We report a microelectrochemical array composed of 1000 individual bipolar electrodes that are controlled with just two driving electrodes and a simple power supply. The system is configured so that faradaic processes occurring at the cathode end of each electrode are correlated to light emission via electrogenerated chemiluminescence (ECL) at the anode end. This makes it possible to read out the state of each electrode simultaneously. The significant advance is that the electrode array is fabricated on a glass microscope slide and is operated in a simple electrochemical cell. This eliminates the need for microfluidic channels, provides a fabrication route to arbitrarily large electrode arrays, and will make it possible to place sensing chemistries onto each electrode using a robotic spotter.
Here we report an electrochemical DNA microarray sensor whose function is controlled using just two wires regardless of the number of individual sensing electrodes. This advance is enabled by confining bipolar sensing electrodes within a microfluidic channel (part a of Scheme 1) and exerting potential control over the electrolyte solution rather than individual electrodes. In this configuration, the two driving electrodes control the potential difference between the sensing electrodes and the solution, and the current at the sensing electrodes is indirectly measured by taking advantage of electrogenerated chemiluminescence (ECL) present at the anode end of each bipolar electrode. In this communication, we show that this approach can be used to sense hybridization of DNA oligonucleotides.Electrochemistry is normally carried out by controlling the electrode potential. However, because the potential difference between the electrode and the solution drives the electron-transfer reaction, it is equally effective to control the potential of the solution. Our approach for using this principle is illustrated in part b of Scheme 1. 1,2 An external potential (E tot ) is applied to the two ends of a microchannel, and the resistance of the electrolyte solution results in a linear potential gradient (dE/dx) along the channel. The difference in potential between the two ends of the bipolar electrode (∆E elec ) is the fraction of E tot dropped across the length of this electrode (L elec ). If ∆E elec is sufficiently large, then faradaic electrochemical processes will occur simultaneously at both ends of the bipolar electrode. Because of the requirement for charge balance, the rate of electron transfer (i.e., the current) at both ends of the electrode must be the same.A significant deficiency of bipolar electrochemistry is that there is no means for directly measuring current flowing within an electrode. 1,2 The experimental configuration illustrated in part c of Scheme 1 addresses this problem. Here, E tot is held at a sufficiently high value that the ECL reaction resulting from the oxidation of Ru(bpy) 3 2+ and tri-n-propylamine (TPrA), 3-5 indicated at the anode end of the bipolar electrode, is activated upon electrocatalytic reduction of O 2 at the cathode end of the electrode. In the sensing experiments discussed next, the oxygen reduction reaction (ORR) is catalyzed by hybridization of target DNA labeled with Pt nanoparticles (Pt-NPs) to previously immobilized capture DNA. 6 Accordingly, in the presence of DNA hybridization at the cathode, light is emitted from the anode.Part a of Figure 1 shows that the sensor consists of a microfluidic device and three Au electrodes. The poly(dimethylsiloxane) (PDMS) microfluidic device was prepared by a standard micromolding method. 7 The microchannel was 12 mm long, 1.75 mm wide, and 26 µm high. The three Au electrodes (1.00 × 0.25 mm) were microfabricated on a glass slide and configured parallel to one another at the center of the channel. Two Pt wires were placed in reservoirs at ei...
We report a two-channel microelectrochemical sensor that communicates between separate sensing and reporting microchannels via one or more bipolar electrodes (BPEs). Depending on the contents of each microchannel and the voltage applied across the BPE, faradaic reactions may be activated simultaneously in both channels. As presently configured, one end of the BPE is designated as the sensing pole and the other as the reporting pole. When the sensing pole is activated by a target, electrogenerated chemiluminescence (ECL) is emitted at the reporting pole. Compared to previously reported single-channel BPE sensors, the key advantage of the multichannel architecture reported here is physical separation of the ECL reporting cocktail and the solution containing the target. This prevents chemical interference between the two channels.
In this study, we investigate the use of multifunctional smart radiotherapy biomaterials (SRBs) loaded with immunoadjuvants for boosting the abscopal effect of local radiotherapy (RT). SRBs were designed similar to currently used inert RT biomaterials, incorporating a biodegradable polymer with reservoir for loading payloads of the immunoadjuvant anti-CD40 monoclonal antibody. Lung (LLC1) tumors were generated both on the right and left flank of each mouse, with the left tumor representing metastasis. The mice were randomized and divided into eight cohorts with four cohorts receiving image-guided RT (IGRT) at 5 Gy and another similar four cohorts at 0 Gy. IGRT and Computed Tomography (CT) imaging were performed using a small animal radiation research platform (SARRP). Tumor volume measurements for both flank tumors and animal survival was assessed over 25 weeks. Tumor volume measurements showed significantly enhanced inhibition in growth for the right flank tumors of mice in the cohort treated with SRBs loaded with CD40 mAbs and IGRT. Results also suggest that the use of polymeric SRBs with CD40 mAbs without RT could generate an immune response, consistent with previous studies showing such response when using anti-CD40. Overall, 60% of mice treated with SRBs showed complete tumor regression during the observation period, compared to 10% for cohorts administered with anti-CD40 mAbs, but no SRB. Complete tumor regression was not observed in any other cohorts. The findings justify more studies varying RT doses and quantifying the immune-cell populations involved when using SRBs. Such SRBs could be developed to replace currently used RT biomaterials, allowing not only for geometric accuracy during RT, but also for extending RT to the treatment of metastatic lesions.
Here we report a simple design philosophy, based on the principles of bipolar electrochemistry, for the operation of microelectrochemical integrated circuits. The inputs for these systems are simple voltage sources, but because they do not require much power they could be activated by chemical or biological reactions. Device output is an optical signal arising from electrogenerated chemiluminescence. Individual microelectrochemical logic gates are described first, and then multiple logic circuits are integrated into a single microfluidic channel to yield an integrated circuit that can perform parallel logic functions. AND, OR, NOR, and NAND gates are described. Eventually, systems such as those described here could provide on-chip data processing functions for lab-on-a-chip devices.
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