Carboxymethyl cellulose assisted preparation of water-processable halloysite nanotubular composites with carboxyl-functionalized multi-carbon nanotubes for simultaneous voltammetric detection of uric acid, guanine and adenine in biological samples

Uric acid (UA), a waste product of purine derivatives catabolism, is one of the main culprits of gout. In this paper, a simple and sensitive method for the simultaneous voltammetric detection of UA and the most common purine derivatives like guanine (G) and adenine (A) in human serum and lettuce samples was successfully realized using glassy carbon electrode (GCE) modified with the water-processable nanotubular composites consisting of both halloysite nanotubes (HNTs) and carboxyl-functionalized multi-walled carbon nanotubes ( f MWCNTs) that were well dispersed by carboxymethyl cellulose (CMC). A water-processable HNTs hybrid nanotubes with f MWCNTs were successfully prepared using CMC assist, and the CMC-HNTs- f MWCNTs composites were characterized by scanning electron microscopy, fourier-transform infrared spectroscopy, transmission electron microscope, electrochemical impedance spectroscopy , cyclic voltammetry and chronocoulometry . CMC-HNTs- f MWCNTs/GCE displayed enhanced electrode stability in water, effective surface area, adhesive property and adsorption capacity, and electrocatalytic activity for the oxidation of UA, G and A, which could simultaneously detected three purine derivatives in linear ranges from 1 to 130   μM with a limit of detection (LOD) of 0.5   μM for UA, 0.05 to 9   μM with LOD of 0.018   μM for G, and 0.3 to 25   μM with LOD of 0.19   μM for A, respectively. The as-fabricated sensor displayed high sensitivity, low detection limit, good sensing stability, remarkable feasibility, and satisfactory practicality.