1,721,002 research outputs found
Novel technologies for the formation of 2-D and 3-D droplet interface bilayer networks
No full textDroplet Interface Bilayer (DIB) networks have vast potential in the field of membrane biophysics, synthetic biology, and functional bio-electronics. However a technological bottleneck exists in network fabrication: existing methods are limited in terms of their automation, throughput, versatility, and ability to form well defined 3-D networks. We have developed a series of novel and low-cost methodologies which address these limitations. The first involves building DIB networks around the contours of a microfluidic chip. The second uses flow rate and droplet size control to influence droplet packing geometries within a microfluidic chamber. The latter method enables controlled formation of various 3-D network arrays consisting of thousands of interconnected symmetric and asymmetric lipid bilayers for the first time. Both approaches allow individual droplet position and composition to be controlled, paving the way for complex on-chip functional network synthesis.<br/
Dynamic control of compartmentalisation in artificial cell models
No full textIn bottom-up synthetic biology, compartmentalisation of bioactive materials within artificial cells is used to mimic the ways biological cells segregate and manage their cellular activity and/or communicate with other cells. In phospholipid-based artificial cell models, compartmentalisation of biomolecules is achieved by encapsulating them into small nano-sized vesicles stabilised by a unilamellar lipid bilayer. These compartments are then encapsulated into micro-scaled unilamellar vesicles – bioreaction-hosting artificial cells. Although this artificial compartmentalisation hierarchy resembles a biologically ubiquitous one, in natural cells compartmentalisation is a dynamic process as organelles, membrane-bound cavities hosting biochemical reactions, change shape, size, and location within the cell. In some instances, membrane-less organelles form in response to external triggers, helping the biological cells combat cellular stress. These examples show how important dynamic compartmentalisation is to maintain optimal cellular activities.
In phospholipid-based systems created to mimic cellular processes, compartmentalisation remains static. Organelle mimics diffuse throughout the hosting giant vesicle lumen without control over their spatial organisation. This lack of control over artificial cell compartmentalisation limits the researcher’s ability to create more life-like cells. Strategies for gaining control over dynamic cell compartmentalisation could potentially enable further functionalisation of artificial cells and therefore their application potential in constructing sophisticated micromachines such as nested vesicle microreactors and targeted drug delivery vehicles. In this thesis we created a suite of compartmentalised architectures with dynamic features. We have explored electrostatic interactions between oppositely charged phospholipid vesicles to create hierarchical artificial cells with defined sub-compartment spatial organisations that can be controlled using chemical and mechanical external stimuli.Open Acces
Development of stimuli-responsive vesicles as distributed artificial organelles
No full textIn recent years there has been an increasing interest in coupling artificial and living cells to expand the capabilities of engineered living organisms in biotechnology and biomedicine. The incorporation of abiotic artificial cells, constructed from the bottom-up and designed for specific purposes, enables the integration of synthetic components that confer novel functionalities into hybrid artificial-living systems.
To date, the communication between both artificial and living modules of the hybrid systems relies entirely on chemical cues. However, these cannot be externally controlled, thus hindering their potential development in therapeutic or biosensing applications.
This thesis details the design and assembly of stimuli-responsive artificial cells that enable an external user to control the activation of protein expression in bacterial cells on demand. By developing a light-responsive and a thermo-responsive lipid formulation, spatiotemporal control over living cells has been gained.
Here, vesicle-based artificial cells are loaded with a signalling molecule that is released with a light or temperature trigger and induces the expression of fluorescent proteins in bacteria. The experimental conditions have been optimised to enable ex-situ and in-situ activation of the bacterial cells, hence mimicking both endocrine and paracrine signalling conditions.
These stimuli-responsive artificial cells constitute distributed “artificial organelles”, which are not encapsulated within the living cells but endow bacteria with novel responsiveness to physical stimuli. This distributed approach converts the artificial cells into the central design units - hijacking the artificial cells enables the bacteria to gain novel functionalities, like light or temperature sensitivity, without undergoing genetic engineering. This constitutes a novel realisation in synthetic biology which could be extended to other functionalities and stimuli. Moreover, further developments could enable more complex processes, such as multistep reactions or sensing-acting tasks, to be completed thanks to multimodular hybrid systems with each module engineered to perform specific processes.Open Acces
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Present and future of synthetic cell development
No full textScientists are captivated by the prospect of creating a fully synthetic cell, offering the potential to revolutionize biology, medicine and biotechnology. In this Viewpoint, a panel of experts discusses the definitions of a synthetic cell and highlights current achievements, challenges and future opportunities of building such systems.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.BN/Marileen Dogterom La
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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