Younan Xia

Bio: Younan Xia is an academic researcher from The Wallace H. Coulter Department of Biomedical Engineering. The author has contributed to research in topics: Nanocages & Nanowire. The author has an hindex of 216, co-authored 943 publications receiving 175757 citations. Previous affiliations of Younan Xia include Washington University in St. Louis & University of Texas at Dallas.

Near-Infrared-Triggered Release of Ca 2+ Ions for Potential Application in Combination Cancer Therapy

Abstract: Calcium ion (Ca2+ ), an abundant species in the body, is a potential therapeutic ion with manageable side effects. However, the delivery of such a highly charged species represents a great challenge. Here, a nanosystem based on Au nanocages (AuNCs) and a phase-change material (PCM) for delivering calcium chloride (CaCl2 ) into cancer cells and thereby triggering cell death upon near-infrared (NIR) irradiation is demonstrated. In the absence of NIR irradiation, the nanosystem, denoted CaCl2 -PCM-AuNC, shows negligible cytotoxicity because the Ca2+ ions are fully encapsulated in a solid matrix. Upon NIR irradiation, the Ca2+ ions are swiftly released due to the melting of PCM matrix in response to photothermal heating. The sudden increase in intracellular Ca2+ causes disruption to the mitochondrial Ca2+ homeostasis and thus the loss of mitochondrial membrane potential, subsequently resulting in cell apoptosis. This nanosystem provides a new method for cancer treatment by tightly managing the intracellular concentration of a physiologically essential element.

Direct in Situ Observation and Analysis of the Formation of Palladium Nanocrystals with High-Index Facets

Abstract: Synthesizing concave-structured nanoparticles (NP) with high-index surfaces offers a viable method to significantly enhance the catalytic activity of NPs. Current approaches for fabricating concave NPs, however, are limited. Exploring novel synthesis methods requires a thorough understanding of the competing mechanisms that contribute to the evolution of surface structures during NP growth. Here, by tracking the evolution of Pd nanocubes into concave NPs at atomic scale using in situ liquid cell transmission electron microscopy, our study reveals that concave-structured Pd NPs can be formed by the cointroduction of surface capping agents and halogen ions. These two chemicals jointly create a new surface energy landscape of Pd NPs, leading to the morphological transformation. In particular, Pd atoms dissociate from the {100} surfaces with the aid of Cl– ions and preferentially redeposit to the corners and edges of the nanocubes when the capping agent polyvinylpyrrolidone is introduced, resulting in the for...

The effect of adipose-derived stem cell sheets and CTGF on early flexor tendon healing in a canine model.

Abstract: Intrasynovial tendon injuries are among the most challenging in orthopedics. Despite significant improvements in operative and rehabilitation methods, functional outcomes continue to be limited by adhesions, gap formation, and rupture. Adhesions result from excessive inflammation, whereas tendon gapping and rupture result from inflammation-induced matrix degradation and insufficient regeneration. Therefore, this study used a combined treatment approach to modulate inflammation with adipose-derived mesenchymal stromal cells (ASCs) while stimulating tendon regeneration with connective tissue growth factor (CTGF). ASCs were applied to the repair surface via cell sheets and CTGF was delivered to the repair center via porous sutures. The effect of the combined treatment was assessed fourteen days after repair in a canine flexor tendon injury model. CTGF, either alone or with ASCs, reduced inflammatory (IL1B and IL6) and matrix degrading (MMP3 and MMP13) gene expression, while increasing anti-inflammatory gene (IL4) expression and collagen synthesis compared to control repairs. The combined treatment was more effective than CTGF treatment alone, reducing the inflammatory IFNG and scar-associated COL3A1 gene expression and increasing CD146+ tendon stem/progenitor cells at the tendon surface and interior along the core suture tracks. Therefore, the combined approach is promising in promoting early flexor tendon healing and worthy of further investigation.

Edelmetall-Nanokristalle mit konkaven Oberflächen: Synthese und Anwendungen

Abstract: Metallische Nanokristalle mit konkaven Oberflachen sind aufgrund ihrer hoch indizierten Flachen, Oberflachenvertiefungen und scharfen Ecken und Kanten fur viele Anwendungen in der Katalyse, Plasmonik und oberflachenverstarkten Spektroskopie interessant. Zwei wesentliche Fragen stehen mit dieser neuartigen Klasse von Nanokristallen in Zusammenhang: 1) Wie erzeugt man eine konkave Oberflache mit negativer Krummung, die wegen ihres hoheren Energiegehalts im Vergleich zur konvexen Oberflache thermodynamisch benachteiligt ist? 2) Wie stabilisiert man die Morphologie eines Nanokristalls mit konkaven Strukturen an der Oberflache? In jungster Zeit wurden mehrere Protokolle zur Synthese von Edelmetall-Nanokristallen mit konkaven Oberflachen entwickelt. Dieser Aufsatz fasst diese Entwicklungen mit dem Ziel zusammen, neue Einblicke in die Kristallwachstumsmechanismen zu gewinnen. Wir konzentrieren uns auf zwei allgemeine Strategien: 1) ortsspezifisches Ablosen von Atomen durch Atzvorgange und galvanischen Austausch und 2) richtungskontrolliertes Uberwachsen durch flachenselektives Capping, kinetische Kontrolle und templatgelenkte Epitaxie. Wir beschreiben auserdem die katalytischen und elektrokatalytischen Eigenschaften konkaver Nanokristalle.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

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

Abstract: 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。

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346