Layered double hydroxides (LDH) are matrices with interlayer anions that can be exchanged with several types of organic or inorganic anions. Due to the anion-exchange capability, hundreds of new materials have been prepared in the past two decades. Conversely, attempts to intercalate neutral molecules (and increase the range of applications) have been achieved by expanding the interlayer space with longchain surfactants, thus allowing to exclusively retain highly hydrophobic molecules. This work describes a folate-intercalated LDH structure, where folate pillars are capable of forming both hydrogen bonds and hydrophobic interactions with neutral molecules. Infrared spectroscopy and X-ray diffraction data indicated that imidazole, urea and cyclophosphamide were successfully intercalated. This evidence increases the opportunity to prepare more novel materials with neutral molecules in LDH. The cyclophosphamide-LDH product here obtained represents a remarkable example of an LDH-based vehicle for a non-ionic anti-cancer drug used in current chemotherapies.1. Introduction: Layered double hydroxides (LDH) are synthetic layered compounds widely known for their positively charged layers as a result of the isomorphic substitution of divalent cations located in octahedral sites of brucite-like layers by trivalent cations [1]. The positive charge is neutralised by interlayer anions, which can be exchanged with a large number of anions. This anion-exchange property is the most remarkable feature of these structures [2, 3] because even organic anions can be inserted between the layers by the exchange process to produce new hybrid materials such as gene and drug vehicles [4,5], polymer flame retardants [6], enzyme supports [7,8] or nutraceutical and cosmeceutical carriers [9, 10]. Due to the ease of intercalating different types of anions into LDH, hundreds of scientific articles are published every year. Unusual cases of neutral molecules intercalated in LDH have been reported with ribose and curcubituril [11,12] and attempts to improve this intercalation involves pre-expansion of LDH with long chain anions. Examples of this is the intercalation of iphosphamide into a pre-expanded LDH with dodecylsulphate (DDS); the intercalation of ultraviolet (UV)-absorbers after expansion of the interlayer space with DDS or dodecylbenzenesulphonate [13]; and the intercalation of curcubituril into a pre-expanded LDH with DDS [12].This strategy has been limited to increase the size of interlayer galleries with long chain hydrophobic anions (surfactants) and consequently, the neutral species intercalated further required a high hydrophobic character. In fact, we have observed our own experiments that urea (a highly polar molecule) does not intercalate into surfactant pre-expanded LDH.On the other hand, considering that folic acid, by itself, can retain aromatic molecules like anthracene due to an attraction with π bonds [14], the present Letter reports the use of a pre-expanded LDH structure with folate anions where the aromatic rings allow r...
Abstract:The antineoplasic activity of gallic acid has been reported. This compound induces apoptosis and inhibits the growth of several neoplasic cells. However, this molecule is easily oxidized and degraded in the body. The aim of this work was to intercalate gallate ions into layered double hydroxide (LDH) nanoparticles under controlled conditions to reduce oxidation of gallate and to evaluate its toxicity against the A549 adenocarcinoma cell line. An isopropanol medium under nitrogen atmosphere was adequate to intercalate gallate ions with a lesser oxidation degree as detected by electron spin resonance spectroscopy. Concentrations of the hybrid LDH-gallate nanoparticles between 0.39 and 25 µg/mL reduced the cell viability to 67%, while the value reached with the pure gallic acid and LDH was 90% and 78%, respectively, thus proving that the combination of gallate ions with the inorganic nanoparticles increases the toxicity potential within this dose range.
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