Synthesis, characterization, cytotoxicity and antimicrobial activity of a nanostructured mineral clay

Abstract

Clay minerals nanostructured appear as an alternative to increase textural property and mechanical strength, such as montmorillonite (MMT-NPs). Nanocomposites are nanomaterials made up of a matrix and reinforcement, to obtain a higher quality nanomaterial. In parallel, (agro)industrial waste constitutes a major socio-environmental problem, such as rice husk (RH - a source of silica) and residual sludge (RS – a source of silica and aluminum). In this context, the present work aims to synthesize and characterize montmorillonite nanoparticles (MMT-NPs) for use as nanocomposite support to evaluate the safety profile in 293T embryonic kidney human and antimicrobial activity against E. coli, S. aureus and P. aeruginosa strains. X-ray diffraction (XRD) showed the presence of characteristic peaks of montmorillonite in the crystalline phases of the neighborite, muscovite, kaolinite and quartz low. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectra indicated the stretching of Si-O-Si (at 991.29 cm−1) and Si-O-Al at 470.54 cm−1. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) micrographs indicated a heterogeneous morphology with a semicube shape and composition containing sodium, aluminum, potassium, and magnesium. MMT-NPs showed type V isotherms with H3 hysteresis (mesoporous characteristics) and SBET = 18 ± 0.2 m2 g−1, Dp = 33.5 ± 0.5 nm with zeta potential (ZP) of the −18.2 ± 0.4 mV and a contact angle around 26.1°. Biological results showed a minimal antibacterial inhibition concentration against S. aureus, E. coli and P. aeruginosa of the 15.6, 500 and 500 mg L−1, respectively. Furthermore, the safety profile of MMT-NPs using 293T cells indicated the 100% concentration as safe (>60% cells) and showed the release of reactive oxygen species and nitrates and nitrites similar to the negative control. Therefore, it was possible to synthesize montmorillonite nanoparticles from rice husk and residual sludge for use as a nanocomposite matrix, correlating sustainability and environmental nanotechnology.