Neurotoxicity of tetramethylammonium ion on larval and juvenile zebrafish:Effects on neurobehaviors and multiple biomarkers

Tetramethylammonium hydroxide(TMAH)is an important compound that utilized and released by the rapidly expanding semiconductor industry,which could hardly be removed by the conventional wastewater treatment techniques.As a cholinergic agonist,the tetramethylammonium ion(TMA^(+))has been reported to induce toxicity to muscular and respiratory systems of mammals and human,however the toxicity on aquatic biota remains poorly known.We investigated the neurotoxic effects of TMA^(+)exposure on zebrafish,based on neurobehavior tests and a series of biomarkers.Significant inhibitions on the swimming distance of zebrafish larvae were observed when the exposure level exceeded 50 mg/L,and significant alterations on swimming path angles(straight and deflective movements)occurred even at 10 mg/L.The tested neurobehavioral endpoints of zebrafish larvae were significantly positively correlated with reactive oxygen species(ROS)and malondialdehyde(MDA),significantly negatively related with the activities of antioxidant enzymes,but not significantly correlated with the level of acetylcholinesterase(AChE).Such relationship indicates that the observed neurotoxic effects on swimming behavior of zebrafish larvae is mainly driven by oxidative stress,rather than the alterations of neurotransmitter.At the highest exposure concentration(200 mg/L),TMA^(+)evoked more severe toxicity on zebrafish juveniles,showing significantly stronger elevation on the MDA activity,and greater inhibitions on the activities of antioxidant enzymes and ACh E,suggesting juveniles were more susceptible to TMA^(+)exposure than larval zebrafish.

Asymmetric side-chain engineering of organic semiconductor for ultrasensitive gas sensing

Molecular structure of organic semiconductor plays a critical role in determining the performance and functionality of organic electronic devices,by optimizing the electrical,optical and physicochemical properties.Substituted alkyl chains are fundamental units in tailering the solubility and assemblability,among which the asymmetric properties have been reported as key element for controlling the packing motifs and intrinsic charge transport.Here,we expanded the scope of molecular asymmetry dependent sensing features based on a new series of naphthalene diimides(NDI)-based derivatives substituted with a same branching alkyl chain but various linear-shaped alkyl chains(Cn-).A clear molecular stacking change,from head-to-head bilayer to head-to-tail monolayer packing model,is observed based on the features of anisotropic molecular interactions with the change in the chain length.Most importantly,a unique LUMO level shift of 0.17 eV is validated for NDI-PhC4,providing a record sensitivity up to 150%to 0.01 ppb ammonia,due to the desired molecular reactivity and device amplification properties.These results indicate that asymmetric side-chain engineering opens a route for breath healthcare.