Facile Synthesis of Functional Polytrithiocarbonates from Multicomponent Tandem Polymerizations of CS2, Thiols, and Alkyl Halides

Polytrithiocarbonates have attracted significant attention recently because of their good thermal stability, light refractivity, crystallinity, and mechanical properties; however, the exploration of their structures and functionalities has been limited by their synthetic approaches. Multicomponent polymerization featuring simple monomers, mild conditions, diversified product structures, and high efficiency could provide a powerful and versatile tool to synthesize various polytrithiocarbonates from commercially available monomers. Herein, a robust and efficient multicomponent tandem polymerization (MCTP) of CS2, dithiols, and alkyl halides was developed in DMF with K2CO3 at room temperature in air to synthesize 12 polytrithiocarbonates with diversified and systematically tuned structures, high molecular weights (Mns up to 37900 g/mol), and high yields (up to 93%). Depending on the different polymer backbone structures, amorphous polytrithiocarbonates showed excellent breaking elongations, and crystallinic polytrithiocarbonates possessed a large process temperature window (about 200 °C) and good mechanical performance (σB of 23.6 MPa and εB of 858%), whose tensile strength could be dramatically enhanced to 87.5 MPa after uniaxial extension deformation. The upper critical solution temperature (UCST) in organic solvents, together with nonconventional luminescence, were observed for the crystallinic polytrithiocarbonates, even without any aromatic ring. This efficient, robust, mild, and economic MCTP of CS2 thus opened up an avenue for the facile construction of polytrithiocarbonates with structural diversity, bringing modulable mechanical, thermal, luminescent, and thermal-responsive properties, which would greatly broaden the scope of structures and applications of sulfur-containing polymers.

Multifunctional Polymer Vesicles for Synergistic Antibiotic-Antioxidant Treatment of Bacterial Keratitis

As an acute ophthalmic infection, bacterial keratitis (BK) can lead to severe visual morbidity, such as corneal perforation, intraocular infection, and permanent corneal opacity, if rapid and effective treatments are not available. In addition to eradicating pathogenic bacteria, protecting corneal tissue from oxidative damage and promoting wound healing by relieving inflammation are equally critical for the efficient treatment of BK. Besides, it is very necessary to improve the bioavailability of drugs by enhancing the ocular surface adhesion and corneal permeability. In this investigation, therefore, a synergistic antibiotic-antioxidant treatment of BK was achieved based on multifunctional block copolymer vesicles, within which ciprofloxacin (CIP) was simultaneously encapsulated during the self-assembly. Due to the phenylboronic acid residues in the corona layer, these vesicles exhibited enhanced muco-adhesion, deep corneal epithelial penetration, and bacteria-targeting, which facilitated the drug delivery to corneal bacterial infection sites. Additionally, the abundant thioether moieties in the hydrophobic membrane enabled the vesicles to both have ROS-scavenging capacity and accelerated CIP release at the inflammatory corneal tissue. In vivo experiments on a mice model demonstrated that the multifunctional polymer vesicles achieved efficient treatment of BK, owing to the enhanced corneal adhesion and penetration, bacteria targeting, ROS-triggered CIP release, and the combined antioxidant-antibiotic therapy. This synergistic strategy holds great potential in the treatment of BK and other diseases associated with bacterial infections.

Enhanced anti-metastatic therapy with down-regulation of heparinase expression by ROS-responsive micellar nanoparticles

Metastasis is a major sign of malignant tumors which plays a vital role in cancer-related death. Suppressing metastasis is an important way to improve the survival rate of cancer patients. Herein, multifunctional PEG-LAM-PPS nanoparticles (nPLPs) are fabricated as both nanocarriers and anti-metastatic agents for tumor treatment. In this system, laminarin sulfate (LAM) suppresses metastasis by reducing heparinase and protecting the extracellular matrix; the ROS-sensitive polypropylene sulfide (PPS) improves the release of the loaded drug in the tumor microenvironment. This is the first time that laminarin sulfate has been used as a carrier to inhibit the expression of heparinase and treat melanoma lung metastasis. The blank nanoparticles are excellently safe and showed high anti-metastatic efficacy in melanoma lung metastatic mouse models, reducing metastatic nodules by 60%. They significantly improved the anti-tumor efficacy of the loaded drug doxorubicin, provided ∼33% further reduction of the tumor volume and 50% further reduction of the metastatic nodule number compared with free doxorubicin. Thus, these simple and versatile micellar nanoparticles composed of biocompatible materials offer a promising vehicle for treating invasive solid tumors and metastases.

Transition of Conformation and Solubility in β-Sheet-Structured Poly(l-cysteine)s with Methylthio or Sulfonium Pendants

Poly(l-cysteine)s with methylthio pendants (PMTLCs) were synthesized by ring-opening polymerization of a new l-cysteine-based N-carboxyanhydride. The thioether bonds of PMTLC can be readily oxidized by H₂O₂ yielding water-soluble PMTLC^OX. The methylthio groups can undergo an alkylation reaction using methyl iodide and a subsequent ion-exchange reaction yielding sulfonium-based polypeptides (PPLC-DMS-X, where X = I, BF₄). PPLC-DMS-X showed upper critical solution temperature-type thermo- and oxidation-responsive properties in aqueous solutions. Both PMTLC and PPLC-DMS-X showed oxidation-induced β-sheet to α-helix transitions. The absorbance of PPLC-DMS-I and methyl orange aqueous solution displayed a significant linear correlation with temperature, which makes the sulfonium-based polypeptides good candidates in the field of temperature sensors.

Self-assembly behavior of oligo(ethylene glycol) substituted polycaprolactone homopolymers

In this work, non-ionic amphiphilic oligo(ethylene glycol)-substituted polycaprolactone homopolymers readily self-assembled to form micelles in a polar environment, which allowed the encapsulation of a hydrophobic molecule.

Thermo- and oxidation-sensitive poly(meth)acrylates based on alkyl sulfoxides: dual-responsive homopolymers from one functional group

Alkyl sulfoxide side groups introduce thermo- and oxidation-sensitivity into poly(meth)acrylates, thus realizing new dual-responsive homopolymers based on one functional group.