Ultrasensitive nanohybrid electrochemical sensor to detect LipL32 gene of Leptospira interrogans

We report an ultrasensitive nanohybrid electrochemical DNA sensor developed to detect the LipL32 gene of Leptospira interrogans that causes leptospirosis. A carboxylated multiwalled carbon nanotubes electrode with gold nanoparticles (c-MWCNTs/nano-Au) was modified with polyamidoamine (PAMAM) and graphene quantum dots using cysteine (Cys) as a linker. The c-MWCNTs/nano-Au electrode was covalently bonded to polyamidoamine (PAMAM) via Cys through Au-SH bonding. The amino group of PAMAM was linked to carboxyl moiety of graphene quantum dots (GQD) to form a c-MWCNTs/nano-Au/Cys/PAMAM/GQD nanohybrid electrode. A 5'-amino (NH2) labeled single-stranded DNA (ssDNA) probe based on the LipL32 gene was immobilized on the surface of a c-MWCNTs/nano-Au/Cys/PAMAM/GQD nanohybrid electrode. The different dilutions of single-stranded genomic DNA (ssG-DNA) of L. interrogans were treated on immobilized DNA probe to allow the hybridization. The hybridization events are measured using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) using redox indicators of 1 mM methylene blue and potassium ferricyanide. Field emission scanning electron microscopy (FE-SEM) was performed to analyze the modifications done on the surface of the electrode. The developed nanohybrid sensor has a sensitivity of 1952.3 mu A cm(-2) ng(-1) and a lower limit of detection (LOD) of 0.112 pg/mu l (R-2 = 0.98). The nanohybrid sensor showed good reproducibility over a period of 6 months, exhibiting only a 10% loss in actual DPV current. The developed nanohybrid sensor is found to be specific to L. interrogans with high sensitivity and reproducibility, and it can be used for routine analysis for L. interrogans identification and leptospirosis diagnosis.

Automated summary

An ultrasensitive nanohybrid electrochemical DNA sensor was developed for detecting the LipL32 gene of Leptospira interrogans, showing high sensitivity and specificity with a lower limit of detection of 0.112 pg/mu l. The sensor exhibited good reproducibility over a 6-month period, making it suitable for routine analysis in the identification of L. interrogans and diagnosis of leptospirosis.