Ultraefficient electrochemical biosensing platform utilizing aloe vera-derived carbon nanodots for ANXA2 liver cancer biomarker diagnosis

The synthesis of nanomaterials from natural resources offers a cost-effective and environmentally sustainable approach for biosensor development. In this study, carbon nanodot (CND)-based electrochemical biosensor has been developed for the early diagnosis of liver cancer (LC) biomarker i.e. ANXA2. Initially, Aloe vera has been chosen as the carbon precursor for the synthesis of CNDs. The synthesis of carbon nanodots began with the extraction of Aloe vera gel, which has been mixed with ultrapure water and subjected to hydrothermal processing at 180 °C for 12 h. Then the obtained product has been filtered through 0.22 µm polytetrafluoroethylene (PTFE) membrane, washed with dichloromethane and stored at 4 °C. The size of synthesized CNDs has been obtained as ∼5.6 nm. Further, the prepared CNDs have been electrophoretically deposited onto hydrolysed indium tin oxide (ITO)-coated glass electrodes under an optimized potential of 10 V for 60 s at 300 mA. Further, the obtained thin film of CNDs onto the ITO electrode has been used to immobilize anti-ANXA2 via drop casting method and bovine serum albumin (BSA) has been used for the blocking of non-specific binding sites. The morphological, structural and electrochemical properties of the synthesized CNDs and the fabricated electrodes have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), attenuated total reflectance (ATR), UV-Vis spectroscopy and cyclic voltammetry (CV) techniques. Further the fabricated BSA/anti-ANXA2/CND/ITO biosensing platform has been used to investigate the ANXA2 biomarker via CV technique and the obtained results indicate the fabricated platform shows liner detection range in between 1 fg mL⁻¹ to 10 ng mL⁻¹ and 10–500 ng mL⁻¹, sensitivities 1.36 µA [log (ng mL⁻¹)]⁻¹ cm⁻² and 6.84 µA [log (ng mL⁻¹)]⁻¹ cm⁻² respectively with response time of 20 min. Notably, the biosensor demonstrated excellent selectivity with minimal interference from common biological analytes present in the serum sample of liver cancer patients with highly reproducible in nature.