Development of an accurate method for dispersion and quantification of carbon nanotubes in biological media

Understanding the biological effects triggered by nanomaterials is crucial, not only in nanomedicine but also in toxicology. The dose-response relation is relevant in biological tests due to its use for determining appropriate dosages for drugs and toxicity limits. Carbon nanotubes can trigger numerous unusual biological effects, many of which could have unique applications in biotechnology and medicine. However, their resuspension in saline solutions and the accurate determination of their concentration after dispersion in biological media are major handicaps to identify the magnitude of the response of organisms as a function of this exposure. This difficulty has led to inconsistent results and misinterpretations of their in vivo behavior, limiting their potential use in nanomedicine. The lack of a proper protocol that allows comparing different studies of the carbon nanotubes content and its adequate resuspension in culture cell media gives rise to this study. Here, we describe a methodology to functionalize, resuspend and determine the carbon nanotubes concentration in biocompatible media based on UV-Vis spectroscopy. This method allows us to accurately estimate the concentration of these resuspended carbon nanotubes, after removing bundles and micrometric aggregates, which can be used as a calibration standard, for dosage-dependent studies in biological systems. This method can also be extended to any other nanomaterial to properly quantify the actual concentration.