Nanoemulsion: A Review on Mechanisms for the Transdermal Delivery of Hydrophobic and Hydrophilic Drugs

Abstract

Nanoemulsions (NEs) are colloidal dispersions of two immiscible liquids, oil and water, in which one is dispersed in the other with the aid of a surfactant/co-surfactant mixture, either forming oil-in-water (o/w) or water-in-oil (w/o) nanodroplets systems, with droplets 20–200 nm in size. NEs are easy to prepare and upscale, and they show high variability in their components. They have proven to be very viable, non-invasive, and cost-effective nanocarriers for the enhanced transdermal delivery of a wide range of active compounds that tend to metabolize heavily or suffer from undesirable side effects when taken orally. In addition, the anti-microbial and anti-viral properties of NE components, leading to preservative-free formulations, make NE a very attractive approach for transdermal drug delivery. This review focuses on how NEs mechanistically deliver both lipophilic and hydrophilic drugs through skin layers to reach the blood stream, exerting the desired therapeutic effect. It highlights the mechanisms and strategies executed to effectively deliver drugs, both with o/w and w/o NE types, through the transdermal way. However, the mechanisms reported in the literature are highly diverse, to the extent that a definite mechanism is not conclusive.

Formulation and Optimization of Nanoemulsions Using the Natural Surfactant Saponin from Quillaja Bark

“…In fact, because of its versatility [1,2], the technological application of emulsions is vast among industries that include food [3][4][5], pharmaceutics [6][7][8], and cosmetics [9][10][11]. Among the different types of emulsions, micro-and nanoemulsions present the most appealing properties due to their higher stability and possibility to serve as potential carriers of functionalities [12].…”

Dermal Delivery Enhancement of Natural Anti-Ageing Compounds from Ocimum sanctum Linn. Extract by Nanostructured Lipid Carriers

“…According to the lower release amount and slower release rate of RA from NLC and NE compared to the solution, it could be remarked that both of them exhibited a controlled release pattern. The prolonged release of RA from NE was suggested to result from the rate-limiting step of RA diffusion across the interfacial film between the internal and external phases of NE [9,50], whereas the prolonged release of RA from NLC resulted from the Fickian diffusion of RA throughout the lipid matrix of NLC [51]. The release profiles of NLC can vary from very fast release, medium release, or extremely prolonged release depending on the matrix structure, the method of production, the solubilizing properties of the surfactant for the incorporated active, and the solubility of the active in the lipid matrix [52].…”

“…The average droplet size of NE is usually between 100-500 nm. Due to its small droplet size, NE possesses stability against sedimentation or creaming with Ostwald ripening forming the main mechanism of NE breakdown [9]. NE is easily produced in large quantity by mixing a water-immiscible oil phase into an aqueous phase with a high stress, a mechanical extrusion process which is available worldwide [9].…”

Emerging trends in nanomedicine for topical delivery in skin disorders: Current and translational approaches

“…In addition, the dendrimers also provide enhanced stability to hydrophobic molecules such as resveratrol. 77 The chemical modifications on dendrimers also regulate the drug release, such as G4-COOH dendrimer exhibits an enhanced release of NSAIDs compared to its aminated counterpart.…”