Reversible Electroaddressing of Self-assembling Amino-Acid Conjugates

• Published in: Advanced functional materials 2011-05, Vol.21 (9), p.1575-1580
• Main Authors: Liu, Yi, Kim, Eunkyoung, Ulijn, Rein V., Bentley, William E., Payne, Gregory F.
• Format: Article
• Language: English
• Subjects: electroaddressing; Fmoc-peptides; hydrogels; microfluidic; pH-responsive materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201002020

The triggered assembly of organic and biological materials in response to imposed electrical signals (i.e., electroaddressing) provides interesting opportunities for applications in molecular electronics, biosensing and nanobiotechnology. Recent studies have shown that the conjugation of aromatic moieties to short peptides often yields hydrogelator compounds that can be triggered to self‐assemble over a hierarchy of length scales in response to a reduction in pH. Here, we examined the capabilities of fluorenyl‐9‐methoxycarbonyl‐phenylalanine (Fmoc‐Phe) to electrodeposit in response to an electrochemically‐induced pH gradient generated at the anode surface. We report that the electrodeposition of Fmoc‐Phe; is rapid (minutes), can be spatially controlled in normal and lateral directions, and can be reversed by applying a brief cathodic current. Further more, we show that Fmoc‐Phe can be simultaneously deposited on one electrode address (anode) while it is being cathodically stripped from a separate electrode address of the same chip. Finally, we demonstrate that these capabilities can be extended for electroaddressing within microfluidic channels. The reversible assembly/disassembly of molecular gelators (Fmoc‐amino acids and Fmoc‐peptides) in response to spatiotemporally imposed electrical signals offers unique opportunities for electroaddressing that should be especially valuable for lab‐on‐a‐chip applications. pH‐responsive Fmoc‐phenylalanine can be reversibly assembled (i.e., electrodeposited) in response to anodic signals and disassembled (i.e., dissolved) in response to cathodic signals. Fmoc‐phenylalanine assembly/disassembly on patterned electrode addresses is rapid, spatially‐controllable, programmable, and can be achieved in a covered microfluidic channel. Reversible electroaddressing should be especially useful for enlisting localized electrical signals in lab‐on‐a‐chip applications.