Highly Sensitive Photoelectrochemical Immunosensor Based on Organic Multielectron Donor Nanocomposite as Signal Probe

Organic photoelectric materials with conjugated electron-rich structures and good biocompatibilities have broad application prospects in biosensors. Herein, we report a promising organic photoelectric multielectron donor nanocomposite for highly sensitive PEC immunoassays. Specifically, the organic multielectron donor nanocomposite (DA-ZnTCPP-g-C₃N₄) was prepared from dopamine (DA, polyphenol hydroxyl structure substance), zinc tetracarboxylate porphyrin (ZnTCPP, large p-π conjugated heterocyclic compound), and two-dimensional graphene-like nitrogen carbide (g-C₃N₄) via an amidation reaction. With a multielectron donor structure and photoelectricity, this nanocomposite can achieve sensitization by self-structure without the addition of an electron donor in the test solution. It was utilized to label the carcinoembryonic detection antibody as a immuno-probe (Ab2-DA-ZnTCPP-g-C₃N₄). Meanwhile, the glassy carbon electrode electrodeposited with gold nanoparticles anchoring the capture antibody was used as a PEC immunomatrix (Ab1/DpAu/GCE). The enhanced PEC current, "signal on", was confirmed by the immunosensor via sandwich immunorecognition of a carcinoembryonic antigen (CEA). Under optimal conditions, the as-prepared sensing platform displayed high sensitivity for CEA with a dynamic linear response range from 10 fg·mL^-1 to 1 mg·mL^-1 and a lower detection limit of 3.6 fg·mL^-1. This organic nanocomposite showed good sensitivity and stability in an immunosensing system with a low background. This strategy affords a promising approach for biological applications of organic photoelectric materials.