Concealing Organic Neuromorphic Devices with Neuronal-Inspired Supported Lipid Bilayers

Abstract

Neurohybrid systems have gained large attention for their potential as in vitro and in vivo platform to interrogate and modulate the activity of cells and tissue within nervous system. In this scenario organic neuromorphic devices have been engineered as bioelectronic platforms to resemble characteristic neuronal functions. However, aiming to a functional communication with neuronal cells, material synthesis, and surface engineering can yet be exploited for optimizing bio-recognition processes at the neuromorphic-neuronal hybrid interface. In this work, artificial neuronal-inspired lipid bilayers have been assembled on an electrochemical neuromorphic organic device (ENODe) to resemble post-synaptic structural and functional features of living synapses. Here, synaptic conditioning has been achieved by introducing two neurotransmitter-mediated biochemical signals, to induce an irreversible change in the device conductance thus achieving Pavlovian associative learning. This new class of in vitro devices can be further exploited for assembling hybrid neuronal networks and potentially for in vivo integration within living neuronal tissues.

Keywords: neurohybrids; neuromorphic devices; organic electrochemical transistor; supported lipid bilayer.

Figure 1

(A) Schematics of the device: i) 3D isometric projection and ii) side view. B) AFM images of bare PEDOT:PSS, POPC‐containing bilayer, and POPC‐chol‐SM‐ containing SLB (1:1:1 in mixture). C) FRAP results of POPC‐bilayer: fluorescence intensity recovery after photobleaching at t = 0 s, 60 s, and 5 min and the corresponding fluorescence intensity profiles. D) FRAP results of POPC‐chol‐SM (Brain) SLB: fluorescence intensity recovery after photobleaching at t = 0 s, 60 s, and 5 min and the corresponding fluorescence intensity profiles.

Figure 2

A) Bode and B) Nyquist plot of bare OECT, POPC, and POPC‐chol‐SM‐containing bilayers. C) Equivalent electrical circuit used for EIS fitting: the resistance described the electrolyte behavior and the capacitance accounted for the membrane. Capacitance and resistance numerical data were estimated by fitting EIS measurements with an electrical equivalent circuit composed by a resistance, accounting for the resistance of the electrolyte, and a capacitance, describing the capacitance of the electrode, connected in series D) Numerical values of the resistance and capacitance of bare OECT, POPC, and POPC‐chol‐SM‐containing bilayers. The presence of the bilayer did not induce a significant change in either parameters, without any significative differences between the two compositions.

Figure 3

A) Calculation of the time constant τ of the ionic circuit between the gate and the channel of the OECT. The time constant corresponds to 63% of charge of the equivalent RC circuit modelling the OECT ionic circuit. The computation of τ was performed by applying a square voltage pulse at the gate electrode and monitoring the channel current to extract the time needed to charge the polymeric channel up to 63% of its maximum charged value. B) Mean values of the τ calculated before and after the formation of SLBs. C,D) The mean conductance variation elicited by gate voltage pulses with Δt equal to 1τ and 5τ with and without SLB. The graph highlighted how the presence of both bilayers increased the conductance modulation. E) Mean values of Δg computed before and after the formation of the SLBs and setting Δt equal to 1τ and 5τ. F,G) Percentage of charge injected/retained in the PEDOT:PSS channel was calculated with Δt equal to 1τ and 5τ. Mean values of charges injected/retained from the gate electrode to the channel was calculated after the application of a voltage pulse with Δt equal to 1τ and 5τ. The voltage bias applied at the gate terminal is 300 mV.

Figure 4

A,B) DA and 5‐HT‐mediated conductance modulation, respectively. The concentration employed for both neurotransmitters is 30 µM. C) Pavlovian associative learning experiment, recapitulated in a neuronal‐inspired SLB‐coated OECT.