Development and analytical characterization of novel bioactive hybrid composites for biomedical or agri-food applications.

The challenge posed by bacterial antibiotic resistance is a huge health problem and the use of alternative antimicrobial systems often poses an issue related to their potential toxicity. Hybrid organic-inorganic composites represent interesting systems for the development of new architectures for different emerging applications, due to their manifold opportunities to optimize the performances of their starting components. In this respect, many plant extracts have been investigated worldwide as potential sources of novel antimicrobial compounds, as alternative tools for the treatment of infectious diseases or as agents able to promote food and cosmetic preservation. On the other hand, natural compounds are often highly unstable, not soluble in aqueous solutions, susceptible to oxidation, thermal degradation and/or rapid volatilization. Among thedifferent protection strategies, caged or lamellar clay minerals have been proposed as vehicles of natural molecules for various applications such as food packaging, hygienic-sanitary, pharmaceutic, agricultural, etc. In this respect, in the last decades we developed and characterized different clays (such as bentonite, zeolite, hydrotalcite, diatomaceous earth, etc.) modified with plant-derived organic molecules showing enhanced antibacterial, antioxidant or biocompatible properties for biomedical or agri-food applications (1-3). More recently, a special attention was paid to the development of hybrid systems based on carvacrol or thymol, the main antimicrobial molecules composing several essential oils, loaded in Zn-exchanged montmorillonite or Zn-exchanged zeolite, designed as new antimicrobials for food packaging applications. Combination of different analytical techniques (XPS, FT-IR, TGA, GC-MS) allowed us to ascertain the success of the ion exchange process, to estimate the loading of the active molecules in the hybrid composites as well as their release in appropriate simulating media. Antimicrobial assays carried out against spoilage and pathogenic bacterial strains, showed intriguing antimicrobial activity for the proposed hybrid materials paving the way for interesting applications of these systems in the agri-food and biomedical fields.