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

A novel enzyme-free and all-carbon photoelectrochemical (PEC) bioprobe, based on carboxylated multiwalled carbon nanotube–Congo red–fullerene nanohybrids (MWNTCOOH–CR–C₆₀), for the ultrasensitive immunosensing of carcinoembryonic antigen (CEA) was reported. The MWNTCOOH–CR–C₆₀ nanohybrids, prepared by mechanically grinding a mixture of MWNTCOOH, C₆₀, and CR at a certain mass ratio, had good water dispersibility and high PEC conversion efficiency in visible light ranges. Covalent binding of the detection antibody of CEA on the MWNTCOOH–CR–C₆₀ nanohybrids produced a sensitive PEC 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∼100.0 ng/mL and a low detection limit of 0.1 pg/mL (calculated 5 zmol for a 10.0 μL 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 PEC biosensors

White-Light-Exciting, Layer-by-Layer-Assembled ZnCdHgSe Quantum Dots/Polymerized Ionic Liquid Hybrid Film for Highly Sensitive Photoelectrochemical Immunosensing of Neuron Specific Enolase

ZnCdHgSe quantum dots (QDs) functionalized with <i>N</i>-acetyl-l-cysteine were synthesized and characterized. Through layer-by-layer assembling, the ZnCdHgSe QDs was integrated with a polymerized 1-decyl-3-[3-pyrrole-1-yl-propyl]­imidazolium tetrafluoroborate (PDPIT) ionic liquid film modified indium tin oxide (ITO) electrode to fabricated a photoelectrochemical interface for the immobilization of rabbit antihuman neuron specific enolase (anti-NSE). After being treated with glutaraldehyde vapor and bovine serum albumin successively, an anti-NSE/ZnCdHgSe QDs/PDPIT/ITO sensing platform was established. Simplely using a white-light LED as an excitation source, the immunoassay of neuron specific enolase (NSE) was achieved through monitoring the photocurrent variation. The polymerized ionic liquid film was demonstrated to be an important element to enhance the photocurrent response of ZnCdHgSe QDs. The anti-NSE/ZnCdHgSe QDs/PDPIT/ITO based immunosensor presents excellent performances in neuron specific enolase determination. The photocurrent variation before and after being interacted with NSE exhibits a good linear relationship with the logarithm of its concentration (log <i>c</i>_NSE) in the range from 1.0 pg mL^–1 to 100 ng mL^–1. The limit of detection of this immunosensor is able to reach 0.2 pg mL^–1 (<i>S</i>/<i>N</i> = 3). The determination of NSE in clinical human sera was also demonstrated using anti-NSE/ZnCdHgSe QDs/PDPIT/ITO electrode. The results were found comparable with those obtained by using enzyme-linked immunosorbent assay method