A Combinatory Therapy of Metformin and Dexamethasone Reduces the Foreign Body Reaction to Intraneural Electrodes

Neural electrodes used for bidirectional communication between the nervous system and external devices like prosthetic limbs have advanced in neuroprosthetic applications. However, their effectiveness is hindered by the foreign body reaction, a natural immune response causing inflammation and fibrosis around the implanted device. This process involves protein adsorption, immune cell recruitment, cytokine release, and fibroblast activation, leading to a fibrous capsule formation and a decrease in electrode functionality. Anti-inflammatory and antifibrotic strategies have the potential to diminish the impact of the foreign body response. In this work, we have evaluated long-term metformin administration and short-term dexamethasone administration as a combined therapy to modulate the foreign body reaction induced by a polyimide intraneural implant in the sciatic nerve of rats. After a 12-week implant, the foreign body reaction was significantly reduced only in the group administered both drugs.