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Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study

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ABSTRACT

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.

No MeSH data available.


a UV–vis spectra of gelatin-AuNPs and gelatin-AuNPs degraded by 2 M chlorhydric acid (Cgelatin: 0.4 wt%). The inset in a is the digital image of Curve 1 (left) and 2 (right) colloids; b TEM image of incompletely degraded gelatin-AuNPs colloid.
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Figure 6: a UV–vis spectra of gelatin-AuNPs and gelatin-AuNPs degraded by 2 M chlorhydric acid (Cgelatin: 0.4 wt%). The inset in a is the digital image of Curve 1 (left) and 2 (right) colloids; b TEM image of incompletely degraded gelatin-AuNPs colloid.

Mentions: Gelatin is prone to degradation on incubation at elevated temperature in the absence of proteases. The incubation parameters such as temperature, time, pH, and salt ions have great effect on gelatin degradation [29]. Therefore, the gelatin degradation has been partly carried out in the process of gold nanoparticle growth at higher temperature. To obtain the information on AuNPs stabilized by gelatin, the gelatin backbone was removed by hydrolyzing gelatin-AuNPs in 2 M HCl. Figure 6a showed that the plasmon resonance band of AuNPs at 529 nm has disappeared. But the size and shape of AuNPs stabilized by gelatin residues (marked by pane 2 in Figure 6b) has no obvious difference with AuNPs stabilized by gelatin as well as incompletely degraded gelatin by comparing with Figures 1 and 6b. The plasmon resonance band of AuNPs depends on the morphology of nanoparticles and the dielectric properties of the surrounding medium [30]. Exploring the reason of this alteration on the plasmon resonance of AuNPs, we studied the stability of AuNPs against pH and salt (NaCl) at room temperature (see Figure 7). There, besides the decrease in plasmon resonance peak intensity of AuNPs induced by diluting the gelatin-AuNPs colloid with NaOH, HCl or NaCl solution, Figure 7 showed that the plasmon resonance peak of AuNPs remained stable by altering pH and NaCl concentration of the gelatin-AuNPs colloid, even at lower pH and higher NaCl concentration. When the three-dimensional α-helix folding structure of gelatin was destroyed by the degradation of gelatin with the acid, gelatin polypeptides changed into gelatin residues. Therefore, Curve 1 in Figure 6a showed the plasmon resonance band of AuNPs aggregates (including many separated AuNPs) stabilized by gelatin three-dimensional α-helix folding chains and Curve 2 showed the plasmon resonance band of separated AuNPs stabilized by gelatin three-dimensional α-helix folding chains. Furthermore, the gelatin solution degraded slowly and is suitable for fungal growth at room temperature. The gelatin template has changed into fungal templates for gold nanoparticles (see Figure 8) (the fungal species is very complicated because it originated from fungoid in air) [31].


Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study
a UV–vis spectra of gelatin-AuNPs and gelatin-AuNPs degraded by 2 M chlorhydric acid (Cgelatin: 0.4 wt%). The inset in a is the digital image of Curve 1 (left) and 2 (right) colloids; b TEM image of incompletely degraded gelatin-AuNPs colloid.
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Related In: Results  -  Collection

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Figure 6: a UV–vis spectra of gelatin-AuNPs and gelatin-AuNPs degraded by 2 M chlorhydric acid (Cgelatin: 0.4 wt%). The inset in a is the digital image of Curve 1 (left) and 2 (right) colloids; b TEM image of incompletely degraded gelatin-AuNPs colloid.
Mentions: Gelatin is prone to degradation on incubation at elevated temperature in the absence of proteases. The incubation parameters such as temperature, time, pH, and salt ions have great effect on gelatin degradation [29]. Therefore, the gelatin degradation has been partly carried out in the process of gold nanoparticle growth at higher temperature. To obtain the information on AuNPs stabilized by gelatin, the gelatin backbone was removed by hydrolyzing gelatin-AuNPs in 2 M HCl. Figure 6a showed that the plasmon resonance band of AuNPs at 529 nm has disappeared. But the size and shape of AuNPs stabilized by gelatin residues (marked by pane 2 in Figure 6b) has no obvious difference with AuNPs stabilized by gelatin as well as incompletely degraded gelatin by comparing with Figures 1 and 6b. The plasmon resonance band of AuNPs depends on the morphology of nanoparticles and the dielectric properties of the surrounding medium [30]. Exploring the reason of this alteration on the plasmon resonance of AuNPs, we studied the stability of AuNPs against pH and salt (NaCl) at room temperature (see Figure 7). There, besides the decrease in plasmon resonance peak intensity of AuNPs induced by diluting the gelatin-AuNPs colloid with NaOH, HCl or NaCl solution, Figure 7 showed that the plasmon resonance peak of AuNPs remained stable by altering pH and NaCl concentration of the gelatin-AuNPs colloid, even at lower pH and higher NaCl concentration. When the three-dimensional α-helix folding structure of gelatin was destroyed by the degradation of gelatin with the acid, gelatin polypeptides changed into gelatin residues. Therefore, Curve 1 in Figure 6a showed the plasmon resonance band of AuNPs aggregates (including many separated AuNPs) stabilized by gelatin three-dimensional α-helix folding chains and Curve 2 showed the plasmon resonance band of separated AuNPs stabilized by gelatin three-dimensional α-helix folding chains. Furthermore, the gelatin solution degraded slowly and is suitable for fungal growth at room temperature. The gelatin template has changed into fungal templates for gold nanoparticles (see Figure 8) (the fungal species is very complicated because it originated from fungoid in air) [31].

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.

No MeSH data available.