Copolycarbonates Based on a Bicyclic Diol Derived from Citric Acid and Flexible 1,4-Cyclohexanedimethanol: From Synthesis to Properties.

Octahydro-2,5-pentalenediol (OPD), is a compelling citric acid-based bicyclic diol with excellent rigidity and thermal stability. Herein, a series of copolycarbonates (co-PCs) were synthesized, starting from OPD, 1,4-cyclohexanedimethanol (CHDM), and diphenyl carbonate (DPC). All polycarbonates are amorphous with glass transition temperatures increased when increasing the content in OPD units. Dynamic mechanical analysis (DMA) revealed the sub Tg ß-relaxations at low temperatures originating from the CHDM conformational transition, indicative of the possibility of impact-resistance. Morphological analysis of the fracture surfaces revealed the toughening mechanism under tensile was shear yielding of the matrix triggered by internal cavitation. The incorporation of OPD steadily increased the Young's modulus, from 482 to 757 MPa, with the OPD fraction increased from 0 to 30 mol %. As the OPD content further increased, a "ductile-to-brittle" transition occurred due to the low number-average molecular weight (Mn) and the low entangled strand density (high entanglement molecular weight).

Copolymerization of Natural Camphor-Derived Rigid Diol with Various Dicarboxylic Acids: Access to Biobased Polyesters with Various Properties.

In this work, alicyclic (1R,3S)-1,2,2-trimethylcyclopentane-1,3-dimethanol (TCDM), derived from natural camphor, was copolymerized with linear α,ω-diacids, terephthalic acid (TPA), and 2,5-furandicarboxylic acid (FDCA), affording a series of polyesters with functional properties. 2D NMR spectroscopy revealed that the stereoconfiguration of TCDM was preserved after polymerization. The TCDM polyester based on TPA showed high thermostability, high Tg value (115 °C), high modulus (1.3 GPa), and high ultimate strength (29.8 MPa). The TCDM polyester based on 1,4-succinic acid exhibited excellent ductility and resilience. Lastly, the rigidity analysis based on van Krevelen's group contribution method, coupled with the comparisons between TCDM- and sugar-based polyesters, confirmed that TCDM is a highly reactive and rigid diol. Results indicate that TCDM polyesters are suitable for a wide range of applications, including hot-filled containers and transparent packaging materials. This work addresses some critical needs for high performance biopolymers such as achieving high Tg values, high thermostability, and high transparency.

Construction of an Antibacterial Membrane Based on Dopamine and Polyethylenimine Cross-Linked Graphene Oxide.

Bacterial infections have been considered to be one of the greatest threats to human health. In this study, a covalently cross-linked GO membrane was fabricated through vacuum-assisted filtration self-assembly after being consequentially functionalized with dopamine (GO-PDA) and branched polyethylenimine (GO-PDA-PEI). The characteristics of GO, GO-PDA, and GO-PDA-PEI membranes were confirmed by X-ray diffraction, Fourier transform infrared measurements, scanning electron microscopy images, static water contact angle measurements, etc. The GO-PDA-PEI membrane showed extraordinary stability, compared with GO and GO-PDA, confirmed by ultrasonication treatment. Notably, the GO-PDA-PEI membrane exhibited excellent antibacterial efficiency for both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli (more than 99%) upon irradiation by a 795 nm near-infrared (NIR) laser. Interestingly, the GO-PDA-PEI membrane can be recycled, that is, the photothermal effect, as well as the antibacterial activity of the GO-PDA-PEI membrane, remained the same after 5-time recycling. Hence, the proposed system has great potential for future design of recyclable, highly stable, superior bacteriostatic membrane materials.

A multifunctional polymeric gene delivery system for circumventing biological barriers.

Aiming to circumvent the pre-defined obstacles in the journey of gene transportation, we attempt to compile a number of functional components into a tandem tri-copolymeric material. Herein, a ß-cyclodextrin-functionalized poly(glycerol methacrylate) (PG) segment and a quaternary amine-functionalized poly[(2-acryloyl)-ethyl-(p-boronic acid pinacol ester benzyl)diethylammonium bromide] (BP) segment are attached to complex DNA to formulate a nanoscaled delivery system based on electrostatic interactions. The formulated polyplex is strengthened by a hydrophobic poly[2-(5,5-dimethyl-1,3-dioxan-2-yloxy)ethyl acrylate] (PDM) segment, affording improved complex stability. To retrieve the polyplex from entrapment by acidic and digestive endo/lysosomes, light-stimulated ROS-producing 4,4'-(1,2-diphenylethene-1,2-diyl)bis(1,4-phenylene)diboronic acid (TPE) is installed in the cavities of cyclodextrin. Upon light irradiation, TPE is triggered to produce abundant ROS, not only committing disruption of the endo/lysosome membrane for polyplex escape from the entrapment but also inducing the transformation of the positively charged BP to become negatively charged. This charge conversion behavior, together with the transformation of PDM to be hydrophilic and responsive to an acidic endosome pH gradient (pH 5.0) is envisioned to induce the dissociation of the electrostatically-assembled polyplex, thereby facilitating the release of the DNA payload for the subsequent transcription machinery. This strategically-tailored and easily synthesized tandem tri-copolymer exhibits excellent gene expression activity and provides a facile response to endogenous and exogenous stimuli for active gene expression.

Construction of Bovine Serum Albumin/AIE-Based Quaternary Complexes for Efficient Gene Transfection.

High transfection efficiency and superior cell imaging are required for cationic polymers-based gene delivery system to afford high therapeutic effect but its high toxicity and unstable cell imaging are easily ignored. In this study, cationic amino poly(glycerol methacrylate) derivative (PGMA-EDA) is used to incorporate bovine serum albumin (BSA) and aggregation-induced emission (AIE) molecular (tetraphenylethylene derivatives, TPE) as an efficient carrier for gene transfection and intracellular imaging. The obtained polymer/pDNA-TPE/BSA (PDTB) quaternary nanoparticles (NPs) not only exhibit efficient gene transfection but also show excellent biocompatibility. After inclusion of TPE/BSA (TB) NPs, BSA promoted dissociation of the complexes upon being protonated and the lipophilic TPE-reduced endosomal membrane stability, which enhanced endosomal escape of pDNA payload, finally resulting in an excellent gene transfection. On the other hand, less positive surface charge of PDTB NPs than that of the binary PD complexes, as well as the addition of biocompatible BSA, both factors contribute to the improved cell viability. Moreover, the AIE feature of TPE compared to aggregation-caused quenching character of conventional fluorophores enables the complex with stably tracking the delivery of pDNA into cancer cells. Therefore, the newly developed PDTB complexes may be a promising candidate vector for traceable, safe, and effective gene delivery.

Construction of coumarin-based cross-linked micelles with pH responsive hydrazone bond and tumor targeting moiety.

It is still a major challenge for targeted cancer chemotherapy to design a stable biocompatible micellar drug delivery system. To address this dilemma, novel responsive cross-linked micelles (x-micelles) based on polyurethane with photo-responsive coumarin derivatives and pH-responsive hydrazone groups were synthesized. The polymers could be self-assembled into micelles using a typical and facile way. The x-micelles were stable at physiological conditions after UV light induced cross-linking, and can be disassociated under acidic condition. The drug loading content (DLC) and the encapsulation efficiency (EE) of the obtained x-micelles (15.2% and 60.8% respectively) were higher than those of micelles (9.8% and 39.2% respectively), and the DOX release rate of x-micelles was also improved. For targeted therapy, folic acid (FA) was then conjugated to x-micelles, resulting in x-micelles-FA. Cellular viability experiments show that both x-micelles and micelles had a low cytotoxicity and good biocompatibility of up to 1000 µg mL-1, and DOX-loaded x-micelles-FA and x-micelles exhibited half-maximal inhibitory concentration (IC50) values of 1.17 and 2.40 µg mL-1, respectively, to HeLa cells, but have lower cytotoxicity to L929 cells. The pH-responsive x-micelles-FA exhibited superior extracellular stability but activated intracellular drug release. We have demonstrated that the polyurethane with UV- and pH-responsive properties as a novel platform for tumor-targeting drug delivery.