Nano-antibiotics Bullet: Highly Functionalized Carbon Nanotubes and their Antibacterial Activity

As the infectious diseases continue to be one of the greatest health challenges worldwide, the demand for alternative agents is increased because the conventional antibiotics have many disadvantages like the development of multiple drug resistance and the adverse side effects. Therefore, scientists go on for nanoparticles, a nanoscale material ranging from 1-100 nanometers. One of these nanoparticles is the carbon nanotubes that pose many unique properties such as physical, chemical, electrical, mechanical and optical properties. The aim of this work was the covalent functionalization of the single walled carbon nanotubes (SWCNTs) with multiple copies of the ciprofloxacin antibiotic through radical reaction that has been developed by tour group to get a highly stable conjugate in the presence of polyethylene glycol linkers to improve the solubility and dispersibility of these nano-antibiotics. The SWCNTs were functionalized with benzylamine moieties blocked with di-tert-butyl-dicarbonate (Boc) protecting groups that can be removed under acidic condition to further functionalization of SWCNTs. The prepared nano-antibiotics were characterized by different techniques, including scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravometric analysis (TGA), nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis), and Raman spectroscopy, while the amine loading was determined by using the Kaiser test. The in vitro release both at room temperature and 37 ̊C and the antibacterial activity against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa of these nano-antibiotics have been studied. The characterization of these nano-antibiotics confirmed the successful covalent functionalization of the SWCNTs with ciprofloxacin with 50% functionalization as obtained by TGA. While the release profile revealed the similarity in the release pattern at room temperature and at 37 ̊C in the presence of porcine liver esterase (PLE). About 90% of the loaded ciprofloxacin in SWCNTs was released in 2.5 h at pH 7.4. Interestingly, the results of the antibacterial activity indicated that the functionalized SWCNTs have more significant increase in the antibacterial activity against the three strains of bacteria by 16 folds for S.aureus and P.aeruginosa and by 8 folds for E.coli in comparison to the ciprofloxacin and pristine SWCNTs alone.