Nanomaterials are increasingly being used in new products and devices with a great impact on different fields from sensoristics to biomedicine. Biosynthesis of nanomaterials by microorganisms is recently attracting interest as a new, exciting approach towards the development of 'greener' nanomanufacturing compared to traditional chemical and physical approaches. This review provides an insight about microbial biosynthesis of nanomaterials by bacteria, yeast, molds, and microalgae for the manufacturing of sensoristic devices and therapeutic/diagnostic applications. The last ten-year literature was selected, focusing on scientific works where aspects like biosynthesis features, characterization, and applications have been described. The knowledge, challenges, and potentiality of microbial-mediated biosynthesis was also described. Bacteria and microalgae are the main microorganism used for nanobiosynthesis, principally for biomedical applications. Some bacteria and microalgae have showed the ability to synthetize unique nanostructures: bacterial nanocellulose, exopolysaccharides, bacterial nanowires, and biomineralized nanoscale materials (magnetosomes, frustules, and coccoliths). Yeasts and molds are characterized by extracellular synthesis, advantageous for possible reuse of cell cultures and reduced purification processes of nanomaterials. The intrinsic variability of the microbiological systems requires a greater protocols standardization to obtain nanomaterials with increasingly uniform and reproducible chemical-physical characteristics. A deeper knowledge about biosynthetic pathways and the opportunities from genetic engineering are stimulating the research towards a breakthrough development of microbial-based nanosynthesis for the future scaling-up and possible industrial exploitation of these promising 'nanofactories'.

Microbial Nanotechnology: Challenges and Prospects for Green Biocatalytic Synthesis of Nanoscale Materials for Sensoristic and Biomedical Applications.

Biosynthesis of cobalt oxide nanoparticles using endophytic fungus Aspergillus nidulans.

Biologically synthesized PbS nanoparticles for the detection of arsenic in water

Present investigation is focused on the development of environment friendly protocol for ZnO nanoparticles synthesis using mycelial free filtrate of unexplored endophytic fungus Cochliobolus geniculatus. Zinc metal tolerant endophyte was isolated from leaves of Nothapodytes foetida and identified based on rDNA internal transcribed spacer region sequence. Surface plasmon resonance examined by UV–VIS spectroscopy analysis confirmed the synthesis of ZnO nanoparticles; exhibiting a band gap of 3.28 eV. The obtained nanoparticles were characterized by energy dispersive X-ray (EDX), high resolution transmission electron microscopy and XRD analysis. The synthesized ZnO nanoparticles were found to be polydispersed and well distributed deprived of agglomeration, crystalline, quasi spherical particles exhibiting a narrow range distribution. Fluorescence, FTIR and UV–VIS spectra depicted presence of extracellular proteins which was further confirmed by SDS-PAGE study that displayed occurrence of 52 kDa and 58 kDa protein bands involved in the synthesis of ZnO nanoparticles and further act as capping material.

Mechanistic insight into the endophytic fungus mediated synthesis of protein capped ZnO nanoparticles

Recently, several nonconventional sources have emerged as strong hotspots for the biosynthesis of chalcogenide quantum dots. However, studies that have ascertained the biomimetic methodologies that initiate biosynthesis are rather limited. The present investigation portrays a few perspectives of rare-earth(Gd)-doped ZnS biosynthesis using the endophytic fungi Aspergillus flavus for sensing metals based on their fluorescence. Analysis of ZnS:Gd nanoparticles was performed by elemental analysis, energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), and transmission electron microscopy (TEM). The results of TEM demonstrated that the particles were polycrystalline in nature, with a mean size of 10–18 nm. The fluorescence amenability of the biogenic ZnS nanoparticles was further used for the development of a simple and efficient sensing array. The results showed sensitive and detectable quenching/enhancement in the fluorescence of biogenic colloidal ZnS nanoparticles, in the presence of Pb (II), Cd (II), Hg (II), Cu (II) and Ni (II), respectively. The fluorescence intensity of the biogenic ZnS:Gd nanoparticles was found to increase compared to that of the ZnS nanoparticles that capacitate these systems as a reliable fluorescence sensing platform with selective environmental applications.

https://www.mdpi.com/2313-7673/4/1/11/pdf

Bioinspired ZnS:Gd Nanoparticles Synthesized from an Endophytic Fungi Aspergillus flavus for Fluorescence-Based Metal Detection.

The development of reliable and eco-friendly processes for the synthesis of metal sulphide quantum dots has been considered as a major challenge in the field of nanotechnology. In the present study, polycrystalline ZnS quantum dots were synthesized from an endophytic fungus Aspergillus flavus . It is noteworthy that apart from being rich sources of bioactive compounds, endophytic fungus also has the ability to mediate the synthesis of nanoparticles. TEM and DLS revealed the formation of spherical particles with an average diameter of about 18 nm and 58.9 nm, respectively. The ZnS quantum dots were further characterized using SEM, EDAX, XRD, UV–visible spectroscopy and FTIR. The obtained results confirmed the synthesis of polycrystalline ZnS quantum dots and these quantum dots are used for studying ROS activity. In addition this paper explains kinetics of metal sorption to study the role of biosorption in synthesis of quantum dots by applying Morris-Weber kinetic model. Since Aspergillus flavus is isolated from a medicinal plant Nothapodytes foetida, quantum dots synthesized from this fungus may have great potential in broad environmental and medical applications.

Raj Mohan B

Papers

Biologically synthesized PbS nanoparticles for the detection of arsenic in water

ZnS semiconductor quantum dots production by an endophytic fungus Aspergillus flavus