Nano LIFE

Magnetic nanoparticles (MNPs) have emerged as a major platform for the formulation of magnetic vectors for nonviral gene delivery. Notably the application of "magnetofection" strategies (use of magnetic fields to increase MNP–cell interactions) can significantly enhance MNP mediated gene transfer. Despite the potential of this approach, the use of MNPs and magnetofection for gene delivery to oligodendrocytes (the cells that make and maintain myelin, the insulating sheath around nerve fibers in the central nervous system) has never been tested. Here, we prove the feasibility of using MNPs in conjunction with applied static or oscillating gradient magnetic fields (the "magnetofection" method) to deliver genes to oligodendrocytes; all applied magnetic field conditions resulted in greater transfection than the no field condition but overall transfection levels obtained were typically low (ca. < 6%). Oligodendrocyte transfection levels under all magnetic field conditions were less than a third compared with their parent cell population, the oligodendrocyte precursor cells. Our results demonstrate for the first time that, within cells of a specific neural lineage, the amenability to transfection is dependent on the differentiation status of the cell.

The complement system is an integral innate immune component that is made up of a cascade of enzymatic proteins that, once activated, results in lysis of invading pathogens, opsonization or recruitment of other innate and/or acquired immune responders, or some combination of the three. Due to the importance of the signal amplification and control points present in the cascade, complement is highly sensitive to subtle variations in initiation conditions, including nanoscale changes to molecular spacing. Using Fc-functionalized microparticles and nanoparticles, we find that activation requires a minimum threshold surface concentration of Fc of at least 20% surface coverage. This result indicates that a high surface density Fc is necessary for micro/nanoparticle complement activation through the classical pathway. In addition, the magnitude of the response was dependent on the size of the particle, with larger particles causing decreased activation. We hypothesize that a high density of Fc is needed to efficiently bind and closely appose molecular initiators of the complement cascade, from initiation to terminal complement complex formation. These fundamental studies of the interaction of microparticles and nanoparticles with the immune system suggest design rules for particle size and molecular density that impact immunostimulation through the complement system. Providing a therapeutic agent to modulate the complement response could aid a variety of treatment strategies. Engineered nanoparticles with controlled gaps between molecular activators could lead to new types of immunomodulatory agents.

Herein, we present a new flow-guided assembly approach to align and position DNA nanowires. Single or multiple drops of a λ-DNA solution were loaded from one side of template with micropad array and blown off by air flow. DNA molecules were aligned along the flow direction and well positioned under the guiding of pre-defined micropatterns. Different from other pioneering work, we focused on investigating the assembly quality, reliability and appropriateness for large-scale manufacturing. We correlated the assembly quality (alignment, patterning and the surface coverage) with the concentration of DNA in droplets and droplet evaporation and suggested appropriate process windows. With this new approach, the synthesis, alignment and patterning of nanowires may be done in a reliable and efficient manner and with high throughput.

Carbon Nanotube (CNT) ribbon is a thin layer of aligned, partially overlapping CNTs drawn from a forest of CNTs grown on a substrate. The electrical properties of the ribbon must be understood to put this material into multifunctional applications. Measurements show that CNT ribbon exhibits interesting characteristics including frequency-dependent electrical impedance. The impedance is mainly a combination of resistive and capacitive impedance. The magnitude of the impedance of ribbon increases moderately with increasing frequency then decreases significantly at higher frequency, MHz and above. An electrical model was developed to approximate the electrical impedance of the CNT ribbon. Based on this model, some important properties of the CNT ribbon can be understood. The ribbon capacitance, CNT–CNT contact resistance and resistivity can be approximated using the model. This information is useful in determining the suitability of ribbon for different applications. Methods to improve the electrical conduction of CNT ribbon are also discussed.

Introduction: Metal nanoparticles such as gold and silver nanoparticles have attracted much interest during the last decades for their special chemical and physical properties. Gold and silver nanoparticles can be functionalized with active biologic moieties like antibodies, drugs and chemicals, enabling them to react with specific cells. Furthermore, penetration and cytotoxic effects of nanoparticles can be increased by electromagnetic waves such as infrared, ultraviolet, radiofrequency and microwave. Aim: The aim of this study was to evaluate the rate of cell cytotoxicity induced by folic acid-functionalized gold and silver nanoparticles with and without microwave irradiation on cancer cells from patients with acute myeloid leukemia (AML). Method: Patients with known AML (M1, M2, M3 and M4), all recently diagnosed by histopathology, special stains and immunohistochemistry, and 4 normal persons were enrolled in the study. The blood mononuclear cell fraction was separated, so that the final concentration of neoplastic myeloid cells and normal mononuclear cells in each tube was adjusted to about 400 cells/μL. For preparation of folate-functionalized gold and silver nanoparticles, folic acid was dissolved in deionized water, added to 1 mM HAuCl₄ and 1 mM AgNO₃ solution, and incubated at 50°C for 8 h. Scanning electron micrographs, ultraviolet-visible spectrophotometer and Fourier transform infrared (FTIR) were used for confirmation of the synthesis of functionalized nanoparticles. After preparation, nanoparticles were added to cancerous and normal cell suspensions, and then incubated at 37°C for 1 h. Another experiment was carried out in the same way but with exposure to microwave irradiation for 10 s so that its temperature reached at 50°C, and then incubated at 37°C for 1 h, after which cell cytotoxicity was evaluated with MTT test. All of the tests were duplicated, and paired t-test was used to compare the mean absorbance read-out in each of the above-mentioned groups of wells. Results: The sizes of functionalized gold and silver nanoparticles were approximately 25 nm to 32 nm. After synthesis of functionalized nanoparticles, the tubes containing HAuCl₄ turned to red color, and the peak absorbance for gold nanoparticles was at 520 nm. For AgNo₃, it turned to yellow color with a peak absorbance at 420 nm. FTIR test showed connection of folic acid moieties to gold and silver surfaces. This study showed that functionalized gold nanoparticles were more toxic than functionalized silver nanoparticles on cancer and normal cells. Also, microwave irradiation was more synergic with functionalized gold nanoparticles. Furthermore, the most effectiveness score was 2.87 for functionalized silver nanoparticles without microwave irradiation and the minimum effectiveness score was 2.20 for functionalized silver nanoparticles with microwave. Conclusion: This study clearly demonstrated that although functionalized gold nanoparticles have high toxicity to cells, but silver nanoparticles without microwave irradiation are more effective because of less cytotoxic effect on normal cells.