جستجوی مقالات مرتبط با کلیدواژه "gold" در نشریات گروه "زیست شناسی"

Gold and silver nanoparticles are utilized in various industrial applications because of their unique properties. Physical, chemical, and green methods exist to synthesize these plasmonic nanoparticles. In green synthesis, biocompatible compounds, plants or their extracts, and microorganisms such as yeast, bacteria, actinobacteria, fungi, and algae are used to synthesize gold and silver nanoparticles. These biological sources have biomolecules that produce plasmonic gold and silver nanoparticles by reducing gold and silver ions. Green synthesis is easy, secure, high-yield, economically sensible, and eco-friendly. The synthesized nanoparticles should be characterized to determine their physiochemical properties (size, shape, surface, homogeneity, stability, and other properties). There are various techniques for the characterization of plasmonic nanoparticles, such as transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared, dynamic light scattering, and zeta potential. Gold and silver nanoparticles have diverse applications including antimicrobial and antitumor activities, usage in textile, food, and agriculture industries, wastewater treatment, and bioremediation. This review paper aims to introduce gold and silver nanoparticles and their synthesis approaches with an emphasis on green synthesis, explain different characterization techniques, and express the applications of these nanoparticles in biotechnology.

Nanocomposites are prepared from various materials that may have antibacterial activity. This study aimed to investigate antibacterial and antifungal activityies of nanocomposites of bohemite-gold and bohemite-gold-chitosan by help of aqeous extract of peppermint.

In the current study, the nanocomposites were prepared by exextracellular biosynthesis and antibacterial properties were investigated by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and killing-time curve by classic method of consecutive dilutions by Clinical & Laboratory Standards Institute.

The results showed that MIC and MBC were 10 µg/mL and 20 µg/mL for bohemite group, respectively. The results also showed that MIC and MBC were 2.50 µg/mL and 5 µg/mL against Acinetobacter baumannii and 5 µg/mL and 10 µg/mL against Escherichia coli, respectively. The greatest antibacterial activity for of bohemite-gold and bohemite-gold-chitosan was observed for a period of 6 to 24 h. Based on ourfindings, bohemite showed lower antibacterial activity compared with bohemite-gold and bohemite-gold-chitosan against the mentioned bacteria.

The prepared nanocomposites did not show any antifungal activity. Thus, bohemite-gold and bohemite-gold-chitosan nanocomposites have antibacterial activities against bacteria inducing infection in wound.

Since biological methods for metal extraction, such as bioleaching, are environmental friendly, there are high demands to be replaced with the chemical and physical methods. The aim of this study was to extract gold from Muteh sulfide ore by two microbial phases.
Isolation of iron oxidizing bacteria was performed by adding mineral samples into 9k medium. At the first phase of the mineral bioleaching process, the ores were cut into different diameters, and after adding the rocks to the standard medium (1%), they were assessed after 7 days by x-ray diffraction method to study the existence of sulfide minerals. The cyanide producer bacteria were isolated by growing into TSA solid medium. In the second phase, the materials obtained from first phase were exposed to cyanogen bacteria, and the sediments were investigated by ICP.
Based on the results, the isolated bacteria from Sarcheshmeh mining were able to oxidize strongly ferrous and to remove pyrite from ore after 7 days. In the second phase, the isolated bacteria from Tonekabon arable soil could remove gold of (0.023 mg/l). The best range of Au recovery was produced in pH 7.
The isolated bacteria in this study were able to separate Au in two phases of microbial process, consisting of sulfide mineralization and recovery from aqueous form by cyanide bacteria.

Biosynthesis of nanoparticle offers a vast studied today. Plant extracts are eco-friendly and cost effective to synthesis nanoparticles. In present study, has been presented a simple biosynthesis of gold nanoparticles usingZataria multiflora leaf’s extract.
The aqua extract from Zataria multiflora leaf’sextract was prepared. This extract in different concentration with HAuCl4 solution was mixed. Synthesized nanoparticle investigated by the change of color of auric chloride, and growth of nanoparticle in different time andconcentration was monitored by using UV-Vis Spectroscopy, transmission electron microscope (TEM) was used to analyze the shape and size nanoparticles, Energy-dispersive X-ray spectroscopy )EDS( analysis for evaluated present of gold element.
The colour of HAuCl4 solution change from yellow in color to ruby red, this confirmed that gold nanoparticle was fabricated. UV-visible spectroscopyshowed the absorbance peak of gold nanoparticles occur around 540 nm in Zataria multiflora leaf’sextract. TEM images of sample revealed that the nanoparticles were spherical, pantagon and shaped with no definite morphology. This nanoparticle were different from 1-50 nm in size. EDS analysis results showed absorption peak approximately at 2.30 keV due to presence of gold nanoparticles.
The results showed that gold nanoparticles canbe producedbyZataria multiflora leaf’sextract without usingenvironmentallyhazardouschemicalsunsuitable agent.

With the expanding of using nano materials and determining the risks, concerns have been raised about the safety of this technology for human health and the environment. A number of nano-materials without determining the environmental problems are now available for users without an appropriate safety assessment that may have harmful effects for human and environment in long time. The effects of these materials strongly depend on their shape, dimensions, size and the amount of using or exposure time. Nano materials are used in a wide range of areas such as using in monoclonal antibodies, peptides and or drugs. One of the most common application of these materials is in to combating microbes. A number of nanomaterials toxicity and their effects on DNA and the immune system are proven. With the recognition of the toxicity effects of some of the nano materials, scientist decided to determine the permissive levels of using these materials to prevent the environmental pollution.