Nanocarrier Systems for Transdermal Drug Delivery

Abstract

is an open discussion, in one hand, the nanotechnologist continue making new and more sophisticated nanocarriers and in the other hand, toxicologist continue evaluating possible damaging effects.Whatever it happens, nanotechnology is the new era and nanomedicine cannot be taking off. New nanocarriers will be created and the entire scientist working in nanomedicine bet for it to be the cure of diseases that in this moment are difficult to deal with [3] The application of preparations to the skin for medical purposes is as old as the history of medicine itself, with references to the use of ointments and salves found in the records of Babylonian and Egyptian medicine. The historical development of permeation research is well described by Hadgraft & Lane [4]. Over time, the skin has become an important route for drug delivery in which topical, regional or systemic effects are desired. Nevertheless, skin constitutes an excellent barrier and presents difficulties for the transdermal delivery of therapeutic agents, since few drugs possess the characteristics required to permeate across the stratum corneum in sufficient quantities to reach a therapeutic concentration in the blood. In order to enhance drug transdermal absorption different methodologies have been investigated developed and patented [5,6]. Improvement in physical permeationenhancement technologies has led to renewed interest in transdermal drug delivery. Some of these novel advanced transdermal permeation enhancement technologies include: iontophoresis, electroporation, ultrasound, microneedles to open up the skin and more recently the use of transdermal nanocarriers [3,[7][8][9][10].A number of excellent reviews that have been published contain detailed discussions concerning many aspects of transdermal nanocarriers [11][12][13][14][15][16][17]. The present chapter shows an updated overview of the use of submicron particles and other nanostructures in the pharmaceutical field, specifically in the area of topical and transdermal drugs. This focus is justified due to the magnitude of the experimental data available with the use of these nanocarriers. The development of submicron particles and other nanostructures in the pharmaceutical and cosmetic fields has been emerged in the last decades for designing best formulations for application through the skin [18][19][20][21]. The skinThe skin is the largest organ of the body [22][23][24], accounting for more than 10% of body mass, and the one that enables the body to interact more intimately with its environment. Essentially, the skin consists of four layers: The SC, that is the outer layer of the skin (nonviable epidermis), and forms the rate-controlling barrier for diffusion for almost all compounds. It is composed of dead flattened, keratin-rich cells, the corneocytes. These dense cells are surrounded by a complex mixture of intercellular lipids, namely, ceramides, free fatty acids, cholesterol, and cholesterol sulphate. Their most important feature is that they are structured as ordered bilayer arrays [25]...

Breaching the skin barrier through temperature modulations

“…The physiology of the skin has been excellently described in previous publications [20][21][22], and an overview thereof is presented here.…”

The the Microemulsion as a Key Player in Conquering the Skin Barrier for the Aim of Transdermal Delivery of Drugs: Reviewing a Successful Decade

“…The main role of this layer is to store fat, and thereby act as a protectant against external physical pressure and generates heat. Furthermore, one of the important characters of this layer is to convey the vascular and neural systems for the skin [14] Skin penetration pathways The dermis layer is the main site for the absorption of molecules. Therefore, to reach it, the breaching of skin barrier function is required.…”

“…However, lately more thoroughly investigates of this penetration mechanism propose a higher significance especially for follicular route [16]. As for the intercellular route the molecules pass through the small spaces between the corneocytes, which makes this route more challenging [14].…”

“…On the other hand, there are some limitations for the transdermal route including local irritation, local edema, and itching especially at the site of application, in addition to erythema which may occur due to the active molecules, the adhesive, or other excipients in the formulation. In addition to, the skin's low permeability which restricts the quantity of active moieties that can be transported transdermally [14].…”

“…Those methods lead to widening or multiplication of the pathways for dermal microcirculation. The physical methods include the exposure of the SC to mechanical stimuli (sonoporation/sonophoresis), a strong electrical stimulus (electroporation/iontophoresis), thermal stimulus, microporation, needleless injection, magnetophoresis, radiofrequency, pressure wave, and medicated tattoos [14,26]. As for the chemical methods: The use of suitable skin penetration enhancers such as alcohols and polyols (ethanol and propylene glycol), sulfoxides (dimethyl sulfoxide), fatty acids (oleic acid), surfactants (Tween, Span, and sodium lauryl sulfate), amines and amides (Azone and N-methylpyrrolidone), terpenes (limonene), and esters (isopropyl myristate) were developed over the past years.…”