Layered double hydroxides and human health: An overview ✠ C. Del Hoyo Departamento de Química Inorgánica, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de la Merced s/n. 37008 Salamanca, Spain Received 17 January 2005; received in revised form 20 June 2006; accepted 21 June 2006 Available online 13 October 2006 Abstract This work summarizes the beneficial and harmful effects of layered double hydroxides upon human health. Their possible uses in pharmaceutical formulations are present in many subjects: from classical applications as orally and topical drugs to new trends as cancer therapy. The application of layered double hydroxides as excipients and their influence on the bioavailability of the organic active principle is also reviewed. Clay-modified electrodes have received attention in the development of electrochemical sensors and biosensors. This article also reviews this aspect for medical purposes. Finally, a summary of the fields in which layered double hydroxides could be applied to prevent public health is also provided. © 2006 Elsevier B.V. All rights reserved. Keywords: Layered double hydroxides; Pharmaceutical formulations; Drug; Public health 1. Introduction Clay minerals and clays are very extended compounds on the earth surface so they constitute the main component of soils and sedimentary rocks. Due to their presence and special properties that they have, mankind has used them with therapeutic aims from prehistory, not being rare to find references to this subject in works of classic authors. During the Renaissance and with the appearance of the first Pharmacopeia, its use was regulated to a certain extent. The scientific development reached during the XXth century has allowed to understand and to study the reasons of the useful and peculiar properties of clay minerals, directly related to their colloidal size and crystalline structure. These properties are translated in a high specific surface area, optimal rheological proper- ties and/or excellent adsorptive capacity; everything makes cationic clays very useful for a wide range of applications. In the field of health, clay minerals and clays (here often named “cationic clays”) are used in Pharmaceutical Technology and Dermopharmacy as ideal excipients and substances of suitable biological activity due to their chemical inertness and low or null toxicity for the patient (De Benavent, 1960; Galán et al., 1985; Cornejo, 1990; Kibbe, 2000; Carretero, 2002; López Galindo et al., 2005). However, for reasons of utility and fulfillment of requisites, only a limited number of clay minerals are used for these aims. Among them, we should emphasize kaolinite, talc, some smectites (montmorillonite and saponite) and fibrous minerals (sepiolite and paligorskite). The precise use of clay minerals will determine both the technical and legal aspects, and it is necessary to specify the intended use of the clay mineral at issue; for instance, Applied Clay Science 36 (2007) 103 – 121 www.elsevier.com/locate/clay ✠ This work is dedicated to Dr. Ma. Angeles Vicente Hernández (deceased April 2000) in memoriam. E-mail address: hoyo@usal.es. 0169-1317/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2006.06.010