title: Synthetic oligonucleotides: AFM characterisation and electroanalytical studies.
abstract: One of the most important steps in designing more sensitive and stable DNA based biosensors is the immobilisation procedure of the nucleic acid probes on the transducer surface, while maintaining their conformational flexibility. MAC Mode AFM images in air demonstrated that the oligonucleotide sequences adsorb spontaneously on the electrode surface, showing the existence of pores in the adsorbed layer that reveal big parts of the electrode surface, which enables non-specific adsorption of other molecules on the uncovered areas. The electrostatic immobilisation onto a glassy carbon electrode followed by hybridisation with a complementary sequence and control with a non-complementary sequence was studied using differential pulse voltammetry and electrochemical impedance spectroscopy. Changes in the oxidation currents of guanosine and adenosine were observed after hybridisation events as well as after control experiments. Modification of the double layer capacitance that took place after hybridisation or control experiments showed that non-specific adsorption of complementary or non-complementary sequences occur allowing the formation of a mixed multilayer.
authors.affiliation: Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra, Portugal. brett@ci.uc.pt
authors.forename: A M
authors.initials: AM
authors.lastname: Oliveira Brett
authors.forename: A-M
authors.initials: AM
authors.lastname: Chiorcea Paquim
authors.forename: V
authors.initials: V
authors.lastname: Diculescu
authors.forename: T S
authors.initials: TS
authors.lastname: Oretskaya
mesh_terms: D015374:Biosensing Techniques; D017097:Electric Impedance; D004566:Electrodes; D018625:Microscopy, Atomic Force; D009693:Nucleic Acid Hybridization; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D015345:Oligonucleotide Probes / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: D009838:Oligodeoxyribonucleotides; D015345:Oligonucleotide Probes