Activity

Based on electrochemiluminescence resonance energy transfer (ERET) from Ru(bpy)32+ to graphene oxide (GO), a novel label-free solid-state ECL sensor for sensitive detection of DNA was proposed. First, Ru(bpy)32+/AuNPs was successfully prepared by using a simple and green method and characterized by transmission electron microscopy (TEM), Energy Dispersive X-ray (EDX), and UV-vis spectroscopy. PP121 Then, the Ru(bpy)32+/AuNPs colloid was assembled on the gold electrode surface for solid-state ECL film which also later could be used to immobilize thiol-derivatized, single-stranded DNA (HS-ssDNA) via Au-S interactions. The stepwise modification procedure was characterized by cyclic voltammetry(CV), electrochemical impedance spectroscopy (EIS), probe approach curves (PAC) and ECL, respectively. The resulting modified electrode was tested as ECL biosensor for DNA detection. Upon addition of GO, the strong noncovalent interaction between HS-ssDNA and GO led to ECL quenching because of ERET. When in the presence of target ssDNA (t-ssDNA), the distance between the HS-ssDNA and GO increased, which significantly hindered the ERET and, thus, resulted in the restoration of ECL. The ECL intensity of the biosensor increased linearly with t-ssDNA concentration in the range of 50-1000pM, and the detection limit is 20pM. To the best of our knowledge, this is the first application of solid-state ERET from Ru(bpy)32+ to GO and opens new opportunities for sensitive detection of biorecognition events.An analytical method was developed for the direct determination of total mercury in natural waters at low ng L-1 level by inductively coupled plasma mass spectrometry (ICP-MS). The presented method overcomes previously observed problems relating to poor spike recoveries by adding 0.12% thiourea in addition to 3% HCl to all samples and standards. The sample preparation is fast and easy to perform by the developed method since it requires only the addition of HCl and thiourea to the water samples. A very low instrument detection limit (0.4 ng L-1) was obtained without time-consuming preconcentration procedures. The accuracy and precision of the developed method were found excellent by the analysis of a certified groundwater reference material (ERM-CA615). The determined Hg concentration of 38.6 ± 0.5 ng L-1 was within the 95% confidence interval of the certified concentration of 37 ± 4 ng L-1. The analysis of natural water samples showed that total mercury levels ranged from concentrations lower than the method detection limit (2.0 ng L-1) to 10.9 ng L-1. Excellent recoveries of 96-108% for inorganic mercury (iHg) and 102-110% for methylmercury (MeHg) were obtained for spiked humic-rich natural water samples. To our knowledge, the developed method is the first ICP-MS method for the analysis of humic-rich natural water samples at ng L-1 concentrations without the need for hyphenated techniques or preconcentration procedures.Hydrophilic solids based on poly(2-hydroxyethyl methacrylate) (pHEMA) with embedded magnetic nanoparticles and amine-modified carbon nanotubes were synthesized by photopolymerization. For this purpose, an oil in water (O/W) emulsion with an aqueous/oil ratio of 60/40 was prepared where the polymerization reaction occurred in the aqueous phase due to the hydrophilicity of pHEMA and the selected nanoparticles. Variables affecting the stability and emulsion formation as well as the initiation and propagation of the polymerization were studied. The morphology of the obtained magnetic solids was characterized by SEM/EDAX in order to show the differences in presence and absence of nanoparticles within the structure. Finally, the synergic effect of both magnetic and carbon nanoparticles in the sorbent capacity of the final hydrophilic solids was evaluated through the determination of non-steroidal anti-inflammatory drugs (NSAIDs) in human urine samples. HPLC-UV was used as instrumental technique and detection limits ranged from 5 to 10 μg L-1. The precision was calculated both intra- and inter-solids (same and different synthesis batches) obtaining satisfactory RSD values of less than 13%, which indicated the robustness of the synthesis and the extraction procedure. Finally, a study with real and fortified urine samples was also carried out obtaining recovery values between 86% and 109% for target NSAIDs.Herein, a novel bimetallic MOF-818@reduced graphene oxide/multiwalled carbon nanotubes (RGO/MWCNTs) composite was successfully synthesized by a facile solvothermal method. Characterized by scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy and electrochemical measurements, MOF-818@RGO/MWCNTs composite possesses hierarchical porous structures, good electrical conductivity and abundant active sites. The MOF-818@RGO/MWCNTs/GCE exhibits excellent electrocatalytic activity to phenolic acid compounds caffeic acid (CA), chlorogenic acid (CGA) and gallic acid (GA). The sensor shows two linear ranges from 0.2 to 7 μM and 7-50 μM with a high sensitivity of 12.89 μA/μM for the detection of CA, a low detection limit of 5.7 nM and an excellent sensitivity of 12.50 μA/μM in the ranges of 0.1-3 μM and 3-20 μM for CGA detection, as well as a comparable electrochemical performance for GA. The sensor was used to detect CA, CGA and GA in biological samples and the results of quantitative recoveries for each compounds were satisfactory. We envision that the proposed strategy may stimulate extensive explorations of bimetallic MOFs with more active sites for the development of sensitive electrochemical sensors.DNA-scaffolded silver nanoclusters (DNA/AgNC) probes are widely used to detect microRNAs (miRNAs) for diagnosing diseases. However, current available DNA/AgNC probes, which primarily based on fluorescence quenching (turn-off) method, suffer from low detection accuracy caused by bio-matrix interferences. Herein, we designed a new DNA/AgNC-cDNA probe to detect miRNA based on a fluorescence enhancing (turn-on) strategy. Using miR-223, a potential biomarker of inflammatory bowel diseases (IBD), as the target miRNA, we devised the partially hybridized DNA/AgNC-cDNA fluorescent probe. The cDNA was the sequence that completely paired against miR-223 and served as a quencher to the fluorescent DNA/AgNC moiety. Upon the presence of miR-223, which could competitively bind the cDNA, then the DNA/AgNC was set free from the DNA/AgNC-cDNA complex accompanied by an increase in the fluorescence of the DNA/AgNC. Further, by fluorescence decay and polyacrylamide gel electrophoresis (PAGE) experiments, we tentatively addressed the probe working mechanism the restriction of photo-induced electron-transfer from complementary nucleobases to DNA/AgNC.