Viktor Chikan

A/C magnetic hyperthermia of melanoma mediated by iron(0)/iron oxide core/shell magnetic nanoparticles: a mouse study

BackgroundThere is renewed interest in magnetic hyperthermia as a treatment modality for cancer, especially when it is combined with other more traditional therapeutic approaches, such as the co-delivery of anticancer drugs or photodynamic therapy.MethodsThe influence of bimagnetic nanoparticles (MNPs) combined with short external alternating magnetic field (AMF) exposure on the growth of subcutaneous mouse melanomas (B16-F10) was evaluated. Bimagnetic Fe/Fe3O4 core/shell nanoparticles were designed for cancer targeting after intratumoral or intravenous administration. Their inorganic center was protected against rapid biocorrosion by organic dopamine-oligoethylene glycol ligands. TCPP (4-tetracarboxyphenyl porphyrin) units were attached to the dopamine-oligoethylene glycol ligands.ResultsThe magnetic hyperthermia results obtained after intratumoral injection indicated that micromolar concentrations of iron given within the modified core-shell Fe/Fe3O4 nanoparticles caused a significant anti-tumor effect on murine B16-F10 melanoma with three short 10-minute AMF exposures. We also observed a decrease in tumor size after intravenous administration of the MNPs followed by three consecutive days of AMF exposure 24 hrs after the MNPs injection.ConclusionsThese results indicate that intratumoral administration of surface modified MNPs can attenuate mouse melanoma after AMF exposure. Moreover, we have found that after intravenous administration of micromolar concentrations, these MNPs are capable of causing an anti-tumor effect in a mouse melanoma model after only a short AMF exposure time. This is a clear improvement to state of the art.

Cell-delivered magnetic nanoparticles caused hyperthermia-mediated increased survival in a murine pancreatic cancer model

Using magnetic nanoparticles to absorb alternating magnetic field energy as a method of generating localized hyperthermia has been shown to be a potential cancer treatment. This report demonstrates a system that uses tumor homing cells to actively carry iron/iron oxide nanoparticles into tumor tissue for alternating magnetic field treatment. Paramagnetic iron/ iron oxide nanoparticles were synthesized and loaded into RAW264.7 cells (mouse monocyte/ macrophage-like cells), which have been shown to be tumor homing cells. A murine model of disseminated peritoneal pancreatic cancer was then generated by intraperitoneal injection of Pan02 cells. After tumor development, monocyte/macrophage-like cells loaded with iron/ iron oxide nanoparticles were injected intraperitoneally and allowed to migrate into the tumor. Three days after injection, mice were exposed to an alternating magnetic field for 20 minutes to cause the cell-delivered nanoparticles to generate heat. This treatment regimen was repeated three times. A survival study demonstrated that this system can significantly increase survival in a murine pancreatic cancer model, with an average post-tumor insertion life expectancy increase of 31%. This system has the potential to become a useful method for specifically and actively delivering nanoparticles for local hyperthermia treatment of cancer.

Attenuation of Mouse Melanoma by A/C Magnetic Field after Delivery of Bi-Magnetic Nanoparticles by Neural Progenitor Cells

Localized magnetic hyperthermia as a treatment modality for cancer has generated renewed interest, particularly if it can be targeted to the tumor site. We examined whether tumor-tropic neural progenitor cells (NPCs) could be utilized as cell delivery vehicles for achieving preferential accumulation of core/shell iron/iron oxide magnetic nanoparticles (MNPs) within a mouse model of melanoma. We developed aminosiloxane-porphyrin functionalized MNPs, evaluated cell viability and loading efficiency, and transplanted neural progenitor cells loaded with this cargo into mice with melanoma. NPCs were efficiently loaded with core/shell Fe/Fe(3)O(4) MNPs with minimal cytotoxicity; the MNPs accumulated as aggregates in the cytosol. The NPCs loaded with MNPs could travel to subcutaneous melanomas, and after A/C (alternating current) magnetic field (AMF) exposure, the targeted delivery of MNPs by the cells resulted in a measurable regression of the tumors. The tumor attenuation was significant (p < 0.05) a short time (24 h) after the last of three AMF exposures.

Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse

While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 107 has been obtained simitaneously with a dynamic response time of around 10 ms for both light on and off. We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices.

MspA Porin−Gold Nanoparticle Assemblies: Enhanced Binding through a Controlled Cysteine Mutation

In this study, the interactions of two gold nanoparticles of different sizes (average diameters of 3.7 +/- 2.6 and 17 +/- 3 nm) with octameric mycobacterial porin A from Mycobacterium smegmatis (MspA) and a mutant of MspA featuring a cysteine mutation in position 126 (Q126C) are investigated. From the observation of enhanced photoluminescence quenching, it is inferred that the presence of eight cysteines in the MspA Q126C mutant significantly enhances the binding of selected small gold nanoparticles within the inner pore of MspA. The large gold nanoparticle/porin complex shows photoluminescence enhancement, which is expected since the larger nanoparticles cannot dock within the homopore of MspA due to size exclusion. In addition to the fluorescence experiments, observation of energy transfer from the small gold nanoparticles to the MspA shows the close proximity of the small gold nanoparticles with the porin. Interestingly, the energy transfer of the large nanoparticle/MspA complex is completely missing. From high-performance liquid chromatography data, the estimated binding constants for small Au@MspA, large Au@MspA, small Au@MspAcys, and large Au@MspAcys are 1.3 x 10 (9), 2.22 x 10 (10), > 10 (12) (irreversible), and 1.7 x 10 (10), respectively.

Synthesis of Hafnium Oxide-Gold Core–Shell Nanoparticles

Developing cheap composite nanoparticle systems that combines a high dielectric constant with good conductivity is important for the future of the electronic industry. In this study, two different sizes, 7.3 ± 2.2 and 5.6 ± 1.9 nm, of HfO(2)@Au core-shell nanoparticles are prepared by using a high-temperature reduction method. The core-shell nanoparticles are characterized by powder X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), and UV-visible absorption spectroscopy. HfO(2) exhibits no absorption in the visible region, but the HfO(2)@Au core-shell nanoparticles show a plasmon absorption band at 555 nm that is 25 nm red-shifted as compared to pure gold nanoparticles. According to transmission electron microscopy and energy dispersive X-ray analysis, the HfO(2) particles are coated with approximately three atomic layers of gold.

Relaxation dynamics in photoexcited GaSe nanoparticles

The photophysics and relaxation dynamics of GaSe nanoparticles have been studied in room temperature solutions, using static and time-resolved emission spectroscopy. Following 400 nm excitation, these particles exhibit a static emission maximum at 480 nm. This emission is polarized and the anisotropy is largest on the blue edge of the emission spectrum. Both the total (unpolarized) emission kinetics and the emission anisotropy kinetics are obtained. Static emission spectra along with wavelength-dependent kinetic results permit the reconstruction of time-dependent spectra. The kinetic results reported here show an 80 ps decay component in the total emission, but not in the anisotropy decay kinetics. There is an ∼270 cm−1 shift in the emission maximum during this decay. This transient is assigned to direct to indirect band edge relaxation. This is followed by a 400 ps decay in both the total emission and the anisotropy kinetics. A very small shift (∼170 cm−1) in the emission maximum occurs during this decay...

Hexagonal magnetite nanoprisms: preparation, characterization and cellular uptake

The capacity of iron oxide nanocrystals to heat tissue when subjected to an alternating magnetic field (AMF hyperthermia) is shape-selective. Although iron oxide nanostructures with numerous shapes have been synthesized to date, hexagonal Fe3O4 prisms of low toxicity remained elusive. Here, we report the use of a dual ligand system permitting feasible reaction conditions to synthesize nearly perfect hexagonal Fe3O4 nanoplatelet structures, with edge length of 45 ± 5 nm and thickness of 5 to 6 nm. Their Specific Absorption Rate (SAR) is >750 W g(Fe)-1. The Fe3O4 hexagons were coated with a dopamine-based ligand to increase dispersibility in aqueous buffers. The Fe3O4 hexagons were only minimally toxic to RAW264.7 cells, which can be utilized in cell-based cancer targeting approaches.

Effect of Cd/Te ratio on the formation of CdTe magic-sized quantum dots during aggregation.

In this study, the aggregation dynamics of magic-sized CdTe quantum dots is investigated. The experiments show that the growth kinetics of the quantum dots is very sensitive to the Cd/Te ratio. The crossover from tellurium-rich to cadmium-rich conditions produces a very different aggregation pattern, which can be explained by the lack of formation of magic-sized nanoparticles during the reaction conditions. A simple simulation that includes both monomer-induced growth and aggregation growth is presented to reproduce the experimentally observed aggregation patterns. The simulation results strongly suggest that the experimental aggregation pattern can be reproduced if initially a double magic-sized distribution is assumed. The numerical data clearly show that the aggregation is enhanced by the dipole-dipole interaction. Simulations also suggest that the neck formation of the CdTe quantum dot aggregates is unlikely under the experimental conditions. The absence of neck formation is in agreement with the expectations during high-temperature synthesis.

Relaxation and electron transfer dynamics in bare and DTDCI sensitized MoS2 nanoclusters

The trapping dynamics of photogenerated electrons and holes in MoS2 nanoclusters has been studied using time resolved emission polarization and absorption spectroscopies. These results are compared to absorption kinetics obtained on MoS2 nanoclusters with adsorbed DTDCI (DTDCI≡diethylthiodicarbocyanine iodide) dye. The results indicate that emission from the MoS2 band edge state is polarized, while emission from trapped electrons and holes is unpolarized. This polarization difference is used to obtain the electron and hole trapping times and values of 275 ps and 42 ps, respectively, are obtained. Decays having the same time constants are observed in the transient absorption results. The results obtained on the MoS2/DTDCI system show that electron injection occurs with a time constant of 12 ps. These kinetics also show a 225 ps decay component which is assigned to electron trapping and reverse electron transfer. The 225 ps decay time along with the 275 ps trapping time indicates that reverse electron trans...