Dexamethasone-Enhanced Microdialysis and Penetration Injury

Abstract

Microdialysis probes, electrochemical microsensors, and neural prosthetics are often used for in vivo monitoring, but these are invasive devices that are implanted directly into brain tissue. Although the selectivity, sensitivity, and temporal resolution of these devices have been characterized in detail, less attention has been paid to the impact of the trauma they inflict on the tissue or the effect of any such trauma on the outcome of the measurements they are used to perform. Factors affecting brain tissue reaction to the implanted devices include: the mechanical trauma during insertion, the foreign body response, implantation method, and physical properties of the device (size, shape, and surface characteristics. Modulation of the immune response is an important step toward making these devices with reliable long-term performance. Local release of anti-inflammatory agents such as dexamethasone (DEX) are often used to mitigate the foreign body response. In this article microdialysis is used to locally deliver DEX to the surrounding brain tissue. This work discusses the immune response resulting from microdialysis probe implantation. We briefly review the principles of microdialysis and the applications of DEX with microdialysis in (i) neuronal devices, (ii) dopamine and fast scan cyclic voltammetry, (iii) the attenuation of microglial cells, (iv) macrophage polarization states, and (v) spreading depolarizations. The difficulties and complexities in these applications are herein discussed.

Establishment of a pharmacokinetics and pharmacodynamics model of Schisandra lignans against hippocampal neurotransmitters in AD rats based on microdi-alysis liquid chromatography-mass spectrometry

“…These substances are then transported with the perfusate to a sample collector. Due to the probe’s small size and molecular weight ( Jaquins-Gerstl and Michael, 2020 ), this method causes minimal trauma to the subject, and collected samples can be directly subjected to mass spectrometry analysis without prior treatment ( Hou et al, 2022 ). Another advantageous feature of MD is its ability to enable continuous sampling from the same experimental animal ( O'Connell and Krejci, 2022 ).…”

Electroosmotic Perfusion, External Microdialysis: Simulation and Experiment

“…Thus, only very slow reactions are accessible with these devices. In addition, the diameter of these devices at ∼350 μm inhibits application to small brain regions and creates significant insertion trauma. − Iontophoresis has been used sparingly for analogous work. Qualitative evaluation of peptide hydrolysis following iontophoretic delivery into skin has been investigated for Tyr-Phe, LHRH, and delta sleep-inducing peptide .…”

Simultaneous Presentation of Dexamethasone and Nerve Growth Factor via Layered Carbon Nanotubes and Polypyrrole to Interface Neural Cells

“…Various strategies have been developed to improve the long-term and high-performance neural signal recording/stimulation, such as using soft electrode materials, surface coating with conductive polymers, local release or presentation of anti-inflammatory drugs, or neural growth promoted biomolecules. − Studies indicated that controlling the inflammatory reactions at the electrode sites or stimulating the growth of neural cells and extension of neurites are key points for the maintenance of electrode functions. , The acute and chronic inflammatory response is a key factor accounting for the failure of neural electrodes in long-term functionalization, and the inflammatory response could be modulated via the administration of anti-inflammatory drugs . Dexamethasone (Dex), a synthetic glucocorticoid, is associated with diminished migration and activation of immune cells, upregulation of anti-inflammatory cytokines, and decreased collagen production at the implant site. − Dex has been locally delivered to the microelectrode implanted sites via integrated microfluidic channels, conductive polymer controlled release, or hydrogel transportation, leading to a significantly decreased number of reactive astrocytes and reduced foreign body reactions. , However, the fabrication of microfluidic channels adds to the complexity in electrode fabrication; a limited amount of Dex could be delivered via the conductive polymer copolymerization, and the expansion of nonconductive hydrogels adds to the distance between neurons and neural electrodes. Besides, stimulating the regrowth of neural cells and attracting neurites to the active electrode sites by local presentation of biomolecules, such as NGF, from/on the electrode is another useful way to improve the recording/stimulation performance. , Incorporation of NGF as a codopant in conducting polymers has been demonstrated as an alternative way to locally deliver nerve-protective biomolecules .…”

“…16−18 Dex has been locally delivered to the microelectrode implanted sites via integrated microfluidic channels, conductive polymer controlled release, or hydrogel transportation, leading to a significantly decreased number of reactive astrocytes and reduced foreign body reactions. 15,17 However, the fabrication of microfluidic channels adds to the complexity in electrode fabrication; a limited amount of Dex could be delivered via the conductive polymer copolymerization, and the expansion of nonconductive hydrogels adds to the distance between neurons and neural electrodes. Besides, stimulating the regrowth of neural cells and attracting neurites to the active electrode sites by local presentation of biomolecules, such as NGF, from/on the electrode is another useful way to improve the recording/stimulation performance.…”