Impedance based Aluminium Interdigitated Electrode (Al-IDE) Biosensor on Silicon Substrate for Salmonella Detection

Si is one of the most common, and prominent element in electronic field. In this research, Al based interdigitated electrical biosensors was prepared using Si as base material to detect Salmonella enterica typhi (S. typhi). The usage of the IDE sensors in the biosensor field is tremendous in these days because of the large number of comb structured finger electrodes gain high sensitivity. S. typhi is a very harmful food borne pathogen, makes typhoid disease which causes many deaths annually in worldwide. The AutoCAD software was used to design the chrome mask of IDE sensor. The fabrication process was done using conventional photolithography method. The fabricated Al-IDE, morphologically analyzed using SEM and further structurally characterized using EDX. The SEM depicted the well fabricated interdigitated electrode fingers and finger gaps are nearly equal to 50 μm and 1μm, respectively as designed dimensions. Silanization by APTES, immobilization with carboxylic functionalized S. typhi ssDNA probes and blocking with tween-20 were the major functionalization steps. The sensitivity measurements were done using different concentration of complementary targets and selectivity measurements were done using complementary, non-complementary and single base mismatch ssDNA samples. Each step was electrically characterized using Nyquist plot by impedance analyzer. Selectivity measurement confirmed, the tween-20 was important for the specificity of biosensor. The sensitivity measurements further verify that the biosensor is appropriate for detection of various concentrations from 1 fM to 1 μM of S. typhi targets.