Bio-inspired polynorepinephrine based nanocoatings for reduced graphene oxide/gold nanoparticles composite for high-performance biosensing of Mycobacterium tuberculosis

Polydopamine (PDA) has established itself as a promising grafting and coating material, particularly for func-tional group-deprived electrochemically active nanomaterials such as graphene, MXene, CNT, metal nano -particles, and so on, and has proven its extensive applicability in the design and development of electrochemical biosensor devices. However, polynorepinephrine (PNE), a sister compound of PDA, having additional -OH groups and greater coating uniformity and biocompatibility, has never been studied in the field of biosensors. Herein, we investigated PNE as a coating material for reduced graphene oxide (RGO) and gold nanoparticles (Au) in order to build an electrochemical genosensor for Mycobacterium tuberculosis (MTB) detection. Biotin-Avidin chemistry was used to covalently immobilize probe DNA (ssDNA) specific to MTB to the nanocomposite sur-face on glassy carbon electrode (GCE) in order to construct biosensing electrodes. The formation of RGO/PNE and RGO/PNE/Au nanocomposite as well as the immobilization of ssDNA onto the bioelectrodes are both corroborated by UV-Visible, Raman, and XRD studies with FE-SEM and HR-TEM analysis. The electrochemical studies performed using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) showed the significant enhancement in charge transfer kinetics of RGO/PNE/GCE and RGO/PNE/Au/GCE electrode compared to GO/ GCE electrode. The biosensing investigations performed using ssDNA/avidin/RGO/PNE/Au/GCE bioelectrode showed high sensitivity (2.3 x 10-3 mA mu M-1), low detection limit (0.1 x 10-7 mu M), broad detection range (0.1 x 10-2 to 0.1 x 10-7 mu M) with good selectivity and low response time (5 s) of the developed sensor. In com-parison to the analogous RGO/PDA/Au material system, RGO/PNE/Au demonstrated increased enzyme loading, improved electrochemical responsiveness, and superior biosensing performance.