Arūnas Ramanavičius

Capacitive micromachined ultrasound transducer (cMUT) for immunosensor design

An affinity sensor based on a capacitive micromachined ultrasound transducer (cMUT) is reported by this Communication. The cMUT micromembrane arrays modified with adsorbed bovine leukemia virus protein gp51 were applied as a biological recognition part. The cMUT-based sensor is shown to be sensitive to the antibodies against bovine leukemia virus protein gp51 (anti-gp51). Two different concentrations of anti-gp51-containing samples and one blank sample without anti-gp51 were tested. The sensitivity of cMUT-based immunosensor is comparable with the sensitivity of a quartz microbalance-based immunosensor. The cMUT array provides a multi-channel system for the measurement of analytical signal. Moreover, two different characteristics--the resonance frequency shift (Deltaf) and the shift of the real part of the electromechanical impedance (DeltaRe)--could have been evaluated simultaneously. Both analytical signals are informative and can be applied for the estimation of immune complex formation. We found the performance of such a system being potentially superior over some other immunosensing techniques. It is more rapid than electrochemical techniques and provides two different informative parameters.

A New Experimental Model for Neuronal and Glial Differentiation Using Stem Cells Derived from Human Exfoliated Deciduous Teeth

Stem cells isolated from human adult tissues represent a promising source for neural differentiation studies in vitro. We have isolated and characterized stem cells from human exfoliated deciduous teeth (SHEDs). These originate from the neural crest and therefore particularly suitable for induction of neural differentiation. We here established a novel three-stage protocol for neural differentiation of SHEDs cells. After adaptation to a serum-free and neurogenic environment, SHEDs were induced to differentiate. This resulted in the formation of stellate or bipolar round-shaped neuron-like cells with subpopulations expressing markers of sensory neurons (Brn3a, peripherin) and glia (myelin basic protein). Commercial PCR array analyses addressed the expression profiles of genes related to neurogenesis and cAMP/calcium signalling. We found distinct evidence for the upregulation of genes regulating the specification of sensory (MAF), sympathetic (midkine, pleitrophin) and dopaminergic (tyrosine hydroxylase, Nurr1) neurons and the differentiation and support of myelinating and non-myelinating Schwann cells (Krox24, Krox20, apolipoprotein E). Moreover, for genes controlling major developmental signalling pathways, there was upregulation of BMP (TGF β-3, BMP2) and Notch (Notch 2, DLL1, HES1, HEY1, HEY2) in the differentiating SHEDs. SHEDs treated according to our new differentiation protocol gave rise to mixed neuronal/glial cell cultures, which opens new possibilities for in vitro studies of neuronal and glial specification and broadens the potential for the employment of such cells in experimental models and future treatment strategies.

Insights into a Hole Transfer Mechanism between Glucose Oxidase and a p-type Organic Semiconductor

This manuscript describes a bioelectrochemical application of a new class of electrochemically generated hole-transporting (p-type) polymeric semiconductors (HTPS), which are based on a carbazole core and the oxiran and thiiran reactive groups. Electrode based on transparent layer of indium tin oxide was electrochemically modified with a layer of HTPS and a monolayer of covalently immobilized glucose oxidase (GOx). The HTPS/GOx-based electrode was investigated for an evaluation of direct hole-transfer between the enzyme and electrode at a bio-electrochemically relevant potential via HTPS layer. The broad linear relationship between the peak-current density and glucose concentration from 2 to 15mM and high stability of ITO/poly-CzS/GOx-electrode was observed. Moreover, it was determined that charge transfer rate constants are reliable for the establishment of advanced electron transfer between enzyme and electrode for the application of this HTPS/GOx-based electrode in long-lived biofuel cells and amperometric biosensors.

Evaluation of Competence Phenomenon of Yeast Saccharomyces cerevisiae by Lipophilic Cations Accumulation and FT-IR Spectroscopy. Relation of Competence to Cell Cycle

Capability of taking up exogenous DNA of yeast Saccharomyces cerevisiae cells was studied by lipophilic cations accumulation and FT-IR spectroscopy. The increase in permeability of the yeast cells treated with Li+ ions was observed. The changes in the cell wall structure detected by FT-IR spectra were associated with transformability of yeast cells. The presence of a population of cells with buds with a higher permeability to TPP cations was determined. Relationship between transformation efficiency of yeast Saccharomyces cerevisiae and cell cycle was determined. Yeast cells in the S-phase of cell cycle showed an enhanced perception to exogenous DNA. An increase was associated with physiological and permeability properties of yeast cells. The phenomenon of natural competence is supposed to occur in yeast cells.