抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

The manipulation of fluids in channels with dimensions of tens of micrometres--microfluidics--has emerged as a distinct new field. Microfluidics has the potential to influence subject areas from chemical synthesis and biological analysis to optics and information technology. But the field is still at an early stage of development. Even as the basic science and technological demonstrations develop, other problems must be addressed: choosing and focusing on initial applications, and developing strategies to complete the cycle of development, including commercialization. The solutions to these problems will require imagination and ingenuity.

The origins and the future of microfluidics

基礎講座 電気泳動(Electrophoresis)

This article describes the process of formation of droplets and bubbles in microfluidic T-junction geometries. At low capillary numbers break-up is not dominated by shear stresses: experimental results support the assertion that the dominant contribution to the dynamics of break-up arises from the pressure drop across the emerging droplet or bubble. This pressure drop results from the high resistance to flow of the continuous (carrier) fluid in the thin films that separate the droplet from the walls of the microchannel when the droplet fills almost the entire cross-section of the channel. A simple scaling relation, based on this assertion, predicts the size of droplets and bubbles produced in the T-junctions over a range of rates of flow of the two immiscible phases, the viscosity of the continuous phase, the interfacial tension, and the geometrical dimensions of the device.

http://ichf.pong.pl/i/publications/29.pdf

Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up.

Hydrogels are hydrophilic polymer-based materials with high water content and physical characteristics that resemble the native extracellular matrix. Because of their remarkable properties, hydrogel systems are used for a wide range of biomedical applications, such as three-dimensional (3D) matrices for tissue engineering, drug-delivery vehicles, composite biomaterials, and as injectable fillers in minimally invasive surgeries. In addition, the rational design of hydrogels with controlled physical and biological properties can be used to modulate cellular functionality and tissue morphogenesis. Here, the development of advanced hydrogels with tunable physiochemical properties is highlighted, with particular emphasis on elastomeric, light-sensitive, composite, and shape-memory hydrogels. Emerging technologies developed over the past decade to control hydrogel architecture are also discussed and a number of potential applications and challenges in the utilization of hydrogels in regenerative medicine are reviewed. It is anticipated that the continued development of sophisticated hydrogels will result in clinical applications that will improve patient care and quality of life.

/pdf/25th-anniversary-article-rational-design-and-applications-of-4vstyfvewj.pdf

25th Anniversary Article: Rational Design and Applications of Hydrogels in Regenerative Medicine

The following article is based on the Symposium X presentation given by David A. Weitz (Harvard University) on April 11, 2007, at the Materials Research Society Spring Meeting in San Francisco. The article describes how simple microfluidic devices can be used to control fluid flow and produce a variety of new materials. Based on the concepts of coaxial flow and hydrodynamically focused flow, used alone or in various combinations, the devices can produce precisely controlled double emulsions (droplets within droplets) and even triple emulsions (double emulsions suspended in a third droplet). These structures, which can be created in a single microfluidic device, have various applications such as encapsulants for drugs, cosmetics, or food additives.

Dripping, Jetting, Drops, and Wetting: The Magic of Microfluidics

A microfluidic device denoted the Phase Chip has been designed to measure and manipulate the phase diagram of multicomponent fluid mixtures. The Phase Chip exploits the permeation of water through poly(dimethylsiloxane) (PDMS) in order to controllably vary the concentration of solutes in aqueous nanoliter volume microdrops stored in wells. The permeation of water in the Phase Chip is modeled using the diffusion equation, and good agreement between experiment and theory is obtained. The Phase Chip operates by first creating drops of the water/solute mixture whose composition varies sequentially. Next, drops are transported down channels and guided into storage wells using surface tension forces. Finally, the solute concentration of each stored drop is simultaneously varied and measured. Two applications of the Phase Chip are presented. First, the phase diagram of a polymer/salt mixture is measured on-chip and validated off-chip, and second, protein crystallization rates are enhanced through the manipulation of the kinetics of nucleation and growth.

/pdf/control-and-measurement-of-the-phase-behavior-of-aqueous-2n577ojuqc.pdf

Control and measurement of the phase behavior of aqueous solutions using microfluidics

The present invention relates generally to microfluidic structures, and more specifically, to microfluidic structures and methods including microreactors for manipulating fluids and reactions. In some embodiments, structures and methods for manipulating many (e.g., 1000) fluid samples, i.e., in the form of droplets, are described. Processes such as diffusion, evaporation, dilution, and precipitation can be controlled in each fluid sample. These methods also enable conditions within the fluid samples (e.g., concentration) to be controlled. Manipulation of fluid samples can be useful for a variety of applications, including testing for reaction conditions, e.g., in crystallization, chemical, and biological assays.

Microfluidic manipulation of fluids and reactions

A high-throughput, low-volume microfluidic device has been designed to decouple the physical processes of protein crystal nucleation and growth. This device, called the Phase Chip, is constructed o...

/pdf/using-microfluidics-to-decouple-nucleation-and-growth-of-53hfn0kold.pdf

Using Microfluidics to Decouple Nucleation and Growth of Protein Crystals.

We report a fabrication method for producing interference-based electro-optic phase gratings that switch between diffracting and transparent states. The phase grating consists of a hexagonal-close-packed array of monodisperse emulsion drops of nematic liquid crystal, embedded in a polymer matrix. Monodisperse droplet size allows for fast switching at low electric fields.

Darren Roy Link

Papers

Dripping, Jetting, Drops, and Wetting: The Magic of Microfluidics

Control and measurement of the phase behavior of aqueous solutions using microfluidics

Microfluidic manipulation of fluids and reactions

Using Microfluidics to Decouple Nucleation and Growth of Protein Crystals.

Phase switching of ordered arrays of liquid crystal emulsions