Negatively-charged supported lipid bilayers regulate neuronal adhesion and outgrowth

One of the main challenges in neuroelectronics is the implementation of electronic platforms able to secure a tight coupling with neuronal cells and achieve an optimal signal to noise ratio during stimulation/recording of electrophysiological activity. In this context, supported lipid bilayers (SLBs), recapitulating the structure and the dynamicity of the biological plasma membrane, offer a promising biomimetic approach to trick cells to recognize a device as part of their native environment, tightening the cell-chip coupling. Among possible functionalization strategies used to improve cell adhesion on SLBs, the modification of the bilayer surface charge has been exploited to enhance the electrostatic interaction between the artificial membrane and its biological counterpart. In this work, several SLBs with different lipidic composition were synthesized and interfaced with primary neurons. Starting from a neuron-inspired biomembrane, the negative charges were increased through the addition of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(succinyl) (succinyl-PE), a lipid exposing phosphate (PO(4)(−)) groups; furthermore, the reactivity of the succinyl carboxylate group enabled the subsequent addition of negatively charged sulfonate (SO(3)(−)) groups. The synthesized SLBs were then tested as platforms for neuronal adhesion and network formation. Despite the expected repulsive electrostatic interactions, our work suggests that negatively charged SLBs may influence neurite elongation and branching, highlighting the potential of surface charge to tune neuronal processes at the neuron–SLB interface.