Combined Application of Prototype Ultrasound and BSA-Loaded PLGA Particles for Protein Delivery.

PURPOSE: To develop an in vitro culture system for tissue engineering to mimic the in vivo environment and evaluate the applicability of ultrasound and PLGA particle system. METHODS: For tissue engineering, large molecules such as growth factors for cell differentiation should be supplied in a controlled manner into the culture system, and the in vivo microenvironment need to be reproduced in the system for the regulation of cellular function. In this study, portable prototype ultrasound with low intensity was devised and tested for protein release from bovine serum albumin (BSA)-loaded poly(lactic-co-glycolic acid) (PLGA) particles. RESULTS: BSA-loaded PLGA particles were prepared using various types of PLGA reagents and their physicochemical properties were characterized including particle size, shape, or aqueous wetting profiles. The BSA-loaded formulation showed nano-ranged size distribution with optimal physical stability during storage period, and protein release behaviors in a controlled manner. Notably, the application of prototype ultrasound with low intensity influenced protein release patterns in the culture system containing the BSA-loaded PLGA formulation. The results revealed that the portable ultrasound set controlled by the computer could contribute for the protein delivery in the culture medium. CONCLUSIONS: This study suggests that combined application with ultrasound and protein-loaded PLGA encapsulation system could be utilized to improve culture system for tissue engineering or cell regeneration therapy.

Synergistic Effect of Growth Factor Releasing Polymeric Nanoparticles and Ultrasound Stimulation on Osteogenic Differentiation.

Mesenchymal stem cells (MSCs) have been extensively used in the tissue regeneration therapy. Ex vivo therapy with well-differentiated osteogenic cells is known as an efficient treatment for musculoskeletal diseases, including rheumatoid diseases. However, along with its high cost, the current therapy has limitations in terms of restoring bone regeneration procedures. An efficient process for the cell differentiation to obtain a large number of functionalized osteogenic cells is necessary. Therefore, it is strongly recommended to develop strategies to produce sufficient numbers of well-differentiated osteogenic cells from the MSCs. In general, differentiation media with growth factors have been used to facilitate cell differentiation. In the present study, the poly (lactic-co-glycolic acid) (PLGA) nanoparticles incorporating the growth factors were included in the media, resulting in releasing growth factors (dexamethasone and ß-glycerophosphate) in the media in the controlled manner. Stable growth and early differentiation of osteogenic cells were achieved by the PLGA-based growth factor releasing system. Moreover, low intensity pulsed ultrasound was applied to this system to induce cell differentiation process. The results revealed that, as a biomarker at early stage of osteogenic cell differentiation, Lamin A/C nuclear protein was efficiently expressed in the cells growing in the presence of PLGA-based growth factor reservoirs and ultrasound. In conclusion, our results showed that the ultrasound stimulation combined with polymeric nanoparticles releasing growth factors could potentially induce osteogenic cell differentiation.

Multilevel nonvolatile small-molecule memory cell embedded with Ni nanocrystals surrounded by a NiO tunneling barrier.

Four-level nonvolatile small-molecule 4F(2) memory cells were developed with a sandwiched device structure consisting of an upper Al electrode, upper small-molecule layer (Alq(3), aluminum tris(8-hydroxyquinoline)), Ni nanocrystals surrounded by NiO tunneling barrier, lower small-molecule layer, and bottom Al electrode. In particular, an in situ O(2)-plasma oxidation process following Ni evaporation was developed to produce uniformly stable 10 nm Ni nanocrystals surrounded by a NiO tunneling barrier embedded in the small-molecule layer. They presented a memory margin (I(on)/I(off) ratio) of approximately 1 x 10(3), a retention time of more than 10(5) s, an endurance of more than 5 x 10(2) erase-and-program cycles, and multilevel cell (MLC) operation, being a terabit nonvolatile memory-cell. A vertically double-stacked 4F(2) multilevel nonvolatile memory cell was also developed, showing a memory margin of approximately 1 x 10(3) in both the top and bottom memory cells and eight-level cell operation.

Optical and field emission properties of thin single-crystalline GaN nanowires.

Thin high-quality gallium nitride (GaN) nanowires were synthesized by a catalytic chemical vapor deposition method. The synthesized GaN nanowires with hexagonal single-crystalline structure had thin diameters of 10-50 nm and lengths of tens of micrometers. The thin GaN nanowires revealed UV bands at 3.481 and 3.285 eV in low-temperature PL measurements due to the recombination of donor-bound excitons and donor-acceptor pairs, respectively. The blue shifts of UV bands in the low-temperature PL measurement were observed, indicating quantum confinement effects in the thin GaN nanowires which have smaller diameters than the exciton Bohr radius, 11 nm. For field emission properties of GaN nanowires, the turn-on field of GaN nanowires was 8.5 V/microm and the current density was about 0.2 mA/cm(2) at 17.5 V/microm, which is sufficient for the applications of field emission displays and vacuum microelectronic devices. Moreover, the GaN nanowires indicated stronger emission stability compared with carbon nanotubes.