Tunable Signal-Off and Signal-On Electrochemical Cisplatin Sensor

We report the first electrochemical cisplatin sensor fabricated with a thiolated and methylene blue (MB)-modified oligo-adenine (A)-guanine (G) DNA probe. Depending on the probe coverage, the sensor can behave as a signal-off or signal-on sensor. For the high-coverage sensor, formation of intrastrand Pt­(II)-AG adducts rigidifies the oligo-AG probe, resulting in a concentration-dependent decrease in the MB signal. For the low-coverage sensor, the increase in probe-to-probe spacing enables binding of cisplatin via the intrastrand GNG motif (N = A), generating a bend in the probe which results in an increase in the MB current. Although both high-coverage signal-off and low-coverage signal-on sensors are capable of detecting cisplatin, the signal-on sensing mechanism is better suited for real time analysis of cisplatin. The low-coverage sensor has a lower limit of detection, wider optimal AC frequency range, and faster response time. It has high specificity for cisplatin and potentially other Pt­(II) drugs and does not cross-react with satraplatin, a Pt­(IV) prodrug. It is also selective enough to be employed directly in 50% saliva and 50% urine. This detection strategy may offer a new approach for sensitive and real time analysis of cisplatin in clinical samples

Electrochemical Detection of Platinum(IV) Prodrug Satraplatin in Serum

We report the design and fabrication of a reagentless and reusable electrochemical sensor for detection of satraplatin (SAT), a platinum­(IV) prodrug. The detection strategy is based on the electrocatalytic reaction between the Pt­(IV) center of SAT and surface-immobilized methylene blue. We systematically evaluated the effect of passivating diluent chain length on the overall sensor performance. Our results show that the use of a shorter diluent like 2-mercaptoethanol is more advantageous than using a longer and more passivating diluent such as 6-mercapto-1-hexanol. Independent of the use of cyclic voltammetry or chronoamperometry as the sensor interrogation technique, all three sensors, each passivated with a different alkanethiol diluent, have been demonstrated to be sensitive; the limit of detection is in the range of 1–10 μM. They are also highly specific and do not respond to Pt­(II) drugs such as cisplatin and carboplatin. More importantly, they are selective enough to be employed directly in 50% serum. This sensing strategy has potential applications in clinical pharmacokinetics studies

Electrochemical Gold(III) Sensor with High Sensitivity and Tunable Dynamic Range

We report the design and fabrication of a sensitive, specific, and selective electrochemical ion (E-ION) sensor for detection of Au­(III). The signaling mechanism is based on the interactions between Au­(III) and adenine; formation of these complexes rigidifies the methylene blue (MB)-modified oligoadenine probes, resulting in a concentration-dependent reduction in the MB signal. The dynamic range of the sensor can be tuned by simply changing the length of the DNA probe (six (A6) or 12 (A12) adenines). Independent of the probe length, both sensors have demonstrated to be sensitive, with a limits of detection of 50 and 20 nM for the A6 and A12 sensors, respectively. With further optimization, this sensing strategy may offer a promising approach for analyzing Au­(III)

Estimated results of the BOP model.

<p>Estimated results of the BOP model.</p

Cross-tabulation by bike-sharing usage and level of satisfaction.

<p>Cross-tabulation by bike-sharing usage and level of satisfaction.</p

Proportional distribution of usage and satisfaction degree of bike-sharing.

<p>Proportional distribution of usage and satisfaction degree of bike-sharing.</p

Marginal effects for the BOP model.

<p>Marginal effects for the BOP model.</p

Bike-sharing system (bicycles and docking stations) deployment in Ningbo.

<p>Bike-sharing system (bicycles and docking stations) deployment in Ningbo.</p

The rapid growth of bike-sharing programmes.

<p>The rapid growth of bike-sharing programmes.</p

Average daily use of bike-sharing across all months.

<p>Average daily use of bike-sharing across all months.</p