(265a) Integrated Biosensor for Rapid and Point-of-Care Sepsis Diagnosis

Purpose: Sepsis is an often fatal condition that arises when the immune response to an infection causes widespread systemic organ injury. A critical unmet need in combating sepsis is the lack of accurate early biomarkers that produce actionable results in busy clinical settings. Here, we report the development of a point-of-care platform for rapid sepsis detection. Termed IBS (integrated biosensor for sepsis), our approach leverages i) the newly-found pathophysiological role of cytokine interleukin-3 (IL-3) in early sepsis, and ii) a hybrid magneto-electrochemical sensor for IL-3 detection.

Materials & Methods: Assay. The IBS assay starts by extracting the target protein IL-3 through immunomagnetic enrichment. The captured protein is then subsequently labeled with detection antibodies and oxidizing enzyme (horseradish peroxidase, HRP). Finally, the beads are mixed with chromogenic electron mediators (3,3′,5,5′-tetramethylbenzidine, TMB); the enzyme catalyzes the oxidation of TMB and the reduction of H₂O₂. The oxidized TMB is then reduced by receiving electrons from the electrode, which generates electrical current as an analytical read out. Using magnetic beads allowed for direct and fast extraction of IL-3 from blood samples. Signal can also be amplified by concentrating magnetic beads underneath the electrodes. Clinical study. We applied IBS to detect IL-3 in clinical samples. Plasma or serum samples were collected from patients with symptoms of systemic infection, inflammation, or both. We obtained 23 samples from septic patients and another 39 from non-septic patients.

Results: The magneto-electrochemical sensing strategy developed here enables POC diagnostics: i) magnetic beads provides large surface area (~230 mm²) for target capture and an easy way to perform assay steps; ii) the analytical signal is read out by compact, rugged electronics. Applying the IBS prototype, we achieved rapid (<1 hr), highly sensitive (<10 pg/mL) IL-3 detection in human plasma samples. Whole blood can also be used without preprocessing, which would better position the assay into most clinical workflows. The pilot clinical study supported the potential of IL-3 as a surrogate biomarker of sepsis: the sensitivity was 91.3%, and the specificity 82.4%. In comparison, procalcitonin (PCT) has been shown to have accuracies below 80%. Because IBS is fast and consumes small amount of samples (100 µL), it can be readily adopted to track temporal changes of biomarkers. This capacity would aid in not only the timely diagnosis of acute septic shock, but also reliable prognostication assessment of the risk. Also, using the small amount of samples would be especially advantageous for detection of sepsis in new borns/infants as blood samples from preterm infants (with a blood volume of <50 mL) are limited in volume.

Conclusion: The developed platform produces test results within 1 hour from native blood samples, and detects IL-3 at a sensitivity of <10 pg/mL; this performance is >5-times faster and >10-times more sensitive than a current gold standard, enzyme-linked immunoadsorbent assay. Using clinical samples, we show that high plasma IL-3 levels are associated with high organ failure rate and thus greater risk of mortality, confirming the potential of IL-3 as an early diagnostic biomarker. Compact and fast, the IBS platform can be readily integrated into clinical workflows, enabling timely diagnosis and proactive treatment of sepsis.