Fiber-Based Electrochemical Biosensors for Monitoring pH and Transient Neurometabolic Lactate

Abstract

Developing tools that are able to monitor transient neurochemical dynamics is important to decipher brain chemistry and function. Multifunctional polymer-based fibers have been recently applied to monitor and modulate neural activity. Here, we explore the potential of polymer fibers comprising six graphite-doped electrodes and two microfluidic channels within a flexible polycarbonate body as a platform for sensing pH and neurometabolic lactate. Electrodes were made into potentiometric sensors (responsive to pH) or amperometric sensors (lactate biosensors). The growth of an iridium oxide layer made the fiber electrodes responsive to pH in a physiologically relevant range. Lactate biosensors were fabricated via platinum black growth on the fiber electrode, followed by an enzyme layer, making them responsive to lactate concentration. Lactate fiber biosensors detected transient neurometabolic lactate changes in an in vivo mouse model. Lactate concentration changes were associated with spreading depolarizations, known to be detrimental to the injured brain. Induced waves were identified by a signature lactate concentration change profile and measured as having a speed of ∼2.7 mm/min ( n = 4 waves). Our work highlights the potential applications of fiber-based biosensors for direct monitoring of brain metabolites in the context of injury.

A Lab-in-a-Fiber optofluidic device using droplet microfluidics and laser-induced fluorescence for virus detection

“…Optical fibers possess a set of attributes which include flexibility, chemical and bio-inertness, easy light coupling, and a high aspect ratio. Moreover, their widespread use across numerous fields, from telecommunications to sensing 22 , 23 and imaging in medicine 24 – 27 have brought about high tolerance, and standardized production in kilometer lengths which can be assembled into low-cost optofluidic devices with precise channel dimensions using equipment developed for telecommunications production. In previous work, we demonstrated several all-fiber optofluidic devices for biomedical applications fabricated from an array of optical fibers and capillaries.…”

Significance of Flexible Substrates for Wearable and Implantable Devices: Recent Advances and Perspectives

“…For example, at the first level of developing fibers to realize sensing properties, significant research has been conducted. [ 339 ] For example, Lewis et al. fabricated soft capacitive strain sensor fibers for the determination of elongational strains for specific applications in soft robotics and human–machine interfaces.…”

“…fabricated soft capacitive strain sensor fibers for the determination of elongational strains for specific applications in soft robotics and human–machine interfaces. [ 339c ] Additionally, Anikeeva et al. reported a flexible and stretchable probe with the capacity to combine optical stimulation and electrophysiological recordings for successful implantation into mouse spinal cords.…”

Design and Evaluation of a Lactate Microbiosensor: Toward Multianalyte Monitoring of Neurometabolic Markers In Vivo in the Brain

“…Therefore, numerous studies have been carried out based on Pt:Ir (90:10) microelectrodes of cylindrical or disk geometry [17]. Alternatively, platinized carbon fiber electrodes have also been used to develop microbiosensors for in vivo monitoring [18,19].…”