Echem methods and electrode types of the current in vivo electrochemical sensing

In-vitro sensing of traumatic brain tissue by electrochemical impedance for diagnosis and therapeutic

Traumatic brain injury (TBI) induces neurogenerative disorders affecting severely daily human activities and early diagnosis is a critical requirement for prevention and cure. Here, we induced TBI formation in the Zebra fish, a model organism, by both mechanical (ultrasonic cleaner generated convulsive shock, UGCS) and chemical (pentylenetetrazol, PTZ) methods. The TBI induced cellular and neuronal changes are monitored by measuring the activities of the indicator biomarkers viz., superoxide anion (O2-) and glutamate by electrochemical techniques. For this, the α-lipoic acid (α-LA, LA) functionalized gold-silver (LA-Au/Ag) is used as an electrochemical sensor to diagnose the presence of these markers in physiological phosphate buffer saline (PBS, pH 7.4), 0.1 M KCl solutions and in TBI tissues. While the oxidation of glutamate is observed in the potential window 0.2-0.5 V, the metal mediated oxidation of O2- is observed at the potential window 0.6-1.0 V. The sensor showed good linear ranges for O2- (from 4 to 48 μM with the LOD of 4 μM for the O2- detection) and glutamate (from 20 to 130 μM with the LOD 19 μM). The TBI tissue modified electrode showed lower resistance than the normal brain tissue ((NBT), as control) due to the presence of higher amount of O2- and occurrence of Fenton's and Heber-Weise's reactions in the presence of [Fe(CN)6]3-/4-. For theragnostic application, the LA-Au/Ag nanoparticles is delivered into the UGCS and PTZ treated Zebrafish and electrochemical signal changes are monitored by cyclic voltammetry and impedance spectroscopy. Electrochemical data further corroborated with the activities of superoxide dismutase (SOD), Catalase (CAT) and lipid peroxidase (MDA) in parallel. The developed method of electrochemical sensing of TBI may provide alternative for the early TBI diagnosis and therapeutics for the prevention of TBI.

Clinical challenges and opportunities related to the biological responses experienced by indwelling and implantable bioelectronic medical devices

Implantable electrodes have been utilized for decades to stimulate, sense, or monitor a broad range of biological processes, with examples ranging from glucose monitoring devices to cochlear implants. While the underlying science related to the application of electrodes is a mature field, preclinical and clinical studies have demonstrated that there are still significant challenges in vivo associated with a lack of control over tissue-material interfacial interactions, especially over longer time frames. Herein we discuss the current challenges and opportunities for implantable electrodes and the associated bioelectronic interfaces across the clinical landscape with a focus on emerging technologies and the obstacles of biofouling, microbial colonization, and the foreign body response. Overcoming these challenges is predicted to open the door for a new generation of implantable medical devices and significant associated clinical impact. STATEMENT OF SIGNIFICANCE: Implantable electrodes have been utilised for decades to stimulate, sense, or monitor a broad range of biological processes, with examples ranging from glucose monitoring devices to cochlear implants. Next-generation bioelectronic implantable medical devices promise an explosion of new applications that have until this point in time been impossible to achieve. However, there are several persistent biological challenges hindering the realisation of these new applications. We present a clinical perspective on how these biological challenges have shaped the device market and clinical trial landscape. Specifically, we present statistical breakdowns of current device applications and discuss biofouling, the foreign body response, and microbial colonisation as the main factors that need to be addressed before a new generation of devices can be explored.

Advancements in Brain Research: The In Vivo/In Vitro Electrochemical Detection of Neurochemicals

Neurochemicals, crucial for nervous system function, influence vital bodily processes and their fluctuations are linked to neurodegenerative diseases and mental health conditions. Monitoring these compounds is pivotal, yet the intricate nature of the central nervous system poses challenges. Researchers have devised methods, notably electrochemical sensing with micro-nanoscale electrodes, offering high-resolution monitoring despite low concentrations and rapid changes. Implantable sensors enable precise detection in brain tissues with minimal damage, while microdialysis-coupled platforms allow in vivo sampling and subsequent in vitro analysis, addressing the selectivity issues seen in other methods. While lacking temporal resolution, techniques like HPLC and CE complement electrochemical sensing's selectivity, particularly for structurally similar neurochemicals. This review covers essential neurochemicals and explores miniaturized electrochemical sensors for brain analysis, emphasizing microdialysis integration. It discusses the pros and cons of these techniques, forecasting electrochemical sensing's future in neuroscience research. Overall, this comprehensive review outlines the evolution, strengths, and potential applications of electrochemical sensing in the study of neurochemicals, offering insights into future advancements in the field.