Ludmila Otilia Cinteza

Quantum dots in biomedical applications: advances and challenges

In the past two decades, nanotechnology has made great progress in generating novel materials with superior properties. Quantum dots (QDs) are an example of such materials. With unique optical properties, they have proven to be useful in a wide range of applications in life sciences, especially as a better alternative to overcome the shortcomings of conventional fluorophores. Current progress in the synthesis of biocompatible QDs allows for the possibility of producing a large variety of semiconductor nanocrystals in terms of size, surface functionality, bioconjugation, and targeting facilities. Strategies to enhance the water-dispersibility and biocompatibility of these nanoparticles have been developed, involving various encapsulation techniques and surface functionalization. The major obstacle in the clinical use of QDs remains their toxicity, and the systematic investigation on harmful effects of QDs both to humans and to the environment has become critical. Many examples of the experimental use of QDs prove their far-reaching potential for the study of intracellular processes at the molecular level, high resolution cellular imaging, and in vivo observation of cell trafficking. Biosensing methods based on QD bioconjugates proved to be successful in rapid detection of pathogens, and significant improvements are expected in early cancer diagnostic, non-conventional therapy of cancer and neurodegenerative diseases.

Advanced functionalization of organoclay nanoparticles by silylation and their polystyrene nanocomposites obtained by miniemulsion polymerization

Four types of alkoxysilanes with different organosilyl groups were used for the silylation of a commercial alkylammonium-modified montmorillonite (Cloisite 30B). TGA, XPS, DLS, FTIR, XRD, and contact angle measurements were performed for the characterization of the silylated clays. Furthermore, the behavior of these advanced hydrophobic clays in the miniemulsion polymerization process of styrene and the characterization of nanocomposites materials were followed. The hydrophobic nature is a combined result of the length of the organic chain and of the amount of silane groups grafted onto clay edges, reflected also in the final properties of the nanocomposite latexes.

Silicon‐based quantum dots induce inflammation in human lung cells and disrupt extracellular matrix homeostasis

Quantum dots (QDs) are nanocrystalline semiconductor materials that have been tested for biological applications such as cancer therapy, cellular imaging and drug delivery, despite the serious lack of information of their effects on mammalian cells. The present study aimed to evaluate the potential of Si/SiO2 QDs to induce an inflammatory response in MRC‐5 human lung fibroblasts. Cells were exposed to different concentrations of Si/SiO2 QDs (25–200 μg·mL−1) for 24, 48, 72 and 96 h. The results obtained showed that uptake of QDs was dependent on biocorona formation and the stability of nanoparticles in various biological media (minimum essential medium without or with 10% fetal bovine serum). The cell membrane damage indicated by the increase in lactate dehydrogenase release after exposure to QDs was dose‐ and time‐dependent. The level of lysosomes increased proportionally with the concentration of QDs, whereas an accumulation of autophagosomes was also observed. Cellular morphology was affected, as shown by the disruption of actin filaments. The enhanced release of nitric oxide and the increase in interleukin‐6 and interleukin‐8 protein expression suggested that nanoparticles triggered an inflammatory response in MRC‐5 cells. QDs decreased the protein expression and enzymatic activity of matrix metalloproteinase (MMP)‐2 and MMP‐9 and also MMP‐1 caseinase activity, whereas the protein levels of MMP‐1 and tissue inhibitor of metalloproteinase‐1 increased. The present study reveals for the first time that silicon‐based QDs are able to generate inflammation in lung cells and cause an imbalance in extracellular matrix turnover through a differential regulation of MMPs and tissue inhibitor of metalloproteinase‐1 protein expression.

Polymer-clay nanocomposites obtained by solution polymerization of vinyl benzyl triammonium chloride in the presence of advanced functionalized clay

AbstractPolymer-clay nanocomposites were synthesized by solution polymerization method using advanced functionalized clay and vinyl benzyl trimethyl ammonium chloride as monomer. First stage consisted in the silylation of a commercial organo-modified clay-Cl 20A using alkoxysilanes with different chain lengths. In the second step, the synthesis and characterization of polymer-nanocomposites were followed. To evaluate the clay functionalization process as well as the final polymer-clay products, thermogravimetric, X-ray diffraction, dynamic light scattering, Fourier transform infrared spectroscopy and three test liquid contact angles analyses were used. The loss of ammonium ions from commercial clay, the grafting degree, the lengths and the nature of alkyl chain influence the dispersion of the advanced modified clay into the polymer solution and, furthermore, the properties of the final polymer-clay nanocomposite film. Graphical AbstractPolymer-clay nanocomposites were obtained by solution polymerization using advanced functionalized clay and a water soluble monomer. The loss of ammonium ions, the grafting degree, the lengths and the nature of alkyl chain influenced the dispersion of the modified clay into the polymer solution and the properties of the final hybrid film.

Facile Preparation of Impurity Doped CdS Nanoparticles in New Polymeric Templates

Cadmium sulfide nanocrystals (quantum dots) have been prepared using polymer solution as template. The new polymer is a vinyl acetate- maleic anhydride (VAcMA) copolymer obtained by using an original procedure developed in our laboratory. The influence of composition and concentration of the polymer on the size and the optical properties of the semiconductor nanoparticles has been studied. The influence of the reaction parameter was also investigated in order to obtain a versatile procedure to prepare nanocrystals with tunable optical properties. The reaction in polymeric matrix could lead to the formation of wide range of particle size (3–8 nm). In addition to modify the emission properties by controlling the particle size, CdS nanocrystals were doped with Zn, Cu and Mn ions. Both blue and red shifts of the maximum emission wavelength were recorded. QD-polymer composites obtained from CdS nanoparticles prepared in VAcMA matrix have been investigated by UV-VIS, fluorescence and IR spectroscopy, TEM and DLS. The photophysical properties of the semiconductor nanoparticles obtained in polymer matrix was compared for different QD-polymer composites, according to the obtaining procedure.

Dynamic analysis of the interactions between Si/SiO 2 quantum dots and biomolecules for improving applications based on nano-bio interfaces

Due to their outstanding properties, quantum dots (QDs) received a growing interest in the biomedical field, but it is of major importance to investigate and to understand their interaction with the biomolecules. We examined the stability of silicon QDs and the time evolution of QDs – protein corona formation in various biological media (bovine serum albumin, cell culture medium without or supplemented with 10% fetal bovine serum-FBS). Changes in the secondary structure of BSA were also investigated over time. Hydrodynamic size and zeta potential measurements showed an evolution in time indicating the nanoparticle-protein interaction. The protein corona formation was also dependent on time, albumin adsorption reaching the peak level after 1 hour. The silicon QDs adsorbed an important amount of FBS proteins from the first 5 minutes of incubation that was maintained for the next 8 hours, and diminished afterwards. Under protein-free conditions the QDs induced cell membrane damage in a time-dependent manner, however the presence of serum proteins attenuated their hemolytic activity and maintained the integrity of phosphatidylcholine layer. This study provides useful insights regarding the dynamics of BSA adsorption and interaction of silicon QDs with proteins and lipids, in order to understand the role of QDs biocorona.

Chitosan-Stabilized Ag Nanoparticles with Superior Biocompatibility and Their Synergistic Antibacterial Effect in Mixtures with Essential Oils

Silver nanoparticles (AgNPs) are considered a promising alternative to the use of antibiotics in fighting multidrug-resistant pathogens. However, their use in medical application is hindered by the public concern regarding the toxicity of metallic nanoparticles. In this study, rationally designed AgNP were produced, in order to balance the antibacterial activity and toxicity. A facile, environmentally friendly synthesis was used for the electrochemical fabrication of AgNPs. Chitosan was employed as the capping agent, both for the stabilization and to improve the biocompatibility. Size, morphology, composition, capping layer, and stability of the synthesized nanoparticles were characterized. The in vitro biocompatibility and antimicrobial activities of AgNPs against common Gram-negative and Gram-positive bacteria were evaluated. The results revealed that chitosan-stabilized AgNPs were nontoxic to normal fibroblasts, even at high concentrations, compared to bare nanoparticles, while significant antibacterial activity was recorded. The silver colloidal dispersion was further mixed with essential oils (EO) to increase the biological activity. Synergistic effects at some AgNP–EO ratios were observed, as demonstrated by the fractionary inhibitory concentration values. Our results reveal that the synergistic action of both polymer-stabilized AgNPs and essential oils could provide a significant efficiency against a large variety of microorganisms, with minimal side effects.