The formulation was sonicated (3 cycles – 5

Figure 2. Preparation of mechanical dispersion method

Soy PC + Permeation enhancer are dissolved in ethanol and pg (propylene glycol) in a concealed glass bottle (stirred at 1500 rpm)

The above mixture is heated up to 30°C in a water bath

Water is added to the prepared mixture and stirred continuously

Using a probe sonicator the above preparation is the sonicated (3 cycles – 10 min)

The formulation is stored in the refrigerator

Figure 3. Preparation of ethosomes by hot method

Soy PC is dispersed in water and placed in water bath at 40°C till a colloidal suspension is attained

Ethanol + PG (Popylene glycol) is heated at 40°C

The above mixture is added to the pospholipid mixture drop wise by continuously stirring (Mechanical or Magnetic stirrer

The drug is dissolved based on its hydrophilic or hydrophobic nature into either of the organic or aqueous phase

The preparation is the sonicated (3 cycles – 5 min at 4°C)

The preparation is homogenized using high pressure homogenizer (at 15000 psi) to get uniform nanosized ethosomes

Figure 4. Preparation of ethosomes by hot method

TYPES OF ETHOSOMAL SYSTEM⁽³⁾:

Ethosomes are classified into three types based on its composition.

Classical ethosomes:

These ethosomes are nothing but the modification of liposomes. They comprise of high concentration of ethanol (aroun 45% w/w), phospholipids and water. These ethosomes were considered to be superordinate to liposomes for percutaneous delivery due to their smaller size and better entrapment efficiency. The stability and penetration properties of classical ethosomes were more proficient compared to liposomes. Drugs with MW in the range of 130.077 Da – 24kDa were encapsulated in the classical ethosomes.

Binary ethosomes:

Zhou et al introduced the binary ethosomes. The development of these ethosomes were made possible by addition of an alcohol type to the classical ethosomes. The frequently used alcohols to these binary ethosomes are Isopropyl alcohol and Propylene glycol.

Transethosomes:

Song et al acquainted these new generation ethosomes called transethosomes in the year 2012. These ethosomes were similar to classical ethosomes with the same components except for the addition of a penetration enhancer or surfactant. These ethosomes were brought into consideration to add its advantage of the already existing transferosomes which are nothing but deformable liposomes and classical ethosomes as a single formula in terms of transethosomes. Transethosomes are found to be superordinate than the classical ethosomes. Characteristics of ethosomal system is made better by the addition of various edge activators or penetration enhancers. The drugs with a MW in the range of 130.077 Da up to 200 – 325k Da can be encapsulated by transethosomes⁽³⁾^,⁽³⁵⁾.

Figure 5. Types of ethosomes.

MECHANISM OF DRUG PENETRATION:

Stratum corneum has two probable routes which encompasses intercellular and transcellular pathways. Drug delivery into skin via locally imposed vesicles is influenced by oodles of divisors. Vesicles that are more modest in size penetrate substantially into the deeper layers of skin. The size of ethosomes is affected by the concentration of phospholipid and ethanol. As the size of ethosomes diminishes, the concentration of ethanol is observed to escalate. Ethosomes permeate via transcutaneous pathway of skin which comprises of Stratum corneum and open hair follicles. The vesicles are fragmented in the upper layer of skin in the course of transcutaneous permeation which allows penetration of therapeutic agents progressively although the epidermis retains the phospholipid. This phenomenon is based on the interdependent effects of the lipid and ethanol to escalate the ethosome permeation. At corporeal temperature the multilayered lipid Stratum corneum is organized and packed compactly. Ethanol deeds as an incursion enhancer thereby escalating the fluidity of lipid layer which abridges the lipid density in skin and the arrangement of lipid bilayer of skin is also bothered. The bi-layered vesicle is made soft and ductile by the use of ethanol for easy penetration into skin. Amalgamation of these vesicles will expel the drug into layers that are deep in skin. Therefore the use of ethanol escalates the fluidity and probable ethosomal interactions on the vesicles and Stratum corneum for more prominent drug delivery⁽³⁶⁾⁽³⁷⁾.

ETHOSOME MECHANISM FOR THE SKIN DELIVERY

The penetration of drug falls out in two phases:

1. Ethanol effect

2. Ethosomes effect

Ethanol effect:

Ethanol via the skin deeds as an incursion enhancer. Ethanol insights into the intercellular lipids and the fluidity of lipid cell membrane escalates ad interim the cell membrane density of lipid multilayer diminishes.

Ethosome effect:

When the fluidity of cell membrane lipid is intensified by the ethanol of ethosomes, the perviousness of skin also escalates. Ethosomes infuse deep inside the skin layers and gets merged with the lipids of skin and in so doing the drug is being liberated into the deep strata of skin⁽²⁷⁾⁽³⁷⁾.

EVALUATION PARAMETERS OF ETHOSOMES:

1. VESICLE MORPHOLOGY:

The morphology of ethosomal system are determined by Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM) in which the samples are stained negatively with a solution in water i.e. aqueous solution. Staining of solution of ethosomes was done using a microscopic grid which is coated with carbon. Blotting is done to detach the superfluous solution. It is then dried and the observation of vesicles is done using TEM or SEM⁽³⁷⁾^,⁽³⁸⁾.

2. VESICLE SIZE AND SIZE DISTRIBUTION:

Vesicles in the ethosome formulation are usually assessed with dynamic light scattering (DLS) by the use of a computerized system and PCS (photon correlation spectroscopy)⁽³⁷⁾^,⁽³⁹⁾. Constituents in the formulation influence the series of sizes between microns and nanometers,⁽¹¹⁾^,⁽¹²⁾^,⁽³³⁾^,⁽⁴⁰⁾.

3. PERCENT ENTRAPMENT EFFICIENCY:

Measuring the entrapment efficiency is important as it endows the prolonged release features of ethosomes⁽²⁴⁾. The entrapment efficiency is usually calculated by methods as follows:

3.1 Ultracentrifugation:

3.2 Dialysis:

3.1 Ultracentrifugation:

It contains two segments in which the preparation of vesicle in the 1^st segment is set aside overnight and at the intended rpm and time, it is exposed to ultracentrifugation while the other segment contains the pure drug which is assayed using methods such as HPLC to measure the entrapment efficiency by using the formula below⁽³⁷⁾:

EE = entrapment efficiency

Dₜ = the quantity of drug added theoretically

Dₛ = the quantity of drug present in the supernatant

3.2 Dialysis:

Polymers such as cellulose acetate are used for the preparation of dialysis bag which is set aside for 1h in a saline solution to make sure that the membrane is wholly wetted after which the deliberate quantity of vesicles that are loaded with drug are located in the bag, the vesicles are then moved to the PBS (phosphate buffer saline) of 500ml at a pH of 7.0.. Using a magnetic stirrer, the mediums are stirred and sink condition is maintained by withdrawing the aliquots with similar amount at time intervals from the medium receiving and replacing the solution of PBS with equal amount. HPLC is used for assessing the drug content of samples⁽³⁷⁾⁽⁴¹⁾. The entrapment efficiency is then calculated using the above formula⁽⁴²⁾^,⁽⁴³⁾^,⁽³²⁾^,⁽⁴⁴⁾.

4. ZETA POTENTIAL:

Development of charge between the liquid medium and its solid surface at the interface is the Zeta potential. Zeta potential is assessed by using Zeta meter or Zeta sizer. The unit of Zeta potential is denoted by Milli Volts⁽¹³⁾^,⁽⁴³⁾^,⁽⁴⁴⁾.

5. PERMEATION DISTINCTIVENESS:

Ethanol has been well known for its penetration properties. Two effects are ascribed by the penetration properties of which is enriched by the generation of ethosomal characteristics which are flexible and are provided by the synergistic effect between the lipids in skin, vesicles and ethanol which proves that the penetration enhanced by ethosomes is much better than the penetration enhanced by ethanol solely. The two effects are as follows

5.1 Push effect:

Escalation in thermodynamic action owing to the vaporization of ethanol

5.2 Pull effect:

Ethanol reduces the barriers present in the dermatological tissue which in turn escalates the permeation of drug⁽³⁷⁾.

6. SURFACE TENSION MEASUREMENT:

Du Novy ring tensiometer is a ring method which used for measuring the surface tension of a drug⁽³⁹⁾.

7. PHYSICAL STABILITY:

In the formulation of ethosomes, cholesterol bids a foremost role in its distribution in the whole system and aggregation takes place in the non-existence of cholesterol. When ethosomes are retained in the gel form, cholesterol is found to be stabilized in the bilayer and the flexibility of ethosomal vesicles is made definite due to the eminent level of ethanol in ethosomal formulation and rational quantity of cholesterol makes sure of its stability. The stability of ethosomal suspension during a long storage period is secured by freeze drying method⁽¹³⁾^,⁽⁴²⁾.

8. TRANSITION TEMPERATURE:

Differential scanning calorimetry is used for detecting the transition temperature of the ethosomal system⁽³⁹⁾.

9. VESICLE - SKIN INTERACTION STUDY:

The interaction between the skin and vesicle can be studied using Fluorescence microscopy, Scanning electron microscopy or Transmission electron microscopy. Fluorescence microscopy is done with the same protocol as that of SEM and TEM⁽¹¹⁾^,⁽³³⁾.

ETHOSOME APPLICATIONS:

Ethosomes for percutaneous delivery:

Ethosomes have been proven to have a proficiency of greater than 65% to deliver the drug with a propriety to penetrate the skin of human remuneratively. Ethosomes are reported to be an efficient vehicle for the passage of drug into strata and their efficacy in managing numerous skin disorders. A comparative study was done to determine the penetration properties of Minoxidil invitro by using either hydroethanolic or ethanolic or phospholipid ethanolic micella solution of minoxidil in which the excipients used were water and phospholipid. In the end of study it was observed that the permeability of minoxidil was gradually increased⁽³⁷⁾.The probability of ethosomes that are loaded with ketoprofen through the skin in divergence to hydroethanolic solution was evaluation using Soya phosphatidyl choline as an excipient. In the permeation study conducted in the skin of human, it was proven to have an escalated permeation of drug and the transdermal flux was also found to be higher in case of formulations containing ethosomes than the hydroethanolic solution. In patients with candidiasis a study was performed to determine the efficacy of ethosomes which was encapsulated with fluconazole against liposome loaded gel, a formulation available in the market and the hydroethanolic solution. The invitro permeation study revealed that the permeation of ethosomes were twice than the permeation of liposomes meanwhile the permeation of ethosomes were thrice than the hydroethanolic solution. The ethosome fluidity was much greater when compared to liposomes which was demonstrated using DSC study⁽³⁶⁾⁽²⁶⁾^,⁽⁴⁵⁾.

Ethosomes in DNA delivery:

Skin is an immunologically active organ and allows gene expression which acts as an eminent disputing barrier through which microorganisms pass over the periphery of the body. It helps in the use of DNA delivery of molecules in cells of skin that are encapsulated with protein i.e. GTP- cytomegalovirus (CMV) focused by transfecting construct into ethosome for gene expression which is also found to be a requisite application of ethosomes. CLSM Studies have shown that the application of the ethosomal formulation on the dorsal side of the CD-1 male mice which is 5-week old for 48h which then was removed from the skin after 48h of penetration has aided effective drug delivery. Thus the Green fluorescent protein- Cytomegalovirus-driven transfecting construct allowed an effective gene expression into cells of skin.

Ethosomes in Hormone delivery:

Oral dosage form of the hormone delivery rises up with numerous side effects which includes depleted oral BA, side effects related to dose dependency and first pass metabolism in a higher rate. Besides these side effects, the oral form of hormonal delivery has a high impact on the compliance of patients. Studies were performed on testosterone loaded ethosomes in divergence to transdermal testosterone patch for percutaneous delivery which discovered the possibility of hormonal delivery on the skin of a rabbit which established skin permeation of the ethosomal formulation of testosterone to be 30 times greater. Drug deposition of the formulation containing ethosomes was significantly more eminent (p< 0.05). On comparison between the testoderm (18.32 ± 4.05µg) and testosome (130.76 ± 18.14µg) application, the Cmax and Area under curve (AUC) of testosterone have been escalated in case of testosome. Improvement in permeation of skin and bioavailability of drug was observed after the invitro and invivo studies of testosterone loaded ethosomal formulation⁽⁴⁶⁾^,⁽²⁷⁾.

Ethosomes in transcellular delivery:

Ethosomes deeds to be an effective enhancer for the delivery of drug in transcellular pathway for numerous drugs with efficacious clinical studies which thereby demonstrates the ethosomal efficacy in transcellular pathway by conducting a study on Swiss albino mice of molecules of 3T3 fibroblasts for transcellular delivery which has enormous number of physico-chemical properties of ethosomes, lipid carriers encompassing ethanol. 4-(4-diethylamino) styryl-N-methylpyridinium iodide (D289), rhodamine red dihexadecanoyl glycerophosphoethanolamine (RR) and fluorescent PC were selected as probes. CLSM and FACS studies scrutinized the permeation properties of naked mice skin and probes that were fluorescent into fibroblasts. Micrographs of CLSM demonstrated that the permeation of probes into the cells were enabled by ethosomes to which the fluorescence with greater intensity were evident. In comparison, no fluorescence was identified when it was fused into liposomes or a hydroethanolic solution. Incubation was done for 3min after which the intracellular presence was observed in three tested probes each. Experiments using Calcein which hydrophilic in nature and a lypophilic RR which was performed on naked skin of mouse was observed with improved permeation of drug with ethosome as a carrier. By utilizing the invitro method i.e. Franz diffusion cell, a permeation study for transdermal delivery was done in human hypertrophic scar (HS) and skin for 5-Fluoracil loaded ethosomes. After 24h of permeation, extent of the drug i.e. 5-fluoracil that permeated into skin was copious through HS (E-scar) in addition to a hydroethanolic solution through H-Scar skin and H-Skin, ethosomes through E-Skin⁽⁴⁷⁾^,⁽⁴⁸⁾. Confocal laser scanning microscopy was used for analyzing the permeability of ethosomes with fluorescent labelled rhodamine 6GO in skin and HS. In the study, permeation was highest in HS. Nanoparticle labelling for example quantum dots on various strata of skin scar and delivery of medicines was found to be extremely good in the ethosomes. Hence this study demonstrates that ethosomes have efficient fluorescence labelling characteristics for the quantum dots⁽³⁷⁾^,⁽³⁶⁾.

Microbial and viral activity of ethosomes for infection in skin:

Antibiotic activity of ethosomes are very efficacious for treating infections in skin. Activity of antibiotics is examined using animal models for treating infections caused in skin. A comparison study was done with erythromycin loaded ethosomes and hydroethanolic solution of erythromycin for the treatment of dermal infections on a mice which was infected by Staphylococcus aureus. It was observed that infections were healed without the growth of any bacteria in case of ethosomal erythromycin than the hydroethanolic erythromycin solution. A study was conducted by utilizing bacitracin and (FITC-Bac) i.e ethosomes loaded with fluorescently labelled bacitracin to understand the invitro and invivo mechanism of skin permeability. Fluorescent-activated cell sorting (FACS) and confocal laser scanning microscopy (CLSM) experiments were used to calculate the results. The calculated results obtained from the study confirms the drug penetration across skin is aided by ethosomes⁽⁴⁹⁾^,⁽⁵⁰⁾.

Ethosomes for infections caused by fungi and virus

Side effects of oral administration such as low absorption in the intestine (15-30%), side effects related to dose have decreased in addition it also escalates the permeation through percutaneous delivery of ACV into the outer layer of skin in which viral replication takes place for treating herpes labialis alongside ethosome loaded ACV (Acyclovir)⁽⁵¹⁾. Comparative study between market available 5% Acyclovir cream and 5% ethosome loaded acyclovir preparation was performed⁽⁵²⁾. The efficacy of ethosomes was revealed in the study for herpes infection and an innovative method for local delivery of a drug that is hydrophilic based on ethosomes such as Supra-Vir cream was demonstrated with the help of this study.

Ethosomes loaded with testosterone for deficiency in hormone:

In male hypogonadism, the male sex hormone is testosterone which is not effective in oral administration because of the poor hepatic metabolism (53). Sub-physiological and Supra physiological levels of testosterone can be obtained by IM injection, whereas testosterone injections are painful when directly injected. Henceforth the alternative approach to surpass the first pass hepatic metabolism and side effects related to IV route is the percutaneous delivery of testosterone⁽⁵⁴⁾^,⁽³¹⁾.

i. Testosome : Testoterone loaded ethosomal patch:

Comparison between the prepared patch of ethosomal testosterone i.e. testosome with the market available patch of testosterone-Testoderm™ is done by using invitro and invivo techniques for testing their efficacy.

The data gained from the above invitro study from testosterone reveals that testosterone has thirty times better permeation of skin than the market available Testoderm™. The drug quantity present in the skin was escalated upto 7 times from testosterone loaded ethosome i.e. Testosome whereas the results from invivo study showed that the values of Cmax and AUC were 2.4 and 2.2 respectively which was observed to be higher than Testoderm™.

ii. Ethosomal testosterone gel:

Evaluation of a formulation encompassing ethsomal testosterone gel is compared with the commercially available drug- Androgel®. Six point four times increase in permeation of skin was observed in the invivo study conducted in rats from the ethosomal testosterone gel which was compared with Androgel®(55).

Ethosomes for syndromes related to menopause:

Buspirone hydrochloride (BH) is a drug which has got a half-life upto 2.5h endures first pass metabolism and results in low oral absorption which in turn leads to lesser bioavailability of around 3.9% comparative to IV injection and needs dosing frequency. Though Buspirone hydrochloride is a cationic molecule with strong affinity towards water is not adequate enough for it to penetrate the skin and reach the blood at its target site. Ethosomes were intended to escalate the penetration property of BH in skin by investigating the PKPD efficacy for treating the menopause syndrome by using animal models with anxiety and hot flash (56). Henceforth ethosome loaded BH was proven to be harmless and efficient for syndromes related to menopause(57), (58).

Treatment of Parkinsonism by using Ethosomes:

A cationic anti-MI muscarinic drug- Trihexphenidyl (THP) is used for Parkinsonism disorder. 2% and more elderly people are being affected by Parkinsonism.THP with a half life of around 3h is taken three to four times a day orally. For the reason that Parkinsonism causes motor instabilities and neurological manifestations oral administration is not recommended for elderly patients as they may have problem in swallowing the drug. To surpass such problems correlated with the delivery of drug through oral route, drug delivery via topical route for THP is an excellent approach. Stratum corneum is a barrier that has affinity towards lipids endures restriction to molecules that are ionic in nature. Ethosomes are introduced for the purpose of making the topical delivery of THP a successful and efficient one. During characterization of THP containing ethosomes the particle was found to be small i.e. 109 ± 2 nm and the entrapment efficiency was much higher (75 ± 0.5%). The percutaneous delivery of ethosomal THP was compared with the liposomal THP by using the skin of a naked mice in the dorsal side which revealed the THP flux of around fifty one times better than liposomes. After 18h of experiment the drug quantity that was accrued in skin was much higher in ethosomes. Stability of ethosomal THP was for two years and more (59).

Hairloss treatment using Ethosomes loaded with Minoxidil:

In the present scenario enomous number of population are affected by hair problems such as Seborrhea and Alopecia. Hence targeting the particular follicles of hair is essential for treating pilosebaceous diseases. Minoxidil is a drug which is having greater affinity towards lipid is often applied locally on scalp to treat alopecia. In vivo studies was conducted in rats that were hairless to examine the activity of ethosome loaded minoxidil in the sebaceous gland. It was revealed that there was a better delivery of minoxidil in the pilosebaceous unit which exhibited localization when ethosome was used as a carrier (60).

Ethosomes for Anti-arthritis and Anti-inflammatory activity:

Ethosomes loaded with Ammonium glycyrrhizinate (AG) was examined for its anti-inflammatory action on volunteers having erythema induced by methyl-nicotinate. Comparison between the hydroethanolic solution of drug and the anti-inflammatory activity of ethosomes loaded ammonium glycyrrhizinate was made to understand the effects of ethosomes on erythema. Reflectance visible Spectrophotometer was used to calculate the Erythema index. When compared to hydroethanolic solution, the ethosomes loaded Ammonium glycyrrhizinate revealed a diminution in the duration and vividness of erythema. The drug Cannabidiol (CBD) which is used for rheumatic arthritis has high affinity towards lipid. This drug has numerous side effects which includes poor BA due to hepatic metabolism, Gastric pH instability and low aqueous solubility. Ethosomal CBD was prepared and assessed for skin permeability via in vivo permeation studies. The drug was found to be accumulated in the skin and tissues underlying (61), (62).

Vaginal delivery using ethosomes:

Ethosomes of metronidazole that are pH responsive were prepared and assessed for its activity in the vaginal delivery. Skin permeation study in vitro was executed on Franz diffusion cell using phosphate buffer as a medium with a pH of 5.5 and cellulose semipermeable membrane. The results showed that the ethosome loaded metronidazole revealed a flux of maximum value i.e. 143.67±2.73 µg/cm²/h which indicates a sustained delivery of the prepared metronidazole ethosomes (36).

Ethosomes with analgesic and antipyretic activity:

Ethosomes loaded with ibuprofen for percutaneous delivery is examined for its analgesic and anti-pyretic activity by in vivo studies using animals (63). The report revealed that after applying the ibuprofen loaded ethosomal gel, there was a reduction in body temperature in rats with fever which reached normal temperature of body in 3h. For 12h, the temperature of body persisted to be 37±0.2°C while the body temperature in rats which consumed ibuprofen through oral delivery showed reduction in temperature after 1h but it persisted to be low for only 7h after which there was rise in temperature to 38±0.4°C. When comparing the analgesic activity of ethosomal gel of ibuprofen to oral ibuprofen after application for about 120-360min in mice by tail flick test, it was observed that the ethosomal ibuprofen revealed better activity than the oral ibuprofen. Ethosomal ibuprofen was found to be more efficient for percutaneous delivery hence neglecting the GI bleeding and ulceration produced by oral ibuprofen.

Treatment of skin diseases using ethosome as carrier:

Anti-psoriatic activity was examined by using the tretinoin containing ethosomes and various other nanolipid carriers in the mouse tail model. For shallow skin problems such as psoriasis, ethosomes were found to be ineffective. Two models for skin cancer i.e. intradermal injection of ES2 cells and TE.354.T cells were estimated for antitumor activity using naked mice. When compared to a marketed product, both the models revealed to have repression of tumor development. Activity of 5-aminolevulinic acid loaded with ethosomes and liposomes were related to photodynamic treatment of skin cancers that are non-melanomic. It was witnessed that ethosomes exhibited more penetration ability than liposomes(64),(65).

Ethosomes for hypertension:

Valsartan is an anti-hypertensive oral drug with poor absorption via Gastroinntestinal tract which in turn has lesser BA because of first pass metabolism. Transdermal delivery of valsartan will surpass the disadvantages related to the oral delivery of valsartan. Wistar rats were used to examine the anti-hypertensive activity by induction of methyl prednisolone acetate which is allied with hypertension. In comparison between the oral suspension and topical delivery of valsartan, enhanced and sustained effect was observed in case of transdermal delivery. Optimization of valsartan was done using Box-Behnken design in which a nanoethosomal gel was prepared by conservative thin layer evaporation method. Rats with hypertension were used to assess the PD (pharmacodynamic) effects in vivo of valsartan. Around 34.11% decrease in BP was observed in the Valsartan containing ethosomes which in turn was concluded to be efficient (66).

Diverse Applications of ethosomes:

Drug delivery via skin using formulations containing ethosomes has been successful. High drug accumulation of Finasteride containing ethosomes into deeper strata was observed to have a greater flux of around 2.6, 3.2 and 7.4 times better than that of hydroethanolic drug solution, conventional liposomes and aqueous solution respectively (67). Linoleic acid loaded ethosomes have greater penetration via skin for hyperpigmentation associated diseases through topical delivery. Contrast agents such as iodine when used with ethosomes has an application on imaging for the computed tomography (68)(69). Lung diseases are also treated using ethosomes. Vitiligo is treated using nanosized topical hydrogel formulation of ethosomes which was found to be effective with methoxsalen. Hepatitis and HIV can also be treated using ethosomes. For good pharmacological effect, synthesis of gold nanoparticles takes place in the bilayer of ethosomes. Skin lightning agent such as phenyl ethyl resorcinol encapsulated with ethosomes demonstrates a better activity in the inhibition of tyrosinase and the diminution of melatonin without any irritation in skin. An anti-diabetic drug namely repaglinide which has a short half-life for about 1h was formulated with ethosomes for percutaneous delivery. It was observed that there was diminution in the frequency of dosing and the repaglinide effect was prolonged due to the ethosomal formulation (41).

CONCLUSION:

Among the different layers of skin, the SC (stratum corneum) bids as a major barrier for penetration of drug into skin. Ethosomes are the leading edge vesicular system which is distinctively premeditated containing eminent level of ethanol which makes ethosomes supple and dexterous enough to fluidize and intrude the lipids of stratum corneum which in turn results in an efficacious delivery of drug into the deeper layer of skin. Apart from the non-invasive delivery of molecules that are small, intermediate or prominently large, inexpensive therapy and patient acquiescence is achieved. Ethosomes brings about the progress of enhanced therapies with novel challenges and prospects. It is apparent that these ethosomal vesicles gains great interest among the researchers which will consent drug release in vivo with better control that will result in good manufacturing and therapeutic efficacy. Thus ethosomes are proven to be the pioneering carriers for the conveyance of therapeutic agents.

ACKNOWLEDGEMENT:

The authors would like to thank the Department of Science and Technology-Fund for improvement of Science and Technology Infrastructure in Universities and Higher Educational Institution (DST-FIST), New Delhifor providing Nanospray drier/ Hanson diffusion cell/ Malvern Zetasizer/Rheometer under the DST-FIST program.

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

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Received on 22.12.2018 Modified on 31.01.2019

Research J. Pharm. and Tech. 2019; 12(7): 3133-3143.

DOI: 10.5958/0974-360X.2019.00529.8