Diselenium-containing ultrathin polymer nanocapsules for highly efficient targeted drug delivery and combined anticancer effect

Psammaplin A analogues with modified disulfide bond targeting histone deacetylases: Synthesis and biological evaluation

Psammaplin A (PsA), a symmetrical bromotyrosine-derived disulfide marine metabolite, has been reported could inhibit HDAC1/2/3 through its thiol monomer. Inspired by the disuflide bond structure of this marine natural product, we designed and synthesized a series of PsA analogues, in which the disulfide bond of PsA was replaced with diselenide bond or cyclic disulfide/diselenide/selenenylsulfide motifs. We also studied the HDAC inhibition, cell growth inhibition, and apoptosis induction of these PsA analogues. The results showed that, all the synthetic diselenide analogues and cyclic selenenyl sulfide compounds exhibited better antiproferative activity than their counterpart of disulfide analogues. Among the prepared analogues, diselenide analogue P-503 and P-116 significantly increased the ability of inhibiting HDAC6 and induced apoptosis and G2/M cell cycle arrest. However, cyclic selenenylsulfides analogues P-111 lost its HDAC inhibitory ability and exhibited no effect on cell cycle and apoptosis, indicating that the anti-proliferative mechanism of cyclic selenenylsulfides analogues has changed.

Stereoselective Single Step Cyclization to Give Belt-Functionalized Pillar[6]arenes

Two macrocycles were synthesized through cyclization reactions of secondary benzylic alcohols, giving pillar[6]arenes with a methyl substituent at each belt position. These macrocycles form stereoselectively with only the rtctct isomer with alternating up and down orientations of the belt methyl groups definitively identified. Isolated yields were modest (7 and 9%), but the macrocycles are prepared in a single step from either a commercially available alcohol or a very readily prepared precursor. X-ray crystal structures of the macrocycles indicate they have a capsule-like structure, which is far from the conventional pillar shape. Density functional theory calculations reveal that the energy barrier required to obtain the pillar conformation is significantly higher for these belt-functionalized macrocycles than for conventional belt-unfunctionalized pillar[6]arenes.

Covalently bridged pillararene-based polymers: structures, synthesis, and applications

Covalently bridged pillararene-based polymers (CBPPs) are a special class of macrocycle-based polymers in which multiple pillararene monomers are attached to the polymer structures by covalent bonds. Owing to the unique molecular structures including the connection components or the spatial structures, CBPPs have become increasingly popular in applications ranging from environmental science to biomedical science. In this review, CBPPs are divided into three types (linear polymers, grafted polymers, and cross-linked polymers) according to their structural characteristics and described from the perspective of synthesis methods comprehensively. In addition, the applications of CBPPs are presented, including selective adsorption and separation, fluorescence sensing and detection, construction of supramolecular gels, anticancer drug delivery, artificial light-harvesting, catalysis, and others. Finally, the current challenging issues and comprehensive prospects of CBPPs are discussed.

Macrocycle-Surfaced Polymer Nanocapsules: An Emerging Paradigm for Biomedical Applications

In the recent decade, macrocycle-surfaced polymer nanocapsules have been developed and studied as potential drug carriers. In particular, a unique group of these nanocapsules were constructed from a covalently self-assembled polymer network based on several classic macrocycles including cucurbituril, pillararene, and calixarene. The unique structure of these nanocapsules consists of a liquid or solid core and a shell laced with macrocycles in which the macrocycles not only act as the shell matrix of the nanocapsules but also allow further facile, modular functionalization via host-guest interactions with guest-tagged molecules. More interestingly, when a responsive cross-linker was introduced between the macrocycles, the payload inside the nanocapsules could be selectively released in the presence of typical hallmarks of certain diseases, which is of great interest for biomedical applications. In this Topical Review, macrocycle-surfaced polymer nanocapsules derived from covalently self-assembled polymer networks are introduced systemically with a focus on the molecular design and biomedical applications.

Supramolecular Combination Cancer Therapy Based on Macrocyclic Supramolecular Materials

Supramolecular combination therapy adopts supramolecular materials to design intelligent drug delivery systems with different strategies for cancer treatments. Thereinto, macrocyclic supramolecular materials play a crucial role in encapsulating anticancer drugs to improve anticancer efficiency and decrease toxicity towards normal tissue by host-guest interaction. In general, chemotherapy is still common therapy for solid tumors in clinics. However, supramolecular combination therapy can overcome the limitations of the traditional single-drug chemotherapy in the laboratory findings. In this review, we summarized the combination chemotherapy, photothermal chemotherapy, and gene chemotherapy based on macrocyclic supramolecular materials. Finally, the application prospects in supramolecular combination therapy are discussed.

Emerging Roles of Green-Synthesized Chalcogen and Chalcogenide Nanoparticles in Cancer Theranostics

The last few decades have seen an overwhelming increase in the amount of research carried out on the use of inorganic nanoparticles. More fascinating is the tremendous progress made in the use of chalcogen and chalcogenide nanoparticles in cancer theranostics. These nanomaterials, which were initially synthesized through chemical methods, have now been efficiently produced using different plant materials. The paradigm shift towards the biogenic route of nanoparticle synthesis stems from its superior advantages of biosafety, eco-friendliness, and simplicity, among others. Despite a large number of reviews available on inorganic nanoparticle synthesis through green chemistry, there is currently a dearth of information on the green synthesis of chalcogens and chalcogenides for cancer research. Nanoformulations involving chalcogens such as sulfur, selenium, and tellurium and their respective chalcogenides have recently emerged as promising tools in cancer therapeutics and diagnosis. Similar to other inorganic nanoparticles, chalcogens and chalcogenides have been synthesized using plant extracts and their purified biomolecules. In this review, we provide an up-to-date discussion of the recent progress that has been made in the plant-mediated synthesis of chalcogens and chalcogenides with a special focus on their application in cancer theranostics.

Biocompatible Diselenide-Containing Protein Hydrogels with Effective Visible-Light-Initiated Self-Healing Properties

Smart hydrogels are typical functional soft materials, but their functional and mechanical properties are compromised upon micro- or macro-mechanical damage. In contrast, hydrogels with self-healing properties overcome this limitation. Herein, a dual dynamic bind, cross-linked, self-healing protein hydrogel is prepared, based on Schiff base bonds and diselenide bonds. The Schiff base bond is a typical dynamic covalent bond and the diselenide bond is an emerging dynamic covalent bond with a visible light response, which gives the resulting hydrogel a dual response in visible light and a desirable self-healing ability. The diselenide-containing protein hydrogels were biocompatible due to the fact that their main component was protein. In addition, the hydrogels loaded with glucose oxidase (GOx) could be transformed into sols in glucose solution due to the sensitive response of the diselenide bonds to the generated hydrogen peroxide (H2O2) by enzymatic catalysis. This work demonstrated a diselenide-containing protein hydrogel that could efficiently self-heal up to nearly 100% without compromising their mechanical properties under visible light at room temperature.

Recent developments in selenium-containing polymeric micelles: prospective stimuli, drug-release behaviors, and intrinsic anticancer activity

Selenium is capable of forming a dynamic covalent bond with itself and other elements and can undergo metathesis and regeneration reactions under optimum conditions. Its dynamic nature endows selenium-containing polymers with striking sensitivity towards some environmental alterations. In the past decade, several selenium-containing polymers were synthesized and used for the preparation of oxidation-, reduction-, and radiation-responsive nanocarriers. Recently, thioredoxin reductase, sonication, and osmotic pressure triggered the cleavage of Se-Se bonds and swelling or disassembly of nanostructures. Moreover, some selenium-containing nanocarriers form oxidation products such as seleninic acids and acrylates with inherent anticancer activities. Thus, selenium-containing polymers hold promise for the fabrication of ultrasensitive and multifunctional nanocarriers of radiotherapeutic, chemotherapeutic, and immunotherapeutic significance. Herein, we discuss the most recent developments in selenium-containing polymeric micelles in light of their architecture, multiple stimuli-responsive properties, emerging immunomodulatory activities, and future perspectives in the delivery and controlled release of anticancer agents.

Genetic Incorporation of Selenotyrosine Significantly Improves Enzymatic Activity of Agrobacterium radiobacter Phosphotriesterase

Tyrosine plays important roles in many enzymes. To facilitate enzyme design, mechanistic studies and minimize structural perturbation in the active site, here we report the genetic incorporation of a novel unnatural amino acid selenotyrosine (SeHF), which has single-atom replacement in comparison to tyrosine. The arPTE-(Agrobacterium radiobacter Phosphotriesterase) Tyr309SeHF mutant exhibits a significant 12-fold increase in kcat and 3.2-fold enhancement in kcat /KM at pH 7.0. Molecular dynamics simulations show that the SeHF309 mutation results in a conformational switch which opens up the product release pocket and increases the product release rate, thereby elevating the overall enzyme activity. Significant improvement of the catalytic efficiency at neutral pH by single unnatural amino acid (UAA) mutation broadens the application of this enzyme, and provides valuable insights to the mechanism. Our method represents a new approach for designing enzymes with enhanced activity.

Template-Free Self-Assembly of Two-Dimensional Polymers into Nano/Microstructured Materials

In the past few decades, enormous efforts have been made to synthesize covalent polymer nano/microstructured materials with specific morphologies, due to the relationship between their structures and functions. Up to now, the formation of most of these structures often requires either templates or preorganization in order to construct a specific structure before, and then the subsequent removal of previous templates to form a desired structure, on account of the lack of “self-error-correcting” properties of reversible interactions in polymers. The above processes are time-consuming and tedious. A template-free, self-assembled strategy as a “bottom-up” route to fabricate well-defined nano/microstructures remains a challenge. Herein, we introduce the recent progress in template-free, self-assembled nano/microstructures formed by covalent two-dimensional (2D) polymers, such as polymer capsules, polymer films, polymer tubes and polymer rings.

Metal-Organic Framework-Based Stimuli-Responsive Polymers

Metal-organic framework (MOF) based stimuli-responsive polymers (coordination polymers) exhibit reversible phase-transition behavior and demonstrate attractive properties that are capable of altering physical and/or chemical properties upon exposure to external stimuli, including pH, temperature, ions, etc., in a dynamic fashion. Thus, their conformational change can be imitated by the adsorption/desorption of target analytes (guest molecules), temperature or pressure changes, and electromagnetic field manipulation. MOF-based stimuli responsive polymers have received great attention due to their advanced optical properties and variety of applications. Herein, we summarized some recent progress on MOF-based stimuli-responsive polymers (SRPs) classified by physical and chemical responsiveness, including temperature, pressure, electricity, pH, metal ions, gases, alcohol and multi-targets.

Stimuli-responsive supramolecular nano-systems based on pillar[n]arenes and their related applications

Stimuli-responsive supramolecular nano-systems (SRNS) have been a trending interdisciplinary research area due to the responsiveness upon appropriate stimuli, which makes SRNS very attractive in multiple fields where precise control is vital.