Browsing by Author "Lin, Kun-Liang"

Now showing 1 - 3 of 3

Imaging specificity of MR-optical imaging agents following the masking of surface charge by poly(ethylene glycol)
(2013-05-01)
Wu, Shou-Cheng
;
Lin, Kun-Liang
;
Wang, Tzu-Pin
;
Tzou, Shey-Cherng
;
Singh, Gyan
The coupling of specific antibodies to imaging agents often improves imaging specificity. However, free amine groups designed for the coupling can cause nonspecific binding of the imaging agents. We report here development of a nanocarrier, MnMEIO-silane-NH2-mPEG nanoparticles (NPs), consisting of a manganese-doped iron oxide nanoparticle core (MnMEIO), a copolymer shell of silane and amine-functionalized poly(ethylene glycol) (silane-EA-mPEG). The key feature in MnMEIO-silane-NH2-mPEG is the flexible PEG, which masks the non-conjugated reactive amine groups (-NH2 <-> -NH3+) and reduces nonspecific binding of MnMEIO-silane-NH2-mPEG to cells. The amine groups on MnMEIO-silane-NH2-mPEG were conjugated with the fluorescent dye, Cy777 or antibodies [Erbitux (Erb)] to form a MR-optical imaging contrast agent (MnMEIO-silane-NH2-(Erb)-mPEG) for EGFR-expressing tumors. Confocal microscopic and flow cytometric analyses showed that MnMEIO-silane-NH2-(Erb)-mPEG displayed low nonspecific binding. Moreover, TEM images showed that MnMEIO-silane-NH2-(Erb)-mPEG were endocytosed by EGFR-expressing cells. In line with their EGFR expression levels, A431, PC-3, and Colo-205 tumors treated with MnMEIO-silane-NH2-(Erb)-mPEG NPs showed -97.1%, -49.7%, and -2.8% contrast enhancement, respectively, in in vitro T-2-weighted MR imaging. In vivo T-2-weighted MR imaging and optical images showed that MnMEIO-silane-NH2-(Erb)mPEG could specifically and effectively target to EGFR-expressing tumors in nude mice; the relative contrast enhancements were 7.94 (at 2 h) and 7.59 (at 24 h) fold higher in A431 tumors as compared to the EGFR-negative Colo-205 tumors. On the contrary, MnMEIO-silane-NH2-(Erb) NPs showed only 1.44 (at 2 h) and 1.52 (at 24 h) fold higher in EGFR-positive tumors as compared to the EGFR-negative tumors. Finally, antibodies can be readily changed to allow imaging of other tumors bearing different antigens. These data indicate that masking surface charges on contrast agents is a useful strategy to improve imaging efficacy. (c) 2013 Elsevier Ltd. All rights reserved.
In Vitro Selection and Characterization of a Novel Zn(II)-Dependent Phosphorothiolate Thiolesterase Ribozyme
(2012-01-10)
Wang, Tzu-Pin
;
Su, Yu-Chih
;
Chen, Yi
;
Liou, Yi-Ming
;
Lin, Kun-Liang
Here we present the in vitro selection of a novel ribozyme specific for Zn(2+)-dependent catalysis on hydrolysis of a phosphorothiolate thiolester bond. The ribozyme, called the TW17 ribozyme, was evolved and selected from an artificial RNA pool covalently linked to a biotin-containing substrate through the phosphorothiolate thiolester bond. The secondary structure for the evolved ribozyme consisted of three major helices and three loops. Biochemical and chemical studies of ribozyme-catalyzed reaction products provided evidence that the ribozyme specifically catalyzes hydrolysis of the phosphorothiolate thiolester linkage. A successful ribozyme construct with active catalysis in trans further supported the determined ribozyme structure and indicated the potential of the ribozyme for multiple-substrate turnover. The ribozyme also requires Zn(2+) and Mg(2+) for maximal catalysis. The TW17 ribozyme, in the presence of Zn(2+) and Mg(2+), conferred a rate enhancement of at least S orders of magnitude when compared to the estimated rate of the uncatalyzed reaction. The ribozyme completely lost catalytic activity in the absence of Zn(2+), like Zn(2+)-dependent protein hydrolases. The discovery and characterization of the TW17 ribozyme suggest additional roles for Zn(2+) in ribozyme catalysts.
Targeted RGD nanoparticles for highly sensitive in vivo integrin receptor imaging
(2012-01-01)
Lin, Ren-Yen
;
Dayananda, Kasala
;
Chen, Ting-Jung
;
Chen, Chiao-Yun
;
Liu, Gin-Chung
A new magnetic resonance imaging (MRI) contrast bearing RGD peptide is reported. In this study, ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with various sizes were prepared. Particles sizes between 6 and 13?nm were tuned by varying the stirring rate. Remarkable negative contrast was observed because USPIO nanoparticles (13.1?+/-?2.1?nm) generated high transversal relaxivity r2 (188?+/-?3?m m-1?s-1) and saturation magnetization (94?emu?g-1 Fe). The USPIO nanoparticles were coated with PDA [2-(pyridyldithio)-ethylamine; PDA nanoparticles] containing functional polymer, which can be readily synthesized by Michael addition. The PDA nanoparticles were conjugated with RGD peptide (RGD nanoparticles) for targeting the specific site. The target specificity and high relaxivity allowed RGD nanoparticles to differentiate the expression level of integrin receptor on several cell lines and tumors (MCF-7, A-549, HT-29 and HT-1080) by in vitro and in vivo MR imaging. Importantly, a remarkable negative contrast (-51.3?+/-?6.7%) was observed for in vivo MR imaging of MCF-7 tumor. This result implies that the RGD nanoparticles that greatly enhance the MR imaging are highly sensitive for early stage tumor detection. Copyright (c) 2012 John Wiley & Sons, Ltd.