Real-time monitoring of nanomolar binding to a cyclodextrin monolayer immobilized on a Si/SiO2/novolac surface using white light reflectance spectroscopy: The case of triclosan

The monitoring of the antibacterial agent triclosan binding at nanomolar concentration from an aqueous solution by employing a well-packed monolayer with a predetermined single orientation made of specifically synthesized 2,3-dimethyl-6-(undec-10-enamide)-6-deoxy-β-cyclodextrin (DMBUA) on a silicon wafer (Si/SiO2) coated with a novolac resin is reported. A white light reflectance spectroscopy (WLRS) setup was used for the real-time monitoring of the DMBUA deposition and triclosan binding processes. Film thicknesses obtained by WLRS were in very good agreement with the ones measured by X-ray reflectivity (XRR) experiments. Triclosan binds strongly to the DMBUA monolayer (log Kassoc = 6.68). NMR studies in aqueous solution indicated that the chlorophenolyl ring rather than the dichlorophenyl ring is preferentially inserted into DMBUA cups. The current detecting system that requires no tedious surface chemistry, no thiolated cyclodextrins, no gold surfaces, and no expensive equipment may be useful in capturing small molecules and may permit various applications, e.g., preparation of antimicrobial surfaces.

A stable, well-packed undecenyl-cyclodextrin (DMBUA) monolayer on Si/SiO2/novolac resin substrate that acts as the interferometer detects triclosan from a 10 nM aqueous solution in a reflectance spectrometer.Figure optionsDownload high-quality image (141 K)Download as PowerPoint slideHighlights
► Detection of the antibacterial agent triclosan at nM concentration is achieved.
► A well-packed monolayer of a modified cyclodextrin (DMBUA) is the detecting layer.
► A white light reflectance spectroscopy setup is used.
► Real-time monitoring of the DMBUA deposition and triclosan binding is achieved.
► Tedious surface chemistry, gold surfaces, or expensive equipment not required.