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

Polyacrylamide-coated, carbon nanotube (PA/CNT)electrodes were prepared by an ink-jet printing process and used to measure pyocyanin and uric acid in a wound fluid simulant at 37 oC.These two moleculesare potential indicators of infection and therefore their detection could proveusefulfor monitoring wound healing. Pyocyanin is a marker for the common wound bacterium, Pseudomonas aeruginosa. Ourlong-term goal is to use these inexpensive and disposable electrodes to measurebiomarkers of wound healing directly. In this proof-of-concept work, studieswere 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 oC. The detection figures of merit for pyocyanin in the simulant at 37 oC were as follows: linearover the physiologically-relevant range= 0.10to 100μmol L-1(R2= 0.9992), limit of detection = 0.10 μmol L-1(S/N =3), sensitivity = 35.6 ± 0.8 mA-L mol-1and response variability≤ 4% RSD. The detection figures of merit for uric acid in the simulant at 37 oC were as follows: linear over the physiologically relevantrange = 100 to 1000 μmol L-1(R2= 0.9997), sensitivity = 2.83 ± 0.01 mA-Lmol-1and 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 fromdifferent strains of P.aeruginosa. The detected concentrations ranged from 1.00 ± 0.02 to 118 ± 6 μM depending on the strain.