Biofilm Rupture by Laser-Induced Stress Waves Increases with Loading Amplitude, Independent of Location

Abstract

Integral to the production of safe and biocompatible medical devices is the determination of interfacial properties that affect or control strong biofilm adhesion. The laser spallation technique has recently emerged as an advantageous method to quantify biofilm adhesion across candidate biomedical surfaces. However, there is a possibility that membrane tension is a factor that contributes to the stress required to separate biofilm and substrate. In that case, the stress amplitude, controlled by laser fluence, that initiates biofilm rupture would vary systematically with location on the biofilm. Film rupture, also known as spallation, occurs when film material is ejected during stress wave loading. To determine effects of membrane tension on the laser spallation process, we present a protocol that measures spall size with increasing laser fluence (variable fluence) and with respect to distance from the biofilm centroid (iso-fluence). Streptococcus mutans biofilms on titanium substrates serve as our model system. A total of 185 biofilm loading locations are analyzed in this study. We demonstrate that biofilm spall size increases monotonically with laser fluence and apply our procedure to failure of nonbiological films. In iso-fluence experiments, no correlation is found between biofilm spall size and loading location, thus providing evidence that membrane tension does not play a dominant role in biofilm adhesion measurements. We recommend our procedure as a straightforward method to determine membrane effects in the measurement of adhesion of biological films on substrate surfaces via the laser spallation technique.

Periodically disturbing biofilms reduces expression of quorum sensing-regulated virulence factors in Pseudomonas aeruginosa

“…Previous work has demonstrated that the amplitude of a disturbance event can influence the distribution of bacteria. 21 , 30 , 31 Accordingly, we investigated the effects of altering the disturbance amplitude on the expression of quorum sensing-regulated virulence factors. We first determined the impact of disturbance amplitude and frequency on the distribution of bacteria in the biofilm and planktonic states.…”

Evolution of the Laser-Induced Spallation Technique in Film Adhesion Measurement

“…18( a ) . During the initial stages of these studies, two enabling works were conducted validating laser spallation as an appropriate technique [ 117 , 118 ]. The first study determined that there was no impact on adhesion strength based on loading regions within the biofilm from any internal film tension, Fig.…”

“…Copyright 2021 by Elsevier). ( b ) Image detecting software is used to measure distance of testing spot from center of biofilm and a graph illustrating this effect on percentage of region spalled (Adapted with permission from Kearns et al [ 117 ]. Copyright 2020 by American Chemical Society).…”