Lignin derived nanoparticle intercalation on nitrogen-doped graphene quantum dots for electrochemical sensing of cardiac biomarker

[Display omitted] •Fabricated LSG_N-GQDs_Ag NPs nanocomposites under finely tuned hydrothermal method.•Shown novel lignin-derived 3D graphene nanostructure through laser scribing method.•Ability of LSG_N-GQDs_Ag NPs-1000 for impedance was proved to distinguish AMI.•A clear demonstration was displayed and attained detection limit up to femtomolar.•Developed biosensor has opened wide ideas for future nanocomposite developments. Lignin-scribed graphene (LSG) conjugated with nitrogen-doped graphene quantum dots (N-GQDs) and lignin-derived silver nanoparticles (Ag NPs) was developed through a hydrothermal process for the electrochemical sensing of Troponin I, a cardiac biomarker for Acute Myocardial Infarction (AMI). A nanocomposite with optimal conduction mechanism was developed by varying the N-GQDs doped amount intercalated on the surface of LSG. The nanocomposite was characterised by morphological, physical, and structural examinations. The Ag NPs and N-GQDs were found uniformly distributed on the LSG surface, with selective capture of the biotinylated aptamer probe on the bio-electrode indicative of the specific interaction with Troponin I, resulting in an increment in the charge transfer resistance following hybridisation analysis. The detection limit, as determined through impedance spectroscopy, was 1 fM or 30 fg/mL, with high levels of linearity, selectivity, repeatability, and stability of the sensor. This nanocomposite opens a new avenue for array-based medical diagnostics.