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Simple observation of Streptococcus mutans biofilm by scanning electron microscopy using ionic liquids.

Asahi Y, Miura J, Tsuda T, Kuwabata S, Tsunashima K, Noiri Y, Sakata T, Ebisu S, Hayashi M - AMB Express (2015)

Bottom Line: Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification.Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface.The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids.

View Article: PubMed Central - PubMed

Affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871 Japan.

ABSTRACT

Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification. However, conventional SEM requires dehydration and metal coating of biological samples before observation, and because biofilms consist mainly of water, sample dehydration may influence the biofilm structure. When coated with an ionic liquid, which is a kind of salt that exists in the liquid state at room temperature, biological samples for SEM observation do not require dehydration or metal coating because ionic liquids do not evaporate under vacuum conditions and are electrically conductive. This study investigates the ability of ionic liquids to allow SEM observation of Streptococcus mutans biofilms compared with conventional coating methods. Two hydrophilic and two hydrophobic ionic liquids, all of which are electronic conductors, are used. Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface. The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids. This study finds that ionic liquids are useful for allowing the observation of biofilms by SEM without preparation by dehydration and metal coating.

No MeSH data available.


Related in: MedlinePlus

SEM images of biofilms prepared for observation using hydrophilic and hydrophobic ILs. (a): SEM images of platinum-coated S. mutans biofilms. Fibrous extracellular matrix-like structures (star) were partially observed. In some areas of the biofilm surface, the cells were separated from the biofilm (arrow). Images of biofilms prepared for observation using hydrophilic ILs (b) [Ch][Lac] and (c) [C2mim][AcO], and hydrophobic ILs (d) [C4mim][Tf2N] and (e) [P4,4,4,12][BF4]. The concentration of all ILs was 10%. Some hydrophobic ILs were repelled by the biofilm surfaces and pooled on them. An asterisk indicates the accumulated IL. Arrowheads indicate the dark gaps thought to be water channels. Scale bars = 10 μm.
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Fig3: SEM images of biofilms prepared for observation using hydrophilic and hydrophobic ILs. (a): SEM images of platinum-coated S. mutans biofilms. Fibrous extracellular matrix-like structures (star) were partially observed. In some areas of the biofilm surface, the cells were separated from the biofilm (arrow). Images of biofilms prepared for observation using hydrophilic ILs (b) [Ch][Lac] and (c) [C2mim][AcO], and hydrophobic ILs (d) [C4mim][Tf2N] and (e) [P4,4,4,12][BF4]. The concentration of all ILs was 10%. Some hydrophobic ILs were repelled by the biofilm surfaces and pooled on them. An asterisk indicates the accumulated IL. Arrowheads indicate the dark gaps thought to be water channels. Scale bars = 10 μm.

Mentions: The SEM images of platinum-coated biofilms obtained in this study are similar to those of S. mutans biofilms reported by other researchers (Li et al. 2002; Pandit et al. 2011). The biofilms were composed of aggregated cocci, and fibriform extracellular matrix-like structures could be partially observed (Figure 3, Additional file 1: Figure S1). In some areas of the biofilm surface, the cells were almost separate from the biofilm (Figure 3a).Figure 3


Simple observation of Streptococcus mutans biofilm by scanning electron microscopy using ionic liquids.

Asahi Y, Miura J, Tsuda T, Kuwabata S, Tsunashima K, Noiri Y, Sakata T, Ebisu S, Hayashi M - AMB Express (2015)

SEM images of biofilms prepared for observation using hydrophilic and hydrophobic ILs. (a): SEM images of platinum-coated S. mutans biofilms. Fibrous extracellular matrix-like structures (star) were partially observed. In some areas of the biofilm surface, the cells were separated from the biofilm (arrow). Images of biofilms prepared for observation using hydrophilic ILs (b) [Ch][Lac] and (c) [C2mim][AcO], and hydrophobic ILs (d) [C4mim][Tf2N] and (e) [P4,4,4,12][BF4]. The concentration of all ILs was 10%. Some hydrophobic ILs were repelled by the biofilm surfaces and pooled on them. An asterisk indicates the accumulated IL. Arrowheads indicate the dark gaps thought to be water channels. Scale bars = 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4305086&req=5

Fig3: SEM images of biofilms prepared for observation using hydrophilic and hydrophobic ILs. (a): SEM images of platinum-coated S. mutans biofilms. Fibrous extracellular matrix-like structures (star) were partially observed. In some areas of the biofilm surface, the cells were separated from the biofilm (arrow). Images of biofilms prepared for observation using hydrophilic ILs (b) [Ch][Lac] and (c) [C2mim][AcO], and hydrophobic ILs (d) [C4mim][Tf2N] and (e) [P4,4,4,12][BF4]. The concentration of all ILs was 10%. Some hydrophobic ILs were repelled by the biofilm surfaces and pooled on them. An asterisk indicates the accumulated IL. Arrowheads indicate the dark gaps thought to be water channels. Scale bars = 10 μm.
Mentions: The SEM images of platinum-coated biofilms obtained in this study are similar to those of S. mutans biofilms reported by other researchers (Li et al. 2002; Pandit et al. 2011). The biofilms were composed of aggregated cocci, and fibriform extracellular matrix-like structures could be partially observed (Figure 3, Additional file 1: Figure S1). In some areas of the biofilm surface, the cells were almost separate from the biofilm (Figure 3a).Figure 3

Bottom Line: Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification.Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface.The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids.

View Article: PubMed Central - PubMed

Affiliation: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565-0871 Japan.

ABSTRACT

Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification. However, conventional SEM requires dehydration and metal coating of biological samples before observation, and because biofilms consist mainly of water, sample dehydration may influence the biofilm structure. When coated with an ionic liquid, which is a kind of salt that exists in the liquid state at room temperature, biological samples for SEM observation do not require dehydration or metal coating because ionic liquids do not evaporate under vacuum conditions and are electrically conductive. This study investigates the ability of ionic liquids to allow SEM observation of Streptococcus mutans biofilms compared with conventional coating methods. Two hydrophilic and two hydrophobic ionic liquids, all of which are electronic conductors, are used. Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface. The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids. This study finds that ionic liquids are useful for allowing the observation of biofilms by SEM without preparation by dehydration and metal coating.

No MeSH data available.


Related in: MedlinePlus