Browsing by Author "Zhu, Chengcheng"

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Glutathione boosting the cytotoxicity of a magnetic platinum(IV) nano-prodrug in tumor cells
(2016-01-01)
Zhu, Zhenzhu
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Wang, Zenghui
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Hao, Yigang
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Zhu, Chengcheng
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Jiao, Yang
Superparamagnetic iron oxide nanoparticles (SPIONs) are potential vehicles for targeted drug delivery and viable contrast agents for magnetic resonance imaging (MRI). A Pt-IV prodrug (HSPt) derived from functionalization of cisplatin with hydroxyl and succinate is conjugated with a poly(ethylene glycol) (PEG)-modified SPION for cancer therapy and monitoring of therapeutic responses. The relaxivity of HSPt-PEG-SPIONs is larger than that of commercial contrast agent Feridex, and a tumor-selective negative contrast is observed in MRI in a magnetic field. HSPt-PEG-SPIONs can be dissociated and reduced into PtII species by glutathione (GSH). Instead of forming DNA-Pt crosslinks, the reduced product induces direct DNA single- or double-strand breaks, which is uncommon for Pt drugs. The cytotoxicity of HSPt-PEG-SPIONs is positively correlated with the GSH level of tumor cells, which is opposite to the scenario of current Pt drugs. HSPt-PEG-SPIONs are as cytotoxic as cisplatin against cancer cells but are almost nontoxic towards normal cells. Since the mechanism of action of the nanocomposite is different from the established paradigm for Pt drugs, it may become a special theranostic agent for cancer treatment.
How HY-2A/GM altimeter performs in marine gravity derivation: assessment in the South China Sea
(2019-11-01)
Zhu, Chengcheng
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Guo, Jinyun
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Hwang, Cheinway
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Gao, Jinyao
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Yuan, Jiajia
HY-2A is China's first satellite altimeter mission, launched in Aug. 2011. Its geodetic mission (GM) started from 2016 March 30 till present, collecting sea surface heights for about five 168-d cycles. To test how the HY-2A altimeter performs in marine gravity derivation, we use the least-squares collocation method to determine marine gravity anomalies on 1' x 1' grids around the SouthChina Sea (covering 0 degrees-30 degrees N, 105 degrees E-125 degrees E) from the HY-2A/GM-measured geoid gradients. We assess the qualities of the HY-2A/GM-derived gravity over different depths and areas using the bias and tilt-adjusted ship-borne gravity anomalies from the U.S. National Centers for Environmental Information (NCEI) and the Second Institute of Oceanography, Ministry of Natural Resources (MNR) of P. R. China. The RMS difference between the HY-2A/GM-derived and the NCEI ship-borne gravity is 5.91 mGal, and is 5.33 mGal when replacing the HY-2A value from the Scripps Institution of Oceanography (SIO) V23.1 value. The RMS difference between the HY-2A/GM-derived and the MNR ship-borne gravity is 2.90 mGal, and is 2.76 mGal when replacing the HY-2A value from the SIO V23.1 value. The RMS difference between the HY-2A and SIO V23.1 value is 3.57 mGal in open sea areas at least 20 km far away from the coast. In general, the difference between the HY-2A/GM-derived gravity and ship-borne gravity decreases with decreasing gravity field roughness and increasing depth. HY-2A results in the lowest gravity accuracy in areas with islands or reefs. Our assessment result suggests that HY-2A can compete with other Ku-band altimeter missions in marine gravity derivation.
Marine gravity determined from multi-satellite GM/ERM altimeter data over the South China Sea: SCSGA V1.0
(2020-05-06)
Zhu, Chengcheng
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Guo, Jinyun
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Gao, Jinyao
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Liu, Xin
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Hwang, Cheinway
High-precision and high-resolution gravity fields can be derived from multi-source satellite altimeter data. A gravity anomaly model around the South China Sea (SCSGA) V1.0 on a 1 ' x 1 ' grid is established from sea surface heights (SSHs) of several geodetic missions (GMs) and exact repeat missions. Gridded deflections of the vertical are first calculated from SSHs by the least squares collocation (LSC) method and then used to derive gravity anomalies by the inverse Vening Meinesz formula. In gravity derivation processing, we establish an approximate relationship among the precision of altimetric gravity, precision of geoid gradients, and density of geoid gradients (the average number of geoid gradients per 1 ' x 1 ' region). The weights of geoid gradients from the Ka-band altimeter for the LSC are innovatively determined by an iterative method. Finally, SCSGA V1.0 is assessed by ship-borne gravity anomalies and marine gravity models. The performance of GMs in gravity derivation is evaluated. In general, the altimetric gravity precision in regions with many islands and reefs increases more obviously than those in other regions when the geoid gradient density increases. The standard deviation of SCSGA V1.0 is 2.78 mGal, which is slightly better than those of four recognized global marine gravity models around the SCS. CryoSat-2 is the most important dataset for SCSGA V1.0. Ka-band SARAL/AltiKa plays a major role in gravity derivation, and the contribution of Haiyang-2A is greater than those of other Ku-band satellites, except CryoSat-2. SCSGA V1.0 is concluded to reach an international advanced level for marine gravity from altimeter data around the SCS.