Pharmaceutical characterization of solid and dispersed carbon nanotubes as nanoexcipients

Abstract

Background: Carbon nanotubes (CNTs) are novel materials with considerable potential in many areas related to nanomedicine. However, a major limitation in the development of CNT-based therapeutic nanomaterials is a lack of reliable and reproducible data describing their chemical and structural composition. Knowledge of properties including purity, structural quality, dispersion state, and concentration are essential before CNTs see widespread use in in vitro and in vivo experiments. In this work, we describe the characterization of several commercially available and two in-house-produced CNT samples and discuss the physicochemical profiles that will support their use in nanomedicine. Methods: Eighteen single-walled and multi-walled CNT raw materials were characterized using established analytical techniques. Solid CNT powders were analyzed for purity and structural quality using thermogravimetric analysis and Raman spectroscopy. Extinction coefficients for each CNT sample were determined by ultraviolet-visible near infrared absorption spectroscopy. Standard curves for each CNT sample were generated in the 0-5 µg/mL concentration range for dispersions prepared in 1,2-dichlorobenzene. Results: Raman spectroscopy and thermogravimetric analysis results demonstrated that CNT purity and overall quality differed substantially between samples and manufacturer sources, and were not always in agreement with purity levels claimed by suppliers. Absorbance values for individual dispersions were found to have significant variation between individual single-walled CNTs and multi-walled CNTs and sources supplying the same type of CNT. Significant differences (P , 0.01) in extinction coefficients were observed between and within single-walled CNTs (24.9-53.1 mL·cm ). The results described here suggest a considerable role for impurities and structural inhomogeneities within individual CNT preparations and the resulting spectroscopic properties of their dispersions. Conclusion: Raw CNT materials require thorough analytical workup before they can be used as nanoexcipients. This applies especially to the determination of CNT purity, structure, and concentration. The results presented here clearly demonstrate that extinction coefficients must be determined for individual CNT preparations prior to their use.

Ruthenium Catalyst Supported on Multi-Walled Carbon Nanotubes for CO Oxidation

“…Figure 7 shows the spectra of the carbon nanotube and the catalyst. The spectrum of the MWCNT showed the peaks at bands D (≈1340 cm −1 ), G (≈1572 cm −1 ), 2D (≈2663 cm −1 ), G + D (≈2919 cm −1 ), in accordance with Zdrojek et al [39] and noise bands between 100 and 200 cm −1 , as observed by Ivanova et al [40]. However, the spectrum of the catalyst sample showed extra peaks, which could be correlated to impurities (≈2330 cm −1 , 800 cm −1 and 270 cm −1 ).…”

Investigating a transcriptomic approach on marine mussel hemocytes exposed to carbon nanofibers: An in vitro/in vivo comparison

“…For this reason, irradiation of the samples started 30 s before acquisition to limit this phenomenon. It is important to note that Raman spectroscopy does not allow a direct measurement of the chemical purity of the samples but more of the level of structural defects (Ivanova et al, 2012). In the context of SbD and the case study this is important because the structural quality of the CNFs may impact the performance of the products and GATam may be a more desirable product than GANF as a result.…”

Optical and Morphological Studies of Multiwalled Carbon Nanotube-Incorporated Poly(3-hexylthiophene-2,5-diyl) Nanocomposites

“…The peak at 1379 cm −1 corresponds to the C-C symmetric bending vibrations of the thiophene ring, whereas that at 1443 cm −1 belonged to the symmetric C=C stretching mode of P3HT. (23,24) Both peaks are sensitive to π-electron delocalisation (conjugation length) and thus indicate the degree of molecular order in P3HT films. (23) On the other hand, the intensity ratio of the Raman disorder (D)-band to the graphite (G)-band is often used to estimate the density of structural defects found in CNTs.…”