Controlled Synthesis of Triangular Silver Nanoplates by Gelatin–Chitosan Mixture and the Influence of Their Shape on Antibacterial Activity

Abstract

Triangular silver nanoplates were prepared by using the seeding growth approach with the presence of citrate-stabilized silver seeds and a mixture of gelatin-chitosan as the protecting agent. By understanding the critical role of reaction components, the synthesis process was improved to prepare the triangular nanoplates with high yield and efficiency. Different morphologies of silver nanostructures, such as triangular nanoplates, hexagonal nanoprisms, or nanodisks, can be obtained by changing experimental parameters, including precursor AgNO 3 volume, gelatin-chitosan concentration ratios, and the pH conditions. The edge lengths of triangular silver nanoplates were successfully controlled, primarily through the addition of silver nitrate under appropriate condition. As-prepared triangular silver nanoplates were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-Vis, Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Silver nanoplates had an average edge length of 65-80 nm depending on experimental conditions and exhibited a surface plasma resonance absorbance peak at 340, 450, and 700 nm. The specific interactions of gelatin and chitosan with triangular AgNPs were demonstrated by FT-IR. Based on the characterization, the growth mechanism of triangular silver nanoplates was theoretically proposed regarding the twinned crystal of the initial nanoparticle seeds and the crystal face-blocking role of the gelatin-chitosan mixture. Moreover, the antibacterial activity of triangular silver nanoplates was considerably improved in comparison with that of spherical shape when tested against Gram-positive and Gram-negative bacteria species, with 6.0 ug/mL of triangular silver nanoplates as the MBC (Minimum bactericidal concentration) for Escherichia coli and Vibrio cholera, and 8.0 ug/mL as the MBC for Staphylococcus aureus and Pseudomonas aeruginosa. The MIC (Minimum inhibitory concentration) of triangular Ag nanoplates was 4.0 ug/mL for E. coli, V. cholera, S. aureus, and P. aeruginosa.

Ag Nanoparticles for Biomedical Applications—Synthesis and Characterization—A Review

“…Being able to penetrate the bacteria membrane with three edges, Pal et al [ 36 ] suggested, through TEM images, that truncated triangular nanoplates were the most aggressive, leading to the highest capacity to kill bacteria [ 36 ]. This theory was also analyzed by Vo et al in 2019 [ 37 ]; by comparing the spherical and the triangular shape of Ag NPs, a higher bactericidal effect was associated with the triangular shape. Previous studies attributed this result to the crystallographic structure of Ag; the (111) facet found in a higher quantity in triangular shape can interact easier with bacteria membrane and can produce necrosis faster [ 36 , 37 , 38 ].…”

“…This theory was also analyzed by Vo et al in 2019 [ 37 ]; by comparing the spherical and the triangular shape of Ag NPs, a higher bactericidal effect was associated with the triangular shape. Previous studies attributed this result to the crystallographic structure of Ag; the (111) facet found in a higher quantity in triangular shape can interact easier with bacteria membrane and can produce necrosis faster [ 36 , 37 , 38 ]. Even if in the case of bacteria species, sharp nanoparticles exhibit stronger bactericidal effects, for a faster regeneration of the lesions and for a proper distribution in the body fluids, spherical nanoparticles are also preferred in most applications, being the most studied nanoparticles.…”

Antimicrobial Active Bioplastics Using Triangular Silver Nanoplate Integrated Polycaprolactone and Polylactic Acid Films

“…TSNPs have been reported to exhibit higher antimicrobial activity, attributed to a rate of Ag + ion release five times larger, compared to spherical NPs. As Ag + ion release is caused by oxidation, the increased ion release of TSNPs is a consequence of their sharp edges and corners, which make them more susceptible to oxidation [ 13 , 14 , 15 , 16 , 17 ]. It is also recognised that larger surface-to-volume ratio possessed by smaller NPs compared to larger ones allows smaller particles to release more Ag + ions.…”

Bioactive Surfaces of Polylactide and Silver Nanoparticles for the Prevention of Microbial Contamination

“…According to the available specialized data (PDF no. 00-004-0783), these peaks correspond to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) diffraction planes of silver crystals with face-centered cubic (fcc) lattice[52,53]. By indicating the high purity and crystalline nature of silver-based sample and by showing its characteristic fcc crystallographic lattice, the XRD pattern confirms that metallic silver represents the sole crystalline phase of the obtained powder.…”