Graphene-based Portable SPR Sensor for the Detection of Mycobacterium tuberculosis DNA Strain

In this study, we presented the novel concept of graphene utilization for the detection of Mycobacterium tuberculosis DNA (deoxyribonucleic acid) hybridization in surface plasmon resonance (SPR) biosensor. The DNA sequences were obtained from DNA fragment IS6110, which was proven as the stable biomarker for Mycobacterium tuberculosis complex (MTBC). A few graphene layers on top of SPR sensing chip were deposited by simple drop casting method from its dispersion solution. The presence of graphene layers plays the major role for single strain DNA immobilization. The single strain DNA (ssDNA) was covalently bond with the gold nano urchin (GNu) as the sensing probe (ssDNA-GNu). The binding mechanism between graphene layers and ssDNA probe is mainly due to the π-π stacking force. Furthermore, hydrogen bond influences the hybridization mechanism of the complementary single strain DNA (cssDNA) and the ssDNA; which has the higher energy compared to the π-π stacking force. Consequently, the presence of the cssDNA target in the reaction chamber disrupts the ssDNA-GNu from the few graphene layers. The experimental results demonstrated the detection limit of this method was achieved around 28 fM of cssDNA target in the salt buffer.