Controlled synthesis and characterizations of amphiphilic poly[(R,S)-3-hydroxybutyrate]-poly(ethylene glycol)-poly[(R,S)-3-hydroxybutyrate] triblock copolymers

Supramolecular Polycations with a Linear-Star Architecture Containing Hydrophobic Poly[(R,S)-3-hydroxybutyrate]: Formation of DNA Micelleplexes Coated with Apolipoprotein E3 for Blood-Brain Barrier Penetrating Gene Delivery

A novel blood-brain barrier (BBB)-penetrating supramolecular gene delivery system was developed utilizing a host-guest block-building strategy to systematically screen and optimize various block compositions. Linear poly(ethylene glycol) (PEG) was coupled with hydrophobic poly[(R,S)-β-hydroxybutyrate] (PHB) blocks of varying lengths with an adamantyl (Ad) end, giving the PEG-PHB-Ad guest polymers, which were complexed with the cationic 4-arm star-shaped β-cyclodextrin-poly(2-dimethylaminoethyl methacrylate) (βCD-pDMAEMA) host polymer, resulting in the formation of linear-star pseudoblock PEG-PHB-Ad/βCD-pDMAEMA copolymers. These amphiphilic supramolecular copolymers were thoroughly characterized and assessed for the formation of DNA micelleplex nanoparticles as a gene delivery system. Through a rational selection process, an optimal host-guest configuration was identified, considering critical factors such as cytotoxicity, gene transfection efficiency, serum stability, cellular uptake, and hemolytic activity. The optimized host-guest copolymer was subsequently coated with the targeting protein apolipoprotein E3 (ApoE3), endowing it with BBB-penetrating capabilities, which was validated through an in vitro BBB transwell model.

Shell-Sheddable Micelles Based on Poly(ethylene glycol)-hydrazone-poly[R,S]-3-hydroxybutyrate Copolymer Loaded with 8-Hydroxyquinoline Glycoconjugates as a Dual Tumor-Targeting Drug Delivery System

The development of selective delivery of anticancer drugs into tumor tissues to avoid systemic toxicity is a crucial challenge in cancer therapy. In this context, we evaluated the efficacy of a combination of nanocarrier pH-sensitivity and glycoconjugation of encapsulated drugs, since both vectors take advantage of the tumor-specific Warburg effect. Herein, we synthesized biodegradable diblock copolymer, a poly(ethylene glycol)-hydrazone linkage-poly[R,S]-3-hydroxybutyrate, which could further self-assemble into micelles with a diameter of ~55 nm. The hydrazone bond was incorporated between two copolymer blocks under an acidic pH, causing the shell-shedding of micelles which results in the drug's release. The micelles were stable at pH 7.4, but decompose in acidic pH, as stated by DLS studies. The copolymer was used as a nanocarrier for 8-hydroxyquinoline glucose and galactose conjugates as well as doxorubicin, and exhibited pH-dependent drug release behavior. In vitro cytotoxicity, apoptosis, and life cycle assays studies of blank and drug-loaded micelles were performed on Normal Human Dermal Fibroblasts-Neonatal (NHDF-Neo), colon carcinoma (HCT-116), and breast cancer (MCF-7) for 24, 48, and 72 h. A lack of toxicity of blank micelles was demonstrated, whereas the glycoconjugates-loaded micelles revealed enhanced selectivity to inhibit the proliferation of cancer cells. The strategy of combining pH-responsive nanocarriers with glycoconjugation of the drug molecule provides an alternative to the modus operandi of designing multi-stimuli nanocarriers to increase the selectivity of anticancer therapy.

Controlling injectability and in vivo stability of thermogelling copolymers for delivery of yttrium-90 through intra-tumoral injection for potential brachytherapy

Intra-tumoral injection of radiopharmaceuticals such as yttrium-90 (⁹⁰Y) or phosphorus-32 (³²P) is an important route for brachytherapy in unresectable solid tumors such as locally advanced hepatocellular carcinoma. However, the injected radiopharmaceuticals can potentially leak out from the tumor site due to high intra-tumoral pressure. In this study, we demonstrated the use of thermogelling copolymers that can be injected into tumor and subsequently solidify as hydrogels within the tumor that can potentially overcome the above problem. To this end, a series of thermogelling polyurethane copolymers with varying compositions were designed and synthesized from Pluronic F127, poly(3-hydroxylbutyrate), and poly(propylene glycol), which were characterized in terms of their molecular structures, compositions, phase diagrams, rheological properties, and injectability and body temperature stability in vitro and in vivo. The analyses of our data elucidated the injectability of the copolymer solutions at low temperatures, and the stability of the hydrogels at the body temperature. This provided the basis on which we could identify one copolymer with balanced composition as the most suitable candidate for intra-tumoral injection and for prevention of the leakage. Finally, the injectability and in vivo stability of the copolymer solution and hydrogel loaded with ⁹⁰Y were further demonstrated in a mouse tumor model, and the in vivo biodistribution of ⁹⁰Y showed that the radionuclide could be retained at the tumor site, indicating that the ⁹⁰Y-loaded copolymer has a great potential for tumor radio-brachytherapy.

Water soluble polyhydroxyalkanoates: future materials for therapeutic applications

Polyhydroxyalkanoates (PHAs) are excellent candidate biomaterials due to their exceptional biodegradability and biocompatibility. However, PHAs need to have tunable hydrophilicity, chemical functionalities, and appropriate hydrolytic stability to expand their therapeutic applications towards more advanced areas. In this Tutorial Review, we present the most recent progress in the synthetic strategies of PHA-based water soluble polymers, including the functionalisation of PHAs with polar functional groups and the block/graft copolymerization of PHAs with hydrophilic components in various polymeric architectures. These chemically modified water soluble PHAs have significant impact on materials engineering and show great value in the fulfilment of smart biomaterials in emerging areas. The applications of water soluble PHAs in controlled drug release, cancer therapy, DNA/siRNA delivery and tissue engineering in new aspects are discussed. In addition, water soluble PHA monomer production will be briefly introduced, with emphasis on its bio-significance in medical physiology and the therapeutic effect in the treatment of diseases.

Polyester-based (bio)degradable polymers as environmentally friendly materials for sustainable development

This review focuses on the polyesters such as polylactide and polyhydroxyalkonoates, as well as polyamides produced from renewable resources, which are currently among the most promising (bio)degradable polymers. Synthetic pathways, favourable properties and utilisation (most important applications) of these attractive polymer families are outlined. Environmental impact and in particular (bio)degradation of aliphatic polyesters, polyamides and related copolymer structures are described in view of the potential applications in various fields.

Synthesis, characterization, biodegradability and biocompatibility of a temperature-sensitive PBLA-PEG-PBLA hydrogel as protein delivery system with low critical gelation concentration

Temperature-sensitive hydrogels were designed using a series of A-B-A triblock copolymers consisting of poly (ethylene glycol) (PEG) with different molecular weights as the hydrophilic block B and poly (β-butyrolactone-co-lactic acid)(PBLA) with varying block lengths and composition as the hydrophobic block A. The triblock copolymers were synthesized by ring-opening polymerization (ROP) of β-BL and LA in bulk using PEG as an initiator and Sn(Oct)2 as the catalyst. Their chemical structure and molecular characteristics were determined by NMR, GPC and DSC, and the relationship between structure and phase behaviors in aqueous solutions was investigated as well. It was found that the phase behaviors in aqueous solutions including critical micelle concentration (CMC), sol-gel-sedimentation phase transition temperature, gel window width and critical gelation concentration (CGC) are largely dependent on the molecular weight and block length ratio of PEG/PBLA. Most importantly, they show a very low CGC ranging from 4 to 8 wt% because of the introduction of β-BL. Furthermore, the biodegradability and biocompatibility of the hydrogels were evaluated. Finally, lysozyme as a model protein was used to evaluate the ability to deliver protein drugs in a sustained release manner and biologically active form. All results demonstrated that the temperature-sensitive in situ forming hydrogel has a promising potential as sustained delivery system for protein drugs.

Polyrotaxanes for applications in life science and biotechnology

Due to their low cytotoxicity, controllable size, and unique architecture, cyclodextrin (CD)-based polyrotaxanes and polypseudorotaxanes have inspired interesting exploitation as novel biomaterials. This review will update the recent progress in the studies on the structures of polyrotaxanes and polypseudorotaxanes based on different CDs and polymers, followed by summarizing their potential applications in life science and biotechnology, such as drug delivery, gene delivery, and tissue engineering. CD-based biodegradable polypseudorotaxane hydrogels could be used as promising injectable drug delivery systems for sustained and controlled drug release. Polyrotaxanes with drug or ligand-conjugated CDs threaded on polymer chain with biodegradable end group could be useful for controlled and multivalent targeting delivery. Cationic polyrotaxanes consisting of multiple oligoethylenimine-grafted CDs threaded on a block copolymer chain were attractive non-viral gene carries due to the strong DNA-binding ability, low cytotoxicity, and high gene transfection efficiency. Cytocleavable end caps were also introduced in the polyrotaxane systems in order to ensure efficient endosomal escape for intracellular trafficking of DNA. Finally, hydrolyzable polyrotaxane hydrogels with cross-linked α-CDs could be a desirable scaffold for cartilage and bone tissue engineering.

Modeling of charged amphiphilic copolymer stars near hydrophobic surfaces

Numerical self-consistent field theory has been applied to amphiphilic copolyelectrolyte stars in the solution and at interfaces both in one- and two-gradient coordinate systems. Our focus is on polymer stars for which the solvent is poor for the short blocks in the center and good for the longer charged chain parts at the periphery of the star. Both in solution as well as near an interface, the structure of the core is influenced by the hydrophobic interactions that tend to form a compact globule with size Rc and the forces exerted by the charged peripheral chain parts that like to expand the core. When the distance H of the center of the star to the surface becomes smaller than the total size R, the interaction force becomes significant; it is positive for Rc<H<R, and rather suddenly becomes strongly attractive at shorter distances when the core can adsorb. Hence, the adsorption as well as the desorption of stars involves the passing of an activation barrier. Details of this barrier are important for a rational design of polymer stars that are of use to modify surface properties.