Electrochemistry of redox liposome nano-impacts for bacterial toxins sensing – ELIPOX

ELIPOX is organized in 5 Work Packages (WPs). WP0 concerns coordination and management; WP1, WP2 and WP3 are experimental and scientific; WP4 concerns dissemination. Partner 1 (Univ. Nantes, CEISAM), coordinator of ELIPOX, will be in charge of all 5 Work Packages. 1 PhD student (WP1, WP2, WP3 and WP4) holding a Master degree in analytical/physical chemistry and 4 Master students (1 per year; WP1 and WP2) will be hired on the duration of ELIPOX (48 months). A partial release of the teaching duties of the PI will be funded by the ANR JCJC (64h/year on the duration of ELIPOX) in order to give time to the coordinator for managing her team and the project on the 5 WPs. Briefly, the scientific strategy of ELIPOX (WP1, WP2 and WP3) consists first to study the detection (sensitivity) of commercial and purified toxins with redox DMPC liposomes (WP1). Then the modulation of the liposomes lipid membrane composition with different types and ratios of phospholipids and cholesterol will be performed in order to design specific liposomes for the sensitive and selective detection of target toxins (WP2). The last scientific task will be to detect the target virulence factors from the pathogenic bacterial supernatant (more complex media) of cells culture (WP3).

Preliminary results (https://doi.org/10.1002/anie.202111416) have showed a weakening of DMPC redox liposomes (containing 0.5 M K4Fe(CN)6 as redox probe) at a submicromolar concentration (500 nM) of commercial Rhamnolipid (R90) after less than 30 minutes of incubation in solution. Current spikes appeared in the chronoamperometry curve, as a result of the electrolysis of the encapsulated redox probe released during the redox liposome impact onto the ultramicroelectrode. The size and shape of each current spike is in agreement with the broad size distribution of the hydrodynamic diameter of redox liposomes determined by dynamic light scattering (DLS) measurements.
These results are currently extended to delta toxin where the first experiments are promising and need to be repeated for the reproducibility of data.

The fundamental scientific impact of ELIPOX will provide first a better understanding of the mechanism intervening at the ultramicroelectrode / phospholipid liposomes interface during the single collision event. The ultimate impact of ELIPOX is to propose the most sensitive electrochemical detection technique for the selective identification of toxins released by pathogenic bacteria. The general idea in the medium and long term is to design an electrochemical platform allowing rapid and selective identification of toxins from pathogenic bacteria through the electrochemical single redox liposome nano-impacts technique.

The economical and societal impact of ELIPOX are obviously to design and develop an efficient electrochemical (bio)sensor for two of the most important bacteria in nosocomial infections responsible for 1 in 5 deaths worldwide. The strategy to detect by an indirect pathway the toxins released by these living bacteria at an early stage of infection is an ambitious and essential objective for medical and clinical applications. A cheap and easy handling biosensor with a high efficiency (sensitivity, selectivity, time of assay) is a challenging and necessary objective for the world health. The research proposed in ELIPOX will precisely contribute to this endeavour through a promising and original strategy with the electrochemistry of redox liposomes nano-impacts.

The potential of ELIPOX for patenting and for protecting the results will be screen before any publication and in this case, the University and other appropriate services will be consulted for advice.

Publication 1:
Recent Advances in Single Liposome Electrochemistry
H. Smida, C. Thobie-Gautier, M. Boujtita, E. Lebègue*
Current Opinion in Electrochemistry, 2022, 36, 101141.
DOI: doi.org/10.1016/j.coelec.2022.101141

The goal of ELIPOX is to design and develop a highly sensitive and specific electrochemical sensor device for the detection of virulence factors secreted by pathogenic bacteria.
In the ELIPOX proposal, electrochemistry of single redox liposome nano-impacts will be applied to the detection of toxins from two bacteria responsible for nosocomial infections: the d-Hemolysin from Staphylococcus aureus and the Rhamnolipid from Pseudomonas aeruginosa.
The electrochemical sensing principle of ELIPOX is based on the weakening of the liposomes lipid membrane upon interaction with destructive bacterial virulence factors which leads upon impact at an ultramicroelectrode to the breakdown of the liposomes and the release/electrolysis of its encapsulated redox probe.
ELIPOX is mainly supported by the coordinator’s previous results on electrochemical single collisions of redox liposomes with the objective to extend this strategy for sensing two target toxins (produced by two pathogenic bacteria), known for interacting with the lipid membrane of liposomes.
The main research hypothesis of ELIPOX is based on the previous results of the coordinator where no current spike was observed in the chronoamperometry curve because the redox liposomes did not break during impact (or collision) onto the ultramicroelectrode surface. In contrast, in the presence of the two target secreted toxins in solution (acting like a surfactant in the lipid membrane), current spikes corresponding to the electrolysis of the encapsulated redox probe released from weakened liposomes are detected.
The main challenge of ELIPOX will be to optimize and adapt the liposomes lipid membrane composition in order to specifically detect the two target toxins and to reach high sensing selectivity, which is of critical importance for biosensor applications.
The expected results of ELIPOX are the most sensitive electrochemical detection toward the target toxins (sub-micromolar) in a short time analysis (30 minutes maximum) with an easy handling and cheap technique.