Despite warnings from the scientific community about the possibility of a forthcoming global pandemic, few people believed that a virus could sweep across the planet and kill millions of people in just 1.5 years, as COVID-19 did in 2019-2020. The vast gaps revealed in COVID-19 diagnostics can and should teach us how to better prepare for yet another imminent global threat: antibiotic resistance. The current paradigm for bacterial infection treatments involves an empirical treatment along with a sample culture for bacterial identification and antibiotic susceptibility testing which may take up to 72 hours. While this empirical treatment may treat bacterial infections, a considerable risk of overtreatment or undertreatment exists, which is a perfect recipe for developing antibiotic resistance. Considering these diagnostic challenges, the development of point-of-care platforms should be prioritized to ensure that patients receive the most effective treatment possible.Electrochemical biosensors are ideal for point-of-care (POC) applications because they are compact and cost-effective. While interdigitated electrode arrays (IDEAs) were developed over 60 years ago, high aspect-ratio carbon interdigitated electrode arrays (C-IDEA) have become an attractive solution for biosensing because they offer higher levels of redox amplification at a lower cost compared to their noble metals counterparts. carbon-based electrochemical biosensors also enable a variety of electrochemical techniques as well as surface chemistries which give scientists the freedom to develop suitable assays.
In this study, the characteristic dimensions of microbands (width, gap, and height) are optimized by numerical analysis and validated experimentally. Flow injection analysis (FIA) data show that flow enhances current density but suppresses redox cycling. Higher width to gap ratio and greater microband height result in higher current density. Since current density is linearly proportional to the microband height in the stationary mode, increasing the microband height is the best strategy to improve both current density and redox amplification.
Additionally, pyrolysis parameters are optimized to achieve a high yield of high aspect-ratio electrodes. The width to height ratio of the microbands and nitrogen flow rate inside the furnace are identified as the main contributing factors. When microband width is less than the microband height the shrinkage is lateral which results in high aspect-ratio microbands. A laminar flow regime with a Reynold number of 1 is ideal for reducing the chip-to-chip variations.
Finally, we demonstrated the capacity of C-IDEAs as a potential platform for POC applications by detecting DNA at femtomolar concentrations. This is an impressive limit of detection (LOD) as it allows the detection of biomarkers at the early stages of infection. These results are also achieved by using a portable instrument and affordable sensors (under $1 fabrication cost), which are essential for the global deployment of POC systems.