The Development of Aptamer-Coupled Microelectrode Fiber Sensors (apta-µFS) for Highly Selective Neurochemical Sensing.

The selective and sensitive sensing of neurochemicals is essential to decipher in-brain chemistry underlying brain pathophysiology. The recent development of flexible and multifunctional polymer-based fibers has been shown useful in recording and modulating neural activities, primarily electrical ones. In this study, we were able to realize fiber-based neurochemical sensing with high sensitivity and selectivity. We achieved a generalizable method to couple aptamers, a type of synthetic receptors on the carbon composites within fibers, as microsensors for highly selective neurochemical detection. Such an aptamer-coupled microelectrode fiber sensor (apta-µFS) enables simple, label-free, and sensitive dopamine (DA) detection down to 5 nM with ultrahigh specificity across major interferents. We succeeded in monitoring DA selectively within the living brain using our apta-µFS. We further showed the proof-of-concept of using microelectronic fiber-based toolsets to target neural pathways across electrical and chemical modalities. In summary, such fiber-based toolsets hold great potential to advance multimodal mechanistic understanding of brain pathophysiology.

Thermally Drawn CNT-Based Hybrid Nanocomposite Fiber for Electrochemical Sensing.

Nowadays, bioelectronic devices are evolving from rigid to flexible materials and substrates, among which thermally-drawn-fiber-based bioelectronics represent promising technologies thanks to their inherent flexibility and seamless integration of multi-functionalities. However, electrochemical sensing within fibers remains a poorly explored area, as it imposes new demands for material properties-both the electrochemical sensitivity and the thermomechanical compatibility with the fiber drawing process. Here, we designed and fabricated microelectrode fibers made of carbon nanotube (CNT)-based hybrid nanocomposites and further evaluated their detailed electrochemical sensing performances. Carbon-black-impregnated polyethylene (CB-CPE) was chosen as the base material, into which CNT was loaded homogeneously in a concentration range of 3.8 to 10 wt%. First, electrical impedance characterization of CNT nanocomposites showed a remarkable decrease of the resistance with the increase in CNT loading ratio, suggesting that CNTs notably increased the effective electrical current pathways inside the composites. In addition, the proof-of-principle performance of fiber-based microelectrodes was characterized for the detection of ferrocenemethanol (FcMeOH) and dopamine (DA), exhibiting an ultra-high sensitivity. Additionally, we further examined the long-term stability of such composite-based electrode in exposure to the aqueous environment, mimicking the in vivo or in vitro settings. Later, we functionalized the surface of the microelectrode fiber with ion-sensitive membranes (ISM) for the selective sensing of Na+ ions. The miniature fiber-based electrochemical sensor developed here holds great potential for standalone point-of-care sensing applications. In the future, taking full advantage of the thermal drawing process, the electrical, optical, chemical, and electrochemical modalities can be all integrated together within a thin strand of fiber. This single fiber can be useful for fundamental multi-mechanistic studies for biological applications and the weaved fibers can be further applied for daily health monitoring as functional textiles.