Revealing region-specific biofilm viscoelastic properties by means of a micro-rheological approach.

Yihong Dai,Huayu Cao,Eoin Casey,Rory Heffernan,Olivier Habimana,Ashkan Safari

doi:10.1038/s41522-016-0005-y

Yihong Dai, Huayu Cao

Open Access

https://doi.org/10.1038/s41522-016-0005-y

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Abstract

Particle-tracking microrheology is an in situ technique that allows quantification of biofilm material properties. It overcomes the limitations of alternative techniques such as bulk rheology or force spectroscopy by providing data on region specific material properties at any required biofilm location and can be combined with confocal microscopy and associated structural analysis. This article describes single particle tracking microrheology combined with confocal laser scanning microscopy to resolve the biofilm structure in 3 dimensions and calculate the creep compliances locally. Samples were analysed from Pseudomonas fluorescens biofilms that were cultivated over two timescales (24 h and 48 h) and alternate ionic conditions (with and without calcium chloride supplementation). The region-based creep compliance analysis showed that the creep compliance of biofilm void zones is the primary contributor to biofilm mechanical properties, contributing to the overall viscoelastic character.

Highlights

The characterisation of biofilms in terms of their material properties is important for the fundamental understanding of methods for the control of unwanted biofilms.[1, 2] comprehensive quantification of the mechanical properties of biofilm remains a major challenge, in part due to the temporal, spatial and compositional dynamics of the extracellular matrix,[3] and due to the lack of available techniques for routine laboratory measurements
Comprehensive quantification of the mechanical properties of biofilm remains a major challenge, in part due to the temporal, spatial and compositional dynamics of the extracellular matrix,[3] and due to the lack of available techniques for routine laboratory measurements. Some methods, such as atomic force microscopy (AFM)[4] or the parallel plate rheometer[5] have been successfully applied for investigation of the structural and physical properties, they are limited in their ability to describe properties at acceptable resolution
This paper describes single particle tracking microrheology combined with confocal laser scanning microscopy to resolve the biofilm structure in three dimensions and calculate the creep compliances locally

Summary

Introduction

The characterisation of biofilms in terms of their material properties is important for the fundamental understanding of methods for the control of unwanted biofilms.[1, 2] comprehensive quantification of the mechanical properties of biofilm remains a major challenge, in part due to the temporal, spatial and compositional dynamics of the extracellular matrix,[3] and due to the lack of available techniques for routine laboratory measurements Some methods, such as atomic force microscopy (AFM)[4] or the parallel plate rheometer[5] have been successfully applied for investigation of the structural and physical properties, they are limited in their ability to describe properties at acceptable resolution. It was found that the creep compliance become higher with increasing height from the bottom of biofilm.[8]

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