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

Cells are inherently sensitive to local mesoscale, microscale, and nanoscale patterns of chemistry and topography. We review current approaches to control cell behavior through the nanoscale engineering of materials surfaces. Far-reaching implications are emerging for applications including medical implants, cell supports, and materials that can be used as instructive three-dimensional environments for tissue regeneration.

https://science.sciencemag.org/content/sci/310/5751/1135.full.pdf

Exploring and engineering the cell surface interface.

Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and at low costs. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. This Review covers the basic principles of nanoimprinting, with an emphasis on the requirements on materials for the imprinting mold, surface properties, and resist materials for successful and reliable nanostructure replication.

/pdf/nanoimprint-lithography-methods-and-material-requirements-csc83swyi1.pdf

Nanoimprint Lithography: Methods and Material Requirements**

To investigate how substrate properties influence stem-cell fate, we cultured single human epidermal stem cells on polydimethylsiloxane (PDMS) and polyacrylamide (PAAm) hydrogel surfaces, 0.1 kPa-2.3 MPa in stiffness, with a covalently attached collagen coating. Cell spreading and differentiation were unaffected by polydimethylsiloxane stiffness. However, cells on polyacrylamide of low elastic modulus (0.5 kPa) could not form stable focal adhesions and differentiated as a result of decreased activation of the extracellular-signal-related kinase (ERK)/mitogen-activated protein kinase (MAPK) signalling pathway. The differentiation of human mesenchymal stem cells was also unaffected by PDMS stiffness but regulated by the elastic modulus of PAAm. Dextran penetration measurements indicated that polyacrylamide substrates of low elastic modulus were more porous than stiff substrates, suggesting that the collagen anchoring points would be further apart. We then changed collagen crosslink concentration and used hydrogel-nanoparticle substrates to vary anchoring distance at constant substrate stiffness. Lower collagen anchoring density resulted in increased differentiation. We conclude that stem cells exert a mechanical force on collagen fibres and gauge the feedback to make cell-fate decisions.

Extracellular-matrix tethering regulates stem-cell fate

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

https://sites.bu.edu/chenlab/files/2014/01/46_YimBiomaterials05.pdf

Nanopattern-induced changes in morphology and motility of smooth muscle cells.

Of all oxides, lithium niobate (LiNbO3) is the gold standard electro-optical material in fiber-optic transmission systems. Modulators based on diffused waveguides in bulk LiNbO3 substrates are, however, relatively large. In contrast, ring modulators based on silicon-on-insulator are of interest for chip-scale electro-optical modulation, but unstrained crystalline silicon does not exhibit a linear electro-optic effect, so modulation is based on alternative mechanisms such as the plasma dispersion effect. Here, we present a hybrid silicon and LiNbO3 electro-optical ring modulator operating at gigahertz frequencies. The modulator consists of a 15 μm radius silicon microring and an ion-sliced LiNbO3 thin film bonded together via benzocyclobutene. Fabricated devices operating in the TE optical mode exhibit an optical loaded quality factor of 14,000 and a resonance tuning of 3.3  pm/V. The small-signal electrical-to-optical 3 dB bandwidth is measured to be 5 GHz. Digital modulation with an extinction ratio greater than 3 dB is demonstrated up to 9  Gb/s. High-speed and low-tuning-power chip-scale modulators that exploit the high-index contrast of silicon with the second-order susceptibility of LiNbO3 are envisioned.

Hybrid silicon and lithium niobate electro-optical ring modulator

We design and investigate plasmon waveguides based on linear arrays of Au nanorings in an SiO2 host for use in an optical communication band (lambda ~ 1550 nm). Nanoring particles have better tunability and can achieve more laterally compact waveguides, compared to their solid counterparts, such as nanospheres and nanodisks. Three-dimensional simulations employing the finite-difference time-domain algorithm are used to determine the set of geometrical parameters attaining localized surface plasmon resonance at 1550 nm. It is found out that, in the SiO2 host, Au nanorings attain LSPR at 1550 nm with a 175-nm inner diameter, a 35-nm height, and a 30-nm thickness. It is shown that linear chains of Au nanorings can transport the electromagnetic energy at 1550 nm, with transmission losses gammaT = 3 dB/655 nm and gammaL = 3 dB/443 nm and group velocities nugT = 0.177c0 and nugL = 0.327c0 for transverse and longitudinal polarizations, respectively, where c0 is the speed of light in a vacuum.

/pdf/hbox-au-sio-2-nanoring-plasmon-waveguides-at-optical-30i8wsgbw8.pdf

$\hbox{Au/SiO}_{2}$ Nanoring Plasmon Waveguides at Optical Communication Band

A low power Mach-Zehnder interferometer thermo-optic switch using free-standing silicon-on-insulator strip waveguides is demonstrated. The air gap provides thermal isolation between the waveguide interferometer arms and the underlying silicon substrate. The highly confined optical modes of the strip waveguides enable miniature heated cross-sections. The heating efficiency from on-chip resistive heaters is enhanced. Measurements of fabricated devices using 100 μm arm lengths at 1550 nm wavelength result in a switching power of 540 μW, a 10% - 90% switching rise time of 141 μs, and an extinction ratio of 25 dB.

Submilliwatt thermo-optic switches using free-standing silicon-on-insulator strip waveguides.

Tissue engineering seeks to develop functional tissues in a biomimetic environment in vitro. As the extracellular environment in vivo is composed of numerous nanostructures, fabrication of nanostructured substrates will be valuable for tissue engineering applications. In this article, we report a simple nanoimprint lithography (NIL) process to pattern nanostructures directly on tissue-culture polystyrene plates. By repeating this NIL process, three-dimensional scaffolds consisting of multiple-layer nanostructures were also fabricated. Bovine pulmonary artery smooth muscle cells were cultured on imprinted gratings ranging from 350 nm to 10 μm. The smooth muscle cells attached and proliferated well on these imprinted substrates without additional surface treatment. Cell elongation and alignment were observed on the micro- and nanopatterns, with the effect significantly more pronounced on the nanostructures.

/pdf/effects-of-nanoimprinted-patterns-in-tissue-culture-422qpmuegp.pdf

Ronald M. Reano

Papers

Nanopattern-induced changes in morphology and motility of smooth muscle cells.

Hybrid silicon and lithium niobate electro-optical ring modulator

$\hbox{Au/SiO}_{2}$ Nanoring Plasmon Waveguides at Optical Communication Band

Submilliwatt thermo-optic switches using free-standing silicon-on-insulator strip waveguides.

Effects of nanoimprinted patterns in tissue-culture polystyrene on cell behavior.