Browsing by Author "Wang, Li-Fang"

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Azide-alkyne cycloaddition for universal post-synthetic modifications of nucleic acids and effective synthesis of bioactive nucleic acid conjugates
(2014)
Su, Yu-Chih
;
Lo, Yu-Lun
;
Hwang, Chi-Ching
;
Wang, Li-Fang
;
Wu, Min Hui
The regioselective post-synthetic modifications of nucleic acids are essential to studies of these molecules for science and applications. Here we report a facile universal approach by harnessing versatile phosphoramidation reactions to regioselectively incorporate alkynyl/azido groups into post-synthetic nucleic acids primed with phosphate at the 5\' termini. With and without the presence of copper, the modified nucleic acids were subjected to azide-alkyne cycloaddition to afford various nucleic acid conjugates including a peptide-oligonucleotide conjugate (POC) with high yield. The POC was inoculated with human A549 cells and demonstrated excellent cell-penetrating ability despite cell deformation caused by a small amount of residual copper chelated to the POC. The combination of phosphoramidation and azide-alkyne cycloaddition reactions thus provides a universal regioselective strategy to post-synthetically modify nucleic acids. This study also explicated the toxicity of residual copper in synthesized bioconjugates destined for biological systems.
Effective and site-specific phosphoramidation reaction for universally labeling nucleic acids
(2014-03-15)
Su, Yu-Chih
;
Chen, Hsing-Yin
;
Ko, Ni Chien
;
Hwang, Chi-Ching
;
Wu, Min Hui
Here we report efficient and selective postsynthesis labeling strategies, based on an advanced phosphoramidation reaction, for nucleic acids of either synthetic or enzyme-catalyzed origin. The reactions provided phosphorimidazolide intermediates of DNA or RNA which, whether reacted in one pot (one-step) or purified (two-step), were directly or indirectly phosphoramidated with label molecules. The acquired fluorophore-labeled nucleic acids, prepared from the phosphoramidation reactions, demonstrated labeling efficacy by their F/N ratio values (number of fluorophores per molecule of nucleic acid) of 0.02-1.2 which are comparable or better than conventional postsynthesis fluorescent labeling methods for DNA and RNA. Yet, PCR and UV melting studies of the one-step phosphoramidation-prepared FITC-labeled DNA indicated that the reaction might facilitate nonspecific hybridization in nucleic acids. Intrinsic hybridization specificity of nucleic acids was, however, conserved in the two-step phosphoramidation reaction. The reaction of site-specific labeling nucleic acids at the 5'-end was supported by fluorescence quenching and UV melting studies of fluorophore-labeled DNA. The two-step phosphoramidation-based, effective, and site-specific labeling method has the potential to expedite critical research including visualization, quantification, structural determination, localization, and distribution of nucleic acids in vivo and in vitro. (C) 2013 Elsevier Inc. All rights reserved.
Folic acid-Pluronic F127 magnetic nanoparticle clusters for combined targeting, diagnosis, and therapy applications
(2009-10-01)
Lin, Jia-Jyun
;
Chen, Jenn-Shing
;
Huang, Shih-Jer
;
Ko, Jyun-Han
;
Wang, Yu-Ming
Superparamagnetic iron oxides possess specific magnetic properties in the presence of an external magnetic field, which make them an attractive platform as contrast agents for magnetic resonance imaging (MRI) and as carriers for drug delivery. In this study, we investigate the drug delivery and the MRI properties of folate-mediated water-soluble iron oxide incorporated into micelles. Pluronic (R) F127 (PF127), which can be self-assembled into micelles upon increasing concentration or raising temperatures, is used to decorate water-soluble polyacrylic acid-bound iron oxides (PAAIO) via a chemical reaction. Next, the hydrophobic dye Nile red is encapsulated into the hydrophobic poly(propylene oxide) compartment of PF127 as a model drug and as a fluorescent agent. Upon encapsulation, PAAIO retains its superparamagnetic characteristics, and thus can be used for MR imaging. A tumor-specific targeting ligand, folic acid (FA), is conjugated onto PF127-PAAIO to produce a multifunctional superparamagnetic iron oxide, FA-PF127-PAAIO. FA-PF127-PAAIO can be simultaneously applied as a diagnostic and therapeutic agent that specifically targets cancer cells that overexpress folate receptors in their cell membranes. PF127-PAAIO is used as a reference group. Based on FTIR and UV-vis absorbance spectra, the successful synthesis of PF127-PAAIO and FA-PF127-PAAIO is realized. The magnetic nanoparticle clusters of PF127-PAAIO and FA-PF127-PAAIO are visualized by transmission electron microscope (TEM). FA-PF127-PAAIO, together with a targeting ligand, displays a higher intracellular uptake into KB cells. This result is confirmed by laser confocal scanning microscopy (CLSM), flow cytometry, and atomic absorption spectroscopy (AAS) studies. The hysteresis curves, generated by using a superconducting quantum interference device (SQUID) magnetometer analysis, demonstrate that the magnetic nanoparticles are superparamagnetic with insignificant hysteresis. The MITT assay explains the negligible cell cytotoxicity of PF127-PAAIO and FA-PF127-PAAIO. In KB cells, the in vitro MRI study indicates the better T(2)-weighted images in FA-PF127-PAAIO than in PF127-PAAIO. (C) 2009 Elsevier Ltd. All rights reserved.