Showcasing advanced electrocatalytic behavior of layered double hydroxide wrapped on carbon nanotubes: Real-time monitoring of L-cysteine in biological matrices

L-cysteine is an imperative amino acid which exists in natural proteins and plays crucial roles in biological systems, thereby its sensitive and selective monitoring is extremely necessary. In this work, novel hybrid nanoarchitectures have been fabricated by wrapping positively charged NiAl layered double hydroxide (LDH) nanosheets on negatively charged carbon nanotubes (CNTs). The electrochemical behavior of CNTs@NiAl LDH hybrids having different concentrations of NiAl LDH precursor salts with fixed amount of CNTs have been explored in detection of L-cysteine using cyclic voltammetry and amperometry techniques. High conductivity of CNTs together with enhanced electrocatalytic properties of NiAl LDH and plentiful surface active sites are accountable to facilitate the direct detection of L-cysteine. Therefore, the fabricated electrode exhibits excellent sensing performance with 0.05 µM to 780 µM wide linear range, sensitivity of 351 μA mM−1 cm−2, low limit of detection upto 3 nM (S/N = 3), superb reproducibility and stability as well as brilliant selectivity against common interferents. Arising from remarkable efficiency, the CNTs@NiAl LDH based sensing system has been practically used in real-time detecting L-cysteine effluxes from different living cells upon stimulation as-well-as in-vitro monitoring of L-cysteine concentrations in human samples (urine and serum).