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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.


Related in: MedlinePlus

Relative fluorescence intensity (with respect to H2O2) showing the cellular ROS formation capability of protein-capped and bare silver nanoparticles as compare to control.Vertical bars represent standard errors. Significant differences from control (p ≤ 0.05) are marked with asterisk.
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pone.0134337.g007: Relative fluorescence intensity (with respect to H2O2) showing the cellular ROS formation capability of protein-capped and bare silver nanoparticles as compare to control.Vertical bars represent standard errors. Significant differences from control (p ≤ 0.05) are marked with asterisk.

Mentions: The exact mechanism of bactericidal effect of silver nanoparticles has yet not been elucidated and is open for debate [7,46]. The most commonly reported mechanism is the generation of free radicals such as peroxide, superoxide and hydroxyl ions by silver nanoparticles which could play a key role in executing bactericidal effects [47]. Fig 7 depicts the magnitude of ROS species formation represented as fluorescent counts due to DCF formation in bacterial cells exposed to the protein-capped and bare silver nanoparticles as compared to the control. The magnitude of ROS species generation was approximately two fold higher for bare silver nanoparticles as compared to the protein-capped nanoparticles in case of Gram positive bacterial species. The low ROS production observed in case of protein-capped silver nanoparticles may be attributed to the presence of biocompatible molecules in the shell. In contrast, absence of these biocompatible molecules on bare silver nanoparticles led to accelerated ROS production. Surprisingly, almost similar magnitude of ROS species generation was observed for both protein-capped and bare silver nanoparticles in Gram negative bacterial species.


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)

Relative fluorescence intensity (with respect to H2O2) showing the cellular ROS formation capability of protein-capped and bare silver nanoparticles as compare to control.Vertical bars represent standard errors. Significant differences from control (p ≤ 0.05) are marked with asterisk.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0134337.g007: Relative fluorescence intensity (with respect to H2O2) showing the cellular ROS formation capability of protein-capped and bare silver nanoparticles as compare to control.Vertical bars represent standard errors. Significant differences from control (p ≤ 0.05) are marked with asterisk.
Mentions: The exact mechanism of bactericidal effect of silver nanoparticles has yet not been elucidated and is open for debate [7,46]. The most commonly reported mechanism is the generation of free radicals such as peroxide, superoxide and hydroxyl ions by silver nanoparticles which could play a key role in executing bactericidal effects [47]. Fig 7 depicts the magnitude of ROS species formation represented as fluorescent counts due to DCF formation in bacterial cells exposed to the protein-capped and bare silver nanoparticles as compared to the control. The magnitude of ROS species generation was approximately two fold higher for bare silver nanoparticles as compared to the protein-capped nanoparticles in case of Gram positive bacterial species. The low ROS production observed in case of protein-capped silver nanoparticles may be attributed to the presence of biocompatible molecules in the shell. In contrast, absence of these biocompatible molecules on bare silver nanoparticles led to accelerated ROS production. Surprisingly, almost similar magnitude of ROS species generation was observed for both protein-capped and bare silver nanoparticles in Gram negative bacterial species.

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