Carbon dots-modified chitosan based electrochemical biosensing platform for detection of vitamin D

Here in, a carbon dots (CDs)-modified chitosan (CH) based biosensing platform was fabricated for vitamin D₂ detection. Carbon dots were synthesized through microwave pyrolysis method, and characterized with transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV/VIS spectroscopy. Chitosan (1%) solution was prepared in acetic acid (1%) solution and followed by the addition of CDs to prepare the carbon dots-chitosan (CD-CH) composite. A thin film of CD-CH composite was prepared onto ITO glass substrate (CD-CH/ITO) by drop casting method. Surface of the composite film was characterized by atomic force microscopy, static contact angle measurement and cyclic voltammetry. CD-CH/ITO surface was further modified with immobilization of vitamin D₂ antibody (Ab-VD₂) and bovine serum albumin (BSA) to prepare BSA/Ab-VD₂/CD-CH/ITO bioelectrode. Electrochemical response of the bioelectrode towards vitamin D₂ antigen (Ag-VD₂) was carried out by differential pulse voltammetry. The biosensing electrode showed linearity within the range 10-50 ng mL^-1 of Ag-VD₂ concentration. The sensitivity was found to be 0.2 μA ng^-1 mL cm^-2, LOD was 1.35 ng mL^-1, and the biosensor had a shelf-life of about 25 days.