Synthesis of PDMS-μ-PCL Miktoarm Star Copolymers by Combinations (Є) of Styrenics-Assisted Atom Transfer Radical Coupling and Ring-Opening Polymerization and Study of the Self-Assembled Nanostructures

Due to their diverse and unique physical properties, miktoarm star copolymers (μ-SCPs) have garnered significant attention. In our study, we employed α-monobomoisobutyryl-terminated polydimethylsiloxane (PDMS-Br) to carry out styrenics-assisted atom transfer radical coupling (SA ATRC) in the presence of 4-vinylbenzyl alcohol (VBA) at 0 °C. By achieving high coupling efficiency (χc = 0.95), we obtained mid-chain functionalized PDMS-VBAm-PDMS polymers with benzylic alcohols. Interestingly, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis revealed the insertion of only two VBA coupling agents (m = 2). Subsequently, the PDMS-VBA2-PDMS products underwent mid-chain extensions using ε-caprolactone (ε-CL) through ring-opening polymerization (ROP) with an efficient organo-catalyst at 40 °C, resulting in the synthesis of novel (PDMS)2-μ-(PCL)2 μ-SCPs. Eventually, novel (PDMS)2-μ-(PCL)2 μ-SCPs were obtained. The obtained PDMS-μ-PCL μ-SCPs were further subjected to examination of their solid-state self-assembly through small-angle X-ray scattering (SAXS) experiments. Notably, various nanostructures, including lamellae and hexagonally packed cylinders, were observed with a periodic size of approximately 15 nm. As a result, we successfully developed a simple and effective reaction combination (Є) strategy (i.e., SA ATRC-Є-ROP) for the synthesis of well-defined PDMS-μ-PCL μ-SCPs. This approach may open up new possibilities for fabricating nanostructures from siloxane-based materials.

Unimolecular micelles from star-shaped block polymers by photocontrolled BIT-RDRP for PTT/PDT synergistic therapy

Unimolecular micelles (UIMs) exhibit promising potential in the precise diagnosis and accurate treatment of tumor tissues, a pressing problem in the field of medical treatment, because of their perfect stability in the complex and variable microenvironment. In this study, porphyrin-based four-armed star-shaped block polymers with narrow molar mass dispersity (Đ = 1.34) were facilely prepared by photocontrolled bromine-iodine transformation reversible-deactivation radical polymerization (BIT-RDRP). A photothermal conversion dye, ketocyanine, was covalently linked onto the PEG and then introduced into the polymers through a "grafting onto" strategy to obtain polymeric nanomaterial, THPP-4PMMA-b-4P(PEGMA-co-APMA)@NIR-800, with dual PTT/PDT function. The resulting polymers could form monodispersed UIMs in the water below critical aggregation concentration, meanwhile maintaining the capacities of singlet oxygen release and photothermal conversion. Importantly, the UIMs displayed excellent biocompatibility while exerting superior PTT and/or PDT therapeutic effects under the irradiation of specific wavelengths of light, according to in vitro cellular experiments, which is expected to become a new hot spot for cancer therapy and anti-tumor research. Overall, stable and powerful UIMs with dual PTT/PDT function is provided, which are expected to be competitive candidates in cancer therapy.

Synthesis of enzyme-responsive theranostic amphiphilic conjugated bottlebrush copolymers for enhanced anticancer drug delivery

Synthesis of polyfluorene (PF) based theranostic amphiphilic copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for promoted intracellular drug release and enhanced cancer therapy has been rarely reported likely due to the lack of efficient synthetic approaches to integrate these desirable properties. In this work, we recorded the successful preparation of well-defined theranostic amphiliphilic bottlebrush copolymers composing of fluorescent backbone of PF and tunable enzyme-degradable side chains of polytyrosine (PTyr) and POEGMA by integrating Suzuki coupling, NCA ROP and ATRP techniques. Notably, the resulting copolymer, PF₂₅-g-(PTyr₂₆-b-(POEGMA₂₈)₂ (P₄) with two branched POEGMA brushes tethered to one PTyr termini for each unit could form steady unimolecular micelles with higher fluorescence quantum yield of 18.3% in aqueous and greater entrapment efficiency (EE) of 91.0% for DOX ascribed to the efficient π-π stacking interactions between PTyr blocks and drug molecules and the unique structure of branched hydrophilic brushes with a moderate chain length. DOX@P₄ micelles revealed visualization of intracellular trafficking and accelerated drug release due to the enzyme-triggered degradation of PTyr blocks with proteinase K and subsequent deshielding of POEGMA corona for micelle destruction. In vitro and In vivo animal study further verified the intensive therapeutic efficiency with attenuated systematic toxicity. Taken together, we provided a universal strategy toward multifunctional polymeric delivery vehicles based on conjugated PF and biocompatible and degradable polypeptide by integratied Suzuki coupling and NCA ROP, and identified the branched structure of hydrophilic brushes for better performance of bottlebrush copolymers-based micelles for drug delivery applications. STATEMENT OF SIGNIFICANCE: Synthesis of polyfluorene (PF)-based theranostic amphiphilic copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for promoted intracellular drug release and enhanced cancer therapy has been rarely reported likely due to the lack of efficient synthetic approaches to integrate these desirable properties. We reported herein successful preparation of enzyme-responsive theranostic amphiliphilic bottlebrush copolymers with simultaneously high drug loading efficiency and tumor microenvironment-specific responsiveness for enhanced chemotherapy in vivo. This study therefore not only developed a universal strategy for the construction of multifunction polymeric vehicles based on the conjugated polymer of PF and degradable polypeptide by integrated Suzuki coupling and NCA ROP, but also emphasized the better stability of micelles endowed by the branched hydrophilic brushes than linear ones.

PEGylated dendritic polyurethane as unimolecular micelles for tumor chemotherapy: Effect of molecular architecture

Unimolecular micelles have attracted intense interests as drug carriers for tumor chemotherapy owing to their superior stability in comparison with the self-assembled supramolecular ones. Among them, the dendritic polymers with the polar frameworks could favour the loading of chemotherapeutic drugs rather than the hyperbranched polymers via radical polymerization, by enhancing the interaction with drugs. While the tedious synthesis procedure for dendritic polymers could be simplified with the construction principle on urethane chemistry. Here, the PEGylated dendritic polyurethanes, Ph-DPU_Gly-PEG and Ph-DPU_TEA-PEG, were designed with glycerol or triethanolamine as monomer, respectively. The effect of the molecular architecture of the Ph-DPU-PEGs unimolecular micelles on the controlled drug releasing performance was compared. It was found that the Ph-DPU_TEA-PEG with tertiary amine as branching points could efficiently endow the pH-triggered drug release, due to its protonation.

Facile synthesis of PEGylated dendritic polyurethane as unimolecular micelles for ultrasound-triggered localized drug delivery

PEGylated dendritic polyurethane was designed via a facile one-pot method as unimolecular micelles for ultrasound-triggered localized drug delivery.

Synthesis of micrometer-sized poly(vinyl acetate) particles through microsuspension iodine transfer polymerization: effect of iodine species in a water medium

Schematic of the behaviors of iodine species in the microsuspension polymerization of vinyl acetate (VAc) in an aqueous medium.