Rapid and selective electrochemical sensing of bacterial pneumonia in human sputum based on conductive polymer dot electrodes

A rapid wireless electrochemical biosensor that can discriminate between gram-negative and gram-positive bacteria is designed for the selective detection of pneumonia pathogens in human sputum. The selective binding with the bacterial cell wall of gram-negative and gram-positive bacteria is achieved by utilizing colistin- and vancomycin-conjugated polymer dot-coated electrodes (PD-Colis for gram-negative and PD-Vanco for gram-positive, respectively) and can be observed as changes in resistance (ΔR~12–15 kΩ for PD-Colis and ΔR~13–17 kΩ for PD-Vanco). The PD-Colis- and PD-Vanco-coated electrodes demonstrate high sensitivities determined by the low limit of detection (LOD) for both gram-negative (3.0 CFU/mL, R²=0.995) and gram-positive (3.1 CFU/mL, R²=0.994) bacteria. The electrodes can also be used to detect antibiotic-resistant bacteria, such as carbapenem-resistant K. pneumoniae (CRKP) and methicillin-resistant S. aureus (MRSA), as well as enabling selective detection in complex media such as human serum. Moreover, the sensors based on PD-Colis- and PD-Vanco-coated electrodes show excellent performance in real clinical samples such as human sputum. Finally, the integration of the sensor with a wireless sensing system provides in-line bacterial detection and allows monitoring via a smartphone. We anticipate that the bacterial sensor can be potentially used for the rapid and accurate diagnosis of bacterial infections in the clinic.