Search

A facile and rapid colorimetric approach was described for selective and sensitive determination of adenosine triphosphate (ATP) based on a hairpin aptamer probe and the anti-aggregation of AuNPs. Poly(diallyldimethylammonium chloride) (PDDA) can induce the aggregation of AuNPs due to the electrostatic interaction causing a red to blue color change. Upon the addition of ATP, aptamer-based hairpin probe is opened and releases flexible ssDNA ends. The released flexible ssDNA ends can interact with PDDA and prevent PDDA-induced AuNPs aggregation. Thus, a visible color change from blue to red and a decrease in the absorption ratio (A 610 /A 520) are observed. Under the optimal conditions, the hairpin aptamer-based colorimetric assay exhibits high sensibility and selectivity for the detection of ATP with a detection limit of 1.7 nM. Moreover, this assay is successfully used in the rapid determination of ATP in spiked human serum samples with good recoveries in the range of 102.88 to 104.07%. Schematic illustration of the colorimetric assay based on the anti-aggregation of AuNPs for the ATP detection. Flexible ssDNA ends were released due to the forming of the aptamer-ATP complexes, which electrostatically hybridize to PDDA to form a duplex and prevents the PDDA-induced aggregation of AuNPs with a color change from blue to red. Unlabelled Image • It has a high sensitivity with a detection limit of 1.7 nM for ATP. Furthermore, the coupling a hairpin-like DNA probe and anti-aggregation of AuNPs guarantees the good selectivity of the assay to ATP and eliminates the effect of non-specific interference. • It is a more universal method that can be used to study other targets by simply changing the sequences of the corresponding aptamers of the hairpin-like DNA probe. [ABSTRACT FROM AUTHOR]

In this work, a rapid, simple and sensitive colorimetric sensor for simultaneous (or respective) detection of Cr 3 + and Pb 2 + using tyrosine functionalized gold nanoparticles (AuNPs Tyr ) has been developed. Tyrosine, a natural and zwitterionic amino acid, could be as a reducing and capping agent to synthesise AuNPs and allow for the simultaneous and selective detection of Cr 3 + and Pb 2 + . Upon the addition of Cr 3 + or Pb 2 + (a combination of them), the color of AuNPs Tyr solution changes from red to blue grey and the characteristic surface plasmon resonance (SPR) band is red-shifted to 580 nm due to the aggregation of AuNPs. Interestingly, the aggregated AuNPs Tyr can be regnerated and recycled by removing Pb 2 + and Cr 3 + . Even after 3 rounds, AuNPs Tyr show almost the same A 580 nm / A 520 nm value for the assays of Pb 2 + and Cr 3 + , indicating the good recyclability of the colorimetric sensor. The responding time (within 1 min) and sensitivity of the colorimetric sensor are largely improved after the addition of 0.1 M NaCl. Moreover, the AuNPs Tyr aggregated by Cr 3 + or Pb 2 + (a combination of them) show excellent selectivity compared to other metal ions (Cr 3 + , Pb 2 + , Fe 2 + ,Cu 2 + ,Zn 2 + ,Cr 6 + ,Ni 2 + ,Co 2 + ,Hg 2 + ,Mn 2 + ,Mg 2 + ,Ca 2 + ,Cd 2 + ). More importantly, the developed sensor manifests good stability at room temperature for 3 months, which has been successfully used to determine Cr 3 + and Pb 2 + in the real water samples with a high sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Background: Recently, some research results showed that the circulating DNA in serum or plasma had potential for the molecular diagnosis and prognosis of certain cancers. Several methods have been employed for the quantification of circulating DNA. However, the circulating DNA levels obtained by various methods exhibited considerable differences. Additionally, these methods were labor-extensive and time-consuming, and not suitable for the quantification of circulating DNA in numerous samples due to the use of commercial DNA extraction kits for the purification of circulating DNA. We presented a new method for the quantification of circulating DNA in sera by capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF). Methods: In the present work, we want to make comparison between CZE-LIF assay and real time PCR for the quantification of circulating DNA levels. Linearity, intra and inter variability of two methods were evaluated. Results: The intra and inter variability of circulating DNA quantification by real-time PCR were 7.3% and 14.92%, respectively. In CZE assay the intra and inter variability were 4.19% and 6.91%, respectively. The R.S.D. values of the same coated capillary and different coated capillaries were 5.14% and 9.02%, respectively. Our data showed that the circulating DNA levels obtained by two methods had a good correlation. Moreover, we further confirmed that blood samples collection, serum preparation and other treatment procedures had a significant impact on the DNA levels in sera. Conclusion: Our data further illustrated that CZE-LIF is a simple, rapid and sensitive method for the quantification of circulating DNA in human sera, and well suitable for the analysis of a large number of samples in clinical diagnosis. [Copyright &y& Elsevier]

Activation mechanism of the nanoplatform AuNCs@MnO 2 nanosheets for GSH detection and intracellular imaging. [Display omitted] • A novel GSH-switched fluorescence nanoprobe has been constructed based on the integration between the inner filter effect of MnO 2 nanosheets and GSH-induced enhanced fluorescence of AuNCs. • The nanoplatform exhibits a high sensitivity for the detection of GSH with a low limit detection of 68 nM. • The nanoplatform achieves outstanding selectivity towards intracellular GSH over cysteine, homocysteine and ascorbic acid. • And that, it can selectively monitoring the GSH in human serum and the fluorescence imaging of endogenous GSH in living cell. Glutathione (GSH) plays a critical role in biological defense system and is associated with numerous human pathologies. However, it still remains a challenge for fluorescent detection of GSH over cysteine (Cys) and homocysteine (Hcy) because of their similar structures. In this work, MnO 2 nanosheets can efficiently quench the fluorescence of gold nanoclusters (Met-AuNCs) prepared by blending methionine and HAuCl 4 owing to their superior absorption capability. However, GSH can reduce MnO 2 nanosheets into Mn2+ which leads to the fluorescence recovery of Met-AuNCs. More intriguingly, GSH can dramatically and selectively enhance the fluorescence intensity of Met-AuNCs. Hence, a low background, ultrasensitive fluorescent detection of GSH was obtained with a detection limit of 68 nM. Moreover, the assay has been successfully used for GSH detection in human serum samples and cellular imaging with high selectivity over Cys and Hcy. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present a universal, highly efficient and sensitive method for the characterization of quantum dot (QD) bioconjugates based on capillary electrophoresis with laser-induced fluorescent (LIF) detection. We first prepared CdTe QDs in aqueous phase by a chemical route with mercaptopropionic acid as a ligand, and then were coupled to certain proteins using bifunctional linkage reagent or electrostatic attraction. The QD bioconjugates were characterized by capillary electrophoresis with LIF detection. We found that QD bioconjugates were efficiently separated with free QDs by the optimization of buffer pH. Furthermore, we found that ultrafiltration was an effective and simple approach to purify QD conjugates with bovine serum albumin (BSA). Due to their broad absorption spectra and size dependent emission wavelength tunability, QDs can be excited to emit different colour fluorescence using a single wavelength laser source, and therefore, we believe that CE with LIF detection will become a universal and efficient tool for the characterization of QD bioconjugates. [Copyright &y& Elsevier]