Development of synthetic nerve endings for axo-axonal transport and testing as acetylcholine ion pump

Currently, more than 450 million people are globally suffering from some types of neurological diseases that can hardly be treated. These diseases are caused by distorted electrical and neurochemical signaling in the nervous system. The awareness of this worldwide problem is not brought in yet and definitive treatment has not been introduced so far. Most of therapies associated with neurological disorders are based on medical treatment such as medical therapy or electric stimulation. However, results are temporary and ineffective. The major effect obtained so far, was to conceal the disease and this was just not enough. In our study, by taking into consideration this problem we are presenting a biomimetic system that duplicates the function of a neural cell and helps to reinstitute the defective electrochemical transport of nervous system. Nerve impulses are communicated across synapses by diffusible molecules called neurotransmitters, of which one is acetylcholine. Acetylcholine molecules are contained in the axon foot inside vesicles. After the release of acetylcholine into the synaptic cleft, it binds to the cholinergic receptors located on the postsynaptic neuron and mediate excitation or inhibition on postsynaptic cells and thus causing the transportation of neural signal. The system developed by our group resembles a two electrode structure with PEDOT:PSS deposited on them and a tiny 2 mm overoxidized region that cuts off electrical conductivity thus allowing only ionic transport. By using an easy and effective method of depositing conjugated polymers (PEDOT:PSS) on flexible substrates, a new design for organic bioelectronic devices has been developed. FTIR and Raman measurements have demonstrated that electrochemical overoxidation region which separates the PEDOT:PSS electrodes and allows ionic conduction has been achieved successfully. The influence of both electrical and ionic conductivities on organic electronic ion pump (OEIP) performances has been studied. The highest equilibrium current density, which corresponds to 4.81x1017 number of ions of acetylcholine was about 41 μA cm-2 observed for the OEIP with the electrical conductivities of 54 Scm-1. The OEIP performances were not changed much beyond this threshold electrical conductivity. Once Nafion™ has been applied for enhancing the ionic conductivity, the equilibrium current density increased about ten times and reached up to 408 μAcm-2. Therefore, it has been demonstrated that the OEIP performance mainly scales with the ionic conductivity. A straightforward method of producing organic bioelectronics is proposed here giving rise to their effortless mass production in the near future.