Estimation of postmortem interval by vitreous potassium evaluation with a novel fluorescence aptasensor

Estimation of postmortem interval (PMI) is a central role in medico-legal identification. Analysis of vitreous potassium ions (K(+)) concentration is frequently used by forensic workers to estimate PMI. This paper describes interdisciplinary research to introduce fluorescence sensing techniques into forensic medicine. On the basis of silver nanoclusters (AgNCs) probe stabilized by DNA, a simple and highly sensitive fluorescence aptasensor has been proposed to selectively detect K(+) ions. The linear range for K(+) ions was found to be 0.1 nM-1 mM, with limit of detection of 0.06 nM. Moreover, 63 vitreous humour cases within 36 h after death were further studied to verify the utility of K(+) ions in estimating the PMI. By the fluorescence aptasensor method, a new formula was built to determine the postmortem interval based on K(+) ions concentration: PMI(h) = −0.55 + 1.66 × C(K) (+)(r = 0.791). And the real significance of this research was demonstrated by additional 6 cases with known PMIs. In comparison with the conventional method, the presented aptasensor strategy is cost-effective and easy in measuring vitreous K(+), which may be potentially a better way for estimation of PMI in medico-legal practice.