Retention of biological activity and near-infrared absorbance upon adsorption of horseradish peroxidase on single-walled carbon nanotubes

The objective of this study is to demonstrate the adsorption of horseradish peroxidase (HRP) on single-walled carbon nanotubes (SWNTs) using the sodium cholate suspension–dialysis method and to determine the effect of HRP adsorption on the biological activity of HRP and the UV–vis–NIR spectra of the SNWTs. The results indicate that this method results in a stable SWNT–protein suspension with complete retention of enzymatic activity of adsorbed HRP and also retention of a substantial fraction of the NIR absorption at 980 nm. The loading of protein on the SWNTs is high, and the overall yield of preparing the SWNT–protein suspension is also high. This process is promising for preparing SWNT–protein suspensions for biological applications where maintaining protein activity and SWNT absorption are important.