Abstract
Nanomaterials are extensively used in consumer products and medical applications, but little is known about their environmental and biological toxicities. Moreover, the toxicity analysis requires sophisticated instruments and labor-intensive experiments. Here we report a microfluidic chip incorporated with the nematode Caenorhabditis elegans that rapidly displays the changes in body growth and gene expression specifically responsive to the silver nanoparticles (AgNPs). C. elegans were cultured in microfluidic chambers in the presence or absence of AgNPs and were consequently transferred to wedge-shaped channels, which immobilized the animals, allowing the evaluation of parameters such as length, moving distance, and fluorescence from the reporter gene. The AgNPs reduced the length of C. elegans body, which was easily identified in the channel of chip. In addition, the decrease of body width enabled the worm to advance the longer distance compared to the animal without nanoparticles in a wedge-shaped channel. The transgenic marker DNA, mtl-2::gfp was highly expressed upon the uptake of AgNPs, resulting in green fluorescence emission. The comparative investigation using gold nanoparticles and heavy-metal ions indicated that these parameters are specific to AgNPs. These results demonstrate that C. elegans-on-a-chip has a great potential as a rapid and specific nanoparticle detection or nanotoxicity assessment system.
Highlights
AgNPs have been shown to be toxic to C. elegans in multiple ways, causing protein or DNA damage, oxidative stress, reduced survival, reduced reproductive capacity, and inhibition of growth[20,21,22]
A novel nanoparticle assessment system based on a microfluidic chip that efficiently and rapidly visualizes the uptake and toxicity of the silver nanoparticles in C. elegans has been demonstrated for the purpose of both in situ and in vivo monitoring of nanomaterials
The size and morphology of the AgNPs dispersed in deionized water were determined by the analysis of the transmission electron microscope (TEM) images
Summary
AgNPs have been shown to be toxic to C. elegans in multiple ways, causing protein or DNA damage, oxidative stress, reduced survival, reduced reproductive capacity, and inhibition of growth[20,21,22]. One of several immobilization methods can be used; worms can be immobilized using glue[25,26], by treatment with sodium azide[27], or by using anesthetics such as levamisole[28] These methods are well established and broadly accepted, they have limitations, including the potential for the occurrence of changes in the worm’s biochemical state and the potential for toxicity. Microfluidic devices that are capable of handling and immobilizing C. elegans have been developed of late, and these devices have been successfully applied in sorting[29], imaging[30,31] and chemo-sensing[32,33,34] In these approaches, the moving worm can be immobilized using one of the available techniques, including the introduction of a gelatinous fluid[35], compression or restriction by pneumatic valves[36], or physical restriction using a wedge-shaped clamp channel[24]. Other heavy metal ions and nanoparticles with a similar size were examined using the developed system to determine a selectivity of the animal-on-a-chip
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