Towards heart failure biomarker detection with plasmonic fiber tip biosensors

Heart failure (HF) with reduced fraction ejection is an entity of multifactorial causes and currently is considered the most imitating cardiovascular disease in terms of survival prognosis and life quality, whose incidence is expected to increase worldwide in the following decade. The N-terminal portion of B-type natriuretic peptide (NT-proBNP) is deemed the gold standard HF biomarker, it is the earliest and sensible marker of cardiac suffering, being used for risk stratification and diagnosis. This project aimed to develop an immunosensor based on a plasmonic exposed core optical fiber tip for the rapid and label-free detection of NT-proBNP. This biosensor was uncladded on the fiber tip and sputtered with a gold nanofilm, enabling both the reflection of light and the excitation of the surface plasmon resonance (SPR) effect. A characterization to the refractive index was performed, reaching an average sensitivity of 2091.8 +/- 125.4 nm/RIU, prior to the functionalization of the fiber surface using anti-NT-proBNP antibodies through cysteamine. The complete biofunctionalization step caused a redshift of the SPR wavelength of 7.6 nm. In the detection test, the biosensor was capable of monitoring NT-proBNP increasing concentrations, from 0.01 to 100 ng/mL, with a total redshift of 6.2 nm. This resulted in a sensitivity of 1.61 +/- 0.14 nm/log(ng.mL(-1)) in a concentration range of clinical interest for HF monitoring. The presented preliminary work exhibited promising results aiming a user-friendly solution that can be used at point of care to test NT-proBNP levels in physiological fluids.