Azam Yaghoobi - Department of Microbiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah
Alireza Jalalvand - Research Center of Oils and Fats, Research Institute for Health Technology, Kermanshah University of Medical Sciences, Kermanshah
Ramin Abiri - Department of Microbiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah
Amirhoushang Alvandi - Department of Microbiology, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah
Elham Arkan - Nano Drug Delivery Research Center, Research Institute for Health Technology, Kermanshah University of Medical Sciences, Kermanshah

Background and Aim : We have constructed a novel electrochemical biosensor for detection andquantification of the Streptococcus Pneumoniae bacteria (SPB) based on change inelectrochemical impedance spectroscopic (EIS) responses of the biosensing system.Methods : A glassy carbon electrode (GCE) was chosen as the platform of the biosensor and itwas modified with lead nanoparticles (Pb NPs) and then, DNA-[FAM]CGC AAT CTA GCA GATGAA GCA GGA AAA AAA AAA [Thiol] (DNA-FAM-S) was loaded onto Pb NPs as a selectiveprobe for sensitive and selective deter- mination of the SPB. After electrochemical andmicroscopic characterization of the modifications applied to the GCE, analytical characterizationof the biosensor was performe.Results : The biosensor had a limit of detection of ۰.۰۰۲۲ ng/ml ~ ۶۲۲ SPBs and a sensitivity of۳۴۳۲.۹ ? (ng/ml). The biosensor response was selective, sensitive, stable, repeatable andreproducible in determination of the SPB. The biosensor performance for determination of the SPBwas comparable with the NanoDrop method which encouraged us to recommend it for practicalpurposes.Conclusion : This paper was very interesting from experimental point of view which developed anovel electroanalytical method for determination of the SPB which showed a comparableperformance with a reference method. Interesting results were obtained from different sections ofthis study and we justified them. Structure of the biosensor was efficiently engineered whoseselectivity was guaranteed by the presence of the DNA-FAM-S while its sensitivity was supportedby the presence of PbNPs and using the EIS as a sensitive electroanalytical method. The biosensorshowed good stability, repeatability and reproducibility as well. After calibration of the biosensorresponse towards determination of the SPB, its performance was statistically and graphicallycompared with the NanoDrop as a reference method which confirmed a good practicalperformance for the biosensor for detection and determination of the SPB.

Biosensor, Streptococcus Pneumoniae, Electrochemical impedance spectroscopy