Aqueous Synthesis of DNA-Functionalized Near-Infrared AgInS₂/ZnS Core/Shell Quantum Dots

Abstract

Biocompatibility, biofunctionality, and chemical stability are essential criteria to be fulfilled by quantum dot (QD) emitters for bio-imaging and -sensing applications. In addition to these criteria, achieving efficient near-infrared (NIR) emission with nontoxic QDs remains very challenging. In this perspective, we developed water-soluble NIR-emitting AgInS 2 /ZnS core/shell (AIS/ ZnS) QDs functionalized with DNA. The newly established aqueous route relying on a two-step hot-injection synthesis led to highly luminescent chalcopyrite-type AIS/ZnS core/shell QDs with an unprecedented photoluminescence quantum yield (PLQY) of 55% at 700 nm and a long photoluminescence (PL) decay time of 900 ns. Fast and slow hot injection of the precursors were compared for the AIS core QD synthesis, yielding a completely different behavior in terms of size, size distribution, stoichiometry, and crystal structure. The PL peak positions of both types of core QDs were 710 (fast) and 760 nm (slow injection) with PLQYs of 36 and 8%, respectively. The slow and successive incorporation of the Zn and S precursors during the subsequent shell growth step on the stronger emitting cores promoted the formation of a three-monolayer thick ZnS shell, evidenced by the increase of the average QD size from 3.0 to 4.8 nm. Bioconjugation of the AIS/ZnS QDs with hexylthiol-modified DNA was achieved during the ZnS shell growth, resulting in a grafting level of 5−6 DNA single strands per QD. The successful chemical conjugation of DNA was attested by UV−vis spectroscopy and agarose gel electrophoresis. Importantly, surface plasmon resonance imaging experiments using complementary DNA strands further corroborated the successful coupling and the stability of the AIS/ZnS-DNA QD conjugates as well as the preservation of the biological activity of the anchored DNA. The strong NIR emission and biocompatibility of these AIS/ ZnS-DNA QDs provide a high potential for their use in biomedical applications.

High-sensitivity fluorescence detection for lung cancer CYFRA21-1 DNA based on accumulative hybridization of quantum dots

“…A representative synthesis method of AgInS 2 QDs with an Ag/In ratio of 1/4 was employed. 36 In a three-neck flask, 8 mL of GSH (0.1 M) and 70 mg of ammonium citrate dibasic were added, and the pH of the solution was adjusted to 6.5 by adding a 5 M NH 4 OH aqueous solution. The formation of a precipitate occurred after the introduction of 0.5 mL of InCl 3 (1 M).…”

“…The next step was the cladding of AgInS 2 with the ZnS shell. 36 Two precursor solutions (A and B) were first prepared: solution A contained 7 mL of Zn(CH 3 COO) 2 Á2H 2 O (0.1 M), 7 mL of the stabilizing ligand GSH (0.1 M) and 2 mL of H 2 O, and solution B consisted of 700 mL of Na 2 S (1 M) and 15.3 mL of H 2 O. The nuclear solution was incubated at 96 1C constantly in a nitrogen atmosphere, and solutions A and B were simultaneously injected into the thermal solution via a syringe pump with a constant flow rate of 0.15 mL min À1 .…”

Ternary Quantum Dots in Chemical Analysis. Synthesis and Detection Mechanisms

“…In addition, QDs have been functionalized for biomedical applications. AgInS 2 was functionalized with sgc8c aptamer to sense tumor cells [ 87 ], methotrexate for drug delivery [ 88 ], and DNA for potential biomedical applications [ 89 ]. Therefore, the functionalization of these novel nanoparticles is an opportunity area with several applications.…”

Aptamer-Conjugated Quantum Dot Optical Biosensors: Strategies and Applications

“…In addition to the application of QDs as visible-range ECL biosensors, there have been efforts to broaden the application of QD biosensors that are capable of detection in the NIR range. NIR emitters have several advantages including minimal autofluorescence, light absorption, and scattering from the biological environment, which have facilitated the development of NIR QDs [75]. In order to detect biomolecules in the NIR range, an aptamer-based QD biosensor has been incorporated with gold nanorods (AuNRs), which exhibit distinct shape-dependent surface plasmon resonance [48]; Figure 3B.…”

“…[ 98,99] • Use of yeast • ZnS and CdS QD production from M13 bacteriophage [107] One way to reduce their toxicity is to change the surface of QDs. This surface change could be achieved through various fabrication strategies of core-shell conjugates because this can increase the size of the QDs and protect the toxic component from degrading, thereby minimizing the surface defects of these QDs and enhancing their luminescent quantum yield [75].…”