(163c) Reusable Electrochemical Cyclodextrin Biosensor for Resveratrol Detection

In this work, a sensitive α-cyclodextrin (α-CD) based biosensor was designed for detection of resveratrol. Numerous studies have shown that CDs can form inclusion complexes with various organic and inorganic hydrophobic molecules because of their hydrophobic inner cavity and hydrophilic exterior. For that reason, CD-based biosensors have been used for detection of different analytes over the last two decades. However, to the best of our knowledge reusable CD biosensors have not yet been reported, and the current developed CD biosensors are unable to monitor the analyte concentration continuously. During the construction of these biosensors, metal electrodes are mostly coated by CD, without any additional support, and this makes the sensor disposable after each measurement. Therefore, we tried a different approach to develop a reusable CD-based biosensor by combination of self-assembled monolayers and CD supra-molecular interactions. We chose electrochemical impedance spectroscopy (EIS) as our detection technique because of its fast response and high sensitivity.

The technique presented will involve modifying a gold electrode surface with polyethylene glycol (PEG)-SH via thiol chemistry. The surface PEG brushes were then complexed with α–CD. The CD-PEG surface was exposed to different concentrations of resveratrol. We monitored the change in double layer capacitance, which is proportional to the release of CD from the PEG surface. Compared to the bare surface, sensitivity was improved. To check the reusability of the surface, after each serial dilution, the surface was reloaded with CD, and a new serial dilution was performed. It was found that CD was successfully reloaded on the PEG brushes. Attenuated total reflectance – Fourier transform infrared and X-ray photoelectron spectroscopy tests were also carried out to verify impedance results both for initial surface modification and CD reloading. As a control, we did resveratrol serial dilution with a bare surface and a modified PEG surface in which double layer capacitance stayed constant. Moreover, a time control experiment with a CD-PEG surface was carried out. In this experiment we put our modified surface in a PBS solution and measured capacitance every 5 minutes; no changes in double layer capacitance was observed in this experiment either. Finally, the capacitive response of our CD-PEG surface to cortisol was investigated. As it was predicted the α–CD surface only showed some selectivity towards cortisol. Therefore, we have created a semi-selective reusable sensor towards the detection of molecules that interact with α–CD, such as resveratrol in the range 500 pM to 20 nM.