Gold nanostructure microelectrode arrays for in vitro recording and stimulation from neuronal networks.

An ideal microelectrode array (MEA) design should include materials and structures which exhibit biocompatibility, low electrode polarization, low impedance/noise, and structural durability. Here, the fabrication of MEAs with indium tin oxide (ITO) electrodes deposited with self-similar gold nanostructures (GNS) is described. We show that fern leaf fractal-like GNS deposited on ITO electrodes are conducive for neural cell attachment and viability while reducing the interfacial impedance more than two orders of magnitude at low frequencies (100-1000 Hz) versus bare ITO. GNS MEAs, with low interfacial impedance, allowed the detection of extracellular action potentials with excellent signal-to-noise ratios (SNR, 20.26 ± 2.14). Additionally, the modified electrodes demonstrated electrochemical and mechanical stability over 29 d in vitro.

Poly(1,4-phenylene vinylene) Derivatives with Ether Substituents to Improve Polymer Solubility for Use in Organic Light-Emitting Diode Devices.

New ether-substituted poly(1,4-phenylene vinylene) (PPV) derivatives were synthesized via Horner-Emmons coupling. The structures of the monomers and the resultant oligomers were confirmed by 1H and 13C NMR spectroscopies. The molecular weights of the oligomers were characterized by gel permeation chromatography, giving the number-average and weight-average molecular weights and the corresponding polydispersity indices. Measurements of UV-vis absorption and fluorescence were used to characterize the optical properties of the oligomers. Estimation of the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels and other electrochemical characteristics of the oligomers were investigated by cyclic voltammetry. Dialkyl and dialkoxy PPV oligomers were also prepared and characterized following the same instrumental methods used for the ether-substituted oligomers, providing a known reference system to judge the performance of the new conjugated oligomers. Devices were fabricated to analyze the electroluminescent characteristics of the oligomers in organic light-emitting diodes.

A patterned polystyrene-based microelectrode array for in vitro neuronal recordings.

Substrate-integrated microelectrode arrays (MEAs) are non-invasive platforms for recording supra-threshold signals, i.e. action potentials or spikes, from a variety of cultured electrically active cells, and are useful for pharmacological and toxicological studies. However, the MEA substrate, which is often fabricated using semiconductor processing technology, presents some challenges to the user. Specifically, the electrode encapsulation, which may consist of a variety of inorganic and organic materials, requires a specific substrate preparation protocol to optimize cell adhesion to the surface. Often, these protocols differ from and are more complex than traditional protocols for in vitro cell culture in polystyrene petri dishes. Here, we describe the fabrication of an MEA with indium tin oxide microelectrodes and a patterned polystyrene electrode encapsulation. We demonstrate the electrochemical stability of the electrodes and encapsulation, and show viable cell culture and in vitro recordings.

A non-doped phosphorescent organic light-emitting device with above 31% external quantum efficiency.

The demonstrated square-planar Pt(II)-complex has reduced triplet-triplet quenching and therefore a near unity quantum yield in the neat thin film. A non-doped phosphorescent organic light-emitting diode (PhOLED) based on this emitter achieves (31.1 ± 0.1)% external quantum efficiency without any out-coupling, which shows that a non-doped PhOLED can be comparable in efficiency to the best doped devices with very complicated device structures.

Molecular and electronic structure of cyclic trinuclear gold(I) carbeniate complexes: insights for structure/luminescence/conductivity relationships.

An experimental and computational study of correlations between solid-state structure and optical/electronic properties of cyclotrimeric gold(I) carbeniates, [Au3(RN═COR')3] (R, R' = H, Me, (n)Bu, or (c)Pe), is reported. Synthesis and structural and photophysical characterization of novel complexes [Au3(MeN═CO(n)Bu)3], [Au3((n)BuN═COMe)3], [Au3((n)BuN═CO(n)Bu)3], and [Au3((c)PeN═COMe)3] are presented. Changes in R and R' lead to distinctive variations in solid-state stacking, luminescence spectra, and conductive properties. Solid-state emission and excitation spectra for each complex display a remarkable dependence on the solid-state packing of the cyclotrimers. The electronic structure of [Au3(RN═COR')3] was investigated via molecular and solid-state simulations. Calculations on [Au3(HN═COH)3] models indicate that the infinitely extended chain of eclipsed structures with equidistant Au--Au intertrimer aurophilic bonding can have lower band gaps, smaller Stokes shifts, and reduced reorganization energies (λ). The action of one cyclotrimer as a molecular nanowire is demonstrated via fabrication of an organic field effect transistor and shown to produce a p-type field effect. Hole transport for the same cyclotrimer-doped within a poly(9-vinylcarbazole) host-produced a colossal increase in current density from ∼1 to ∼1000 mA/cm(2). Computations and experiments thus delineate the complex relationships between solid-state morphologies, electronic structures, and optoelectronic properties of gold(I) carbeniates.

Determining a performance envelope for capture of kidney stones functionalized with superparamagnetic microparticles.

BACKGROUND AND PURPOSE: Complete stone removal is important in upper tract stone surgery. Unfortunately, even with the latest technologic advances, current methods only achieve 50% to 80% complete clearance of upper tract stones at the time of primary treatment. Our group has explored the novel use of peptide-coated iron oxide superparamagnetic microparticles that bind to calcium stones, allowing for extraction of these stones with magnetic tools. We present analytic and numeric models that characterize stone attraction performance for feasible magnetic tool sizes and stone magnetization levels. MATERIALS AND METHODS: Magnetostatics equations are applied to a simplified, one-dimensional scenario of a spherical target coated with a variable amount of superparamagnetic particles, placed under the influence of a magnetic field aimed at vertical attraction (capture) of the target. Equations are parameterized in terms of (a) target size, ranging from 0.5 mm to 3 mm to represent stone sizes of interest, (b) effective magnetization per surface area delivered by the particle binding chemistry, and (c) distance to the field source. RESULTS: Target capture is predicted to be effective in the low, single-digit millimeter distance range, favoring smaller stones and then up to a practical upper limit of 3 mm diameter. Higher iron loading chemistries have a direct improvement in magnetic force and therefore increase the viability of the technique, albeit along an asymptotic trendline. CONCLUSIONS: We are able to characterize the potential for kidney stone capture via magnetic attraction. Computer-developed models show good correlation with experimental results using actual magnetized stone samples. Future research efforts can use the proposed techniques to estimate the performance impact of advanced magnetic tools and surface chemistries.

Rendering stone fragments paramagnetic with iron-oxide microparticles improves the efficiency and effectiveness of endoscopic stone fragment retrieval.

OBJECTIVES: To develop peptide-coated iron oxide-based microparticles that selectively adhere to calcium stone fragments, thereby enabling magnetic manipulation of human stone fragments. METHODS: In phase 1, human stone fragments were coated overnight with iron oxide-based microparticles. Groups of 10 coated stones (1.5-3 mm) were placed into a bladder simulator and removed cystoscopically with either an 8 Fr magnetic extraction device or a 2.4 Fr nitinol basket. In phase 2, the peptide coating was optimized and 2 stone fragment sizes (1-2 mm and 2-3 mm) were exposed to 3 separate concentrations of microparticles for 3 different incubation times. In each trial, 10 fragments were placed into a glass vial and removed using the 8 Fr magnetic device. RESULTS: In phase 1, mean total time for removal of all fragments was 53% shorter using the magnetic instrument compared with basket extraction. An average of 3.7 extractions was required to magnetically remove all fragments versus 9.4 for basket extraction. In phase 2, 18 different combinations of particle concentrations, fragment sizes, and incubation times were tested; 91% of small fragment trials and 43% of large fragment trials yielded successful fragment extraction. Of the small fragments, 100% were successfully extracted at both the middle and high particle concentrations after 2 minutes, and of the large fragments 70% and 100% were successfully extracted after 10 minutes of incubation at the lowest and highest concentrations, respectively. CONCLUSIONS: Rendering stone fragments paramagnetic with novel microparticles allows manipulation and removal using a novel magnetic device in vitro, potentially improving surgical efficacy and efficiency.