Novel microwire-based biosensor probe for simultaneous real-time measurement of glutamate and GABA dynamics in vitro and in vivo

Abstract

Glutamate (GLU) and γ-aminobutyric acid (GABA) are the major excitatory (E) and inhibitory (I) neurotransmitters in the brain, respectively. Dysregulation of the E/I ratio is associated with numerous neurological disorders. enzyme-based microelectrode array biosensors present the potential for improved biocompatibility, localized sample volumes, and much faster sampling rates over existing measurement methods. However, enzymes degrade over time. To overcome the time limitation of permanently implanted microbiosensors, we created a microwire-based biosensor that can be periodically inserted into a permanently implanted cannula. Biosensor coatings were based on our previously developed GLU and reagent-free GABA shank-type biosensor. In addition, the microwire biosensors were in the same geometric plane for the improved acquisition of signals in planar tissue including rodent brain slices, cultured cells, and brain regions with laminar structure. We measured real-time dynamics of GLU and GABA in rat hippocampal slices and observed a significant, nonlinear shift in the E/I ratio from excitatory to inhibitory dominance as electrical stimulation frequency increased from 10 to 140 Hz, suggesting that GABA release is a component of a homeostatic mechanism in the hippocampus to prevent excitotoxic damage. Additionally, we recorded from a freely moving rat over fourteen weeks, inserting fresh biosensors each time, thus demonstrating that the microwire biosensor overcomes the time limitation of permanently implanted biosensors and that the biosensors detect relevant changes in GLU and GABA levels that are consistent with various behaviors. Near real-time measurement of neurotransmitter levels in the brain is expected to reveal important clues to the underlying mechanisms of neurological disorders, such as epilepsy, addiction, motor control 1-3 , and secondary damage after stroke 4 and traumatic brain injury 5,6. Two important and ubiquitous neurotransmitters in the brain are l-glutamine (GLU) and γ-aminobutyric acid (GABA), which are the major excitatory and inhibitory neurotransmitters, respectively. A balance of excitatory (E) and inhibitory (I) electrical signaling in local networks (E/I ratio) is observed in awake states and in sleep, with the exception of slow-wave sleep in humans and monkeys 7. Dysregulation in E/I is closely linked to dysregulation of GLU and/or GABA dynamics 8. Prolonged, excessive GLU release often leads to excitotoxic neuronal cell death directly or through a cascade of secondary cellular injury 9,10. Furthermore, insufficient release of GABA is associated with seizures 6,11 and autism 12. Most studies so far have only looked at GLU and GABA in isolation 13,14. However, a more meaningful interpretation of the mechanisms of disease and secondary injury can be obtained by knowing the regional E/I balance 15. Furthermore,

A Pencil-Lead Immunosensor for the Rapid Electrochemical Measurement of Anti-Diphtheria Toxin Antibodies

“…The parameters employed in the equation were: the number of electrons ( n = 1), Faraday constant (F = 96,485 C mol L −1 ), the concentration of [Fe(CN) 6 ] 4− = 5 × 10 −6 mol cm −3 , and the average diffusion coefficient value of the [Fe(CN) 6 ] 4− in 0.1 mol L −1 KCl = 5.38 × 10 −6 cm 2 s −1 [ 41 ]. The one-way ANOVA test was performed ( n = 3) with significance defined as p < 0.05 to check whether the device-to-device surface variation during the optimization of fabrication or analytical parameters—e.g., type of PLE, biEP and sec-IgG concentrations, serum dilution ratio, and time of exposition—was significant, as done in studies found in the literature [ 42 , 43 ]. Then, a two-tailed Students t -test with a confidence level of 95% was performed for pairwise comparisons.…”

“…Then, a two-tailed Students t -test with a confidence level of 95% was performed for pairwise comparisons. [ 42 , 43 ].…”

Farelerde Pentilentetrazol ile Oluşturulan Epileptik Nöbetler Üzerine Anakinra’nın Etkisinin Araştırılması

“…Eksitatör ve inhibitör ana nörotransmitterler arasındaki denge normal bir beyin fonksiyonu için elzemken, GABA/Glutamat imbalansı epilepsiyle yakından ilişkilidir. [22][23] PTZ enjeksiyonları sonrası hipokampusta GABA konsantrasyonunun azalmış olması literatürle uyumludur. [24][25] PTZ'nin beyinde GABA ve Glutamat konsantrasyonları üzerindeki etkisini, bu nörotransmitterlerin metabolizmasında yer alan glutamat dehidrogenaz ve GABA aminotransferaz gibi enzimlerin aktivitelerini etkileyerek gerçekleştirdiği ileri sürülmektedir.…”

Biomaterials-based strategies for in vitro neural models

“…This approach has proven useful for measuring neurotransmitter levels within in vitro neural models 261 and monitoring neural differentiation of stem cells. 262…”