Liquid crystals as optical amplifiers for bacterial detection

Interactions of bacteria with target molecules (e.g. antibiotics) or other microorganisms are of growing interest. The first barrier for targeting gram-negative bacteria is layer of a Lipopolysaccharides (LPS). Liquid crystal (LC) based sensors covered with LPS monolayers, as presented in this study, offer a simple model to study and make use of this type of interface for detection and screening. This work describes in detail the production and application of such sensors based on three different LPS that have been investigated regarding their potential to serve as sensing layer to detect bacteria. The LPS O127:B8 in combination with a LC based sensor was identified to be most useful as biomimetic sensing surface. This LPS/LC combination interacts with three different bacteria species, one gram-positive and two gram-negative species, allowing the detection of bacterial presence regardless from their viability. It could be shown that even very low bacterial cell numbers (minimum 500 cell ml(-1)) could be detected within minutes (maximum 15 min). The readout mechanism is the adsorption of bacterial entities on surface bond LPS molecules with the LC serving as an optical amplifier.