This production of microsystem for label-free multi detection of biomolecules is fundamental for the realization of rapid tests dedicated to laboratory diagnosis. A viable method is requires to both address capture probes and to be associates with a sensitive analysis on multiplexed platform. In this study, the method chosen for detection on electrode is cyclic voltammetry, and ferrocene was used to modify stem-loop oligonucleotides. A strategy was developed for the electroadressing of probes on gold surface. It is performed through chemistry "click" between an alkyne and an azide. This reaction may be catalyzed by maintaining the correct potential to the electrode to form an active copper oxidation state on the surface. A first small chemical entity, containing two phosphate dithiol moieties and a hexynyl moiety was synthesized by supported chemistry and grafted on gold electrode. Thereafter, various elements were immobilized by chemistry "click". Ferrocene derivative carrying an azide function was used to determine the optimal conditions for this chemistry. Then, this method has been exploited for the immobilization of proteins and fluorescent nanoparticles via the formation of biotin/streptavidin complex. DNA hybridization tests were conducted in complex environments with a detection limit determined at 100 fM Finally, this method allowed to electroaddress stem-loop oligonucleotids, designed as capture probes, modified by ferrocene. Molecular beacon (MB) probes are fluorophore- and quencher-labeled short synthetic DNAs folded in a stem-loop shape. Since the first report by Tyagi and Kramer, it has become a widely accepted tool for nucleic acid analysis and triggered a cascade of related developments in the field of molecular sensing.
The unprecedented success of MB probes stems from their ability to detect specific DNA or RNA sequences immediately after hybridization with no need to wash out the unbound probe (instantaneous format). Importantly, the hairpin structure of the probe is responsible for both the low fluorescent background and improved selectivity. This paper highlights the advantages of MB probes and discusses the approaches that address the challenges in MB probe design.įurthermore, the signal is generated in a reversible manner thus, if the analyte is removed, the signal is reduced to the background. Variations of MB-based assays tackle the problem of stem invasion, improve SNP genotyping and signal-to-noise ratio, as well as address the challenges of detecting folded RNA and DNA.Īn ultrasensitive optical biosensor for microRNA-155 (miR-155) was developed to diagnose breast cancer at early stages. At first, the probe DNA covalently bind to the negatively charged gold nanoparticles (citrate-capped AuNPs).
Then, the target miR-155 electrostatically adsorb onto the positively charged gold nanoparticles (polyethylenimine-capped AuNP) surface.
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