Electronic biological chips bring ultra-portable detectors closer to reality

January 16th, 2009 - 2:23 pm ICT by ANI  

Washington, January 16 (ANI): A new study has raised Penn State researchers hopes for the development of a handheld device that will recognize and immediately report on a wide variety of environmental or medical compounds.
The researchers say that a method that incorporates a mixture of biologically tagged nanowires onto integrated circuit chips can help develop an ultra-portable device of this kind.
“Probably one of the most important things for connecting to the circuit is to place the wires accurately. We need to control spatial placement on the chip with less than a micron of accuracy,” says Theresa S. Mayer, professor of electrical engineering and director of Penn State’’s Nanofabrication Laboratory.
The researchers say that using standard chip manufacturing would help place each type of nanowire on the board in a separate operation, and then using their bottom-up method would help place three different types of DNA-coated wires where they are wanted, with an error rate of less than one percent.
“This approach can be used to simultaneously detect different pathogens or diseases based on their nucleic acid signatures,” says Christine D. Keating, associate professor of chemistry.
“Device components such as nanowires can be synthesized from many different materials and even coated with biological molecules prior to assembling them onto a chip,” the researchers note in the journal Science.
They add that positioning the nanowires accurately is still difficult using conventional methods.
According to them, their assembly method can be helpful in placing specific nanowires in assigned areas.
The team begin with a chip with tiny rectangular depressions in the places they wish to place the nanowires, and then apply an electrical field between electrodes that define the area where they want the nanowires to assemble.
The researchers inject a mixture of the tagged nanowires and a liquid over the top of the chip. The nanowires are attracted to the area with an electric field and they fall into the proper tiny wells.
“We do not need microfluidic channels to control where each nanowire type goes. We can run the solution over the whole chip and its wires will only attach where they are supposed to attach. This is important for scale-up,” says Mayer.
The researchers later move the electric field and position the next tagged nanowires.
Though the different tagged wires in the current proof-of-concept experiment were placed in rows, the researchers say that they could be placed in a variety of configurations.
Once the wires are in place, they can be made into a variety of devices like resonators or field effect transistors, which can be used to detect nucleic acid targets.
The researchers believe that their assembly method is extremely flexible, capable of placing a variety of conducting and non-conducting wires with a wide array of coatings.
“The eventual idea would be to extend the method to more nanowire types, such as different DNA sequences or even proteins, and move from fluorescence to real-time electrical detection on the chip,” says Keating. (ANI)

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