Redox-active biomolecules such as Ascorbic acid (AA), Dopamine (DA), Uric acid (UA), Tryptophan (Trp), Xanthine (XA), and Caffeine (CA) are all critical for biological homeostatic maintenance. The depletion or over consumption in any of the biomolecules can lead to detrimental effects. For example, previous reports have suggested the depletion of dopamine in the brain is highly correlated to the progression of Parkinson’s disease 1. Caffeine, though not a bio-molecules, it is frequently consumed, and overdose can lead to neurological damage, or even death 2,3. In extension, these bio-molecules tend to exists as a mixture. Thus, it becomes important to develop a platform that enables the monitoring of these biomolecule concentrations simultaneously.In recent years, carbon nanotubes have collected a great amount of attention from the electrochemical sensor development communities 4. Due to their high surface to volume ratio, carbon nanotubes are able to enhance the electrical catalytic activity increasing the overall conductance 5. This characteristic is highly essential as not only it can increase the potential application range, it can also resolve and separate for biomolecules that have overlapping redox-potentials. In addition, nanotubes are highly biocompatible and do not pose a toxic effect on the biological system. In this work, a novel immobilized ferric cyanide-chitosan polymer ion pair on the multi-walled carbon nanotube-based nanocomposite was synthesized and utilized for the construction of a sensor platform capable of simultaneously detecting six redox-active biomolecules.Using Fourier-transform infrared spectroscopy, and scanning electron microscopy, the nanocomposite was shown to be successfully synthesized. Cyclic voltammetry, and electrochemical impedance spectroscopy both demonstrated the final modified electrode has improved electrochemical activity. Using differential pulse voltammetry, AA, DA, UA, Trp, XA, and CA were all detected simultaneously (Shown in Figure 1). Finally, the sensor performance was analyzed in real samples and demonstrated a comparable performance. These results demonstrated the reported sensor has a strong potential to become the next generation of biosensors. Reference 1. A. Nobili et al., Nat. Commun., 8, 14727 (2017).2. J. W. Daly, Cell. Mol. Life Sci., 64, 2153–2169 (2007).3. B. J. Gurley, S. C. Steelman, and S. L. Thomas, Clin. Ther., 37, 275–301 (2015).4. J. Wang, Electroanalysis, 17, 7–14 (2005).5. A. Eatemadi et al., Nanoscale Res. Lett., 9, 1–13 (2014). Figure 1