Bio-Nanotechnology and Nanofluidics
Guo lab and collaborators exploited the exciting nano-bio field over a few years ago. We have developed a flexible technique for selectively patterning bioactive proteins using nanoimprint, surface passivation and chemical modification, and exploiting the specificity of the biotin/streptavidin linkage. This technique achieves high throughput reproducible patterns of biologically active proteins with nanoscale resolution and high selectivity (Nano Letters. 4, 953, 2004). We have exploited a specific type of motor protein, kinesin, and to integrate such nanoscopic molecular engines into functional micro-devices. Our group developed a highly efficient method for guiding the directional transport of microtubules by confining the kinesin proteins into passivated polymer nano-tracks that are integrated with microfluidic channels (Small 1, 409, 2005). They and collaborators have obtained very encouraging results from a prototype molecular sorting device based on these developments (µTAS, 2003, Lab on a Chip, 9, 1282, 2009). Our group also developed a greatly simplified technique for fabricating large arrays of nanofluidic channels with controlled dimensions, and illustrated one biological application by stretching genomic DNAs in the nanochannels (Nano Letters. 4, 69, 2004), which may find use for single molecule detection, quick DNA sizing. Nanochannels has been studied to control ion transport. Our lab discovered ion current rectification in nanochannels with asymmetric bath ionic concentrations (Nano Lett. 7, 3165, 2007) and demonstrated nanochannel diodes that mimic the action of semiconductor diode (ACS Nano, 24, 575, 2009)
Impact: The versatile, highly specific, and biologically friendly technique for generating ultra-high resolution protein patterns will allow the diverse activities of proteins to be integrated into microfabricated devices and sensors. It also provides a unique solution to create "grey scale" protein patterns with varied densities, which will aid the study of cell adhesion and motility and enzyme-substrate interactions. The successful demonstration of molecular sorting devices powered by motor proteins will spur further investigations and new device concepts to harvest the full potential of these highly sophisticated nanostructures provided by nature with unprecedented small scale and high efficiency. The simple technique for constructing nanochannels will provide a useful fabrication tool to perform genomic, proteomic, and chemical analysis in the nanoscale. A nanofluidic device that can conduct ion current preferentially in one direction and inhibits the current flow in the opposite direction is of great interest since it may open a new way to handle molecular or ion species in fluid, and may even shed light on the mechanism of biological ionic channels.