Facile fabrication of ordered nanostructures from protruding nanoballs to recessional nanosuckers via solvent treatment on covered nanosphere assembled monolayers.

We present a facile lithographic nanosphere production process by laminating a nanosphere monolayer with a UV resin and applying various gentle solvent treatments to produce "bottom-up" and "bottom-down" nonclose-packed patterns and investigate their practical applications in nanolenses for optical display and nanosuckers for adhesion. The solvents effect depending on its solubility parameter and solubility tendency toward the interior polystyrene nanospheres was discussed. The polymer-based nanosucker pattern displays shear adhesion force as high as 75.2 N/cm(2).

Fabrication of "electroactive cells" using bio-inspired polydopamine-derived carbon nanoparticles for manipulation of cells with electrical stimulation.

In this study, we report some bio-inspired carbon nanoparticles (CNPs) that exhibit high fluorescence quantum yields, good conductivity, excellent dispersion in aqueous solution, high cell-uptake efficiency, and no cytotoxicity as well. We were inspired by mussels' adhesive components to synthesize polydopamine nanoparticles and then use a carbonization process to prepare fluorescent CNPs. Using some surfactants, we could control the sizes of CNPs and increase their dispersion in water. Fluorescence spectroscopy confirmed the excitation of CNPs at 360 nm and emission of blue light with a 400-450 nm wavelength. High quantum yields of greater than 20% were also measured. Transmission electron microscopy proved that the addition of surfactants could shrink particles to several nanometers in size. The fluorescent and conductive CNPs were applied to stain L929 fibroblast cells in vitro, finding no harmful effects on cells. Due to the polydopamine-derived CNPs' good electrical, fluorescent, and biocompatible response, we designed a platform to manipulate the cells after endocytosis of conductive CNPs to observe the effects of electrical stimulation on cell attachment, cell growth, and cell death. The nanoparticles endocytosed by cells seemed more easily attracted to the electric field, leading to enhanced cell attachment and growth. Therefore, CNP uptake can increase the attachment of cells onto a conductive plate electrode in a short time (within 10 min at 4°C). When the source of the electric field was changed to rod electrodes in the medium, cells that had been pre-adsorbed onto a non-conductive plate were desorbed from the plate and destroyed. Therefore, addition of CNPs during cell incubation can allow control of cell growth and death via manipulation of electric fields.

A new technique for separating platelet-rich plasma by a copolymer device － without a centrifugation process.

BACKGROUND: Platelet-rich plasma (PRP) is beneficial for clinical applications in various medical fields. Although commercial PRP preparation kits are already available in the market, most of these kits employ centrifugation. METHODS: We used a new cationic copolymer coating on a polyurethane (PU) sponge to promote platelet separation from the blood. This copolymer showed no cytotoxicity against cell viability or hemolysis. We further evaluated the efficiency of the new PRP preparation device by comparing it with that of a commercially available kit (RegenKit-THT). RESULTS: We demonstrated that PRP obtained using copolymer device contains high concentrations of platelets and angiogenic growth factors (epidermal growth factor, vascular endothelial growth factor-A, growth differentiation factor 2, and interleukin-8). The separated PRP also displayed beneficial effects on cell migration, angiogenesis, and matrix metalloproteinase gene expression. CONCLUSION: Based on these results, we developed a cationic copolymer-coated PU sponge as a PRP preparation device without the need for any centrifugation.

The surface modification of silver nanoparticles by phosphoryl disulfides for improved biocompatibility and intracellular uptake.

In order to enhance the biocompatibility and cell affinity of metal nanoparticles for biosensing and drug delivering applications, we prepared the phospholipid derivatives containing disulfide groups to modify silver nanoparticle surfaces. By adding sodium borohydride to reduce both disulfide bonds of the derivatives and silver ions simultaneously, the generated thiol groups can be reacted with newborn silver atoms immediately to generate nanoclusters. The assemblies consisted of either phosphorylcholine (PC) or phosphorylethanolamine (PE) head groups, which made the silver clusters biocompatibile. Transmission electron microscope (TEM) and optical absorption spectra assisted in modulating reaction conditions, demonstrating that a surfactant/Ag ratio of 0.4 led to the formation of uniform, well-dispersed spherical particles about 3.8 nm in diameter. X-ray photoelectron spectra and infrared spectra also illustrated the elemental and molecular structures of nanoparticles. The insertion of rhodamine dye into the surfactant layer enabled the nanoparticles to be used as a fluorescent probe. In cell culture tests, the nanoparticles were internalized into platelet or fibroblast cells in a short period of incubation without harming the cells.

Preparation of polyaniline-modified electrodes containing sulfonated polyelectrolytes using layer-by-layer techniques.

Polyaniline (PAni) has been used frequently for the construction of biosensors. However, a prime limitation is its instability at basic or neutral pH because of the loss of its electrochemical activity and conductivity. In this study, three available sulfonated polyanions: Nafion, poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS) serving as the counterion and providing an acidic microenvironment to stabilize PAni, are used to fabricate a sensor for ammonium ion detection. Nafion used to be a common ion-sensitive membrane due to its high proton conductivity. However, its high cost and limited solubility has constrained its uses. PVS and PSS are water-soluble polymers, easily incorporating with PAni to form the composites. Surface analysis by electron spectroscopy for chemical analysis (ESCA) and scanning electron microscope (SEM), and the electrochromic property for the PAni composites provided the convenient tools to characterize the electrode fabrication. On the aspect of sensing the ammonium ions, the modified electrodes exhibited electroactivity of PAni in ammonium ion detection and also showed the linear dependence of reduction current on the ammonium ion concentration. The pH effect on the sensing response was also evaluated and found insignificant to the response (ranging from pH 6.9-7.6). For increasing the stability of the electrodes, the diazo-resin (DAR) was introduced to the coat on the outmost layer and then cured by UV irradiation, giving the covalent network between the layers of polyelectrolytes. The PSS-doped PAni electrode was found to perform detection sensitivity in the linear range of 0-100mM of ammonium ion concentration.

Self-assembled biomimetic monolayers using phospholipid-containing disulfides.

Several phospholipid-based disulfide molecules were synthesized and attached onto the gold-coated silicon wafer using the self-assembling method. The syntheses of these surface-modifying agents were conducted by introducing bromoethylphosphorate (PBr), phosphorylcholine (PC) or phosphorylethanolamine (PE) groups on the terminals of a dialkyl disulfide. After disulfides adsorption onto gold substrate surfaces, the composition, the film thickness, and the conformational order of self-assembled monolayer surfaces were explored and discussed in detail based on reflection-absorption infrared spectroscopy, contact angle measurement, Auger electron spectroscopy, X-ray photoelectron spectroscopy, and so on. The monolayer having the PBr end group could also be converted to a PC surface by treating with trimethylamine. The model functional surfaces of Au-SC11-PC, -PE, -PBr, -OH or corresponding mixed layers were used to mimic biomembrane surfaces. The monolayer having PC groups was found to reduce fibrinogen adsorption as evaluated from protein adsorption experiments using quartz crystal microbalance. It also showed relatively low platelet adherence compare to the glass, PBr and PE surfaces. The cell viability test also revealed that the PC surface displayed lower cytotoxicity than other surfaces.