Antimicrobial characterization of silver nanoparticle-coated surfaces by “touch test” method

Figures & data

Figure 1 Schematic picture of “touch test” method.

Figure 2 Comparison of antimicrobial properties of direct and indirect LFS silver nanoparticle deposition on glass surfaces against E. coli and S. aureus.

Notes: Bacterial growth scale: 3 – good growth; 2 – moderate growth; 1 – poor growth; 0 – no growth. Reference means glass samples without LFS nanoparticle coatings.
Abbreviations: E. coli, Escherichia coli; LFS, liquid flame spray; S. aureus, Staphylococcus aureus.

Figure 3 Threshold screening for LFS silver nanoparticle-coating cycles against E. coli (A) and S. aureus (B) in cover glass samples.

Notes: Bacterial growth scale: 3 = good growth; 2 = moderate growth; 1 = poor growth; 0, no growth. Reference means glass samples without LFS nanoparticle coatings.
Abbreviations: E. coli, Escherichia coli; LFS, liquid flame spray; S. aureus, Staphylococcus aureus; room temperature.

Figure 4 Antibacterial effect of silver nanoparticle-coated PE samples against E. coli (A) and S. aureus (B) and PET samples against E. coli (C) and S. aureus (D).

Note: Bacterial growth scale: 3 – good growth; 2 – moderate growth; 1 – poor growth; 0 – no growth.
Abbreviations: E. coli, Escherichia coli; LFS, liquid flame spray; PE, polyethylene; PET, PE terephthalate; S. aureus, Staphylococcus aureus; RT, room temperature.

Table 1 Comparison of antimicrobial properties of direct and indirect LFS silver nanoparticle deposition against seven clinically relevant bacteria

LFS	Incubation time	S. aureus (MetR), mean (SD)	E. faecalis, mean (SD)	E. faecium, mean (SD)	P. aeruginosa, mean (SD)	Acinetobacter sp., mean (SD)	S. pyogenes, mean (SD)	S. pneumoniae, mean (SD)
Direct	6 h, RT	0.7 (±0.58)	0.5 (±0.71)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	nd	nd
	24 h, RT	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	nd	nd
	6 h, 37°C	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)
	24 h, 37°C	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)
Indirect	6 h, RT	3.0 (±0.0)	2.7 (±0.58)	2.3 (±1.15)	2.0 (±1.73)	1.0 (±1.73)	nd	nd
	24 h, RT	2.0 (±1.0)	2.3 (±0.58)	2.3 (±0.58)	0.0 (±0.0)	0.0 (±0.0)	nd	nd
	6 h, 37°C	0.7 (±1.15)	2.3 (±0.5)	2.0 (±0.0)	0.5 (±0.58)	0.0 (±0.0)	0.0 (±0.0)	0.5 (±0.58)
	24 h, 37°C	0.7 (±0.58)	2.0 (±0.0)	2.6 (±0.48)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)	0.0 (±0.0)
Reference glass	6 h, RT	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	nd	nd
	24 h, RT	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	2.0 (±1.0)	nd	nd
	6 h, 37°C	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	1.3 (±1.53)	0.3 (±0.5)	1.5 (±1.29)
	24 h, 37°C	3.0 (±0.0)	3.0 (±0.0)	3.0 (±0.0)	2.5 (±0.58)	1.3 (±1.53)	0.3 (±0.5)	0.0 (±0.0)

Abbreviations: E. faecalis, Enterococcus faecalis; E. faecium, Enterococcus faecium; LFS, liquid flame spray; P. aeruginosa, Pseudomonas aeruginosa; PET, polyethylene terephthalate; RT, room temperature; S. aureus, Staphylococcus aureus; SEM, scanning electron microscopy; S. pneumoniae, Streptococcus pneumoniae; S. pyogenes, Streptococcus pyogenes; MetR, methicillin resistant; nd, not determined.

Figure 5 SEM image showing silver nanoparticles on the glass surface with direct 30× (A) and indirect 30 s (B) deposition, and direct 30× deposition on PET surface (C).

Abbreviations: PET, polyethylene terephthalate; SEM, scanning electron microscopy; SEI, secondary electron imaging; WD, working distance; EHT, electron high tension.