Study on the Effect of Contrast Agent on Biofilms and Their Visualization in Porous Substrate Using X-ray μCT

Abstract

Investigation of biofilms and visualization using non-destructive imaging techniques like X-ray μCT has recently gained interest. Biofilms are congregations of microorganisms that attach to surfaces and comprise of microbial cells embedded in extracellular polymeric substances (EPS). They are ubiquitous entities that are commonly found in any non-sterile setting and have direct implications on human health. Methods to visualize them in situ are highly needed to understand their behaviour (attachment and detachment) inside a substrate. Contrast-enhanced X-ray μCT is a 3D imaging technique that is capable of visualising objects that have very low attenuation contrast. The use of contrast agents in X-ray μCT has been an evolving process, however, the possible toxic effect of these chemical compounds against biofilms has not been studied in detail. In this study, we focus on the toxic effect of contrast agents and study the diffusion and drainage of contrast agents in biofilms. We propose using water-soluble potassium bromide (KBr) as a suitable contrast agent for enhancement of the attenuation coefficient of a monoculture of Pseudomonas fluorescens biofilms inside a porous substrate. At the given concentration, KBr proved to be less bactericidal compared to other commonly used contrast agents and at 5% w/v concentration we were able to clearly distinguish between the biofilm and the porous substrate.

Insights into the Development of Phototrophic Biofilms in a Bioreactor by a Combination of X-ray Microtomography and Optical Coherence Tomography

“…This was considered by a correction factor of −2.1% for the biomass volume in µCT results. Due to expected long-term damage to the cells by the contrast agent, biomass cannot be used further [33]. Using a contrast agent can also lead to artifacts which could appear in the form of band-like, linear shaped areas or pixels that were too bright.…”

“…Often µCT scans are used to obtain a 3D model for a simulation (e.g., CFD) or for 3D printing [32]. Due to poor contrast differences in µCT analysis between biofilm and biocarrier [33], often a contrast agent is needed. Until now, a broad variety of contrast agents have been studied, but no universal contrast agent has been found [34].…”