Understanding the Inflammatory Tissue Reaction to Brain Implants To Improve Neurochemical Sensing Performance

Neurochemical sensing probes are a valuable diagnostic and therapeutic tool that can be used to study neurodegenerative diseases involving deficiencies in neurotransmitter signaling. However, implantation of these biosensors can elicit a harmful tissue response that alters the neurochemical environment within the brain. Transmission of chemical messengers via neurons is impeded by a barrier-forming glial scar that occurs within weeks after insertion followed by progressive neurodegeneration, attenuating signal sensitivity. Emerging research reveals that non-neuronal cells also influence the neurochemical milieu following injury both directly and indirectly. The reactivity of both microglia and astrocytes to inserted probes have been extensively studied in the past yet there remains other glial subtypes in the brain, such as oligodendrocytes and their precursors, the myelin structures they form, as well as vascular-bound pericytes, that have the potential to contribute significantly to the inflammation due to their responsibility to maintain tissue homeostasis. A brief overview of how tissue injury alters the neurochemical makeup followed by alternative potential targets of investigation and novel strategies to enhance the chemical sensing abilities of implantable probes will be discussed.