Abstract
The synthesis method of layered double hydroxides (LDHs) determines nanoparticles’ performance in biomedical applications. In this study, hydrothermal treatment as an important synthesis technique has been examined for its influence on the physicochemical properties and the drug release rate from drug-containing LDHs. We synthesised MgAl–LDHs intercalated with non-steroidal anti-inflammatory drugs (i.e., naproxen, diclofenac and ibuprofen) using a co-precipitation method with or without hydrothermal treatment (150 °C, 4 h). After being hydrothermally treated, LDH–drug crystallites increased in particle size and crystallinity, but did not change in the interlayer anion orientation, gallery height and chemical composition. The drug release patterns of all studied LDH–drug hybrids were biphasic and sustained. LDHs loaded with diclofenac had a quicker drug release rate compared with those with naproxen and ibuprofen, and the drug release from the hydrothermally-treated LDH–drug was slower than the freshly precipitated LDH–drug. These results suggest that the drug release of LDH–drugs is influenced by the crystallite size of LDHs, which can be controlled by hydrothermal treatment, as well as by the drug molecular physicochemical properties.
Highlights
Layered double hydroxides (LDHs), known as hydrotalcite-like materials or anionic clays, can be found in nature as minerals, as well as being readily synthesised in the laboratory [1]
Ultrasonic treatment was used to break down the dried agglomerates of layered double hydroxides (LDHs)–NAP, LDH–DIC and LDH–IBU in ethanol for the particle size distribution measurement, and all LDH–drug suspension had a narrow size distribution with a polydispersity index (PDI) smaller than 0.3 (Table 1)
In the case of LDH containing NAP or DIC, the average hydrodynamic diameter of LDH–drug particles prepared with hydrothermal treatment (194–332 nm) was significantly larger than that without hydrothermal treatment (159–172 nm) (Table 1)
Summary
Layered double hydroxides (LDHs), known as hydrotalcite-like materials or anionic clays, can be found in nature as minerals, as well as being readily synthesised in the laboratory [1]. The most commonly used method is the co-precipitation of mixed metal salt solution in hydroxide solution at a constant or various pH followed by aging at a temperature over 100 °C (hydrothermal treatment) [1]. Hydrothermal treatment makes the metal cations (M2+ and M3+) distribute more evenly within the hydroxide layers and form a better crystallised LDH particle. There are a few studies on the influences of hydrothermal treatment on the physicochemical properties of LDHs, little is known on the changes in the physicochemical and release properties of therapeutic molecule-intercalated LDH nanohybrids after being hydrothermally treated. The aim is to investigate the effect of hydrothermal treatment on the morphology, particle size and structure of the drug–LDH nanohybrids, as well as the subsequent possible changes in the drug release pattern
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