Vertical Nanowire Arrays Offers Potential for Faster Diagnoses

Reducing spot sizes from microscale to nanoscale facilitates miniaturization of platforms and consequently decreased material consumption, but faces inherent challenges in the reduction of fluorescent signals and compatibility with complex solutions.

Scientists at the University of Copenhagen (Denmark) have constructed vertical arrays of nanowires (NWs) that can overcome several bottlenecks of using nanoarrays for extraction and analysis of proteins. The majority of protein microarray applications use fluorescence detection of proteins due to the simplicity of detection, availability of fluorophores with a wide range of properties and possibilities of multiplexing, although label-free techniques are emerging as interesting alternatives.

The investigators used ordered arrays of vertically aligned indium arsenide (InAs) NW arrays to perform bioanalytical assays on protein nanospots. The three dimensional structure of the NWs substantially increases the amount of protein that can be immobilized on each feature of the array, thereby increasing the signal from nanometer-sized spots. Furthermore, the high aspect ratio of the NWs allows the detection of signals several micrometers away from the surface of the chip, thus rendering passivation of the surface between the NWs unnecessary.

The nanowires stand up like a little forest, creating a much greater surface area to hold the proteins because they can attach to all sides of the nanowire. When examining the proteins, the nanowires can be reused by performing a multiple tests on the same protein. This simplifies the workflow in the laboratory greatly in comparison to the conventional method, where scientists have to start over with a new plate to hold the proteins every time they perform a new analysis. In this way, the method helps to make the diagnostic process more environmentally friendly and economically viable for use.

Katrine R. Rostgaard, a PhD student at the Nano-Science Center of the University and lead author of the study said, “We have developed a method in which we optimize the analysis of the proteins. A central point of this method is the use of nanowires to hold the proteins while we analyze them. It is unique. With greater area, we can hold more proteins at once. This makes it possible to measure for multiple biomarkers simultaneously and it increases the signal, thereby providing a better quality of diagnosis.” The study was published on August 22, 2013, in the journal Nanoscale.

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