Quantitative characterization of nanoparticles in blood by transmission electron microscopy with a window-type microchip nanopipet.

Transmission electron microscopy (TEM) is a unique and powerful tool for observation of nanoparticles. However, due to the uneven spatial distribution of particles conventionally dried on copper grids, TEM is rarely employed to evaluate the spatial distribution of nanoparticles in aqueous solutions. Here, we present a microchip nanopipet with a narrow chamber width for sorting nanoparticles from blood and preventing the aggregation of the particles during the drying process, enabling quantitative analysis of their aggregation/agglomeration states and the particle concentration in aqueous solutions. This microchip is adaptable to all commercial TEM holders. Such a nanopipet proves to be a simple and convenient sampling device for TEM image-based quantitative characterization.

Heat-activated sustaining nitric oxide release from zwitterionic diazeniumdiolate loaded in thermo-sensitive liposomes.

Zwitterionic diazeniumdiolate, a nitric oxide precursor, was dissolved in basic buffer solution (pH=9.0) and encapsulated in thermo-sensitive liposomes composed of phospholipids of different sensitive temperatures. The basic intra-liposomal environment dramatically delayed spontaneous NO release. When the liposomes were placed in physiological buffer solution and temperatures were increased to the sensitive temperatures of the phospholipids' membranes, extra-liposomal protons started to influx to collapse the pH gradient and subsequently induce a significant NO release. Moreover, the presence of a stronger pH gradient when the liposomes were applied to a more acidic environment caused a higher proton influx driving force to trigger the influx of protons and, subsequently, NO release. In this work, we demonstrate that thermo-sensitive liposomes can be used to create a stable pH gradient in a nanoenvironment entrapping zwitterionic diazeniumdiolate for sustained and heat/acid-activated NO release.

Thermosensitive liposomes entrapping iron oxide nanoparticles for controllable drug release.

Iron oxide nanoparticles can serve as a heating source upon alternative magnetic field (AMF) exposure. Iron oxide nanoparticles can be mixed with thermosensitive nanovehicles for hyperthermia-induced drug release, yet such a design and mechanism may not be suitable for controllable drug release applications in which the tissues are susceptible to environmental temperature change such as brain tissue. In the present study, iron oxide nanoparticles were entrapped inside of thermosensitive liposomes for AMF-induced drug release while the environmental temperature was maintained at a constant level. Carboxyfluorescein was co-entrapped with the iron oxide nanoparticles in the liposomes as a model compound for monitoring drug release and environmental temperature was maintained with a water circulator jacket. These experiments have been successfully performed in solution, in phantom and in anesthetized animals. Furthermore, the thermosensitive liposomes were administered into rat forearm skeletal muscle, and the release of carboxylfluorescein triggered by the external alternative magnetic field was monitored by an implanted microdialysis perfusion probe with an on-line laser-induced fluorescence detector. In the future such a device could be applied to simultaneous magnetic resonance imaging and non-invasive drug release in temperature-sensitive applications.

Three-dimensional tracking and temporal analysis of liposomal transport in live cells using bright-field imaging.

Gold nanoparticles (AuNPs) confined in liposomes of diameters around 200 nm produce strong scattering signal owing to surface plasmon resonance, and therefore bright-field optical tracking of the AuNP-encapsulating liposomes can be conducted in living cells. Using an optical profiling technique called noninterferometric wide-field optical profilometry and a bright-field tracking algorithm, the polynomial-fit Gaussian weight method, we analyze three-dimensional (3D) motion of such liposomes in living fibroblasts. The positioning accuracy in three dimensions is nearly 20 nm. We tag the liposome membranes with fibroblast growth factor-1 and reveal the intracellular transportation processes toward or away from the nucleus. On the basis of a temporal analysis of the intracellular 3D trajectories of AuNP-encapsulating liposomes, we identify directed and diffusive motions in the transportation processes.