Design, development and characterization of a handheld electrochemical analyzer system : in the perspective of DNA biosensors for foodbourne pathogen detection

peer-reviewedDetailed in this work is the design and development of a novel handheld electrochemical analyzer system interfaced to smart phone. The custom made electrochemical analyzer is versatile, cost-effective and can be used for real-time applications. The electrochemical analyzer was characterised for electron transfer events associated with chemical and biological samples. The presented design was implemented based on the Arduino Nano open source electronics prototyping platform. This platform includes a microcontroller, which is then connected to a custom made electrochemical analyzer circuit. In a novel approach, the versatility of the instrument was further demonstrated by employing the electrochemical analyzer to a modified electrochemical cell which formed the basis of a DNA biosensor. The cyclic voltammetry technique was used to impose a triangular waveform on an electrochemical cell and the resulting current through the cell was then monitored. The DNA biosensor generated unique electrical signals in real-time between complementary and non-complementary oligonucleotides sequences of the Bacillus cereus DNA and it proved to be effective. Investigations were also undertaken by employing a commercial electrochemical analyzer for label-free detection of DNA hybridization using impedimetric, potentiometric and amperometric techniques. Impedance measurements are performed without using additional redox probes. The effects of hybridization and non-specific binding were compared when the probe DNA molecules were immobilized by different immobilization methods on a conducting polymer matrix. The results showed that the probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to other immobilization methods. Control experiments were also performed to prove the specificity of the biosensor in the presence of noncomplementary oligonucleotide and no unspecific bonding with the immobilized probe was observed. The performance of the DNA sensor proved to be effective in terms of selectivity, sensitivity and reproducibility of hybridization events. Analysis of these DNA probes showed that the minimum level of detection was 33.3 pg/ml (103 CFU/ml). The implications of the experimental results obtained are discussed as are the insights they provide into further development of the analyzer. Future work would include interface of a smaller scale sensor heads to use in a handheld electrochemical analyzer system to detect environmental variables including pathogenic micro-organisms in realtime. Individual sensors are based on the unique DNA signature of the specific foodborne bacterial pathogen(s) will be developed. Based on sensor identification of these pathogens, it will be possible to detect them directly from the food source