The present invention discloses an electrochemical biosensor for rapid, highly sensitive detection of pyocyanin as a biomarker of bacterial Pseudomonas aeruginosa infection, and a method thereof. The electrochemical biosensor comprises a nanocomposite selected from a group comprising a gold nanoparticle, a silver nanoparticle, a platinum nanoparticle, an indium tin oxide nanoparticle, a polymer dot, a carbon, a carbon nanotube, a carbon nanofiber, a graphene and any combinations thereof, and a biorecognition sensing material dispersed in the nanocomposite comprising a nucleic acid binding species or aptamer containing reporter molecules configured for transducing molecular recognition of pyocyanin molecules increasingly concentrated from a fluid sample deposited thereon to a differential current signal. The biorecognition sensing material selectively subjects the concentrated pyocyanin molecules to a controlled voltage waveform that oxidizes the pyocyanin molecules, resulting in a response current signal to the said controlled voltage waveform representing a concentration of the pyocyanin in the fluid sample thereof.