Acquisition of time-frequency localized mechanical properties of biofilms and single cells with high spatial resolution

TL;DR

This paper introduces a high-resolution AFM-based method combined with viscoelastic analysis to map the localized mechanical properties of biofilms and single cells across time and frequency, revealing insights into biofilm stability and dispersal.

Contribution

The study develops a novel technique integrating AFM and viscoelastic analysis for detailed, localized mechanical characterization of biofilms at the single-cell level.

Findings

Provides nanorheological signatures of biofilms

Maps mechanical heterogeneity within biofilms

Offers computational routines for data analysis

Abstract

Biofilms are a cluster of bacteria embedded in extracellular polymeric substances (EPS) that contain a complex composition of polysaccharides, proteins, and extracellular DNA (eDNA). Desirable mechanical properties of the biofilms are critical for their survival, propagation, and dispersal, and the response of mechanical properties to different treatment conditions also sheds light on biofilm control and eradication in vivo and on engineering surfaces. However, it is challenging yet important to interrogate mechanical behaviors of biofilms with a high spatial resolution because biofilms are very heterogeneous. Moreover, biofilms are viscoelastic, and their time-dependent mechanical behavior is difficult to capture. Herein, we developed a powerful technique that combines the high spatial resolution of the atomic force microscope (AFM) with a rigorous history-dependent viscoelastic analysis to deliver highly spatial-localized biofilm properties within a wide time-frequency window. By exploiting the use of static force spectroscopy in combination with an appropriate viscoelastic framework, we highlight the intensive amount of time-dependent information experimentally available that has been largely overlooked. It is shown that this technique provides a detailed nanorheological signature of the biofilms even at the single-cell level. We share the computational routines that would allow any user to perform the analysis from experimental raw data. The detailed localization of mechanical properties in space and in time-frequency domain provides insights on the understanding of biofilm stability, cohesiveness, dispersal, and control.