Scalable flexographic printing of graphite/carbon dot nanobiosensors for non-faradaic electrochemical quantification...

Interleukin-8 (IL-8) is a key biomarker linked to inflammation and disability in neonates. However, current IL-8 detection methods are often costly, labor-intensive, and require highly trained personnel. While electrochemical techniques have been employed for sensitive IL-8 quantification, they typically rely on redox probes and three-electrode electrochemical cells, leading to issues such as toxicity, prolonged fabrication time, and increased waste generation. Additionally, conventional electrochemical biosensors fabrication techniques are expensive and time-consuming, limiting their scalability for mass disease screening. In this study, we introduce a low-cost, non-faradaic electrochemical nanobiosensor for the direct detection of IL-8. The sensor consists of interdigitated graphite/carbon dot conjugates flexographically printed onto a flexible polyimide substrate. The printed layer's physical properties were systematically characterized using SEM, AFM and surface profilometer, and biofunctionalization was achieved using aminopropyltriethoxysilane (APTES) and glutaraldehyde. Successful surface modification was confirmed through ATR-FTIR and EDS elemental mapping. Electrochemical impedance spectroscopy (EIS) analysis demonstrated the nanobiosensor's response to varying IL-8 concentrations, with capacitance, Z_mod, Z_real, and Z_imag measurements. Among these, Z_imag exhibited the highest sensitivity, with a response of 2.7 kΩ/log(ng/mL) and a detection limit of 50 pg/mL-well below the clinically established threshold of 600 pg/mL. This study demonstrates that, in addition to capacitance, there are multiple parameters that warrant exploration in non-faradaic biosensors to improve their sensing performance. The nanobiosensor fabrication via flexographic printing enables scalable, cost-effective production while maintaining high sensitivity and selectivity through a non-faradaic detection mechanism. This work paves the way for the development of affordable, mass-producible biosensors for early biomarker detection, facilitating timely medical intervention and improved neonatal healthcare outcomes.