title: Multi-walled carbon nanotubes decrease lactate dehydrogenase activity in enzymatic reaction.
abstract: The oxidation of 1, 4-nicotinamide adenine dinucleotide (NADH) to β-nicotinamide adenine dinucleotide (NAD(+)) coupled with converting of pyruvic acid (PA) to lactate catalyzed by lactate dehydrogenase (LDH), NADH+PA+H(+)⇌LDHNAD(+)+Lactate, was widely adopted to quantify the cell's death, membrane infiltration and proliferation induced by potential toxins. The differential pulse voltammetry (DPV) cathodic signal of NAD(+) at a hanging mercury drop electrode (HMDE) showed LDH activity decreased with the elevating dosages of and the pre-contact time (t(c)) with multi-walled carbon nanotubes (MWCNTs). Comparison of kinetic rate constant of above enzymatic reaction (ER) was able to sensitively assay the adverse influence of MWCNTs. Toxic concentration of altering relative LDH activity by 50% (TC(50)) of MWCNTs was derived to be 40mg/L. TC(50) values indicated a decrease toxicity order Al (III)>MWCNTs>nano-Al(13)>50nm-Al(2)O(3)≥1000nm-Al(2)O(3). The negatively charged surfaces of these nanoparticles (NPs) might be a main cause for the decrement of LDH activity. This decrement was capable to result in the underestimation of the toxicity of NPs in classic LDH assays. This observation would highlight to settle down contradictory medium dependent toxicity of MWCNTs among the literature.
authors: School of Chemistry and Chemical Engineering, State Key Laboratory of Coordination Chemistry, and MOE Key Laboratory for Life Science,Nanjing University, China.
authors: Fuping
authors: F
authors: Zhang
authors: Na
authors: N
authors: Wang
authors: Jin
authors: J
authors: Kong
authors: Jianyuan
authors: J
authors: Dai
authors: Fang
authors: F
authors: Chang
authors: Guiying
authors: G
authors: Feng
authors: Shuping
authors: S
authors: Bi