Nanoparticle stripe sensor for highly sensitive and selective detection of mercury ions.

Mercury and its compounds are emitted during industrial processes and are extremely harmful for eco systems and human health. Therefore, the detection of mercury ions (Hg2+) in our living and working environment is of great importance for the society and especially for the health of human beings. Here we demonstrate a proof of concept nanoparticle stripe sensor for highly sensitive and selective detection of Hg2+. This sensor is based on the changes of the charge transport between the neighboring nanoparticles in the nanoparticle stripe. The addition of Hg2+ induces a chelation between Hg2+ and carboxylic groups on the surface modification molecules and thus facilitates the charge transport, causing an increase of conductivity in the nanoparticle stripe. These nanoparticle stripes with a few layers in height and several micrometers in width possess large surface area, which increases their exposure to ions and improves the ability to detect Hg2+ at low concentrations. Besides, we studied the effect of molecular length on the sensitivity of the sensor. It is shown that the length of surface modification molecules is positively correlated with the sensitivity of the sensor. The fabricated devices exhibit a detection limit as low as 0.1 nM and a specific response towards Hg2+ ions.

Multi-level logic gate operation based on amplified aptasensor performance.

Conventional electronic circuits can perform multi-level logic operations; however, this capability is rarely realized by biological logic gates. In addition, the question of how to close the gap between biomolecular computation and silicon-based electrical circuitry is still a key issue in the bioelectronics field. Here we explore a novel split aptamer-based multi-level logic gate built from INHIBIT and AND gates that performs a net XOR analysis, with electrochemical signal as output. Based on the aptamer-target interaction and a novel concept of electrochemical rectification, a relayed charge transfer occurs upon target binding between aptamer-linked redox probes and solution-phase probes, which amplifies the sensor signal and facilitates a straightforward and reliable diagnosis. This work reveals a new route for the design of bioelectronic logic circuits that can realize multi-level logic operation, which has the potential to simplify an otherwise complex diagnosis to a "yes" or "no" decision.

Electrochemical current rectification-a novel signal amplification strategy for highly sensitive and selective aptamer-based biosensor.

Electrochemical aptamer-based (E-AB) sensors represent an emerging class of recently developed sensors. However, numerous of these sensors are limited by a low surface density of electrode-bound redox-oligonucleotides which are used as probe. Here we propose to use the concept of electrochemical current rectification (ECR) for the enhancement of the redox signal of E-AB sensors. Commonly, the probe-DNA performs a change in conformation during target binding and enables a nonrecurring charge transfer between redox-tag and electrode. In our system, the redox-tag of the probe-DNA is continuously replenished by solution-phase redox molecules. A unidirectional electron transfer from electrode via surface-linked redox-tag to the solution-phase redox molecules arises that efficiently amplifies the current response. Using this robust and straight-forward strategy, the developed sensor showed a substantial signal amplification and consequently improved sensitivity with a calculated detection limit of 114nM for ATP, which was improved by one order of magnitude compared with the amplification-free detection and superior to other previous detection results using enzymes or nanomaterials-based signal amplification. To the best of our knowledge, this is the first demonstration of an aptamer-based electrochemical biosensor involving electrochemical rectification, which can be presumably transferred to other biomedical sensor systems.