Fluorescent and electrochemical bimodal bioplatform for femtomolar detection of microRNAs in blood sera
SENSORS AND ACTUATORS B-CHEMICAL
Authors: Zayani, Riham; Rabti, Amal; Ben Aoun, Sami; Raouafi, Noureddine
Noncoding RNAs such as miRNAs (miRs) are extensively researched as a novel class of cancer biomarkers. Herein, we describe a new method to sensitively determine the levels miRNAs via dual signal readout involving competitive hybridization between the miR-21 target and its biotinylated analog towards the same thiolated DNA probe attached onto the surface of gold nanoparticles. Hybridization of the DNA probes by the biotinylated miRs followed by conjugation with streptavidin-horseradish peroxidase, which catalyzes the oxidation of o-phenylenediamine into 2,3-diaminophenazine, allows detecting the target using fluorescence and electrochemistry. The two signals varied in a miRNA concentration-dependent manner. The bioplatform has limits of detection of 15 fmol/L and 19 fmol/L (0.15 and 0.19 attomol in 20 mu L, respectively). Furthermore, it displays a wide linear calibration range varying from 19 fmol/L to 100 pmol/L and 15 fmol/L to 100 pmol/L using voltamperometry and fluorescence, respectively. The bioplatform is able to provide very low detection limits without any DNA/RNA amplification step, an excellent selectivity toward non-complementary miRs along with an acceptable distinction with a single nucleotide mismatched sequence. Finally, the method was used to determine miR-21 expression levels in blood sera from patients diagnosed with breast cancer.
Effect of whey protein isolate on the stability and antioxidant capacity of blueberry anthocyanins: A mechanistic and in vitro simulation study
Authors: Zang, Zhihuan; Chou, Shurui; Tian, Jinlong; Lang, Yuxi; Shen, Yixiao; Ran, Xulong; Gao, Ningxuan; Li, Bin
The processing stability and antioxidant capacity of blueberry anthocyanins (ANs) in the presence of whey protein isolate (WPI) were examined. WPI was found to enhance both the stability and antioxidant activity of ANs during processing and simulated in vitro digestion, especially at a concentration of 0.15 mgmL(-1). Fluorescence and ultraviolet-visible absorption spectroscopy showed that ANs were primarily stabilized by hydrophobic forces between WPI and malvidin-3-O-galactoside (M3G), the major anthocyanin monomer. Circular dichroism and Fourier-transform infrared spectroscopy confirmed that the structure of WPI changed and the microenvironments of certain amino acid residues were modulated by non-covalent binding to M3G; furthermore, fewer alpha-helices and more beta-sheets were formed. Molecular docking studies revealed that WPI, especially immunoglobulin (IgG), contributed the most to ANs stability via hydrogen bonds and hydrophobic forces according to molecular docking scores ( - 141.30 kcal/mol). These results provided an important fundamental basis for improving the stabilities of ANs in milk systems.