7 research outputs found
Synthesis of PEGylated Ferrocene Nanoconjugates as the Radiosensitizer of Cancer Cells
Radiation is one of the most widely
used methods for cancer diagnosis
and therapy. Herein, we report a new type of radiation sensitizer
(Fc-PEG) by a facile one-step reaction of conjugating the hydrophilic
PEG chain with hydrophobic ferrocene molecule. The chemical composition
and structure of Fc-PEG have been thoroughly characterized by FT-IR,
NMR, GPC, and MALDI-TOF mass spectrometry. This Fc-PEG conjugate could
self-assemble in aqueous solution into spherical aggregates, and it
was found that the exposure to 4 Gy of X-ray radiation have little
influence on the shape and size of these aggregates. After the chemical
bonding with PEG chains, the uptake level of Fe element could be enhanced
via the formation of aggregates. The live/dead, CCK-8, as well as
apoptosis assays, indicated that the death of cancer cells can be
obviously increased by X-ray radiation after the incubation of these
Fc-based nanoconjugates, which might be served as the radiation sensitizer
toward cancer cells. We suggest that this radiosensitizing effect
comes from the enhancement of reactive oxygen specimen (ROS) level
as denoted by both flow cytometric and fluorescence microscopic analysis.
The enhanced radiation sensitivity of cancer cells is contributed
by the synergic effect of Fe-induced radiation-sensitizing and the
increased uptake of nanoconjugates after polymeric grafting
Light-Enhanced Antibacterial Activity of Graphene Oxide, Mainly via Accelerated Electron Transfer
Before graphene derivatives can be
exploited as next-generation
antimicrobials, we must understand their behavior under environmental
conditions. Here, we demonstrate how exposure to simulated sunlight
significantly enhances the antibacterial activity of graphene oxide
(GO) and reveal the underlying mechanism. Our measurements of reactive
oxygen species (ROS) showed that only singlet oxygen (<sup>1</sup>O<sub>2</sub>) is generated by GO exposed to simulated sunlight,
which contributes only slightly to the oxidation of antioxidant biomolecules.
Unexpectedly, we find the main cause of oxidation is light-induced
electronâhole pairs generated on the surface of GO. These light-induced
electrons promote the reduction of GO, introducing additional carbon-centered
free radicals that may also enhance the antibacterial activities of
GO. We conclude that GO-mediated oxidative stress mainly is ROS-independent;
simulated sunlight accelerates the transfer of electrons from antioxidant
biomolecules to GO, thereby destroying bacterial antioxidant systems
and causing the reduction of GO. Our insights will help support the
development of graphene for antibacterial applications
Reduced Cytotoxicity of Graphene Nanosheets Mediated by Blood-Protein Coating
The advent and pending wide use of nanoscale materials urges a biosafety assessment and safe design of nanomaterials that demonstrate applicability to human medicine. In biological microenvironment, biomolecules will bind onto nanoparticles forming corona and endow nanoparticles new biological identity. Since blood-circulatory system will most likely be the first interaction organ exposed to these nanomaterials, a deep understanding of the basic interaction mechanisms between serum proteins and foreign nanoparticles may help to better clarify the potential risks of nanomaterials and provide guidance on safe design of nanomaterials. In this study, the adsorption of four high-abundance blood proteins onto the carbon-based nanomaterial graphene oxide (GO) and reduced GO (rGO) were investigated <i>via</i> experimental (AFM, florescence spectroscopy, SPR) and simulation-based (molecular dynamics) approaches. Among the proteins in question, we observe competitive binding to the GO surface that features a meĚlange of distinct packing modes. Our MD simulations reveal that the protein adsorption is mainly enthalpically driven through strong ĎâĎ stacking interactions between GO and aromatic protein residues, in addition to hydrophobic interactions. Overall, these results were in line with previous findings related to adsorption of serum proteins onto single-walled carbon nanotubes (SWCNTs), but GO exhibits a dramatic enhancement of adsorption capacity compared to this one-dimensional carbon form. Encouragingly, protein-coated GO resulted in a markedly less cytotoxicity than pristine and protein-coated SWCNTs, suggesting a useful role for this planar nanomaterial in biomedical applications
Facet Energy <i>versus</i> Enzyme-like Activities: The Unexpected Protection of Palladium Nanocrystals against Oxidative Damage
To
develop nanomaterials as artificial enzymes, it is necessary
to better understand how their physicochemical properties affect their
enzyme-like activities. Although prior research has demonstrated that
nanomaterials exhibit tunable enzyme-like activities depending on
their size, structure, and composition, few studies have examined
the effect of surface facets, which determine surface energy or surface
reactivity. Here, we use electron spin-resonance spectroscopy to report
that lower surface energy {111}-faceted Pd octahedrons have greater
intrinsic antioxidant enzyme-like activity than higher surface energy
{100}-faceted Pd nanocubes. Our <i>in vitro</i> experiments
found that those same Pd octahedrons are more effective than Pd nanocubes
at scavenging reactive oxygen species (ROS). Those reductions in ROS
preserve the homogeneity of mitochondrial membrane potential and attenuate
damage to important biomolecules, thereby allowing a substantially
higher number of cells to survive oxidative challenges. Our computations
of molecular mechanisms for the antioxidant activities of {111}- and
{100}-faceted Pd nanocrystals, as well as their activity order, agree
well with experimental observations. These findings can guide the
design of antioxidant-mimicking nanomaterials, which could have therapeutic
or preventative potential against oxidative stress related diseases
Crossover between Anti- and Pro-oxidant Activities of Graphene Quantum Dots in the Absence or Presence of Light
Graphene
quantum dots (GQDs), zero-dimensional carbon materials
displaying excellent luminescence properties, show great promise for
medical applications such as imaging, drug delivery, biosensors, and
novel therapeutics. A deeper understanding of how the properties of
GQDs interact with biological systems is essential for these applications.
Our work demonstrates that GQDs can efficiently scavenge a number
of free radicals and thereby protect cells against oxidative damage.
However, upon exposure to blue light, GQDs exhibit significant phototoxicity
through increasing intracellular reactive oxygen species (ROS) levels
and reducing cell viability, attributable to the generation of free
radicals under light excitation. We confirm that light-induced formation
of ROS originates from the electronâhole pair and, more importantly,
reveal that singlet oxygen is generated by photoexcited GQDs <i>via</i> both energy-transfer and electron-transfer pathways.
Moreover, upon light excitation, GQDs accelerate the oxidation of
non-enzymic anti-oxidants and promote lipid peroxidation, contributing
to the phototoxicity of GQDs. Our results reveal that GQDs can display
both anti- and pro-oxidant activities, depending upon light exposure,
which will be useful in guiding the safe application and development
of potential anticancer/antibacterial applications for GQDs
Tungsten Sulfide Quantum Dots as Multifunctional Nanotheranostics for <i>In Vivo</i> Dual-Modal Image-Guided Photothermal/Radiotherapy Synergistic Therapy
Designing a multifunctional nanomedicine for integration of precise diagnosis and effective treatment of tumors is desirable but remains a great challenge. Here, we report a multifunctional nanomedicine based on WS<sub>2</sub> quantum dots (QDs), which was prepared by a facile and âgreenâ method through physical grinding and ultrasonication. The as-obtained WS<sub>2</sub> QDs with small size (3 nm) possess not only significant X-ray computed tomography (CT)/photoaccoustic (PA) imaging signal enhancement but also remarkable photothermal therapy (PTT)/radiotherapy (RT) synergistic effect for tumor treatment. With CT/PA imaging and the synergistic effect between PTT and RT, the tumor could be accurately positioned and thoroughly eradicated <i>in vivo</i> after intravenous injection of WS<sub>2</sub> QDs. Moreover, hematoxylin and eosin staining, blood hematology, and biochemistry analysis revealed no noticeable toxicity of WS<sub>2</sub> QDs <i>in vitro</i> and <i>in vivo</i>, which confirmed that WS<sub>2</sub> QDs possess good biocompatibility. This multifunctional nanoparticle could play an important role in facilitating simultaneously multimodal imaging and synergistic therapy between PTT and RT to achieve better therapeutic efficacy
Bactericidal Effects of Silver Nanoparticles on Lactobacilli and the Underlying Mechanism
While
the antibacterial properties of silver nanoparticles (AgNPs)
have been demonstrated across a spectrum of bacterial pathogens, the
effects of AgNPs on the beneficial bacteria are less clear. To address
this issue, we compared the antibacterial activity of AgNPs against
two beneficial lactobacilli (<i>Lactobacillus delbrueckii subsp.
bulgaricus</i> and <i>Lactobacillus casei</i>) and
two common opportunistic pathogens (<i>Escherichia coli</i> and <i>Staphylococcus aureus</i>). Our results demonstrate
that those lactobacilli are highly susceptible to AgNPs, while the
opportunistic pathogens are not. Acidic environment caused by the
lactobacilli is associated with the bactericidal effects of AgNPs.
Our mechanistic study suggests that the acidic growth environment
of lactobacilli promotes AgNP dissolution and hydroxyl radical (â˘OH)
overproduction. Furthermore, increases in silver ions (Ag<sup>+</sup>) and â˘OH deplete the glutathione pool inside the cell, which
is associated with the increase in cellular reactive oxygen species
(ROS). High levels of ROS may further induce DNA damage and lead to
cell death. When <i>E. coli</i> and <i>S. aureus</i> are placed in a similar acidic environment, they also become more
susceptible to AgNPs. This study provides a mechanistic description
of a pH-Ag<sup>+</sup>-â˘OH bactericidal pathway and will contribute
to the responsible development of products containing AgNPs