Pharmaceutical characterization of solid and dispersed carbon nanotubes as nanoexcipients
Open Access
- 1 January 2012
- journal article
- research article
- Published by Taylor & Francis Ltd in International Journal of Nanomedicine
- Vol. 7, 403-415
- https://doi.org/10.2147/ijn.s27442
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-1•mg-1) and multi-walled CNTs (49.0–68.3 mL•cm-1•mg-1). 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.Keywords
This publication has 19 references indexed in Scilit:
- Regulating Nanomedicine – Can the FDA Handle It?Current Drug Delivery, 2011
- Applications of TGA in quality control of SWCNTsAnalytical and Bioanalytical Chemistry, 2009
- Current activities of ISO TC229/WG2 on purity evaluation and quality assurance standards for carbon nanotubesAnalytical and Bioanalytical Chemistry, 2009
- Carbon nanotubes in biology and medicine: In vitro and in vivo detection, imaging and drug deliveryNano Research, 2009
- Carbon nanotubes as functional excipients for nanomedicines: II. Drug delivery and biocompatibility issuesNanomedicine: Nanotechnology, Biology and Medicine, 2008
- Carbon nanotubes as functional excipients for nanomedicines: I. pharmaceutical propertiesNanomedicine: Nanotechnology, Biology and Medicine, 2008
- Biological properties of carbon nanotubes.Journal of Nanoscience and Nanotechnology, 2007
- Carbon nanotubes as nanomedicines: From toxicology to pharmacologyAdvanced Drug Delivery Reviews, 2006
- Nanotechnology: Intelligent Design to Treat Complex DiseasePharmaceutical Research, 2006
- Carbon Nanotubes as Intracellular Transporters for Proteins and DNA: An Investigation of the Uptake Mechanism and PathwayAngewandte Chemie, 2006