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A novel bacterial isolate Stenotrophomonas maltophilia as living factory for synthesis of gold nanoparticles.

Nangia Y, Wangoo N, Goyal N, Shekhawat G, Suri CR - Microb. Cell Fact. (2009)

Bottom Line: Gold nanoparticles were characterized and found to be of ~40 nm size.Electrophoresis, Zeta potential and FTIR measurements confirmed that the particles are capped with negatively charged phosphate groups from NADP rendering them stable in aqueous medium.The process of synthesis of well-dispersed nanoparticles using a novel microorganism isolated from the gold enriched soil sample has been reported in this study, leading to the development of an easy bioprocess for synthesis of GNPs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh 160036, India. raman@imtech.res.in.

ABSTRACT

Background: The synthesis of gold nanoparticles (GNPs) has received considerable attention with their potential applications in various life sciences related applications. Recently, there has been tremendous excitement in the study of nanoparticles synthesis by using some natural biological system, which has led to the development of various biomimetic approaches for the growth of advanced nanomaterials. In the present study, we have demonstrated the synthesis of gold nanoparticles by a novel bacterial strain isolated from a site near the famous gold mines in India. A promising mechanism for the biosynthesis of GNPs by this strain and their stabilization via charge capping was investigated.

Results: A bacterial isolate capable of gold nanoparticle synthesis was isolated and identified as a novel strain of Stenotrophomonas malophilia (AuRed02) based on its morphology and an analysis of its 16S rDNA gene sequence. After 8 hrs of incubation, monodisperse preparation of gold nanoparticles was obtained. Gold nanoparticles were characterized and found to be of ~40 nm size. Electrophoresis, Zeta potential and FTIR measurements confirmed that the particles are capped with negatively charged phosphate groups from NADP rendering them stable in aqueous medium.

Conclusion: The process of synthesis of well-dispersed nanoparticles using a novel microorganism isolated from the gold enriched soil sample has been reported in this study, leading to the development of an easy bioprocess for synthesis of GNPs. This is the first study in which an extensive characterization of the indigenous bacterium isolated from the actual gold enriched soil was conducted. Promising mechanism for the biosynthesis of GNPs by the strain and their stabilization via charge capping is suggested, which involves an NADPH-dependent reductase enzyme that reduces Au3+ to Au0 through electron shuttle enzymatic metal reduction process.

No MeSH data available.


Related in: MedlinePlus

UV-vis spectra of GNPs solutions prepared by resuspending the biomass of Stenotrophomonas maltophilia for different time intervals in the presence of 1 mM HAuCl4.
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Figure 4: UV-vis spectra of GNPs solutions prepared by resuspending the biomass of Stenotrophomonas maltophilia for different time intervals in the presence of 1 mM HAuCl4.

Mentions: A solution of gold chloride in a suspension of cell mass of Stenotrophomonas maltophilia changed progressively from light yellow to cherry red at temperature 25°C showing formation of gold nanoparticles. Control experiments, without the addition of biomass as well as with heat-killed cells, showed no change in color of suspension (Fig. 3a) confirming the formation of GNPs in the presence of biomass only. The kinetics of the reaction was studied using UV-vis spectroscopy by recording spectra from the colloidal gold solutions obtained after disrupting the cells, which were resuspended with HAuCl4 solution for different time intervals. The spectra revealed a strong absorption at nearly 530 nm after 8 hrs of incubation at 25°C, gradually showing a red shift with time at 25°C (Fig 4 curves bottom to top). The intense plasmon resonance band indicated the formation of spherical gold nanoparticles of approximately 40 nm in diameter [18]. Size distribution of GNPs was confirmed by coating a drop of the supernatant solution of disrupted cell suspension by TEM imaging. The images demonstrate gold nanoparticles possessing an average diameter of 40 nm (± 15%) as depicted in (Fig. 3b). Cryo TEM imaging of the thin sections of stained AuRed02 strain after reacting the biomass with gold chloride solution for 8 h showed the presence of gold nanoparticles on the inner cytoplasmic membrane (see Additional file 1, S1). It is likely that some gold ions (Au3+) cross the cell barrier through ion-transport channel and are reduced by the enzymes present on the cytoplasmic membrane and within the cytoplasm. Energy dispersive spectroscopy analysis (EDS) confirmed the presence of gold nanoparticles in the suspension. The spectra (Fig. 3c) present major Au peaks at approximately 2 keV besides several other peaks of C, O, and Si which might be due to the chemical composition of the sample substrate used in the EDS analysis. These results show that the strain Stenotrophomonas maltophilia could effectively synthesize GNPs of different sizes by resuspending the biomass for different time intervals in the presence of HAuCl4 (Fig. 4). The colored solution of GNPs remained stable for more than 2-weeks of storage at 4°C indicating the capping of GNPs with some charged groups. FTIR analysis of these GNPs further confirmed the capping of GNPs by phosphate groups (900 cm-1) (see Additional file 1, S2).


A novel bacterial isolate Stenotrophomonas maltophilia as living factory for synthesis of gold nanoparticles.

Nangia Y, Wangoo N, Goyal N, Shekhawat G, Suri CR - Microb. Cell Fact. (2009)

UV-vis spectra of GNPs solutions prepared by resuspending the biomass of Stenotrophomonas maltophilia for different time intervals in the presence of 1 mM HAuCl4.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2719591&req=5

Figure 4: UV-vis spectra of GNPs solutions prepared by resuspending the biomass of Stenotrophomonas maltophilia for different time intervals in the presence of 1 mM HAuCl4.
Mentions: A solution of gold chloride in a suspension of cell mass of Stenotrophomonas maltophilia changed progressively from light yellow to cherry red at temperature 25°C showing formation of gold nanoparticles. Control experiments, without the addition of biomass as well as with heat-killed cells, showed no change in color of suspension (Fig. 3a) confirming the formation of GNPs in the presence of biomass only. The kinetics of the reaction was studied using UV-vis spectroscopy by recording spectra from the colloidal gold solutions obtained after disrupting the cells, which were resuspended with HAuCl4 solution for different time intervals. The spectra revealed a strong absorption at nearly 530 nm after 8 hrs of incubation at 25°C, gradually showing a red shift with time at 25°C (Fig 4 curves bottom to top). The intense plasmon resonance band indicated the formation of spherical gold nanoparticles of approximately 40 nm in diameter [18]. Size distribution of GNPs was confirmed by coating a drop of the supernatant solution of disrupted cell suspension by TEM imaging. The images demonstrate gold nanoparticles possessing an average diameter of 40 nm (± 15%) as depicted in (Fig. 3b). Cryo TEM imaging of the thin sections of stained AuRed02 strain after reacting the biomass with gold chloride solution for 8 h showed the presence of gold nanoparticles on the inner cytoplasmic membrane (see Additional file 1, S1). It is likely that some gold ions (Au3+) cross the cell barrier through ion-transport channel and are reduced by the enzymes present on the cytoplasmic membrane and within the cytoplasm. Energy dispersive spectroscopy analysis (EDS) confirmed the presence of gold nanoparticles in the suspension. The spectra (Fig. 3c) present major Au peaks at approximately 2 keV besides several other peaks of C, O, and Si which might be due to the chemical composition of the sample substrate used in the EDS analysis. These results show that the strain Stenotrophomonas maltophilia could effectively synthesize GNPs of different sizes by resuspending the biomass for different time intervals in the presence of HAuCl4 (Fig. 4). The colored solution of GNPs remained stable for more than 2-weeks of storage at 4°C indicating the capping of GNPs with some charged groups. FTIR analysis of these GNPs further confirmed the capping of GNPs by phosphate groups (900 cm-1) (see Additional file 1, S2).

Bottom Line: Gold nanoparticles were characterized and found to be of ~40 nm size.Electrophoresis, Zeta potential and FTIR measurements confirmed that the particles are capped with negatively charged phosphate groups from NADP rendering them stable in aqueous medium.The process of synthesis of well-dispersed nanoparticles using a novel microorganism isolated from the gold enriched soil sample has been reported in this study, leading to the development of an easy bioprocess for synthesis of GNPs.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh 160036, India. raman@imtech.res.in.

ABSTRACT

Background: The synthesis of gold nanoparticles (GNPs) has received considerable attention with their potential applications in various life sciences related applications. Recently, there has been tremendous excitement in the study of nanoparticles synthesis by using some natural biological system, which has led to the development of various biomimetic approaches for the growth of advanced nanomaterials. In the present study, we have demonstrated the synthesis of gold nanoparticles by a novel bacterial strain isolated from a site near the famous gold mines in India. A promising mechanism for the biosynthesis of GNPs by this strain and their stabilization via charge capping was investigated.

Results: A bacterial isolate capable of gold nanoparticle synthesis was isolated and identified as a novel strain of Stenotrophomonas malophilia (AuRed02) based on its morphology and an analysis of its 16S rDNA gene sequence. After 8 hrs of incubation, monodisperse preparation of gold nanoparticles was obtained. Gold nanoparticles were characterized and found to be of ~40 nm size. Electrophoresis, Zeta potential and FTIR measurements confirmed that the particles are capped with negatively charged phosphate groups from NADP rendering them stable in aqueous medium.

Conclusion: The process of synthesis of well-dispersed nanoparticles using a novel microorganism isolated from the gold enriched soil sample has been reported in this study, leading to the development of an easy bioprocess for synthesis of GNPs. This is the first study in which an extensive characterization of the indigenous bacterium isolated from the actual gold enriched soil was conducted. Promising mechanism for the biosynthesis of GNPs by the strain and their stabilization via charge capping is suggested, which involves an NADPH-dependent reductase enzyme that reduces Au3+ to Au0 through electron shuttle enzymatic metal reduction process.

No MeSH data available.


Related in: MedlinePlus