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Removal of Protein Capping Enhances the Antibacterial Efficiency of Biosynthesized Silver Nanoparticles.

Jain N, Bhargava A, Rathi M, Dilip RV, Panwar J - PLoS ONE (2015)

Bottom Line: The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell.The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species.In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biotechnology, Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, 333 031, India.

ABSTRACT
The present study demonstrates an economical and environmental affable approach for the synthesis of "protein-capped" silver nanoparticles in aqueous solvent system. A variety of standard techniques viz. UV-visible spectroscopy, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) measurements were employed to characterize the shape, size and composition of nanoparticles. The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell. In order to prepare bare silver nanoparticles, the protein shell was removed from biogenic nanoparticles as confirmed by UV-visible spectroscopy, FTIR and photoluminescence analysis. Subsequently, the antibacterial efficacy of protein-capped and bare silver nanoparticles was compared by bacterial growth rate and minimum inhibitory concentration assay. The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species. Mechanistic studies based on ROS generation and membrane damage suggested that protein-capped and bare silver nanoparticles demonstrate distinct mode of action. These findings were strengthened by the TEM imaging along with silver ion release measurements using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects. These findings open new avenues for surface modifications of nanoparticles to modulate and enhance their functional properties.

No MeSH data available.


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ICP-AES analysis of silver dissolution profiles of protein-capped and bare silver nanoparticles.
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pone.0134337.g011: ICP-AES analysis of silver dissolution profiles of protein-capped and bare silver nanoparticles.

Mentions: The release of silver ions from silver nanoparticles determines their antibacterial activity [46,47,56–58]. It has been demonstrated that aerobic conditions can readily oxidized silver nanoparticles in aqueous solutions resulting in the release of silver ions [59]. The positive charge generated due to release of Ag+ ions from silver nanoparticles develops an electrostatic interaction with the negatively charged bacterial cell membrane [60]. Moreover, the reaction of silver ions with carbohydrates, hydroxyls and thiols of bacterial cell wall and nuclear membrane leads to cell distortion and death [12,61]. In the present study, the release of silver ions from protein-capped and bare silver nanoparticles was estimated using ICP-AES. The dissolved silver ion concentration for protein-capped and bare silver nanoparticles was measured as 15.8 and 27.5 μg L-1, respectively (Fig 11). It clearly indicates that the presence of protein shell acts as a barrier preventing the release of silver ions from the nanoparticles. These results are in complete accordance with a previous study which demonstrated that surface coating play a key role in dissolution of silver ions from nanoparticle surface and the toxicity of silver nanoparticles depends on the surface coating [62].


Removal of Protein Capping Enhances the Antibacterial Efficiency of Biosynthesized Silver Nanoparticles.

Jain N, Bhargava A, Rathi M, Dilip RV, Panwar J - PLoS ONE (2015)

ICP-AES analysis of silver dissolution profiles of protein-capped and bare silver nanoparticles.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520467&req=5

pone.0134337.g011: ICP-AES analysis of silver dissolution profiles of protein-capped and bare silver nanoparticles.
Mentions: The release of silver ions from silver nanoparticles determines their antibacterial activity [46,47,56–58]. It has been demonstrated that aerobic conditions can readily oxidized silver nanoparticles in aqueous solutions resulting in the release of silver ions [59]. The positive charge generated due to release of Ag+ ions from silver nanoparticles develops an electrostatic interaction with the negatively charged bacterial cell membrane [60]. Moreover, the reaction of silver ions with carbohydrates, hydroxyls and thiols of bacterial cell wall and nuclear membrane leads to cell distortion and death [12,61]. In the present study, the release of silver ions from protein-capped and bare silver nanoparticles was estimated using ICP-AES. The dissolved silver ion concentration for protein-capped and bare silver nanoparticles was measured as 15.8 and 27.5 μg L-1, respectively (Fig 11). It clearly indicates that the presence of protein shell acts as a barrier preventing the release of silver ions from the nanoparticles. These results are in complete accordance with a previous study which demonstrated that surface coating play a key role in dissolution of silver ions from nanoparticle surface and the toxicity of silver nanoparticles depends on the surface coating [62].

Bottom Line: The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell.The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species.In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects.

View Article: PubMed Central - PubMed

Affiliation: Centre for Biotechnology, Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, 333 031, India.

ABSTRACT
The present study demonstrates an economical and environmental affable approach for the synthesis of "protein-capped" silver nanoparticles in aqueous solvent system. A variety of standard techniques viz. UV-visible spectroscopy, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) measurements were employed to characterize the shape, size and composition of nanoparticles. The synthesized nanoparticles were found to be homogenous, spherical, mono-dispersed and covered with multi-layered protein shell. In order to prepare bare silver nanoparticles, the protein shell was removed from biogenic nanoparticles as confirmed by UV-visible spectroscopy, FTIR and photoluminescence analysis. Subsequently, the antibacterial efficacy of protein-capped and bare silver nanoparticles was compared by bacterial growth rate and minimum inhibitory concentration assay. The results revealed that bare nanoparticles were more effective as compared to the protein-capped silver nanoparticles with varying antibacterial potential against the tested Gram positive and negative bacterial species. Mechanistic studies based on ROS generation and membrane damage suggested that protein-capped and bare silver nanoparticles demonstrate distinct mode of action. These findings were strengthened by the TEM imaging along with silver ion release measurements using inductively coupled plasma atomic emission spectroscopy (ICP-AES). In conclusion, our results illustrate that presence of protein shell on silver nanoparticles can decrease their bactericidal effects. These findings open new avenues for surface modifications of nanoparticles to modulate and enhance their functional properties.

No MeSH data available.


Related in: MedlinePlus