Quantification of 2,4,5-trichlorophenoxyacetic acid by fluorescence enzyme-linked immunosorbent assay with secondary antibody

Simultaneous detection of multiple biomarkers with over three orders of concentration difference using phase change nanoparticles

A big challenge for multiplexed detection of cancer biomarkers is that biomarker concentrations in body fluid differs several orders of magnitude. Existing techniques are not suitable to detect low- and high-concentration biomarkers (protein and DNA) at the same time, and liquid chromatography or electrophoresis is used to separate or purify target biomarkers before analysis. This paper describes a new broad-range biomarker assay using solid to liquid phase change nanoparticles, where a panel of metallic nanoparticles (i.e., metals and eutectic alloys) are modified with a panel of ligands to establish a one-to-one correspondence and attached onto ligand-modified substrates by forming sandwiched complexes. The melting peak and fusion enthalpy of phase change nanoparticles during thermal analysis reflect the type and concentration of biomarkers, respectively. The thermal readout condition can be adjusted in such a way that multiple biomarkers with concentration difference over 3 orders of magnitude have been simultaneously detected under the same condition.

Determinations of uranium(VI) binding properties with some metalloproteins (transferrin, albumin, metallothionein and ferritin) by fluorescence quenching

The interactions between uranium and four metalloproteins (Apo-HTf, HSA, MT and Apo-EqSF) were investigated using fluorescence quenching measurements. The combined use of a microplate spectrofluorometer and logarithmic additions of uranium into protein solutions allowed us to define the fluorescence quenching over a wide range of [U]/[Pi] ratios (from 0.05 to 1150) at physiologically relevant conditions of pH. Results showed that fluorescence from the four metalloproteins was quenched by UO(2)(2+). Stoichiometry reactions, fluorescence quenching mechanisms and complexing properties of metalloproteins, i.e. binding constants and binding sites densities, were determined using classic fluorescence quenching methods and curve-fitting software (PROSECE). It was demonstrated that in our test conditions, the metalloprotein complexation by uranium could be simulated by two specific sites (L(1) and L(2)). Results showed that the U(VI)-Apo-HTf complexation constant values (log K(1)=7.7, log K(2)=4.6) were slightly higher than those observed for U(VI)-HSA complex (log K(1)=6.1, log K(2)=4.8), U(VI)-MT complex (log K(1)=6.5, log K(2)=5.6) and U(VI)-Apo-EqsF complex (log K(1)=5.3, log K(2)=3.9). PROSECE fitting studies also showed that the complexing capacities of each protein were different: 550 moles of U(VI) are complexed by Apo-EqSF while only 28, 10 and 5 moles of U(VI) are complexed by Apo-HTf, HSA and MT, respectively.