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Adsorption of Biomolecules in the Organism Body and PAHs on Engineered Nanoparticles

Author: ZhaoJian
Tutor: WangZhenYu
School: Ocean University of China
Course: Environmental Science
Keywords: nanoparticles acetylcholinesterase adsorption polycyclic aromatichydrocarbons pulmonary surfactant
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Type: PhD thesis
Year: 2011
Downloads: 148
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Abstract


Engineered nanoparticles （NPs） are increasingly being used in various applications（e.g., electronics, biomedicine, catalysis and material science）. During their produceand use, NPs could release to the environment, the potential harmful impacts onhumans and the environment are attracting increasing research and public attention.These NPs can be toxic via interactions with biomolecules such as proteins andenzymes after entering the human body. Moreover, NPs, especially carbon nanotubes（CNTs） can be carriers of polycyclic aromatic hydrocarbons （PAHs） because of theirhigh adsorption affinity and capacity. Thus, CNTs and PAHs have possibility toexhibit co-toxicity. Therefore, we aim to study the adsorption behavior of biomeculesin the nervous, gastrointestinal and respiratory systems on CNTs, and bioaccessibilityof adsorbed PAHs on CNTs in the presence of biomolecules.Acetylcholinesterase （AChE） is a key enzyme of nervous system present in thebrain and blood. A modified Ellman assay was used to measure AChE activitybecause NPs could adsorb the yellowish product （5-MNBA） during the colordevelopment. All the tested NPs, SiO2, TiO2, Al2O3, Al, Cu, Cu-C （carbon-coatedcopper）, multi-walled carbon nanotubes （MWCNT） and single-walled carbonnanotubes （SWCNT） could inhibit AChE activity. Carbon nanotubes had high affinityfor AChE adsorption, the highest being SWCNT （94%）. Nano SiO2and Al2O3showed the lowest adsorption. Inhibition by the tested NPs was primarily caused byadsorption. However, Cu2+release in Cu and Cu-C NPs suspensions caused40%and45%of AChE activity reduction, respectively. AChE inhibition by bulk Cu andactivated carbon particles was also measured for comparison, showing that theinhibition by bulk particles was lower than their counterpart NPs. AChE inhibition byCu, Cu-C, MWCNT and SWCNT had dose-response relationships, and their medianinhibitory concentrations (IC50) were4,17,156and96mg L-1, respectively, showingthat these NPs may have neurotoxicity and should pay more attention. Besides the high adsorption capability of CNTs to biomolecules, CNTs could alsostrongly adsorb hydrophobic organic contaminants such as polycyclic aromatichydrocarbons （PAHs）. Adsorption and desorption of PAHs on CNTs in the simulatedgastrointestinal fluids were examined. Adsorption of phenanthrene on CNTs wassuppressed by pepsin and bile salts due to competitive sorption and solubilization ofphenanthrene by pepsin and bile salts. Desorption kinetics study showed that therapidly desorbing phase was lasted less than1h for all CNTs. Further,43%-69%ofphenanthrene was released from CNTs after fasted state and fed state gastrointestinaldigestion. The digested （released） phenanthrene could rapidly adsorb by the humanbody, thus exhibiting toxicity.When the phenanthrene adsorbed CNTs enter the respiratory tract, pulmonarysurfactant influences the bioaccessibility of phenanthrene. We studied the adsorptionof phenanthrene on pulmonary surfactant （Curosurf） and its components （DPPC andBSA） using a Passive Dosing method. It was showed that solubilization （adsorption）of phenanthrene by Curosurf, DPPC or BSA was linear, and phenanthrenesolubilization by Curosurf was much higher than the single component （DPPC orBSA）. The solubilization effect of the lipid mixture was higher than the sum of therespective effects of the mixture components. In the presence of Curosurf, DPPC orBSA, adsorption of phenanthrene was suppressed, showing competitive adsorptionbetween pulmonary surfactant （or DPPC, BSA） and phenanthrene. The competitiveadsorption between Curosurf and phenanthrene was the strongest. Therefore, whenPAHs adsorbed CNTs entered the respiratory tract, part of PAHs were desorbed fromCNTs due to solubilization and competitive adsorption. The desorbed phenanthrenecould have health risk to the human body.

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