A novel ratiometric fluorescent immunoassay for human α-fetoprotein based on carbon nanodot-doped silica nanoparticles and FITC

Abstract

The application of fluorescent carbon nanodots (C-dots or CD), non-toxic particulate organic labels, to disease biomarker detection is still in its earliest stage of development. In the effort described here, a novel ratiometric immunoassay was developed to target a model protein disease biomarker, alpha-fetoprotein (AFP), using C-dot doped silica nanoparticles (CD-SNPs) and fluorescein isothiocyanate (FITC) as signaling agents. Highly fluorescent C-dots were hydrothermally synthesized from citric acid and ethylene diamine. The C-dots were then encapsulated in silicate shells to yield 45 nm nanoparticles using a novel reverse microemulsion method, enabling convenient handling (centrifugation and washing) and straightforward surface chemistry modification to facilitate development of bioassays. Capture antibody capped CD-SNPs (Ab1-CD-SNPs), together with FITC labeled antibodies (Ab2-FITC) constituted a new ratiometric immunosensor for AFP, in which CD-SNPs functioned as both solid supports for washing and separation and as built-in reference signaling agents to correct for inconsistent environmental effects. A calibration curve was established between the ratiometric signal (the ratio of fluorescence signals of FITC and C-dots, F/C) and AFP concentration in the broad range of 0.317-280 μg/dL, exhibiting a useful linear range (0.317-35 μg/dL, R 2 =0.9977), low detection limit (0.317 μg/dL) and acceptable recovery (105-120%). This assay format can be applied to a wide range of immunoassay targets. Our demonstration of encapsulating low-cost, easily synthesized, highly-fluorescent C-dots into silica nanoparticles for use in immunoassays will be useful in expanding future applications of these carbon nanomaterials to areas such as in-vivo cellular imaging, drug delivery, and in-vitro cell labeling and biomolecule sensing.

Preparation of gold nanoparticle coated NaYF4:Yb,Er,Gd nanoparticles and their application for AFP detection in the red region

“…Table 1 Assay results of AFP in serum samples Table 2 shows the analytical performance of other methods for AFP detection. This new one-step detection method has a low (Limit of Detection) LOD and wide range of detection similar to or better than previously reported ways [36][37][38][39][40][41] . However, the system provides cost-effective testing with a simple measuring process.…”

Functionalisation of Detonation Nanodiamond for Monodispersed, Soluble DNA-Nanodiamond Conjugates Using Mixed Silane Bead-Assisted Sonication Disintegration

“…For A100, APTES functionalisation was confirmed by the characteristic NH 2 bending mode at 1557 cm −1 , corresponding to the APTES functional head group 45 . For T100, THPMP functionalisation was confirmed by identification of two peaks corresponding to head group moieties of THPMP 46 .…”

Reductant‐Free Synthesis of Silver Nanoparticles by Functionalized Hollow Doughnut Mesoporous Silica Nanoparticles for Preparation of Catalytic Nanoreactor

“…After modified with amine functional group, the FT‐IR spectrum of hd‐MSN‐NH 2 exhibited the new peaks at 2940 cm −1 , 2885 cm −1 and 2824 cm −1 corresponding to C−H stretching of methyl group on grafted DAEAPTS . Additionally, the peak at 1578 cm −1 corresponded to symmetric stretching of N−H bond of amine functional group …”