Nanoplasmonics for Real-Time and Label-Free Monitoring of Microbial Biofilm Formation

Abstract

Microbial biofilms possess intrinsic resistance against conventional antibiotics and cleaning procedures; thus, a better understanding of their complex biological structures is crucial in both medical and industrial applications. Existing laboratory methodologies have focused on macroscopic and mostly indirect characterization of mechanical and microbiological properties of biofilms adhered on a given substrate. However, the kinetics underlying the biofilm formation is not well understood, while such information is critical to understanding how drugs and chemicals influence the biofilm formation. Herein, we report the use of localized surface plasmon resonance (LSPR) for real-time, label-free monitoring of E. coli biofilm assembly on a nanoplasmonic substrate consisting of gold mushroom-like structures. Our LSPR sensor is able to capture the signatures of biofilm formation in real-time by measuring the wavelength shift in the LSPR resonance peak with high temporal resolution. We employ this sensor feature to elucidate how biofilm formation is affected by different drugs, including conventional antibiotics (kanamycin and ampicillin) as well as rifapentine, a molecule preventing cell adhesion yet barely affecting bacterial viability and vitality. Due to its flexibility and simplicity, our LSPR based platform can be used on a wide variety of clinically relevant bacteria, thus representing a valuable tool in biofilm characterization and drug screening.

Mimicking biofilm formation and development: Recent progress in in vitro and in vivo biofilm models

“…An interesting optical microsystem for studying biofilm formation in vitro was developed by Funari et al (2018). The authors fabricated what they called a ''nanomushroom-based localized surface plasmon resonance (LSPR) substrate'' for the real-time monitoring of biofilm formation and drug screening.…”

Nanophotonics for bacterial detection and antimicrobial susceptibility testing

“…This further decrease is enabled by increasing the sensitivity to bacterial growth because only the first layer of adherent bacteria is probed by the evanescent tail [23,122], therefore affording to probe growth from a much earlier stage. Such configuration lends itself to the study of real-time biofilm growth [125,128], where the bottom layer is crucial, and represents an attractive alternative to traditional cumbersome microscopy or staining protocols [129].…”

“…On resonance, the electric field at the surface of the nanoparticle is strongly enhanced and decays with a short distance (tens of nanometre), thereby enabling evanescent-wave optical sensing [123,124]. Funari et al [125] fabricated gold nanoparticles supported by silica pillars, as shown in the sketch in Figure 7(d) and imaged in Figure 7(e). These structures, dubbed gold nanomushrooms, support a broad (Q ≲ 10) LSPR mode which was used to monitor an E. coli biofilm forming over the surface in the presence of different antibiotics.…”

Biological Effects of C60 Fullerene Revealed with Bacterial Biosensor—Toxic or Rather Antioxidant?

“…In the present paper, a simple yet efficient bacterial model based on Escherichia coli is utilized. Recently, it was used to develop a biosensor for detection of catechol [19] and to detect biofilm formation using localized surface plasmon resonance in real-time [20]. Here, we decided to apply an E. coli biosensor based on the MG1655 pKatG-lux strain, which is specific to one of the main reactive oxygen species—hydrogen peroxide (H 2 O 2 ).…”