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

Area of Science:

• Nanotechnology
• Surface Chemistry
• Biomolecular Engineering

Background:

• Dip pen nanolithography (DPN) is a technique for patterning surfaces using an atomic force microscope (AFM) tip.
• DPN faces challenges with high molecular weight inks and molecule-specific transport optimization.
• Existing DPN methods struggle with efficient transfer of large biomolecules like proteins and viruses.

Purpose of the Study:

• To introduce a novel DPN strategy, redox activating DPN (RA-DPN), to overcome limitations of traditional DPN.
• To enable the patterning of high molecular weight biomolecules that are difficult to transport with conventional DPN.
• To demonstrate a versatile method for creating high-resolution patterns on functionalized surfaces.

Main Methods:

• RA-DPN utilizes a quinone-functionalized surface that is switched between reduced (hydroquinone) and oxidized (benzoquinone) states.
• An oxidant is delivered via DPN to locally convert hydroquinone to benzoquinone, creating reactive sites.
• The patterned surface is then immersed in a solution of target nucleophiles (proteins, oligonucleotides) that react specifically with the benzoquinone form.

Main Results:

• Successful patterning of AF549-labeled cholera toxin beta subunit and amine-modified oligonucleotides was achieved.
• Fluorescent patterns of proteins and oligonucleotides were visualized using epifluorescence microscopy.
• RA-DPN demonstrated control over feature size, achieving resolutions as small as 165 nm.
• High-density patterns of 50,000 spots within a 100 x 100 micrometer grid were created.

Conclusions:

• RA-DPN offers a robust alternative to DPN for patterning diverse molecules, including challenging high molecular weight biomolecules.
• The method provides precise control over patterning and feature size, enabling high-resolution nanoscale fabrication.
• RA-DPN significantly expands the scope of DPN applications in fields like biosensing and materials science.