Folate-conjugated amphiphilic block copolymer micelle for targeted and redox-responsive delivery of doxorubicin.

In this paper, novel folate-conjugated and redox-responsive crosslinked block copolymer was successfully synthesized for targeted and controlled release of doxorubicin (DOX) to cancer cells. Folate-conjugated poly(ethylene glycol)-b-copolycarbonates (FA-PEG-b-P(MAC-co-DTC)) and methoxy poly(ethylene glycol)-b-copolycarbonates (mPEG-b-P(MAC-co-DTC)) were firstly synthesized by enzymatic method. FA-PEG/mPEG-b-P(MAC-co-DTC)-SS was then obtained by further crosslinking reaction with cystamine. Non-conjugated crosslinked copolymer mPEG-b-P(MAC-co-DTC)-SS- and non-conjugated uncrosslinked copolymer mPEG-b-P(MAC-co-DTC) were also synthesized for comparison. All the amphiphlic copolymers could self-assemble to form nano-sized micelles which dispersed in spherical shape before and after DOX loading. The core crosslinking structure of FA-PEG/mPEG-b-P(MAC-co-DTC)-SS could improve the micellar stability and drug loading capacity, while in vitro release studies also showed more sustained drug release behavior which could be accelerated in reductive condition. Moreover, confocal laser scanning microscopy indicated that the conjugation of FA could enhance the cellular uptake efficiency obviously via FA-receptor-mediated endocytosis, and MTT assays demonstrated highly potent cytotoxic activity of FA-PEG/mPEG-b-P(MAC-co-DTC)-SS.

Mercaptan acids modified amphiphilic copolymers for efficient loading and release of doxorubicin.

In this paper, four different kinds of mercaptan acids modified amphiphilic copolymers mPEG-b-PATMC-g-SRCOOH (R=CH2, CH2CH2, (CH2)10 and CH(COOH)CH2) were successfully synthesized by thiol-ene "click" reaction between pendent carbon-carbon double bonds of PEG-b-PATMC and thiol groups of thioglycolic acid, 3-mercaptopropionic acid, 11-mercaptoundecanoic acid or 2-mercaptosuccinic acid. DLS and TEM measurements showed that all the mPEG-b-PATMC-g-SRCOOH copolymers could self-assemble to form micelles which dispersed in spherical shape with nano-size before and after DOX loading. The positively-charged DOX could effectively load into copolymer micelles via synergistic hydrophobic and electrostatic interactions. All DOX-loaded mPEG-b-PATMC-g-SRCOOH micelles displayed sustained drug release behavior without an initial burst which could be further adjusted by the conditions of ionic strength and pH. Especially in the case of mPEG-b-PATMC-g-S(CH2)10COOH (P3) micelles, the suitable hydrophobility and charge density were not only beneficial to improve the DOX-loading efficiency, they were also good for obtaining smaller particle size, higher micelle stability and more timely drug delivery. Confocal laser scanning microscopy (CLSM) and MTT assays further demonstrated efficient cellular uptake of DOX delivered by mPEG-b-PATMC-g-SRCOOH micelles and potent cytotoxic activity against cancer cells.

Amphiphilic copolymers with pendent carboxyl groups for high-efficiency loading and controlled release of doxorubicin.

In this paper, biodegradable amphiphilic block copolymer based on methoxy poly(ethylene glycol)-b-poly(5-allyloxy-1,3-dioxan-2-one) (mPEG-b-PATMC) was successfully synthesized in bulk using immobilized porcine pancreas lipase (IPPL) as the catalyst. After thiol-ene "click" reactions occur between thiol group of thioglycolic acid and carbon-carbon double bonds of PATMC segments, the pendent carboxyl-modified copolymer mPEG-b-PATMC-g-SCH2COOH was obtained for high-efficiency loading and controlled release of doxorubicin (DOX) to cancer cells. Both the carboxyl-modified and unmodified copolymers could self-assemble to form nano-sized micelles in aqueous solution, while transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after DOX loading. Compared with the unmodified copolymer, the pendent carboxyl-modified structure in mPEG-b-PATMC-g-SCH2COOH could markedly enhance the drug-loading capacity and entrapment efficiency via the electrostatic interaction. The in vitro release studies showed more sustained drug release behavior of mPEG-b-PATMC-g-SCH2COOH without an initial burst, which could be further adjusted by the conditions of ionic strength and pH. Confocal laser scanning microscopy (CLSM) indicated efficient cellular uptake of DOX delivered by mPEG-b-PATMC-g-SCH2COOH, while MTT assays also demonstrated potent cytotoxic activity against HeLa cells.

Thymine-functionalized amphiphilic biodegradable copolymers for high-efficiency loading and controlled release of methotrexate.

In this study, a novel thymine-functionalized six-membered cyclic carbonate monomer (TAC) was synthesized by the Michael-addition reaction between thymine and acryloyl carbonate (AC). The corresponding functional amphiphilic block copolymer mPEG-b-PTAC was further successfully synthesized by ring-opening polymerization using immobilized porcine pancreas lipase (IPPL) as the catalyst and mPEG as the macroinitiator. Meanwhile, mPEG-b-P(TAC-co-DTC) and mPEG-b-PDTC were also synthesized by the same enzymatic methods for comparison on different TAC contents. The structures of monomer and copolymers were characterized by (1)H-NMR, (13)C-NMR and FTIR. All the amphiphilic block copolymers could self-assemble to form nano-sized micelles in aqueous solution. Transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after MTX loading. (1)H-NMR and FTIR results confirmed the successful formation of multiple hydrogen-bonding interactions between exposed thymine groups of hydrophobic PTAC segments and 2,6-diaminopyridine (DAP) groups of MTX molecules, which resulting in the higher drug loading capacity and the pH-sensitive drug release behavior. MTT assays also indicated lower toxicity of copolymer but higher potent cytotoxic activity of MTX-loaded copolymer against HeLa cells.

Folate-conjugated amphiphilic block copolymers for targeted and efficient delivery of doxorubicin.

In this paper, novel biodegradable amphiphilic block copolymers based on folate-conjugated poly(ethylene glycol)-b-copolycarbonates (FA-PEG-b-P(MAC-co-DTC)) and methoxy poly(ethylene glycol)-b-copolycarbonates (mPEG-b-P(MAC-co-DTC)) were successfully synthesized for targeted and efficient delivery of doxorubicin (DOX) to cancer cells. Immobilized porcine pancreas lipase (IPPL) was employed as the catalyst to perform the ring-opening copolymerization in bulk, while the folate-conjugated poly(ethylene glycol) (FA-PEG) or methoxy poly(ethylene glycol) (mPEG) was used as the initiator. The resulting copolymers, characterized by (1)H NMR and GPC, could self-assemble to form nano-sized micelles in aqueous solution by dialysis method. P(MAC-co-DTC) acted as the hydrophobic core, thereby aggregating hydrophilic PEG chains as the outer shell with FA as targeting ligand located at the surface of the polymeric micelles. Transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after DOX loading. Both the FA-conjugated and non-conjugated block copolymers showed low cellular cytotoxicity. Furthermore, as compared to the non-conjugated copolymers, much more efficient cellular uptake of the FA-conjugated copolymers via FA-receptor-mediated endocytosis could be observed by confocal laser scanning microscopy (CLSM), while MTT assays also demonstrated highly potent cytotoxic activity against HeLa cells.

Crosslinked triblock copolymeric micelle for redox-responsive drug delivery.

In this paper, novel biodegradable amphiphilic triblock copolymer based on methoxy poly(ethylene glycol)-b-poly(ɛ-caprolactone)-b-poly(2-(2-oxo-1,3,2-dioxaphospholoyloxy)ethyl methacrylate) (mPEG-b-PCL-b-PPEMA) was successfully synthesized. After Michael-addition reactions between amine groups of cystamine and carbon-carbon double bonds of PPEMA segments, the crosslinked reduction-sensitive copolymer mPEG-b-PCL-b-PPEMA-SS- was obtained for efficient delivery and controlled release of doxorubicin (DOX) to cancer cells. Both the uncrosslinked and crosslinked copolymers could self-assemble to form nano-sized micelles in aqueous solution, while transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after DOX loading. Meanwhile, (1)H NMR spectra in D2O indicated the formation of a lower mobility core by crosslinking method and a solid-like rigid core via further DOX-loaded. As compared to the uncrosslinked copolymer, the core crosslinking structure in mPEG-b-PCL-b-PPEMA-SS- could improve the micellar stability and enhance the drug loading capacity and entrapment efficiency. The in vitro release studies showed more sustained drug release behavior of crosslinked mPEG-b-PCL-b-PPEMA-SS- which could be accelerated quantitatively in response to the reductive condition similar to intracellular environment. Furthermore, confocal laser scanning microscopy (CLSM) indicated much more efficient cellular uptake of DOX delivered by mPEG-b-PCL-b-PPEMA-SS-, while MTT assays also demonstrated potent cytotoxic activity against HeLa cells.

Amphiphilic polycarbonate conjugates of doxorubicin with pH-sensitive hydrazone linker for controlled release.

Novel amphiphilic polycarbonates-graft-doxorubicin (mPEG-b-P(ATMC-co-DTC)-g-DOX) were successfully designed and synthesized for pH-triggered intercellular drug release in cancer cells. The amphiphilic block copolymer, mPEG-b-P(ATMC-co-DTC), was synthesized in bulk using immobilized porcine pancreas lipase (IPPL) as the catalyst. After allyl epoxidation of ATMC units, DOX was covalently conjugated to the hydrophobic polycarbonates block through a hydrazone linkage. The resulting mPEG-b-P(ATMC-co-DTC)-g-DOX prodrugs could self-assemble to form nano-sized micelles in aqueous solution, while DOX contents in the hydrophobic core were 9.9 and 12.5 wt.%. DOX release rate from the prodrug micelles increased in acidic medium due to the acid-cleavable hydrazone linkage between the DOX and polycarbonates. MTT assays demonstrated that DOX prodrug micelles in this study showed effective cytotoxic effects to HeLa cells. Furthermore, confocal laser scanning microscopy (CLSM) observations also revealed that mPEG-b-P(ATMC-co-DTC)-g-DOX prodrugs could efficiently deliver and release DOX into the nuclei of HeLa cells.