Ultrasensitive All-Carbon Photoelectrochemical Bioprobes for Zeptomole Immunosensing of Tumor Markers by an Inexpensive Visible Laser Light

A novel enzyme-free and all-carbon photo-electrochemical (PEG) bioprobe, based on carboxylated multiwalled carbon nanotube-Congo red-fullerene nano-hybrids (MWNTCOOH-CR-C-60), for the ultrasensitive immunosensing of carcinoembryonic antigen (CEA) was reported. The MWNTCOOH-CR-C-60 nanohybrids, prepared by mechanically grinding a mixture of MWNTCOOH, C-60, and CR at a certain mass ratio, had good water dispersibility and high PEG conversion efficiency in visible light ranges. Covalent binding of the detection antibody of CEA on the MWNTCOOH-CR-C-60 nanohybrids produced a sensitive PEG bioprobe for detection of CEA by sandwich immunosensing. The corresponding immunosensor, employing an inexpensive and portable green laser light, possessed a wide calibration range of 1.0 pg/mL similar to 100.0 ng/mL and a low detection limit of 0.1 pg/mL (calculated 5 zmol for a 10.0 mu L sample solution) (S/N = 3), which was successfully applied to the detection of CEA in serum samples from both healthy people and cancer patients. The present work thus demonstrated the promising application of fullerene-based nanocomposites in developing highly sensitive, environmentally friendly, and cost-effective PEG biosensors.