Design and evaluation of the sensing characteristics of a polyaniline-biotinlylated antibody pseudomonas aeruginosa biosensor

Abstract

Although there are many diagnostic and detection platforms for detection of various bacteria, these often require large elaborate procedures and well trained experts to execute. The turnaround time for results can sometimes be long. The development of portable and low power devices integrated biosensors is making available devices that can be used at the point-of-care. Such devices often can give immediate results. Rapid detection of bacterial pathogens is critical in the diagnosis of infectious disease. Pseudomonas aeruginosa is a nuisance bacteria that is also found in hospital environment that can cause fatality if there is a delay in detection. A biosensor based on polyaniline thin films and biotinylated anti-Pseudomonas aeruginosa polyclonal antibodies has been developed that enables the detection of P. aeruginosa bacteria. Thin films comprising polyaniline nano fibres were developed via in-situ polymerization on glass slides. Fourier Transform Infrared (FTIR) spectroscopy and UV/Vis spectroscopy were used for functional group analysis and determination of optical properties. The effect of polymerization time and thermal treatment on morphology and electrical properties was investigated. The morphological characteristics were determined using Atomic Force Microscopy (AFM) whilst electrical properties were determined using a four-point probe coupled to a source meter. Anti-P. aeruginosa biotinylated polyclonal antibodies were immobilized on avidin treated polyaniline thin films. Sensing characteristics of polyaniline films were evaluated in biosensor detection set-up. The set-up consisted of a helium-neon laser interfaced with a cadmium sulphide LDR detector connected to a circuit incorporating a multimeter. The changes in light intensity were observed to be directly proportional to the amount of bacteria bound by the antibodies that reflected an increase in the resistance of the films. The resistance was found to increase linearly with increasing bacteria concentration. Bacteria concentrations in unknown samples were determined rapidly in under 5 minutes. The lower detection limit of the sensor was found to be 9.0×105 CFU/ml. Selectivity was demonstrated with the E.coli cross-reactivity test, which showed no biosensor response in comparison to the response seen with the P. aeruginosa tests. We have successfully developed and tested a biochip that can be used in sensor devices for rapid determination of P. aeruginosa bacteria.