Modern drug delivery strategies applied to natural active compounds.

INTRODUCTION: Colloidal drug delivery systems (CDDSs) are innovative carriers that have been studied in pharmaceutical field from many years to overcome unfavorable physical and chemical features of synthetic drugs. Recently the use of CDDS as carriers for phytochemicals has seen an exponential increase which, in some cases, has led to the rediscovery of ancient and forgotten natural molecules. Area covered: This article focuses on the main features of CDDS, particularly micro- and nanoemulsions, vesicular carriers and micro- and nanoparticles, loaded with natural active compounds. A detailed review of the literature is presented, introducing the importance of these systems in terms of their capability to optimize the stability of phytochemicals, their absorption through biological membranes and their bioavailability. Expert opinion: The delivery of phytochemicals is problematic due to poor solubility, poor permeability, low bioavailability, instability in biological milieu and extensive first-pass metabolism. Global research efforts investigating nanotechnology have attempted to overcome these limitations rediscovering and, in some cases, 'discovering ex novo' unexpected virtues and benefits associated to these compounds. The 'nanotechnological approach' can definitely enhance the pharmacokinetics and therapeutic index of natural active compounds and improve their performance in therapy.

Design of solid lipid nanoparticles for caffeine topical administration.

CONTEXT: Solid lipid nanoparticles (SLN) are drug carriers possessing numerous features useful for topical application. A copious scientific literature outlined their ability as potential delivery systems for lipophilic drugs, while the entrapment of a hydrophilic drug inside the hydrophobic matrix of SLN is often difficult to obtain. OBJECTIVE: To develop SLN intended for loading caffeine (SLN-CAF) and to evaluate the permeation profile of this substance through the skin once released from the lipid nanocarriers. Caffeine is an interesting compound showing anticancer and protective effects upon topical administration, although its penetration through the skin is compromised by its hydrophilicity. MATERIALS AND METHODS: SLN-CAF were formulated by using a modification of the quasi-emulsion solvent diffusion technique (QESD) and characterized by PCS and DSC analyses. In vitro percutaneous absorption studies were effected using excised human skin membranes (i.e. Stratum Corneum Epidermis or SCE). RESULTS: SLN-CAF were in a nanometric range (182.6 ± 8.4 nm) and showed an interesting payload value (75% ± 1.1). DSC studies suggest the presence of a well-defined system and the successful drug incorporation. Furthermore, SLN-CAF generated a significantly faster permeation than a control formulation over 24 h of monitoring. DISCUSSION AND CONCLUSIONS: SLN-CAF were characterized by valid dimensions and a good encapsulation efficiency, although the active to incorporate showed a hydrophilic character. This result confirms the suitability of the formulation strategy employed in the present work. Furthermore, the in vitro evidence outline the key role of lipid nanoparticles in enhancing caffeine permeation through the skin.

Evaluation of nanostructured lipid carriers (NLC) and nanoemulsions as carriers for UV-filters: characterization, in vitro penetration and photostability studies.

The increased awareness of protection against UV radiation damages has led to a rise in the use of topically applied chemical sunscreen agents and to an increased need of innovative carriers designed to achieve the highest protective effect and reduce the toxicological risk resulting from the percutaneous absorption of these substances. In this paper, nanostructured lipid carriers (NLC) and nanoemulsions (NE) were formulated to optimize the topical application of different and widespread UVA or UVB sun filters (ethyl hexyltriazone (EHT), diethylamino hydroxybenzoyl hexyl benzoate (DHHB), bemotrizinol (Tinosorb S), octylmethoxycinnamate (OMC) and avobenzone (AVO)). The preparation and stability parameters of these nanocarriers have been investigated concerning particle size and zeta potential. The release pattern of the sunscreens from NLC and NE was evaluated in vitro, determining their percutaneous absorption through excised human skin. Additional in vitro studies were performed in order to evaluate, after UVA radiation treatment, the spectral stability of the sunfilters once formulated in NLC or NE. From the results obtained, when incorporated in NLC, the skin permeation abilities of the sun filter were drastically reduced, remaining mainly on the surface of the skin. The photostability studies showed that EHT, DHHB and Tinosorb S still retain their photostability when incorporated in these carriers, while OMC and AVO were not photostable as expected. However, no significant differences in terms of photoprotective efficacy between the two carriers were observed.

Emerging role of colloidal drug delivery systems (CDDS) in NSAID topical administration.

NSAIDs are the most commonly prescribed category of drugs for the treatment of musculoskeletal pain and inflammation associated with many conditions. Topical administration of these drugs is always the best choice since adverse effects occur commonly with systemic NSAID therapy. Colloidal drug delivery systems (CDDS) are interesting systems, which are able to improve the duration of drug residence in the skin and to allow an achievable drug sustained and controlled release compared to conventional topical formulations. This review focuses on micro and nanoemulsions, vesicular carriers and nanoparticles as novel high efficiency delivery systems of NSAIDs in topical applications.