Sticky Situations: Bacterial Attachment Deciphered by Interferometry of Silicon Microstructures

Abstract

The peculiarities of surface-bound bacterial cells are often overshadowed by the study of planktonic cells in clinical microbiology. Thus, we employ phase-shift reflectometric interference spectroscopic measurements to observe the interactions between bacterial cells and abiotic, microstructured material surfaces in a label-free, real-time manner. Both material characteristics (i.e., substrate surface charge and wettability) and characteristics of the bacterial cells (i.e., motility, cell charge, biofilm formation, and physiology) drive bacteria to adhere to a particular surface. We conclude that the attachment of bacterial cells to a surface is determined by the culmination of numerous factors. When specific characteristics of the bacteria are met with factors of the surface, enhanced cell attachment and biofilm formation occur. Such knowledge can be exploited to predict antibiotic efficacy, biofilm development, enhance biosensor development, as well as prevent biofouling.

Antifungal susceptibility testing ofAspergillus nigeron silicon microwells by intensity-based reflectometric interference spectroscopy

“…1D-i and 1D-ii). Whereas in previous works [28][29][30][31][32][33] the values of 2nL were monitored over time, in this assay, the intensity of the reflected light is tracked, as A. niger tends to grow on top of the silicon microwells resulting in a decrease in peak intensity. The percent change in peak intensity of the fast Fourier spectrum, ΔI, of the reflected light over time is calculated as:…”

“…28 Previously, phase-shift reflectometric interference spectroscopic measurements (PRISM) was demonstrated to monitor antibiotic susceptibility and the behavior of bacteria within microstructured arrays. [29][30][31][32][33] Reflectance spectra of the arrays were collected over time in order to infer values of 2nL, in which n represents refractive index of the medium within the arrays and L represents the height of the microstructures. However, due to the different behavior and morphology of filamentous fungi compared to bacteria, herein we apply intensity-based PRISM, referred to as iPRISM, as a principle for the detection of microorganisms and as a tool for label-free, phenotypic antifungal susceptibility testing using fungal species A. niger as a model microorganism.…”