Selective Control of Supported Lipid Bilayers in a Neuromorphic OECT

Neuromorphic engineering was developed to build machines able to emulate key features of the brain that allows for the fulfilment of several complex tasks at the same time, with unmatched energy efficiency. To date, hardware implementation of spiking neurons has been successfully developed, in which complex silicon-based building blocks may be combined to mimic several aspects of biological neurons¹.<br/>Conversely, neuron-inspired devices cannot be limited to communicate through spikes, but they may require additional features like synaptic plasticity². In light of this, organic neuromorphic devices and in particular PEDOT:PSS-based organic electrochemical transistors (OECTs) are emerging as ideal candidates, as their biocompatibility and soft-nature allows for the integration with living tissue³.<br/>In this scenario, in order to promote the seamless integration between artificial and biological neurons, the integration of neuromorphic OECTs with a supported lipid bilayer (SLB), was successfully demonstrated⁴, enhancing neuromorphic features, such as short-term plasticity (STP).<br/>While proving the possibility of integrating a biomembrane with an organic transistor, such artificial device is still far from recapitulating an actual post-synaptic neuron, hampering a proper interface with living cells. In fact, the composition of the SLB used is still far from the complex architecture of a neuronal membrane. In addition, the positioning of the bilayer between the gate and the channel of the OECT hinders the passage of ions. Furthermore, long-term plasticity (LTP) was not demonstrated.<br/>In light of this, the present work proposes to go further, by exploiting a microfluidic module coupled to a solvent-assisted lipid bilayer⁵ (SALB) technique that allows to form and confine a neuron-inspired phospholipidic membrane on the polymeric channel of a planar-gated PEDOT:PSS-based OECT, <i>de facto</i> engineering a post-synaptic artificial neurons. The correct formation and the morphological properties of the bilayer are investigated and the effect of the SLB on the electrical properties of the artificial neuron are assessed. Here, such unprecedented integration allows for the enhancement of the biomimetic potential of the transistor, while not hindering the free passage of ions. In addition, neurotransmitter-mediated LTP is demonstrated. This work ultimately paves the way towards the building of new biomimetic platforms that can be used to interface with living neurons in their native environment.<br/><br/>References<br/>1. Indiveri, G. <i>et al.</i> Neuromorphic Silicon Neuron Circuits. <i>Front. Neurosci.</i> <b>5</b>, (2011).<br/>2. Kandel, E. R., Schwartz, J. H., Jessell, T. M., Siegelbaum, S. A. & Hudspeth, A. J. <i>Principles of neural science</i>. vol. 4 (McGraw-hill New York, 2000).<br/>3. Mariano, A. <i>et al.</i> Advances in Cell-Conductive Polymer Biointerfaces and Role of the Plasma Membrane. <i>Chem. Rev.</i> (2021) doi:10.1021/acs.chemrev.1c00363.<br/>4. Lubrano, C., Bruno, U., Ausilio, C. & Santoro, F. Supported Lipid Bilayers Coupled to Organic Neuromorphic Devices Modulate Short-Term Plasticity in Biomimetic Synapses. <i>Adv. Mater.</i> <b>34</b>, 2110194 (2022).<br/>5. Ferhan, A. R. <i>et al.</i> Solvent-assisted preparation of supported lipid bilayers. <i>Nat. Protoc.</i> <b>14</b>, 2091–2118 (2019).