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.

Ultrahigh sensitivity carbon nanotube agents for photoacoustic molecular imaging in living mice.

Abstract: Photoacoustic imaging is an emerging 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 novel photoacoustic contrast agent, Indocyanine Green dye-enhanced single walled carbon nanotube (SWNT-ICG). We conjugated this contrast agent with cyclic Arg-Gly-Asp (RGD) peptides to molecularly target the Rv� 3 integrins, which are associated with tumor angiogenesis. Intravenous administration of this tumor-targeted contrast agent to tumor-bearing mice showed significantly higher photoacoustic signal in the tumor than in mice injected with the untargeted contrast agent. The new contrast agent gave a markedly 300 times higher photoacoustic contrast in living tissues than previously reported SWNTs, leading to subnanomolar sensitivities. Finally, we show that the new contrast agent can detect ∼20 times fewer cancer cells than previously reported SWNTs.

Fenton-Reaction-Acceleratable Magnetic Nanoparticles for Ferroptosis Therapy of Orthotopic Brain Tumors.

Abstract: Cancer is one of the leading causes of morbidity and mortality in the world, but more cancer therapies are needed to complement existing regimens due to problems of existing cancer therapies. Herein, we term ferroptosis therapy (FT) as a form of cancer therapy and hypothesize that the FT efficacy can be significantly improved via accelerating the Fenton reaction by simultaneously increasing the local concentrations of all reactants (Fe2+, Fe3+, and H2O2) in cancer cells. Thus, Fenton-reaction-acceleratable magnetic nanoparticles, i.e., cisplatin (CDDP)-loaded Fe3O4/Gd2O3 hybrid nanoparticles with conjugation of lactoferrin (LF) and RGD dimer (RGD2) (FeGd-HN@Pt@LF/RGD2), were exploited in this study for FT of orthotopic brain tumors. FeGd-HN@Pt@LF/RGD2 nanoparticles were able to cross the blood–brain barrier because of its small size (6.6 nm) and LF-receptor-mediated transcytosis. FeGd-HN@Pt@LF/RGD2 can be internalized into cancer cells by integrin αvβ3-mediated endocytosis and then release Fe2+, Fe3+, and...

In vivo Near-Infrared Fluorescence Imaging of Integrin αvβ3 in Brain Tumor Xenografts

Abstract: Noninvasive visualization of cell adhesion molecule alpha(v)beta(3) integrin expression in vivo has been well studied by using the radionuclide imaging modalities in various preclinical tumor models. A literature survey indicated no previous use of cyanine dyes as contrast agents for in vivo optical detection of tumor integrin. Herein, we report the integrin receptor specificity of novel peptide-dye conjugate arginine-glycine-aspartic acid (RGD)-Cy5.5 as a contrast agent in vitro, in vivo, and ex vivo. The RGD-Cy5.5 exhibited intermediate affinity for alpha(v)beta(3) integrin (IC(50) = 58.1 +/- 5.6 nmol/L). The conjugate led to elevated cell-associated fluorescence on integrin-expressing tumor cells and endothelial cells and produced minimal cell fluorescence when coincubated with c(RGDyK). In vivo imaging with a prototype three-dimensional small-animal imaging system visualized subcutaneous U87MG glioblastoma xenograft with a broad range of concentrations of fluorescent probe administered via the tail vein. The intermediate dose (0.5 nmol) produces better tumor contrast than high dose (3 nmol) and low dose (0.1 nmol) during 30 minutes to 24 hours postinjection, because of partial self-inhibition of receptor-specific tumor uptake at high dose and the presence of significant amount of background fluorescence at low dose, respectively. The tumor contrast was also dependent on the mouse viewing angles. Tumor uptake of RGD-Cy5.5 was blocked by unlabeled c(RGDyK). This study suggests that the combination of the specificity of RGD peptide/integrin interaction with near-infrared fluorescence detection may be applied to noninvasive imaging of integrin expression and monitoring anti-integrin treatment efficacy providing near real-time measurements.

Spectral Measurement of Electron Antineutrino Oscillation Amplitude and Frequency at Daya Bay

Abstract: A measurement of the energy dependence of antineutrino disappearance at the Daya Bay reactor neutrino experiment is reported. Electron antineutrinos (ν¯_e) from six 2.9 GW_(th) reactors were detected with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls. Using 217 days of data, 41 589 (203 809 and 92 912) antineutrino candidates were detected in the far hall (near halls). An improved measurement of the oscillation amplitude sin^2 2θ_(13) = 0.090^(+0.008)_(−0.009) and the first direct measurement of the ν¯e mass-squared difference |Δm2ee|=(2.59^(+0.19)_(−0.20))×10^−3 eV^2 is obtained using the observed ν¯_e rates and energy spectra in a three-neutrino framework. This value of |Δm^(2)_(ee)| is consistent with |Δm^(2)_(μμ)| measured by muon neutrino disappearance, supporting the three-flavor oscillation model.

microPET Imaging of Glioma Integrin αvβ3 Expression Using 64Cu-Labeled Tetrameric RGD Peptide

Abstract: Integrin αvβ3 plays a critical role in tumor-induced angiogenesis and metastasis and has become a promising diagnostic indicator and therapeutic target for various solid tumors. Radiolabeled RGD peptides that are integrin specific can be used for noninvasive imaging of integrin expression level as well as for integrin-targeted radionuclide therapy. Methods: In this study we developed a tetrameric RGD peptide tracer 64Cu-DOTA-E{E[c(RGDfK)]2}2 (DOTA is 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid) for PET imaging of integrin αvβ3 expression in female athymic nude mice bearing the subcutaneous UG87MG glioma xenografts. Results: The RGD tetramer showed significantly higher integrin binding affinity than the corresponding monomeric and dimeric RGD analogs, most likely due to a polyvalency effect. The radiolabeled peptide showed rapid blood clearance (0.61 ± 0.01 %ID/g at 30 min and 0.21 ± 0.01 %ID/g at 4 h after injection, respectively [%ID/g is percentage injected dose per gram]) and predominantly renal excretion. Tumor uptake was rapid and high, and the tumor washout was slow (9.93 ± 1.05 %ID/g at 30 min after injection and 4.56 ± 0.51 %ID/g at 24 h after injection). The metabolic stability of 64Cu-DOTA-E{E[c(RGDfK)]2}2 was determined in mouse blood, urine, and liver and kidney homogenates at different times after tracer injection. The average fractions of intact tracer in these organs at 1 h were approximately 70%, 58%, 51%, and 26%, respectively. Noninvasive microPET studies showed significant tumor uptake and good contrast in the subcutaneous tumor-bearing mice, which agreed well with the biodistribution results. Integrin αvβ3 specificity was demonstrated by successful blocking of tumor uptake of 64Cu-DOTA-E{E[c(RGDfK)]2}2 in the presence of excess c(RGDyK) at 1 h after injection. The highest absorbed radiation doses determined for the human reference adult were received by the urinary bladder wall (0.262 mGy/MBq), kidneys (0.0296 mGy/MBq), and liver (0.0242 mGy/MBq). The average effective dose resulting from a single 64Cu-DOTA-E{E[c(RGDfK)]2}2 injection was estimated to be 0.0164 mSv/MBq. Conclusion: The high integrin and avidity and favorable biokinetics make 64Cu-DOTA-E{E[c(RGDfK)]2}2 a promising agent for peptide receptor radionuclide imaging and therapy of integrin-positive tumors.

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