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The essential cytoskeletal protein actin and its func- tions are paramount for motility, communication, and locomotive processes in eukaryotic cells. Detection and quantification of actin protein is of great interest for in vitro studies potentially eluci- dating unknown cellular mechanisms affecting drug responses with an extension to the study of disease states (e.g., study of neurodegenerative disorders). To this end, development of biomedical platforms and biosensors plays an important role in providing reliable and sensitive devices to study such intracellular constructs. Here, we present for the first time the microfabrica- tion, characterization, testing, and electrical/interfacial modeling of a microfluidic biosensor for actin protein characterization. The device allows for the interaction and characterization of actin bundles using electrochemical impedance spectroscopy (EIS). The device was tested with 1 μM and 8 μM actin bundles concentrations producing shifts in impedance response in the significant biological frequency of 1 kHz from 17 to 30 kOhm (k). Interfacial capacitance and electrical modeling showed that at increasing actin bundles concentrations, the distance from the electrode to the diffusion region (Debye length) was reduced from 386 to 136, and from 1526 to 539 Å. Inter- facial capacitance was evaluated for 1 μM concentration at two dielectric constants (εr = 5 and 78) resulting in 3.8 and 15.6 mF/m2 respectively. Similarly, for 8 μM concentration, interfacial capacitance resulted in 10.1 and 43.3 mF/m2 for the same values of εr. Based on these theoretical calculations, the interface model could accurately predict the quantification of the actin bundles previously elucidated by the experimental EIS method. 

This paper reports a bioelectric device for measuring impedance and electrophysiology of fertilized and unfertilized killifish embryos. 

Microfabrication and assembly of a Three-Dimensional Microneedle Electrode Array (3D MEA) based on a glass-stainless steel platform is demonstrated involving the utilization of non-traditional “Makerspace Microfabrication” techniques featuring cost-effective, rapid fabrication and an assorted biocompatible material palette. The stainless steel microneedle electrode array was realized by planar laser micromachining and out-of-plane transitioning to have a 3D configuration with perpendicular transition angles. The 3D MEA chip is bonded onto a glass die with metal traces routed to the periphery of the chip for electrical interfacing. Confined precision drop casting (CPDC) of PDMS is used to define an insulation layer and realize the 3D microelectrodes. The use of glass as a substrate offers optical clarity allowing for simultaneous optical and electrical probing of electrogenic cells. Additionally, an interconnect using 3D printing and conductive ink casting has been developed which allows metal traces on the glass chip to be transitioned to the bottomside of the device for interfacing with commercial data acquisition/analysis equipment. The 3D MEAs demonstrate an average impedance/phase of ∼13.3 kΩ/−12.1° at 1 kHz respectively, and an average 4.2 μV noise. Lastly, electrophysiological activity from an immortal cardiomyocyte cell line was recorded using the 3D MEA demonstrating end to end device development.