![]() In addition, the controlled release of the drugs from the coatings has proved to be challenging, and their limited drug loading capacity renders them unfeasible for long‐term usage. Moreover, an acute inflammatory response is inevitable as these drug‐eluting coatings are incapable of preventing the adsorption of proteins and debris from the punctured cellular membranes that initiate the inflammation signal cascades. ] Although anti‐inflammatory drugs eluted from the neural probe coatings suppress the increase in inflammation due to the chronic foreign body reaction, neuronal damage inflicted during the probe insertion still inevitably occurs. Brain damage during insertion into the brain is also an unavoidable issue for neural probes with drug‐eluting coatings due to probe rigidity. ] Ironically, such strategies for insertion into the brain cause brain tissue damage due to the strong friction that occurs at the probe‐tissue interface owing to the probe's temporarily increased stiffness. ] or integrating them with a rigid shuttle device. To enable the insertion of flexible probes into the brain, insertion force has to be temporarily increased by adopting strategies such as coating the probes with dissolvable materials [ ] However, flexible neural probes with drug‐eluting coatings also come with limitations such as insertion difficulty due to their ultraflexibility. ] A drug‐eluting coating containing anti‐inflammatory drugs has been explored most often as it has the potential to reduce glial encapsulation. Softer material properties in flexible probes have led to less mechanical strain on the surrounding tissue and a minimal chronic immune response resulting from micromotion. The aim of flexible neural probes is to reduce the chronic immune response resulting from the shearing micromotion between the probe material and the neural tissue. To address the issue of gliosis progression, there have been attempts to make probes flexible or combine drug‐eluting coatings on their surfaces. ] Furthermore, the glial sheath thickness increases gradually due to the foreign body reaction, eventually driving neurons away from the electrodes beyond the effective recording range. Acute insertion trauma not only causes an increase of acute neural loss but also accelerates the initial formation of the glial sheath around the implanted probe. However, implanted probes for clinical BMIs have not yet been widely adopted, mainly because of the biological inflammatory response (e.g., gliosis) around the probe‐tissue interface that arises from acute insertion trauma and chronic foreign body reaction. ] have been developed for firm integration with brain tissue to record neural signals stably from neurons. In recent decades, many neural probes with different shapes, [ ] Therefore, it is essential to seamlessly integrate the interface between the brain tissue and the implanted device to record and control neurons over long periods. ] and can control the movement of computer cursors [ ] For example, recorded brain signals using chronically implanted devices can be decoded into a synthesized voice [ By significantly reducing insertion damage and the foreign body reaction, the lubricated immune‐stealthy probe surface (LIPS) can maximize the longevity of implantable BMIs.īrain‐machine interfaces (BMIs) have been spotlighted as a tool to help people with extensive clinical disabilities. Furthermore, the signal measurable period increases from 8 to 16 weeks due to the prevention of gliosis. Reduced friction force leads to 86% less impulse on the brain tissue, and thus immediately increases the number of measured signal electrodes by 102% upon insertion. To address this challenge, a lubricated surface is fabricated to minimize friction during insertion and avoid immunogenicity during neural signal recording. However, the longevity of such implanted devices remains limited by the deterioration of their signal sensitivity over time due to acute inflammation from insertion trauma and chronic inflammation caused by the foreign body reaction. Brain‐machine interfaces (BMIs) that link the brain to a machine are promising for the treatment of neurological disorders through the bi‐directional translation of neural information over extended periods. ![]()
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