Modulating fluorescence anisotropy of terminally labeled double-stranded DNA via the interaction between dye and nucleotides for rational design of DNA recognition based applications.

Effective signal enhancement for fluorescence anisotropy in a simple manner is most desirable for fluorescence anisotropy method development. This work aimed to provide insights into the fluorescence anisotropy of terminally labeled double-stranded DNA (dsDNA) to facilitate a facile and universal design strategy for DNA recognition based applications. We demonstrated that fluorescence anisotropy of dsDNA could be regulated by the nature of dyes, the molecular volume, and the end structure of dsDNA.

The electron-transfer based interaction between transition metal ions and photoluminescent graphene quantum dots (GQDs): a platform for metal ion sensing.

The electron-transfer based quenching effect of commonly encountered transition metal ions on the photoluminescence of grapheme quantum dots (GQDs) was for the first time investigated, and was found to be associated with electron configuration of the individual metal ion. Ethylene diamine tetraacetic acid (EDTA), the metal ion chelator, can competitively interact with metal ions to recover the quenched photoluminescence of GQDs. Basically, metal ions with empty or completely filled d orbits could not quench the photoluminescence of GQDs, but this quenching effect was observed for the metal ions with partly filled d orbits.

Gold nanoparticle enhanced fluorescence anisotropy for the assay of single nucleotide polymorphisms (SNPs) based on toehold-mediated strand-displacement reaction.

We developed a highly differentiating, homogeneous gold nanoparticle (AuNP) enhanced fluorescence anisotropic method for single nucleotide polymorphism (SNP) detection at nanomolar level using toehold-mediated strand-displacement reaction. The template strand, containing a toehold domain with an allele-specific site, was immobilized on the surface of AuNPs, and the solution fluorescence anisotropy was markedly enhanced when the fluorescein-labeled blocking DNA was attached to the AuNP via hybridization. Strand-displacement by the target ssDNA strand resulted in detachment of fluorescein-labeled DNA from AuNPs, and thus decreased fluorescence anisotropy.

The homogeneous fluorescence anisotropic sensing of salivary lysozyme using the 6-carboxyfluorescein-labeled DNA aptamer.

A simple and sensitive fluorescence anisotropy method was developed for lysozyme, employing the coupling of fluorophore, 6-carboxyfluorescein (FAM), with lysozyme upon recognition between the target molecule and its DNA aptamer. It was found in this study that the rotational dynamic of the detecting system is crucial to obtain a high anisotropy signal that cannot always be achieved by simply increasing the molecular volume, because molecular volume increase may not be able to efficiently retard the rotational movement of the fluorophore. FAM was selected as the label of the ssDNA aptamer to effectively facilitate the change of the fluorophore from a primarily independent segmental movement to slow global rotation.

Novel method to measure enamel surface porosity with hydrogen peroxide bleaching.

Purpose: To establish methods to quantitate the physical surface change, not the chemical color bleaching change, of enamel occurring with hydrogen peroxide treatment in solution and commercially available plastic strips.

Methods: Bovine enamel was polished to a sound, uniform, optical flat, white subsurface that was used as the initial substrate for all substrate modification, treatment and instrumental measurement using digital photography-image analysis, SEM and profilometry. Sound enamel was treated with 10, 20 and 30% solutions of hydrogen peroxide.

Determination of human urinary kanamycin in one step using urea-enhanced surface plasmon resonance light-scattering of gold nanoparticles.

The purpose of this study was to establish a simple, sensitive analytical method for kanamycin (KANA) in human urine. Enhancement of the plasmon resonance light-scattering (PRLS) of gold nanoparticles (AuNPs) by KANA provided the basis for this analytical method. At pH 6.