RESUMEN
A highly specific and sensitive isothermal method for mercury detection using DNA-conjugated upconversion nanoparticles is reported. A single-stranded DNA containing thymine bases, used as the Hg2+-capturing element through the formation of thymine-Hg2+-thymine complex, is covalently attached to the NaYF4: Yb3+, Tm3+ nanoparticles. Luminescence resonance energy transfer takes place between the NaYF4: Yb3+, Tm3+ nanoparticles as donor and DNA-intercalating SYBR Green I as the acceptor upon excitation of 980â¯nm. The sensitivity and selectivity toward Hg2+ are enhanced using the nicking enzyme, Nt. Alwl, which leads to signal amplification. By monitoring the ratio of acceptor emission to a reference peak, the presence of Hg2+ ions are quantitatively determined with a lower detection limit of 0.14â¯nM, which is much lower than the US Environmental Protection Agency (EPA) limit of Hg2+ in drinking water.
Asunto(s)
ADN/química , Mercurio/análisis , Nanopartículas/química , Técnicas de Amplificación de Ácido Nucleico , Agua Potable/química , Transferencia Resonante de Energía de FluorescenciaRESUMEN
We present a proof-of-concept "on-off" detection scheme, which uses gadolinium phthalocyanine (GdTcPc)-grafted silica nanoparticles as paramagnetic centers, capable of modifying the transverse relaxation time (T2) of water protons in solution. A DNA strand (as probe) was conjugated to the GdTcPc to act as a recognition element. In the presence of the target DNA, which was complementary to the probe, an increase in the T2 value was detected, with magnitude proportional to the target DNA concentration. The linear range was observed from 30 to 140â¯nM, with limit of detection of 15â¯nM. The developed nuclear relaxation-based detection scheme is shown to be a simple, fast and selective method to detect DNA and could be useful in point-of-care diagnostic applications.
Asunto(s)
Nanopartículas/química , Oligonucleótidos/análisis , Gadolinio/química , Indoles/química , Isoindoles , Estructura Molecular , Dióxido de Silicio/químicaRESUMEN
A simple and low cost colorimetric method, requiring no instrumentation, is presented for the detection of fructose in human semen, a marker of seminal vesicle function. In this study we have synthesized a novel gold nanoparticle (AuNP) based sensor, named as fructose blue, by co-functionalizing AuNPs with 3-aminophenyl boronic acid (APB) and L-glutamic acid-(2,2,2)-trichloroethyl ester (GTE). The red-shift in the plasmon absorption spectra of fructose blue with different fructose concentrations accompanied by colour change of the solution from red to blue is the principle applied here for the estimation of fructose. The novel co-functionalized nanoparticles (NPs) have better colour change response for fructose than that of the earlier reported fructose sensors based on AuNPs functionalized by the APB moiety alone. The proposed method showed linearity in the range of 0.5-6 mg/mL with a detection limit of 0.3 mg/mL, and exhibits excellent selectivity for fructose over a collection of sugars. The method was successfully applied for detection of fructose in real samples of semen and agrees well with values obtained from conventional methods. The method depicted here for the detection of semen fructose is indeed superior to the existing methods in the sense that it can be performed at home as a preliminary self-screening test by patients suspecting infertility for warranting further medical attention and provides privacy also. Moreover the method is important, particularly in third world countries where high-tech diagnostic aids are inaccessible to the bulk of the population.