Highly selective and sensitive nucleic acid detection based on polysaccharide-functionalized silver nanoparticles

Polysaccharide-functionalized silver nanoparticles (Oc-AgNPs) with a mean diameter of 15 nm were utilized as a novel and effective fluorescence-sensing platform for nucleic acid detection. Tests on the oligonucleotide sequences associated with the human immunodeficiency virus as a model system showed that the Oc-AgNPs effectively absorbed and quenched dye-labeled single-stranded DNA through strong hydrogen bonding interactions and slight electrostatic attractive interactions. The proposed system efficiently differentiated between complementary and mismatched nucleic acid sequences with high selectivity and good reproducibility at room temperature.

Fluorescence resonance energy transfer dye-labeled probe for fluorescence-enhanced DNA detection: an effective strategy to greatly improve discrimination ability toward single-base mismatch

In this article, we report on the first use of fluorescence resonance energy transfer (FRET) dye-labeled probe for fluorescence resonance enhanced DNA detection to greatly improve discrimination ability toward single-base mismatch using conjugation polymer poly(p-phenylenediamine) nanobelts (PNs) as a sensing platform. The suggested FRET dye-labeled probe contains a 5-carboxyfluorescein (FAM) group at 5' end of the oligomer as a donor and a 6-carboxy-X-rhodamine (ROX) attached to a modified cytosine (C) base as an acceptor, which were separated by three bases. The general concept used in this DNA assay is based on adsorption of the FRET dye-labeled single-stranded DNA (ssDNA) probe by PN, which is accompanied by substantial fluorescence quenching and disappearance of FRET. The subsequent specific hybridization with its target forms a double-stranded DNA (dsDNA), resulting in desorption of the hybridized duplex from PN surface accompanied by reoccurrence of FRET and fluorescence recovery. It suggests that the discrimination ability of this FRET probe based system toward single-base mismatch is about 5.2 times that of the system based on single dye-labeled probe based system.

Poly(m-phenylenediamine) nanospheres and nanorods: selective synthesis and their application for multiplex nucleic acid detection

In this paper, we demonstrate for the first time that poly(m-phenylenediamine) (PMPD) nanospheres and nanorods can be selectively synthesized via chemical oxidation polymerization of m-phenylenediamine (MPD) monomers using ammonium persulfate (APS) as an oxidant at room temperature. It suggests that the pH value plays a critical role in controlling the the morphology of the nanostructures and fast polymerization rate favors the anisotropic growth of PMPD under homogeneous nucleation condition. We further demonstrate that such PMPD nanostructures can be used as an effective fluorescent sensing platform for multiplex nucleic acid detection. A detection limit as low as 50 pM and a high selectivity down to single-base mismatch could be achieved. The fluorescence quenching is attributed to photoinduced electron transfer from nitrogen atom in PMPD to excited fluorophore. Most importantly, the successful use of this sensing platform in human blood serum system is also demonstrated.