Quantification of Carbon Nanotubes Taken up by Macrophage Cells Using Optical Absorption Method

Quantification of the cellular uptake of nanomaterials is crucial for studies of their toxicity and medical applications. However, our knowledge of the behaviors of carbon nanotubes (CNTs) in cells or tissues remains incomplete due to the lack of appropriate methods for quantitative analysis. Here, we present a unique methodology for quantitatively assessing the cellular uptake of CNTs, taking advantage of their absorption of light in the near-infrared region. Measurement of CNT concentration in cell lysates by monitoring absorbance at 750 nm enabled highly accurate quantification of CNTs accumulated within cells. In a comparative study of eight commercially available CNTs with size ranging from 30 nm to 400 nm, we obtained the first quantitative evidence that cellular uptake of CNTs by RAW264.7 macrophages depends on the sizes, specifically on the widths of their bundles in dispersion, regardless of type or manufacturer.