Anticancer Camptothecin-N-Poly(lactic acid) Nanoconjugates with Facile Hydrolysable Linker

Amphiphilic tri- and tetra-block co-polymers combining versatile functionality with facile assembly into cytocompatible nanoparticles

In order for synthetic polymers to find widespread practical application as biomaterials, their syntheses must be easy to perform, utilising freely available building blocks, and should generate products which have no adverse effects on cells or tissue. In addition, it is highly desirable that the synthesis platform for the biomaterials can be adapted to generate polymers with a range of physical properties and macromolecular architectures, and with multiple functional handles to allow derivatisation with 'actives' for sensing or therapy. Here we describe the syntheses of amphiphilic tri- and tetra-block copolymers, using diazabicyclo[5.4.0]undec-5-ene (DBU) as a metal-free catalyst for ring-opening polymerisations of the widely-utilised monomer lactide combined with a functionalised protected cyclic carbonate. These syntheses employed PEGylated macroinitiators with varying chain lengths and architectures, as well as a labile-ester methacrylate initiator, and produced block copolymers with good control over monomer incorporation, molar masses, side-chain and terminal functionality and physico-chemical properties. Regardless of the nature of the initiators, the fidelity of the hydroxyl end group was maintained as confirmed by a second ROP chain extension step, and polymers with acryloyl/methacryloyl termini were able to undergo a second tandem reaction step, in particular thiol-ene click and RAFT polymerisations for the production of hyperbranched materials. Furthermore, the polymer side-chain functionalities could be easily deprotected to yield an active amine which could be subsequently coupled to a drug molecule in good yields. The resultant amphiphilic copolymers formed a range of unimolecular or kinetically-trapped micellar-like nanoparticles in aqueous environments, and the non-cationic polymers were all well-tolerated by MCF-7 breast cancer cells. The rapid and facile route to such highly adaptable polymers, as demonstrated here, offers promise for a range of bio materials applications.

A new, simple, and efficient strategy for the preparation of active antifungal biodegradable materials via ring-opening polymerization of l-lactide with zinc aryloxides

In this work, zinc aryloxides supported by monodentate hydroxybiphenyls [ArOH: ortho-phenylphenol (o-XenOH), meta-phenylphenol (m-XenOH), or para-phenylphenol (p-XenOH] and N,N,N',N'-tetramethylethylenediamine (TMEDA) were used to develop active polymeric materials for antifungal agents for agricultural use. The direct reaction of ligand precursor ArOH with ZnEt2 (1 : 2) in a toluene/TMEDA mixture (1 : 10) afforded a series of three isostructural monomeric compounds, namely [Zn(o-XenO)2(TMEDA)] (1), [Zn(m-XenO)2(TMEDA)] (2), and [Zn(p-XenO)2(TMEDA)] (3). These were characterized by single-crystal X-ray diffraction, and spectroscopic and other analytical methods. The results show that 1-3 are effective initiators for the ring-opening polymerization (ROP) of l-lactide (l-LA) via bifunctional activation of the monomer with Lewis pairs to give polymers terminated with TMEDA and Zn(OAr)2 as the α- and ω-chain ends, respectively. Combinations of ZnEt2 with two molar equivalents of ArOH proligands were used to synthesize polylactides containing fungicide molecules covalently bonded via ester linkers. The ROP of l-LA initiated by these zinc-based systems could be used for the preparation of polyesters with promising antifungal activities.

Self-assisted membrane-penetrating helical polypeptides mediate anti-inflammatory RNAi against myocardial ischemic reperfusion (IR) injury

Aromatically-modified helical polypeptide mediates membrane-penetrating RAGE siRNA delivery toward anti-inflammatory treatment against myocardial IR injury.

Branched polyesters: Preparative strategies and applications

In the last 20years, the availability of precision chemical tools (e.g. controlled/living polymerizations, 'click' reactions) has determined a step change in the complexity of both the macromolecular architecture and the chemical functionality of biodegradable polyesters. A major part in this evolution has been played by the possibilities that controlled macromolecular branching offers in terms of tailored physical/biological performance. This review paper aims to provide an updated overview of preparative techniques that derive hyperbranched, dendritic, comb, grafted polyesters through polycondensation or ring-opening polymerization mechanisms.

Doxorubicin-loaded biodegradable self-assembly zein nanoparticle and its anti-cancer effect: Preparation, in vitro evaluation, and cellular uptake

Cancer is one top leading cause of the deaths worldwide. Various anticancer drugs, which can effectively kill cancer cells, have been developed in the last decade. However, the problem is still about the low therapeutic index of the drugs, which means that the effective dose of drugs will cause cytotoxicity to normal cells. A strategy based on drug nano-encapsulation is applied to achieve an effective anti-cancer therapy. In this study, we use zein, which is an amphiphilic protein, to make the anti-cancer drug nano-encapsulation. Doxorubicin (DOX), a popular anti-cancer drug, is selected as the core drug. The results show that DOX could be successfully encapsulated into zein to form spherical nanoparticles. The encapsulation efficiency and loading efficiency could reach as high as 90.06% and 15.01 mg/g, respectively. The cumulative release result showed a desired pH-responsible release behavior: DOX could be released faster in acidic buffer solutions (pH 5.0 and 6.5) than neutral one (pH 7.4). The effects of the nano-encapsulation on the anti-proliferation of HeLa cells were also examined. It indicated that, compared with free DOX, the DOX-loaded zein nanoparticles (DOX-zein-NPs) had a better effect on cancer cell killing at low DOX concentrations. We also investigated the cellular uptake of DOX-zein-NPs using confocal laser scanning microscopy (CLSM), flow cytometry, and transmission electron microscopy (TEM). And the endocytosis mechanism of DOX-zein-NPs entering into HeLa cells was studied using various endocytosis pathway inhibitors.

Self-defensive nano-assemblies from camptothecin-based antitumor drugs

Camptothecin (CPT)-based drugs always undergo the reversible, pH-dependent lactone ring-opening reaction, yielding the inactive but toxic carboxylate form. Self-assembly strategy provides an effective route for preserving their bio-stability. In this article, nano-sized self-assemblies from CPT-based antitumor drugs were simply built up by directly diluting the stock dimethylsulfoxide solutions of (S)-(+)-CPT, (S)-10-hydroxyl camptothecin and carboxylic CPT with water/phosphate-buffered saline solution. Because of their different molecular structures in A-ring or modification on the 20-OH group, CPT self-assembled into helical nano-ribbons, whereas 10-hydroxycamptothecin and carboxylic CPT self-aggregated into flat nano-ribbons and cylindric nano-rods, respectively. Attractively, the self-assembly of CPT-based drugs could occur within 1 min at a low concentration of 1 × 10⁻⁵M. Adopting the J-type self-aggregation, self-assemblies were stable in aqueous solution and could effectively protect the CPT-based drugs from hydrolysis, which thereby kept their bioactivity for tumor therapy.

Redox-Responsive Self-Assembled Chain-Shattering Polymeric Therapeutics

We report the design and development of redox-responsive chain-shattering polymeric therapeutics (CSPTs). CSPTs were synthesized by condensation polymerization and further modified with poly(ethylene glycol) (PEG) via "Click" reaction. Size-controlled CSPT nanoparticles (NPs) were formed through nanoprecipitation with high drug loading (up to 18%); the particle size increased in a concentration dependent manner. Drug release from particles was well controlled over 48 h upon redox triggering. The anticancer efficacy of the CSPT NPs was validated both in vitro and in vivo.

Biodegradable micelles capable of mannose-mediated targeted drug delivery to cancer cells

A targeted micellar drug delivery system is developed from a biocompatible and biodegradable amphiphilic polyester, poly(Lac-OCA)-b-(poly(Tyr(alkynyl)-OCA)-g-mannose) (PLA-b-(PTA-g-mannose), that is synthesized via controlled ring-opening polymerization of O-carboxyanhydride (OCA) and highly efficient "Click" chemistry. Doxorubicin (DOX), a model lipophilic anticancer drug, can be effectively encapsulated into the micelles, and the mannose moiety allows active targeting of the micelles to cancer cells that specifically express mannose receptors, which thereafter enhances the anticancer efficiency of the drug. Comprised entirely of biodegradable and biocompatible polyesters, this micellar system demonstrates promising potentials for targeted drug delivery and cancer therapy.

Hydrolyzable polyureas bearing hindered urea bonds

Hydrolyzable polymers are widely used materials that have found numerous applications in biomedical, agricultural, plastic, and packaging industrials. They usually contain ester and other hydrolyzable bonds, such as anhydride, acetal, ketal, or imine, in their backbone structures. Here, we report the first design of hydrolyzable polyureas bearing dynamic hindered urea bonds (HUBs) that can reversibly dissociate to bulky amines and isocyanates, the latter of which can be further hydrolyzed by water, driving the equilibrium to facilitate the degradation of polyureas. Polyureas bearing 1-tert-butyl-1-ethylurea bonds that show high dynamicity (high bond dissociation rate), in the form of either linear polymers or cross-linked gels, can be completely degraded by water under mild conditions. Given the simplicity and low cost for the production of polyureas by simply mixing multifunctional bulky amines and isocyanates, the versatility of the structures, and the tunability of the degradation profiles of HUB-bearing polyureas, these materials are potentially of very broad applications.