Organic-Inorganic Composites Based on Multi-walled Carbon Nanotubes ‎ Containing Lysine/Histidine

Abstract

Carbon nanotubes (CNTs) have been employed alone or in composites with other substances to generate highly useful materials in a variety of industries. They are especially promising as scaffolds for bone tissue regeneration. To the best of our knowledge, no studies have been published on the usage of lysine (Lys) or histidine (His) for functionalizing oxidised Multiwalled carbon nanotubes (ox-MWCNTs) using the sol-gel process. The goal of this research is to create innovative hybrid composites for biomedical applications based on ox-MWCNTs incorporating tetra ethyl orthosilicate (TEOS) and various amino acids (Lys or His). Fourier transform infrared spectroscopy (FTIR), dynamic light scattering technique (DLS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning and transmission electron microscopes (SEM and TEM) were used to characterise the physicochemical properties.. In vitro bone bioactivity was tested after 7 days of soaking in simulated body fluid (SBF) at 37 °C, as well as cytotoxicity against mice bone marrow stromal cells using the MTT assay. The results showed that both functionalized MWCNTs had particle sizes of 1332 and 1329 nm and are colloidal stable. After soaking the composites in SBF, SEM pictures revealed aggregated ca-apatite layers on the surface. After soaking for 7 days, the calcium element and the liberated free amino acids concentrations in the residual SBF were approximately (2.1 and 0.9) and (2.6 and 2.0) mg/L in the case of both amino acids, respectively. It can be concluded that both covalent attached amino acids play enhancement role for the ca-apatite formation and lowering the toxicity in the hybrid composites relative to the ox-MWCNTs especially in the case of His.