Hydrophilic, Bright CuInS₂ Quantum Dots as Cd-Free Fluorescent Labels in Quantitative Immunoassay

Abstract

We report on the synthesis of core-shell CuInS2/ZnS quantum dots (QDs) in organic solution, their encapsulation with a PEG-containing amphiphilic polymer, and the application of the resulting water-soluble QDs as fluorescent label in quantitative immunoassay. By optimizing the methods for core synthesis and shell growth, CuInS2/ZnS QDs were obtained with a quantum yield of 50% on average after hydrophilization. After conjugation with an aflatoxin B1-protein derivative, the obtained QDs were used as fluorescent labels in microplate immunoassay for the quantitative determination of the mycotoxin aflatoxin B1. QDs-based immunoassay showed higher sensitivity compared to enzyme-based immunoassay.

Highly sensitive and accurate detection of C-reactive protein by CdSe/ZnS quantum dot-based fluorescence-linked immunosorbent assay

“…Currently, enzymes as labels have been widely used in commercially quantitative immunoassays [1, 2], especially enzyme-linked immunosorbent assay (ELISA) [3, 4] is frequently used in in vitro diagnosis because of its high sensitivity and specificity [5, 6]. The signal collection in ELISA are based on a change in optical transmittance by a time-dependent enzymatic reaction, but enzymes are usually vulnerable to external conditions and very susceptible to matrix constituent [7].…”

Structural and optical characterization of CuInS2 quantum dots synthesized by microwave-assisted continuous flow methods

“…CIS has the advantage of being a ternary material which allows further tuning of optical properties by changing the ratio of Cu and In in the lattice (De Trizio et al 2012;Nam et al 2011;Speranskaya et al 2014;Uehara et al 2008). For example, Cu poor CIS QDs have been shown to have increased PL quantum yield (PLQY) which was blue shifted compared to stoichiometric CIS (Nam et al 2011;Uehara et al 2008;Zhong et al 2012).…”

“…A good quality ZnS shell can be grown on the exposed CIS surfaces due to the small lattice mismatch between the two materials. ZnS shells have been shown to increase PLQY by passivating surface trap states on a range of QD systems including CdSe, CdZnSe, and CIS (Dabbousi et al 1997;Fitzmorris et al 2013;Li et al 2011;Park and Kim 2011;Speranskaya et al 2014).…”

Bioconjugation of quantum dots: Review & impact on future application

“…QDs, in particular, have emerged as one of the most promising labels for immunoassay detection because of their photostability and size tunable photoluminescence. They can be used to develop enzyme linked-immunosorbent assays (ELISAs) [4], lateral flow immunoassays (LFIAs) [99], Western blots [59] or in FRET studies [47,100], to name but a few. For biosensing, the greatest potential of QD-conjugates lies in multiplexing [51,99].…”

“…Nowadays I-III-VI 2 semiconductor QDs (e.g. CuInS 2 ) are considered as one of the main alternatives of Cd-based QDs [4]. Due to QDs small size, the electrons are confined in a limited space, and when the radii of the semiconductor nanocrystal is smaller or equal than the excitation Bohr radius, there is quantization of the energy levels.…”