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Tetracyclines (TCs) constitute a group of antibiotics that are commonly used to treat bacterial diseases, in veterinary medicine and as an additive in animal feed. This broad application has led to their accumulation in food products and the environment because sewage treatment plants cannot completely remove them. Therefore, the aim of this study was to synthesize graphene oxide (GO) and evaluate its TC adsorption properties in aqueous media. The effects of pH (between 2.5 and 11) and Ca2+ concentration (between 0 and 1 M) were thoroughly investigated. Structural, textural, and electrokinetic properties of the prepared GO were determined by N2 adsorption/desorption, XRD, TEM, UV–vis, FTIR, XPS, thermogravimetry and electrophoretic mobility measurements. TC adsorption on GO is an interplay between the two main roles played by Ca2+: competitor or bridging cation. At low pH, there is cation exchange, and Ca2+ behaves as a competitor of the positively charged TC species, decreasing adsorption as calcium concentration increases. At high, the formation of Ca bridges between the surface and TC (GO-Ca2+-TC) is favored, increasing the adsorption of the antibiotic by increasing calcium concentration. Different combinations of Ca2+ and pH effects are important to improve the use of GO either as a pH-dependent and reversible TC adsorbent for decontamination or as pH-independent adsorbent for TC quantification with electrochemical sensors. [ABSTRACT FROM AUTHOR]

For several decades antimicrobial resistance has been a growing threat to the effective treatment of infections, so it is necessary to focus on a rational and effective use of the antibiotics already available. The development of new materials for controlled release of drug is a topic of high priority. Vancomycin (VAN) is a glycopeptide antibiotic used to treat infections caused by gram positive bacteria, and layered double hydroxides (LDH) are inorganic and biocompatible excipients that can provided a long drug release time. In this work, LDH-VAN complexes were synthesized by two methods: co-precipitation and reconstruction. They were characterized by XRD, FTIR, TG, DSC, SEM and EDS, together with dissolution and release kinetics, and electrophoretic mobilities. The coprecipitation samples resulted in particles with a homogeneous chemical composition where there is a rather intimate contact between VAN and the solid phase of the LDH. Reconstruction samples were heterogeneous, but presented higher drug content. There was a congruent dissolution of coprecipitation samples, with VAN being released at the same rate than Mg. Reconstruction samples, on the contrary, dissolved incongruently, with VAN being released much more rapidly than Mg. The rate of VAN release can be tuned and controlled in coprecipitated samples by simply controlling the solution pH. [ABSTRACT FROM AUTHOR]