Biosynthesis, characterization, and antimicrobial applications of silver nanoparticles

Figures & data

Figure 1 Chromatic properties of culture supernatant of Brevibacterium frigoritolerans DC2.

Notes: Culture supernatant of B. frigoritolerans DC2 after incubation with AgNO₃ (silver nitrate) (1 mM) (A) and control with medium and AgNO₃ (1 mM) after incubation period (B). UV-Vis spectra of culture supernatant of B. frigoritolerans DC2 treated with 1 mM AgNO₃ (C).

Abbreviations: OD, optical density; UV-Vis, ultraviolet-visible.

Figure 2 Properties of silver nanoparticles synthesized by Brevibacterium frigoritolerans DC2.

Notes: Transmission electron micrograph of silver nanoparticles synthesized by B. frigoritolerans DC2 (A and B). Particles size distribution of silver nanoparticles according to volume (C), number (D), and intensity (E).

Figure 3 Silver nanoparticles examined under a variety of conditions.

Notes: Energy dispersive X-ray spectroscopy of the whole scan area showing major peak of silver nanoparticles at 3 keV (A); X-ray diffraction patterns of silver nanoparticles obtained by Brevibacterium frigoritolerans DC2 (B); transmission electron micrograph of silver nanoparticle pellet solution (C); silver nanoparticles, green (D).

Table 1 Diameters of zones of inhibition (mm) for 50 μL of reaction mixture containing silver nanoparticles after incubation with various microorganisms

Number	Microorganism	Zone of inhibition (mm)
		Silver nitrate	Reaction mixture
1	Candida albicans KACC 30062	22±0.7	24±1.4
2	Vibrio parahaemolyticus ATCC 33844	23±1.1	25±1.0
3	Bacillus anthracis NCTC 10340	14±0.2	15±0.8
4	Bacillus cereus ATCC 14579	14±0.3	15±0.5
5	Salmonella enterica ATCC 13076	12±0.4	12±0.6
6	Escherichia coli ATCC 10798	10±0.7	11±0.2

Notes: Each value is the mean of the diameters of two wells. Each well contained 50 μL of tested samples.

Figure 4 Zones of inhibition for various pathogens.

Notes: Zones of inhibition of 50 μL of reaction mixture containing silver nanoparticles and 50 μL of 1mM AgNO₃ (silver nitrate) against the pathogenic strains Candida albicans (A), Vibrio parahaemolyticus (B), Bacillus anthracis (C), Bacillus cereus (D), Salmonella enterica (E), and Escherichia coli (F).

Abbreviation: AgNPs, silver nanoparticles.

Figure 5 Effects of partially purified silver nanoparticle pellet solution on various pathogens.

Notes: Zones of inhibition of partially purified silver nanoparticle pellet solution and silver nitrate (AgNO₃) (both at same concentration, 30 μL [100 mg/L]) against Salmonella enterica (A), Escherichia coli (B), Vibrio parahaemolyticus (C), Bacillus anthracis (D), and Bacillus cereus (E). Zones of inhibition of standard antibiotic discs against pathogenic bacteria Salmonella enterica (F), Escherichia coli (G), Vibrio parahaemolyticus (H), Bacillus anthracis (I), and Bacillus cereus (J). Zones of inhibition of standard antibiotic discs with silver nanoparticles against Salmonella enterica (K), Escherichia coli (L), Vibrio parahaemolyticus (M), Bacillus anthracis (N), and Bacillus cereus (O). Zones of inhibition of silver nanoparticles and silver nitrate against Candida albicans (P), cycloheximide (Q-7), Cycloheximide with AgNPs (Q-8,9). For (A–Q), the numbers, the corresponding antibiotics, and the corresponding concentrations of antibiotics are as follows: 1) lincomycin (MY15), 15 μg/disc; 2) oleandomycin (OL15), 15 μg/disc; 3) novobiocin (NV30), 30 μg/disc; 4) vancomycin (VA30), 30 μg/disc; 5) penicillin G (P10), 10 μg/disc; 6) rifampicin (RD5) 5 μg/disc; 7) cycloheximide, 10 μg/disc; 8) cycloheximide (10 μg/disc) with silver nanoparticles; and 9) cycloheximide (10 μg/disc) with silver nanoparticles.

Abbreviation: AgNPs, silver nanoparticles.

Figure 6 Graphical representation of comparative study between antibiotics and antibiotics with AgNPs.

Notes: Salmonella enterica (A), Escherichia coli (B), Vibrio parahaemolyticus (C), Bacillus anthracis (D), and Bacillus cereus (E), respectively. Results interpreting the antimicrobial activity of commercial antibiotics alone with that of antibiotics combined with silver nanoparticles.