Sol-Gel Immobilization of Colistin Sulfate onto Double Walled Carbon Nanotubes: In Vitro Bone Bioactivity

The aim of this study is to fabricate a multifunctional biohybrid composite utilizing double walled carbon nanotubes (DWCNTs) as a carrier for loading of the colistin sulfate (CLS) through the application of the sol-gel technique. The resulting composite was analyzed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), X-ray diffraction patterns (XRD), and particle size distribution analysis utilizing dynamic light scattering technique (DLS). Furthermore, an assessment of in vitro bone bioactivity was conducted under physiological levels of Ca²⁺ and PO⁴⁺ (SBF) at 37 °C and pH 7.4 over a period of 7 days. Additionally, the in vitro cytotoxicity against mice bone marrow cells was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The outcomes indicated that the composite possessed a particle size of 365 nm in diameter with a PDI of 0.21 (the pure CLS and untreated DWCNTs were 290 and 459 nm in diameter, respectively), improved biocompatibility, and promoted the formation of a Ca-phosphate apatite layer on the surface with a Ca/P ratio of approximately 1.78. The findings collectively validated the significant contribution of the CLS peptide in DWCNTs-based composite for the purposes of bone tissue engineering.