A Raman immunosensor based on SERS and microfluidic chip for all-fiber detection of brain natriuretic peptide

Early diagnosis of chronic heart failure (CHF) relies on the ultra-sensitive detection assay of its main biomarker, Brain natriuretic peptide (BNP). To meet such demand, we designed a near-infrared immunoassay biosensor, utilizing a fiber-embedded microfluidic chip for surface-enhanced Raman scattering (SERS) detection. A SERS probe, consisting of metal–organic framework and Au-HEPES coupling nanoparticles (AuHPs), was used to enhance the Raman signal of the toluidine blue (TB) dye. The probe anchored with TB is used as a SERS tag, which is linked to BNP through sandwich method. To enhance the Raman signal further, we embedded a SERS substrate at the bottom of the microfluidic channel, which serves an enhancer when the SERS tagged BNP passes through the microfluidic chip. The amplified Raman signal was collected by an optical fiber probe of a simple and portable Raman detection system with an all-fiber connected configuration. Such design resulted in the lowest detection limit of pg/mL, indicating that the proposed platform can be used for rapid and highly sensitive detection of BNP. In addition, our platform also has the advantages of low sample consumption and high throughput rate, providing an effective scheme for the early diagnosis of CHF.