ROS-Responsive Poly(α-l-lysine)-Based Nanoparticles Loaded with Doxycycline Combat Oxidative Stress and Bacterial Infection

Bacterial pneumonia is one of the major threats in clinical practice, and the reactive oxygen species (ROS) generated at the infection site can exacerbate the damage. Currently, conventional antibiotic therapies have low utilization, and their excessive use can result in substantial toxicity. Nanocarrier systems provide an ideal approach for treating bacterial infection by facilitating more efficient utilization of antibiotics. In this study, the ROS-responsive amphiphilic nanoparticles (NPs) are developed and used to encapsulate the antibiotic doxycycline (DOXY) to achieve antibacterial and antioxidant functionalities. The NPs are prepared from poly(α-l-lysine) (α-PLL) and phenylboronic acid pinacol ester simultaneously conjugated carbonyldiimidazole (abbreviated as CDIPB). The phenylboronic acid ester groups on CDIPB could react with excessive ROS to suppress oxidative damage at the infection site. The ROS-responsive degradation of CDIPB also facilitates the rapid release of internal DOXY, effectively killing the accumulated bacteria. Additionally, in vitro cell experiments demonstrate the good biocompatibility of the NPs. These results suggest that the ROS-responsive amphiphilic nanoparticles can serve as a novel nanoplatform for the treatment of bacterial pneumonia.

Unlocking the Mitochondria for Nanomedicine-based Treatments: Overcoming Biological Barriers, Improving Designs, and Selecting Verification Techniques

Enhanced targeting approaches will support the treatment of diseases associated with dysfunctional mitochondria, which play critical roles in energy generation and cell survival. Obstacles to mitochondria-specific targeting include the presence of distinct biological barriers and the need to pass through (or avoid) various cell internalization mechanisms. A range of studies have reported the design of mitochondrially-targeted nanomedicines that navigate the complex routes required to influence mitochondrial function; nonetheless, a significant journey lies ahead before mitochondrially-targeted nanomedicines become suitable for clinical use. Moving swiftly forward will require safety studies, in vivo assays confirming effectiveness, and methodologies to validate mitochondria-targeted nanomedicines' subcellular location/activity. From a nanomedicine standpoint, we describe the biological routes involved (from administration to arrival within the mitochondria), the features influencing rational design, and the techniques used to identify/validate successful targeting. Overall, rationally-designed mitochondria-targeted-based nanomedicines hold great promise for precise subcellular therapeutic delivery.

Drug in Therapeutic Polymer: Sinomenine-Loaded Oxidation-Responsive Polymeric Nanoparticles for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that frequently involves cartilage damage and the destruction of the bone structure, ultimately resulting in disability and long-term pain. It is clear that overexpression of reactive oxygen species (ROS) and the complex inflammatory microenvironment are the main causes of RA pathogenesis; thereby, the efficacy of any single-drug treatment is limited. Herein, we formulated a therapeutic hyaluronic acid derivative (PAM-HA) with adsorption capacity to the subchondral bone, a long retention time within inflamed joints, and ROS-scavenging capacity, which was used as a drug carrier for realizing the controlled release of sinomenine (Sin) within arthritic joints. This "drug in therapeutic polymer" design strategy was aimed at realizing antioxidant and anti-inflammatory combination therapy for RA. In vivo experiments suggest that PAM-HA@Sin NPs can be retained in the inflamed joints of rats for a long time compared with commercially available free Sin injections. As expected, therapeutic PAM-HA polymeric carriers can increase joint lubrication and reduce oxidative stress, while the released Sin induces downregulation of proinflammatory factors (TNF-α and IL-1β) and upregulation of anti-inflammatory factors (Arg-1 and IL-10) via the NF-κB pathway. In summary, a ROS-scavenging hyaluronic acid (HA) derivative was developed as the nanocarrier for Sin delivery to simultaneously remodel the oxidative/inflammatory microenvironment in RA, which opens up new horizons for the development of therapeutic polymers and the combined therapeutic strategies.

Polysulfide nanoparticles inhibit fibroblast-to-myofibroblast transition via extracellular ROS scavenging and have potential anti-fibrotic properties

This paper is about the effects of reactive oxygen species (ROS) - and of their nanoparticle-mediated extracellular removal - in the TGF-β1-induced differentiation of fibroblasts (human dermal fibroblasts - HDFa) to more contractile myofibroblasts, and in the maintenance of this phenotype. Here, poly(propylene sulfide) (PPS) nanoparticles have been employed on 2D and 3D in vitro models, showing extremely low toxicity and undergoing negligible internalization, thereby ensuring an extracellular-only action. Firstly, PPS nanoparticles abrogated ROS-mediated downstream molecular events such as glutathione oxidation, NF-κB activation, and heme oxidase-1 (HMOX) overexpression. Secondly, PPS nanoparticles were also capable to inhibit, prevent and reverse the TGF-β1-induced upregulation of key biomechanical elements, such as ED-a fibronectin (EF-A FN) and alpha-smooth muscle actin (α-SMA), respectively markers of protomyofibroblastic and of myofibroblastic differentiation. We also confirmed that ROS alone are ineffective promoters of the myofibroblastic transition, although their presence contributes to its stabilization. Finally, the particles also countered TGF-β1-induced matrix- and tissue-level phenomena, e.g., the upregulation of collagen type 1, the development of aberrant collagen type 1/3 ratios and the contracture of HDFa 3D-seeded fibrin constructs. In short, experimental data at molecular, cellular and tissue levels show a significant potential in the use of PPS nanoparticles as anti-fibrotic agents.

Opportunities and Challenges of Switchable Materials for Pharmaceutical Use

Switchable polymeric materials, which can respond to triggering signals through changes in their properties, have become a major research focus for parenteral controlled delivery systems. They may enable externally induced drug release or delivery that is adaptive to in vivo stimuli. Despite the promise of new functionalities using switchable materials, several of these concepts may need to face challenges associated with clinical use. Accordingly, this review provides an overview of various types of switchable polymers responsive to different types of stimuli and addresses opportunities and challenges that may arise from their application in biomedicine.

An enhanced antioxidant strategy of astaxanthin encapsulated in ROS-responsive nanoparticles for combating cisplatin-induced ototoxicity

Background

Excessive accumulation of reactive oxygen species (ROS) has been documented as the crucial cellular mechanism of cisplatin-induced ototoxicity. However, numerous antioxidants have failed in clinical studies partly due to inefficient drug delivery to the cochlea. A drug delivery system is an attractive strategy to overcome this drawback.

Methods and results

In the present study, we proposed the combination of antioxidant astaxanthin (ATX) and ROS-responsive/consuming nanoparticles (PPS-NP) to combat cisplatin-induced ototoxicity. ATX-PPS-NP were constructed by the self-assembly of an amphiphilic hyperbranched polyphosphoester containing thioketal units, which scavenged ROS and disintegrate to release the encapsulated ATX. The ROS-sensitivity was confirmed by ¹H nuclear magnetic resonance spectroscopy, transmission electron microscopy and an H₂O₂ ON/OFF stimulated model. Enhanced release profiles stimulated by H₂O₂ were verified in artificial perilymph, the HEI-OC1 cell line and guinea pigs. In addition, ATX-PPS-NP efficiently inhibited cisplatin-induced HEI-OC1 cell cytotoxicity and apoptosis compared with ATX or PPS-NP alone, suggesting an enhanced effect of the combination of the natural active compound ATX and ROS-consuming PPS-NP. Moreover, ATX-PPS-NP attenuated outer hair cell losses in cultured organ of Corti. In guinea pigs, NiRe-PPS-NP verified a quick penetration across the round window membrane and ATX-PPS-NP showed protective effect on spiral ganglion neurons, which further attenuated cisplatin-induced moderate hearing loss. Further studies revealed that the protective mechanisms involved decreasing excessive ROS generation, reducing inflammatory chemokine (interleukin-6) release, increasing antioxidant glutathione expression and inhibiting the mitochondrial apoptotic pathway.

Conclusions

Thus, this ROS-responsive nanoparticle encapsulating ATX has favorable potential in the prevention of cisplatin-induced hearing loss.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01485-8.

Dexamethasone-loaded ROS-responsive poly(thioketal) nanoparticles suppress inflammation and oxidative stress of acute lung injury

Acute lung injury (ALI) is associated with excessive inflammatory response, leading to acute respiratory distress syndrome (ARDS) without timely treatment. A fewer effective drugs are available currently to treat the ALI/ARDS. Herein, a therapeutic nanoplatform with reactive oxygen species (ROS)-responsiveness was developed for the regulation of inflammation. Dexamethasone acetate (Dex) was encapsulated into poly(thioketal) polymers to form polymeric nanoparticles (NPs) (PTKNPs@Dex). The NPs were composed of poly(1,4-phenyleneacetonedimethylene thioketal) (PPADT) and polythioketal urethane (PTKU), in which the thioketal bonds could be cleaved by the high level of ROS at the ALI site. The PTKNPs@Dex could accumulate in the pulmonary inflammatory sites and release the encapsulated payloads rapidly, leading to the decreased ROS level, less generation of pro-inflammatory cytokines, and reduced lung injury and mortality of mice. RNA sequencing (RNA-seq) analysis showed that the therapeutic efficacy of the NPs was associated with the modulation of many immune and inflammation-linked pathways. These findings provide a newly developed nanoplatform for the efficient treatment of ALI/ARDS.

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A therapeutic nanoplatform with ROS-responsiveness was developed for the regulation of inflammation.

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NPs composed of low Mw of PPADT and high Mw of PTKU were loaded with dexamethasone to obtain a self-adaptive system.

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The Dex-loaded NPs significantly decreased lung inflammation, and reduced lung injury and mortality in vivo.

Passerini chemistries for synthesis of polymer pro-drug and polymersome drug delivery nanoparticles

New materials chemistries are urgently needed to overcome the limitations of existing biomedical materials in terms of preparation, functionality and versatility, and also in regards to their compatibility with biological...

Implementation of surface functionalization of MnS nanoparticles for achieving novel optical properties and improving therapeutic potential

The citrate capping of solubilized MnS nanoparticles in water produced photo-induced pH switching. Citrate-MnS shows remarkable ROS production at acidic and neutral pH in the dark, at pH 5 ROS production demonstrates bilirubin degradation and antimicrobial activity.

Vinyl mercaptoethanol as a reactive monomer for the preparation of functional homo- and copolymers with (meth)acrylates

Vinyl mercaptoethanol is a scalable vinyl thioether monomer, which can readily be polymerized in a free radical process or by controlled methods. It tends to form alternating copolymers if copolymerized with acrylates and methacrylates.

Thioanisole ester based logic gate cascade to control ROS-triggered micellar degradation

Thioanisole ester polymer side chains hydrolyze exclusively upon thioether oxidation, showing logic gate response. ROS-induced ester hydrolysis on the hydrophobic domain leads to nanocarrier disassembly with potential for targeted drug release.

Development of an Acid-Labile Ketal Linked Amphiphilic Block Copolymer Nanoparticles for pH-Triggered Release of Paclitaxel

Here, we report on the construction of biodegradable poly(ethylene oxide monomethyl ether) (MPEO)-b-poly(ε-caprolactone) (PCL) nanoparticles (NPs) having acid-labile (acyclic ketal group) linkage at the block junction. In the presence of acidic pH, the nanoassemblies were destabilized as a consequence of cleaving this linkage. The amphiphilic MPEO-b-PCL diblock copolymer self-assembled in PBS solution into regular spherical NPs. The structure of self-assemble and disassemble NPs were characterized in detail by dynamic (DLS), static (SLS) light scattering, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). The key of the obtained NPs is using them in a paclitaxel (PTX) delivery system and study their in vitro cytostatic activity in a cancer cell model. The acid-labile ketal linker enabled the disassembly of the NPs in a buffer simulating an acidic environment in endosomal (pH ~5.0 to ~6.0) and lysosomal (pH ~4.0 to ~5.0) cell compartments resulting in the release of paclitaxel (PTX) and formation of neutral degradation products. The in vitro cytotoxicity studies showed that the activity of the drug-loaded NPs was increased compared to the free PTX. The ability of the NPs to release the drug at the endosomal pH with concomitant high cytotoxicity makes them suitable candidates as a drug delivery system for cancer therapy.

Selective Oxidation of Polysulfide Latexes to Produce Polysulfoxide and Polysulfone in a Waterborne Environment

Polymers containing sulfur centers with high oxidation states in the main chain, polysulfoxide and polysulfone, display desirable properties such as thermomechanical and chemical stability. To circumvent their challenging direct synthesis, methods based on the oxidation of a parent polysulfide have been developed but are plagued by uncontrolled reactions, leading either to ill-defined mixtures of polysulfoxides and polysulfones or to polysulfones with reduced degrees of polymerization due to overoxidation of the polymer. We developed an alternative method to produce well-defined polysulfoxide and polysulfone in a waterborne colloidal emulsion using different oxidants to control the oxidation state of sulfur in the final materials. The direct oxidation of water-based polysulfide latexes avoided the use of volatile organic solvents and allowed for the control of the oxidation state of the sulfur atoms. Oxidation of parent polysulfides by tert-butyl hydroperoxide led to the production of pure polysulfoxides, even after 70 days of reaction time. Additionally, hydrogen peroxide produced both species through the course of the reaction but yielded fully converted polysulfones after 24 h. By employing mild oxidants, our approach controlled the oxidation state of the sulfur atoms in the final sulfur-containing polymer and prevented any overoxidation, thus ensuring the integrity of the polymer chains and colloidal stability of the system. We also verified the selectivity, versatility, and robustness of the method by applying it to polysulfides of different chemical compositions and structures. The universality demonstrated by this method makes it a powerful yet simple platform for the design of sulfur-containing polymers and nanoparticles.

Designing responsive dressings for inflammatory skin disorders; encapsulating antioxidant nanoparticles into biocompatible electrospun fibres

Inflammatory skin disorders are highly prevalent and current treatments are marred by side-effects. Here, we have designed anti-inflammatory fibrous sheets with the potential to treat low exudate inflammatory skin disorders such as psoriasis or atopic dermatitis. Antioxidant and anti-inflammatory nanoparticles composed of crosslinked poly(propylene sulfide) (PPS) were encapsulated in poly(ethylene oxide) (PEO) fibres via electrospinning from an aqueous suspension. The loading of nanoparticles did not adversely effect the homogenous nature of the electrospun fibres; furthermore, nanoparticles retained their morphology, size and anti-inflammatory character after electrospinning. The PPS-nanoparticle-loaded nanofibres were found to be highly cytocompatible when tested on human dermal fibroblasts. These findings suggest they have significant potential to topically treat inflamed tissues that are characterized by high reactive oxygen species (ROS) levels.

Oxidative regulation of the mechanical strength of a C-S bond

The mechanical strength of individual polymer chains is believed to underlie a number of performance metrics in bulk materials, including adhesion and fracture toughness. Methods by which the intrinsic molecular strength of the constituents of a given polymeric material might be switched are therefore potentially useful both for applications in which triggered property changes are desirable, and as tests of molecular theories for bulk behaviors. Here we report that the sequential oxidation of sulfide containing polyesters (PE-S) to the corresponding sulfoxide (PE-SO) and then sulfone (PE-SO2) first weakens (sulfoxide), and then enhances (sulfone), the effective mechanical integrity of the polymer backbone; PE-S ∼ PE-SO2 > PE-SO. The relative mechanical strength as a function of oxidation state is revealed through the use of gem-dichlorocyclopropane nonscissile mechanophores as an internal standard, and the observed order agrees well with the reported bond dissociation energies of C–S bonds in each species and with the results of CoGEF modeling.

The mechanical strength of individual polymer chains is believed to underlie a number of performance metrics in bulk materials, including adhesion and fracture toughness.

The interpretation of small molecule diffusion coefficients: Quantitative use of diffusion-ordered NMR spectroscopy

Measuring accurate molecular self-diffusion coefficients, D, by nuclear magnetic resonance (NMR) techniques has become routine as hardware, software and experimental methodologies have all improved. However, the quantitative interpretation of such data remains difficult, particularly for small molecules. This review article first provides a description of, and explanation for, the failure of the Stokes-Einstein equation to accurately predict small molecule diffusion coefficients, before moving on to three broadly complementary methods for their quantitative interpretation. Two are based on power laws, but differ in the nature of the reference molecules used. The third addresses the uncertainties in the Stokes-Einstein equation directly. For all three methods, a wide range of examples are used to show the range of chemistry to which diffusion NMR can be applied, and how best to implement the different methods to obtain quantitative information from the chemical systems studied.

Main Chain Polysulfoxides as Active 'Stealth' Polymers with Additional Antioxidant and Anti-Inflammatory Behaviour

We present the evaluation of a sulfoxide-based polymer (poly(propylene sulfoxide), PPSO) as a potential 'stealth' macromolecule, and at the same time as a pharmacologically active (anti-inflammatory/anti-oxidant) material. The combination of these two concepts may at first seem peculiar since the gold standard polymer in biomaterials and drug delivery, poly(ethylene glycol) (PEG), is 'stealth' due to its chemical and biological inertness, which makes it hardly biologically active. Polysulfoxides, on the contrary, may couple a substantial inertness towards biomolecules under homeostatic conditions, with the possibility to scavenge reactive oxygen species (ROS) associated to inflammation. Polysulfoxides, therefore, are rather uniquely, 'active' 'stealth' polymers. Here, we describe the synthesis of PPSO through controlled oxidation of poly(propylene sulfide) (PPS), which on its turn was obtained via anionic ring-opening polymerization. In vitro, PPSO was characterized by a low toxicity (IC50 ~7 mg/mL at 24 h on human dermal fibroblasts) and a level of complement activation (in human plasma) and macrophage uptake slightly lower than PEG of a similar size. Importantly, and differently from PEG, on LPS-activated macrophages, PPSO showed a strong and dose-dependent ROS (hydrogen peroxide and hypochlorite)-scavenging activity, which resulted in a corresponding reduction of cytokine production.

The polymerization kinetics, oxidation-responsiveness, and in vitro anticancer efficacy of poly(ester-thioether)s

The oxidation-responsiveness and biomedical properties of poly(ester-thioether)s could be tuned by varying the polymer backbones.

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.

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.

Facile synthesis of ROS-responsive biodegradable main chain poly(carbonate-thioether) copolymers

The amphiphilic main chain poly(carbonate-thioether) copolymers were synthesized based on a novel macrocyclic sulfur-substituted carbonate monomer. The assembled nanostructures have rich ROS responsiveness.

Polymeric micelles with dual thermal and reactive oxygen species (ROS)-responsiveness for inflammatory cancer cell delivery

Background

The object of this study was to develop a thermally and reactive oxygen species-responsive nanocarrier system for cancer therapy.

Results

PPS-PNIPAm block copolymer was designed and synthesised using a combination of living anionic ring-opening polymerization and atom transfer radical polymerization. The synthesized polymer formed micellar aggregates in water and demonstrated dual responsiveness towards temperature and oxidants. Using doxorubicin (DOX) as a model drug, encapsulation and in vitro release of the drug molecules in PPS-PNIPAm nanocarriers confirmed the responsive release properties of such system. Cell uptake of the DOX loaded micelles was investigated with human breast cancer cell line (MCF-7). The results showed Dox-loaded micelles were able to be taken by the cells and mainly reside in the cytoplasma. In the stimulated cells with an elevated level of ROS, more released DOX was observed around the nuclei. In the cytotoxicity experiments, the Dox-loaded micelles demonstrated comparable efficacy to free DOX at higher concentrations, especially on ROS stimulated cells.

Conclusions

These results demonstrated that PPS-PNIPAm nanocarriers possess the capability to respond two typical stimuli in inflammatory cells: temperature and oxidants and can be used in anticancer drug delivery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-017-0275-4) contains supplementary material, which is available to authorized users.

Fluorescent boronate-based polymer nanoparticles with reactive oxygen species (ROS)-triggered cargo release for drug-delivery applications

A new drug-delivery system of polymer nanoparticles (NPs) bearing pinacol-type boronic ester and alkyne moieties displaying triggered self-immolative polymer degradation in the presence of reactive oxygen species (ROS) with the capability of cellular imaging is presented. The NPs specifically release their drug cargo under concentrations of ROS that are commonly found in the intracellular environment of certain tumors and of inflamed tissues and exhibit significant cytotoxicity to cancer cells compared to their non-ROS-responsive counterparts.

Lipase-catalyzed synthesis of oxidation-responsive poly(ethylene glycol)-b-poly(β-thioether ester) amphiphilic block copolymers

Lipase-catalyzed one-step synthesis of novel oxidation-responsive poly(ethylene glycol)-b-poly(β-thioether ester) diblock copolymers was reported.

Binary behaviour of an oxidation-responsive MRI nano contrast agent

A new nano contrast agent has been prepared incorporating a molecular magnet in oxidation-responsive nanoparticles; this system has shown a remarkable sensitivity to hydrogen peroxide (detection down to at least 40 μM), which was used as a model reactive oxygen species. Surprisingly, the response had a binary (off/on) character, due to a non-linear cascade relation between extent of oxidation and water permeability in the particles.

Oxidation-responsive polymers for biomedical applications

This article summarizes recent progress in the design and synthesis of various oxidation-responsive polymers and their application in biomedical fields.