Xiaoyuan Chen

Bio: Xiaoyuan Chen is an academic researcher from National University of Singapore. The author has contributed to research in topics: Physics & Photothermal therapy. The author has an hindex of 149, co-authored 994 publications receiving 89870 citations. Previous affiliations of Xiaoyuan Chen include Brown University & University of Southern California.

Family of enhanced photoacoustic imaging agents for high-sensitivity and multiplexing studies in living mice.

Abstract: Photoacoustic imaging is a unique modality that overcomes to a great extent the resolution and depth limitations of optical imaging while maintaining relatively high contrast. However, since many diseases will not manifest an endogenous photoacoustic contrast, it is essential to develop exogenous photoacoustic contrast agents that can target diseased tissue(s). Here we present a family of novel photoacoustic contrast agents that are based on the binding of small optical dyes to single-walled carbon nanotubes (SWNT-dye). We synthesized five different SWNT-dye contrast agents using different optical dyes, creating five "flavors" of SWNT-dye nanoparticles. In particular, SWNTs that were coated with either QSY(21) (SWNT-QSY) or indocyanine green (SWNT-ICG) exhibited over 100-times higher photoacoustic contrast in living animals compared to plain SWNTs, leading to subnanomolar sensitivities. We then conjugated the SWNT-dye conjugates with cyclic Arg-Gly-Asp peptides to molecularly target the α(v)β(3) integrin, which is associated with tumor angiogenesis. Intravenous administration of these tumor-targeted imaging agents to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. Finally, we were able to spectrally separate the photoacoustic signals of SWNT-QSY and SWNT-ICG in living animals injected subcutaneously with both particles in the same location, opening the possibility for multiplexing in vivo studies.

Engineered iron-oxide-based nanoparticles as enhanced T1 contrast agents for efficient tumor imaging.

Abstract: We report the design and synthesis of small-sized zwitterion-coated gadolinium-embedded iron oxide (GdIO) nanoparticles, which exhibit a strong T1 contrast effect for tumor imaging through enhanced permeation and retention effect and the ability to clear out of the body in living subjects. The combination of spin-canting effects and the collection of gadolinium species within small-sized GdIO nanoparticles led to a significantly enhanced T1 contrast effect. For example, GdIO nanoparticles with a diameter of ∼4.8 nm exhibited a high r1 relaxivity of 7.85 mM–1·S–1 and a low r2/r1 ratio of 5.24. After being coated with zwitterionic dopamine sulfonate molecules, the 4.8 nm GdIO nanoparticles showed a steady hydrodynamic diameter (∼5.2 nm) in both PBS buffer and fetal bovine serum solution, indicating a low nonspecific protein absorption. This study provides a valuable strategy for the design of highly sensitive iron-oxide-based T1 contrast agents with relatively long circulation half-lives (∼50 min), efficien...

An Ultrasound Activated Vesicle of Janus Au-MnO Nanoparticles for Promoted Tumor Penetration and Sono-Chemodynamic Therapy of Orthotopic Liver Cancer

Abstract: Sonodynamic therapy (SDT) has the advantages of high penetration, non-invasiveness, and controllability, and it is suitable for deep-seated tumors. However, there is still a lack of effective sonosensitizers with high sensitivity, safety, and penetration. Now, ultrasound (US) and glutathione (GSH) dual responsive vesicles of Janus Au-MnO nanoparticles (JNPs) were coated with PEG and a ROS-sensitive polymer. Upon US irradiation, the vesicles were disassembled into small Janus Au-MnO nanoparticles (NPs) with promoted penetration ability. Subsequently, GSH-triggered MnO degradation simultaneously released smaller Au NPs as numerous cavitation nucleation sites and Mn2+ for chemodynamic therapy (CDT), resulting in enhanced reactive oxygen species (ROS) generation. This also allowed dual-modality photoacoustic imaging in the second near-infrared (NIR) window and T1 -MR imaging due to the released Mn2+ , and inhibited orthotopic liver tumor growth via synergistic SDT/CDT.

Tumor Microenvironment-Triggered Supramolecular System as an In Situ Nanotheranostic Generator for Cancer Phototherapy.

Abstract: The efficacy of photosensitizers in cancer phototherapy is often limited by photobleaching, low tumor selectivity, and tumor hypoxia. Assembling photosensitizers into nanostructures can improve photodynamic therapy efficacy and the safety profile of photosensitizers. Herein by employing supramolecular assembly, enhanced theranostic capability of Mn2+-assisted assembly of a photosensitizer (sinoporphyrin sodium, DVDMS) is demonstrated. A tumor environment-triggered coassembly strategy is further developed to form Mn/DVDMS nanotheranostics (nanoDVD) for cancer phototherapy. MnO2 nanosheets serve as a highly effective DVDMS carrier and in situ oxygen and nanoDVD generator. In MCF-7 cells and xenograft tumors, MnO2/DVDMS is reduced by glutathione (GSH) and H2O2 and reassembled into nanoDVD, which can be monitored by activated magnetic resonance/fluorescence/photoacoustic signals. Intriguingly, the decrease of GSH, the production of O2, and the formation of nanoDVD are shown to be synergistic with phototherapy to improve antitumor efficacy in vitro and in vivo, offering a new avenue for cancer theranostics.

pH-Controlled Gas-Generating Mineralized Nanoparticles: A Theranostic Agent for Ultrasound Imaging and Therapy of Cancers

Abstract: We report a theranostic nanoparticle that can express ultrasound (US) imaging and simultaneous therapeutic functions for cancer treatment. We developed doxorubicin-loaded calcium carbonate (CaCO3) hybrid nanoparticles (DOX-CaCO3-MNPs) through a block copolymer templated in situ mineralization approach. The nanoparticles exhibited strong echogenic signals at tumoral acid pH by producing carbon dioxide (CO2) bubbles and showed excellent echo persistence. In vivo results demonstrated that the DOX-CaCO3-MNPs generated CO2 bubbles at tumor tissues sufficient for echogenic reflectivity under a US field. In contrast, the DOX-CaCO3-MNPs located in the liver or tumor-free subcutaneous area did not generate the CO2 bubbles necessary for US contrast. The DOX-CaCO3-MNPs could also trigger the DOX release simultaneously with CO2 bubble generation at the acidic tumoral environment. The DOX-CaCO3-MNPs displayed effective antitumor therapeutic activity in tumor-bearing mice. The concept described in this work may serve a...

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

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。

Chemistry and properties of nanocrystals of different shapes.

Abstract: The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102