Characterisation of protein-nanoparticleconjugates

Depending on the nature of the nanoparticles, reactive oxygen species may be generated, thus disturbing the oxidative balance in the lung environment. The toxicity of the particle may be mitigated by components of the epithelial lining fluid, such as antioxidants. The presence of protein in the lining fluid could also resolve the biological effects of particle exposure. However, the mechanisms of protein-particle interaction remain unclear. Hydrophobic carbon-based nanoparticles were used to investigate the interactions between bovine serum albumin (BSA) and particles, including carbon black, which has an average diameter of 23 nm (CB23) or 65 nm (CB65); single-walled nanotubes (SWNTs), which have an average diameter of 1−2 nm (500 nm in length); and double-walled nanotubes (DWNTs), which have an average diameter of 5 nm (5−15 μm in length). The zeta potentials of the particles alone and of the protein-particle conjugates were determined (Figure 1). The zeta potentials of CB23, CB65, SWNTs and DWNTs dispersed in −0.4 mV d-H2O were 2.7, −3.9, −8.7 and 8.2 mV, respectively, and these values were significantly decreased to −24.3, −23.6, −19.3 and −20.4 mV, respectively, after the addition of −15.4 mV of BSA