52263-97-5Relevant articles and documents
Block copolymer micelles with acid-labile ortho ester side-chains: Synthesis, characterization, and enhanced drug delivery to human glioma cells
Tang, Rupei,Ji, Weihang,Panus, David,Palumbo, R. Noelle,Wang, Chun
, p. 18 - 27 (2011)
A new type of block copolymer micelles for pH-triggered delivery of poorly water-soluble anticancer drugs has been synthesized and characterized. The micelles were formed by the self-assembly of an amphiphilic diblock copolymer consisting of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic polymethacrylate block (PEYM) bearing acid-labile ortho ester side-chains. The diblock copolymer was synthesized by atom transfer radical polymerization (ATRP) from a PEG macro-initiator to obtain well-defined polymer chain-length. The PEG-b-PEYM micelles assumed a stable core-shell structure in aqueous buffer at physiological pH with a low critical micelle concentration as determined by proton NMR and pyrene fluorescence spectroscopy. The hydrolysis of the ortho ester side-chain at physiological pH was minimal yet much accelerated at mildly acidic pHs. Doxorubicin (Dox) was successfully loaded into the micelles at pH 7.4 and was released at a much higher rate in response to slight acidification to pH 5. Interestingly, the release of Dox at pH 5 followed apparently a biphasic profile, consisting of an initial fast phase of several hours followed by a sustained release period of several days. Dox loaded in the micelles was rapidly taken up by human glioma (T98G) cells in vitro, accumulating in the endolysosome and subsequently in the nucleus in a few hours, in contrast to the very low uptake of free drug at the same dose. The dose-dependent cytotoxicity of the Dox-loaded micelles was determined by the MTT assay and compared with that of the free Dox. While the empty micelles themselves were not toxic, the IC50 values of the Dox-loaded micelles were approximately ten-times (by 24 h) and three-times (by 48 h) lower than the free drug. The much enhanced potency in killing the multi-drug-resistant human glioma cells by Dox loaded in the micelles could be attributed to high intracellular drug concentration and the subsequent pH-triggered drug release. These results establish the PEG-b-PEYM block copolymer with acid-labile ortho ester side-chains as a novel and effective pH-responsive nano-carrier for enhancing the delivery of drugs to cancer cells.
Process for the preparation of 2,2-dialkoxy cyclic ortho esters derived from lactones
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, (2008/06/13)
This invention is directed to a process for the synthesis of 2,2-dialkoxy cyclic ortho esters derived from lactones which comprises reacting trialkyl orthoformate with boron trifluoride to give dialkoxymethylium tetrafluoroborate; reacting dialkoxymethylium tetrafluoroborate with a lactone to give the corresponding O-alkyllactonium tetrafluoroborate; and reacting the O-alkyllactonium tetrafluoroborate with an alkoxide, or alternatively with an alkanol in the presence of a base; wherein the first two steps of the process of the invention are conducted in the absence of solvents, other than the reactants themselves. The third step may also optionally be run without solvents. The invention is also directed to the preparation of the O-alkyllactonium tetrafluoroborate in one reaction vessel; that is, the boron trifluoride is added to the trialkyl orthoformate and the lactone in a single reaction vessel. As the intermediate dialkoxymethylium tetrafluoroborate is formed, it reacts in situ with the lactone in the reaction mixture, thus avoiding the additional steps of separating the dialkoxymethylium tetrafluoroborate and then reacting it with the lactone in a separate step and vessel.
