Biosynthesis of luminescent quantum dots in an earthworm

Abstract

The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co(3)O(4)) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl(2) and Na(2)TeO(3) salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.

Ultra-small fluorescent inorganic nanoparticles for bioimaging

“…Silica is one of the most popular inert materials used for surface modification, and has a few distinct advantages, 65 including: (1) a non-porous silica shell 20 that the earthworm's metal detoxification pathway can be exploited to produce water-soluble and biocompatible CdTe QDs. 59 This bioapproach is time-consuming (11 days), however, and the resultant QDs have a low fluorescence QY (8%), so this method cannot be used for large-scale preparation. 25 …”

Biosynthesis of Quantum Dots and Their Potential Applications in Biology and Biomedicine

“…The particles demonstrated an absorption band edge of 450 nm with a slight excitonic feature at 360 nm, consistent with CdTe QDs. The observed green emission from the QDs was determined to be near the band edge, with Stokes shifted emission maxima at 520 nm and a second weaker component at 460 nm from residual autofluorescence [42]. High-resolution electron microscopy analyses confirmed the presence of crystalline nanoparticles with an average diameter of 2.33 + 0.59 nm (100 particles measured) and clear lattice fringes, while selective area electron diffraction (SAED) demonstrated diffuse rings consistent with CdTe nanoparticles.…”

“…This is achieved using an isolation strategy that relies on metallothioneins-a family of cysteine-rich proteins-to transport heavy metals to the chloragogenous tissues (cells that resemble the liver in vertebrates) where toxins are neutralized [41,42]. Although the cadmium detoxification system in earthworms is well established, little is known regarding the uptake, trafficking, and storage dynamics of tellurium.…”

“…Although the cadmium detoxification system in earthworms is well established, little is known regarding the uptake, trafficking, and storage dynamics of tellurium. Authors suggested that the tellurite was reduced by glutathione reductase, reduced nicotinamide adenine dinucleotide phosphate (NADPH) and glutathione (GSH) via the GS-Te-SG complex, to H 2 Te, a common Te precursor, and thus able to react with the available Cd 2+ [42]. Earthworms exposed for 11 days to standard soil spiked with CdCl 2 and Na 2 TeO 3 were shown to transport the precursors, via metallated metallothionein complexes, to the chloragogenous tissue located at the coelomic surfaces of the worm gut, where they reacted to form QDs before isolation.…”

ATP synthesis in the energy metabolism pathway: a new perspective for manipulating CdSe quantum dots biosynthesized in <em>Saccharomyces cerevisiae</em>

“…11 Various nanoparticles are reported that are biosynthesized by bacteria, [12][13][14] fungi, 15,16 plants, 17,18 mammalian cells, 19 or even earthworms. 20 Considering the simple culture methods, the low cost of the equipment, and the easy way to get the gradients, the biosynthesis of nanoparticles using microorganisms is the most economic and common approach.…”