Cell detection and counting through cell lysate impedance spectroscopy in microfluidic devices

Cell-based microfluidic devices have attracted interest for a wide range of applications. While optical cell counting and flow cytometry-type devices have been reported extensively, sensitive and efficient non-optical methods to detect and quantify cells attached over large surface areas within microdevices are generally lacking. We describe an electrical method for counting cells based on the measurement of changes in conductivity of the surrounding medium due to ions released from surface-immobilized cells within a microfluidic channel. Immobilized cells are lysed using a low conductivity, hypotonic media and the resulting change in impedance is measured using surface patterned electrodes to detect and quantify the number of cells. We found that the bulk solution conductance increases linearly with the number of isolated cells contributing to solution ion concentration. The method of cell lysate impedance spectroscopy is sensitive enough to detect 20 cells microL(-1), and offers a simple and efficient method for detecting and enumerating cells within microfluidic devices for many applications including measurement of CD4 cell counts in HIV patients in resource-limited settings. To our knowledge, this is the most sensitive approach using non-optical setups to enumerate immobilized cells. The microfluidic device, capable of isolating specific cell types from a complex bio-fluidic and quantifying cell number, can serve as a single use cartridge for a hand-held instrument to provide simple, fast and affordable cell counting in point-of-care settings.     

Cell encapsulating droplet vitrification

The capability to encapsulate single cells in droplets while retaining high cell viability (>90%) has great impact on tissue engineering, high-throughput screening, as well as clinical diagnostics and therapeutics. We demonstrate a novel method to vitrify a small number of cells using cell-encapsulating droplets. The method allows vitrification at low cryoprotectant concentration (1.5 M propanediol and 0.5 M trehalose), similar to that used in slow freezing protocols. The method was successfully applied to five different mammalian cell types: AML-12 hepatocytes, NIH-3T3 fibroblasts, HL-1 cardiomyocytes, mouse embryonic stem cells, and RAJI cells.     

Neutral Higgs sector of the MSSM with explicit CP violation and non-holomorphic soft breaking

Using the effective potential method, we computed one-loop corrections to the mass matrix of neutral Higgs bosons of the Non-Holomorphic Supersymmetric Standard Model (NHSSM) with explicit CP violation, where the radiative corrections due to the quarks and squarks of the third generation were taken into account. We observed that the non-holomorphic trilinear couplings can compete with the holomorphic ones in CP violating issues for the mass and mixing of the neutral Higgs bosons.     

Synthesis, characterization and biological evaluation of a novel Cu(II) complex with the mixed ligands 2,6-pyridinedicarboxylic acid and 2-aminopyridine

A novel bridged binuclear Cu(II) complex with mixed ligands, di-μ-(2-aminopyridine(N,N′))-bis[(2,6-pyridinedicarboxylate)aquacopper(II)] tetrahydrate, formulated as [Cu(μ-ap)(dipic)(H₂O)]₂·4H₂O (1) (dipic = 2,6-pyridinedicarboxylate, ap = 2-aminopyridine), has been synthesized and characterized by elemental, spectral (IR and UV–Vis.), thermal analysis, magnetic measurements and single crystal X-ray diffraction analysis. The central Cu(II) ion resides on a centre of symmetry in a distorted square-pyramid coordination environment comprising of two N atoms, one from dipic and one from the ap ring, two carboxylate O atoms from dipic, and one O atom from water. Intermolecular N–HO and O–HO hydrogen bonds and π–π stacking interactions seem to be effective in the stabilization of the crystal structure. The free ligands and the complex were also evaluated for their antimicrobial and radical scavenging activities (DPPH = 1,1-diphenyl-2-picrylhydrazyl hydrate) using in vitro microdilution methods. Antimicrobial screening of the free ligands and their complex showed that the free ligands and the complex possess antifungal activity against Candida sp.     

Determination of pK a of benzoic acid- and p-aminobenzoic acid-modified platinum surfaces by electrochemical and contact angle measurements

Acidity constant values of benzoic acid (BA)-modified platinum electrode (Pt-BA) and p-aminobenzoic acid (pABA)-modified platinum electrode (Pt-NHBA) surfaces were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and contact angle measurements (CAM). Diazonium tetrafluoroborate salt reduction and pABA oxidation reactions were used to prepare (Pt-BA) and (Pt-NHBA) surfaces, respectively. Both surfaces exhibited pH dependence with [Fe(CN)₆]^3?/4? redox probe solutions at different pH; this allowed us to estimate the surface pK _a values. Acidity constants for Pt-BA surface were found to be pK _a (3.09 ± 0.25), (4.89 ± 0.11), and (3.91 ± 0.54) by CV, EIS, and CAM techniques, respectively, while the values for Pt-NHBA surface were pK _a (3.16 ± 0.45), (4.24 ± 0.40), and (5.64 ± 0.12). The Pt-BA surface pK _a values were lower in CV and CAM measurements relative to the bulk solution of BA, while a higher value was observed in EIS for Pt-BA surface. The pK _a values determined for Pt-NHBA surface via both CV and EIS were lower than the bulk value; however, the result obtained from CAM was one unit higher than pK _a of bulk pABA.     

Insulator-to-metal transition in selenium-hyperdoped silicon: observation and origin

Hyperdoping has emerged as a promising method for designing semiconductors with unique optical and electronic properties, although such properties currently lack a clear microscopic explanation. Combining computational and experimental evidence, we probe the origin of sub-band-gap optical absorption and metallicity in Se-hyperdoped Si. We show that sub-band-gap absorption arises from direct defect-to-conduction-band transitions rather than free carrier absorption. Density functional theory predicts the Se-induced insulator-to-metal transition arises from merging of defect and conduction bands, at a concentration in excellent agreement with experiment. Quantum Monte Carlo calculations confirm the critical concentration, demonstrate that correlation is important to describing the transition accurately, and suggest that it is a classic impurity-driven Mott transition.     

Assesment of dimethyl phthalate removal from aqueous phase using barium hexaferrite containing magnetic beads

The barium hexaferrite (BaFe(12)O(19)) containing magnetic poly (ethylene glycol dimethacrylate-vinyl pyridine; mag-poly [EGDMA-VP]) beads (average diameter=53-212 μm) were synthesized and characterized. Their use as an adsorbent in the removal of dimethyl phthalate (DMP) from an aqueous solution was investigated. The mag-poly (EGDMA-VP) beads were prepared by copolymerizing of 4-vinyl pyridine (VP) with ethylene glycol dimethacrylate (EGDMA). The mag-poly (EGDMA-VP) beads were characterized by N(2) adsorption/desorption isotherms (BET), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), elemental analysis, scanning electron microscope (SEM), and swelling studies. At a fixed solid/solution ratio, the various factors affecting the adsorption of DMP from aqueous solutions such as pH, initial concentration, contact time, and temperature were analyzed. The maximum DMP adsorption capacity of the mag-poly (EGDMA-VP) beads was determined as 96.2 mg/g at pH 3.0, 25 °C. All the isotherm data can be fitted with both the Langmuir and the Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The thermodynamic parameters obtained indicated the exothermic nature of the adsorption. The DMP adsorption capacity did not change after 10 batch successive reactions, demonstrating the usefulness of the magnetic beads in applications.     

TiO2 embedded hydrothermally synthesized carbon composite as interlayer for lithium-sulfur batteries

Journal of Solid State Electrochemistry - Lithium-sulfur battery chemistry is one of the best alternatives to meet the demand of future electric vehicles providing high theoretical capacity and...     

Removal of copper (Cu2+) from water by sulfonated cellulose

Water insoluble sulfonated cellulose was prepared and applied for Cu²⁺ removal from water. The effects of sorbent dose, initial solution pH, temperature and initial Cu²⁺ concentration on the removal performance of sulfonated cellulose were investigated. Isothermal data were modeled with the Langmuir and Freundlich isotherm models. The Cu²⁺ sorption onto sulfonated cellulose followed the Langmuir isotherm model with the maximum sorption capacity of 8.2?mg-Cu²⁺/g. Removal of Cu²⁺ showed rapid initial kinetics; in 3?min removal of Cu²⁺ reached equilibrium status. Thermodynamic study revealed an exothermic sorption process. In addition, sulfonated cellulose is a kind of green and renewable sorbent because it can be easily regenerated by 0.1?M HCl.