Construction of hyperbranched and pH-responsive polymeric nanocarriers by yne-phenol click-reaction for tumor synergistic chemotherapy

In past decades, to improve the chemotherapeutic efficiency and reduce the systemic toxicity of small molecule anti-cancer drugs, polymer-based drug delivery systems (DDSs) have attracted great attention for tumor treatment due to their remarkable biocompatibility and responsive degradation in tumor microenvironment (TME). Herein, we developed a kind of pH-responsive and degradable hyperbranched polymeric nanocarriers via yne-phenol click-reaction of resveratrol (RSV) with bifunctional n-butyl dipropiolate (BDP) for efficient doxorubicin (DOX) delivery. The natural product RSV with three phenol groups has excellent antioxidant activity and synergetic enhancement for some anticancer drugs such as DOX. RSV tends to attack the alkynyl groups on BDP by nucleophilic addition in the presence of base as catalyst to afford hyperbranched polyprodrug (denoted as RB). PEGylated RB (termed as RBP) were further synthesized to improve the water solubility and prolong blood circulation by the click reaction of propiolate-terminated RB with amino terminated poly(ethylene glycol) (PEG-NH₂). Interestingly, the RBP have high DOX loading ratio (∼58.6 %) at neutral pH, but the vinyl-ether bonds in RB could break down at low pH conditions such as acidic TME (extracellular pH∼6.8, endosomes and lysosomes pH∼5.0) that leading to the targeting release of DOX and RSV. Therefore, the developed RBP@DOX nanoparticles exhibited high kill efficiency to tumor cells and slight damage to normal cells due to the effective delivery and release of DOX and RSV in tumor sites and the synergistic enhancement effect of two drugs.

Metal-Free Catalysts for the Polymerization of Alkynyl-Based Monomers

Novel polymerizations based on alkyne monomers are becoming a powerful tool to construct polymers with unique structures and advanced functions in the areas of polymer and material sciences, and scientists have been attracted to develop a variety of novel polymerizations in recent decades. Therein, catalytic systems play an indispensable role in the influence of polymerization efficiencies and the performances of the resultant polymers. Concerning the shortcomings of metallic catalysts, much of the recent research focus has been on metal-free polymerization systems. In this paper, metal-free catalysts are classified and the corresponding polymerizations are reviewed, including organobase-catalyzed polymerizations, Lewis-acid-catalyzed polymerizations, as well as catalyst-free polymerizations. Moreover, the challenges and perspectives in this area are also briefly discussed.

Organobase-catalysed hydroxyl–yne click polymerization

An efficient organobase (DABCO)-catalysed hydroxyl–yne click polymerization is successfully developed under mild conditions.

Preparation of hyperbranched polymers by oxa-Michael addition polymerization

Hyperbranched polymers with high molecular weights were synthesized by t-BuP₂-catalyzed oxa-Michael addition polymerization of trifunctional hydroxyl and diacrylate monomers.

Transition metal-free thiol–yne click polymerization toward Z-stereoregular poly(vinylene sulfide)s

An efficient K₃PO₄-mediated thiol–yne click polymerization was established, and regio- and stereoregular poly(vinylene sulfide)s with Z-isomers were produced.

Thiol-yne Click Polymerization

Thiol-yne click polymerization (TYCP) is one of the most significant synthetic techniques for artificial polymers, due to its simplicity, efficiency, and functionality tolerance. In nature, it is a classic nucleophilic addition reaction and a step-growth polymerization, which can be initiated or accelerated in the presence of free-radicals, amines, and transition metals, respectively. Its rate is greatly influenced by the structures (i.e., their electrophilicity and steric hindrance) of the used thiols and/or alkynes. With aliphatic monomers being used as feeding materials, the topological architectures (such as linear, branching, and cross-linked network, etc.) and available functional groups (such as hydroxyl, carboxyl, amino, and epoxy groups, and so on) can be facilely tailored via altering the chemical structure and feeding order. In contrast, for aromatic monomers, mono-addition occurs only during the process of thiol-yne click reaction, leading exclusively to linear poly(vinyl thioether)s. These sulfur-containing polymers synthesized by TYCP are promising to be widely utilized as high refractive index materials, photovoltaic materials, drug-delivery vehicles, biomaterials, and hybrid materials, etc.

Recent advances in alkyne-based click polymerizations

The recent progress in alkyne-based click polymerizations and their application in the preparation of new functional polymers are summarized. The challenges and opportunities in this area are also briefly discussed.

Hyperbranched polymers from A2 + B3 strategy: recent advances in description and control of fine topology

Recent advances in the fine topology regulation of hyperbranched polymers from an A₂ + B₃ strategy were presented from the perspectives of topology description and architecture control.

Functional polyurethane–urea coatings from sulfur rich hyperbranched polymers and an evaluation of their anticorrosion and optical properties

Solvent free, one pot, multistep synthesis of sulfur rich hyperbranched polyols (SHBPs). SHBPs yielded excellent corrosion resistant, transparent polyurethane–urea coatings.

Cu(i)-Catalyzed amino-yne click polymerization

The first example of Cu(i)-catalyzed regio-specific and stereo-selective amino-yne click polymerization was established.

Sequential Michael addition thiol–ene and radical-mediated thiol–ene reactions in one-pot produced sequence-ordered polymers

Sequential Michael addition-based thiol–ene and free radical mediated thiol–ene reactions for preparing sequence-ordered polymers are reported for the first time.

Solution processible hyperbranched inverse-vulcanized polymers as new cathode materials in Li–S batteries

Highly soluble inverse-vulcanized hyperbranched polymers were synthesized as cathode-active materials in Li–S batteries.

One-pot approach to synthesize hyperbranched poly(thiol–ether amine) (hPtEA) through sequential “thiol–ene” and “epoxy–amine” click reactions

We demonstrated a one-pot approach to synthesize hyperbranched poly(thiol–ether amine) (hPtEA) through sequential “thiol–ene” and “epoxy–amine” click reactions, both of which were well traced using in situ¹H-NMR spectra.

The electrophilic effect of thiol groups on thiol–yne thermal click polymerization for hyperbranched polythioether

The significant effect of the electrophilicity of the thiol groups on thiol–yne click polymerization was found and well demonstrated.

Hyperbranched polymers: advances from synthesis to applications

This review summarizes the advances in hyperbranched polymers from the viewpoint of structure, click synthesis and functionalization towards their applications in the last decade.

Topological analysis and intramolecular cyclic feature evaluation of polymers derived from Am + Bn step-growth polymerization

We presented new and convenient evaluation strategies for intramolecular cyclic features of polymers derived from A_m + B_n step-growth polymerization.

ROMP (co)polymers with pendent alkyne side groups: post-polymerization modification employing thiol–yne and CuAAC coupling chemistries

The synthesis of a series of copolymers via ring-opening metathesis polymerization (ROMP) containing pendent trimethylsilyl-protected alkyne functional groups is described.

Efficient functionalization of oxide-free silicon(111) surfaces: thiol-yne versus thiol-ene click chemistry

Thiol-yne click (TYC) chemistry was utilized as a copper-free click reaction for the modification of alkyne-terminated monolayers on oxide-free Si(111) surfaces, and the results were compared with the analogous thiol-ene click (TEC) chemistry. A wide range of thiols such as 9-fluorenylmethoxy-carbonyl cysteine, thio-β-d-glucose tetraacetate, thioacetic acid, thioglycerol, thioglycolic acid, and 1H,1H,2H,2H-perfluorodecanethiol was immobilized using TYC under photochemical conditions, and all modified surfaces were characterized by static water contact angle measurements, X-ray photoelectron spectroscopy (including a simulation thereof by density functional calculations), and infrared absorption reflection spectroscopy. Surface-bound TYC proceeds with an efficiency of up to 1.5 thiols per alkyne group. This high surface coverage proceeds without oxidizing the Si surface. TYC yielded consistently higher surface coverages than TEC, due to double addition of thiols to alkyne-terminated monolayers. This also allows for the sequential and highly efficient attachment of two different thiols onto an alkyne-terminated monolayer.