Electronic control of H⁺ current in a bioprotonic device with carbon nanotube porins - Fig 2

(a) Pd contact with SLB. The SLB blocks H+ from transferring from the solution to the Pd contact even with V = -250 mV (vs. Ag/AgCl). (b) Pd contact with SLB incorporating 0.8 nm diameter CNTPs is semipermeable to H+, with CNTPs facilitating the rapid flow of H+ to the Pd/solution interface. (c) Upon addition of Ca+2 to the bulk solution, H+ current through CNTPs becomes partially blocked. (d) iH+ vs. time plots recorded at V = −250 mV and V = 20 mV. Blue trace: SLB, red trace: SLB with CNTPs, gray trace SLB with CNTPs in presence of Ca+2 ions in the bulk solution. (The data are collected from 3 different devices with different dimensions: Pd / SLB: 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs: 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs+Ca+2: 3 different devices of 2 × 50 μm. The error bars are the root mean square of the displacement of the data from the average value).</p

Conductive AFM of SLB with CNTPs channels.

(a) The current map for the Pd contact with SLB incorporating CNTPs. The hot spot (green spot) correspond to higher current (red trace) that represent CNT and the background (purple area) correspond to negligible amount of current (black trace) which represent SLB membrane. (b) In the IV curve the red trace collected from the green spot and the back trace collected from the purple area. The green spot has i ~ 1.78 nA ± 0.09 nA and purple area has i ~ 5.86 pA ± 0.98 pA. This current most likely represents the electron conductivity of CNT. (The data are collected from 3 different areas of the AFM image for both green spot and purple area. The error bars are the root mean square of the displacement of the data from the average value).</p

A bioprotonic device with integrated carbon nanotube porins (CNTPs) supports proton current across the SLB through the CNTPs when a negative voltage (<i>-V</i>) is applied on the Pd contact.

When H+ reach the surface of the Pd contact, they are reduced to H by an incoming electron and diffuse into the Pd to form palladium hydride (PdHx). The current density at the contact (–iH+), measures the rate of H+ flux along the CNTPs.</p

Electronic control of H⁺ current in a bioprotonic device with carbon nanotube porins - Fig 3

(a) Pd contact with SLB incorporating 0.8 nm diameter CNTPs with K-HEPES buffer at pH = 6.0, is semipermeable to H+, with CNTPs facilitating the rapid flow of H+ to the Pd/solution interface. (b) Pd contact with SLB incorporating Narrow CNTPs with K-HEPES buffer pH = 7.0, is still semipermeable to H+ but facilitating lower flow of H+ to the Pd/solution interface. (c) iH+ versus time plot for V = −250 mV and V = 50 mV. Gray trace SLB, red trace SLB+ CNTps (K-HEPES, pH = 6.0), black trace SLB+ CNTPs (K-HEPES, pH = 7.0). The iH+ for measurements K-HEPES pH = 6.0 is higher than K-HEPES pH = 7. We can hypothesize that at pH = 6.0 we have a driving force due to the lower pH across the membrane in addition to the applied voltage that expedite the flow of H+ while at pH = 7.0 we have only the applied voltage as a driving force to transport the H+ across. We did not observe any significant different between the iH+ at pH = 8.0 as compare to pH = 7.0 which might be due the buffer capacity of HEPES at different pH condition (Fig A in S1 File). (The data are collected from 3 different devices with different dimensions: SLB- K-HEPES pH = 7.0 : 3 different devices of 2 × 50 μm, Pd/SLB+CNTPs+Ca+2: 3 different devices of 2 × 50 μm. The error bars are the root mean square of the displacement of the data from the average value).</p

Delivery of Cargo with a Bioelectronic Trigger

Biological systems exchange information often with chemical signals. Here, we demonstrate the chemical delivery of a fluorescent label using a bioelectronic trigger. Acid-sensitive microparticles release fluorescin diacetate upon low pH induced by a bioelectronic device. Cardiac fibroblast cells (CFs) uptake fluorescin diacetate, which transforms into fluorescein and emits a fluorescent signal. This proof-of-concept bioelectronic triggered delivery may be used in the future for real-time programming and control of cells and cell systems