Kuantum noktacıklarının hücresel etkileşim ve sitotoksisitelerinin araştırılması

TÜBİTAK SBAG Proje01.05.201

An experimental study on heat transfer performance of iron oxide based ferrofluids

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous

Experimental study on heat transfer performance of iron oxide based ferrofluids to be used as new generation coolants and drug delivery agents

Ferrofluids are colloidal suspensions, in which the solid phase material is composed of magnetic nanoparticles, while the base fluid can potentially be any fluid. The solid particles are held in suspension by weak intermolecular forces and may be made of materials with different magnetic properties. Magnetite is one of the materials used for its natural ferromagnetic properties. Heat transfer performance of ferrofluids should be carefully analyzed and considered for their potential of their use in wide range of applications. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with Lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions varying from 0% to ~5% and average particle diameter of 25 nm, in a hypodermic stainless steel microtube with an inner diameter of 514 Hm, an outer diameter of 819 Hm, and a heated length of 2.5 cm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1ml/s, 0.62ml/s and 0.36 ml/s). A decrease of around 100% in the maximum surface temperature (measured at the exit of the microtube) with the ferrofluid compared to the pure base fluid at significant heat fluxes (>100 W/cm2) was observed. Moreover, the enhancement in heat transfer increased with nanoparticle concentration, and there was no clue for saturation in heat transfer coefficient profiles with increasing volume fraction over the volume fraction range in this study (0%-5%). The promising results obtained from the experiments suggest that the use of ferrofluids for heat transfer, drug delivery, and biological applications can be advantageous and a viable alternative as new generation coolants and futuristic drug carriers

Heat transfer enhancement with iron oxide nanoparticle based ferrofluids

Nanofluids are colloidal compounds, where the solid phase material is composed of nano sized particles, and the liquid phase can potentially be any fluid but aqueous media are common. As a common nanofluid type, ferrofluids are formed by holding solid nanoparticles in suspension by weak intermolecular forces and may be produced from materials with different magnetic properties. Heat transfer performance of ferrofluids is one of the crucial properties among many others that should be analyzed and considered for their wide range of applications. For this purpose, experiments were conducted in order to characterize heat transfer properties of ironoxide based ferrofluids flowing through a microchannel. In this study, convective heat transfer experiments were conducted in order to characterize convective heat transfer enhancements with Lauric acid coated ironoxide (Fe3O4) nanoparticle based ferrofluids, which have volumetric fractions between 0%–∼5% and average particle diameter of 25 nm, in a 2.5 cm long hypodermic stainless steel microtube with an inner diameter of 514 μm and an outer diameter of 819 μm. Heat fluxes up to 184 W/cm2 were applied to the system at three different flow rates (1ml/s, 0.62ml/s and 0.36 ml/s). Promising results were obtained from this study, which are suggesting the use of ferrofluids for heat transfer applications can be advantageous

Development of theranostic PNIPAM/SPION nanoparticles for cancer treatment

Backround/Aim: Stimuli-responsive nanoparticles are being investigated for controlled delivery of toxic drugs to the disease site, especially in cancer. Tumors are known as more acidic and hypertermic in comparison with healthy body parts. Thus, pH and/or temperature-responsive drug delivery vehicles have a tremendous importance in achieving secure delivery and se-cretion of the cargo chemotherapeutic drug only to the tumor site to enhance the efficacy and reduce side effects. Materi-als & Methods: In this study, Poly (N-isopropylacrylamide) (PNIPAM) bound Fe3O4 nanoparticles (SPION-PNIPAM) were synthesized via surface initiated ATRP (atom transfer radical polymerization) and loaded with chemotherapeutic drug Doxo-rubicin (Dox). We performed MTT and Trypan Blue Exclusion Assay to evaluate dose and temperature dependent cell viabili-ty exposed to Dox, nanoparticles and Dox loaded nanoparticles. Confocal analysis was carried out to observe cellular uptake and intracellular trafficking of NPs. Gamma-H2AX phosphor-ylation, p53 and Caspase activation were examined through Immunoblotting to identify the NP and drug dependent DNA damage in vitro. Results: Release studies performed at differ-ent temperatures (25 °C, 37 °C, 42 °C) and pH (7.4, 5.6) re-vealed both pH and temperature dependent release which is minimal at physiological pH and temperature and maximum at low pH-high temperature combination. For the toxicity studies, we have used HeLa cervical cancer cells. Administration of the PNIPAM/SPION alone did not show toxic effect event at high doses, proving safety of the delivery vehicle.. However, Dox loaded NPs (0.3 μg/ml and 1.3 μg/ml drug content) showed dose and time dependent toxicity. Based on the confocal microsco-py studies, internalization of NPs increases with the NP dose, incubation time and temperature. We have also observed that NPs were internalized through endosomal pathway using the endosomal markers Rab5 and Rab9. In addition, cells incubated with Dox loaded NPs exhibited higher levels of gamma-H2AX phosphorylation, p53 and Caspase activation in comparison to free Doxorubicin. Conclusion: According to our findings, du-ally responsive controlled drug release behavior makes these SPION-PNIPAM nanoparticles valuable stimuli responsive theranostic candidates

Anticancer use of nanoparticles as nucleic acid carriers

Commonly used drugs can mainly be classified as protein-based drugs such as insulin and small-molecule chemicals such as aspirin (Acetylsalicylic Acid). Search for organic drug-like molecules with high efficacy and low side-effects revealed nucleic acids as potential drugs. siRNA and miRNAs are one of the negative regulators of gene expression controlling various fundamental biological processes such as cell proliferation, stem cell division, and apoptosis. They act either by altering the stability of the mRNA transcripts and/or blocking protein translation by ribosomes. During the last decade, RNA molecules (siRNA and miRNA) and DNA fragments that code for them (shRNA or miRNA genes) were analyzed in detail to reveal their potential as new generation drugs against cancer. Accumulating data on these drugs will be discussed in the light of recent advances about the usage of nano particles as nucleic acid drug carriers

Magnetic nanoparticle based nanofluid actuation with dynamic magnetic fields

Magnetic nanoparticle suspensions and their manipulation are becoming an alternative research line and have very important applications in the field of microfluidics such as microscale flow control in microfluidic circuits, actuation of fluids in microscale, and drug delivery mechanisms. In microscale, it is possible and beneficial to use magnetic fields as actuators of such nanofluids, where these fluids could move along a gradient of magnetic field so that a micropump without any moving parts could be generated with this technique. Thus, magnetically actuated nanofluids could have the potential to be used as an alternative micro pumping system. Actuation of ferrofluid plugs with a changing magnetic field has been extensively studied in the literature. However; the flow properties of ferrofluids are sparsely investigated when the ferrofluid itself is forced to continuously flow inside a channel. As an extension of previous studies, this study aims to investigate flows of magnetic nanoparticle based nanofluids by a generated magnetic field and to compare the efficiency of the resulting system. Lauric Acid coated Super Paramagnetic Iron Oxide (SPIO-LA) was used as the ferrofluid sample in the experiments to realise actuation. Significant flow rates up to 61.8 mu L/s at nominal maximum magnetic field strengths of 300mT were achieved in the experiments. Results suggest that nanofluids with magnetic nanoparticles merit more research efforts in micro pumping. Thus, magnetic actuation could be a significant alternative for more common techniques such as electromechanical, electrokinetic, and piezoelectric actuation

Synthesis of stable gold nanoparticles using linear polyethyleneimines and catalysis of both anionic and cationic azo dye degradation

Reduction of auric acid with polyethyleneimine (PEI) provides a simple, low-cost alternative for the production of cationic gold nanoparticles (GNPs). However, linear PEI (lPEI) failed to produce small, colloidally stable GNPs, so far. Since lPEI is a polyelectrolyte, pH should be an important factor both in reduction and stabilization of GNPs and may be optimized to produce small and stable lPEI/GNPs. Cationic GNPs were produced by the direct reduction of auric acid in water with lPEI utilizing two different methods to dissolve the polymer: by protonation or at high temperature. The influence of pH on the particle formation and properties was studied over a wide pH range (3.5 to 10). The impacts of the PEI/Au mass ratio, polymer molecular weight (2.5 and 25 kDa) and post-synthetic pH on the particle properties were also studied. Best is to dissolve lPEI by protonation and to clean the GNPs via controlled centrifugal precipitation. The MW did not influence the hydrodynamic size, stability or particle shape, but low MW lPEI provided faceted particles. This simple one pot synthesis of small, stable cationic GNPs in water is a valuable, simple alternative for producing new cationic GNPs with even low molecular weight lPEI. Additionally, these GNPs were evaluated as catalysts in the degradation of methyl orange (MO) (anionic-zwitterionic) and methylene blue (MB) (cationic) azo dyes at different pH values. The fastest degradation of MO and MB was recorded at pH 7.5 and 3.5, respectively. Overall, this is a rare case where a single catalyst quickly and effectively catalyzes the degradation of both cationic and anionic dyes. This journal i

Magnetic actuation of nanofluids with ferromagnetic particles

Electromagnetically actuated microflows are generated by using ferromagnetic nanofluids containing Fe2O3 based nanoparticles. Because of their magnetic properties these nanoparticles are able to response to a magnetic field imposed along a microchannel so that a microflow could be driven. Nanofluid samples were located inside a minichannel and were directed with a magnetic field, which was induced by a solenoid wrapped around the minichannel, to drive the flow inside the minichannel, where its flow rate was also recorded. The flow rate was measured as a function of the imposed magnetic field. The corresponding pressure drop to deliver the same flow rate with an ordinary pump along the same minichannel was estimated so that the potential of this system for acting as a micropump in microfluidic applications was revealed