Rita Sánchez-Espejo

Release kinetics of 5-aminosalicylic acid from halloysite

This paper investigates desorption of 5-aminosalicilyc acid (5-ASA) adsorbed onto halloysite (HL). Desorption isotherms were fitted according to kinetic laws obtained considering release of 5-ASA from HL as the phase of desorption of the previously adsorbed drug molecules both inside the nanotubes of HL as onto the surface of clay particles and/or in the inter-particle spaces of their aggregates. Desorption isotherms has been also fitted with other equations frequently used in drug release kinetics studies. The best fitting corresponded to the kinetic model proposed; in agreement with the results of adsorption.

Intestinal permeability of oxytetracycline from chitosan-montmorillonite nanocomposites

A nanocomposite based on chitosan and montmorillonite was developed as carrier to improve oral bioavailability of oxytetracycline. The nanocomposite was prepared by simple solid-liquid interaction and loaded with the drug. The loaded nanocomposite was characterized by X-ray powder diffraction, thermal analysis, FTIR spectroscopy and zeta potential. Caco-2 cell cultures were used to evaluate in vitro cytotoxicity and drug permeation. Confocal laser scanning microscopy was also performed to evaluate the eventual entrapment of drug into the Caco-2 cells. Results showed that the nanocomposite was internalized into the cells and effectively enhanced drug permeation, being also biocompatible towards Caco-2 cells.

Assessment of halloysite nanotubes as vehicles of isoniazid

Equilibrium and thermodynamic aspects of the adsorption of isoniazid (INH) onto halloysite nanotubes (HLNTs) and characteristics of the resultant drug/nanocarrier systems are investigated. Equilibrium studies were performed in aqueous medium at different times, temperatures and drug concentrations. The overall adsorption process was explained as the result of two simple processes: adsorption on the activated sites of HLNTs and precipitation of INH on HLNTs surface. Formation of the INH-loaded HLNTs was spontaneous, endothermic and endoentropic, increasing the thermodynamic stability of the system (ΔH=70.40kJ/mol; ΔS=0.2519kJ/molK). Solid state characterization corroborated the effective interaction between the components that was also described by modeling at molecular level by quantum mechanics calculations along with empirical interatomic potentials. Transmission electron microphotographs confirmed the double allocation and homogeneous distribution of INH in the nanohybrids. FTIR spectra revealed the interaction via hydrogen bonds between the inner hydroxyl groups of HLNTs and N in INH molecules. Loading of INH in the nanohybrids was approximately 20% w/w. Effective loading of INH and activation energies of the interactions enable to propose the designed nanohybrids in the development of modified drug delivery systems.

Clays in complementary and alternative medicine

Abstract In western countries complementary and alternative medicine is used to sustain the mainstream medical practice (biomedicine). Nowadays, it is used to treat diseases, but also in the prevention, health promotion and health maintenance. Complementary and alternative medicine includes treatments that do not involve use of material substances (mind body treatments), but also other therapies including the use of materials in their treatments. Clays are frequently used as biomaterials with clinical applications in complementary and alternative medicine, as actives and excipients. The uses of clay materials in these medicines are revised, including homeopathy, balneotherapy, natural health substances (i.e. food supplements), as well as other traditional therapeutic systems as Ayurveda and traditional Chinese medicine, with increasing presence in western countries.

Characterisation of Tunisian layered clay materials to be used in semisolid health care products

Abstract The possibilities of nine Tunisian clay samples to be used in semisolid health care products have been evaluated. Clays from Aleg formation (Conacian–Santonian) at Jebel Romana (R1, R2, R3, R4, R5 and R6) and Jebel Aidoudi (AYD3) and clay potter formation (Pliocene) at Menzel Temime, Cap Bon (CBL) and Jebel Ayat (JAD12) were characterised, including their mineralogical and chemical compositions, textural features and technical properties. Two commercial clay samples were also included as reference materials. Samples from meridional Atlas were mainly composed of smectites, whereas those from septentrional Atlas and Saharian platform were illitic or illitic–smectitic. All samples were very fine powders mainly constituted by irregularly flake shaped particles. By comparison with the commercial materials, those samples with better perspectives in future semisolid formulations were R1–R3, R5 and AYD3. The non-selected samples showed mineral impurities and/or technical features that should require treatments before considering their possible use.

Advanced Inorganic Nanosystems for Skin Drug Delivery

On/into/through the skin drug delivery represents an attractive alternative for the oral route, providing local and/or systemic drug delivery. Due to its complex and well-organised structure, most of the drugs show difficulties to penetrate the human skin. Therefore, enormous efforts have been invested to develop intelligent drug delivery systems overcoming the skin barrier with particular emphasis on increasing therapeutic activity and minimizing undesirable side-effects. Most of these strategies require the use of singular materials with new properties. In particular, and on the basis of their inherent properties, including biocompatibility, biodegradability and relative low-cost, inorganic nanoparticles are ideal candidates for the development of skin drug delivery systems. This review provides an updated and comprehensive overview of the state of the art in the trends towards skin drug delivery with a particular focus in the attractive alternative offered by inorganic-based nanosystems.