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The impedance spectral response of electrochemical systems to multi sine (MS) potential perturbations was simulated using numerical techniques. The MS waves comprised of odd harmonic waves and were applied to a simple electron transfer reaction, and a reaction with an adsorbed intermediate. The governing equations were solved without linearization. Two choices of frequency sets with phases corresponding to the minimum crest factor were employed. The effects of large amplitude perturbations, potential instability, noise and solution resistance were investigated. The EIS data were subjected to Kramers Kronig transforms (KKT). The results show that (i) if large amplitude perturbations are used, the spectra acquired using MS appear to be noisy and they violate KKT, (ii) potential drifts and noise effects are successfully identified by KKT and (iii) in the presence of a significant solution resistance, the kinetic equations must be employed along with the equivalent circuit model to estimate the kinetic parameters.

Enhancing an endogenous stem cell response is a promising approach to improve stroke recovery. We have previously shown that a conductive polymer cannula system for human stem cell delivery and electrical stimulation of the post-stroke environment increases endogenous stem cell production and improves functional recovery in a rodent model of distal middle cerebral artery occlusion (dMCAO). Transcriptomic analyses coupled with lentiviral manipulation identified stanniocalcin 2 (STC-2) as one key mediator of this functional improvement. To further investigate the role of STC-2, we intraventricularly administered recombinant STC-2 one week post-dMCAO and assessed functional recovery via vibrissae-forepaw (WP) test at 5 weeks. Our results indicate that intraventricular injection of STC-2 alone post-stroke improves functional recovery in comparison to a control and intraventricular saline group (n=10 per group, p=<0.001, see Figure 1A). Histological analyses revealed an increase in endogenous stem cells that express immature neuronal markers (doublecortin, colocalized with bromodeoxyuridine) between the subventricular zone and peri-infarct region of the STC2-treated group (n=5 per group; p=0.019, see Figure 1B). Additional studies are necessary in order to further elucidate the causative molecular mechanisms involved; however, we believe this study yields great translational potential as our results may help enable a route to augment endogenous responses in the post-stroke environment.

The impedance spectral response of electrochemical systems to multi sine (MS) potential perturbations was simulated using numerical techniques. The MS waves comprised of odd harmonic waves and were applied to a simple electron transfer reaction, and a reaction with an adsorbed intermediate. The governing equations were solved without linearization. Two choices of frequency sets with phases corresponding to the minimum crest factor were employed. The effects of large amplitude perturbations, potential instability, noise and solution resistance were investigated. The EIS data were subjected to Kramers Kronig transforms (KKT). The results show that (i) if large amplitude perturbations are used, the spectra acquired using MS appear to be noisy and they violate KKT, (ii) potential drifts and noise effects are successfully identified by KKT and (iii) in the presence of a significant solution resistance, the kinetic equations must be employed along with the equivalent circuit model to estimate the kinetic parameters.