Exploring unsaturated fatty acid cholesteryl esters as transdermal permeation enhancers

Advances in the transdermal delivery of antiretroviral drugs

Antiretroviral therapy regimens are successful in stopping the advancement of human immunodeficiency virus infection to acquired immunodeficiency syndrome, and other opportunistic infections. However, they do have significant disadvantages, including long-term treatment, limited oral bioavailability, inaccessibility to organs, non-adherence by patients, and the development of medication resistance. Because of the listed drawbacks of available routes and the availability of curative medicines for human immunodeficiency virus/acquired immunodeficiency syndrome, advanced solutions are required. Antiretroviral therapy transdermal delivery is one of the current strategies that have attracted much attention from many researchers. In this narrative review, various in vitro, in vivo, and ex vivo transdermal antiretroviral therapy delivery strategies were reviewed, such as transdermal patches and films, lipid-based nano-delivery systems, microneedles, chemical penetration enhancers, and iontophoresis, which showed promising results. Although the majority of studies on Antiretroviral transdermal delivery have produced hopeful findings, additional in-depth research on passive and physical enhancement techniques, both existing and new, is necessary to fully understand the potential of this route and to make it accessible to human immunodeficiency virus patients.

Recent advances in delivery of transdermal nutrients: A review

Nutrients provide vital functions in the body for sustained health, which have been shown to be related to the incidence, prevention and treatment of disease. However, limited bioavailability, loss of targeting specificity and the increased hepatic metabolism limit the utilization of nutrients. In this review, we highlight transdermal absorption of nutrients, which represents an opportunity to allow great use of many nutrients with promising human health benefits. Moreover, we describe how the various types of permeation enhancers are increasingly exploited for transdermal nutrient delivery. Chemical penetration enhancers, carrier systems and physical techniques for transdermal nutrient delivery are described, with a focus on combinatorial approaches. Although there are many carrier systems and physical techniques currently in development, with some tools currently in advanced clinical trials, relatively few products have achieved full translation to clinical practice. Challenges and further developments of these tools are discussed here in this review. This review will be useful to researchers interested in transdermal applications of permeation enhancers for the efficient delivery of nutrients, providing a reference for supporting the need to take more account of specific nutritional needs in specific states.

Green formulation, characterization, antifungal and biological safety evaluation of terbinafine HCl niosomes and niosomal gels manufactured by eco-friendly green method

Terbinafine (TER) is a promising candidate medication for the topical treatment of fungal infections. However, its solubility in water and skin permeability are limited. To overcome these limitations, a Terbinafine niosome and niosomal gel was developed. The impact of cholesterol:surfactants on terbinafine incorporated niosome (terbinasome) preparations was examined. Differential scanning calorimetry (DSC), photon correlation spectroscopy (PCS), scanning electron microscopy (SEM), and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy were used to assess the morphological features of terbinasome and the physicochemical characteristics of TER in terbinasome. The obtained results has shown that Chol enhanced the diameter of the terbinasome from 123.20 ± 2.86 to 701.93 ± 17.72 nm. The highest encapsulation of terbinafine was estimated to be around 66% due to the cholesterol:surfactants ratio in the terbinasome was 1:3 and 1:6. Additional examination has revealed that changes in the cholesterol:surfactants ratio can result in a change in the PDI value of between 0.421 ± 0.004 and 0.712 ± 0.011. The terbinasome gel was prepared and tested for pharmaceutical testing, including pH, viscosity, spreadability, and stability. The percentage of TER dissolution from terbinasome were determined more than 80% and showed quickest drug release. In a cutaneous permeability examination, the quantity of TER in the cutaneous layers and the receiver compartment were higher for the terbinasome gel than for the TER simple gel. The terbinasome's cell viability was around 90% (HFF cell line) and MTT experiment demonstrated that the terbinasome was not cytotoxic. The MIC of the terbinasome was lower than pure drug against Aspergillus, Fusarium, and Trichophyton. The terbinasomal gels were non-irritant (score < 2) in the cutaneous irritation examination performed on Wistar rats. The research suggests that the optimized terbinasome may be used as a nano-vesicle for TER drug administration, hence opening up new possibilities for the treatment of cutaneous infections.

A simple and efficient approach for the synthesis of cholesterol esters of long-chain saturated fatty acids by using Ph3P·SO3 as a versatile organocatalyst

Cholesteryl esters are more nonpolar compounds formed by the conjugation of cholesterol with fatty acids containing a long hydrocarbon chain. These ester molecules do not participate in the composition of the cell membranes and are found in lipid droplets. Because this form of cholesterol can be packaged in a larger amount in lipoproteins, the transport of cholesterol is more effective, and also, these esters play an important role in cholesterol metabolism. Moreover, some of their hydroperoxide derivatives are biologically active components of minimally modified low-density lipoprotein (mmLDL). In recent years, these esters have attracted attention in many industrial and medical applications. In this study, a triphenylphosphine-sulfur trioxide adduct efficiently catalyzed the esterification reactions between homologous long-chain saturated monocarboxylic or dicarboxylic fatty acids and cholesterol molecule in toluene. In these reactions, the triphenylphosphine-based adduct acts as a source of sulfur trioxide. Reactions were performed at 110 °C with equimolar amounts of the reagents except in the case of dicarboxylic acids, and two equimolar of cholesterol was used to afford the corresponding homologous cholesteryl esters in good to excellent yields. The present developed method has advantages such as being simpler, practical, and less toxic than the existing ones as well as enabling the synthesis of the related esters with higher yields.

Esters of terpene alcohols as highly potent, reversible, and low toxic skin penetration enhancers

Skin penetration/permeation enhancers are compounds that improve (trans)dermal drug delivery. We designed hybrid terpene-amino acid enhancers by conjugating natural terpenes (citronellol, geraniol, nerol, farnesol, linalool, perillyl alcohol, menthol, borneol, carveol) or cinnamyl alcohol with 6-(dimethylamino)hexanoic acid through a biodegradable ester linker. The compounds were screened for their ability to increase the delivery of theophylline and hydrocortisone through and into human skin ex vivo. The citronellyl, bornyl and cinnamyl esters showed exceptional permeation-enhancing properties (enhancement ratios up to 82) while having low cellular toxicities. The barrier function of enhancer-treated skin (assessed by transepidermal water loss and electrical impedance) recovered within 24 h. Infrared spectroscopy suggested that these esters fluidized the stratum corneum lipids. Furthermore, the citronellyl ester increased the epidermal concentration of topically applied cidofovir, which is a potent antiviral and anticancer drug, by 15-fold. In conclusion, citronellyl 6-(dimethylamino)hexanoate is an outstanding enhancer with an advantageous combination of properties, which may improve the delivery of drugs that have a limited ability to cross biological barriers.

Effect of neat and binary vehicle systems on the solubility and cutaneous delivery of piperine

Vitiligo is a skin disease characterized by depigmentation disorders due to lack of melanin production. Piperine, an alkaloid extracted from black piper, is active in melanocytes proliferation. To achieve this, the drug has to reach the melanocytes which exist in the deep layer of the epidermis. Higher drug concentration can be obtained after application of optimized formulation to skin. Accordingly, the aim of this work is to investigate the effect of vehicles on skin penetration of piperine as the first step in development of optimized formulation. The tested vehicles include ethanol (Eth), propylene glycol (PG), polyethylene glycol 400 (PEG), and oleic acid (OA) and their combinations. Water was used as the control and skin permeation was monitored using rabbit ear model skin. The highest piperine solubility (48.6 mg/ml) and flux (40.8 μg/cm² h) was achieved by Eth and the lowest piperine flux (1.17 μg/cm² h) was reported for PEG. PG and OA showed piperine flux values comparable to that of the control. Among different combination systems, Eth-OA (75:25) binary system had the highest piperine flux (59.3 μg/cm² h) followed by Eth-OA (50:50) (32.3 μg/cm² h) and PG-OA (90:10) (22.7 μg/cm² h). The study thus introduced a vehicle system as the first step in the development of topical formulation of piperine.