Biosynthesis enhancement of tropodithietic acid (TDA) antibacterial compound through biofilm formation by marine bacteria Phaeobacter inhibens on micro-structured polymer surfaces

Although aquaculture is a major player in current and future food production, the routine use of antibiotics provides ample ground for development of antibiotic resistance. An alternative route to disease control is the use of probiotic bacteria such as the marine bacteria Phaeobacter inhibens which produces tropodithietic acid (TDA) that inhibit pathogens without affecting the fish. Improving conditions for the formation of biofilm and TDA-synthesis is a promising avenue for biocontrol in aquaculture. In this study, the biosynthesis of TDA by Phaeobacter inhibens grown on micro-structured polymeric surfaces in micro-fluidic flow-cells is investigated. The formation of biofilms on three surface topographies; hexagonal micro-pit-arrays, hexagonal micro-pillar-arrays, and planar references is investigated. The biomass on these surfaces is measured by a non-invasive confocal microscopy 3D imaging technique, and the corresponding TDA production is monitored by liquid chromatography mass spectrometry (LC-MS) in samples collected from the outlets of the microfluidic channels. Although all surfaces support growth of P. inhibens, biomass appears to be decoupled from total TDA biosynthesis as the micro-pit-arrays generate the largest biomass while the micro-pillar-arrays produce significantly higher amounts of TDA. The findings highlight the potential for optimized micro-structured surfaces to maintain biofilms of probiotic bacteria for sustainable aquacultures.

Using Impedance Flow Cytometry for Rapid Viability Classification of Heat-Treated Bacteria

In the future, rapid electrical characterization of cells with impedance flow cytometry promises to be a fast and accurate method for the evaluation of cell properties. In this paper, we investigate how the conductivity of the suspending medium along with the heat exposure time affects the viability classification of heat-treated E. coli. Using a theoretical model, we show that perforation of the bacteria membrane during heat exposure changes the impedance of the bacterial cell from effectively less conducting than the suspension medium to effectively more conducting. Consequently, this results in a shift in the differential argument of the complex electrical current that can be measured with impedance flow cytometry. We observe this shift experimentally through measurements on E. coli samples with varying medium conductivity and heat exposure times. We show that increased exposure time and lower medium conductivity results in improved classification between untreated and heat-treated bacteria. The best classification was achieved with a medium conductivity of 0.045 S/m after 30 min of heat exposure.

Rarely naturalized, but widespread and even invasive: the paradox of a popular pet terrapin expansion in Eurasia

The North American terrapin, the red-eared slider, has globally recognized invasive status. We built a new extensive database using our own original and literature data on the ecology of this reptile, representing information on 1477 water bodies throughout Eurasia over the last 50 years. The analysis reveals regions of earliest introductions and long-term spatio-temporal dynamics of the expansion covering now 68 Eurasian countries, including eight countries reported here for the first time. We established also long-term trends in terms of numbers of terrapins per aquatic site, habitat occupation, and reproduction success. Our investigation has revealed differences in the ecology of the red-eared slider in different parts of Eurasia. The most prominent expression of diverse signs of invasion success (higher portion of inhabited natural water bodies, higher number of individuals per water body, successful overwintering, occurrence of juvenile individuals, successful reproduction, and establishment of populations) are typical for Europe, West Asia and East Asia and tend to be restricted to coastal regions and islands. Reproduction records coincide well with the predicted potential range based on climatic requirements but records of successful wintering have a wider distribution. This invader provides an excellent and possibly unique (among animals) example of wide alien distribution, without the establishment of reproducing populations, but through the recruitment of new individuals to rising pseudopopulations due to additional releases. Therefore, alongside the potential reproduction range, a cost-effective strategy for population control must take in account the geographical area of successful wintering.

Sub–100 nm Nanoparticle Upconcentration in Flow by Dielectrophoretic Forces

This paper presents a novel microfluidic chip for upconcentration of sub–100 nm nanoparticles in a flow using electrical forces generated by a DC or AC field. Two electrode designs were optimized using COMSOL Multiphysics and tested using particles with sizes as low as 47 nm. We show how inclined electrodes with a zig-zag three-tooth configuration in a channel of 20 µm width are the ones generating the highest gradient and therefore the largest force. The design, based on AC dielectrophoresis, was shown to upconcentrate sub–100 nm particles by a factor of 11 using a flow rate of 2–25 µL/h. We present theoretical and experimental results and discuss how the chip design can easily be massively parallelized in order to increase throughput by a factor of at least 1250.

Continuous Microfluidic Production of Citrem-Phosphatidylcholine Nano-Self-Assemblies for Thymoquinone Delivery

Lamellar and non-lamellar liquid crystalline nanodispersions, including liposomes, cubosomes, and hexosomes are attractive platforms for drug delivery, bio-imaging, and related pharmaceutical applications. As compared to liposomes, there is a modest number of reports on the continuous production of cubosomes and hexosomes. Using a binary lipid mixture of citrem and soy phosphatidylcholine (SPC), we describe the continuous production of nanocarriers for delivering thymoquinone (TQ, a substance with various therapeutic potentials) by employing a commercial microfluidic hydrodynamic flow-focusing chip. In this study, nanoparticle tracking analysis (NTA) and synchrotron small-angle X-ray scattering (SAXS) were employed to characterize TQ-free and TQ-loaded citrem/SPC nanodispersions. Microfluidic synthesis led to formation of TQ-free and TQ-loaded nanoparticles with mean sizes around 115 and 124 nm, and NTA findings indicated comparable nanoparticle size distributions in these nanodispersions. Despite the attractiveness of the microfluidic chip for continuous production of citrem/SPC nano-self-assemblies, it was not efficient as comparable mean nanoparticle sizes were obtained on employing a batch (discontinuous) method based on low-energy emulsification method. SAXS results indicated the formation of a biphasic feature of swollen lamellar (Lα) phase in coexistence with an inverse bicontinuous cubic Pn3m phase in all continuously produced TQ-free and TQ-loaded nanodispersions. Further, a set of SAXS experiments were conducted on samples prepared using the batch method for gaining further insight into the effects of ethanol and TQ concentration on the structural features of citrem/SPC nano-self-assemblies. We discuss these effects and comment on the need to introduce efficient microfluidic platforms for producing nanocarriers for delivering TQ and other therapeutic agents.

Investigating the Use of Impedance Flow Cytometry for Classifying the Viability State of E. coli

Bacteria detection, counting and analysis is of great importance in several fields. When viability plays a major role in decision making, the counting of colony-forming units grown on agar plates remains the gold standard. However, because plate counts depend on the growth of the bacteria, it is a slow procedure and only works with culturable species. Impedance flow cytometry (IFC) is a promising technology for particle detection, counting and characterization. It relies on the perturbation of an electric field by particles flowing through a microfluidic channel. The perturbation is directly related to the electrical properties of the particles, and therefore provides information about their composition and structure. In this work we investigate whether IFC can be used to differentiate viable cells from inactivated cells. Our findings demonstrate that the specific viability state of the bacteria has to be considered, but that with proper characterization thresholds, IFC can be used to classify bacterial viability states. By using three different inactivation methods-ethanol, heat and autoclavation-we have been able to show that the impedance response of Escherichia coli depends on its viability state, but that the specific response depends on the inactivation method. With these findings we expect to be able to optimize IFC for more reliable bacteria detection and counting in the future.

Nanograss sensor for selective detection of Pseudomonas aeruginosa by pyocyanin identification in airway samples

Pyocyanin is a virulence factor solely produced by the pathogen Pseudomonas aeruginosa. Pyocyanin is also a redox active molecule that can be directly detected by electrochemical sensing. A nanograss (NG) based sensor for sensitive quantification of pyocyanin in sputum samples from cystic fibrosis (CF) patients is presented here. The NG sensors were custom made in a cleanroom environment by etching nanograss topography on the electrode surface followed by depositing 200 nm gold. The NG sensors were utilized for amperometric quantification of pyocyanin in spiked hypertonic saline samples, resulting in a linear calibration curve with a R² value of 0.9901 and a limit of detection of 172 nM. The NG sensors were applied in a small pilot test on five airway samples from five CF patients. The NG sensor was capable of identifying P. aeruginosa in the airway samples in 60 s without any sample pretreatment.

Electrochemical determination of bentazone using simple screen-printed carbon electrodes

Bentazone is one of the most problematic pesticides polluting groundwater resources. It is on the list of pesticides that are mandatory to analyze at water work controls. The current pesticide measuring approach includes manual water sampling and time-consuming chromatographical quantification of the bentazone content at centralized laboratories. Here, we report the use of an electrochemical approach for analytical determination of bentazone that takes 10 s. The electrochemical electrodes were manually screen printed, resulting in the low-cost fabrication of the sensors. The current response was linearly proportional to the bentazone concentration with a R² ~ 0.999. We demonstrated a sensitivity of 0.0987 μA/μM and a limit of detection of 0.034 μM, which is below the U.S. Health Advisory level. Furthermore, the sensors have proved to be reusable and stable with a drop of only 2% after 15 times reuse. The sensors have been applied to successfully quantify bentazone spiked in real groundwater and lake water. The sensing method presented here is a step towards on-site application of electrochemical detection of pesticides in water sources.

A hydrodynamic flow focusing microfluidic device for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride

Cubosomes and hexosomes are emerging platforms for drug and nutraceutical delivery applications. In addition to common high- and low-energy batch emulsification methods for the preparation of these nano-self-assemblies, it is important to introduce suitable microfluidic devices with a precision control of the flow parameters for their continuous production. Microfluidics has several advantages including cost effectiveness, short-production time, and control of the nanoparticle size and size distribution. In the present study, a hydrodynamic flow focusing polyimide microfluidic device was employed for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride (MAG-DHA), in the presence of the stabilizer Pluronic F127. The size, structural, morphological and size characterizations of the continuously produced MAG-DHA nanodispersions were investigated through an integrated approach involving synchrotron small angle X-ray scattering, dynamic light scattering, and cryogenic transmission electron microscopy. We report on a simple process for the microfluidic synthesis of hexosomes with sizes ranging from 108 to 138 nm and relatively narrow size distributions as the polydispersity indices were in the range of 0.14-0.22. At the applied total volumetric flow rates (TFRs) ranging of 50-150 μL min^-1 and flow rate ratios (FRRs) of 10-30, it was evident from SAXS findings that ethanol has only a slight effect on the lattice parameter of the internal inverse hexagonal (H₂) phase of the produced hexosomes. In addition to hexosomes, cryo-TEM observations indicated the coexistence of vesicular structures and smaller nano-objects. The formation of these nano-objects that are most likely normal micelles was also confirmed by SAXS, particularly on increasing FRR from 10 to 20 or 30 at TFR of 150 μL min^-1. Taking into account the reported positive health effects of MAG-DHA, which is a long-chain omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglyceride, in various disorders including cancer, the produced hexosomes are attractive for the delivery of ω-3 PUFAs, drugs, nutraceuticals, and their combinations.

Detection of Glyphosate in Drinking Water: A Fast and Direct Detection Method without Sample Pretreatment

Glyphosate (Gly) is one of the most problematic pesticides that repeatedly appears in drinking water. Continuous on-site detection of Gly in water supplies can provide an early warning in incidents of contamination, before the pesticide reaches the drinking water. Here, we report the first direct detection of Gly in tap water with electrochemical sensing. Gold working electrodes were used to detect the pesticide in spiked tap water without any supporting electrolyte, sample pretreatment or electrode modifications. Amperometric measurements were used to quantify Gly to a limit of detection of 2 μM, which is below the regulation limit of permitted contamination of drinking water in the United States. The quantification of Gly was linearly proportional with the measured signal. The selectivity of this method was evaluated by applying the same technique on a Gly Metabolite, AMPA, and on another pesticide, omethoate, with a chemical structure similar to Gly. The testing revealed no interfering electrochemical activity at the potential range used for Gly detection. The simple detection of Gly presented in this work may lead to direct on-site monitoring of Gly contamination at drinking water sources.

Nivolumab for adults with Hodgkin's lymphoma (a rapid review using the software RobotReviewer)

BACKGROUND

Hodgkin's lymphoma (HL) is a cancer of the lymphatic system, and involves the lymph nodes, spleen and other organs such as the liver, lung, bone or bone marrow, depending on the tumour stage. With cure rates of up to 90%, HL is one of the most curable cancers worldwide. Approximately 10% of people with HL will be refractory to initial treatment or will relapse; this is more common in people with advanced stage or bulky disease. Standard of care for these people is high-dose chemotherapy and autologous stem cell transplantation (ASCT), but only 55% of participants treated with high-dose chemotherapy and ASCT are free from treatment failure at three years, with an overall survival (OS) of about 80% at three years.Checkpoint inhibitors that target the interaction of the programmed death (PD)-1 immune checkpoint receptor, and its ligands PD-L1 and PD-L2, have shown remarkable activity in a wide range of malignancies. Nivolumab is an anti-(PD)-1 monoclonal antibody and currently approved by the US Food and Drug Administration (FDA) for the treatment of melanoma, non-small cell lung cancer, renal cell carcinoma and, since 2016, for classical Hodgkin's lymphoma (cHL) after treatment with ASCT and brentuximab vedotin.

OBJECTIVES

To assess the benefits and harms of nivolumab in adults with HL (irrespective of stage of disease).

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, International Pharmaceutical Abstracts, conference proceedings and six study registries from January 2000 to May 2018 for prospectively planned trials evaluating nivolumab.

SELECTION CRITERIA

We included prospectively planned trials evaluating nivolumab in adults with HL. We excluded trials in which less than 80% of participants had HL, unless the trial authors provided the subgroup data for these participants in the publication or after we contacted the trial authors.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed potential risk of bias. We used the software RobotReviewer to extract data and compared results with our findings. As we did not identify any randomised controlled trials (RCTs) or non-RCTs, we did not meta-analyse data.

MAIN RESULTS

Our search found 782 potentially relevant references. From these, we included three trials without a control group, with 283 participants. In addition, we identified 14 ongoing trials evaluating nivolumab, of which two are randomised. Risk of bias of the three included studies was moderate to high. All of the participants were in relapsed stage, most of them were heavily pretreated and had received at least two previous treatments, most of them had also undergone ASCT. As we did not identify any RCTs, we could not use the software RobotReviewer to assess risk of bias. The software identified correctly that one study was not an RCT and did not extract any trial data, but extracted characteristics of the other two studies (although also not RCTs) in a sufficient way.Two studies with 260 participants evaluated OS. After six months, OS was 100% in one study and median OS (the timepoint when only 50% of participants were alive) was not reached in the other trial after a median follow-up of 18 months (interquartile range (IQR) 15 to 22 months) (very low certainty evidence, due to observational trial design, heterogenous patient population in terms of pretreatments and various follow-up times (downgrading by 1 point)). In one study, one out of three cohorts reported quality of life. It was unclear whether there was an effect on quality of life as only a subset of participants filled out the follow-up questionnaire (very low certainty evidence). Three trials (283 participants) evaluated progression-free survival (PFS) (very low certainty evidence). Six-month PFS ranged between 60% and 86%, and median PFS ranged between 12 and 18 months. All three trials (283 participants) reported complete response rates, ranging from 12% to 29%, depending on inclusion criteria and participants' previous treatments (very low certainty evidence).One trial (243 participants) reported drug-related grade 3 or 4 adverse events (AEs) only after a median follow-up of 18 months (IQR 15 to 22 months); these were fatigue (23%), diarrhoea (15%), infusion reactions (14%) and rash (12%). The other two trials (40 participants) reported 23% to 52% grade 3 or 4 AEs after six months' follow-up (very low certainty evidence). Only one trial (243 participants) reported drug-related serious AEs; 2% of participants developed infusion reactions and 1% pneumonitis (very low certainty evidence).None of the studies reported treatment-related mortality.

AUTHORS' CONCLUSIONS

To date, data on OS, quality of life, PFS, response rate, or short- and long-term AEs are available from small uncontrolled trials only. The three trials included heavily pretreated participants, which had previously undergone regimens of BV or ASCT. For these participants, median OS was not reached after follow-up times of at least 16 months (more than 50% of participants with a limited life expectancy were alive at this timepoint). Only one cohort out of three only reported quality of life, with limited follow-up data so that meaningful conclusions were not possible. Serious adverse events occurred rarely. Currently, data are too sparse to make a clear statement on nivolumab for people with relapsed or refractory HL except for heavily pretreated people, which had previously undergone regimens of BV or ASCT. When interpreting these results, it is important to consider that proper RCTs should confirm these findings.As there are 14 ongoing trials evaluating nivolumab, of which two are RCTs, it is possible that an update of this review will be published in the near future and that this update will show different results to those reported here.

Direct Detection of Candida albicans with a Membrane Based Electrochemical Impedance Spectroscopy Sensor

Candidemia and invasive candidiasis is a cause of high mortality and morbidity rates among hospitalized patients worldwide. The occurrence of the infections increases due to the complexity of the patients and overuse of the antifungal therapy. The current Candida detection method includes blood culturing which is a lengthy procedure and thus delays the administration of the antifungal therapy. Even though the results are available after 48 h it is still the gold standard in pathogen detection in a hospital setting. In this work we present an electrochemical impedance sensor that is capable of detecting Candida albicans yeast. The yeast cells are captured on electrodes specifically functionalized with anti-Candida antibodies and detection is achieved by electrochemical impedance spectroscopy. The sensor allows for detection of the yeast cells at clinically relevant concentrations in less than 1 h.

Paper-based sensors for rapid detection of virulence factor produced by Pseudomonas aeruginosa

Pyocyanin is a toxin produced by Pseudomonas aeruginosa. Here we describe a novel paper-based electrochemical sensor for pyocyanin detection, manufactured with a simple and inexpensive approach based on electrode printing on paper. The resulting sensors constitute an effective electrochemical method to quantify pyocyanin in bacterial cultures without the conventional time consuming pretreatment of the samples. The electrochemical properties of the paper-based sensors were evaluated by ferri/ferrocyanide as a redox mediator, and showed reliable sensing performance. The paper-based sensors readily allow for the determination of pyocyanin in bacterial cultures with high reproducibility, achieving a limit of detection of 95 nM and a sensitivity of 4.30 μA/μM in standard culture media. Compared to the similar commercial ceramic based sensors, it is a 2.3-fold enhanced performance. The simple in-house fabrication of sensors for pyocyanin quantification allows researchers to understand in vitro adaptation of P. aeruginosa infections via rapid screenings of bacterial cultures that otherwise are expensive and time-consuming.

Novel culturing platform for brain slices and neuronal cells

In this paper we demonstrate a novel culturing system for brain slices and neuronal cells, which can control the concentration of nutrients and the waste removal from the culture by adjusting the fluid flow within the device. The entire system can be placed in an incubator. The system has been tested successfully with brain slices and PC12 cells. The culture substrate can be modified using metal electrodes and/or nanostructures for conducting electrical measurements while culturing and for better mimicking the in vivo conditions.

Novel membrane-based electrochemical sensor for real-time bio-applications

This article presents a novel membrane-based sensor for real-time electrochemical investigations of cellular- or tissue cultures. The membrane sensor enables recording of electrical signals from a cell culture without any signal dilution, thus avoiding loss of sensitivity. Moreover, the porosity of the membrane provides optimal culturing conditions similar to existing culturing techniques allowing more efficient nutrient uptake and molecule release. The patterned sensor electrodes were fabricated on a porous membrane by electron-beam evaporation. The electrochemical performance of the membrane electrodes was characterized by cyclic voltammetry and chronoamperometry, and the detection of synthetic dopamine was demonstrated down to a concentration of 3.1 pM. Furthermore, to present the membrane-sensor functionality the dopamine release from cultured PC12 cells was successfully measured. The PC12 cells culturing experiments showed that the membrane-sensor was suitable as a cell culturing substrate for bio-applications. Real-time measurements of dopamine exocytosis in cell cultures were performed, where the transmitter release was recorded at the point of release. The developed membrane-sensor provides a new functionality to the standard culturing methods, enabling sensitive continuous in vitro monitoring and closely mimicking the in vivo conditions.

Cdt1 Interactions in the Licensing Process: A Model for Dynamic Spatio-temporal Control of Licensing

Within each cell cycle, a cell must ensure that the processes of selection of replication origins (licensing) and initiation of DNA replication are well coordinated to prevent reinitiation of DNA replication from the same DNA segment during the same cell cycle. This is achieved by restricting the licensing process to G1 phase when the prereplicative complexes (preRCs) are assembled onto the origin DNA, while DNA replication is initiated only during S phase when de novo preRC assembly is blocked. Cdt1 is an important member of the preRC complex and its tight regulation through ubiquitin-dependent proteolysis and binding to its inhibitor Geminin ensure that Cdt1 will only be present in G1 phase, preventing relicensing of replication origins. We have recently reported that Cdt1 associates with chromatin in a dynamic way and recruits its inhibitor Geminin onto chromatin in vivo. Here we discuss how these dynamic Cdt1-chromatin interactions and the local recruitment of Geminin onto origins of replication by Cdt1 may provide a tight control of the licensing process in time and in space.

A compact microelectrode array chip with multiple measuring sites for electrochemical applications

In this paper we demonstrate the fabrication and electrochemical characterization of a microchip with 12 identical but individually addressable electrochemical measuring sites, each consisting of a set of interdigitated electrodes acting as a working electrode as well as two circular electrodes functioning as a counter and reference electrode in close proximity. The electrodes are made of gold on a silicon oxide substrate and are passivated by a silicon nitride membrane. A method for avoiding the creation of high edges at the electrodes (known as lift-off ears) is presented. The microchip design is highly symmetric to accommodate easy electronic integration and provides space for microfluidic inlets and outlets for integrated custom-made microfluidic systems on top.

A compact multifunctional microfluidic platform for exploring cellular dynamics in real-time using electrochemical detection

Dopamine detection from PC12 cell populations and monitoring of yeast redox metabolism demonstrate the multifunctionality of the compact microfluidic cell culture and electrochemical analysis platform with in-built fluid handling and detection unit.

Doped overoxidized polypyrrole microelectrodes as sensors for the detection of dopamine released from cell populations

A surface modification of interdigitated gold microelectrodes (IDEs) with a doped polypyrrole (PPy) film for detection of dopamine released from populations of differentiated PC12 cells is presented. A thin PPy layer was potentiostatically electropolymerized from an aqueous pyrrole solution onto electrode surfaces. The conducting polymer film was doped during electropolymerization by introducing counter-ions in the monomer solution. Several counter-ions were tested and the resulting electrode modifications were characterized electrochemically to find the optimal dopant that increases sensitivity in dopamine detection. Overoxidation of the PPy films was shown to contribute to a significant enhancement in sensitivity to dopamine. The changes caused by overoxidation in the electrochemical behavior and electrode morphology were investigated using cyclic voltammetry and SEM as well as AFM, respectively. The optimal dopant for dopamine detection was found to be polystyrene sulfonate anion (PSS(-)). Rat pheochromocytoma (PC12) cells, a suitable model to study exocytotic dopamine release, were differentiated on IDEs functionalized with an overoxidized PSS(-)-doped PPy film. The modified electrodes were used to amperometrically detect dopamine released by populations of cells upon triggering cellular exocytosis with an elevated K(+) concentration. A comparison between the generated current on bare gold electrodes and gold electrodes modified with overoxidized doped PPy illustrates the clear advantage of the modification, yielding 2.6-fold signal amplification. The results also illustrate how to use cell population based dopamine exocytosis measurements to obtain biologically significant information that can be relevant in, for instance, the study of neural stem cell differentiation into dopaminergic neurons.

Cell cycle-dependent subcellular translocation of the human DNA licensing inhibitor geminin

Once per cell cycle replication is crucial for maintaining genome integrity. Geminin interacts with the licensing factor Cdt1 to prevent untimely replication and is controlled by APC/C-dependent cell cycle specific proteolysis during mitosis and in G1. We show here that human geminin, when expressed in human cells in culture under a constitutive promoter, is excluded from the nucleus during part of the G1 phase and at the transition from G0 to G1. The N-terminal 30 amino acids of geminin, which contain its destruction box, are essential for nuclear exclusion. In addition, 30 amino acids within the central domain of geminin are required for both nuclear exclusion and nuclear accumulation. Cdt1 overexpression targets geminin to the nucleus, while reducing Cdt1 levels by RNAi leads to the appearance of endogenous geminin in the cytoplasm. Our data propose a novel means of regulating the balance of Cdt1/geminin in human cells, at the level of the subcellular localization of geminin.

Combined cell culture-biosensing platform using vertically aligned patterned peptide nanofibers for cellular studies

This Article presents the development of a combined cell culture-biosensing platform using vertically aligned self-assembled peptide nanofibers. Peptide nanofibers were patterned on a microchip containing gold microelectrodes to provide the cells with a 3D environment enabling them to grow and proliferate. Gold microelectrodes were functionalized with conductive polymers for the electrochemical detection of dopamine released from PC12 cells. The combined cell culture-biosensing platform assured a close proximity of the release site, the cells and the active surface of the sensor, thereby rendering it possible to avoid a loss of sensitivity because of the diffusion of the sample. The obtained results showed that the peptide nanofibers were suitable as a cell culturing substrate for PC12 cells. The peptide nanofibers could be employed as an alternative biological material to increase the adherence properties of PC12 cells. Dopamine was amperometrically detected at a value of 168 fmole.

Multichannel bipotentiostat integrated with a microfluidic platform for electrochemical real-time monitoring of cell cultures

An electrochemical detection system specifically designed for multi-parameter real-time monitoring of stem cell culturing/differentiation in a microfluidic system is presented. It is composed of a very compact 24-channel electronic board, compatible with arrays of microelectrodes and coupled to a microfluidic cell culture system. A versatile data acquisition software enables performing amperometry, cyclic voltammetry and impedance spectroscopy in each of the 12 independent chambers over a 100 kHz bandwidth with current resolution down to 5 pA for 100 ms measuring time. The design of the platform, its realization and experimental characterization are reported, with emphasis on the analysis of impact of input capacitance (i.e., microelectrode size) and microfluidic pump operation on current noise. Programmable sequences of successive injections of analytes (ferricyanide and dopamine) and rinsing buffer solution as well as the impedimetric continuous tracking for seven days of the proliferation of a colony of PC12 cells are successfully demonstrated.

Microfluidic device to study cell transmigration under physiological shear stress conditions

The development of new drug therapies relies on studies of cell transmigration in in vitro systems. Migration has traditionally been studied using two methods, the Boyden chamber and a shear flow chamber assay. Though, commonly applied in cell transmigration studies, they are far from imitating a natural migration process. Here we describe a novel in vitro cell transmigration microfluidic assay, which mimicks physiological shear flow conditions in blood vessels. The device was designed to incorporate the principles of both the Boyden chamber and the shear flow chamber assay, i.e. migration through the membrane under flow conditions. The 3D environment of migrating cells is imitated by injecting cell adhesion proteins to coat the membrane in the device. We tested the developed device with Jurkat cells migration towards medium supplemented with serum, and with chemokine induced lymphocytes migration. The applied continuous flow of cell suspension and chemoattractant ensures that the concentration gradient is maintained in time and space. The cell adhesion proteins used to enhance cell migration in the device were fibronectin and VCAM-1. We successfully observed a multistep transmigration process by means of the developed microfluidic migration assay. The presented device is inexpensive, easy to fabricate and disposable, having a potential to be applied in basic research as well as in the drug development process.

Electrostatic force microscopy of self-assembled peptide structures

In this report electrostatic force microscopy (EFM) is used to study different peptide self-assembled structures such as tubes and particles. It is shown that not only geometrical information can be obtained using EFM, but also information about the composition of different structures. In particular we use EFM to investigate the structures of diphenylalanine peptide tubes, particles, and CSGAITIG peptide particles placed on pre-fabricated SiO(2) surfaces with a backgate. We show that the cavity in the peptide tubes could be due to the presence of water residues. Additionally we show that self-assembled amyloid peptides form spherical solid structures containing the same self-assembled peptide in its interior. In both cases transmission electron microscopy is used to verify these structures. Further, the limitations of the EFM technique are discussed, especially when the observed structures become small compared with the radius of the AFM tip used. Finally, an agreement between the detected signal and the structure of the hollow peptide tubes is demonstrated.

Idas, a novel phylogenetically conserved geminin-related protein, binds to geminin and is required for cell cycle progression

Development and homeostasis of multicellular organisms relies on an intricate balance between cell proliferation and differentiation. Geminin regulates the cell cycle by directly binding and inhibiting the DNA replication licensing factor Cdt1. Geminin also interacts with transcriptional regulators of differentiation and chromatin remodelling factors, and its balanced interactions are implicated in proliferation-differentiation decisions during development. Here, we describe Idas (Idas being a cousin of the Gemini in Ancient Greek Mythology), a previously uncharacterised coiled-coil protein related to Geminin. We show that human Idas localizes to the nucleus, forms a complex with Geminin both in cells and in vitro through coiled-coil mediated interactions, and can change Geminin subcellular localization. Idas does not associate with Cdt1 and prevents Geminin from binding to Cdt1 in vitro. Idas depletion from cells affects cell cycle progression; cells accumulate in S phase and are unable to efficiently progress to mitosis. Idas protein levels decrease in anaphase, whereas its overexpression causes mitotic defects. During development, we show that Idas exhibits high level expression in the choroid plexus and the cortical hem of the mouse telencephalon. Our data highlight Idas as a novel Geminin binding partner, implicated in cell cycle progression, and a putative regulator of proliferation-differentiation decisions during development.

Three dimensional electrochemical system for neurobiological studies

In this work we report a novel three dimensional electrode array for electrochemical measurements in neuronal studies. The main advantage of working with these out-of-plane structures is the enhanced sensitivity of the system in terms of measuring electrochemical changes in the environment of a cell culture in real time. In addition, the system is devised to offer a compact solution that helps to obtain a homogeneous distribution of current density among the active electrodes.

Qualitative mapping of structurally different dipeptide nanotubes

Biological self-assembled structures are receiving increasing focus within micro- and nanotechnology, for example, as sensing devices, due to the fact that they are cheap to produce and easy to functionalize. Therefore, methods for the characterization of these structures are much needed. In this paper, electrostatic force microscopy (EFM) was used to distinguish between hollow nanotubes formed by self-assembly by a simple aromatic dipeptide, L-phenylalanine, silver-filled peptide-based nanotubes, and silver wires placed on prefabricated SiO2 surfaces with a backgate. The investigation shows that it is possible to distinguish between these three types of structures using this method. Further, an agreement between the detected signal and the structure of the hollow peptide was demonstrated; however only qualitative agreement with the mathematical expressing of the tubes is shown.

Investigation of parameters controlling the dielectrophoretic assembly of carbon nanotubes on microelectrodes

Networks of single-walled carbon nanotubes were assembled onto microelectrodes by dielectrophoresis. The dependence of the obtained networks on several assembly parameters such as bias voltage, field application time, frequency, electrode geometry and the nanotube solvent were investigated both structurally and electrically. Reproducible differences in morphological and electrical properties were observed for the parameters investigated. Application of a bias voltage above 10 V for more than 30 seconds with nanotubes in an SDS solution, resulted in dense networks with a relatively low resistance in the 10 komega regime. On the other hand, individual nanotubes and bundles were assembled with lower voltages applied for less than 10 seconds and with other nanotubes solutions. The experimental results were combined with theoretical calculations in order to find a geometry and voltage independent threshold field for the successful assembly of nanotubes between electrodes using dielectrophoresis.

Eastern Mediterranean chameleons (Chamaeleo chamaeleon, Ch. africanus) are distinct

Abstract

Based on mitochondrial 16S rRNA sequences, we suggest that the founder individuals of the introduced Greek population of Chamaeleo africanus originated in the Nile Delta region of Egypt. In Ch. chamaeleon, we discovered in the eastern Mediterranean new 16S rRNA haplotypes, being highly distinct from previously published western Mediterranean haplotypes. Eastern Mediterranean haplotypes were found in samples from northern Syria, Cyprus, Crete, Samos, Malta and Tunisia. The occurrence of an eastern Mediterranean haplotype in Tunisia and of distinct haplotypes in Morocco could argue for a phylogeographic break in northwestern Africa.

Cdt1 associates dynamically with chromatin throughout G1 and recruits Geminin onto chromatin

To maintain genome integrity, eukaryotic cells initiate DNA replication once per cell cycle after assembling prereplicative complexes (preRCs) on chromatin at the end of mitosis and during G1. In S phase, preRCs are disassembled, precluding initiation of another round of replication. Cdt1 is a key member of the preRC and its correct regulation via proteolysis and by its inhibitor Geminin is essential to prevent premature re-replication. Using quantitative fluorescence microscopy, we study the interactions of Cdt1 with chromatin and Geminin in living cells. We find that Cdt1 exhibits dynamic interactions with chromatin throughout G1 phase and that the protein domains responsible for chromatin and Geminin interactions are separable. Contrary to existing in vitro data, we show that Cdt1 simultaneously binds Geminin and chromatin in vivo, thereby recruiting Geminin onto chromatin. We propose that dynamic Cdt1-chromatin associations and the recruitment of Geminin to chromatin provide spatio-temporal control of the licensing process.

Single- and multiwalled carbon nanotube networks and bundles assembled on microelectrodes

Dielectrophoresis is a convenient and flexible method for manipulating carbon nanotubes by the use of alternating electric fields. The method can be used for self-assembly of nanotubes on a set of microelectrodes. This paper shows bundles and nets of single- and multiwalled carbon nanotubes assembled between microelectrodes of various geometries as well IV curves recorded on the assembled nanosystems. The nets of multiwalled carbon nanotubes are suspended, while the single-walled nanotubes are lying on a surface. Carbon nanotube nets exhibit a large current-carrying capacity up to almost 4 mA with resistance of 1 to 4 kΩ, indicating that reliable electrical contacts can be formed using dielectrophoresis. This conclusion is further strengthened by the fact that the nanotubes tend to fail in intermediate regions far away from the electrodes, when subjected to currents above the maximal current capacity.

Ecology and conservation of the Milos viper, Macrovipera schweizeri (Werner, 1935)

Abstract

The Milos viper (Macrovipera schweizeri) is nocturnal from early summer until mid-September. The typical habitat was maquis terrain with small and large bushes on gravel or rocky ground. Telemetric studies showed that cryptic basking behaviour was used during 23.5% of the localisations, and a preference for large bushes (77.7%). The mean distance moved between two succeeding days was 28.5 m (with s_x, of 47.9), and in general, the male home range covered an area of 10 to 20 ha, while the female home range was smaller. Hibernacula were south facing and situated in the middle of the home ranges. Population density was 50 adult vipers per km2 in the optimal habitats. The total population for western Milos was estimated to be around 2,500 adult vipers during the study period (1993-98). The present total population on Milos seems to be below 3,000 adult animals. The species has been isolated since the Pliocene, and adapted to a diet of passerine birds. A pattern of twice-a-year foraging during spring and autumn bird migrations was highlighted. During spring, the vipers tend to be concentrated around water pools; in the dry autumn nights they climb up trees for resting birds. In years with a cold spring or autumn, critical situations may occur with starvation, resulting in cyclic population patterns. Mid-May is the mating period. The female reproductive cycle is biennial. The sex ratio is nearly equal. Around 600 specimens reach adulthood and participate in the reproductive activities each year. Mining and fires destroy habitat. The yearly estimated removal by man and road killing of vipers is up to 500-600 adult specimens. Thus, the input and out-take of adult specimens is of the same magnitude, and equal to a yearly 25% turnover. This indicates a very delicate balance, and even a small change that increases the removed number can lead towards a rapid extinction. A conservation program is urgently needed and should include the establishment of protected areas, the closing of roads for night-time driving, and prohibition of increased mining activities.