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.

Histone deacetylase inhibitors are neuroprotective and preserve NGF-mediated cell survival following traumatic brain injury.

Abstract: Acute traumatic brain injury (TBI) is associated with long-term cognitive and behavioral dysfunction. In vivo studies have shown histone deacetylase inhibitors (HDACis) to be neuroprotective following TBI in rodent models. HDACis are intriguing candidates because they are capable of provoking widespread genetic changes and modulation of protein function. By using known HDACis and a unique small-molecule pan-HDACi (LB-205), we investigated the effects and mechanisms associated with HDACi-induced neuroprotection following CNS injury in an astrocyte scratch assay in vitro and a rat TBI model in vivo. We demonstrate the preservation of sufficient expression of nerve growth factor (NGF) and activation of the neurotrophic tyrosine kinase receptor type 1 (TrkA) pathway following HDACi treatment to be crucial in stimulating the survival of CNS cells after TBI. HDACi treatment up-regulated the expression of NGF, phospho-TrkA, phospho-protein kinase B (p-AKT), NF-κB, and B-cell lymphoma 2 (Bcl-2) cell survival factors while down-regulating the expression of p75 neurotrophin receptor (NTR), phospho-JNK, and Bcl-2–associated X protein apoptosis factors. HDACi treatment also increased the expression of the stem cell biomarker nestin, and decreased the expression of reactive astrocyte biomarker GFAP within damaged tissue following TBI. These findings provide further insight into the mechanisms by which HDACi treatment after TBI is neuroprotective and support the continued study of HDACis following acute TBI.

Real-time video imaging of protease expression in vivo.

Abstract: We demonstrate the first true real-time in vivo video imaging of extracellular protease expression using an ultrafast-acting and extended-use activatable probe. This simple, one-step technique is capable of boosting fluorescent signals upon target protease cleavage as early as 30 minutes from injection in a small animal model and is able to sustain the strong fluorescent signal up to 24 hours. Using this method, we video imaged the expression and inhibition of matrix metalloproteinases (MMPs) in a tumor-bearing mouse model. The current platform can be universally applied to any target protease of interest with a known peptide substrate and is adaptable to a wide range of real-time imaging applications with high throughputs such as for in vivo drug screening, examinations of the therapeutic efficacy of drugs, and monitoring of disease onset and development in animal models.

Degradable hollow mesoporous silicon/carbon nanoparticles for photoacoustic imaging-guided highly effective chemo-thermal tumor therapy in vitro and in vivo

Abstract: The development of nanoscaled theranostic agents for cancer combination therapies has received intensive attention in recent years. In this report, a degradable hollow mesoporous PEG-Si/C-DOX NP is designed and fabricated for pH-responsive, photoacoustic imaging-guided highly effective chemo-thermal combination therapy. The intrinsic hollow mesoporous structure endows the as-synthesized nanoparticles (NPs) with a high drug loading capacity (31.1%). Under NIR (808 nm) irradiation, the photothermal conversion efficiency of the Si/C NPs is as high as 40.7%. Preferential accumulation of the PEG-Si/C-DOX NPs around tumor tissue was demonstrated with photoacoustic images. Cellular internalization of the NPs and release of the DOX in nuclei are shown with fluorescent images. With efficient NIR photothermal conversion and high DOX loading capacity, the PEG-Si/C-DOX NPs are demonstrated to have remarkable cancer-cell-killing ability and to achieve complete in vivo tumor elimination via combinational chemo-thermal therapy. Last but not least, the NPs show good biodegradability and biosafety, making them a promising candidate for multifunctional drug delivery and cancer theranostic.

First Experience with Clinical-Grade [18F]FPP(RGD)2: An Automated Multi-step Radiosynthesis for Clinical PET Studies

Abstract: A reliable and routine process to introduce a new 18F-labeled dimeric RGD-peptide tracer ([18F]FPP(RGD)2) for noninvasive imaging of αvβ3 expression in tumors needed to be developed so the tracer could be evaluated for the first time in man. Clinical-grade [18F]FPP(RGD)2 was screened in mouse prior to our first pilot study in human. [18F]FPP(RGD)2 was synthesized by coupling 4-nitrophenyl-2-[18F]fluoropropionate ([18F]NPE) with the dimeric RGD-peptide (PEG3-c(RGDyK)2). Imaging studies with [18F]FPP(RGD)2 in normal mice and a healthy human volunteer were carried out using small animal and clinical PET scanners, respectively. Through optimization of each radiosynthetic step, [18F]FPP(RGD)2 was obtained with RCYs of 16.9 ± 2.7% (n = 8, EOB) and specific radioactivity of 114 ± 72 GBq/μmol (3.08 ± 1.95 Ci/μmol; n = 8, EOB) after 170 min of radiosynthesis. In our mouse studies, high radioactivity uptake was only observed in the kidneys and bladder with the clinical-grade tracer. Favorable [18F]FPP(RGD)2 biodistribution in human studies, with low background signal in the head, neck, and thorax, showed the potential applications of this RGD-peptide tracer for detecting and monitoring tumor growth and metastasis. A reliable, routine, and automated radiosynthesis of clinical-grade [18F]FPP(RGD)2 was established. PET imaging in a healthy human volunteer illustrates that [18F]FPP(RGD)2 possesses desirable pharmacokinetic properties for clinical noninvasive imaging of αvβ3 expression. Further imaging studies using [18F]FPP(RGD)2 in patient volunteers are now under active investigation.

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