Probe-type bioelectronics hold enormous clinical potential for diagnosis and treatment of neurodegenerative and cardiac diseases and abnormalities. Transient devices are attractive alternatives to conventional silicon electrodes, as they can provide short-term electrical stimulation/recording followed by complete device degradation, mitigating the need for removal surgeries. Although transient devices have been developed, a fully transient probe-type electrode has yet to be realized. In the present work, we take steps to address shortcomings of current electrode technologies through the design of conductive, flexible constructs with tunable degradation in aqueous environments.<br/><br/>One central component in a degradable electrode is the conductive circuitry, often fabricated using transient metals. The trade-off between stable electrical stimulation/recording and degradation, however, represents a significant challenge for transient metal-based devices as the metal undergoes rapid corrosion in aqueous conditions. Routes to protect the metal circuitry using polymer and/or oxide passivation approaches have been explored, where any such coating must also be degradable under physiological conditions. Instead of protecting the circuitry, these coatings can undesirably initiate corrosion. We address this challenge by coating a model transient metal material (magnesium wires) via a solvent-free compression molding strategy. Our coating approach centers on silk fibroin, owing to its biocompatibility, processing ability, desirable mechanical properties, and controllable degradation behavior in aqueous environments. These proof-of-concept transient constructs provide a framework to develop a fundamental understanding of synergies between transient metal degradation and coating degradation. Specifically, we explored how tuning construct chemical and physical properties alters degradation kinetics, as well as routes to improve coating conductivity by silk chemical modification with synthetic as well as biomass-derived carbon allotropes. Preliminary findings assessing coating morphology, chemical composition, and crystallinity/secondary structure will be presented, pertaining to the impact on device performance. Additionally, we will present findings on device conductivity as a function of degradation. Ultimately, knowledge established in these fundamental studies will be used to inform the design of probe-type bioelectronics implant with completely tunable properties.

Transient probe-type bioelectronics implants: Solvent-free strategy to coat transient metals with silk

256th National Meeting (2018)

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