Simultaneous Electroreduction of Different Diazonium Salts for Direct Electrochemical DNA Biosensor Development

An innovative method for controlled synthesis of bicomponent monolayer films obtained by reduction of diazonium

This study presents a novel method based on the electrochemical co-reduction of two aryldiazonium salts, enabling the synthesis of controlled two-component monolayer thin films on carbon in a single step. By introducing a 12-carbon alkyl chain as a spacer between the aryldiazonium function and the functional group, precise control over film thickness and composition was achieved. The alkyl chain effectively standardizes the reduction potential, enabling the equalization of reactivity and precise stoichiometric control. Experimental results from spectroscopic, electrochemical, and X-ray photoelectron spectroscopy analyses validate the effectiveness of the method in controlling the composition of the mixed layers.

Surface grafting of poly-L-lysine via diazonium chemistry to enhance cell adhesion to biomedical electrodes

The ability to study and regulate cell behavior at a biomaterial interface requires a strict control over its surface chemistry. Significance of studying cell adhesion in vitro and in vivo has become increasingly important, particularly in the field of tissue engineering and regenerative medicine. A promising surface modification route assumes using organic layers prepared by the method of electrografting of diazonium salts and their further functionalization with biologically active molecules as cell adhesion promoters. This work reports the modification of platinum electrodes with selected diazonium salts and poly-L-lysine to increase the number of sites available for cell adhesion. As-modified electrodes were characterized in terms of their chemical and morphological properties, as well as wettability. In order to monitor the process of cell attachment, biofunctionalized electrodes were used as substrates for culturing human neuroblastoma SH-SY5Y cells. The experiments revealed that cell adhesion is favored on the surface of diazonium-modified and poly-L-lysine coated electrodes, indicating proposed modification route as a valuable strategy enhancing the integration between bioelectronic devices and neural cells.

Grafting of Diazonium Salts on Surfaces: Application to Biosensors

This review is divided into two parts; the first one summarizes the main features of surface modification by diazonium salts with a focus on most recent advances, while the second part deals with diazonium-based biosensors including small molecules of biological interest, proteins, and nucleic acids.

Influence of amine and thiol modifications at the 3' ends of single stranded DNA molecules on their adsorption on gold surface and the efficiency of their hybridization

Adsorption of molecules of DNA (deoxyribonucleic acid) or modified DNA on gold surfaces is often the first step in construction of many various biosensors, including biosensors for detection of DNA with a particular sequence. In this work we study the influence of amine and thiol modifications at the 3' ends of single stranded DNA (ssDNA) molecules on their adsorption on the surface of gold substrates and on the efficiency of hybridization of immobilized DNA with the complementary single stranded DNA. The characterization of formed layers has been carried out using infrared spectroscopy and atomic force microscopy. As model single stranded DNA we used DNA containing 20 adenine bases, whereas the complementary DNA contained 20 thymine bases. We found that the bands in polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) spectra of layers formed from thiol-modified DNA are significantly narrower and sharper, indicating their higher regularity in the orientation of DNA on gold surface when using thiol linker. Also, hybridization of the layer of thiol-modified DNA containing 20 adenine bases with the respective DNA containing thymine bases leads to formation of much more organized structures than in the case of unmodified DNA or DNA with the amine linker. We conclude that the thiol-modified ssDNA is more promising for the preparation of biosensors, in comparison with the amine-modified or unmodified ssDNA. We have also found that the above-mentioned modifications at the 3' end of ssDNA significantly influence the IR spectrum (and hence the structure) of polycrystalline films formed from such compounds, even though adsorbed fragments contain less than 5% of the DNA chain. This effect should be taken into account when comparing IR spectra of various polycrystalline films formed from modified and unmodified DNA.

Grafting of a peptide probe for Prostate-Specific Antigen detection using diazonium electroreduction and click chemistry

The main objective of this work was to validate a label-free electrochemical method of protein detection using peptides as capture probes. As a proof-of-concept, we used a 7 amino acids sequence (HSSKLQL) specific for Prostate Specific Antigen. We investigated various electrografting conditions of two anilines (2-[(4-aminophenyl)sulfanyl]-8-hydroxy-1,4-naphthoquinone and 4-azidoaniline) further converted in situ into their corresponding diazonium salts on glassy carbon electrodes. It was demonstrated that the best method to obtain a mixed layer is the simultaneous electroreduction of the two diazonium salts. 4-azidoaniline was used to covalently immobilize the ethynyl-functionalized peptide probe by click coupling, and the hydroxynaphthoquinone derivative plays the role of electrochemical transducer of the peptide-protein recognition. The proteolytic activity of PSA towards a small peptide substrate carrying streptavidin at its distal end was also investigated to design an original sensing architecture leading to a reagentless, label free, and "signal-on" PSA sensor. Without optimization, the limit of quantification can be estimated in the nM to pM range.