An electrochemical biosensor for hypoxanthine detection in vitreous humor: A potential tool for estimating the post-mortem interval in forensic cases

In this study, a simple electrochemical method was developed for fast and convenient detection of hypoxanthine (Hx) and subsequent estimation of the post-mortem interval (PMI) in forensic cases. A polydopamine-modified carbon nanofibers (CNFs) electrode was utilized with xanthine oxidase (XOD) for Hx detection in vitreous humor (VH) samples for the first time. Fourier transform infrared (FT-IR) spectra and electrochemical characterization revealed the PDA-coated CNFs exhibited good biocompatibility for XOD immobilization and fast electron transfer. Under the optimal conditions, acceptable stability and reproducibility of the assay were achieved. Additionally, this enzymatic electrochemical biosensor showed a good linear relationship between the current response and Hx concentrations in the range of 5 - 60 mu M and a detection limit of 2 mu M. Consequently, the possible interferences in VH samples were studied to verify the selectivity of this device, and the findings confirmed the excellent detection specificity of this assay for the analysis of real samples. Moreover, the recycling experiments conducted in VH samples showed the practical application of this microdevice. In addition, the analysis of Hx concentration allowed for accurate PMI prediction, compared with known PMI values. These results indicated that the Hx biosensor may be a promising tool for the estimation of PMI in forensic investigations.