Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

This review provides an overview of major microengineering emulsification techniques for production of monodispersed droplets. The main emphasis has been put on membrane emulsification using Shirasu Porous Glass and microsieve membrane, microchannel emulsification using grooved-type and straight-through microchannel plates, microfluidic junctions and flow focusing microfluidic devices. Microfabrication methods for production of planar and 3D poly(dimethylsiloxane) devices, glass capillary microfluidic devices and single-crystal silicon microchannel array devices have been described including soft lithography, glass capillary pulling and microforging, hot embossing, anisotropic wet etching and deep reactive ion etching. In addition, fabrication methods for SPG and microseive membranes have been outlined, such as spinodal decomposition, reactive ion etching and ultraviolet LIGA (Lithography, Electroplating, and Moulding) process. The most widespread application of micromachined emulsification devices is in the synthesis of monodispersed particles and vesicles, such as polymeric particles, microgels, solid lipid particles, Janus particles, and functional vesicles (liposomes, polymersomes and colloidosomes). Glass capillary microfluidic devices are very suitable for production of core/shell drops of controllable shell thickness and multiple emulsions containing a controlled number of inner droplets and/or inner droplets of two or more distinct phases. Microchannel emulsification is a very promising technique for production of monodispersed droplets with droplet throughputs of up to 100 l h−1

Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

This paper deals with the political nature of mafias that protect drug trafficking from a broadly mentioned but poorly studied aspect in the same concept of mafia, namely, the articulation of interests of diverse social groups within their protection offer. Both types of mafias, the ones that enjoy social control and the ones that do not enjoy major social interaction, aims to impose decisions favorable to their interests. The big difference is that decisions of the former ones tend to consider the social structure transformed by drug trafficking. Any attempt to repress these mafias means now an attack to the structural interests of diverse social groups. A specific case is used to illustrate this political approach on mafia: the war of Pablo Escobar against the Colombian state.Este artículo es una aproximación al carácter político de las mafias que protegen el tráfico de drogas desde una perspectiva mencionada pero poco tratada dentro del concepto mismo de mafia: la articulación de intereses de amplios grupos sociales dentro de su oferta de protección. Tanto las mafias de la droga que gozan de dominación social como las que no tienen mayor interacción social toman decisiones dirigidas a la imposición de sus intereses. La gran diferencia está en que las decisiones de las primeras tienden a involucrar la estructura social que ha sido transformada por el narcotráfico. Cualquier intento por reprimir a las mafias involucra ahora un ataque a los intereses estructurales de amplios sectores sociales. Un caso concreto servirá para ilustrar esta lectura política del narcotráfico: la guerra de Pablo Escobar contra el estado

Capturing, Analyzing and Collecting Adherent Cells Using Microarray Technologies

Effective separation of a particular cell of interest from a heterogeneous cell population is crucial to many areas of biomedical research including microscopy, clinical diagnostics and stem cell studies. Examples of such studies include the analysis of single cells, isolation of transfected cells and cell transformation studies. Biological technologies can have skewed results if cells outside of the type of interest are present. Additionally, in many instances the targeted cells are of low abundance with respect to the heterogeneous population. For these reasons, it is important to have a technique capable of identifying the desired cells, separating these cells from unwanted cells and collecting the marked cells for further analysis. Two biotools, referred to as micropallets and microrafts, have recently been introduced for sorting adherent cells. These devices comprise arrays of microelements weakly attached to a substrate. Following culture of adherent cells on the elements, individual microstructures are selectively detached from the array while still carrying the cells. These technologies have shown success in sorting single cells from small heterogeneous cell populations with high post sorting viabilities. However, previous device designs employed gravity-based collection methods and small microelement arrays which substantially reduced the collection yields, purities and sample sizes. In this dissertation new approaches are described for capturing, examining and isolating individual cells by micropallet and microraft technologies. Initially a new approach was developed to isolate released microstructures from the array employing magnetism. Microstructures were embedded with uniformly dispersed magnetic nanoparticles which allowed collection by an external magnet immediately following release. Application of a magnetic field permitted microstructure collection with high yield, precision and purity. This improved collection efficiency enabled isolation of very rare cell types. Large arrays constituting over 106 micropallets were developed along with imaging analysis software to identify and sort low abundance target cells. This system was employed to isolate breast cancer stem cells from a heterogeneous cell population and circulating tumor cells directly from peripheral blood. Additionally, an array-based cell colony replication strategy was established which allowed highly efficient colony splitting and sampling.Doctor of Philosoph