New Synthetic Methodologies for Amphiphilic Multiblock Copolymers of Ethylene Glycol and Propylene Sulfide

O/S Exchange Reaction in Synthesizing Sulfur-Containing Polymers

Using carbon disulfide (CS2) and carbonyl sulfide (COS) as sulfur-containing and one-carbon feedstocks to make value-added products is paramount for both pure and applied chemistry and environmental science. One of the practical strategies is to copolymerize these bulk chemicals with epoxides to produce sulfur-containing polymers. This approach contributes to improving the sustainability of polymer manufacturing, provides highly desired functional polymer materials, and has attracted much attention. However, these copolymerizations invariably exhibit the intensely complicated chemistry of O/S exchange reaction, leading to sulfur-containing polymers with diverse architectures. As the understanding of O/S exchange continues to deepen, recent efforts have guided significant advances in the synthesis of CS2- and COS-based polymers. This review examines the O/S exchange chemistry and summarizes the recent progress in this field to promote the further advance of synthesizing sulfur-containing polymers from CS2 and COS.

Drug Integrating Amphiphilic Nano-Assemblies: 2. Spatiotemporal Distribution within Inflammation Sites

The need for chronic systemic immunosuppression, which is associated with unavoidable side-effects, greatly limits the applicability of allogeneic cell transplantation for regenerative medicine applications including pancreatic islet cell transplantation to restore insulin production in type 1 diabetes (T1D). Cell transplantation in confined sites enables the localized delivery of anti-inflammatory and immunomodulatory drugs to prevent graft loss by innate and adaptive immunity, providing an opportunity to achieve local effects while minimizing unwanted systemic side effects. Nanoparticles can provide the means to achieve the needed localized and sustained drug delivery either by graft targeting or co-implantation. Here, we evaluated the potential of our versatile platform of drug-integrating amphiphilic nanomaterial assemblies (DIANAs) for targeted drug delivery to an inflamed site model relevant for islet transplantation. We tested either passive targeting of intravenous administered spherical nanomicelles (nMIC; 20-25 nm diameter) or co-implantation of elongated nanofibrils (nFIB; 5 nm diameter and >1 μm length). To assess the ability of nMIC and nFIB to target an inflamed graft site, we used a lipophilic fluorescent cargo (DiD and DiR) and evaluated the in vivo biodistribution and cellular uptake in the graft site and other organs, including draining and non-draining lymph nodes, after systemic administration (nMIC) and/or graft co-transplantation (nFIB) in mice. Localized inflammation was generated either by using an LPS injection or by using biomaterial-coated islet-like bead implantation in the subcutaneous site. A cell transplant inflammation model was used as well to test nMIC- and nFIB-targeted biodistribution. We found that nMIC can reach the inflamed site after systemic administration, while nFIB remains localized for several days after co-implantation. We confirmed that DIANAs are taken up by different immune cell populations responsible for graft inflammation. Therefore, DIANA is a useful approach for targeted and/or localized delivery of immunomodulatory drugs to decrease innate and adaptive immune responses that cause graft loss after transplantation of therapeutic cells.

Dual stimuli-responsive and sustained drug delivery NanoSensoGel formulation for prevention of cisplatin-induced ototoxicity

Cisplatin (CisPt)-induced ototoxicity (CIO) is delineated as a consequence of CisPt-induced intracellular generation of reactive oxygen species (ROS) which can be circumvented by Bucillamine (BUC; an antioxidant drug with sulfhydryl groups) and Diltiazem (DLT, L-type calcium channel blocker). However, its effective accumulation in the Organ of Corti and cell cytoplasm is desired. Therefore, a biocompatible BUC- and DLT-nanoparticles (NPs)-impregnated dual stimuli-responsive formulation (NanoSensoGel) presented here with ROS- and thermo-responsive properties for the sustained and receptive delivery of drugs. The ROS-responsive polypropylene sulfide- methyl polyethylene glycol-2000 (PPS-mPEG2000) polymer was rationally designed, synthesized, and characterized to fabricate BUC- and DLT-loaded PPS-mPEG2000-NPs (BUC- and DLT-NPs). The fabricated BUC- and DLT-NPs showed efficient cellular uptake, intracellular delivery, ROS responsiveness, and cytoprotective effect which was characterized using cellular internalization, intracellular ROS, mitochondrial superoxide, and Caspase 3/7 assays on the House Ear Institute-Organ of Corti-1 (HEI-OC1) cells. The composite NanoSensoGel (i.e., ROS-responsive BUC- and DLT-NPs suspended in the thermo-responsive hydrogel) present in a sol state at room temperature and turned to gel above 33°C, which could be essential for retaining the formulation at the target site for long-term release. The NanoSensoGel showed sustained release of BUC and DLT following Fickian release diffusion kinetics. Overall, a novel NanoSensoGel formulation developed in this study has demonstrated its great potential in delivering therapeutics in the inner ear for prophylactic treatment of CIO, and associated hearing loss.

Tuning the Envelope Structure of Enzyme Nanoreactors for In Vivo Detoxification of Organophosphates

Encapsulated phosphotriesterase nanoreactors show their efficacy in the prophylaxis and post-exposure treatment of poisoning by paraoxon. A new enzyme nanoreactor (E-nRs) containing an evolved multiple mutant (L72C/Y97F/Y99F/W263V/I280T) of Saccharolobus solfataricus phosphotriesterase (PTE) for in vivo detoxification of organophosphorous compounds (OP) was made. A comparison of nanoreactors made of three- and di-block copolymers was carried out. Two types of morphology nanoreactors made of di-block copolymers were prepared and characterized as spherical micelles and polymersomes with sizes of 40 nm and 100 nm, respectively. The polymer concentrations were varied from 0.1 to 0.5% (w/w) and enzyme concentrations were varied from 2.5 to 12.5 μM. In vivo experiments using E-nRs of diameter 106 nm, polydispersity 0.17, zeta-potential -8.3 mV, and loading capacity 15% showed that the detoxification efficacy against paraoxon was improved: the LD50 shift was 23.7xLD50 for prophylaxis and 8xLD50 for post-exposure treatment without behavioral alteration or functional physiological changes up to one month after injection. The pharmacokinetic profiles of i.v.-injected E-nRs made of three- and di-block copolymers were similar to the profiles of the injected free enzyme, suggesting partial enzyme encapsulation. Indeed, ELISA and Western blot analyses showed that animals developed an immune response against the enzyme. However, animals that received several injections did not develop iatrogenic symptoms.

Dendritic peptide-conjugated polymeric nanovectors for non-toxic delivery of plasmid DNA and enhanced non-viral transfection of immune cells

Plasmid DNA (pDNA) transfection is advantageous for gene therapies requiring larger genetic elements, including "all-in-one" CRISPR/Cas9 plasmids, but is limited by toxicity as well as poor intracellular release and transfection efficiency in immune cell populations. Here, we developed a synthetic non-viral gene delivery platform composed of poly(ethylene glycol)-b-poly(propylene sulfide) copolymers linked to a cationic dendritic peptide (DP) via a reduceable bond, PEG-b-PPS-ss-DP (PPDP). A library of self-assembling PPDP polymers was synthesized and screened to identify optimal constructs capable of transfecting macrophages with small (pCMV-DsRed, 4.6 kb) and large (pL-CRISPR.EFS.tRFP, 11.7 kb) plasmids. The optimized PPDP construct transfected macrophages, fibroblasts, dendritic cells, and T cells more efficiently and with less toxicity than a commercial Lipo2K reagent, regardless of pDNA size and under standard culture conditions in the presence of serum. The PPDP technology described herein is a stimuli-responsive polymeric nanovector that can be leveraged to meet diverse challenges in gene delivery.

Enzyme Nanoreactor for In Vivo Detoxification of Organophosphates

A nanoreactor containing an evolved mutant of Saccharolobus solfataricus phosphotriesterase (L72C/Y97F/Y99F/W263V/I280T) as a catalytic bioscavenger was made for detoxification of organophosphates. This nanoreactor intended for treatment of organophosphate poisoning was studied against paraoxon (POX). Nanoreactors were low polydispersity polymersomes containing a high concentration of enzyme (20 μM). The polyethylene glycol-polypropylene sulfide membrane allowed for penetration of POX and exit of hydrolysis products. In vitro simulations under second order conditions showed that 1 μM enzyme inactivates 5 μM POX in less than 10 s. LD₅₀-shift experiments of POX-challenged mice through intraperitoneal (i.p.) and subcutaneous (s.c.) injections showed that intravenous administration of nanoreactors (1.6 nmol enzyme) protected against 7 × LD₅₀ i.p. in prophylaxis and 3.3 × LD₅₀ i.p. in post-exposure treatment. For mice s.c.-challenged, LD₅₀ shifts were more pronounced: 16.6 × LD₅₀ in prophylaxis and 9.8 × LD₅₀ in post-exposure treatment. Rotarod tests showed that transitory impaired neuromuscular functions of challenged mice were restored the day of experiments. No deterioration was observed in the following days and weeks. The high therapeutic index provided by prophylactic administration of enzyme nanoreactors suggests that no other drugs are needed for protection against acute POX toxicity. For post-exposure treatment, co-administration of classical drugs would certainly have beneficial effects against transient incapacitation.

Versatility of Hydrogels: From Synthetic Strategies, Classification, and Properties to Biomedical Applications

Hydrogels are three-dimensional, cross-linked, and supramolecular networks that can absorb significant volumes of water. Hydrogels are one of the most promising biomaterials in the biological and biomedical fields, thanks to their hydrophilic properties, biocompatibility, and wide therapeutic potential. Owing to their nontoxic nature and safe use, they are widely accepted for various biomedical applications such as wound dressing, controlled drug delivery, bone regeneration, tissue engineering, biosensors, and artificial contact lenses. Herein, this review comprises different synthetic strategies for hydrogels and their chemical/physical characteristics, and various analytical, optical, and spectroscopic tools for their characterization are discussed. A range of synthetic approaches is also covered for the synthesis and design of hydrogels. It will also cover biomedical applications such as bone regeneration, tissue engineering, and drug delivery. This review addressed the fundamental, general, and applied features of hydrogels in order to facilitate undergraduates, graduates, biomedical students, and researchers in a variety of domains.

Reactive Oxygen Species (ROS)-Responsive Biomaterials for the Treatment of Bone-Related Diseases

Reactive oxygen species (ROS) are the key signaling molecules in many physiological signs of progress and are associated with almost all diseases, such as atherosclerosis, aging, and cancer. Bone is a specific connective tissue consisting of cells, fibers, and mineralized extracellular components, and its quality changes with aging and disease. Growing evidence indicated that overproduced ROS accumulation may disrupt cellular homeostasis in the progress of bone modeling and remodeling, leading to bone metabolic disease. Thus, ROS-responsive biomaterials have attracted great interest from many researchers as promising strategies to realize drug release or targeted therapy for bone-related diseases. Herein, we endeavor to introduce the role of ROS in the bone microenvironment, summarize the mechanism and development of ROS-responsive biomaterials, and their completion and potential for future therapy of bone-related diseases.

RC. Facile Synthesis of Epoxide-co-Propylene Sulphide Polymers with Compositional and Architectural Control

We present a facile method to produce propylene sulphide (PS) homopolymers up to 100 kg/mol and PS – epoxide statistical, block, and ABA copolymers using inexpensive and versatile thio-aluminium (SAl)...

Polymers from S-vinyl monomers: reactivities and properties

This review summarises the work of several decades on the polymerisation of S-vinyl monomers, ranging from the early reports of suitable polymerisation techniques for these monomers to their recent renaissance in various applications.

Thioether-Based Polymeric Micelles with Fine-Tuned Oxidation Sensitivities for Chemotherapeutic Drug Delivery

Oxidation-sensitive drug delivery systems (DDSs) have attracted attention due to the potential to improve efficacy and safety of chemotherapeutics. These systems are designed to release the payload in response to oxidative stress conditions, which are associated with many types of cancer. Despite extensive research on the development of oxidation-sensitive DDS, the lack of selectivity toward cancer cells over healthy cells remains a challenge. Here, we report the design and characterization of polymeric micelles containing thioether groups with varying oxidation sensitivities within the micellar core, which become hydrophilic upon thioether oxidation, leading to destabilization of the micellar structure. We first used the thioether model compounds, 3-methylthiopropylamide (TPAM), thiomorpholine amide (TMAM), and 4-(methylthio)benzylamide (TPhAM) to investigate the effect of the chemical structures of the thioethers on the oxidation by hydrogen peroxide (H₂O₂). TPAM shows the fastest oxidation, followed by TMAM and TPhAM, showing that the oxidation reaction of thioethers can be modulated by changing the substituent groups bound to the sulfur atom. We next prepared micelles containing these different thioether groups within the core (TP, TM, and TPh micelles). The micelles containing the thioether groups with a higher oxidation sensitivity were destabilized by H₂O₂ at a lower concentration. Micelle destabilization was also tested in human liver cancer (HepG2) cells and human umbilical vein endothelial cells (HUVECs). The TP micelles having the highest oxidation sensitivity were destabilized in both HepG2 cells and HUVECs, while the TPh micelles, which showed the lowest reactivity toward H₂O₂, were stable in these cell lines. The TM micelles possessing a moderate oxidation sensitivity were destabilized in HepG2 cells but were stable in HUVECs. Furthermore, the micelles were loaded with doxorubicin (Dox) to evaluate their potential in drug delivery applications. Among the micelles, the TM micelles loaded with Dox showed the enhanced relative toxicity in HepG2 cells over HUVECs. Therefore, our approach to fine-tune the oxidation sensitivity of the micelles has potential for improving therapeutic efficacy and safety of drugs in cancer treatment.

Pi-stacking Enhances Stability, Scalability of Formation, Control over Flexibility and Circulation Time of Polymeric Filaments

Self-assembling filomicelles (FM) are of great interest to nanomedicine due to their structural flexibility, extensive systemic circulation time, and amenability to unique "cylinder-to-sphere" morphological transitions. However, current fabrication techniques for FM self-assembly are highly variable and difficult to scale. Here, we demonstrate that tetrablock copolymers composed of poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) diblocks linked by a pi-stacking perylene bisimide (PBI) moiety permit rapid, scalable, and facile assembly of FM via the flash nanoprecipitation (FNP) method. Co-assembling the tetrablocks and PEG-b-PPS diblocks at different molar ratios resulted in mixed PBI-containing FM (mPBI-FM) with tunable length and flexibility. The flexibility of mPBI-FM can be optimized to decrease uptake by macrophages in vivo, leading to increased circulation time versus (-)PBI-FM without PBI tetrablocks after intravenous administration in mice. While PEG-b-PPS diblocks form FM within a narrow range of hydrophilic weight fractions, incorporation of pi-stacking PBI groups expanded this range to increase favorability of FM assembly. Furthermore, the aggregation-dependent fluorescence of PBI shifted during oxidation-induced "cylinder-to-sphere" transitions of mPBI-FM into micelles, resulting in a distinct emission wavelength for filamentous versus spherical nanostructures. Thus, incorporation of pi-stacking allows for rapid, scalable assembly of FM with tunable flexibility and stability for theranostic and nanomedicine applications.

Insights into oxidative stress in bone tissue and novel challenges for biomaterials

The presence of Reactive Oxygen Species (ROS) in bone can influence resident cells behaviour as well as the extra-cellular matrix composition and the tissue architecture. Aging, in addition to excessive overloads, unbalanced diet, smoking, predisposing genetic factors, lead to an increase of ROS and, if it is accompanied with an inappropriate production of scavengers, promotes the generation of oxidative stress that encourages bone catabolism. Furthermore, bone injuries can be triggered by numerous events such as road and sports accidents or tumour resection. Although bone tissue possesses a well-known repair and regeneration capacity, these mechanisms are inefficient in repairing large size defects and bone grafts are often necessary. ROS play a fundamental role in response after the implant introduction and can influence its success. This review provides insights on the mechanisms of oxidative stress generated by an implant in vivo and suitable ways for its modulation. The local delivery of active molecules, such as polyphenols, enhanced bone biomaterial integration evidencing that the management of the oxidative stress is a target for the effectiveness of an implant. Polyphenols have been widely used in medicine for cardiovascular, neurodegenerative, bone disorders and cancer, thanks to their antioxidant and anti-inflammatory properties. In addition, the perspective of new smart biomaterials and molecular medicine for the oxidative stress modulation in a programmable way, by the use of ROS responsive materials or by the targeting of selective molecular pathways involved in ROS generation, will be analysed and discussed critically.

Therapeutic nanoreactors for detoxification of xenobiotics: Concepts, challenges and biotechnological trends with special emphasis to organophosphate bioscavenging

The introduction of enzyme nanoreactors in medicine is relatively new. However, this technology has already been experimentally successful in cancer treatments, struggle against toxicity of reactive oxygen species in inflammatory processes, detoxification of drugs and xenobiotics, and correction of metabolic and genetic defects by using encapsulated enzymes, acting in single or cascade reactions. Biomolecules, e.g. enzymes, antibodies, reactive proteins capable of inactivating toxicants in the body are called bioscavengers. In this review, we focus on enzyme-containing nanoreactors for in vivo detoxification of organophosphorous compounds (OP) to be used for prophylaxis and post-exposure treatment of OP poisoning. A particular attention is devoted to bioscavenger-containing injectable nanoreactors operating in the bloodstream. The nanoreactor concept implements single or multiple enzymes and cofactors co-encapsulated in polymeric semi-permeable nanocontainers. Thus, the detoxification processes take place in a confined space containing highly concentrated bioscavengers. The article deals with historical and theoretical backgrounds about enzymatic detoxification of OPs in nanoreactors, nanoreactor polymeric enveloppes, realizations and advantages over other approaches using bioscavengers.

Precisely Alternating Copolymerization of Episulfides and Isothiocyanates: A Practical Route to Construct Sulfur-Rich Polymers

The development of a controlled and reliable method to construct well-defined sulfur-containing polymers has sparked great interest in polymer science. Herein, we present the trial on the copolymerization of isothiocyanates with episulfides in the presence of organic onium salts, which provides direct access to a class of sulfur-rich polymers. This methodology has combined advantages of simple operation, no metals, mild conditions (25-100 °C), controlled polymerization performance (M_n > 10⁵ g mol^-1, Đ < 1.3), and high reactivity (turnover frequency over 1000 h^-1). The metal-free feature and versatility of the easily accessible monomers, along with fine adjustment of the final properties enable this strategy to be a feasible approach to produce sulfur-rich polymers (16 examples).

Drug-Integrating Amphiphilic Nanomaterial Assemblies: 1. Spatiotemporal control of cyclosporine delivery and activity using nanomicelles and nanofibrils

Immunomodulatory therapies are limited by unavoidable side effects as well as poor solubility, stability, and pharmacokinetic properties. Nanomaterial-based drug delivery may overcome these limitations by increasing drug solubility, site-targeting, and duration of action. Here, we prepared innovative drug-integrating amphiphilic nanomaterial assemblies (DIANA) with tunable hydrophobicity, size, and morphology, and we evaluated their ability to deliver cyclosporine A (CsA) for immunomodulatory applications. We synthesized amphiphilic block copolymers made of poly(ethylene glycol)-poly(propylene sulfide) (PEG-PPS) and poly(ethylene glycol)-oligo(ethylene sulfide) (PEG-OES) that can self-assemble into solid core nanomicelles (nMIC, with ≈20 nm diameter) and nanofibrils (nFIB, with ≈5 nm diameter and > 500 nm length), respectively. nMIC and nFIB displayed good CsA encapsulation efficiency (up to 4.5 and 2 mg/mL, respectively in aqueous solution), superior to many other solubilization methods, and provided sustained release (>14 and > 7 days for the nMIC and nFIB) without compromising CsA's pharmacological activity. Treatment of insulin-secreting cells with unloaded DIANAs did not impair cell viability and functionality. Both CsA-loaded DIANAs inhibited the proliferation and activation of insulin-reactive cytotoxic T cells in vitro. Subcutaneous injections of CsA-loaded DIANAs in mice provided CsA sustained release, decreasing alloantigen-induced immune responses in the draining lymph node at lower doses and reduced administration frequency than unformulated CsA. While nMIC solubilized higher amounts and provided more sustained release of CsA in vitro, nFIB enhanced cellular uptake and promoted local retention due to slower trafficking in vivo. DIANAs provide a versatile platform for a local immune suppression regimen that can be applied to allogeneic cell transplantation.

Library of Derivatizable Multiblock Copolymers by Nucleophilic Substitution Polymerization and Targeting Specific Properties

Multiblock copolymers (MBCs) are fascinating in the field of biology-polymer chemistry interfaces. Synthesizing libraries of MBCs with tailor-made functionality is challenging as it involves multiple steps. Herein, a simple synthesis, analogous to polyurethane/Michael addition reactions, has been introduced to obtain a library of derivatizable MBCs. Nucleophilic substitution polymerization (S_NP) of poly(ε-caprolactone) and poly(ethylene glycol) blocks containing activated halide termini by primary mono/di/coamines or clickable amines provides functional MBCs. The structure of amines directs the properties of the MBCs. The self-assembly of small molecular weight primary diamine-based MBCs shows controlled release of hydrophobic model guest molecules and therapeutics. The primary diamine (no dangling chain) helps to form MBC micelles having a relatively tight core with a low diffusion property. Antimicrobial property in the MBCs has been introduced by separating the cationic centers from the lipophilic groups using a coamine as a nucleophilic agent and a small molecular weight dihalide as a chain extender. Clickable MBCs were synthesized by changing the structure of the nucleophile to obtain degradable amphiphilic conetworks and hydrogels. Varieties of macromolecular entities could be obtained by switching the nucleophilic agent and introducing a small molecular weight chain extender. This synthesis approach provides an opportunity to tune the chemical functionality, topological structure, and biological properties of macromolecular entities.

Homopolymer self-assembly of poly(propylene sulfone) hydrogels via dynamic noncovalent sulfone-sulfone bonding

Natural biomolecules such as peptides and DNA can dynamically self-organize into diverse hierarchical structures. Mimicry of this homopolymer self-assembly using synthetic systems has remained limited but would be advantageous for the design of adaptive bio/nanomaterials. Here, we report both experiments and simulations on the dynamic network self-assembly and subsequent collapse of the synthetic homopolymer poly(propylene sulfone). The assembly is directed by dynamic noncovalent sulfone–sulfone bonds that are susceptible to solvent polarity. The hydration history, specified by the stepwise increase in water ratio within lower polarity water-miscible solvents like dimethylsulfoxide, controls the homopolymer assembly into crystalline frameworks or uniform nanostructured hydrogels of spherical, vesicular, or cylindrical morphologies. These electrostatic hydrogels have a high affinity for a wide range of organic solutes, achieving >95% encapsulation efficiency for hydrophilic small molecules and biologics. This system validates sulfone–sulfone bonding for dynamic self-assembly, presenting a robust platform for controllable gelation, nanofabrication, and molecular encapsulation.

Natural biomolecules such as peptides and DNA can dynamically self-organize into diverse hierarchical structures. Here the authors report experiments and simulations on the dynamic network self-assembly and subsequent collapse of the synthetic homopolymer poly(propylene sulfone).

Repurposing poly(monothiocarbonate)s to poly(thioether)s with organic bases

This work reports a unique one-pot/one-step route to rapidly produce poly(thioether)s from poly(monothiocarbonate) (PMTC), a sulfur-containing polymer, using commercially available organic bases.

Histamine, an effective initiator for the synthesis of polysulfides

A solvent-free and metal-free synthesis of highly pure polysulfides is described using histamine, a primary amine, as an initiator.

Surface engineered polymersomes for enhanced modulation of dendritic cells during cardiovascular immunotherapy

The principle cause of cardiovascular disease (CVD) is atherosclerosis, a chronic inflammatory condition characterized by immunologically complex fatty lesions within the intima of arterial vessel walls. Dendritic cells (DCs) are key regulators of atherosclerotic inflammation, with mature DCs generating pro-inflammatory signals within vascular lesions and tolerogenic DCs eliciting atheroprotective cytokine profiles and regulatory T cell (Treg) activation. Here, we engineered the surface chemistry and morphology of synthetic nanocarriers composed of poly(ethylene glycol)-b-poly(propylene sulfide) copolymers to selectively target and modulate DCs by transporting the anti-inflammatory agent 1, 25-Dihydroxyvitamin D3 (aVD) and ApoB-100 derived antigenic peptide P210. Polymersomes decorated with an optimized surface display and density for a lipid construct of the P-D2 peptide, which binds CD11c on the DC surface, significantly enhanced the cytosolic delivery and resulting immunomodulatory capacity of aVD in vitro. Intravenous administration of the optimized polymersomes achieved selective targeting of DCs in atheroma and spleen compared to all other cell populations, including both immune and CD45- cells, and locally increased the presence of tolerogenic DCs and cytokines. aVD-loaded polymersomes significantly inhibited atherosclerotic lesion development in high fat diet-fed ApoE-/- mice following 8 weeks of administration. Incorporation of the P210 peptide generated the largest reductions in vascular lesion area (~33%, p<0.001), macrophage content (~55%, p<0.001), and vascular stiffness (4.8-fold). These results correlated with an ~6.5-fold increase in levels of Foxp3+ regulatory T cells within atherosclerotic lesions. Our results validate the key role of DC immunomodulation during aVD-dependent inhibition of atherosclerosis and demonstrate the therapeutic enhancement and dosage lowering capability of cell-targeted nanotherapy in the treatment of CVD.

Synthesis of Silane-Based Poly(thioether) via Successive Click Reaction and Their Applications in Ion Detection and Cell Imaging

A series of poly(thioether)s containing silicon atom with unconventional fluorescence were synthesized via successive thiol click reaction at room temperature. Although rigid π-conjugated structure did not exist in the polymer chain, the poly(thioether)s exhibited excellent fluorescent properties in solutions and showed visible blue fluorescence in living cells. The strong blue fluorescence can be attributed to the aggregation of lone pair electron of heteroatom and coordination between heteroatom and Si atom. In addition, the responsiveness of poly(thioether) to metal ions suggested that the selectivity of poly(thioether) to Fe³⁺ ion could be enhanced by end-modifying with different sulfhydryl compounds. This study further explored their application in cell imaging and studied their responsiveness to Fe³⁺ in living cells. It is expected that the described synthetic route could be extended to synthesize novel poly(thioether)s with superior optical properties. Their application in cell imaging and ion detection will broaden the range of application of poly(thioether)s.

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.

Reactive oxygen species (ROS)-responsive biomaterials mediate tissue microenvironments and tissue regeneration

ROS-responsive biomaterials alleviate the oxidative stress in tissue microenvironments, promoting tissue regeneration and disease therapy.

Organocatalytic Ring-opening Polymerization Towards Poly(cyclopropane)s, Poly(lactame)s, Poly(aziridine)s, Poly(siloxane)s, Poly(carbosiloxane)s, Poly(phosphate)s, Poly(phosphonate)s, Poly(thiolactone)s, Poly(thionolactone)s and Poly(thiirane)s

The following chapter is a collection of monomers that undergo organocatalyzed ring-opening polymerizations and have not been covered in a separate chapter of this book. This includes polymers widely used in industrial applications, but also solely academically relevant and more “exotic” polymer classes. As most of these polymers contain heteroatoms in their backbone, the chapter is divided according to the respective heteroatoms. Each sub-section first gives a short introduction to the respective polymer or monomer properties and industrial applications (if available), followed by a brief summary of the traditional synthetic pathways. Afterwards, important milestones for the organocatalytic ROP are presented in chronological order. Special emphasis is put on the advantages and disadvantages of organocatalysis over traditional (ROP) methods on the basis of appropriate literature examples.

Synchronous Chemoradiation Nanovesicles by X-Ray Triggered Cascade of Drug Release

The approach of concurrent-to-synchronous chemoradiation has now been advanced by well-designed nanovesicles that permit X-ray irradiation-triggered instant drug release. The nanovesicles consist of Au nanoparticles tethered with irradiation labile linoleic acid hydroperoxide (LAHP) molecules and oxidation-responsive poly(propylene sulfide)-poly(ethylene glycol) (PPS-PEG) polymers, where DOX were loaded in the inner core of the vesicles (Au-LAHP-vDOX). Upon irradiation, the in situ formation of hydroxyl radicals from LAHP molecules triggers the internal oxidation of PPS from being hydrophobic to hydrophilic, leading to degradation of the vesicles and burst release of cargo drugs. In this manner, synchronous chemoradiation showed impressive anticancer efficacy both in vitro and in a subcutaneous mouse tumor model by one-dose injection and one-time irradiation.

Sequential intracellular release of water-soluble cargos from Shell-crosslinked polymersomes

Polymer vesicles, i.e. polymersomes (PS), present unique nanostructures with an interior aqueous core that can encapsulate multiple independent cargos concurrently. However, the sequential release of such co-loaded actives remains a challenge. Here, we report the rational design and synthesis of oxidation-responsive shell-crosslinked PS with capability for the controlled, sequential release of encapsulated hydrophilic molecules and hydrogels. Amphiphilic brush block copolymers poly(oligo(ethylene glycol) methyl ether methacrylate)-b-poly(oligo(propylene sulfide) methacrylate) (POEGMA-POPSMA) were prepared to fabricate PS via self-assembly in aqueous solution. As a type of unique drug delivery vehicle, the interior of the PS was co-loaded with hydrophilic molecules and water-soluble poly(N-isopropylacrylamide) (PNIPAM) conjugates. Due to the thermosensitivity of PNIPAM, PNIPAM conjugates within the PS aqueous interior underwent a phase transition to form hydrogels in situ when the temperature was raised above the lower critical solution temperature (LCST) of PNIPAM. Via control of the overall shell permeability by oxidation, we realized the sequential release of two water-soluble payloads based on the assumption that hydrogels have much smaller membrane permeability than that of molecular cargos. The ability to control the timing of release of molecular dyes and PNIPAM-based hydrogels was also observed within live cells. Furthermore, leakage of hydrogels from the PS was effectively alleviated in comparison to molecular cargos, which would facilitate intracellular accumulation and prolonged retention of hydrogels within the cell cytoplasm. Thus, we demonstrate that the integration of responsive hydrogels into PS with crosslinkable membranes provides a facile and versatile technique to control the stability and release of water-soluble cargos for drug delivery purposes.

The effect of a crosslinking chemical reaction on pattern formation in viscous fingering of miscible fluids in a Hele-Shaw cell

Viscous fingering can occur in fluid motion whenever a high mobility fluid displaces a low mobility fluid in a Darcy type flow. When the mobility difference is primarily attributable to viscosity (e.g., flow between the two horizontal plates of a Hele-Shaw cell), viscous fingering (VF) occurs, which is sometimes termed the Saffman-Taylor instability. Alternatively, in the presence of differences in density in a gravity field, buoyancy-driven convection can occur. These instabilities have been studied for decades, in part because of their many applications in pollutant dispersal, ocean currents, enhanced petroleum recovery, and so on. More recent interest has emerged regarding the effects of chemical reactions on fingering instabilities. As chemical reactions change the key flow parameters (densities, viscosities, and concentrations), they may have either a destabilizing or stabilizing effect on the flow. Hence, new flow patterns can emerge; moreover, one can then hope to gain some control over flow instabilities through reaction rates, flow rates, and reaction products. We report effects of chemical reactions on VF in a Hele-Shaw cell for a reactive step-growth cross-linking polymerization system. The cross-linked reaction product results in a non-monotonic viscosity profile at the interface, which affects flow stability. Furthermore, three-dimensional internal flows influence the long-term pattern that results.

Multifunctional Nanoparticles Self-Assembled from Small Organic Building Blocks for Biomedicine

Supramolecular self-assembly shows significant potential to construct responsive materials. By tailoring the structural parameters of organic building blocks, nanosystems can be fabricated, whose performance in catalysis, energy storage and conversion, and biomedicine has been explored. Since small organic building blocks are structurally simple, easily modified, and reproducible, they are frequently employed in supramolecular self-assembly and materials science. The dynamic and adaptive nature of self-assembled nanoarchitectures affords an enhanced sensitivity to the changes in environmental conditions, favoring their applications in controllable drug release and bioimaging. Here, recent significant research advancements of small-organic-molecule self-assembled nanoarchitectures toward biomedical applications are highlighted. Functionalized assemblies, mainly including vesicles, nanoparticles, and micelles are categorized according to their topological morphologies and functions. These nanoarchitectures with different topologies possess distinguishing advantages in biological applications, well incarnating the structure-property relationship. By presenting some important discoveries, three domains of these nanoarchitectures in biomedical research are covered, including biosensors, bioimaging, and controlled release/therapy. The strategies regarding how to design and characterize organic assemblies to exhibit biomedical applications are also discussed. Up-to-date research developments in the field are provided and research challenges to be overcome in future studies are revealed.

Specific Cancer Cytosolic Drug Delivery Triggered by Reactive Oxygen Species-Responsive Micelles

Cytosolic drug delivery, a major route in cancer therapy, is limited by the lack of efficient and safe endosomal escape techniques. Herein, we demonstrate a reactive oxygen species (ROS)-responsive micelle composed of methoxy polyethylene glycol-b-poly(diethyl sulfide) (mPEG-PS) copolymers which can induce specific endosome escape in cancer cells by changes in the hydrophobicity of copolymers. Owing to the more ROS levels in cancer cells than normal cells, the copolymers can be converted into more hydrophilic and insert into and destabilize the cancer intracellular endosome membrane after cellular uptake. More importantly, we show that acid-intolerant drugs successfully maintain their bioactivity and cause selective cytotoxicity for cancer cells over normal cells. Our results suggest that the endosomal escape induced by hydrophobic-hydrophilic exchange of copolymers has great potential to locally and efficiently deliver biological agents (e.g., proteins and genes) in the cancer cell cytosol.

Light-controlled reactive oxygen species (ROS)-producible polymeric micelles with simultaneous drug-release triggering and endo/lysosomal escape

A doxorubicin (DOX)-loaded and light-induced ROS-producing polymeric micelle (D-LRPM), in which light triggers simultaneous DOX-release and endo/lysosomal escape, produces a powerful, spatiotemporally controllable, therapeutic efficacy for tumor treatment.

Synthesis of Highly Fluorescent Copper Clusters Using Living Polymer Chains as Combined Reducing Agents and Ligands

We present the synthesis of colloidally stable ultrasmall (diameter of 1.5 ± 0.6 nm) and fluorescent copper clusters (Cu-clusters) exhibiting outstanding quantum efficiencies (up to 67% in THF and approximately 30% in water). For this purpose, an amphiphilic block copolymer poly(ethylene glycol)-block-poly(propylene sulfide) (MPEG-b-PPS) was synthesized by living anionic ring-opening polymerization. When CuBr is mixed with the living polymer chains in THF, the formation of Cu-clusters is detected by the appearance of the fluorescence. The cluster growth is quenched by the addition of water, followed by THF removal. The structural features of the MPEG-b-PPS copolymer control the cluster formation and the stabilization: the poly(propylene sulfide) segment acts as coordinating and reducing agent for the copper ions in THF, and imparts a hydrophobic character. This hydrophobic block protects the Cu-clusters from water exposure, thus allowing to obtain a stable emission in water. The PEG segment instead provides the hydrophilicity, rendering the Cu-clusters water-soluble. To obtain fluorescent and stable Cu-clusters exhibiting outstanding quantum efficiencies, the removal of the excess of free polymer and copper salt was crucial. The Cu-clusters are also colloidally and optically stable in physiological media and showed bright fluorescence even when taken up by HeLa cells, being noncytotoxic when administered at a Cu dose between 10 nM and 1.6 μM. Given the very small size of the Cu-clusters, localization and fluorescent staining of cell nucleus is achieved, as demonstrated by confocal cell imaging performed at different Cu-cluster doses and at different incubation temperatures.