Mechanical Stability of Nano‐Coatings on Clinically Applicable Electrodes, Generated by Electrophoretic Deposition

• Published in: Advanced healthcare materials 2022-12, Vol.11 (23), p.e2102637-n/a
• Main Authors: Ramesh, Vaijayanthi, Stratmann, Nadine, Schaufler, Viktor, Angelov, Svilen D., Nordhorn, Ilona D., Heissler, Hans E., Martínez‐Hincapié, Ricardo, Čolić, Viktor, Rehbock, Christoph, Schwabe, Kerstin, Karst, Uwe, Krauss, Joachim K., Barcikowski, Stephan
• Format: Article
• Language: English
• Subjects: Adhesives; Animals; biocompatibility; biomaterials; Brain; Coated electrodes; Coatings; colloids; deep brain stimulation; Electrodes; Electrophoretic deposition; impedance; In vivo methods and tests; Inductively coupled plasma mass spectrometry; Laser ablation; laser ablation in liquids; Mass spectrometry; Mass spectroscopy; Metal Nanoparticles; Nanoparticles; Platinum; Rats; Stimulation; Surface stability
• ISSN: 2192-2640; 2192-2659; 2192-2659
• DOI: 10.1002/adhm.202102637

The mechanical stability of implant coatings is crucial for medical approval and transfer to clinical applications. Here, electrophoretic deposition (EPD) is a versatile coating technique, previously shown to cause significant post‐surgery impedance reduction of brain stimulation platinum electrodes. However, the mechanical stability of the resulting coating has been rarely systematically investigated. In this work, pulsed‐DC EPD of laser‐generated platinum nanoparticles (PtNPs) on Pt‐based, 3D neural electrodes is performed and the in vitro mechanical stability is examined using agarose gel, adhesive tape, and ultrasonication‐based stress tests. EPD‐generated coatings are highly stable inside simulated brain environments represented by agarose gel tests as well as after in vivo stimulation experiments. Electrochemical stability of the NP‐modified surfaces is tested via cyclic voltammetry and that multiple scans may improve coating stability could be verified, indicated by higher signal stability following highly invasive adhesive tape stress tests. The brain sections post neural stimulation in rats are analyzed via laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS). Measurements reveal higher levels of Pt near the region stimulated with coated electrodes, in comparison to uncoated controls. Even though local concentrations in the vicinity of the implanted electrode are elevated, the total Pt mass found is below systemic toxicologically relevant concentrations. The mechanical stability of surface modified neural electrodes via electrophoretic deposition using laser‐generated platinum nanoparticles is evaluated. In vitro stability tests show the lowest impedance increase after agarose gel test. After in vivo deep brain stimulation (DBS) in rats, the amount of biodispersed platinum is higher in coated electrodes though being fourfold lower than toxicologically relevant systemic concentrations.