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Degradable Controlled-Release Polymers and Polymeric Nanoparticles: Mechanisms of Controlling Drug Release

This review is focused on the chemical design and synthesis of polymer-based drug delivery systems, in particular with stimuli-responsive nanoplatforms for cancer treatment. We provide a brief description of the properties, synthesis and advantages of amphiphilic block copolymers, including polyether-polyester and polyether-polyanhydride. As for stimuli-responsive polymers, we detail the recent innovative techniques for constructing smarter, more precise and optimally tuned nanocarriers that release drug in the disease site. This review is presented in the context of polymer science research, with special attention focused on the tailor-made polymers containing specific chemical functionalities. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3525–3550

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/pola.28252

Polymer‐based drug delivery systems for cancer treatment

α-Lipoic Acid in Soluplus® Polymeric Nanomicelles for Ocular Treatment of Diabetes-Associated Corneal Diseases

Construction of redox/pH dual stimuli-responsive PEGylated polymeric micelles for intracellular doxorubicin delivery in liver cancer

Bioinspired materials have received substantial attention across biomedical, biological, and drug delivery research because of their high biocompatibility and lower toxicity compared with synthetic materials. Bile acids, well-established biomimetic biomolecules, have been reported with respect to their potential applications as carriers of drugs or imaging contrast agents and, most importantly, as oral absorption enhancers. This review introduced the potential mechanisms involved in the oral absorption of bile acids and their derivatives and further focused on the intelligent applications of bile acids or modified bile acids that respond to biological cues as potential oral absorption enhancers for peptides and macromolecular drugs. Our investigations via the modifications of bile acids with various linkers have demonstrated their effects on the degree of oral absorption. Furthermore, we summarized the reports regarding the development of bile acid formulations for the oral delivery of optical imaging contrast agents for GI tract imaging, as well as anticancer drug delivery. Our opinions regarding the utilization of bile acids for biological and biomedical applications provide clear and concise guidance to investigators with respect to the merits and demerits of bile acid use and the selection of appropriate bile acids based on the requirements for improved biomedical applications.

Design and strategies for bile acid mediated therapy and imaging

Reduction responsive biodegradable core-cross-linked micelles are developed form lipoic acid (LA) and cholic acid (CA) decorated poly(ethylene glycol)-b-poly(L-glutamic acid) (PEG-pGlu(EDA-LA)-CA) block copolymers and investigated for intracellular doxorubicin (DOX) release. The amphiphilic polymers can self-assemble into nano-sized core–shell micelles that are easily cross-linked in the presence of a catalytic amount of dithiothreitol (DTT). The cross-linked micelles (CLM) show excellent stability against extensive dilution and high salt concentration but rapid dissociation and drug release in reductive environments. Confocal laser scanning microscopy further demonstrates that DOX was delivered and released into the nuclei of HeLa cells following 8 h incubation with DOX-loaded CLM. MTT assays reveal that DOX-loaded CLM had similar anti-tumor activity to non-cross-linked micelles (NCLM) for HeLa cells following 48 h incubation, while blank micelles were practically nontoxic up to a tested concentration of 1.0 mg mL−1. These reduction responsive core-cross-linked micelles have great potential for drug delivery in cancer chemotherapy.

Disulfide cross-linked cholic-acid modified PEG–poly(amino acid) block copolymer micelles for controlled drug delivery of doxorubicin

Reversibly shell cross-linked micelles based on a lipoic acid (LA) decorated triblock copolymer poly(ethylene glycol)-b-poly(γ-benzyl-L-glutamate)-b-poly(L-phenylalanine) (PEG–PGlu(EDA–LA)–PPhe) have been developed for active loading and efficient intracellular delivery of DOX. The triblock copolymer was synthesized through consecutive ring-opening polymerization of cyclic monomers γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and L-phenylalanine N-carboxyanhydride (Phe-NCA) using amino-terminated poly(ethylene glycol) (PEG–NH2) as macroinitiator, followed by conjugation with LA for reversible cross-linking. The amphiphilic polymer was self-assembled to core shell corona micelles, which could be further crosslinked in the presence of a catalytic amount of dithiothreitol (DTT) in phosphate buffer (pH 7.4) to form shell-cross-linking micelles (SCLM). The SCLM showed excellent stability under physiological conditions but rapid dissociation and drug release in reductive environments mimicking those of the cytoplasm and the cell nucleus. Confocal laser scanning microscopy further demonstrated that DOX was delivered and released into the nuclei of HeLa cells following 12 h incubation with DOX-loaded SCLM. MTT assays revealed that DOX-loaded SCLM had similar anti-tumor activity as non-cross-linked micelles (NCLM) for HeLa cells following 48 h incubation. PEG–PGlu(EDA–LA)–PPhe micelles displayed low cytotoxicity up to a concentration of 1.0 mg mL−1. These biodegradable reversibly shell-cross-linked micelles provide a promising platform for intelligent intracellular drug delivery in clinical chemotherapy.

Reversibly cross-linked poly(ethylene glycol)–poly(amino acid)s copolymer micelles: a promising approach to overcome the extracellular stability versus intracellular drug release challenge

The invention relates to preparation and application of a reducing sensitive nano-micelle, belonging to preparation and application of an amphiphilic block polymer. A hydrophilic section and a hydrophobic section of the amphiphilic block polymer are connected with each other by a reducing responsive sulfur-sulfur bond; the nano-micelle is formed by self-assembling; the reducing sensitive nano-micelle consists of a shell and an inner core, wherein the shell is a hydrophilic polymer, and the inner core is a hydrophobic polymer; the hydrophilic section of the amphiphilic block polymer is polyphosphate, the hydrophobic section of the amphiphilic block polymer is poly(benzyl glutamate), and the hydrophilic section and the hydrophobic section of the amphiphilic block polymer are connected with each other by the reducing responsive sulfur-sulfur bond. The reducing sensitive nano-micelle has the advantages that the drug-loaded nano-micelle is difficult to dissociate outside the cells or in the blood, so that the drug encapsulated in the nano-micelle is enabled to be stable; once the nano-micelle enters the cancer cell, the sulfur-sulfur bond can be disconnected by glutathione which is a reducing matter in the cell, so that the nano-micelle is rapidly dissociated, the anti-cancer drug encapsulated in the nano-micelle can be rapidly and effectively released out, and an effective treatment effect is achieved; the reducing sensitive nano-micelle overcomes the defects that the drug is easy to leak in vivo, low in transport efficiency, slow in intracellular release speed, and the like.

Preparation and application of reducing sensitive nano-micelle

The invention discloses a synthesis method and use of a cholic acid-modified polyamino acid block copolymer. A hydrophilic chain of the block copolymer is polyethylene glycol, a hydrophobic chain of the block copolymer is polyamino acid, the tail end of the polyamino acid is modified through micromolecular cholic acid, the side chain of the polyamino acid is a lipoyl group, and lipoic acid and an amino group of hydrophobic polyamino acid undergo a reaction to produce an amido bond. Through crosslinking of a self-assembled nanometer micelle of the cholic acid-modified polyamino acid block copolymer, a stable crosslinked reduction-sensitive polymer nanometer micelle is obtained so that the nanometer micelle is not easily damaged in vitro and in blood and nanometer micelle-coated drug stability is guaranteed. When the nanometer micelle enters a cancer cell, the nanometer micelle can be fast decrosslinked and dissociated and the coated drug can be fast released and produce high efficiency treatment effects. The cholic acid-modified polyamino acid block copolymer solves the problems of early release of a drug in vivo, low carrying efficiency and a slow release rate in cells.

Synthesis method and use of cholic acid-modified polyamino acid block copolymer

The invention discloses a preparation method and use of a thioctic acid-modified polyethylene glycol-polyaminoacid amphiphilic triblock copolymer. A hydrophilic chain of the amphipathic triblock polymer is polyethylene glycol, a middle hydrophobic chain segment of the amphipathic triblock polymer is poly(benzyl glutamate), a tail hydrophobic chain segment of the amphipathic triblock polymer is polyphenylalanine and the side chain of the middle chain segment is modified through thioctic acid. The amphipathic triblock polymer is self-assembled in water to form a polymer nanometer micelle with polyethylene glycol as an outer crown, thioctic acid-modified poly(benzyl glutamate) as a middle shell and polyphenylalanine as an inner core. Through crosslinking of the nanometer micelle, the stable reduction-sensitive shell crosslinked nanometer micelle is obtained so that the nanometer micelle is not easily dissociated in vitro and in blood and thus stability of a nanometer micelle-coated drug is guaranteed. When the nanometer micelle enters a tumor cell, the nanometer micelle can be fast crosslinked and dissociated so that the drug can be fast released and produces high treatment effects. The amphipathic triblock polymer solves the problems of drug leakage in vivo, low conveying efficiency and slow release in cells.

Preparation method and use of thioctic acid-modified polyethylene glycol-polyaminoacid block copolymer

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