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August 17, 2012

Lab-on-a-chip using Nanowires provides heart attack detection in minutes

Science News - Looking for a specific protein in a drop of blood is like trying to find a notorious white whale on the seven seas — it takes some time. But a new device quickly filters the ocean of molecules in a blood sample, capturing proteins that may warn of an impending heart attack or out-of-whack insulin levels. Besides detecting potential emergencies, such devices could minimize the fraught days a patient spends waiting for lab results, providing them in mere minutes.

Experiments showed the setup detected various levels of troponin T, a cardiac-regulating protein that can signal an impending heart attack, in less than 10 minutes.

In the future, people at home who are having chest pains might use the technology to find out quickly whether they need to get to an emergency room, says biomedical chemist Fernando Patolsky.

The sugar-cube–sized lab-on-a-chip consists of two small compartments connected by a thin channel. In the first compartment is a densely packed forest of silicon nanowires coated with antibodies, molecules that latch onto specific proteins. The researchers made these nanowires very rough and full of holes, greatly increasing the surface area for attaching the protein-grabbing antibodies.

“They are so rough and porous we can turn a 1-centimeter-square wafer into a 300-centimeter-square surface,” Patolsky says.



Nanoletters - Si Nanowires Forest-Based On-Chip Biomolecular Filtering, Separation and Preconcentration Devices: Nanowires Do it All



ABSTRACT - The development of efficient biomolecular separation and purification techniques is of critical importance in modern genomics, proteomics, and biosensing areas, primarily due to the fact that most biosamples are mixtures of high diversity and complexity. Most of existent techniques lack the capability to rapidly and selectively separate and concentrate specific target proteins from a complex biosample, and are difficult to integrate with lab-on-a-chip sensing devices. Here, we demonstrate the development of an on-chip all-SiNW filtering, selective separation, desalting, and preconcentration platform for the direct analysis of whole blood and other complex biosamples. The separation of required protein analytes from raw biosamples is first performed using a antibody-modified roughness-controlled SiNWs (silicon nanowires) forest of ultralarge binding surface area, followed by the release of target proteins in a controlled liquid media, and their subsequent detection by supersensitive SiNW-based FETs arrays fabricated on the same chip platform. Importantly, this is the first demonstration of an all-NWs device for the whole direct analysis of blood samples on a single chip, able to selectively collect and separate specific low abundant proteins, while easily removing unwanted blood components (proteins, cells) and achieving desalting effects, without the requirement of time-consuming centrifugation steps, the use of desalting or affinity columns. Futhermore, we have demonstrated the use of our nanowire forest-based separation device, integrated in a single platform with downstream SiNW-based sensors arrays, for the real-time ultrasensitive detection of protein biomarkers directly from blood samples. The whole ultrasensitive protein label-free analysis process can be practically performed in less than 10 min.

8 pages of supporting information

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