Vol.:(0123456789) Discover Nano (2024) 19:37 | https://doi.org/10.1186/s11671-024-03980-3 Discover Nano Research Bio‑functionalized carbon dots for signaling immuno‑reaction of carcinoembryonic antigen in an electrochemical biosensor for cancer biomarker detection Amarnath Chellachamy Anbalagan 1  · Jyoti Korram 1  · Mukesh Doble 2  · Shilpa N. Sawant 1,3 Received: 16 August 2023 / Accepted: 22 February 2024 © The Author(s) 2024 OPEN Abstract Early diagnosis of cancer demands sensitive and accurate detection of cancer biomarkers in blood. Carbon dots (CDs) bio-functionalization with antibodies, peptides or aptamers have played significant role in cancer diagnosis and tar- geted cancer therapy. Herein, a biosensor for detection of cancer biomarker carcinoembryonic antigen (CEA) in blood serum has been designed using CDs bio-functionalized with HRP-conjugated CEA antibody (CUCDs@ CEA Ab2) as detec- tion probe. CDs were synthesized by upscaling of cow urine, a nitrogen rich biomass waste, by hydrothermal method. Detection probe based on CDs resulted in 3.5 times higher sensitivity as compared to conventional electrochemical sandwich immunoassay. To further improve the sensor performance, hyper-branched polyethylenimine grafted poly amino aniline (PEI-g-PAANI) was used as the sensing interface, which enabled immobilization of higher amount of cap- ture antibody. Detection of CEA in human blood serum coupled with wide linear range (0.5–50 ng/ml), good specificity, stability, reproducibility and low detection limit (10 pg/ml) signified the excellence of CUCDs based CEA immunosensor. CUCDs exhibited excitation wavelength dependent fluorescence property and showed strong blue emission under UV irradiation. MTT assay indicated that the material is not toxic towards human dental pulp stem cells (hDPSCs) and MG63 osteosarcoma cells (cell viability > 90%). The present study demonstrates a methodology for valorization of animal waste to a cost-effective carbon based functional nanomaterial for clinical detection of cancer biomarkers. Keywords Carbon dots · Electrochemical biosensor · Cancer biomarker · Bio-conjugation · Polyaniline · Horseradish peroxidase 1 Introduction Recently cancer surpasses heart diseases as the leading cause of death worldwide [1]. Detection of cancer at the earliest stage supports the treatment significantly and increases the chance of survival of patient. Biosensors hold enormous potential for detection of critical cancer biomarkers and for determining effectiveness of anti-cancer drug during treatment. However, detection of biomarkers at low concentrations has always been a challenging task Supplementary Information The online version contains supplementary material available at https://doi.org/10.1186/s11671-024- 03980-3. * Shilpa N. Sawant, stawde@barc.gov.in | 1 Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India. 2 Department of Cariology, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Chennai 600077, India. 3 Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India.