Redox-activating dip-pen nanolithography (RA-DPN)

Northwestern University, Department of Chemistry, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society (Impact Factor: 12.11). 02/2009; 131(3):922-3. DOI: 10.1021/ja809107n
Source: PubMed


Dip pen nanolithography (DPN) involves the direct transfer of an ink from a coated atomic force microscope (AFM) tip to a substrate of interest and uses as many as 55,000 pens to form arbitrary patterns of alkanethiols, oligonucleotides, proteins, and viruses. Two limitations of DPN are the difficulty in transporting high molecular weight inks and the need to optimize individually the transport rates and tip inking methods of each molecule. As an alternative strategy that circumvents these two challenges, a method termed redox activating DPN (RA-DPN) is reported. In this strategy, an electrochemically active, quinone functionalized surface is toggled from the reduced hydroquinone form to the oxidized benzoquinone form by the delivery of an oxidant by DPN. While the benzoquinone form is susceptible to nucleophilic attack in Michael-type additions, hydroquinone is not and acts as a passivating agent. Because both forms of the quinone are kinetically stable, the patterned surface can be immersed in a solution of a target containing any strong nucleophile, which will react only where the benzoquinone form persists on the surface. For proof-of-concept demonstrations, quinone surfaces were patterned by the delivery of the oxidant cerric ammonium nitrate and were immersed in solutions of AF549 labeled cholera toxin beta subunit or oligonucleotides modified at the 5' end with an amine and the 3' end with a fluorophore. Fluorescent patterns of both the proteins and oligonucleotides were observed by epifluorescence microscopy. Additionally, RA-DPN maintains the advantageous ability of DPN to control feature size by varying the dwell time of the tip on the surface, and variation of this parameter has resulted in feature sizes as small as 165 nm. With this resolution, patterns of 50,000 spots could be made in a 100 x 100 microm(2) grid.

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    • "The ability to pattern surfaces with sub-100 nm resolution has been a driving force in nanotechnology fueled by the semiconductor industry's desire to continually shrink the size of bulk materials, and by new capabilities for biological experiments made possible through high-density biomolecule arrays. In this respect, DPN (Braunschweig, Huo, and Mirkin 2009; Piner et al. 1999; Salaita, Wang, and Mirkin 2007) has become a commercial technique for direct-write molecular printing; it is capable of patterning surfaces with sub-50 nm feature size (Figure 3.6). As a patterning tool, many applications have been explored, and DPN has been used for fundamental transport studies (Rozhok, Piner, and Mirkin 2003; Giam, Wang, and Mirkin 2009), as a fabrication technique for photomasks (Jae-Won Jang 2009), and as a method of creating biological screening devices, including an assay for HIV virus p24 antigen in serum samples (Lee 2004). "
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