Ultrasensitive label-free detection of cardiac biomarker myoglobin based on surface-enhanced Raman spectroscopy

Acute myocardial infarction (AMI) is the leading cause of mortality worldwide. Myoglobin protein was used as a biomarker for AMI because of its higher sensitivity compared with other biomarkers. Its high sensitivity is attributed to its rapid release in the bloodstream. As such, many researchers have focused on developing label-free biosensors to detect myoglobin levels. This study developed a highly sensitive and label-free myoglobin sensor based on surface-enhanced Raman spectroscopy (SERS). The sensor consisted of new 3D silver anisotropic nano-pinetree array modified indium tin oxide (Ag NPT/ITO) substrates. Moreover, another three Ag nanostructure modified ITO substrates (nanoaggregates, nanorods and nanobranched) were developed to select the highest surface enhanced Raman spectroscopy. Results revealed that Ag NPT/ITO displayed the highest SERS performance compared with other substrates. This finding is attributed to the presence of numerous hotspots, particularly in the junctions between the central rod and side arms. The highly enhanced Raman effect of Ag NPT/ITO substrate was applied to develop an ultrasensitive biosensor for detecting myoglobin as a cardiac biomarker at low concentration levels in solutions (pH 7.4, phosphate buffer) and urine. This biosensor is potentially useful for real sample analysis. The 3D morphology of Ag NPT enhanced the sensitivity performance of the sensor and allowed myoglobin detection over a wide linear range with a detection limit of 10 ng/mL.