N-Octyl-O-sulfate chitosan stabilises single wall carbon nanotubes in aqueous media and bestows biocompatibility

Abstract

A non-covalent approach to debundle single wall carbon nanotubes using a biocompatible chitosan-derivative, namely N-octyl-O-sulfate chitosan (NOSC), was investigated. The resulting stable dispersions were characterised by Raman spectroscopy, UV-Vis spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and zeta-potential measurements. Both AFM and TEM studies revealed the presence of individual carbon nanotubes wrapped with the polymer (diameters up to 7 nm). Raman spectra showed radial breathing mode frequency shifts, after the addition of NOSC, due to the wrapping of the biomolecules onto the graphitic sidewalls. Molecular modelling studies were employed to investigate the mode of binding of the NOSC chains to the surface of the nanotubes. In agreement with the experiments, modelling studies predicted that the wrapped tube has a maximum thickness of approximately 7 nm. Studies on the anticoagulant properties of these complexes revealed that NOSC coated SWCNTs exhibit similar activity to the polymer alone, this property would eliminate the risk for SWCNTs to induce coagulation as a host reaction process when used in vivo.

Synthesis of carbon nanotubes loaded hydroxyapatite: Potential for controlled drug release from bone implants

“…The same was not true for composites containing MWNTs that gave a higher overall release (109.9%±8.6% and 88.3%±4.0%, with chitosan and NOSC respectively); this may be due to a poorer dispersion in the reaction mixture with more tubes interacting with each other and not available for interaction with the drug. The good dispersion ability of NOSC was previously demonstrated in our lab [16,27,28]. In general, composites containing NOSC presented a lower amount of ibuprofen released in comparison with the composites containing chitosan; this might be due to hydrophobic interaction between the C8 chain on the polymer and the drug.…”

“…This might indicate that pores are formed by the CNTs themselves which contribute to an increase in the hydrophobicity of the surface available for water sorption. The difference in behaviour of the two composites when CNTs are added could be linked to the superior ability of NOSC to disperse efficiently and homogeneuosly CNTs in aqueous environment [28]. …”

“…Figure 2 shows the morphology of CNTs as received. These are present as bundles of entangled tubes; therefore, before inclusion, CNTs were suspended in a solution of NOSC or chitosan by sonication, process known to stabilise and separate the CNTs into single entities [16,27,28]. Figure 3(a) shows the presence of some crystalline impurities in the HA control prepared in water; this is consistent with the earlier observation of the high conductivity measured in the washing medium, further confirmed by the high water absorption observed in the DVS study (see below).…”

Evaluation of Antibacterial and Cytotoxicity Properties of Silver Nanowires and Their Composites with Carbon Nanotubes for Biomedical Applications

“…As a control, a physical mixture of CNTs and AgNWs (AgNWs-CNT mix) was prepared. Briefly, N-octyl-O-sulphate chitosan (NOSC, 10 mg, synthetized as previously described [44]) was dissolved in 10 mL of purified water before the addition of 12.5 mg of CNTs. The sample was sonicated for 4 h. Then, 40 mL of deoxygenated water and 2 g of PVP were added to the mixture.…”

Stabilisation of Carbon Nanotube Suspensions

“…1.10). 65 Both TMC and NOSC polymers were synthesised from lowviscous chitosan, which has an average molecular weight of 200 kDa. The TMC and NOSC polymers present comparable thickness of coating, respectively 3.7-4.4 nm and 4.7 nm, as observed by AFM imaging (Fig.…”