Synthesis, characterization and cytotoxicity of polyethylene glycol-encapsulated CdTe quantum dots

Application of CdTe/ZnS Core/Shell Quantum Dots as on Fluorescence Sensor for Detection of Gamma Rays

Gamma rays are a type of ionizing radiation that are extremely hazardous and dangerous for humans and the environment. The fluorescence method is a simple, useful, and fast method for the detection of gamma rays. In this research, CdTe/ZnS core/shell quantum dots were used as on fluorescence sensor for the detection of gamma rays. CdTe/ZnS core/shell QDs were prepared via a simple and rapid photochemical method. The shell thickness and concentration of CdTe/ZnS core/shell quantum dots were studied as two important factors in the optical behavior of CdTe/ZnS quantum dots. The obtained results showed that the PL intensity of CdTe/ZnS QDs after gamma irradiation was increased and also a slight redshift in the PL spectrum was observed. X-ray diffractions (XRD) and Raman analyses were used to study the effect of gamma irradiation on the structural properties of CdTe/ZnS QDs. The obtained results showed that gamma irradiation couldn't damage the crystalline structure of CdTe/ZnS core/shell QDs.

The role of acoustofluidics and microbubble dynamics for therapeutic applications and drug delivery

Targeted drug delivery is proposed to reduce the toxic effects of conventional therapeutic methods. For that purpose, nanoparticles are loaded with drugs called nanocarriers and directed toward a specific site. However, biological barriers challenge the nanocarriers to convey the drug to the target site effectively. Different targeting strategies and nanoparticle designs are used to overcome these barriers. Ultrasound is a new, safe, and non-invasive drug targeting method, especially when combined with microbubbles. Microbubbles oscillate under the effect of the ultrasound, which increases the permeability of endothelium, hence, the drug uptake to the target site. Consequently, this new technique reduces the dose of the drug and avoids its side effects. This review aims to describe the biological barriers and the targeting types with the critical features of acoustically driven microbubbles focusing on biomedical applications. The theoretical part covers the historical developments in microbubble models for different conditions: microbubbles in an incompressible and compressible medium and bubbles encapsulated by a shell. The current state and the possible future directions are discussed.

Controlled delivery of quantum dots using microelectrophoresis technique: Intracellular behavior and preservation of cell viability

The use of synthetic nanomaterials as contrast agents, sensors, and drug delivery vehicles in biological research primarily requires effective approaches for intracellular delivery. Recently, the well-accepted microelectrophoresis technique has been reported to exhibit the ability to deliver nanomaterials, quantum dots (QDs) as an example, into live cells, but information about cell viability and intracellular fate of delivered nanomaterials is yet to be provided. Here we show that cell viability following microelectrophoresis of QDs is strongly correlated with the amount of delivered QDs, which can be finely controlled by tuning the ejection duration to maintain long-term cell survival. We reveal that microelectrophoretic delivered QDs distribute homogeneously and present pure Brownian diffusion inside the cytoplasm without endosomal entrapment, having great potential for the study of dynamic intracellular events. We validate that microelectrophoresis is a powerful technique for the effective intracellular delivery of QDs and potentially various functional nanomaterials in biological research.

Biocompatible and fluorescent water based NIR emitting CdTe quantum dot probes for biomedical applications

Proficient fluorescent-characteristics, cytotoxicity-behavior and antimicrobial-activity of near-infrared-emitting (NIR) CdTe quantum dots (QDs) were studied sumptuously as these QDs are having an excellence in deep-tissue dissemination of light. These, NIR-emitting QDs were synthesized using aqueous method, utilizing 3-mercaptopropionic-acid (3-MPA) as a stabilizer; it controls leakage of Cd and Te ions from CdTe QDs. However, encapsulation by polymers also prevents the same by seizing toxic consequence of prepared QDs which was confirmed from cytotoxicity studies. Therefore, easy modification according to biological environment of these encapsulated CdTe QDs can serve in bio imaging and distribution. Antimicrobial study investigated the toxic effects of QDs against bacterial strains and support cytotoxicity studies and showing maximum 26 mm zone of inhibition against bacterial strain. These, NIR fluorescent QDs possess many attractive optical properties over the standard fluorescent probes (organic dyes) and can replace these dyes, as there is no specific dye which works in NIR range.

Quantum dots as targeted doxorubicin drug delivery nanosystems in human lung cancer cells

Background

Lung cancer is one of the most frequently diagnosed cancers all over the world and is also one of the leading causes of cancer-related mortality. The main treatment option for small cell lung cancer, conventional chemotherapy, is characterized by a lack of specificity, resulting in severe adverse effects. Therefore, this study aimed at developing a new targeted drug delivery (TDD) system based on Ag–In–Zn–S quantum dots (QDs). For this purpose, the QD nanocrystals were modified with 11-mercaptoundecanoic acid (MUA), L-cysteine, and lipoic acid decorated with folic acid (FA) and used as a novel TDD system for targeting doxorubicin (DOX) to folate receptors (FARs) on adenocarcinomic human alveolar basal epithelial cells (A549). NIH/3T3 cells were used as FAR-negative controls. Comprehensive physicochemical, cytotoxicity, and genotoxicity studies were performed to characterize the developed novel TDDs.

Results

Fourier transformation infrared spectroscopy, dynamic light scattering, and fluorescence quenching confirmed the successful attachment of FA to the QD nanocrystals and of DOX to the QD–FA nanocarriers. UV–Vis analysis helped in determining the amount of FA and DOX covalently anchored to the surface of the QD nanocrystals. Biological screening revealed that the QD–FA–DOX nanoconjugates had higher cytotoxicity in comparison to the other forms of synthesized QD samples, suggesting the cytotoxic effect of DOX liberated from the QD constructs. Contrary to the QD–MUA–FA–DOX nanoconjugates which occurred to be the most cytotoxic against A549 cells among others, no such effect was observed for NIH/3T3 cells, confirming FARs as molecular targets. In vitro scratch assay also revealed significant inhibition of A549 cell migration after treatment with QD–MUA–FA–DOX. The performed studies evidenced that at IC50 all the nanoconjugates induced significantly more DNA breaks than that observed in nontreated cells. Overall, the QD–MUA–FA–DOX nanoconjugates showed the greatest cytotoxicity and genotoxicity, while significantly inhibiting the migratory potential of A549 cells.

Conclusion

QD–MUA–FA–DOX nanoconjugates can thus be considered as a potential drug delivery system for the effective treatment of adenocarcinomic human alveolar basal epithelial cells.

Influence of Surface Ligands on Charge-Carrier Trapping and Relaxation in Water-Soluble CdSe@CdS Nanorods

In this study, the impact of the type of ligand at the surface of colloidal CdSe@CdS dot-in-rod nanostructures on the basic exciton relaxation and charge localization processes is closely examined. These systems have been introduced into the field of artificial photosynthesis as potent photosensitizers in assemblies for light driven hydrogen generation. Following photoinduced exciton generation, electrons can be transferred to catalytic reaction centers while holes localize into the CdSe seed, which can prevent charge recombination and lead to the formation of long-lived charge separation in assemblies containing catalytic reaction centers. These processes are in competition with trapping processes of charges at surface defect sites. The density and type of surface defects strongly depend on the type of ligand used. Here we report on a systematic steady-state and time-resolved spectroscopic investigation of the impact of the type of anchoring group (phosphine oxide, thiols, dithiols, amines) and the bulkiness of the ligand (alkyl chains vs. poly(ethylene glycol) (PEG)) to unravel trapping pathways and localization efficiencies. We show that the introduction of the widely used thiol ligands leads to an increase of hole traps at the surface compared to trioctylphosphine oxide (TOPO) capped rods, which prevent hole localization in the CdSe core. On the other hand, steric restrictions, e.g., in dithiolates or with bulky side chains (PEG), decrease the surface coverage, and increase the density of electron trap states, impacting the recombination dynamics at the ns timescale. The amines in poly(ethylene imine) (PEI) on the other hand can saturate and remove surface traps to a wide extent. Implications for catalysis are discussed.