Schizosaccharomyces pombe fed-batch culture in the presence of cadmium for the production of cadmium sulphide quantum semiconductor dots

In Vivo Biosynthesis of Inorganic Nanomaterials Using Eukaryotes-A Review

Bionanotechnology, the use of biological resources to produce novel, valuable nanomaterials, has witnessed tremendous developments over the past two decades. This eco-friendly and sustainable approach enables the synthesis of numerous, diverse types of useful nanomaterials for many medical, commercial, and scientific applications. Countless reviews describing the biosynthesis of nanomaterials have been published. However, to the best of our knowledge, no review has been exclusively focused on the in vivo biosynthesis of inorganic nanomaterials. Therefore, the present review is dedicated to filling this gap by describing the many different facets of the in vivo biosynthesis of nanoparticles (NPs) using living eukaryotic cells and organisms-more specifically, live plants and living biomass of several species of microalgae, yeast, fungus, mammalian cells, and animals. It also highlights the strengths and weaknesses of the synthesis methodologies and the NP characteristics, bio-applications, and proposed synthesis mechanisms. This comprehensive review also brings attention to enabling a better understanding between the living organisms themselves and the synthesis conditions that allow their exploitation as nanobiotechnological production platforms as these might serve as a robust resource to boost and expand the bio-production and use of desirable, functional inorganic nanomaterials.

Rhizopus stolonifer mediated biosynthesis of biocompatible cadmium chalcogenide quantum dots

We report an efficient method to biosynthesize biocompatible cadmium telluride and cadmium sulphide quantum dots from the fungus Rhizopus stolonifer. The suspension of the quantum dots exhibited purple and greenish-blue luminescence respectively upon UV light illumination. Photoluminescence spectroscopy, X-ray diffraction, and transmission electron microscopy confirms the formation of the quantum dots. From the photoluminescence spectrum the emission maxima is found to be 424 and 476nm respectively. The X-ray diffraction of the quantum dots matches with results reported in literature. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay for cell viability evaluation carried out on 3-days transfer, inoculum 3×10⁵ cells, embryonic fibroblast cells lines shows that more than 80% of the cells are viable even after 48h, indicating the biocompatible nature of the quantum dots. A good contrast in imaging has been obtained upon incorporating the quantum dots in human breast adenocarcinoma Michigan Cancer Foundation-7 cell lines.

Metal chalcogenide quantum dots: biotechnological synthesis and applications

Metal chalcogenide (metal sulfide, selenide and telluride) quantum dots (QDs) have attracted considerable attention due to their quantum confinement and size-dependent photoemission characteristics.

Microbial synthesis of chalcogenide semiconductor nanoparticles: a review

Chalcogenide semiconductor quantum dots are emerging as promising nanomaterials due to their size tunable optoelectronic properties. The commercial synthesis and their subsequent integration for practical uses have, however, been contorted largely due to the toxicity and cost issues associated with the present chemical synthesis protocols. Accordingly, there is an immediate need to develop alternative environment-friendly synthesis procedures. Microbial factories hold immense potential to achieve this objective. Over the past few years, bacteria, fungi and yeasts have been experimented with as eco-friendly and cost-effective tools for the biosynthesis of semiconductor quantum dots. This review provides a detailed overview about the production of chalcogen-based semiconductor quantum particles using the inherent microbial machinery.

Trichosporon jirovecii-mediated synthesis of cadmium sulfide nanoparticles

Cadmium sulphide is one of the most promising materials for solar cells and of great interest due to its useful applications in photonics and electronics, thus the development of bio-mediated synthesis of cadmium sulphide nanoparticles (CdS NPs) is one of the essential areas in nanoparticles. The present study demonstrates for the first time the eco-friendly biosynthesis of CdS NPs using the yeast Trichosporon jirovecii. The biosynthesis of CdS NPs were confirmed by UV-Vis spectrum and characterized by X-ray diffraction assay and electron microscopy. Scanning and transmission electron microscope analyses shows the formation of spherical CdS NPs with a size range of about 6-15 nm with a mean Cd:S molar ratio of 1.0:0.98. T. jirovecii produced hydrogen sulfide on cysteine containing medium confirmed by positive cysteine-desulfhydrase activity and the colony color turned yellow on 0.1 mM cadmium containing medium. T. jirovecii tolerance to cadmium was increased by the UV treatment and three 0.6 mM cadmium tolerant mutants were generated upon the UV radiation treatment. The overall results indicated that T. jirovecii could tolerate cadmium toxicity by its conversion into CdS NPs on cysteine containing medium using cysteine-desulfhydrase as a defense response mechanism.

Metal uptake and nanoparticle synthesis in hairy root cultures

: Hairy roots are a convenient experimental tool for investigating the interactions between plant cells and metal ions. Hairy roots of species capable of hyperaccumulating Cd and Ni have been applied to investigate heavy metal tolerance in plants; hairy roots of nonhyperaccumulator species have also been employed in metal uptake studies. Furnace treatment of hairy root biomass containing high concentrations of Ni has been used to generate Ni-rich bio-ore suitable for metal recovery in phytomining applications. Hairy roots also have potential for biological synthesis of quantum dot nanocrystals. As plant cells intrinsically provide the confined spaces needed to limit the size of nanocrystals, hairy roots cultured in bioreactors under controlled conditions are a promising vehicle for the manufacture of peptide-capped semiconductor quantum dots.

Accumulation of CdS nanoparticles by yeasts in a fed-batch bioprocess

The yeasts Schizosaccharomyces pombe and Candida glabrata were successfully cultivated in a fed-batch process at cadmium levels up to 100 mg l(-1). S. pombe incorporated 20 mg C dg(-1) dry biomass within 24h. C. glabrata accumulated 8 mg C dg(-1) dry biomass in 24h. The higher Cd uptake from S. pombe cells correlate with the elevated glucose concentrations during and at the end of the cultivation. Analysis of the cells with energy-filtering transmission electron microscopy-element specific imaging (EFTEM-ESI) revealed that cadmium is not precipitated outside the cells or at the cell wall but evenly distributed inside the cell plasma. As Cd is highly toxic this indicates that Cd is immobilized by an intracellular detoxification mechanism. Size exclusion chromatography showed that Cd is associated to a protein fraction between 25 and 67 kDa which corresponds to the theoretical molecular weight of CdS nanoparticles of 35 kDa coated with phytochelatins. This structure has been proposed in literature.

Labelling of cells with quantum dots

Colloidal quantum dots are semiconductor nanocrystals well dispersed in a solvent. The optical properties of quantum dots, in particular the wavelength of their fluorescence, depend strongly on their size. Because of their reduced tendency to photobleach, colloidal quantum dots are interesting fluorescence probes for all types of labelling studies. In this review we will give an overview on how quantum dots have been used so far in cell biology. In particular we will discuss the biologically relevant properties of quantum dots and focus on four topics: labelling of cellular structures and receptors with quantum dots, incorporation of quantum dots by living cells, tracking the path and the fate of individual cells using quantum dot labels, and quantum dots as contrast agents.