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Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.

ABSTRACT: Electrochemical impedance spectroscopy (EIS) is used to compare the apparent electron transfer rate constant (kapp) for a series of alkanethiol and of carbohydrate-terminated alkanethiol self-assembled monolayers (SAMs) on both flat gold and on nanoporous gold (np-Au). Using the surface area for np-Au determined by oxide stripping, the values of kapp for the alkanethiol modified np-Au are initially over two orders of magnitude smaller than the values found on flat Au. This result provides evidence that the diffusing redox probe Fe(CN)63-/4- only accesses a fraction of the np-Au surface after alkanethiol modification suggesting very limited wetting of the internal pores due to the hydrophobic nature of these surfaces. In contrast, for np-Au modified by carbohydrate-terminated (mannose or galactose) alkanethiols the values of kapp are about 10-40 fold smaller than on flat gold, suggesting more extensive access of the diffusing redox probe within the pores and better but still incomplete wetting, a result also found for modification of np-Au with mercaptododecanoic acid. A short chain PEG thiol derivative is found to result in a comparison of kapp values that suggests nearly complete wetting of the internal pores for this highly hydrophilic derivative. These results are of significance for the potential applications of SAM modified np-Au in electrochemical sensors, especially for those based on carbohydrate-protein recognition, or those of np-Au modified by SAMs with polar terminal groups.

SUBMITTER: Sharma A

PROVIDER: S-EPMC5388453 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.

Sharma Abeera A Bhattarai Jay K JK Nigudkar Swati S SS Pistorio Salvatore G SG Demchenko Alexei V AV Stine Keith J KJ

Journal of electroanalytical chemistry (Lausanne, Switzerland) 20161011

Electrochemical impedance spectroscopy (EIS) is used to compare the apparent electron transfer rate constant (kapp) for a series of alkanethiol and of carbohydrate-terminated alkanethiol self-assembled monolayers (SAMs) on both flat gold and on nanoporous gold (np-Au). Using the surface area for np-Au determined by oxide stripping, the values of kapp for the alkanethiol modified np-Au are initially over two orders of magnitude smaller than the values found on ...[more]

PMID: 28413373

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Project description:BackgroundDNA hybridization is at the basis of most current technologies for genotyping and sequencing, due to the unique properties of DNA base-pairing that guarantee a high grade of selectivity. Nonetheless the presence of single base mismatches or not perfectly matched sequences can affect the response of the devices and the major challenge is, nowadays, to distinguish a mismatch of a single base and, at the same time, unequivocally differentiate devices read-out of fully and partially matching sequences.ResultsWe present here two platforms based on different sensing strategies, to detect mismatched and/or perfectly matched complementary DNA strands hybridization into ssDNA oligonucleotide monolayers. The first platform exploits atomic force microscopy-based nanolithography to create ssDNA nano-arrays on gold surfaces. AFM topography measurements then monitor the variation of height of the nanostructures upon biorecognition and then follow annealing at different temperatures. This strategy allowed us to clearly detect the presence of mismatches. The second strategy exploits the change in capacitance at the interface between an ssDNA-functionalized gold electrode and the solution due to the hybridization process in a miniaturized electrochemical cell. Through electrochemical impedance spectroscopy measurements on extended ssDNA self-assembled monolayers we followed in real-time the variation of capacitance, being able to distinguish, through the difference in hybridization kinetics, not only the presence of single, double or triple mismatches in the complementary sequence, but also the position of the mismatched base pair with respect to the electrode surface.ConclusionWe demonstrate here two platforms based on different sensing strategies as sensitive and selective tools to discriminate mismatches. Our assays are ready for parallelization and can be used in the detection and quantification of single nucleotide mismatches in microRNAs or in genomic DNA.

Dataset Information

Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.

Publications

Electrochemical impedance spectroscopy study of carbohydrate-terminated alkanethiol monolayers on nanoporous gold: Implications for pore wetting.

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