Adsorption and inhibition of butyrylcholinesterase by different engineered nanoparticles

Butyrylcholinesterase (BChE), an important enzyme present in brain, serum and nervous system, is sensitive to neurotoxin. Engineered nanoparticles (NPs) may enter the mammalian body and be toxic. To investigate the potential neurotoxicity of different NPs and the interaction between NPs and BChE, three metal NPs (Cu–C, Cu and Al), three oxides NPs (SiO2, TiO2 and Al2O3), two carbon nanotubes (MWCNT and SWCNT) and two micro-scaled particles (Cu and activated carbon) were used to test their adsorption and inhibition on human serum BChE. At 800 mg L−1, adsorption and inhibition of BChE by MWCNT were the highest, 97% and 96%, respectively, while Al NPs showed the lowest adsorption (6.8%) and inhibition rates (3.3%). Ions could be dissolved in all metal and oxide NPs suspensions except TiO2 NPs. In comparison to other ions, Cu2+ released in Cu and Cu–C suspensions had the highest BChE activity reduction, 39.1% and 42.6%, respectively. The contribution of dissolved ions to the total inhibition by NPs suspension followed a decreasing sequence of Al (66%) > Cu (46%) > Cu–C (45%) > Al2O3 (44%) > SS1[SiO2] (25%) > SP1[SiO2] (4%), suggesting that the inhibition of BChE may partly result from ion dissolution from NPs. The inhibition of BChE by micro-scaled activated carbon and Cu particles was significantly lower than that of their nano-scaled particles. The inhibition of BChE by MWCNT, SWCNT, TiO2 (HR3) and Cu NPs showed concentration–response relationships. Their median inhibitory concentrations (IC50) were 97, 49, 206 and 1.54 mg L−1, respectively. These results indicate that these four NPs may have neurotoxicity and BChE may be potentially used as a biomarker of NPs in the environment.