Oxidative stress during bacterial growth characterized through microdialysis sampling coupled with HPLC/fluorescence detection of malondialdehyde

• First report of dynamic monitoring of MDA during periods of microbial growth.
• Protein-free samples obtained without the need for further sample pretreatment.
• A simple-to-operate, real-time, eco-friendly procedure.

Organisms that grow aerobically are routinely exposed to oxidative stress in the form of reactive oxygen species. Monitoring the dynamic variations of oxidative stress allows us to understand its role in basic cellular function and determine mechanisms of antioxidation. In this study, microdialysis (MD) sampling was employed for continuous monitoring of the formation of malondialdehyde (MDA) in a bacterium-inoculated culture broth. To test the practicality of this approach, oxidative stress was induced by cadmium and then a 60-min interval was selected to collect sufficient amounts of dialysate for high-performance liquid chromatography with fluorescence (HPLC-FL) detection. After optimization of this simple-to-operate, simultaneous, and continuous method for dynamic monitoring of MDA during periods of bacterial growth, a retrodialysis technique and a no-net-flux method were used to assess the probe recovery and analytical performance of the proposed system. The mean probe recovery of MDA was 78.6 ± 0.9%, with intra- and interday precisions of 2.7–6.1 and 3.5–7.6%, respectively. To evaluate the practicality of this method, the dynamic variations in the concentrations of MDA in standardized bacterial species (Staphylococcus aureus, ATCC® 29213™) were monitored continuously for 24 h. The analytical results confirmed that this MD sampling technique combined with HPLC-FL detection can be used to accurately and continuously monitor the levels of MDA in microbially inoculated culture broths.