The objective of this study is to demonstrate the adsorption of horseradish peroxidase(HRP) on single-walled carbon nanotubes (SWNTs) using the sodium cholatesuspension–dialysis method and to determine the effect of HRP adsorption on thebiological activity of HRP and the UV–vis–NIR spectra of the SNWTs. The resultsindicate that this method results in a stable SWNT–protein suspension with completeretention of enzymatic activity of adsorbed HRP and also retention of a substantial fractionof 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 biologicalapplications where maintaining protein activity and SWNT absorption are important.