A guide towards long-term functional electrodes interfacing neuronal tissue

Implantable electronics address therapeutical needs of patients with electrical signaling dysfunctions such as heart problems, neurological disorders or hearing impairments. While standard electronics are rigid, planar and made of hard materials, their surrounding biological tissues are soft, wet and constantly in motion. These intrinsic differences in mechanical and chemical properties cause physiological responses that constitute a fundamental challenge to create functional long-term interfaces. Using soft and stretchable materials for electronic implants decreases the mechanical mismatch between implant and biological tissues. As a result, tissue damage during and after implantation is reduced, leading not only to an attenuated foreign body response, but also enabling completely novel applications. However, but for a few exceptions, soft materials are not sufficient to create long-term stable functional implants. In this work, we review recent progress in interfacing both the central (CNS) and peripheral nervous system (PNS) for long-term functional devices. The basics of soft and stretchable devices are introduced by highlighting the importance of minimizing physical as well as mechanical mismatch between tissue and implant in the CNS and emphasizing the relevance of an appropriate surface chemistry for implants in the PNS. Finally, we report on the latest materials and techniques that provide further electronic enhancements while reducing the foreign body reaction. Thus, this review should serve as a guide for creating long-term functional implants to enable future healthcare technologies and as a discussion on current ideas and progress within the field

Formation of Mono(dithiolene)-Thiocarboxamido Complexes in Reactions of Thio(dithiocarbamato)-Mo/W Complexes and Dimethyl Acetylenedicarboxylate

Reactions of Tp*MS(S2CNEt2) with dimethyl acetylenedicarboxylate in dichloromethane produce olive green/black Tp*M{S2C2(CO2Me)2}(SCNEt2-2S,C) (M = Mo (1), W (2); Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate). The seven-coordinate complexes exhibit pseudo-octahedral (1) and distorted pentagonal bipyramidal (2) coordination spheres comprised of tridentate fac-Tp*, bidentate dithiolene, and thiocarboxamido-2S,C ligands. In the solid state, molecules of 1 exhibit pseudo-Cs symmetry, with the thiocarboxamide NEt2 group in a cleft in the Tp* ligand. Molecules of 2 have C1 symmetry in the solid state; here, the thiocarboxamide unit is orientated along one of the W-S(dithiolene) bonds with its NEt2 group projecting away from the Tp* ligand. Both complexes possess effective Cs symmetry in solution. Reaction of Tp*MoI(CO)3 with AgS2CNEt2 affords olive green Tp*Mo(S2CNEt2)(CO)2 (3), which reacts with propylene sulfide in a new synthesis for Tp*MoS(S2CNEt2), the starting material for 1. Complex 3 exhibits a distorted pentagonal bipyramidal structure, the axial sites being defined by a Tp* nitrogen atom and a carbonyl ligand, the pentagonal plane by the remaining nitrogen and carbonyl donors and the two sulfur atoms of the bidentate dithiocarbamate ligand.Patrick J. Lim, Damian A. Slizys, Edward R. T. Tiekink, and Charles G. Youn