Controlled surface functionalization using aryldiazonium salts with bulky protecting groups for the development of DNA-based sensing platforms

Abstract

Developing a comprehensive procedure for tuning the surface and interfacial properties of DNA biorecognition interfaces is crucial for a wide range of analytical applications, but proves to be a difficult task. This study aims to address the challenge by exploiting the significant advantages of surface grafting with protected aryldiazonium salts and “click” azide-alkyne functionalization reactions. In order to control the surface density of reactive alkyne moieties over a wide range, suitable for the immobilization of large biomolecules, we explored novel protecting groups such as triphenylsilyl (TPS) and tris(biphen-4-yl)silyl (TBPS), which are bulkier than the triisopropylsilyl (TIPS) group employed in previous studies. We prepare phenylethynyl-grafted glassy carbon substrates using a two-step protocol consisting in electrografting with the corresponding silyl-protected diazonium salt, followed by nucleophilic cleavage of the protecting group. Using appropriate derivatization reagents and a combination of electrochemical and surface analytical techniques, we find a strong correlation between the protecting group size and the surface coverage of phenylethynyl groups. Next, using the phenylethynyl-grafted substrates for the immobilization of an azide-modified cocaine/quinine aptamer as model bioreceptor, we demonstrate that the surface density of ssDNA decreases with increasing size of the protecting group employed in the grafting procedure. Finally, we prove that our strategy can be effectively employed to fine-tune the analytical performance of an aptasensing platform for quinine detection.