Multicore magnetic nanoparticles (MMNPs) doped with Cs and FITC for the determination of biomarker in serum using ICP-MS.

Multicore magnetic nanoparticles (MMNPs) doped with Cs and FITC (Cs/FITC-doped MMNPs) were synthesized for the extraction and determination of biomarkers using inductively coupled plasma-mass spectrometry (ICP-MS). For demonstration, the MMNPs were used for magnetic separation to extract CA19-9 in serum nonspecifically, and the doped Cs was used as an internal standard for the ratiometric measurement of the tagged particle. This ratiometric method compensated for the particle loss in a magnetic separation and suppressed the signal fluctuation which increased the calibration linearity significantly. The obtained detection limit was 0.02 units/mL of CA19-9, which is more than 300 times lower than that reported by the ICP-MS with element tagging and about 500-fold improved compared to ELISA.

Core-shell silica nanoparticles synthesized for quantitative study of DNA cleavage by laser-induced fluorescence microscopy.

Dye-doped silica nanoparticles (C dots) were synthesized in reverse microemulsions and used to quantitatively examine DNA cleavage in the presence of transition metal ions. The cores were synthesized as fluorescein isothiocyanate (FITC)-doped silica nanoparticles and the shells' surfaces were modified with single-stranded DNA oligomers tagged with Cy5 fluorophores. DNA cleavage induced by heavy metal ions was estimated by comparing the fluorescence of Cy5 before and after reaction with metal ions. For this, a lab-built laser-induced fluorescence microscope equipped with a charge coupled device (CCD) camera, for imaging, and photomultiplier tube, for photon counting, was used. FITC fluorescence from the core was measured as an internal standard to compensate for possible loss of the beads during the treatment. The cleavage of DNA in air in the presence of Pb(2+), Cd(2+), and Hg(2+) at 1 ng/mL was found to be 14%, 6%, and 20%, respectively, and was significantly reduced to below 9% under N(2) gas, indicating that the main cleavage source was oxygen in air. The most significant DNA cleavage was observed with the addition of hydrogen peroxide. This analytical method using dye-doped C dots provided convenient handling and quantification of the estimation of metal-DNA interaction with a detection limit of 34.9 pmol/mL.