Abstract
The presence of heavy metals in increased concentrations in the environment has become a global environmental concern. This rapid increase in heavy metals in the environment is attributed to enhanced industrial and mining activities. Metal ions possess a lengthy half-life and property to bioaccumulate, are non-biodegradable and, thus, are a threat to the human health. A number of conventional spectroscopic and chromatographic techniques are being used for the detection of heavy metals, but these suffer from various limitations. Nano-based sensors have emerged as potential candidates for the sensitive and selective detection of heavy metals. Thus, the present study was focused on the synthesis of selenium nanoparticles (SeNPs) by using selenite-reducing bacteria in the development of a heavy metal toxicity biosensor. During the biosynthesis of selenium nanoparticles, supernatants of the overnight-grown culture were treated with Na2SeO32− and incubated for 24 h at 37 °C. The as-synthesized nanoparticles were characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and transmission electron microscopy (TEM) analyses. XRD and TEM results confirmed the formation of SeNPs in sizes ranging from 35 to 40 nm, with face-centered cubic (FCC) structures. The bioreduction process and validation of the formation of SeNPs was further confirmed by FTIR studies. The reduction in the biosynthesis of SeNPs using bacterial metabolite due to heavy metal cytotoxicity was analyzed by the colorimetric bioassay (SE Assay). The inhibition of selenite reduction and loss of red color in the presence of heavy metals may serve as a biosensor for heavy metal toxicity analysis. Thus, this biosensor development is aimed at improving the sensitivity and specificity of analytic detection.
Highlights
In recent decades, the continuous release of heavy metals into natural water bodies has become globally prevalent
A strong absorption band positioned at 520 nm, which originates from the surface plasmon resonances of selenium nanoparticles, was observed
A very rapid, biosynthesized, and ecofriendly agriculture sensor based on selenium nanoparticles (SeNPs) was developed for the detection of heavy metal toxicity
Summary
The continuous release of heavy metals into natural water bodies has become globally prevalent. A number of methods have been developed for the detection of heavy/toxic metals based on sensors. Mercury compounds were assayed amperometrically with the detection limits of 0.1 ng mL−1 Hg for HgCl2 and methylmercury, 0.2 ng mL−1 Hg for Hg2 (NO3 ) , and 1.7 ng mL−1 Hg for the mercury–glutathione complex This has encouraged us to synthesize a low-cost, less time-consuming, and portable platform for detection of the toxicity of heavy metals. Various nanomaterials, including metal and metal oxide nanoparticles, nanocomposites, carbon-based nanomaterials, etc., have been used to fabricate sensors for heavy metal detection [10] Owing to their size-dependent properties and high degree of functionality, nano-sensors exhibit increased sensitivity and selectivity [8]. We have endeavored to utilize the selenite-reducing rhizospheric bacteria Stenotrophomonas aidaminiphila to develop a SeNP-based biosensor for optical assessment of heavy metal toxicity. A biosensing application was used to analyze the presence of heavy metals in agricultural soil with the help of the selenium-based nano-biosensor, which could be applied for the bioremediation of toxic analytes in the presence of agricultural soil bacterial isolates
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