Rapid neurogenic differentiation of human mesenchymal stem cells through electrochemical stimulation.

The neurogenic differentiation of human mesenchymal stem cells (hMSCs) has been substantially handicapped with the choice of chemical or electrical stimulations for long durations. We demonstrate an innovative strategy of stimulation with <1.0 V for <200 s to achieve hMSCs differentiation towards neural progenitor cells within 24 h and their commitment towards differentiation to neurons on day 3 with the use of three-electrode electrostimulation. Stimulated hMSCs (ES hMSCs) showed elevated expression of neural-specific markers and mitochondrial membrane potential. A voltage bias of ±0.5 V and ±1.0 V did not show any adverse effect on cell viability and proliferation, whereas cells stimulated with ±1.5 V showed an upsurge in the dead cell populations. With the progression of time after stimulation, a rise in mitochondrial membrane potential (MMP, ΔΨ M) was observed in the ES hMSCs and thereby generating intracellular reactive oxygen species (ROS), acting as a key messenger to induce neuronal differentiation. The stratagem may provide insightful handles to circumvent neurodifferentiation impediments, a focal issue for regenerative medicine.

Liposome functionalized reduced graphene oxide for rapid electrochemical sensing of bacteria.

Pathogenic bacteria represent a severe threat to global public health, particularly with the growing rate of antibiotic resistance, and, therefore, indicate a critical need for developing efficient sensing platforms. Liposome-based sensors are collocating interest due to their intrinsic fusogenic ability to fuse with the outer membrane of bacteria. However, the lack of a conducting property limits their applicability for developing biosensing platforms. In this study, we report conjugation of liposomes with reduced graphene oxide (rGO) for fabricating a rapid and sensitive biosensor for electrochemical detection of Escherichia coli (E. coli). The large surface area of rGO facilitated binding of liposomes with their surface, and the intrinsic electrical and biocompatible properties assisted electrochemical sensing of bacteria. The electrochemical response of the liposome and the rGO-liposome coated electrode shows nonconducting and conducting characteristics, respectively. A significant change in the peak current of differential pulse voltammetry with the gradual variation of bacterial density in the electrolyte was observed for the glassy carbon electrode rGO-liposome (GCE-L-rGO) surface only. The detection sensitivity of GCE-L-rGO sensors was ∼26 µA/106 cells per ml of electrolyte for varying cell densities from 3 × 103 to 3 × 104 cells/ml. The proposed sensing technique can serve as an alternative to conventional methodologies for rapid and in situ detection of bacterial load in different samples, laying the foundation for new applications in clinical diagnostics.

Electrochemically differentiated human MSCs biosensing platform for quantification of nestin and ß-III tubulin as whole-cell system.

Polydimethylsiloxane (PDMS) on ITO substrate was used to create a well with conducting surface to adhere human mesenchymal stem cells (hMSCs) and provide electrochemical stimulation for inducing their differentiation into neural-like cells. The cells that received electrochemical stimulation did not show any noticeable change in their viability and proliferation. The cell morphology of the differentiated hMSCs adherent on ITO showed outgrowth and elongation in one dimension, resembling neural-like cells. Immunocytochemistry assessment by quantifying the expression of nestin and ß-III tubulin also confirmed the differentiation of hMSCs. These differentiated hMSCs adherent on ITO were used as electrochemical biosensing platform for differential pulse voltammetry (DPV) measurement for selectively quantifying cell surface markers expressed by neural stem cells and mature neurons. The variation of nestin antibodies concentrations from 9 µU to 27 µU showed a linear increase in DPV current with a detection sensitivity of ∼28 nA/µU of antibody. Varying concentrations of ß-III tubulin antibodies from 30 µU to 210 µU showed a linear increase in DPV current with a detection sensitivity of ∼2.0 nA/µU of antibody. The highest expression level of cell surface marker corresponding to ß-III tubulin in total adherent cells on ITO was calculated. It was in the order of 10-8 U of antibodies/cell, representing the total population of mature neuron cells. This new way of detection may rapidly assess the quantitative expression of cell surface markers/antigens.

Mycotoxin detection on antibody-immobilized conducting polymer-supported electrochemically polymerized acacia gum.

Electrochemical polymerization of acacia gum (AG) was initiated by electroactive polyaniline (PANI) monomers by radical cation formation and their coupling reactions with AG molecules. R(CT) values obtained from electrochemical impedance spectroscopy analysis at various AG concentrations with PANI were drastically decreased, confirming formation of conducting AG complexes with PANI. Quantitative analysis of ochratoxin-A (OTA) detection in electrolyte was carried out on rabbit antibody-immobilized PANI and PANI-AG matrices. The observed sensitivities of 50, 150, and 250 mg AG-added PANI matrix-based platforms were 3.3 ± 0.5, 10.0 ± 0.5, and 12.7 ± 0.5 µA/ng/ml, respectively. The sensitivity of only PANI electrodes was 2.6 ± 0.3 µA/ng/ml, which was relatively lower than AG-added PANI. This increase was due to the presence of glycan functional groups in AG molecules that supported the retention of activity of antibodies. In addition, enhanced electron transportation at AG-PANI film surface was observed due to formation of an electroactive polymer film of two different electroactive functions to contribute toward enhancement in the detection sensitivity.

Performance improvement of dye-sensitized glass powder added TiO2 solar cells.

The effect of two different types of glass powder added TiO2 hydride photoelectrode in performance of dye sensitize solar cell (DSSC) had been studied at different wt.%. TiO2 particles diffusion and possible attachment with Si atoms was observed with field-emission scanning electron microscopy (FE-SEM) and it strongly depends on characteristics of glass. Short circuit current (I(sc)) was increased with increasing the wt.% up to 5% of glass powder and further increase in wt.% ratio had decreased the I(sc). Maximum increase upto 32 and 45% in the efficiently was observed at 5 wt.% of glass powder in TiO2 for low temperature (LTG) and high temperature glass (HTG) powder, respectively. Adding glass powder in TiO2 can increase light scattering properties of hybrid electrode and can also create an energy barriers of SiO2 which prevents the recombination reactions, hence; an increase in efficiency observed.

High pressure plasma treatment for controlling the surface activity and optical properties of TiO2 nanoparticles.

The effect of high pressure radio frequency (RF) plasma treatment on TiO2 surface and photocatalytic property has been investigated. X-ray photoelectron spectroscopy (XPS) measurements have shown the two different oxidation states of oxygen in the untreated TiO2 powder. Its relative proportion changes with the different dose of plasma treatments. The proportion of Ti3+ surface states also changes after plasma treatment and strongly depends on combination of plasma power and treatment time. The photocatalytic activity of plasma-untreated and -treated samples was measured by observing the relative degradation of methylene blue. The result showed about 50% increase in photoactivity at the sample treated with 10 W RF power plasma. Low power plasma treatment is a more efficient process for achieving a photoactive surface. The effect of total dose (power and treatment time) and power has been also studied to modify the surface activity of TiO2 nanoparticles.

Use of Biocompatible Sorafenib-gold Nanoconjugates for Reversal of Drug Resistance in Human Hepatoblatoma Cells.

The present study identifies the potential of highly biocompatible SF-GNP nano-conjugate to enhance the chemotherapeutic response to combat drug resistance in cancer cells. We developed a stable colloidal suspension of sorafenib-gold nanoconjugate (SF-GNP) of <10 nm size in aqueous medium for reverting the cancer drug resistance in SF-resistant HepG2 cells in a 3D ex-vivo model system. In-vivo biocompatibility assay of SF-GNPs showed absence of systemic toxicological effects including hematological, biochemical and histological parameters. More importantly, the histopathological analysis of vital organs such as liver, brain, lung, kidney and heart showed very least or no sign of inflammation, cell infiltration, necrosis, tissue disorganization or fibrotic reactions after intra-peritoneal administration of SF-GNP nanoconjugates in animals. However, SF-GNP nanoconjugates significantly reduced (>80%) the percentage cell survival and the size and number of SF resistant solid tumor colonies of HepG2 cells in 3D model system. The exposure of SF-GNP nanoconjugate to SF resistant HepG2 cell colonies also provided evidence for anti-proliferative effect and reversal of drug resistance by elucidating the molecular regulatory mechanisms of extracellular matrix factor (CD147), tumor growth factor (TGF-ß), hepatoma upregulated protein (hURP) and drug transporter (ABCG-2).

Control of bio-MEMS surface chemical properties in micro fluidic devices for biological applications.

Surface chemistry of silicon/glass based bio-MEMS was controlled by depositing plasma polymerized acrylic acid (ppAc) films at two different electrode positions in a two-stage plasma reactor. AFM and XPS were used to characterize the surface roughness and surface chemistry of the films, respectively. The surface of bio-MEMS was highly functionalized with carboxylic/ester functionalities with a very good surface uniformity. The proportion of carbon atoms as C-OX, C(==O)OX functionalities was decreased and an increase in C==O functionalities was observed when the electrode position was increased from the mesh. These functionalized bio-MEMS devices have advantages in fabrication of reusable micro fluidic devices and the variation of fluid velocity by changing the surface properties may be used to develop a micro-mixing system to control the mixing ratio of different fluids for different biological and chemical applications.

Strategies to prepare TiO2 thin films, doped with transition metal ions, that exhibit specific physicochemical properties to support osteoblast cell adhesion and proliferation.

Metal ion doped titanium oxide (TiO2) thin films, as bioactive coatings on metal or other implantable materials, can be used as surfaces for studying the cell biological properties of osteogenic and other cell types. Bulk crystallite phase distribution and surface carbon-oxygen constitution of thin films, play an important role in determining the biological responses of cells that come in their contact. Here we present a strategy to control the polarity of atomic interactions between the dopant metal and TiO2 molecules and obtain surfaces with smaller crystallite phases and optimal surface carbon-oxygen composition to support the maximum proliferation and adhesion of osteoblast cells. Our results suggest that surfaces, in which atomic interactions between the dopant metals and TiO2 were less polar, could support better adhesion, spreading and proliferation of cells.

Growth, differentiation, and migration of osteoblasts on transparent Ni doped TiO2 thin films deposited on borosilicate glass.

A simple and cost effective dip coating method was used to deposit thin films of amorphous (AM) or anatase (AN) titanium dioxide (TiO(2)) on borosilicate glass substrates, either with or without prior doping of TiO(2) with nickel (Ni) cations by a specially designed sol gel technique. The objective of the study was to compare the physicochemical and biological properties of these films and assess their use in orthopedic implants or for in vitro cell biological studies. Analytical techniques such as XRD and XPS, in combination with ATR-FTIR and SEM revealed that only AN films, prepared by controlled heating up to 450°C, irrespective of prior doping with Ni, contained significant crystalline structures of variable morphologies. This observation could be linked to the carbon and oxygen contents and the availability of functional groups in the films. Cell biological studies revealed that Ni doping of TiO(2) in both AM and AN films improved the adhesion, spreading, proliferation, differentiation, and migration of MC3T3 cells. Our studies provide a new approach to prepare optically transparent metal surfaces, with tunable physicochemical properties, which could be suitable for eliciting optimal osteoinductive cell responses and permit the detailed in vitro cell biological studies of osteoblasts.

Chitosan/polyaniline hybrid conducting biopolymer base impedimetric immunosensor to detect Ochratoxin-A.

Chitosan (CS)-polyaniline (PANI) hybrid conducting biopolymer film was obtained on indium-tin-oxide (ITO) electrode using electrochemical polymerization process. Fourier transform infrared (FT-IR) spectra of PANI-CS had showed covalent and hydrogen binding between PANI and CS molecules. Electrochemical impedance spectroscopy (EIS) measurements had showed low charge transfer resistance (R(CT)) of PANI-CS and PANI. Successive rabbit antibody (IgGs) immobilization on PANI-CS, CS and PANI matrixes surface were confirmed with FT-IR and EIS measurements. Ochratoxin-A (OTA) interaction with IgGs had increased R(CT) values and showed linear response up to 10 ng/mL OTA concentration in electrolyte. Relative change in R(CT) was higher in PANI-CS due to higher proportion of carboxylic and hydroxyl functionalities at PANI-CS matrix surfaces. The absolute sensitivity of PANI, CS, and PANI-CS were 16+/-6, 22+/-9 and 53+/-8 Omega mL/ng, respectively derived from slope of linear response up to 10 ng/mL with 1 ng/mL minimum detection limit.

XPS and SPR analysis of glycoarray surface density.

Despite the fact that the carbohydrate microarray has seen increasing use within the field of glycobiology, the surface chemistry of the glycoarray remains largely unexplored. Motivated by the need to develop surface analytical techniques to characterize carbohydrate-modified surfaces, we developed a quantitative X-ray photoelectron spectroscopy (XPS) and surface plasmon resonance imaging (SPR imaging) method to study glycan biosensors. We performed a comparative analysis on the relative coverage of mixed self-assembled monolayers (SAMs) on gold, consisting of a thiol-functionalized trimannoside (Manalpha1,2Manalpha1,2Manalpha-OEG-SH) at varying concentrations (0-100%) mixed separately with two thiol-containing polyethylene glycol oligomers. XPS C1s core level analysis was used to identify the O-C-O functionality unique to the carbohydrate acetal moiety and to separate and quantify the relative coverage of sugar in carbohydrate/OEG mixed SAMs. XPS spectra of the mixed SAMs demonstrated a proportional increase in the acetal signature of the glycan with increasing sugar concentration. To relate surface glycan density with biological function, we carried out a kinetic analysis of Concanavalin A (ConA) binding to SAMs of varying densities of carbohydrate using SPR imaging. We observed protein binding that was highly dependent on both glycan density and the nature of the OEG-thiol used in the mixed self-assembly. These results illustrate the utility of surface analytical techniques such as XPS and SPR in carbohydrate biosensor characterization and optimization.