PPY-fMWCNT Nanocomposite-Based Chemicapacitive Biosensor for Ultrasensitive Detection of TBI-Specific GFAP Biomarker in Human Plasma

Traumatic brain injury (TBI) is physical damage to the brain and a significant cause of mortality and morbidity affecting all ages worldwide, remaining as a diagnostic and therapeutic challenge to date. The design and development of rapid, low cost, highly accurate, and long-term stable point-of-care TBI diagnostic test kits is an unmet clinical need. In light of this, here we report a novel multianalyte chemicapacitive immunosensing platform that can detect FDA-approved Glial Fibrillary Acidic Protein (GFAP) biomarkers in real-time human plasma samples using carboxylic functionalized MWCNTs (fMWCNTs) embedded Polypyrrole (PPY) as a bioelectrical transducer. Herein, the low-cost GFAP bioelectrodes were prepared through covalent immobilization of anti-GFAP-antibodies on PPY-fMWCNTs modified array of interdigitated microelectrodes (IDµEs, fabricated on low-cost single-side copper clad PCB substrates). The binding event of GFAP peptides with anti-GFAP-antibodies in real-time human plasma samples was captured in terms of ac capacitance measured through C-F analysis (using an Agilent B1500A parametric analyzer) and quantified in terms of normalized change in capacitance of GFAP bioelectrodes with and without exposure of target GFAP peptides spiked in real-time human plasma samples (10 fg/mL – 1 µg/mL). The proposed PPY-fMWCNTs nanocomposite-based chemicapacitive immunosensing platform effectively detected GFAP target analytes in linear detection range 10 fg/mL – 10 ng/mL with a sensitivity and LoD of 3.9743 ((ΔC/C ₀ )/ng·mL ⁻¹ )/cm ² and 0.3854 fg/mL, respectively. Further, it also showed superior performance in terms of selectivity, reproducibility, long-term stability (30 weeks) and interference resistance. The proposed ac-capacitive approach is facile, label-free and can be combined with dc-resistive measurements to improve the diversity of decision-making parameters that inherently aid in improving the diagnostic accuracy of TBI test kit.