Synthesis and in vivo toxicity assessment of CdSe:ZnS quantum dots functionalized with EDTA-Bis-Cysteamine

Abstract

The design and surface chemistry of core shell quantum dots significantly affect their bio-distribution, kinetics and toxicity. Bis-ligands have been shown to improve the loading capacity and control the steric ligand packing density on the quantum dot surfaces, thus improving the biological properties and controlling the toxicity of the quantum dot nano-conjugates. In this study, we functionalized core shell CdSe:ZnS quantum dots with a homo-dimeric system (EDTA-Bis-Cysteamine) and evaluated their stability in vivo for diagnostic applications. This homo-dimeric N 2 S 2 system wraps the quantum dots and has pendant carboxylate moieties for further conjugation chemistry. The novelty in the system is that it can be loaded with a variety of metal atoms through dative bonds, even when the S atoms are attached to the ZnS shell. This results in the formation of a stable complex on a nano-platform for theranostic applications. The synthesized quantum dot nano-conjugate has been structurally evaluated using various analytical techniques.Spectrophotometric studies show the emission of the nano-conjugate at 530 nm, similar to the core shell. The haematology studies, biochemical assays and histopathology performed on the organs of interest showed no significant damage post injection over a time frame of 15 days. The generation of reactive oxygen species by the cadmium based quantum dot nano-conjugate has been evaluated for the first time in vivo using Ferric Reducing Antioxidant Power assay (FRAP). The pharmacokinetics and bio-distribution of the nano-conjugate has been studied using radiolabelling ( 99m Tc). After conjugation, the blood kinetics show increased availability of the quantum dots in the blood pool and the bio-distribution pattern also shows major changes. However, no significant toxic effects were observed during the time scale considered. This study highlights a facile route for designing small homo-dimeric ligand functionalized quantum dots nano-conjugates with favourable biological properties, enhancing their potential to be used as multi-modal imaging/theranostic agents.

Multifunctional Magneto-Fluorescent Nanocarriers for Dual Mode Imaging and Targeted Drug Delivery

“…The in vitro serum stability of MFSCNPs and MFSCNPs-FA-CHI-5FU nanocarriers was determined in serum samples by following the standard protocol . For serum stability experiments, 100 mL of 99m Tc labeled nanocarriers were incubated in 900 μL of the serum (in duplicate) at 37 °C.…”

“…The in vitro serum stability of MFSCNPs and MFSCNPs-FA-CHI-5FU nanocarriers was determined in serum samples by following the standard protocol. 28 For serum stability experiments, 100 mL of 99m Tc labeled nanocarriers were incubated in 900 μL of the serum (in duplicate) at 37 °C. Then samples were analyzed to check for any dissociation by instant thin layer chromatography (ITLC) using silica gel strips in developing solvent (0.9% NaCl aqueous saline solution).…”

“…An aqueous solution of MFSCNPs and MFSCNPs-FA-CHI-5FU nanocarriers (9.78 nM) was added in stannous chloride solution in a shielded vial by following the reported work. 28 The solution pH was adjusted to 6.5−7.0 with NaHCO 3 (0.5 M) and filtered through a 0.22 μm filter into a sterile vial. Freshly eluted 99m TcO 4 − (93.7 MBq) was added in this solution and incubated for 30 min at RT for optimum labeling yield.…”

“…To perform biodistribution studies, the Balb/ C mice were administered with 100 μCi of 99m Tc labeled nanocarriers through the tail intravenously as described in previous reported work. 28 At subsequent time intervals of post injection (1, 2, 4, and 24 h), animals (n = 3) were euthanized and by cardiac puncture, the blood was collected into preweighed tubes. Further, mice were dissected and various organs (heart, lungs, liver, spleen, kidneys, stomach, intestine, muscle) were eradicated and weighed.…”

Enhanced in vivo tumour imaging by EDTA-bis-GNGR functionalized core shell CdSe:ZnS quantum dot: synergistic effect of active passive targeting

“…16 Here we have synthesised a linear tetrapeptide GNGR (Gly-Asn-Gly-Asp) and conjugated it to a homodimeric N 2 S 2 ligand which is an EDTA-bis-cysteamine. In one of our earlier study 30 we have shown that this bis ligand very effectively controls the in vivo toxicity caused due to the leaching out of the Cd 2+ ions by providing a chelating effect. In this study we have tried to evaluate that if a specic targeting moiety is attached to this ligand then will there be an in vivo synergistic effect of active passive targeting or will only one of the mechanism predominate.…”