Jian-Cheng Jin

Interactions between carbon nanodots with human serum albumin and γ-globulins: The effects on the transportation function.

Carbon nanodots (C-dots) have attracted great attention as a new class of luminescent nanomaterials due to their superior physical and chemical properties. In order to better understand the basic behavior of C-dots in biological systems, a series of photophysical measurements were applied to study the interactions of C-dots with human serum albumin (HSA) and γ-globulins. The fluorescence of proteins was quenched by the dynamic mechanism rather than the formation of a protein/C-dots complex. The apparent dissociation constants of the C-dots bound to HSA and γ-globulins were of the same order of magnitude. Furthermore, it is proven that C-dots showed little influence on the conformation of HSA and γ-globulins. In addition, Fourier transform infrared and fluorescence spectroscopic studies demonstrated that the interaction between C-dots and two kinds of serum proteins was driven by hydrophobic and van der waals forces. Since the bioavailability of drugs can be modulated by their interactions with proteins, the variations of binding constants of three drugs with HSA and γ-globulins in the presence of different concentrations of C-dots (0-84 μmol L(-1)) have also been analyzed in this work, to reflect the effect of C-dots on the transportation function of HSA and γ-globulins.

Highly Photoluminescent Nitrogen-Doped Carbon Nanodots and Their Protective Effects against Oxidative Stress on Cells

Highly photoluminescent (PL) (quantum yield = 54%) nitrogen doped carbon nanodots (C-dots) have been prepared through one-step carbonizing citric acid and tris(hydroxymethyl)aminomethane and using oleic acid as solvent. The synthesized C-dots are monodisperse with narrow size distribution (average 1.7 nm). The PL properties of C-dots are pH dependent, and hence, using C-dots as sophisticated pH sensor to detect pH values between 7 and 9 can be expected. In addition, the PL intensity of C-dots remains stable under high ionic strength. The C-dots can protect cells from oxidative stress, which shows potential to expand the biological application of C-dots, especially in medical treatment. The protective mechanism is associated with intracellular reactive oxygen species elimination and the intracellular superoxide dismutase production.

Mitochondrial dysfunction induced by different concentrations of gadolinium ion.

Gadolinium-based compounds are the most widely used paramagnetic contrast agents in magnetic resonance imaging on the world. But the tricationic gadolinium ion (Gd(3+)) could induce cell apoptosis probably because of its effects on mitochondria. Until now, the mechanism about how Gd(3+) interacts with mitochondria is not well elucidated. In this work, mitochondrial swelling, collapsed transmembrane potential and decreased membrane fluidity were observed to be important factors for mitochondrial permeability transition pore (mtPTP) opening induced by Gd(3+). The protection effect of CsA (Cyclosporin A) could confirm high concentration of Gd(3+) (500 μM) would trigger mtPTP opening. Moreover, mitochondrial outer membrane breakdown and volume expansion observed clearly by transmission electron microscopy and the release of Cyt c (Cytochrome c) could explain the mtPTP opening from another aspect. In addition, MBM(+) (monobromobimane(+)) and DTT (dithiothreitol) could protect thiol (-SH) groups from oxidation so that the toxicity of Gd(3+) might be resulted from the chelation of -SH of membrane proteins by free Gd(3+). Gd(3+) could inhibit the initiation of mitochondrial membrane lipid peroxidation, so it might interact with anionic lipids too. These findings will highly contribute to the safe applications of Gd-based agents.

Mitochondrial dysfunction induced by ultra-small silver nanoclusters with a distinct toxic mechanism

As noble metal nanoclusters (NCs) are widely employed in nanotechnology, their potential threats to human and environment are relatively less understood. Herein, the biological effects of ultra-small silver NCs coated by bovine serum albumin (BSA) (Ag-BSA NCs) on isolated rat liver mitochondria were investigated by testing mitochondrial swelling, membrane permeability, ROS generation, lipid peroxidation and respiration. It was found that Ag-BSA NCs induced mitochondrial dysfunction via synergistic effects of two different ways: (1) inducing mitochondrial membrane permeability transition (MPT) by interacting with the phospholipid bilayer of the mitochondrial membrane (not with specific MPT pore proteins); (2) damaging mitochondrial respiration by the generation of reactive oxygen species (ROS). As far as we know, this is the first report on the biological effects of ultra-small size nanoparticles (∼2 nm) at the sub-cellular level, which provides significant insights into the potential risks brought by the applications of NCs. It would inspire us to evaluate the potential threats of nanomaterials more comprehensively, even though they showed no obvious toxicity to cells or in vivo animal models. Noteworthy, a distinct toxic mechanism to mitochondria caused by Ag-BSA NCs was proposed and elucidated.

Necrotic cell death induced by the protein-mediated intercellular uptake of CdTe quantum dots.

The toxicity of CdTe QDs with nearly identical maximum emission wavelength but modified with four different ligands (MPA, NAC, GSH and dBSA) to HEK293 and HeLa cells were investigated using flow cytometry, spectroscopic and microscopic methods. The results showed that the cytotoxicity of QDs increased in a dose- and time-dependent manner. No appreciable fraction of cells with sub-G1 DNA content, the loss of membrane integrity, and the swelling of nuclei clearly indicated that CdTe QDs could lead to necrotic cell death in HEK293 cells. JC-1 staining and TEM images confirmed that QDs induced MPT, which resulted in mitochondrial swelling, collapse of the membrane potential. MPT is an important step in QDs-induced necrosis. Moreover, QDs induced MPT through the elevation of ROS. The fluorimetric assay and theoretical analysis demonstrated ROS production has been associated with the internalization of QDs with cells. Due to large surface/volume ratios of QDs, when QDs added in the culture medium, serum proteins in the culture medium will be adsorbed on the surface of QDs. This adsorption of serum protein will change the surface properties and size, and then mediate the cellular uptake of QDs via the clathrin-mediated endocytic pathway. After entering into cells, the translocation of QDs in cells is usually via endosomal or lysosomal vesicles. The rapid degradation of QDs in lysosome and the lysosomal destabilization induce cell necrosis. This study provides a basis for understanding the cytotoxicity mechanism of CdTe QDs, and valuable information for safe use of QDs in the future.

Spectroscopic and Microscopic Studies on the Mechanism of Mitochondrial Toxicity Induced by CdTe QDs Modified with Different Ligands

Quantum dots (QDs) are increasingly applied in sensing, drug delivery, biomedical imaging, electronics industries, etc. Consequently, it is urgently required to examine their potential threat to humans and the environment. In the present work, the toxicity of CdTe QDs with nearly identical maximum emission wavelength but modified with two different ligands (MPA and BSA) to mitochondria was investigated using flow cytometry, spectroscopic, and microscopic methods. The results showed that QDs induced mitochondrial permeability transition (MPT), which resulted in mitochondrial swelling, collapse of the membrane potential, inner membrane permeability to H+ and K+, the increase of membrane fluidity, depression of respiration, alterations of ultrastructure, and the release of cytochrome c. Furthermore, the protective effects of CsA and EDTA confirmed QDs might be able to induce MPT via a Ca2+-dependent domain. However, the difference between the influence of CdTe QDs and that of Cd2+ on mitochondrial membrane fluidity indicated the release of Cd2+ was not the sole reason that QDs induced mitochondrial dysfunction, which might be related to the nanoscale effect of QDs. Compared with MPA-CdTe QDs, BSA-CdTe QDs had a greater effect on the mitochondrial swelling, membrane fluidity, and permeabilization to H+ and K+ by mitochondrial inner membrane, which was caused the fact that BSA was more lipophilic than MPA. This study provides an important basis for understanding the mechanism of the toxicity of CdTe QDs to mitochondria, and valuable information for safe use of QDs in the future.

The interactions between CdSe quantum dots and yeast Saccharomyces cerevisiae: Adhesion of quantum dots to the cell surface and the protection effect of ZnS shell

The interactions between quantum dots (QDs) and biological systems have attracted increasing attention due to concerns on possible toxicity of the nanoscale materials. The biological effects of CdSe QDs and CdSe/ZnS QDs with nearly identical hydrodynamic size on Saccharomyces cerevisiae were investigated via microcalorimetric, spectroscopic and microscopic methods, demonstrating a toxic order CdSe>CdSe/ZnS QDs. CdSe QDs damaged yeast cell wall and reduced the mitochondrial membrane potential. Noteworthy, adhesion of QDs to the yeast cell surface renders this work a good example of interaction site at cell surface, and the epitaxial coating of ZnS could greatly reduce the toxicity of Cd-containing QDs. These results will contribute to the safety evaluation of quantum dots, and provide valuable information for design of nanomaterials.

Microcalorimetric studies of the effect of cerium (Ш) on isolated rice mitochondria fed by pyruvate

Mitochondria were isolated from the hybrid rice Xiangzaoxian 31, then the effects of low and high concentrations of Ce (Ш) on metabolism of mitochondria fed by pyruvate were investigated respectively, by microcalorimetry and oxygen electrode method The thermogenic curve of mitochondria without Ce (Ш) could be divided into three parts: activity recovery phase, stationary phase and decline phase. And the thermokinetic parameters have been calculated through the metabolic thermogenic curves. With addition of different concentrations of Ce (Ш), the results demonstrated that low levels of cerium ion stimulated the metabolic activity of energized mitochondria and the inhibition was discovered with high concentrations of Ce (Ш). At the same time, it is shown that the effect in respiration correspond to the effect on mitochondrial metabolism on addition of different concentrations of Ce (Ш). Moreover, the addition of low and high concentrations of Ce (Ш) had no obvious effect on the total heat output (Q). The concentration-dependent effect of Ce (Ш) on metabolism of mitochondria is similar to plant growth response to rare earth elements (Hormesis effect).

High Concentration of Gadolinium Ion Modifying Isolated Rice Mitochondrial Biogenesis

Mitochondria play an important role in plant growth and development, cooperating with the endoplasmic reticulum and nucleus. Gadolinium, one of the rare earth elements, is an inhibitor of stretch-activated calcium channels located on the endoplasmic reticulum and plasma membrane and has no effect on nuclear calcium variation in plant cells. We analyzed the effects of Gd3+ on mitochondria function by monitoring mitochondrial swelling, changes of membrane fluidity, and transmembrane potential collapse and by observing mitochondrial ultrastructure. We found that high concentration of Gd3+ induces rice mitochondrial dysfunction through mitochondrial permeability transition (MPT). The protection of DTT and EDTA demonstrate that Gd3+ blocks the inner membrane ion channel through thiol chelation.

Ce(III)-Induced Rice Mitochondrial Permeability Transition Investigated by Spectroscopic and Microscopic Studies

Cerium has been widely used as fertilizer and feed additives in agriculture, but it might finally impair human health by food chain accumulation with its dosage increased in environmental and crops samples. To resolve the conflict, we investigated the effects of Ce(III) on isolated rice mitochondrial permeability transition (MPT) by examining mitochondrial swelling, transmembrane potential, membrane fluidity with spectroscopy, and observing the mitochondrial ultrastructure, meanwhile, the interaction site(s) and mechanism between Ce(III) and mitochondria were also studied. The results showed that the low level of Ce(III) had little effect on rice MPT, however, the higher level of Ce(III) could induce rice MPT, and the thiol (−SH) groups of membrane proteins (defined as “S” site) matched by Ce(III)-triggered rice MPT pore opening.