Towards automated molecular detection through simulated generation of CMOS-based rotational spectroscopy.

The use of CMOS sensors for rotational spectroscopy is a promising, but challenging avenue for low-cost gas sensing and molecular identification. A main challenge in this approach is that practical CMOS spectroscopy samples contain various different noise sources that reduce the effectiveness of matching techniques for molecular identification with rotational spectroscopy. To help solve this challenge, we develop a software application tool that can demonstrate the feasibility and reliability of detection with CMOS sensor samples. Specifically, the tool characterizes the types of noise in CMOS sample collection and synthesizes spectroscopy files based upon existing databases of rotational spectroscopy samples gathered from other sensors. We use the software to create a large database of plausible CMOS-generated sample files of gases. This dataset is used to help evaluate spectral matching algorithms used in gas sensing and molecular identification applications. We evaluate these traditional methods on the synthesized dataset and discuss how peak finding and spectral matching algorithms can be altered to accommodate the noise sources present in CMOS sample collection.

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.

Novel iron oxide microparticles used to render stone fragments paramagnetic: assessment of toxicity in a murine model.

PURPOSE: We developed novel peptide coated iron oxide supraparamagnetic microparticles that bind to calcium stones, allowing for extraction of these stones with magnetic tools. Urothelial and fibroblast cell lines show minimal to no toxicity when exposed to the particles. Before clinical evaluation, assessment of the in vivo systemic toxicity of the microparticles was required. This was studied in a murine model. MATERIALS AND METHODS: A total of 64 mice were exposed to different concentrations of microparticles (0.5, 1 or 5 mg/dl) intravesically or intravenously via the tail vein. Mice were sacrificed at different intervals (days 1, 3, 28 and 84). Representative samples from the brain, lung, heart, kidney and liver were evaluated histologically at each time point. The tissue distribution pattern of the particles and any degree of inflammation was noted by a clinical pathologist. Liver function tests were also performed at similar intervals. RESULTS: All mice survived until the assigned end point and appeared healthy after exposure to microparticles. In the bladder installation group no particles were seen in any organ regardless of the particle concentration instilled. In the intravenous instillation group there was tissue distribution in the liver and to a lesser extent in the lung. There was mild inflammation in the liver and lung, which was dose dependent. CONCLUSIONS: Novel iron oxide supraparamagnetic microparticles used to render stone fragments paramagnetic in the urinary collecting system did not appear to cross intact urothelial membranes. When introduced systemically, they led to minimal inflammatory changes, predominantly in the liver and lung. Additional long-term studies are required.

In vitro comparison of prototype magnetic tool with conventional nitinol basket for ureteroscopic retrieval of stone fragments rendered paramagnetic with iron oxide microparticles.

PURPOSE: We developed a prototype magnetic tool for ureteroscopic extraction of magnetized stone particles. We compared its efficiency for retrieving magnetized calcium oxalate monohydrate stone particles with that of a conventional nitinol basket from the pelvi-collecting system of a bench top ureteroscopic simulator. MATERIALS AND METHODS: Iron oxide microparticles were successfully bound to 1 to 1.5, 1.5 to 2 and 2 to 2.5 mm human calcium oxalate monohydrate stones. Several coated fragments of each size were implanted in the collecting system of a bench top ureteroscopic simulator. Five-minute timed stone extraction trials were performed for each fragment size using a back loaded 8Fr magnetic tool mounted on a 0.038-inch guidewire or a conventional basket. The median number of fragments retrieved per timed trial was compared for the magnetic tool vs the basket using the Mann-Whitney U test. RESULTS: For 1 to 1.5 mm fragments the median number retrieved within 5 minutes was significantly higher for the prototype magnetic tool than for the nitinol basket (9.5 vs 3.5, p = 0.03). For 1.5 to 2 mm fragments the magnetic tool was more efficient but the difference in the number of fragments retrieved was not statistically significant (9.5 vs 4.5, p = 0.19). For 2 to 2.5 mm fragments there was no difference between the instruments in the number retrieved (6 per group, p = 1.0). CONCLUSIONS: The prototype magnetic tool improved the efficiency of retrieving stone particles rendered paramagnetic that were less than 2 mm but showed no advantage for larger fragments. This system has the potential to decrease the number of small retained fragments after ureteroscopic lithotripsy.

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.

Novel stone-magnetizing microparticles: in vitro toxicity and biologic functionality analysis.

BACKGROUND AND PURPOSE: We have developed novel iron-based microparticles (Fe-MP) that bind to calcium oxalate stone fragments, rendering them paramagnetic. Previously, we demonstrated enhanced efficiency of stone extraction in an inanimate model using magnetic instrumentation. Before in vivo stone extraction studies, we sought to further characterize Fe-MP with regard to cellular toxicity and to assess the influence of biologic fluids on binding performance. TOXICITY: Monolayers of murine fibroblasts, human urothelium, and human transitional-cell carcinoma cells were exposed to 1 mg/mL of Fe-MP or saline via an agarose overlay. Cellular viability was assessed using neutral red staining and densitometry. Biologic functionality: Human calcium oxalate stone fragments were incubated with a solution of 1 mg/mL of Fe-MP containing varying concentrations of urine (10%-50%) or blood (0.5%-2%) for 10 minutes. Fragments were then extracted using an 8F magnetic tool. Assays of 10 stone fragments categorized as small (3-3.9 mg) or large (6-6.9 mg) were run in quadruplicate at each concentration. RESULTS: No toxicity was seen in any of the three cell lines after 48 hours of particle exposure, except in urothelial cells at the lowest cell concentration. Stone extraction success was 100% for all stones, regardless of concentration of urine or blood, and extractions were completed in less than 10 minutes. CONCLUSIONS: Preliminary toxicity testing revealed minimal to no cellular toxicity that was attributable to Fe-MP. The microparticles function well in the presence of clinically relevant concentrations of urine and blood that may be present during endoscopic stone surgery. Further toxicity and stone extraction testing in animal models is necessary.

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.

Fabrication of silver vanadium oxide and V2O5 nanowires for electrochromics.

Silver vanadium oxide (SVO) and V2O5 nanowires have been hydrothermally synthesized. The as-made nanowires are over 30 microm long and 10-20 nm in diameter. The nanowires have a layered structure with a d-spacing of 1.07 nm. The nanowires can be fabricated into free-standing and flexible sheets by suction filtration. The electrical conductivity of the SVO nanowires is 0.5 S/cm, compared to 0.08 S/cm for the V2O5 nanowires. The Li ion diffusion coefficient in the SVO nanowires was 7 times higher than that in the V2O5 nanowires. An electrochromic device was fabricated from the SVO nanowires that displayed a color-switching time of 0.2 s from the bleached state (green) to the colored state (red-brown) and 60% transmittance contrast.

Separation and recovery of intact gold-virus complex by agarose electrophoresis and electroelution: application to the purification of cowpea mosaic virus and colloidal gold complex.

Colloidal gold has been coupled to a mutant cowpea mosaic virus (CPMV), which contains 60 cysteine residues on the surface. A purification process was developed to separate the gold-containing viral nanoblocks (VNBs) from the free gold. Agarose electrophoresis was utilized to separate the mixture followed by electroelution of the desired sample to recover the intact virus. Mobility of Au-VNB and free colloidal gold was facilitated by the addition of thioctic acid (TA). 30% of the gold-containing virus was recovered after electroelution as determined by absorbance measurements. Histogram analysis of transmission electron microscopy (TEM) images demonstrated the efficient separation of gold-containing virus from free gold. TEM and scanning electron microscopy (SEM) images indicated that the virus was recovered intact. Monodisperse spherical particles of nominal size of 45 nm were observed under SEM.