Reversible Electroaddressing of Self-assembling Amino-Acid Conjugates

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 nano-biotechnology. 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 fl uorenyl-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 microfl uidic 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.