Plasmon-enhanced near-infrared fluorescence detection of traumatic brain injury biomarker glial fibrillary acidic protein in blood plasma.

An ultrasensitive plasmonic near-infrared fluorescent biosensor substrate has been developed for detection of glial fibrillary acidic protein (GFAP) biomarker in blood plasma, an important protein biomarker of traumatic brain injury (TBI). To minimize the interference from blood plasma sample matrix, a near-infrared fluorophore in the first biological transparency window is used in the biosensor. To amplify the fluorescence signals, a plasmonic gold nanopyramid array has been coupled to the fluorophore. Finite-difference time-domain simulation reveals that the excitation enhancement is primarily responsible for the fluorescence enhancement owing to the intense local electric field excited on the corners and edges. As a result, this biosensor exhibits a lower limit of detection of 0.6 pg/mL toward detection of GFAP in blood plasma.