Chemically modified nanoparticles surface for sensing bacterial loading—experimental study based on fluorescence stimulation by iron ions

The influence of iron ions supplied from magnetite nanoparticles with chemically modified surface on Pseudomonas aeruginosa germ was aimed—with experimental and theoretical approach of the intensity of the fluorescent signal emitted by the pyoverdine like siderophores. As the coated magnetic nanoparticles could function as probes, the possibility of designing a chemical device was considered based on the sensing of iron reduction from Fe3 + into the more soluble Fe2 +, for detecting various levels of contamination (10 ÷ 108 cell/ml) of biological specimens and environmental samples. The proposed mathematical model estimated the fluorescence intensity due to siderophore synthesized by Pseudomonas, considering that the parameter describing the ion–bacteria interaction depends differently on the cell density for different magnetite nanoparticle coatings: linear dependence was found in the case of sodium oleate coating while power function was revealed for tetramethyl ammonium coating of magnetite nanocores, in both cases magnetite suspension being supplied in the same concentration (0.1 μl/ml). The calculated values of fluorescence intensity fitted the experimental data corresponding to magnetite supplied bacteria with graph slopes close to the unit and correlation coefficients of 0.999 and 0.996, while for the control samples, where that parameter was zeroed, correlation coefficient was found of 0.999.

► We report fluorescence based detection of P. aeruginosa using coated magnetite cores.
► Different coatings seem to stimulate differently Pseudomonas siderophore yielding.
► Theoretical model evidenced different parametrical approach of fluorescence increase.
► Biosensor design is proposed based on Fe3 + reduction during siderophore production.