Diagnosis of cyanide poisoning using an automated, field-portable sensor for rapid analysis of blood cyanide concentrations.

Cyanide (both HCN and CN^- are represented by CN) has multiple industrial applications, is commonly found in some foods, and is a component of fire smoke. Upon exposure, CN blocks production of adenosine triphosphate, causing cellular hypoxia and cytotoxic anoxia, which can eventually result in death. Considering CN's quick onset of action and the long analysis times associated with current techniques, the objective of this study was to develop and validate a rapid and field-portable sensor to detect blood CN concentrations focusing on both concentration and diagnostic accuracy. The sensor takes advantage of the chemical properties of CN by converting it exclusively to HCN via acidification of whole blood. High-speed headspace transfer is used to deliver HCN to a capture solution where it is reacted with naphthalene dialdehyde and taurine to produce a fluorescent β-isoindole product. Simple spectrofluorometric analysis of the product provides quantitative analysis of CN from whole blood in 60 s and requires only 25 μL of blood (obtainable via fingerstick). A limit of detection of 5 μM, a linear range of 10-200 μM (with ≥15 μM considered CN exposed), and excellent accuracy (100 ± 15%) and precision (≤15.2% relative standard deviation) were obtained. To evaluate the diagnostic accuracy of the sensor, rabbit blood samples (N = 190, including 24 blinded samples) were analyzed by both the sensor and a lab-based spectrophotometric method. An excellent positive correlation was obtained between the sensor and the lab-based method (R² ˃ 0.995) confirming the concentration accuracy of the CN sensor. Moreover, the sensor produced no false positives or negatives when diagnosing CN poisoning.