Transport and detection of unlabeled nucleotide targets by microtubules functionalized with molecular beacons.

Shrinking biosensors down to microscale dimensions enables increases in sensitivity and the ability to analyze minute samples such as the contents of individual cells. The goal of the present study is to create mobile microscale biosensors by attaching molecular beacons to microtubules and using kinesin molecular motors to transport these functionalized microtubules across two-dimensional surfaces. Previous work has shown that microfluidic channels can be functionalized with kinesin motors such that microtubules can be transported and directed through these channels without the need for external power or pressure-driven pumping. In this work, we show that molecular beacons can be attached to microtubules such that both the fluorescence reporting capability of the beacon and the motility of the microtubules are retained. These molecular beacon-functionalized microtubules were able to bind ssDNA target sequences, transport them across surfaces, and report their presence by an increase in fluorescence that was detected by fluorescence microscopy. This work is an important step toward creating hybrid microdevices for sensitive virus detection or analyzing mRNA profiles of individual cells.