Laser-induced graphene-based aptasensor for the selective detection of Escherichia coli in urine samples

A Laser-Induced Graphene-based (LIG) electrode covalently functionalized with an aptamer (P12-55) was used to develop an aptasensor detecting Escherichia coli in urine samples. Recent strides in material science have spotlighted LIG for exceptional attributes like robust mechanical resistance, superior conductivity, extensive surface area, and facile synthesis/patterning on various polymeric substrates. Variations in the aptasensor charge transfer resistance upon interaction with bacterial cells were evaluated by electrochemical impedance spectroscopy. Tests in phosphate buffer saline solution showed the aptasensor linear response for E. coli between 10⁰ and 10³ CFU/mL. The sensor proved to be selective for E. coli as a negligible response was observed in the presence of Staphylococcus aureus or Pseudomonas aeruginosa. Finally, the sensor was calibrated in urine samples spiked with a known concentration of E. coli cells. Its characteristics make the aptasensor viable for low-cost and portable devices identifying pathogenic microorganisms at the point-of-need. Due to the short response time (about 30 min), we believe that these sensing devices may significantly improve control and management of urinary tract infections.