Cellular uptake, intracellular trafficking, and antitumor efficacy of doxorubicin-loaded reduction-sensitive micelles.

Reduction-sensitive micelles were prepared from monomethoxy-poly(ethylene glycol)-S-S-hexadecyl (mPEG-S-S-C16), an amphiphilic poly(ethylene glycol) derivative containing a disulfide bond. The micelles were then used for the intracellular delivery of the anticancer drug doxorubicin (DOX) into tumor cells, and the cellular uptake mechanisms of the micelles were determined. To serve as a control, monomethoxy-poly(ethylene glycol)-C-C-hexadecyl (mPEG-C-C-C16) with an analogous structure but without a disulfide bond was also prepared. The polymer could self-assemble into micelles in an aqueous solution and be loaded with high-content DOX. In vitro release studies revealed that DOX-loaded mPEG-S-S-C16 micelles released DOX faster than DOX-loaded mPEG-C-C-C16 micelles in the presence of dithiothreitol (DTT), but showed similar release rates in the absence of DTT. MTT assay demonstrated significantly enhanced cytotoxicity of DOX-loaded mPEG-S-S-C16 micelles against the human cervical cancer cells (HeLa) compared with DOX-loaded mPEG-C-C-C16 micelles, but there was no significant difference in the cytotoxicity between the two DOX-loaded micelles against the african green monkey SV40-transformed kidney fibroblast cells (COS-7). Confocal laser scanning microscopy observation and flow cytometry analyses indicated that DOX-loaded mPEG-S-S-C16 micelles were efficiently internalized into HeLa cells, released DOX into the cytoplasm, and entered the nuclei. By contrast, in the case of DOX-loaded mPEG-C-C-C16 micelles, little DOX was found in the nuclei. Endocytosis inhibition results proved that both mPEG-S-S-C16 and mPEG-C-C-C16 micelles entered the HeLa cells mainly through the clathrin-mediated endocytosis pathway, and caveolae-mediated endocytosis was involved to a small extent. These results indicated that the different behaviors of cell uptake between reduction-sensitive and -insensitive micelles may occur after the micelles were internalized into the cells, but not during endocytosis, and the potential of this reduction-sensitive polymer for the effective intracellular delivery of anticancer drugs.

Cui C ，Xue YN ，Wu M ，Zhang Y ，Yu P ，Liu L ，Zhuo RX ，Huang SW ... -  《-》

Reduction-sensitive micelles with sheddable PEG shells self-assembled from a Y-shaped amphiphilic polymer for intracellular doxorubicine release.

A new type of shell-sheddable micelles with disulfide linkages between the hydrophobic polyester core and hydrophilic poly(ethylene glycol) (PEG) shell was developed based on Y-shaped amphiphilic polymers mPEG-S-S-(PCL)2. The micelles were then used for the glutathione-mediated intracellular delivery of the anticancer drug doxorubicin (DOX) into tumor cells. The polymer could self-assemble into micelles with an average diameter of 135nm in aqueous solution and load DOX at a total content of 3.6%. The hydrophilic PEG shell of these micelles could be shed in the presence of reducing agent dithiothreitol (DTT), which resulted in size change of the micelles. In vitro release studies revealed that DOX-loaded mPEG-S-S-(PCL)2 micelles exhibited faster DOX release in the presence of DTT. MTT assay demonstrated that DOX-loaded mPEG-S-S-(PCL)2 micelles showed higher cytotoxicity against 10mM of glutathione monoester (GSH-OEt) pretreated HeLa cells than that of the non-pretreated ones. Confocal laser scanning microscopy and flow cytometry analyses indicated that DOX-loaded mPEG-S-S-(PCL)2 micelles were efficiently internalized into HeLa cells and exhibited faster DOX release in GSH-OEt-pretreated cells than in cells with no pretreatment. Endocytosis inhibition results proved that mPEG-S-S-(PCL)2 micelles entered the cells mainly through the clathrin-mediated endocytosis pathway, and caveolae-mediated endocytosis was involved to a small extent. These results indicate the great potential of the proposed Y-shaped reduction-sensitive polymer for application in effective intracellular anticancer drug delivery.

Cui C ，Yu P ，Wu M ，Zhang Y ，Liu L ，Wu B ，Wang CX ，Zhuo RX ，Huang SW ... -  《-》

Intracellular release of doxorubicin from core-crosslinked polypeptide micelles triggered by both pH and reduction conditions.

Wu L ，Zou Y ，Deng C ，Cheng R ，Meng F ，Zhong Z ... -  《-》

Poly(L-aspartamide)-based reduction-sensitive micelles as nanocarriers to improve doxorubicin content in cell nuclei and to enhance antitumor activity.

A reduction-sensitive graft polymer PHEA-S-S-C16 with poly{α,β-[N-(2-hydroxyethyl)-L-aspartamide]} (PHEA) as a backbone and a disulfide-containing alkyl as a side chain (HOOC-S-S-C16 ) is synthesized and evaluated for intracellular DOX delivery. PHEA-S-S-C16 can self-assemble into micelles in aqueous media and load DOX at a total content of 7.3%. In vitro release studies reveal that the release rate of DOX from PHEA-S-S-C16 micelles is accelerated in the presence of DTT. The results of cell experiments indicate that DOX-loaded mPEG-S-S-C16 micelles can achieve rapid DOX release in HeLa cells, as compared with their reduction-insensitive counterparts. Endocytosis inhibition analysis indicates that PHEA-S-S-C16 micelles entered cells mainly via clathrin-mediated endocytosis.

Cui C ，Xue YN ，Wu M ，Zhang Y ，Yu P ，Liu L ，Zhuo RX ，Huang SW ... -  《-》

Poly(ethylene glycol) shell-sheddable magnetic nanomicelle as the carrier of doxorubicin with enhanced cellular uptake.

This research is aimed to develop a kind of poly(ethylene glycol) shell-sheddable magnetic nanomicelle as the carrier of doxorubicin (Dox) in order to enhance its cellular uptake ability, and achieve synchronous magnetic resonance imaging (MRI)-visible function. Firstly, the five-member rings in poly (L-succinimide) (PSI) were successively opened by the amino terminated disulfide-linked poly(ethylene glycol) monomethyl ether (mPEG-SS-NH2) and dopamine (DA) to produce the graft copolymer of mPEG-SS-NH-graft-PAsp-DA. And then, drug-loaded magnetic nanomicelles of mPEG-SS-NH-graft-PAsp-DA@Fe3O4.Dox were obtained by the Fe3O4 nanoparticle-induced self-assembly of mPEG-SS-NH-graft-PAsp-DA. These magnetic nanomicelles showed spherical shapes with average particle size of about 120 nm measured by dynamic light scattering (DLS). Due to the detachment of PEG shell in the presence of dithiothreitol (DTT), the magnetic nanomicelles showed accelerated in vitro release of Dox, and enhanced cellular uptake ability. Compared with free Dox, the Dox-loaded magnetic nanomicelles showed essential decreased cytotoxicity against Bel-7402 cell line. If its high r2 relaxation rate (221 mM(-1) s(-1)) and good negative contrast effect for magnetic resonance imaging (MRI) were taken into account, mPEG-SS-NH-graft-PAsp-DA@Fe3O4.Dox could be used as MRI-detectable drug carrier of Dox with enhanced cellular uptake ability.

Yu J ，Li X ，Luo Y ，Lu W ，Huang J ，Liu S ... -  《-》