As awareness of traumatic brain injury (TBI) increases, the need to detect mild forms and distinguish between the different severities of TBI becomes more apparent. The goal of this work is to develop a point-of-care sensor to detect whole blood biomarkers for rapid and sensitive diagnosis of TBI severity. Presented herein is the enzymatic detection of norepinephrine through the use of immobilization chemistry and impedance techniques. Sustained elevation of norepinephrine concentrations in the blood has been correlated to negative long-term outcomes in TBI cases, often resulting in permanent cognitive or physical deficits.

Novel analysis techniques have been used to identify an optimal binding frequency (371.1 Hz) of norepinephrine to the immobilized enzyme on a gold disk electrode. This form of analysis yielded a logarithmic fit characterized by exceptional responsivity (20.89 Ω/pgmL^-1), reproducibility (R² = 0.96), and lower limit of detection (98 pg/mL) first in purified samples, then in rabbit whole blood solutions. Once the optimal binding frequency was determined, the preliminary use of an impedance-time technique was attempted in this work. This technique more closely resembles the amperometric detection method used in commercial self-monitoring blood glucose meters, allowing for continuous or instantaneous measurement of blood borne biomarkers without compromising sensitivity. Future directions include exploration of simultaneous multi-marker detection with the impedance-time technique and experimentation with novel mesoporous materials to filter large blood components.

There is a critical need for more accurate, highly sensitive and specific assay for disease diagnosis and management. A novel, multiplexed, single sensor using rapid and label free electrochemical impedance spectroscopy tuning method has been developed. The key challenges while monitoring multiple targets is frequency overlap. Here we describe the methods to circumvent the overlap, tune by use of nanopartide (NP) and discuss the various fabrication and characterization methods to develop this technique. First sensors were fabricated using printed circuit board (PCB) technology and nickel and gold layers were electrodeposited onto the PCB sensors. An off-chip conjugation of gold NP's to molecular recognition elements (with verification technique) is described as well. A standard covalent immobilization of the molecular recognition elements is also discussed with quality control techniques. Finally use and verification of sensitivity and specificity is also presented. By use of gold NP's of various sizes, we have demonstrated the possibility and shown little loss of sensitivity and specificity in the molecular recognition of inflammatory markers as "model" targets for our tuning system. By selection of other sized NP's or NP's of various materials, the tuning effect can be further exploited. The novel platform technology developed could be utilized in critical care, clinical management and at home health and disease management.