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Gas generation-based immunoassay is considered an attractive biosensing platform for the detection of biomarkers by incorporating the target recognition event with a catalyzed gas-generating reaction. Herein, an optical gas pressure sensor based on a silver/polydimethylsiloxane (Ag/PDMS) bilayer system was designed as a signal transducer to read the concentration of the detection target alpha-fetoprotein (AFP) quantitatively. In this proposed pressure-based assay, silicon dioxide (SiO2) nanospheres decorated with platinum (Pt) nanoparticles were coupled to detect antibodies by covalent linkage, and the captured antibodies were conjugated with magnetic beads via streptavidin-biotin interaction, simultaneously. When the AFP was loaded, the Pt-catalyzed hydrogen peroxide (H2O2) decomposition reaction was triggered to induce a significant increase in the reflectance signal of the Ag/PDMS bilayer gas pressure sensor (BGPS) due to a "wrinkled–specular" transition of the Ag film's surface. Under optimal conditions, the pressure-based biosensor exhibited a broad linear detection range from 0.05 to 132 ng mL−1 with a limit of detection (LOD) of 0.016 ng mL−1 for AFP, which satisfies the requirements for the clinical detection of AFP. Besides, the high specificity and detection accuracy of our Ag/PDMS BGPS also proved its feasibility for practical diagnosis. [ABSTRACT FROM AUTHOR]

Quantitative analyses of potential radionuclide contaminants in solid wastes (e.g. calcium fluoride sludge) generated by the nuclear industry are essential for clearance or reutilization of these wastes. In order to measure trace uranium isotopes in calcium fluoride sludge, a total sample dissolution method was developed utilizing lithium metaborate fusion and anion exchange chromatography combined with a triple quadrupole ICP-MS/MS instrument. The method was validated using calcium fluoride sludge spiked with known amounts of uranium isotopes. All measured results were in good agreement with the expected values, demonstrating the feasibility of the method for the determination of trace uranium isotopes. The minimum detectable activities of 234U, 235U and 238U were determined to be 0.15 mBq (0.65 pg), 0.67 μBq (8.38 pg) and 0.014 mBq (1.13 ng), respectively. A key finding was that the sensitivity of uranium (750 Mcps ppm−1) with He at a flow rate of 8.5 mL min−1 was 5 times that achieved by ICP-MS/MS without the collision gas. The investigation of the mechanism of He collision would provide a novel and optimal method to simultaneously improve the sensitivity and suppress interference for the analysis of ultra-low level heavy radionuclides (e.g., uranium, plutonium, and americium) combined with reaction gasses (e.g., CO2, O2, and NH3). [ABSTRACT FROM AUTHOR]