Photoswitchabk antigen-antibody interactions studied by impedance spectroscopy

Fernando Patolsky, Boris Filanovsky, Eugenii Katz, Itamar Willner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

104 Scopus citations

Abstract

A thiolated dinitrospiropyran (1a) is assembled as a monolayer onto a Au electrode. The monolayer exhibits reversible photoisomerizable properties, and irradiation of the 1a monolayer state, 360 nm < λ < 380 nm, yields the protonated merocyanine (1b) monolayer state, whereas illumination of the latter monolayer electrode, λ > 495 nm, regenerates the 1a monolayer electrode. The 1a monolayer interface acts as antigen for the dinitrophenyl antibody, DNP-Ab, while the 1b state lacks an affinity for DNP-Ab. This stimulates the association of the antibody to the 1a monolayer interface, while photoisomerization of the monolayer to the 1b state allows one to wash off DNP-Ab and regenerate the 1a monolayer assembly by a secondary illumination process. The photoisomerization of the monolayer interface and the binding or dissociation of DNP-Ab to and from the photoisomerizable monolayer are studied by impedance spectroscopy, in the presence or absence of a solubilized redox probe. The derived equivalent circuits enable us to characterize the monolayer parameters associated with the photoisomerization and the interactions of DNP-Ab with the monolayer. The non-Faradaic impedance measurements reveal only capacitance changes of the double-layer interface as a result of photoisomerization and the association of DNP-Ab to the monolayer. Faradaic impedance measurements using [Fe(CN)6]3-/4- as a molecular redox probe or ferrocene-tethered glucose oxidase, GOx-Fc, and glucose as a bioelectrocatalytic redox probe, allow for the determination of the electron-transfer resistance, the electrontransfer rate constants, and the characteristic time constants of the equivalent circuits corresponding to the different states of the photoisomerizable monolayer in the absence and presence of DNP-Ab. Faradaic impedance appears to be an effective transduction signal for the photoisomerization occurring upon optical activation of the monolayer and for the photostimulated binding and dissociation of DNP-Ab to and from the monolayer, respectively. The system represents an optoelectronic "OR" gate.

Original languageEnglish
Pages (from-to)10359-10367
Number of pages9
JournalJournal of Physical Chemistry B
Volume102
Issue number50
StatePublished - 10 Dec 1998

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