Subthreshold Electrical Stimulation for Controlling Protein-Mediated Impedance Increases in Platinum Cochlear Electrode
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING
Authors: Aregueta-Robles, Ulises A.; Enke, Ya Lang; Carter, Paul M.; Green, Rylie A.; Poole-Warren, Laura A.
Objective: This study evaluated subthreshold biphasic stimulation pulses as a strategy to stabilize electrode impedance via control of protein adsorption. Following implantation, cochlear electrodes undergo impedance fluctuations thought to be caused by protein adsorption and/or inflammatory responses. Impedance increases can impact device power consumption, safe charge injection limits, and long-term stability of electrodes. Methods: Protein-mediated changes in polarization impedance (Z(p)) were measured by voltage transient responses to biphasic current pulses and electrochemical impedance spectroscopy, with and without protein solutions. Four subthreshold stimulation regimes were studied to assess their effects on protein adsorption and impedance; (1) symmetric charge-balanced pulses delivered continuously, (2) at 10% duty cycle, (3) at 1% duty cycle, and (4) an asymmetric charge balanced pulse delivered continuously with a cathodic phase twice as long as the anodic phase. Results: The Z(p) of electrodes incubated in protein solutions without stimulation for 2 h increased by between similar to 28% and similar to 55%. Subthreshold stimulation reduced the rate at which impedance increased following exposure to all protein solutions. Decreases in Z(p) were dependent on the type of protein solution and the stimulation regime. Subthreshold stimulation pulses were more effective when delivered continuously compared to 1% and 10% duty cycles. Conclusion: These results support the potential of subthreshold stimulation pulses to mitigate protein-mediated increase in impedance. Significance: This research highlights the potential of clinically translatable stimulation pulses to mitigate perilymph protein adsorption on cochlear electrodes, a key phenomenon precursor of the inflammatory response.
A functional ratio fluorescence sensor platform based on the graphene/Mn-ZnS quantum dots loaded with molecularly imprinted polymer for selective and visual detection sinapic acid
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
Authors: Zhu, Rongkun; Lai, Mushen; Zhu, Mingfang; Liang, Huanru; Zhou, Qing; Li, Rui; Zhang, Wenhao; Ye, Hongqing
A functional ratio fluorescence sensor based on themolecularly imprinted polymer (MIP) coated double quantum dots (QDs) being composited of Mn-ZnS QDs and silica-coated graphene quantum dots (GQDs@SiO2) had been established for the sensitive, selective and visual detection of sinapic acid (SA). MIPs@Mn-ZnS/GQDs@SiO2 was synthesized through a simple one-pot sol-gel reaction, and it exhibited two fluorescence emission peaks with yellow fluorescence of Mn-ZnS QDs at 580 nm and the blue fluorescence of GQDs at 445 nm. SA can selectively enhance the fluorescence of GQDs but quench the Mn-ZnS QDs fluorescence to the MIPs@Mn-ZnS/GQDs@SiO2. The ratio of fluorescence enhancement to fluorescence reduction is linear with the concentration of SA from 9 to 81 nM with the detection limits of 0.8388 nM (S/N = 3). And the constructed fluorescent probe can also be used to visually detect SA according to the change of color. More importantly, molecular imprinting technique enables the sensors to selectively recognize the SA while other similar structure molecules hardly interfere with the SA determination in the measurement environment. Meanwhile, the fluorescence sensors have the advantages of fast response time and long duration of fluorescence intensity. These excellent performances made the proposed method to be applied for the determination of SA in Semen Sinapis and Descurainiae Semen. (C) 2020 Elsevier B.V. All rights reserved.