Microarray analysis of the Escherichia coli response to CdTe-GSH Quantum Dots: understanding the bacterial toxicity of semiconductor nanoparticles

Abstract

BackgroundMost semiconductor nanoparticles used in biomedical applications are made of heavy metals and involve synthetic methods that require organic solvents and high temperatures. This issue makes the development of water-soluble nanoparticles with lower toxicity a major topic of interest. In a previous work our group described a biomimetic method for the aqueous synthesis of CdTe-GSH Quantum Dots (QDs) using biomolecules present in cells as reducing and stabilizing agents. This protocol produces nanoparticles with good fluorescent properties and less toxicity than those synthesized by regular chemical methods. Nevertheless, biomimetic CdTe-GSH nanoparticles still display some toxicity, so it is important to know in detail the effects of these semiconductor nanoparticles on cells, their levels of toxicity and the strategies that cells develop to overcome it.ResultsIn this work, the response of E. coli exposed to different sized-CdTe-GSH QDs synthesized by a biomimetic protocol was evaluated through transcriptomic, biochemical, microbiological and genetic approaches. It was determined that: i) red QDs (5 nm) display higher toxicity than green (3 nm), ii) QDs mainly induce expression of genes involved with Cd+2 stress (zntA and znuA) and tellurium does not contribute significantly to QDs-mediated toxicity since cells incorporate low levels of Te, iii) red QDs also induce genes related to oxidative stress response and membrane proteins, iv) Cd2+ release is higher in red QDs, and v) QDs render the cells more sensitive to polymyxin B.ConclusionBased on the results obtained in this work, a general model of CdTe-GSH QDs toxicity in E. coli is proposed. Results indicate that bacterial toxicity of QDs is mainly associated with cadmium release, oxidative stress and loss of membrane integrity. The higher toxicity of red QDs is most probably due to higher cadmium content and release from the nanoparticle as compared to green QDs. Moreover, QDs-treated cells become more sensitive to polymyxin B making these biomimetic QDs candidates for adjuvant therapies against bacterial infections.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1099) contains supplementary material, which is available to authorized users.

Biological Synthesis of CdS/CdSe Core/Shell Nanoparticles and Its Application in Quantum Dot Sensitized Solar Cells

“…On the other hand, an intense fluorescence emission was obtained when L-cysteine was used as a sulfur source for biosynthesis. In water, QDs production was observed at longer incubation times, between 6 and 24 h. As expected, best results were obtained when Borax-citrate was used as buffer (Monrás et al, 2014). CdS QDs biosynthesized this way are obtained faster and display the characteristic emission colors and intensities of this type of nanoparticles.…”

Flavoprotein-Mediated Tellurite Reduction: Structural Basis and Applications to the Synthesis of Tellurium-Containing Nanostructures

“…On the other hand, using enzymes to synthesize metal(loid)-containing NS is a relatively new process. Along this line, only the enzymatic synthesis of silver- ( Kumar et al, 2007a ), gold- ( Kumar et al, 2007b ; Scott et al, 2008 ), cadmium- ( Ansary et al, 2007 ), tellurium- ( Monrás et al, 2014 ), nickel-, lead-, and cobalt-containing nanostructures ( Ansary et al, 2012 ) has been described. So far, TeNS chemical synthesis to form nanopencils, nanorices, nanowires, and nanocubes has been reported ( Lin et al, 2012 ).…”

Tellurium: A Rare Element with Influence on Prokaryotic and Eukaryotic Biological Systems

“…Duganella violacienigra can reduce both Se and Te oxyanions and so it can be exploited in bioremediation and in eco-friendly approaches to produce rare element nanoparticles, rather than synthesising them by chemical means [ 29 ]. Se, Te and other elements such as cadmium (Cd) and sulphur (S) are also used in the production of semiconductor nanoparticles (NPs) or quantum dots (QDs) with unique fluorescent properties and great technological potential [ 114 , 115 ]. Shewanella oneidensis MR-1 is another metal-reducing bacterium that reduces TeO 3 2− giving intracellularly accumulated needle-shaped crystalline Te 0 nanorods.…”