Nanoswitches for bio-silicon communication

May 16, 2006

Brussels, 15 May 2006

Against the odds, European researchers have developed a versatile molecular switch which could play a key role in vast nanotechnology applications, including motors, relays and biosensors. The EU-funded Mol-Switch project recently unveiled a working model, reports IST Results.

Two scientific developments have stolen headlines in the past decade: progress in DNA sequencing, genomics and proteomics, and the quest for smaller and smaller technologies at the nano-scale and beyond. Success in the nearly €2 million EU-funded Mol-Switch project brings these biological and microelectronics worlds much closer together.

Despite scepticism in the scientific world, English, French, Italian, Dutch and Czech scientists have been constructing a single-molecule DNA-sequencing device and accompanying nano-switch based on a biological molecular motor and a moving magnetic bead. According to the team, the secret to success was in the 'microfluidics chip' with its tiny (nano-scale) channels moving in a predictable fashion.

The floor of this channel is peppered with 'Hall-Effect' sensors, accurately describing how a magnetic field influences an electric current. These measurements link the biological motor with the electronic signals of the silicon world. The biological element of the device starts with a DNA molecule fixed to the floor of the microfluidic channel. This strand is held upright – picture a string held up by a weather balloon – by anchoring the floating end of the DNA strand to a magnetic bead, itself held up under the influence of magnetism.

A specific type of protein, called a Restriction-Modification enzyme, provides one of the DNA motors. This type of DNA motor will only bind to a specific sequence of the DNA bases (A, C, G and T). "This binding is very specific," Mol-Switch's coordinator Dr Keith Firman of Portsmouth University told IST Results. "A motor will bind only with its corresponding bases, so you can control exactly where the motor is placed on the vertical DNA strand," he says.

The motor is attached to the strand at the specific sequence of bases. Then the team introduces ATP, the phosphate molecule that provides energy within living cells, into the microfluidics channel. This is the fuel for the motor. The motor then pulls the upright DNA strand through it until it reaches the magnetic bead, like a winch lowering a weather balloon.

As far as the imagination can see In fact, the Hall-Effect sensor can measure the vertical movement of the magnetic bead which indicates whether the molecular switch is on or off – thus acting as a versatile nano-scale actuator. Actuators are all around us converting various energy into mechanical or eletrical forms. "The light switch, the button that makes a retractable pen; all these are actuators, and by developing a molecular switch we've created a tiny actuator that could be used in an equally vast number of applications," explains Firman.

For example, it could be put to use in biosensors, flow-control valves, relays and advanced prosthetics. In addition, the magnetic bead attached to DNA can be used in the single-molecule DNA sequencing apparatus (to overcome coiling due to entropy) and for monitoring the movement of the DNA molecule.

It could one day be used as a communicator between the biological and silicon worlds, providing an interface between muscle and external devices used for implants, for example. A bonus application is in DNA sequencing – in this case, actually mapping the order of the four DNA-bases, which is a core step for genetic research.

DG Research
http:///europa.eu.int/comm/dgs/research/i ndex_en.html

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