A simple electrochemical immunosensor based on MWCNTs-COOH/ Fc-COOH@CoAl-LDH, nanocomposite for sensitive detection of the tumor marker CA724

A novel label-free electrochemical immunosensor for the ultrasensitive determination of cancer antigen (CA724) was developed using a novel composite of CoAl layered double hydroxides (CoAl-LDH) and carboxylfunctionalized multiwall carbon nanotubes (MWCNTs-COOH) as platform and ferrocenecarboxylic acid (FcCOOH) as signal label. The MWCNTs-COOH/Fc-COOH@CoAl-LDH composite was prepared by a convenient and simple one-step ultrasonic method, and various characterization techniques consisting of scanning electron microscopy (SEM), transimission electronic microscopy (TEM), TEM-Mapping, fourier transform infrared (FTIR), X-ray diffraction (XRD) and X-ray photoelectronic energy spectrum (XPS) were applied to study the size and morphological features. Due to its large specific surface area and multilayer structure, the CoAl-LDH can be postdoped to embed a large amount of signal probe to realize the amplification of the internal reference signal Fc. In addition, the higher conductivity of MWCNTs-COOH compensates for the deficiency of CoAl-LDH, which effectively strengthened the electron transfer efficiency of electrochemical signaling substances. The optimal experimental conditions were detected to be 2.5 mmol of Fc-COOH, 4.0 mg/mL of concentration, pH 6.0, incubation time of 40 min, and incubation temperature of 37 degree celsius. Under optimal conditions, the fabricated sensor exhibits linearity in a wide dynamic range covering the physiological concentration, from 0.001 to 100 U/mL and the limit of detection (LOD) was 0.03962 mU/mL, the calibration equation is stated as triangle I = 7.76363 log10CCA724 + 40.50351 (R2 = 0.99674). The sensor is successfully detects trace levels of CA724 in human serum with excellent recovery rates ranging from 100.52 %-102.30 %, proving the synergy of MWCNTs-COOH/FcCOOH@CoAl-LDH as a promising platform for electrochemical sensing for clinical detection of other disease markers.