Inkjet-Printed Carbon Nanotube Electrodes for Measuring Pyocyanin and Uric Acid in a Wound Fluid Simulant and Culture Media

Polyacrylamide-coated, carbon nanotube (PA/ CNT) electrodes were prepared by an inkjet printing process and used to measure pyocyanin and uric acid in a wound fluid simulant at 37 °C. These two molecules are potential indicators of infection, and therefore their detection could prove useful for monitoring wound healing. Pyocyanin is a marker for the common wound bacterium Pseudomonas aeruginosa. Our long-term goal is to use these inexpensive and disposable electrodes to measure biomarkers of wound healing directly. In this proof-of-concept work, studies were performed in a wound fluid simulant to evaluate the stability of the electrodes and their responsiveness for the two bioanalytes. The PA/CNT inkjet-printed electrodes and electrical contacts were stable with unchanging physical and electrochemical properties in the wound fluid simulant over a 7−8-day period at 37 °C. The detection figures of merit for pyocyanin in the simulant at 37 °C were as follows: linear over the physiologically relevant range = 0.10 to 100 μmol L−1 (R2 = 0.9992), limit of detection = 0.10 μmol L−1 (S/N = 3), sensitivity = 35.6 ± 0.8 mA-L mol−1 and response variability ≤4% RSD. The detection figures of merit for uric acid in the simulant at 37 °C were as follows: linear over the physiologically relevant range = 100 to 1000 μmol L−1 (R2 = 0.9997), sensitivity = 2.83 ± 0.01 mA-L mol−1, and response variability ≤4% RSD. The limit of detection was not determined. The PA/CNT electrodes were also used to quantify pyocyanin concentrations in cell-free culture media from different strains of P. aeruginosa. The detected concentrations ranged from 1.00 ± 0.02 to 118 ± 6 μM depending on the strain.