Sensitive detection of heart-failure biomarkers natriuretic peptides using multi-photon laser wave-mixing spectroscopy.

Nonlinear laser wave-mixing spectroscopy is demonstrated as a fast and sensitive detection method for heart-failure biomarkers, pro-atrial natriuretic peptide (proANP) and brain natriuretic peptide (BNP). Wave mixing is an ultrasensitive optical absorption-based method and analytes can be detected in their native form or labeled with fluorophore and chromophore labels. In this study, we utilized Chromeo P540 dye to label the peptides for wave-mixing detection. The wave-mixing signal is created from the diffraction of incoming photons by the thermal grating at the capillary analyte cell. The signal beam is strong, collimated, and coherent (laser-like) and it is collected using a simple photodetector with an excellent signal-to-noise ratio. We demonstrated advantages of this technique over conventional assays including shorter analysis times, smaller sample requirements, and higher throughput. To enhance detection selectivity and sensitivity levels, wave mixing is effectively coupled to capillary zone electrophoresis (CZE) and field-amplified sample stacking (FASS) methods. We determined detection limits of 7.4 × 10 M or 55 zmol and 6.8 × 10 M or 51 zmol for proANP and BNP, respectively, and separated and detected both peptides within 2 min. Due to the challenges in the confirmatory diagnoses of heart failure, wave-mixing serves as a potentially beneficial screening tool in addition to the commonly used echocardiographic tests.