Abstract
Biosensors with high sensitivity and short time-to-result that are capable of detecting biomarkers in body fluids such as serum are an important prerequisite for early diagnostics in modern healthcare provision. Here, we report the development of an electrochemical impedance-based sensor for the detection in serum of human interleukin-8 (IL-8), a pro-angiogenic chemokine implicated in a wide range of inflammatory diseases. The sensor employs a small and robust synthetic non-antibody capture protein based on a cystatin scaffold that displays high affinity for human IL-8 with a KD of 35±10nM and excellent ligand specificity. The change in the phase of the electrochemical impedance from the serum baseline, ∆θ(ƒ), measured at 0.1Hz, was used as the measure for quantifying IL-8 concentration in the fluid. Optimal sensor signal was observed after 15min incubation, and the sensor exhibited a linear response versus logarithm of IL-8 concentration from 900fg/ml to 900ng/ml. A detection limit of around 90fg/ml, which is significantly lower than the basal clinical levels of 5–10pg/ml, was observed. Our results are significant for the development of point-of-care and early diagnostics where high sensitivity and short time-to-results are essential.
Highlights
IntroductionThe ability to detect biomarkers in body fluids at the point of care with high sensitivity and short time-to-result is becoming critical in a society placing increasing importance on both disease prevention, early diagnostics, and on stratified and individualised patient care
Modern healthcare systems rely heavily on in vitro diagnostics
The binding protein showing the strongest affinity to IL-8 was chosen as the capture molecule for the Electrochemical impedance spectroscopy (EIS) biosensor
Summary
The ability to detect biomarkers in body fluids at the point of care with high sensitivity and short time-to-result is becoming critical in a society placing increasing importance on both disease prevention, early diagnostics, and on stratified and individualised patient care. During an injury or infection IL-8 is involved in the recruitment of neutrophils from blood vessels to the affected tissue (Hammond et al, 1995) promoting angiogenesis (Li et al, 2003) Stimulants such as pro-inflammatory cytokines (e.g. TNF-α and interleukin-1), cellular stress, or bacterial and viral products, trigger cells to express IL-8 proteins The ability to monitor IL-8 concentrations with high accuracy in body fluids, e.g. serum, is an important prerequisite to enable early and accurate detection of severe illnesses, some of which result in progressive deterioration and consequent mortality
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