ROS-Responsive Chalcogen-Containing Polycarbonates for Photodynamic Therapy

Doxorubicin-loaded Polymeric Biotin-PEG-SeSe-PBLA Micelles with surface Binding of Biotin-Mediated Cancer Cell Targeting and Redox-Responsive Drug release for enhanced anticancer efficacy

Biotin receptors are overexpressed in various cancer cell types, essential in tumor development, metabolism, and metastasis. Chemotherapeutic agents may be more effective and have fewer adverse effects if they specifically target the biotin receptors on cancer cells. Polymeric micelles (PMs) with nanoscale size via the EPR effect to accumulate near tumor tissue. We utilized the solvent exchange technique to crate polymeric Biotin-PEG-SeSe-PBLA micelles. This underwent self-assembly to create uniformly dispersed PMs with a hydrodynamic diameter of 81.54 ± 0.23 nm. The resulting PMs characterized by 1HNMR, 13CNMR, FTIR, and Raman spectroscopy. PMs exhibited a high efficacy of Doxorubicin encapsulation (EE) and loading content (DLC), with values of 5.93 wt% and 74.32 %, respectively. DOX@Biotin-PEG-SeSe-PBLA micelles showed optimal DOX release, around 89 % and 74 % in 10 mM glutathione and 0.1 % H2O2, respectively, within 72 hours, in the simulated cancer redox pool. Fascinatingly, the blank Biotin-PEG-SeSe-PBLA micelles did not affect the HaCaT or HeLa cell lines; approximately 85 % of the cells were metabolically active. Contrarily, at a 5 μg/ml concentration, DOX@Biotin-PEG-SeSe-PBLA specifically inhibited the proliferation of roughly 76 % of HeLa cells and 11 % of HaCaT cells. The fluorescence microscopy results demonstrated that biotin-decorated micelles were more successfully internalized by HeLa cells, which overexpress the biotin receptor, than by non-targeted micelles in vitro. In summary, the diselenide-linked Biotin-PEGSeSe-PBLA formed smart PMs that could offer DOX specific to cancer cells with precision and are physiologically durable.

Unleashing the Power of PET-RAFT Polymerization: Journey from Porphyrin-Based Photocatalysts to Combinatorial Technologies and Advanced Bioapplications

The emergence of photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer polymerization (PET-RAFT) not only revolutionized the field of photopolymerization but also accelerated the development of porphyrin-based photocatalysts and their analogues. The continual expansion of the monomer family compatible with PET-RAFT polymerization enhances the range of light radiation that can be harnessed, providing increased flexibility in polymerization processes. Furthermore, the versatility of PET-RAFT polymerization extends beyond its inherent capabilities, enabling its integration with various technologies in diverse fields. This integration holds considerable promise for the advancement of biomaterials with satisfactory bioapplications. As researchers delve deeper into the possibilities afforded by PET-RAFT polymerization, the collaborative efforts of individuals from diverse disciplines will prove invaluable in unleashing its full potential. This Review presents a concise introduction to the fundamental principles of PET-RAFT, outlines the progress in photocatalyst development, highlights its primary applications, and offers insights for future advancements in this technique, paving the way for exciting innovations and applications.

High-Molecular-Weight and Light-Colored Disulfide-Bond-Embedded Polyesters: Accelerated Hydrolysis Triggered by Redox Responsiveness

Disulfide bonds have attracted considerable attention due to their reduction responsiveness, but it is crucial and challenging to prepare disulfide-bond-based polyesters by melt polycondensation. Herein, the inherently poor thermal stability of the S-S bond in melting polycondensation was overcome. Moreover, poly(butylene succinate-co-dithiodipropionate) (PBSDi) with a light color and high molecular weights (Mn values up to 84.7 kg/mol) was obtained. These polyesters can be applied via melt processing with Td,5% > 318 °C. PBSDi10-PBSDi40 shows good crystallizability (crystallinity 56-38%) and compact lamellar thickness (2.9-3.2 nm). Compared with commercial poly(butylene adipate-co-terephthalate) (PBAT), the elevated mechanical and barrier performances of PBSDi make them better packaging materials. For the degradation behavior, the disulfide monomer obviously accelerates the enzyme degradation but has a weaker effect on hydrolysis. In 0.1 mol/L or higher concentrations of H2O2 solutions, the oxidation of disulfide bonds to sulfoxide and sulfone groups can be realized. This process results in a stronger nucleophilic attack, as confirmed by the Fukui function and DFT calculations. Additionally, the greater polarity and hydrophilicity of oxidation products, proved by noncovalent interaction analysis, accelerate the hydrolysis of polyesters. Moreover, glutathione-responsive breakage, from polymers to oligomers, is confirmed by an accelerated decline in molecular weight. Our research offers fresh perspectives on the effective synthesis of the disulfide polyester and lays a solid basis for the creation of high-performance biodegradable polyesters that degrade on demand.

Introducing SuFEx click chemistry into aliphatic polycarbonates: a novel toolbox/platform for post-modification as biomaterials

As a biodegradable and biocompatible biomaterial, aliphatic polycarbonates (APCs) have attracted substantial attention in terms of post-polymerization modification (PPM) for functionalization. A strategy for the introduction of sulfur(VI)-fluoride exchange (SuFEx) click chemistry into APCs for PPM is proposed for the first time in this work. 4'-(Fluorosulfonyl)benzyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (FMC) was designed as a SuFEx clickable cyclic carbonate for APCs via ring-opening polymerization (ROP), and an operational and nontoxic synthetic route was achieved. FMC managed to undergo both ROP and PPM through the SuFEx click chemistry organocatalytically without constraining or antagonizing each other, using 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) as a co-organocatalyst here. Its ROP was systematically investigated, and density functional theory (DFT) calculations were performed to understand the acid-base catalytic mechanism in the anionic ROP. Exploratory investigations into PPM by SuFEx of poly(FMC) were conducted as biomaterials, and the one-pot strategies to achieve both ROP and SuFEx were confirmed.

Room-Temperature Metal-Free Multicomponent Polymerizations of Elemental Selenium toward Stable Alicyclic Poly(oxaselenolane)s with High Refractive Index

Selenium-containing polymers are a group of fascinating functional polymers with unique structures, properties, and applications, which have been developed recently but only with limited examples. The challenges of developing selenium-containing polymers with structural and functional diversity include the lack of economic and safe monomers, lack of efficient and convenient synthetic approaches, and poor stability of selenium-involving covalent bonds. In this work, room-temperature metal-free multicomponent polymerizations (MCPs) of elemental selenium, diisocyanides, and dipropargyl alcohols were developed, and polymers with a selenium-containing aliphatic heterocycle, 1,3-oxaselenolane, were synthesized through these MCPs directly from elemental selenium. The alicyclic poly(oxaselenolane)s enjoyed high yields (up to 93%), high molecular weights (up to 15 600 g/mol), high thermal and chemical stability, good solubility and processability. With the structural design of the poly(oxaselenolane)s and their high selenium contents of up to 33.7 wt %, the refractive indices of their spin-coated thin films could reach 1.8026 at 633 nm and maintain 1.7770 at 1700 nm. It is anticipated that these efficient, convenient, mild, and economic multicomponent polymerizations of elemental selenium can promote the selenium-related polymer chemistry and accelerate the exploration of diversified selenium-containing functional polymer materials.

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.

Engineered bioresponsive nanotherapeutics: recent advances in the treatment of atherosclerosis and ischemic-related disease

Biological stimuli that are present during the pathogenesis of disease have gained considerable interest as a critical element for the design of smart drug delivery systems. Recently, the utilization of biological stimuli-responsive (bioresponsive) nanotheranostic agents to treat atherosclerosis and ischemic-related diseases has demonstrated significant outcomes in preclinical studies. Those diseases share similar hallmarks, including high levels of endogenous reactive oxygen species (ROS), low pH, and high enzyme activity. Interestingly, other relevant biological stimuli such as shear stress, cholesterol, and glutathione have recently been explored as internal stimuli to trigger drug release and some particular actions. In addition, a number of strategies can be proposed to enhance their targeting efficiency, diagnostic properties, and efficacy rate. This review discusses recent advancements in the preclinical studies of bioresponsive nanotherapeutics as diagnostic and therapeutic agents against atherosclerosis and ischemic-related diseases as well as some potential strategies to overcome the current limitations.

Heterotellurium-containing macrocycles towards degradable tellurium-functionalized polymers

We first disclose a facile strategy to synthesize a heterotellurium-containing macrocycle series, and then well-defined degradable poly(telluride-carbonate)s were obtained by ring-opening polymerization.

Stimuli-Responsive Aliphatic Polycarbonate Nanocarriers for Tumor-Targeted Drug Delivery

Nanoparticles based on amphiphilic copolymers with tunable physicochemical properties can be used to encapsulate delicate pharmaceutics while at the same time improving their solubility, stability, pharmacokinetic properties, reducing immune surveillance, or achieving tumor-targeting ability. Those nanocarriers based on biodegradable aliphatic polycarbonates are a particularly promising platform for drug delivery due to flexibility in the design and synthesis of appropriate monomers and copolymers. Current studies in this field focus on the design and the synthesis of new effective carriers of hydrophobic drugs and their release in a controlled manner by exogenous or endogenous factors in tumor-specific regions. Reactive groups present in aliphatic carbonate copolymers, undergo a reaction under the action of a stimulus: e.g., acidic hydrolysis, oxidation, reduction, etc. leading to changes in the morphology of nanoparticles. This allows the release of the drug in a highly controlled manner and induces a desired therapeutic outcome without damaging healthy tissues. The presented review summarizes the current advances in chemistry and methods for designing stimuli-responsive nanocarriers based on aliphatic polycarbonates for controlled drug delivery.

Precise magnetic resonance imaging-guided sonodynamic therapy for drug-resistant bacterial deep infection

The precise treatment of drug-resistant deep bacterial infections remains a huge challenge in clinic. Herein, a polymer-peptide-porphyrin conjugate (PPPC), which can be real-time monitored in infectious site, is developed for accurate and deep sonodynamic therapy (SDT) based on "in vivo self-assembly" strategy. The PPPC contains four moieties, i.e., a hyperbranched polymer backbone, a self-assembled peptide linked with an enzyme-cleavable peptide-poly (ethylene glycol) terminal, a bacterial targeting peptide, and a porphyrin sonosensitizer (MnTCPP) segment. Once PPPC nanoparticles reach the infectious area, the protecting PEG layers are removed due to the over-expressed gelatinase, leading to the secondary assembly into large nanoaggregates and resultant enhanced accumulation of sonosensitizer. The nanoaggregates exhibit enhanced interaction with bacterial membrane and decrease the minimum inhibitory concentration (MIC) significantly. Meanwhile, compared with free MnTCPP, the concentration of which can not be accurately quantified, the accumulation amount of MnTCPP in PPPCs at infectious site can be in situ monitored by magnetic resonance imaging (MRI) using T₁ combined with T₂. When the concentration of PPPC-1 reaches MIC, the drug-resistant bacterial infection area is exposed to ultrasound irradiation, causing the precise and efficient elimination of bacteria. Therefore, the MRI-guided SDT system shows extraordinary tissue penetration depth, drug concentration monitoring, morphology-transformation induced accumulation and improved treatment capacity toward drug-resistant bacteria.

Preparation of ROS-responsive core crosslinked polycarbonate micelles with thioketal linkage

Herein, we prepared novel reactive oxygen species (ROS) responsive core crosslinked (CCL/TK) polycarbonate micelles conveniently by click reaction between amphiphilic diblock copolymer poly(ethylene glycol)-poly(5-methyl-5-propargylxycar-bonyl-1,3-dioxane-2-one) (PEG-PMPC) with pendant alkynyl group and thioketal containing azide derivative bis (2-azidoethyl) 3, 3'- (propane-2, 2-diylbis (sulfanediyl)) dipropanoate (TK-N₃). The CCL/TK micelles were obtained with small size of 146.4 nm, showing excellent stability against dilution and high doxorubicin (DOX) loading. In vitro toxicity tests demonstrated that the obtained CCL/TK micelles have good biocompatibility and low toxicity with cell viability above 95 %. Furthermore, DOX-loaded CCL/TK micelles showed significantly superior toxicity with IC₅₀ values for HeLa and MCF-7 cells about 3.74 μg/mL and 3.91 μg/mL, respectively. Confocal laser scanning microscope (CLSM) and flow cytometry showed excellent internalization efficiency and intracellular drug release of DOX-loaded CCL/TK micelles. The obtained ROS-responsive CCL/TK micelles showed great potential for anticancer drug delivery.

A Novel Synthesis of Poly(Ester-Alt-Selenide)s by Ring-Opening Copolymerization of γ-Selenobutyrolactone and Epoxy Monomer

Ring-opening copolymerization (ROCOP) is an effective means to prepare functionalized polyester. In this work, a type of selenide-containing polyesters with controllable structure, molecular weight, and molecular weight distribution was successfully prepared by ROCOP of γ-selenobutyrolactone and epoxy compounds. The influence of the catalyst, solvent, and reaction temperature on the reaction efficiency was examined. Then, kinetic study was investigated under an optimized condition. The structure of the copolymers was carefully characterized by nuclear magnetic resonance (NMR), 1H NMR, 13C NMR, and 77Se NMR, Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and size exclusion chromatography (SEC). The resulting polymers showed a linear structure with a sequence regulated backbone repeating unit of ester-selenide. On this basis, some typical epoxides were investigated to verify the scope of the polymerization system. Due to the "living"/controlled characteristics of this ROCOP, multiblock, amphiphilic, and stereotactic copolymers could be prepared with a pre-designed structure. As expected, the selenide-containing amphiphilic copolymer could self-assemble to micelles and showed an oxidative response.

Assessing the range of enzymatic and oxidative tunability for biosensor design

Development of multi-functional materials and biosensors that can achieve an in situ response designed by the user is a current need in the biomaterials field, especially in complex biological environments, such as inflammation, where multiple enzymatic and oxidative signals are present. In the past decade, there has been extensive research and development of materials chemistries for detecting and monitoring enzymatic activity, as well as for releasing therapeutic and diagnostic agents in regions undergoing oxidative stress. However, there has been limited development of materials in the context of enzymatic and oxidative triggers together, despite their closely tied and overlapping mechanisms. With research focusing on enzymatically and oxidatively triggered materials separately, these systems may be inadequate in monitoring the complexity of inflammatory environments, thus limiting in vivo translatability and diagnostic accuracy. The intention of this review is to highlight a variety of enzymatically and oxidatively triggered materials chemistries to draw attention to the range of synthetic tunability available for the construction of novel biosensors with a spectrum of programmed responses. We focus our discussion on several types of macromolecular sensors, generally classified by the causative material response driving ultimate signal detection. This includes sensing based on degradative processes, conformational changes, supramolecular assembly/disassembly, and nanomaterial interactions, among others. We see each of these classes providing valuable tools toward coalescing current gaps in the biosensing field regarding specificity, selectivity, sensitivity, and flexibility in application. Additionally, by considering the materials chemistry of enzymatically and oxidatively triggered biomaterials in tandem, we hope to encourage synthesis of new biosensors that capitalize on their synergistic roles and overlapping mechanisms in inflammatory environments for applications in disease diagnosis and monitoring.

Near-Infrared Laser-Triggered, Self-Immolative Smart Polymersomes for in vivo Cancer Therapy

Purpose

Traditional chemotherapy is accompanied by significant side effects, which, in many aspects, limits its treatment efficacy and clinical applications. Herein, we report an oxidative responsive polymersome nanosystem mediated by near infrared (NIR) light which exhibited the combination effect of photodynamic therapy (PDT) and chemotherapy.

Methods

In our study, poly (propylene sulfide)₂₀-bl-poly (ethylene glycol)₁₂ (PPS₂₀-b-PEG₁₂) block copolymer was synthesized and employed to prepare the polymersome. The hydrophobic photosensitizer zinc phthalocyanine (ZnPc) was loaded in the shell and the hydrophilic doxorubicin hydrochloride (DOX·HCl) in the inner aqueous space of the polymersome.

Results

Under the irradiation of 660 nm NIR light, singlet oxygen ¹O₂ molecules were generated from ZnPc to oxidize the neighbouring sulfur atoms on the PPS block which eventually ruptured the intact structure of polymersomes, leading to the release of encapsulated DOX·HCl. The released DOX and the ¹O₂ could achieve a combination effect for cancer therapy if the laser activation and drug release occur at the tumoral sites. In vitro studies confirmed the generation of singlet oxygen and DOX release by NIR irradiation. In vivo studies showed that such a combined PDT-chemotherapy nanosystem could accumulate in A375 tumors efficiently, thus leading to significant inhibition on tumor growth as compared to PDT (PZ group) or chemotherapy alone (DOX group).

Conclusion

In summary, this oxidation-sensitive nanosystem showed excellent anti-tumor effects by synergistic chemophotodynamic therapy, indicating that this novel drug delivery strategy could potentially provide a new means for cancer treatments in clinic.

Leveraging a polycationic polymer to direct tunable loading of an anticancer agent and photosensitizer with opposite charges for chemo-photodynamic therapy

Herein, we reported a primary amine containing polycationic polymer to load an oppositely charged anticancer drug (doxorubicin, DOX) and a photosensitizer (chlorin e6, Ce6) for combinational chemo-photodynamic therapy. The electrostatic interactions as well as other multiple interactions between the polymer and payloads endowed the drug-loaded nanoparticles with excellent stability. Moreover, the electrostatic attraction between the cationic polymer and anionic Ce6 dictated that Ce6 had higher loading efficiency than DOX. DOX showed pH-responsive drug release owing to the increased solubility of protonated DOX and reduced interaction with the partially protonated polymer under acidic conditions. In contrast, Ce6 showed pH-insensitive release because of the smaller change in solubility and the intense interactions between Ce6 and the polymer. Synergistic chemo/photodynamic therapy of 4T1 cancer cells was achieved by light-triggered reactive oxygen species (ROS)-mediated enhanced cellular uptake and effective endo/lysosomal escape of drug-loaded nanoparticles. Our study demonstrated that the polycationic polymer could act as a robust carrier for differential loading and release of oppositely charged cargos for combinational therapy.

An NIR-activated polymeric nanoplatform with ROS- and temperature-sensitivity for combined photothermal therapy and chemotherapy of pancreatic cancer

A functional nanoplatform with ROS- and temperature-sensitivity was reported to achieve combined cancer treatment under NIR stimulation.

Organoselenium chemistry-based polymer synthesis

Novel synthesis of selenium containing polymers with pre-determined structures and applications thereof.

Reactive oxygen species-responsive drug delivery systems for the treatment of neurodegenerative diseases

Neurodegenerative diseases and disorders seriously impact memory and cognition and can become life-threatening. Current medical techniques attempt to combat these detrimental effects mainly through the administration of neuromedicine. However, drug efficacy is limited by rapid dispersal of the drugs to off-target sites while the site of administration is prone to overdose. Many neuropathological conditions are accompanied by excessive reactive oxygen species (ROS) due to the inflammatory response. Accordingly, ROS-responsive drug delivery systems have emerged as a promising solution. To guide intelligent and comprehensive design of ROS-responsive drug delivery systems, this review article discusses the two following topics: (1) the biology of ROS in both healthy and diseased nervous systems and (2) recent developments in ROS-responsive, drug delivery system design. Overall, this review article would assist efforts to make better decisions about designing ROS-responsive, neural drug delivery systems, including the selection of ROS-responsive functional groups.

Near-infrared light-triggered degradable hyaluronic acid hydrogel for on-demand drug release and combined chemo-photodynamic therapy

In this study, an injectable and near-infrared (NIR) light-triggered ROS-degradable hyaluronic acid hydrogel platform was developed as localized delivery vehicle for photosensitizer protophorphyrin IX (PpIX) and anticancer drug doxorubicin (DOX), to achieve superior combined chemo-photodynamic therapy with light-tunable on-demand drug release. The in situ-forming hydrogel fabricated readily via the formation of dynamic covalent acylhydrazone bonds could efficiently prevent severe self-quenching effect of water-insoluble PpIX due to the covalent binding, leading to localized enhanced photodynamic therapy (PDT). Moreover, the extensive ROS generated by the hydrogel under NIR light irradiation could not only realize efficient PDT effect, but also cleave the ROS-cleavable small molecule crosslinker, inducing the desirable degradation of hydrogel and subsequent on-demand DOX release for cascaded chemotherapy. The developed versatile hyaluronic acid hydrogels have tunable properties, excellent biocompatibility, biodegradability and exhibit outstanding therapeutic effects in both in vitro cellular experiments and in vivo antitumor studies.

Redox-Responsive Fluorescent Polycarbonates Based on Selenide for Chemotherapy of Triple-Negative Breast Cancer

Transient increase of reactive oxygen species (ROS) is vital for some physiological processes, whereas the chronic and sustained high ROS level is usually implicated in the inflammatory diseases and cancers. Herein, we report the innovative redox-responsive theranostic micellar nanoparticles that are able to load anticancer drugs through coordination and hydrophobic interaction and to fluorescently monitor the intracellular redox status. The nanoparticles were formed by the amphiphilic block copolymers composed of a PEG segment and a selenide-containing hydrophobic polycarbonate block with a small fraction of coumarin-based chromophore. Under the alternative redox stimulation that might be encountered in the physiological process of some healthy cells, these nanoparticles underwent the reversible changes in size, morphology, and fluorescence intensity. With the assistance of small model compounds, we clarified the chemistry behind these changes, that is, the redox triggered reversible transformation between selenide and selenoxide. Upon the monotonic oxidation similar to the sustained high ROS level of cancer cells, the nanoparticles could be disrupted completely, which was accompanied by the drastic decrease in fluorescence. Cisplatin and paclitaxel were simultaneously coloaded in the nanoparticles with a moderate efficacy, and the coordination between selenide and platinum improved the stability of the drug-loaded nanoparticles against dilution. The naked nanoparticles are cytocompatible, whereas the dual drug-loaded nanoparticles exhibited a concentration dependent and synergistic cytotoxicity to triple-negative breast cancer (TNBC) cells. Of importance, the drug-loaded nanoparticles are much more toxic to TNBC cells than to normal cells due in part to ROS overproduction in the former cell lines.

Recent Advances on Reactive Oxygen Species-Responsive Delivery and Diagnosis System

Reactive oxygen species (ROS) play crucial roles in biological metabolism and intercellular signaling. However, ROS level is dramatically elevated due to abnormal metabolism during multiple pathologies, including neurodegenerative diseases, diabetes, cancer, and premature aging. By taking advantage of the discrepancy of ROS levels between normal and diseased tissues, a variety of ROS-sensitive moieties or linkers have been developed to design ROS-responsive systems for the site-specific delivery of drugs and genes. In this review, we summarized the ROS-responsive chemical structures, mechanisms, and delivery systems, focusing on their current advances for precise drug/gene delivery. In particular, ROS-responsive nanocarriers, prodrugs, and supramolecular hydrogels are summarized in terms of their application for drug/gene delivery, and common strategies to elevate or diminish cellular ROS concentrations, as well as the recent development of ROS-related imaging probes were also discussed.

One-shot synthesis and solution properties of ROS/pH responsive methoxy poly(ethylene glycol)-b-polycarbonate

A one-shot method was employed to synthesize ROS/pH responsive methoxy poly(ethylene glycol)-b-polycarbonate (mPEG-b-poly(MN-co-MSe)) with the selenide and tertiary amine groups situated on the backbone.

One-pot cascade polymerization based on the addition reactions of electrophilic selenium reagents to alkenes

A direct polymerization based on the addition reactions of electrophilic selenium reagents to alkenes was established.

Enzymatic synthesis of selenium-containing amphiphilic aliphatic polycarbonate as an oxidation-responsive drug delivery vehicle

Although functional aliphatic polycarbonates (APCs) have attracted prominent research interest as stimuli-responsive biomaterials, the majority of functional APCs are fabricated by detrimental organometallic catalysts or organo-catalysts. Herein, a facile synthetic strategy based on enzymatic polymerization was developed to construct a selenium-containing amphiphilic aliphatic polycarbonate (mPEG-b-CMP₄₅). Specifically, the selenium in its backbone framework underwent a hydrophobic–hydrophilic transition upon exposure to the abnormal ROS level of the tumor, thus providing a promising platform for ROS-triggered drug release. This amphiphilic mPEG-b-CMP₄₅ efficiently encapsulated doxorubicin (DOX) via self-assembly in aqueous solution and showed an excellent ability to regulate the release of DOX in response to H₂O₂ at biologically relevant concentrations (100 μM). These DOX-loaded nanoparticles could easily be internalized into U87 cells and possess the inherent antitumor properties of DOX, while they exhibited much lower cytotoxicity in normal cells HL-7702. Moreover, in many cases, the introduction of selenium caused high cytotoxicity of the materials, but the cytotoxicity results in HL-7702 cells demonstrated the good biocompatibility of mPEG-b-CMP₄₅. These collective data suggested the potential use of mPEG-b-CMP₄₅ as a biocompatible and smart drug delivery vehicle.

A facile synthetic strategy based on enzymatic polymerization was developed to construct a ROS-responsive polycarbonate served as biocompatible drug vehicle.

Synthesis of main chain sulfur-containing aliphatic polycarbonates by organocatalytic ring-opening polymerization of macrocyclic carbonates

The first application of organocatalysts is reported to achieve highly active and living ring-opening polymerization (ROP) of thioether-based macrocyclic carbonates for preparing well-defined main chain thioether functional APCs.

Tumor microenvironment-responsive nanoparticles for cancer theragnostic applications

BACKGROUND

Cancer is one of the deadliest threats to human health. Abnormal physiochemical conditions and dysregulated biosynthetic intermediates in the tumor microenvironment (TME) play a significant role in modulating cancer cells to evade or defend conventional anti-cancer therapy such as surgery, chemotherapy and radiotherapy. One of the most important challenges in the development of anti-tumor therapy is the successful delivery of therapeutic and imaging agents specifically to solid tumors.

MAIN BODY

The recent progresses in development of TME responsive nanoparticles offers promising strategies for combating cancer by making use of the common attributes of tumor such as acidic and hypoxic microenvironments. In this review, we discussed the prominent strategies utilized in the development of tumor microenvironment-responsive nanoparticles and mode of release of therapeutic cargo.

CONCLUSION

Tumor microenvironment-responsive nanoparticles offers a universal approach for anti-cancer therapy.

ROS-responsive poly(ε-caprolactone) with pendent thioether and selenide motifs

Synthesis and oxidation properties of three chalcogen-containing ROS-responsive poly(ε-caprolactone)s have been reported.