Using surface plasmon resonance imaging to study bacterial biofilms

Abstract

This paper describes the use of Surface Plasmon Resonance imaging (SPRi) as an emerging technique to study bacterial physiology in real-time without labels. The overwhelming majority of bacteria on earth exist in large multicellular communities known as biofilms. Biofilms are especially problematic because they facilitate the survival of pathogens, leading to chronic and recurring infections as well as costly industrial complications. Monitoring biofilm accumulation and removal is therefore critical in these and other applications. SPRi uniquely provides label-free, high-resolution images of biomass coverage on large channel surfaces up to 1 cm 2 in real time, which allow quantitative assessment of biofilm dynamics. The rapid imaging capabilities of this technique are particularly relevant for multicellular bacterial studies, as these cells can swim several body lengths per second and divide multiple times per hour. We present here the first application of SPRi to image Escherichia coli and Pseudomonas aeruginosa cells moving, attaching, and forming biofilms across a large surface. This is also the first time that biofilm removal has been visualized with SPRi, which has important implications for monitoring the biofouling and regeneration of fluidic systems. Initial images of the removal process show that the biofilm releases from the surface as a wave along the direction of the fluid flow. V C 2014 AIP Publishing LLC. [http://dx

Improving the Molecular Ion Signal Intensity for In Situ Liquid SIMS Analysis

“…At biointerfaces, for instance, the distribution of small functional ions such as , or small organic molecules such as glucose and phospholipid molecules remains unclear. This is despite the use of many in situ techniques such as atomic force microscopy [1,2], fluorescence [3,4], Raman [5], infrared [6,7], and surface plasmon resonance [8].…”

Surface Plasmon Resonance: a Label-Free Tool for Cellular Analysis

“…In one chamber, GFP-E. coli was added along with LB (lysogeny broth) growth media and in the second one only LB was added as a control. The appearance of bright spots in the SPRi difference images ( Figure 7B) of the bacterial chamber is due to biomass accumulation on the surface, which signifies Reproduced with permission from [28]. Figure 7C & E), and this is due to the evaporation of growth media from the chamber.…”

“…Finally, the SPRi images of both control and sample chambers were correlated with fluorescent images (Figure 7G, H) and as expected fluorescent cells were visualized in the bacterial chamber only. This study revealed both kinetic information about bacterial adherence and growth and spatial information about the biofilm formation [28].…”

“…In one particular study, lipopolysaccharides (an endotoxin), sodium azide (a chemical toxin) and thrombin (a physiological agonist) were tested on human embryonic kidney-293 to assess cell viability [58]. Lipopolysaccharides are well known to cause cell death by triggering an inflammatory response [59], sodium azide is known to inhibit Reproduced with permission from [28]. Surface plasmon resonance: a label-free tool for cellular analysis Review cellular respiration [60] and thrombin is documented to cause contraction in the cells as it affects the cell integrity [61].…”

“…The requirement to assess pathogens in food, medicine and environment has instigated the development of SPR cell-based biosensors that can provide mechanistic and kinetic insight [27][28][29][30][31][32][33]. For example, Watts et al were one of the first groups to apply the SPR platform for the detection of whole living cells.…”