Browsing by Author "Srivastava, S. B."

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    Nanoengineering InP quantum dot-based photoactive biointerfaces for optical control of neurons
    (Frontiers Media S.A., 2021-06-23) Karatum, O.; Aria, M. M.; Eren, G. Ö.; Yıldız, E.; Melikov, R.; Srivastava, S. B.; Sürme, S.; Bakış Doğru, I.; Jalali, H. B.; Ulgut, Burak; Şahin, A.; Kavaklı, İ. H.; Nizamoğlu, S.
    Light-activated biointerfaces provide a non-genetic route for effective control of neural activity. InP quantum dots (QDs) have a high potential for such biomedical applications due to their uniquely tunable electronic properties, photostability, toxic-heavy-metal-free content, heterostructuring, and solution-processing ability. However, the effect of QD nanostructure and biointerface architecture on the photoelectrical cellular interfacing remained unexplored. Here, we unravel the control of the photoelectrical response of InP QD-based biointerfaces via nanoengineering from QD to device-level. At QD level, thin ZnS shell growth (∼0.65 nm) enhances the current level of biointerfaces over an order of magnitude with respect to only InP core QDs. At device-level, band alignment engineering allows for the bidirectional photoelectrochemical current generation, which enables light-induced temporally precise and rapidly reversible action potential generation and hyperpolarization on primary hippocampal neurons. Our findings show that nanoengineering QD-based biointerfaces hold great promise for next-generation neurostimulation devices.
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    Plasmon-coupled photocapacitor neuromodulators
    (American Chemical Society, 2020) Melikov, R.; Srivastava, S. B.; Karatum, O.; Doğru-Yüksel, I. B.; Jalali, H. B.; Sadeghi, S.; Dikbaş, U. M.; Ülgüt, Burak; Kavaklı, İ. H.; Çetin, A. E.; Nizamoğlu, Sedat
    Efficient transduction of optical energy to bioelectrical stimuli is an important goal for effective communication with biological systems. For that, plasmonics has a significant potential via boosting the light−matter interactions. However, plasmonics has been primarily used for heat-induced cell stimulation due to membrane capacitance change (i.e., optocapacitance). Instead, here, we demonstrate that plasmonic coupling to photocapacitor biointerfaces improves safe and efficacious neuromodulating displacement charges for an average of 185% in the entire visible spectrum while maintaining the faradic currents below 1%. Hotelectron injection dominantly leads the enhancement of displacement current in the blue spectral window, and the nanoantenna effect is mainly responsible for the improvement in the red spectral region. The plasmonic photocapacitor facilitates wireless modulation of single cells at three orders of magnitude below the maximum retinal intensity levels, corresponding to one of the most sensitive optoelectronic neural interfaces. This study introduces a new way of using plasmonics for safe and effective photostimulation of neurons and paves the way toward ultrasensitive plasmon-assisted neurostimulation devices.