Adsorption and interactions of the bovine serum albumin-double walled carbon nanotube system

Adsorption and interactions of Bovine Serum Albumin (BSA) with Double Walled Carbon Nanotubes (DWNT) prepared by catalytic chemical vapor deposition (CCVD) synthesis were studied. Adsorption kinetics and equilibrium were investigated by means of in situ UV-spectroscopy. The extent of adsorption at different temperatures was determined at the end of a 420-min adsorption period. The adsorption equilibrium experiments were performed using various amounts of nanotubes at pH 4 and 40 °C, and the adsorption parameters were evaluated comparing the experimental data with models such as the Freundlich and Langmuir isotherms. The maximum protein adsorption capacity (Q0) of DWNT was determined as 1221 mg·g− 1. The effect of temperature on the adsorption rate experiments was investigated for constant amount of adsorbent at pH 4. Adsorption kinetics followed the pseudo-first-order rate. Zeta potential measurements were performed with respect to solution pH for understanding the protein-surface interactions. The interactions between positively charged BSA molecules with negatively charged DWNT at pH 4 were found to be electrostatic attractions. Thermodynamic parameters, ΔH0 and ΔS0 were found as 9.40 kJ·mol− 1 and 321.5 J·mol− 1 K− 1, respectively. ΔH0 value indicated that BSA adsorption on DWNT was a physisorption process.