Synthesis of CaO2 Nanocrystals and Their Spherical Aggregates with Uniform Sizes for Use as a Biodegradable Bacteriostatic Agent

Fabricating oxygen self-supplying 3D printed bioactive hydrogel scaffold for augmented vascularized bone regeneration

Limited cells and factors, inadequate mechanical properties, and necrosis of defects center have hindered the wide clinical application of bone-tissue engineering scaffolds. Herein, we construct a self-oxygenated 3D printed bioactive hydrogel scaffold by integrating oxygen-generating nanoparticles and hybrid double network hydrogel structure. The hydrogel scaffold possesses the characteristics of extracellular matrix; Meanwhile, the fabricated hybrid double network structure by polyacrylamide and CaCl2-crosslinked sodium carboxymethylcellulose endows the hydrogel favorable compressive strength and 3D printability. Furthermore, the O2 generated by CaO2 nanoparticles encapsulated in ZIF-8 releases steadily and sustainably because of the well-developed microporous structure of ZIF-8, which can significantly promote cell viability and proliferation in vitro, as well as angiogenesis and osteogenic differentiation with the assistance of Zn2+. More significantly, the synergy of O2 and 3D printed pore structure can prevent necrosis of defects center and facilitate cell infiltration by providing cells the nutrients and space they need, which can further induce vascular network ingrowth and accelerate bone regeneration in all areas of the defect in vivo. Overall, this work provides a new avenue for preparing cell/factor-free bone-tissue engineered scaffolds that possess great potential for tissue regeneration and clinical alternative.

A self-supplied hydrogen peroxide and nitric oxide-generating nanoplatform enhances the efficacy of chemodynamic therapy for biofilm eradication

Bacterial biofilms present a profound challenge to global public health, often resulting in persistent and recurrent infections that resist treatment. Chemodynamic therapy (CDT), leveraging the conversion of hydrogen peroxide (H2O2) to highly reactive hydroxyl radicals (•OH), has shown potential as an antibacterial approach. Nonetheless, CDT struggles to eliminate biofilms due to limited endogenous H2O2 and the protective extracellular polymeric substances (EPS) within biofilms. This study introduces a multifunctional nanoplatform designed to self-supply H2O2 and generate nitric oxide (NO) to overcome these hurdles. The nanoplatform comprises calcium peroxide (CaO2) for sustained H2O2 production, a copper-based metal-organic framework (HKUST-1) encapsulating CaO2, and l-arginine (l-Arg) as a natural NO donor. When exposed to the acidic microenvironment within biofilms, the HKUST-1 layer decomposes, releasing Cu2+ ions and l-Arg, and exposing the CaO2 core to initiate a cascade of reactions producing reactive species such as H2O2, •OH, and superoxide anions (•O2-). Subsequently, H2O2 catalyzes l-Arg to produce NO, which disperses the biofilm and reacts with •O2- to form peroxynitrite, synergistically eradicating bacteria with •OH. In vitro assays demonstrated the nanoplatform's remarkable antibiofilm efficacy against both Gram-positive Methicillin-resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa, significantly reducing bacterial viability and EPS content. In vivo mouse model experiments validated the nanoplatform's effectiveness in eliminating biofilms and promoting infected wound healing without adverse effects. This study represents a breakthrough in overcoming traditional CDT limitations by integrating self-supplied H2O2 with NO's biofilm-disrupting capabilities, offering a promising therapeutic strategy for biofilm-associated infection.

Fabrication of fiber-particle structures by electrospinning/electrospray combination as an intrinsic antioxidant and oxygen-releasing wound dressing

In this study, we employed a combination of electrospinning and electrospray techniques to fabricate wound dressings with a particle-fiber structure, providing dual characteristics of oxygen-releasing and intrinsic antioxidant properties, simultaneously. The electrospun part of the dressing was prepared from a blend of polycaprolactone/gallic acid-grafted-gelatin (GA-g-GE), enabling intrinsic ROS scavenging. To the best of our knowledge, this is the first time that PCL/GA-g-GE was fabricated by electrospinning. Furthermore, polyvinyl pyrrolidone (PVP) microparticles, containing calcium peroxide nanoparticles (CNPs), were considered as the oxygen production agent through the electrospray part. The CNP content was 1% and 3% w/w of PVP while biopolymer:PCL was 10% w/w. The fabricated structures were characterized in terms of fiber/particle morphology, elemental analysis, oxygen release behavior, ROS inhibition capacity, and water contact angle assessments. The covalent bonding of gallic acid to gelatin was confirmed by 1H-NMR, UV spectroscopy, and FTIR. According to the SEM results, the morphology of the prepared PCL/biopolymer fibers was bead-free and with a uniform average diameter. The analysis of released oxygen showed that by increasing the weight percentage of CNPs from 1 to 3 wt%, the amount of released oxygen increased from 120 mmHg to 195 mmHg in 24 h, which remained almost constant until 72 h. The obtained DPPH assay results revealed that the introduction of GA-g-GE into the fibrous structure could significantly improve the antioxidant properties of wound dressing compared to the control group without CNPs and modified gelatine. In vitro, the fabricated wound dressings were evaluated in terms of biocompatibility and the potential of the dressing to protect human dermal fibroblasts under oxidative stress and hypoxia conditions by an MTT assay. The presence of GA-g-GE led to remarkable protection of the cells against oxidative stress and hypoxia conditions. In vivo studies revealed that the incorporation of intrinsic ROS inhibition and oxygen-releasing properties could significantly accelerate the wound closure rate during the experimental period (7, 14, and 21 days). Additionally, histopathological investigations in terms of H&E and Masson's trichrome staining showed that the incorporation of the two mentioned capabilities remarkably facilitated the wound-healing process.

Advances in H2O2-supplying materials for tumor therapy: synthesis, classification, mechanisms, and applications

Hydrogen peroxide (H2O2) as a reactive oxygen species produced by cellular metabolism can be used in antitumor therapy. However, the concentration of intracellular H2O2 limits its application. Some materials could enhance the concentration of intracellular H2O2 to strengthen antitumor therapy. In this review, the recent advances in H2O2-supplying materials in terms of promoting intracellular H2O2 production and exogenous H2O2 supply are summarized. Then the mechanism of H2O2-supplying materials for tumor therapy is discussed from three aspects: reconstruction of the tumor hypoxia microenvironment, enhancement of oxidative stress, and the intrinsic anti-tumor ability of H2O2-supplying materials. In addition, the application of H2O2-supplying materials for tumor therapy is discussed. Finally, the future of H2O2-supplying materials is presented. This review aims to provide a novel idea for the application of H2O2-supplying materials in tumor therapy.

Hollow mesoporous calcium peroxide nanoparticles for drug-free tumor calcicoptosis therapy

Calcium ions (Ca2+) participate in the regulation of cellular apoptosis as a second messenger. Calcium overload, which refers to the abnormal elevation of intracellular Ca2+ concentration, is a factor that can lead to cell death. Here, based on the unique biological effects of Ca2+, hollow mesoporous calcium peroxide nanoparticles (HMCPN) were developed by a facile hydrolysis-precipitation method for drug-free tumor calcicoptosis therapy. The average pore size of the optimized HMCPN17 is 6.4 nm, and the surface area is 81.3 m2/g, which enables HMCPN17 with high drug loading capability. The Ca2+ release from HMCPN17 is much faster at pH 6.8 than that at pH 7.4, which can be ascribed to the acid-triggered conversion of HMCPN17 to Ca2+ and H2O2, indicating a pH-responsive decomposition behavior of HMCPN17. The high drug loading contents of doxorubicin (DOX) and/or sorafenib (SFN) indicate that HMCPN17 can be employed as a generic drug delivery system (DDS). The in vitro and in vivo results reinforce the high calcicoptosis therapeutic efficacy of tumors by our HMCPN17 without drug loading, which can be attributed to the efficient accumulation in tumors and the ability of H2O2 and Ca2+ production at acidic TME. Our HMCPN17 has broad application prospect for construction of multi-drug-loaded composite nanomaterials with diversified functions for the treatment of tumors. STATEMENT OF SIGNIFICANCE: The combination of hollow mesoporous nanomaterials and calcium peroxide nanoparticles has a wide range of applications in the synergistic treatment of tumors. In this study, hollow mesoporous calcium peroxide nanoparticles (HMCPN) were developed based on a simple hydrolysis-precipitation method for tumor calcicoptosis therapy without drug loading. The high drug loading contents of DOX and/or SFN indicate that our HMCPN can serve as a generic DDS. The experimental results demonstrated the high calcicoptosis therapeutic efficacy of HMCPN on tumors even without drug loading.

Bottle Nanomotors Amplify Tumor Oxidative Stress for Enhanced Calcium Overload/Chemodynamic Therapy

Developing multifunctional, stimuli-responsive nanomedicine is intriguing because it has the potential to effectively treat cancer. Yet, poor tumor penetration of nanodrugs results in limited antitumor efficacy. Herein, an oxygen-driven silicon-based nanomotor (Si-motor) loaded with MnO and CaO2 nanoparticles is developed, which can move in tumor microenvironment (TME) by the cascade reaction of CaO2 and MnO. Under acidic TME, CaO2 reacts with acid to release Ca2+ to induce mitochondrial damage and simultaneously produces O2 and H2O2, when the loaded MnO exerts Fenton-like activity to produce ·OH and O2 based on the produced H2O2. The generated O2 drives Si-motor forward, thus endowing active delivery capability of the formed motors in TME. Meanwhile, MnO with glutathione (GSH) depletion ability further prevents reactive oxygen species (ROS) from being destroyed. Such TME actuated Si-motor with enhanced cellular uptake and deep penetration provides amplification of synergistic oxidative stresscaused by intracellular Ca2 + overloading, GSH depletion induced by Mn2+, and Mn2+ mediated chemodynamic treatment (CDT), leading to excellent tumor cell death. The created nanomotor may offer an effective platform for active synergistic cancer treatment.

A coordinative modular assembly-constructed self-reinforced nano-therapeutic agent for effective antitumor-immune activation

Immunosuppressive microenvironment and poor immunogenicity are two stumbling blocks in anti-tumor immune activation. Tumor associated macrophages (TAMs) play crucial roles in immunosuppressive microenvironment, while immunogenic cell death (ICD) is a typical strategy to boost immunogenicity. Herein, we developed a coordinative modular assembly-based self-reinforced nanoparticle, (CaO2/TA)-(Fe3+/BSA) which integrated CaO2, Fe3+-tannic acid coordinated networks and albumin under the instruction of molecular dynamics simulation. (CaO2/TA)-(Fe3+/BSA) could significantly enhance Fenton reaction through Fe3+ self-reduction and H2O2 self-sufficiency, and simultaneously increased intracellular accumulation of Ca2+. The self-augmented Fenton reaction with sufficient reactive oxygen species effectively repolarized TAMs and elicited ICD with Ca2+ overload. Besides, (CaO2/TA)-(Fe3+/BSA) was confirmed to self-reinforce deep tumor drug delivery by "treatment-delivery" positive feedback based on gp60-mediated transcytosis and M2-like macrophages repolarization-mediated perfusion promotion. Resultantly, (CaO2/TA)-(Fe3+/BSA) effectively alleviated immunosuppression, provoked local and systemic immune response and potentiated anti-PD-1 antibody therapy. Our strategy highlights a facile and controllable approach to construct penetrated effective antitumor nano-immunotherapeutic agent.

Oxygen tension regulating hydrogels for vascularization and osteogenesis via sequential activation of HIF-1α and ERK1/2 signaling pathways in bone regeneration

Angiogenesis plays a crucial role in bone regeneration. Hypoxia is a driving force of angiogenesis at the initial stage of tissue repair. The hypoxic microenvironment could activate the hypoxia-inducible factor (HIF)-1α signaling pathway in cells, thereby enhancing the proliferation, migration and pro-angiogenic functions of stem cells. However, long-term chronic hypoxia could inhibit osteogenic differentiation and even lead to apoptosis. Therefore, shutdown of the HIF-1α signaling pathway and providing oxygen at later stage probably facilitate osteogenic differentiation and bone regeneration. Herein, an oxygen tension regulating hydrogel that sequentially activate and deactivate the HIF-1α signaling pathway were prepared in this study. Its effect and mechanism on stem cell differentiation were investigated both in vitro and in vivo. We proposed a gelatin-based hydrogel capable of sequentially delivering a hypoxic inducer (copper ions) and oxygen generator (calcium peroxide). The copper ions released from the hydrogels significantly enhanced cell viability and VEGF secretion of BMSCs via upregulating HIF-1α expression and facilitating its translocation into the nucleus. Additionally, calcium peroxide promoted alkaline phosphatase activity, osteopontin secretion, and calcium deposition through the activation of ERK1/2. Both Cu2+ and calcium peroxide demonstrated osteogenic promotion individually, while their synergistic effect within the hydrogels led to a superior osteogenic effect by potentially activating the HIF-1α and ERK1/2 signaling pathways.

Polydopamine Nanocarriers with Cascade-Activated Nitric Oxide Release Combined Photothermal Activity for the Therapy of Drug-Resistant Bacterial Infections

Antibiotic abuse leads to increased bacterial resistance, and the surviving planktonic bacteria aggregate and secrete extracellular polymers to form biofilms. Conventional antibacterial agents find it difficult to penetrate the biofilm, remove the bacteria wrapped in it, and produce an excellent therapeutic effect. In this study, a dual pH- and NIR-responsive nanocomposite (A-Ca@PDA) was developed to remove drug-resistant bacteria through a cascade of catalytic nitric oxide (NO) release and photothermal clearance. NO can melt in the outer package of the biofilm, facilitating the nanocomposites to have better permeability. Thermal therapy further inhibits the growth of planktonic bacteria. The locally generated high temperature and the burst release of NO together aggravate the biofilm collapse and bacterial death after NIR irradiation. The nanocomposites achieved a remarkable photothermal conversion efficiency of 47.5%, thereby exhibiting significant advancements in energy conversion. The nanocomposites exhibited remarkable efficacy in inhibiting multidrug-resistant (MDR) Escherichia coli and MDR Staphylococcus aureus, thus achieving an inhibition rate of >90%. Moreover, these nanocomposites significantly improved the wound-healing process in the MDR S. aureus-infected mice. Thus, this novel nanocomposite offers a novel strategy to combat drug-resistant bacterial infections.

A ROS storm generating nanocomposite for enhanced chemodynamic therapy through H2O2 self-supply, GSH depletion and calcium overload

Catalytic generation of toxic hydroxyl radicals (˙OH) from hydrogen peroxide (H2O2) is an effective strategy for tumor treatment in chemodynamic therapy (CDT). However, the intrinsic features of the microenvironment in solid tumors, characterized by limited H2O2 and overexpressed glutathione (GSH), severely impede the accumulation of intracellular ˙OH, posing significant challenges. To circumvent these critical issues, in this work, a CaO2-based multifunctional nanocomposite with a surface coating of Cu2+ and L-buthionine sulfoximine (BSO) (named CaO2@Cu-BSO) is designed for enhanced CDT. Taking advantage of the weakly acidic environment of the tumor, the nanocomposite gradually disintegrates, and the exposed CaO2 nanoparticles subsequently decompose to produce H2O2, alleviating the insufficient supply of endogenous H2O2 in the tumor microenvironment (TME). Furthermore, Cu2+ detached from the surface of CaO2 is reduced by H2O2 and GSH to Cu+ and ROS. Then, Cu+ catalyzes H2O2 to generate highly cytotoxic ˙OH and Cu2+, forming a cyclic catalysis effect for effective CDT. Meanwhile, GSH is depleted by Cu2+ ions to eliminate possible ˙OH scavenging. In addition, the decomposition of CaO2 by TME releases a large amount of free Ca2+, resulting in the accumulation and overload of Ca2+ and mitochondrial damage in tumor cells, further improving CDT efficacy and accelerating tumor apoptosis. Besides, BSO, a molecular inhibitor, decreases GSH production by blocking γ-glutamyl cysteine synthetase. Together, this strategy allows for enhanced CDT efficiency via a ROS storm generation strategy in tumor therapy. The experimental results confirm and demonstrate the satisfactory tumor inhibition effect both in vitro and in vivo.

In Situ Mitochondrial Biomineralization for Drug-Free Cancer Therapy

The common clinical chemotherapy often brings serious side effects to patients, mainly due to the off-target and leakage of toxic drugs. However, this is fatal for some specific clinical tumors, such as brain tumors and neuroma. This study performs a drug-free approach by encapsulating black phosphorus (BP) and calcium peroxide (CaO2) in liposomes with surface-modified triphenylphosphonium (BCLT) to develop mitochondria targeting calcification for cancer therapy without damaging normal cells. BCLT preferentially accumulates inside tumor mitochondria and then is activated by near-infrared (NIR) laser irradiation to produce abundant PO4 3- and Ca2+ to accelerate in situ mitochondrial mineralization, leading to mitochondrial dysfunction and cancer cell death. More importantly, both PO4 3- and Ca2+ are essential components of metabolism in the body, and random gradient diffusion or premature leakage does not cause damage to adjacent normal cells. This achievement promises to be an alternative to conventional chemotherapy in clinical practice for many specific tumor types.

Multi-level Reactive Oxygen Species Amplifier to Enhance Photo-/Chemo-Dynamic/Ca2+ Overload Synergistic Therapy

Reactive oxygen species (ROS)-involved photodynamic therapy (PDT) and chemodynamic therapy (CDT) hold great promise for tumor treatment. However, hypoxia, insufficient H2O2, and overexpressed glutathione (GSH) in the tumor microenvironment (TME) hinder ROS generation significantly. Herein, we reported CaO2@Cu-TCPP/CUR with O2/H2O2/Ca2+ self-supply and GSH depletion for enhanced PDT/CDT and Ca2+ overload synergistic therapy. CaO2 nanospheres were first prepared and used as templates for guiding the coordination between the carboxyl of tetra-(4-carboxyphenyl)porphine (TCPP) and Cu2+ ions as hollow CaO2@Cu-TCPP, which facilitated GSH-activated TCPP-based PDT and Cu+-mediated CDT. The hollow structure was then loaded with curcumin (CUR) to form CaO2@Cu-TCPP/CUR composites. Cu-TCPP prevented degradation of CaO2, while Cu2+ ions reacted with GSH to deplete GSH, produce Cu+ ions, and release TCPP, CaO2, and CUR. CaO2 reacted with H2O to generate O2, H2O2, and Ca2+ to achieve O2/H2O2/Ca2+ self-supply for TCPP-based PDT, Cu+-mediated CDT, and CUR-enhanced Ca2+ overload therapy. Thus, this multilevel ROS amplifier enhances synergistic therapy with fewer side effects and drug resistance.

Aggregation-Induced Emission Photosensitizer-Engineered Anticancer Nanomedicine for Synergistic Chemo/Chemodynamic/Photodynamic Therapy

Photodynamic therapy (PDT) with aggregation-induced emission (AIE) photosensitizers (PSs) is a promising therapeutic strategy to achieve better anticancer results. However, eradicating solid tumors completely by PDT alone can be difficult owing to the inherent drawbacks of this treatment, and the combination of PDT with other therapeutic modalities provides opportunities to achieve cooperative enhancement interactions among various treatments. Herein, this work presents the construction of a biocompatible nanocomposite, namely CaO2@DOX@ZIF@ASQ, featuring light-responsive reactive oxygen species (ROS) generation and tumor-targeting oxygen and hydrogen peroxide discharge, as well as controlled doxorubicin (DOX) and copper ion release, thus allowing the combined PDT/CT/CDT effect by AIE PS-enhanced PDT, DOX-based chemotherapy (CT), and copper-involved Fenton-like reaction-driven chemodynamic therapy (CDT). In vitro and in vivo studies verify that the generation of both ROS and O2 by this nanomedicine, stimulated by light, exhibits superior anticancer efficacy, alleviating tumor hypoxia and achieving synergistic PDT/CT/CDT therapeutic effect. This multifunctional nanomedicine remarkably suppresses the tumor growth with minimized systemic toxicity, providing a new strategy for constructing multimodal PDT/CT/CDT therapeutic systems to overcome hypoxia limitations, and potentially increase the antitumor efficacy at lower doses of PSs and chemotherapeutic drugs, thus minimizing potential toxicity to non-malignant tissues.

H2O2 self-supplying and GSH-depleting nanosystem for amplified NIR mediated-chemodynamic therapy of MRSA biofilm-associated infections

Reactive oxygen species (ROS) has emerged as potent therapeutic agents for biofilm-associated bacterial infections. Chemodynamic therapy (CDT), involving the generation of high-energy ROS, displays great potential in the therapy of bacterial infections. However, challenges such as insufficient hydrogen peroxide (H2O2) and over-expressed glutathione (GSH) levels within the microenvironment of bacterial biofilms severely limit the antibacterial efficacy of CDT. Herein, we have developed a multifunctional nanoplatform (CuS@CaO2@Dex) by integrating copper sulfide (CuS) and calcium peroxide (CaO2) into dextran (Dex)-coated nanoparticles. This innovative platform enhanced ROS generation for highly efficient biofilm elimination by simultaneously supplying H2O2 and depleting GSH. The Dex-coating facilitated the penetrability of CuS@CaO2@Dex into biofilms, while CaO2 generated a substantial amount of H2O2 in the acidic biofilm microenvironment. CuS, through a Fenton-like reaction, catalyzed the conversion of self-supplied H2O2 into hydroxyl radicals (•OH) and consumed the overexpressed GSH. Additionally, the incorporation of near-infrared II (NIR II) laser irradiation enhanced the photothermal properties of CuS, improving the catalytic efficiency of the Fenton-like reaction for enhanced antibacterial effects. In vivo experiments have demonstrated that CuS@CaO2@Dex exhibited remarkable antibacterial and antibiofilm efficacy, exceptional wound healing capabilities, and notable biosafety. In summary, the Dex-coated nanoplatform proposed in this study, with its self-sterilization capability through ROS, holds significant potential for future biomedical applications.

Nanoengineered oxygen-releasing polymeric scaffold with sustained release of dexamethasone for bone regeneration

Maintaining the continuous oxygen supply and proper cell growth before blood vessel ingrowth at the bone defect site are considerably significant issues in bone regeneration. Oxygen-producing scaffolds can supply oxygen and avoid hypoxia leading to expedited bone regeneration. Herein, first oxygen-producing calcium peroxide nanoparticles (CPO NPs) are synthesized, and subsequently, the various amounts of synthesized CPO NPs (0.1, 0.5, and 1 wt/v%) loaded in the scaffold composite, which is developed by simple physical blending of chitosan (CS) and polycaprolactone (PCL) polymers. To deliver the synergistic therapeutic effect, dexamethasone (DEX), known for its potential anti-inflammatory and osteogenic properties, is loaded into the nanocomposite scaffolds. The extensive physicochemical characterizations of nanocomposite scaffolds confirm the successful loading of CPO NPs, adequate porous morphology, pore size, hydrophilicity, and biodegradability.In vitro, biological studies support the antibacterial, hemocompatible, and cytocompatible (MG-63 and MC3T3-E1 cells) nature of the material when tested on respective cells. Field emission scanning electron microscopy and energy-dispersive x-ray spectroscopy confirm the successful biomineralization of the scaffolds. Scaffolds also exhibit the sustained release of DEX and efficient protein adsorption. This study revealed that a nanoengineered scaffold loaded with CPO NPs (PCL/CS/DEX/CPO 3) is a suitable candidate for bone tissue regeneration.

A TME-activated nano-catalyst for triple synergistic therapy of colorectal cancer

Colorectal cancer cells are highly heterogeneous and exhibit various drug resistances, making personalized treatment necessary. This typically involves a combination of different treatment modalities such as surgery, radiation, and chemotherapy to increase patient survival. Inspired by this, synergistic therapy, which combines multiple modalities into a single nanotherapeutic drug, shows promise in treating cancer. In this study, a nano-catalyst based on calcium peroxide (CaO2) and the chemotherapeutic drug doxorubicin hydrochloride (DOX) co-loaded into HPB nanoparticles (HPB@CaO2/DOX-PAA) was developed to achieve synergistic cancer treatment through chemodynamic/chemo/photothermal (CDT/CT/PTT) mechanisms. After being endocytosed by cancer cells, the nano-catalyst decomposes, releasing cargo. During near-infrared light irradiation, HPB induces a photothermal effect, DOX exhibits significant RNA and DNA destruction capabilities, meanwhile CaO2 produces a large amount of H2O2 in the moderately acidic TME, which combines with Fe2+ ions derived from HPB to form the highly toxic •OH in a Fenton-like reaction, enhancing the chemodynamic treatment. Assays conducted ex vivo and in vivo have exhibited the efficacy of this triple synergistic therapeutic regimen, indicating its potential clinical application.

A double-gain theranostic nanoplatform based on self-supplying H2O2 nanocomposites for synergistic chemodynamic/gas therapy

Chemodynamic therapy (CDT) based on hydroxyl radicals (•OH) to suppress tumor cells is a promising strategy due to its efficacy and safety. Nevertheless, in tumor cells, CDT still faces challenges such as insufficient •OH and weak killing effect of tumor cells under physiological conditions due to inadequate amounts of endogenous hydrogen peroxide (H2O2) and heightened glutathione expression. These challenges limit the therapeutic potential of CDT. To improve the effects of CDT, combination treatment strategies have been developed. Here, we report a rationally designed nanocomposite (CaO2@Cu-LA) with self-supplying H2O2 ability from calcium peroxide, and nitric oxide (NO) generation ability from l-arginine. NO molecules not only exhibit a strong killing effect, but also have the potential to transfer into the more cytotoxic substance peroxynitrite anion by reacting with reactive oxygen species. The results showed that CaO2@Cu-LA could significantly suppress tumor growth by increasing •OH radicals and NO molecules. Taken together, the strategy developed here provides a good application foreground to yield a remarkable synergistic antitumor effect of CDT and NO gas therapy.

Guiding the Path to Healing: CuO2 -Laden Nanocomposite Membrane for Diabetic Wound Treatment

Diabetic chronic wounds pose significant clinical challenges due to their characteristic features of impaired extracellular matrix (ECM) function, diminished angiogenesis, chronic inflammation, and increased susceptibility to infection. To tackle these challenges and provide a comprehensive therapeutic approach for diabetic wounds, the first coaxial electrospun nanocomposite membrane is developed that incorporates multifunctional copper peroxide nanoparticles (n-CuO2 ). The membrane's nanofiber possesses a unique "core/sheath" structure consisting of n-CuO2 +PVP (Polyvinylpyrrolidone)/PCL (Polycaprolactone) composite sheath and a PCL core. When exposed to the wound's moist environment, PVP within the sheath gradually disintegrates, releasing the embedded n-CuO2 . Under a weakly acidic microenvironment (typically diabetic and infected wounds), n-CuO2 decomposes to release H2 O2 and Cu2+ ions and subsequently produce ·OH through chemodynamic reactions. This enables the anti-bacterial activity mediated by reactive oxygen species (ROS), suppressing the inflammation while enhancing angiogenesis. At the same time, the dissolution of PVP unveils unique nano-grooved surface patterns on the nanofibers, providing desirable cell-guiding function required for accelerated skin regeneration. Through meticulous material selection and design, this study pioneers the development of functional nanocomposites for multi-modal wound therapy, which holds great promise in guiding the path to healing for diabetic wounds.

CaO2-Cu2O micromotors accelerate infected wound healing through antibacterial functions, hemostasis, improved cell migration, and inflammatory regulation

During the wound tissue healing process, the relatively weak driving forces of tissue barriers and concentration gradients lead to a slow and inefficient penetration of bioactive substances into the wound area, consequently showing an impact on the effectiveness of deep wound healing. To overcome these challenges, we constructed biocompatible CaO2-Cu2O "micromotors". These micromotors reacted with the fluids at the wound site, releasing oxygen bubbles and propelling particles deep into the wound tissue. In vitro experimental results revealed that these micromotors not only exhibited antibacterial and hemostatic functions but also facilitated the migration of dermal fibroblasts and vascular endothelial cells, while modulating the inflammatory microenvironment. A methicillin-resistant Staphylococcus aureus infected full-thickness-wound model was created in rats, in which CaO2-Cu2O micromotors markedly expedited the wound healing process. Specifically, CaO2-Cu2O provided a sterile microenvironment for wounds and increased the amounts of M1-type macrophages during infection and inflammation. During the proliferation and remodeling stages, the amount of M1 macrophages gradually decreased, while the amount of M2 macrophages increased, and CaO2-Cu2O did not prolong the inflammatory period. Furthermore, the introduction of a regenerated silk fibroin (RSF) film on the wound surface successfully enhanced the therapeutic effects of CaO2-Cu2O against the infected wound. The combined application of oxygen-producing CaO2-Cu2O micromotors and a RSF film demonstrates significant therapeutic potential and emerges as a promising candidate for the treatment of infected wounds.

Engineering Crystallinity Gradients for Tailored CaO2 Nanostructures: Enabling Alkalinity-Reinforced Anticancer Activity with Minimized Ca2+/H2O2 Production

CaO2 nanoparticles (CNPs) can produce toxic Ca2+ and H2O2 under acidic pH, which accounts for their intrinsic anticancer activity but at the same time raises safety concerns upon systemic exposure. Simultaneously realizing minimized Ca2+/H2O2 production and enhanced anticancer activity poses a dilemma. Herein, we introduce a "crystallinity gradient-based selective etching" (CGSE) strategy, which is realized by creating a crystallinity gradient in a CNP formed by self-assembled nanocrystals. The nanocrystals distributed in the outer layer have a higher crystallinity and thus are chemically more robust than those distributed in the inner layer, which can be selectively etched. CGSE not only leads to CNPs with tailored single- and double-shell hollow structures and metal-doped compositions but more surprisingly enables significantly enhanced anticancer activity as well as tumor growth inhibition under limited Ca2+/H2O2 production, which is attributed to an alkalinity-reinforced lysosome-dependent cell death pathway.

Metallic elements combine with herbal compounds upload in microneedles to promote wound healing: a review

Wound healing is a dynamic and complex restorative process, and traditional dressings reduce their therapeutic effectiveness due to the accumulation of drugs in the cuticle. As a novel drug delivery system, microneedles (MNs) can overcome the defect and deliver drugs to the deeper layers of the skin. As the core of the microneedle system, loaded drugs exert a significant influence on the therapeutic efficacy of MNs. Metallic elements and herbal compounds have been widely used in wound treatment for their ability to accelerate the healing process. Metallic elements primarily serve as antimicrobial agents and facilitate the enhancement of cell proliferation. Whereas various herbal compounds act on different targets in the inflammatory, proliferative, and remodeling phases of wound healing. The interaction between the two drugs forms nanoparticles (NPs) and metal-organic frameworks (MOFs), reducing the toxicity of the metallic elements and increasing the therapeutic effect. This article summarizes recent trends in the development of MNs made of metallic elements and herbal compounds for wound healing, describes their advantages in wound treatment, and provides a reference for the development of future MNs.

pH Switchable Nanozyme Platform for Healing Skin Tumor Wound Infected with Drug-Resistant Bacteria

Nanozymes capable of generating reactive oxygen species have recently emerged as promising treatments for wounds infected with drug-resistant bacteria, possessing a reduced possibility of inducing resistance. However, the therapeutic effect is limited by a shortage of endogenous oxy-substrates and undesirable off-target biotoxicity. Herein, a ferrocenyl coordination polymer (FeCP) nanozyme, featuring pH switchable peroxidase (POD)- and catalase (CAT)-like activity is incorporated with indocyanine green (ICG) and calcium peroxide (CaO2 ) to fabricate an H2 O2 /O2 self-supplying system (FeCP/ICG@CaO2 ) for precise treatment of bacterial infections. At the wound site, CaO2 reacts with water to generate H2 O2 and O2 . Acting as a POD mimic under an acidic bacterial microenvironment, FeCP catalyzes H2 O2 into hydroxyl radicals to prevent infection. However, FeCP switches to CAT-like activity in neutral tissue, decomposing H2 O2 into H2 O and O2 to prevent oxidative damage and facilitate wound healing. Additionally, FeCP/ICG@CaO2 shows photothermal therapy capability, as ICG can emit heat under near-infrared laser irradiation. This heat assists FeCP in fully exerting its enzyme-like activity. Thus, this system achieves an antibacterial efficiency of 99.8% in vitro for drug-resistant bacteria, and effectively overcomes the main limitations of nanozyme-based treatment assays, resulting in satisfactory therapeutic effects in repairing normal and special skin tumor wounds infected with drug-resistant bacteria.

CaO2nanomedicines: a review of their emerging roles in cancer therapy

Metal peroxide-based nanomedicines have emerged as promising theranostic agents for cancer due to their multifunctional properties, including the generation of bioactive small molecules such as metal ions, H2O2, O2, and OH-. Among these metal peroxides, calcium peroxide (CaO2) nanomedicines have attracted significant attention due to their facile synthesis and good biocompatibility. CaO2nanoparticles have been explored for cancer treatment through three main mechanisms: (1) the release of O2, which helps alleviate tumor hypoxia and enhances oxygen-dependent therapies such as chemotherapy, photodynamic therapy, and immunotherapy; (2) the generation of H2O2, a precursor for ·OH generation, which enables cancer chemodynamic therapy; and (3) the release of Ca2+ions, which induce calcium overload and promote cell apoptosis (called ion-interference therapy). This review provides a comprehensive summary of recent examples of CaO2nanoparticle-based cancer therapeutic strategies, as well as discusses the challenges and future directions in the development of CaO2nanomedicines for cancer treatment.

A novel strategy to enhance photocatalytic killing of foodborne pathogenic bacteria by modification of non-metallic monomeric black phosphorus with Elaeagnus mollis polysaccharides

New antibacterial agents are needed to overcome the challenges of microbial food contamination. In this study, we investigated the potential of Elaeagnus mollis polysaccharide (EMP) to modify black phosphorus (BP) for use as a bactericide for foodborne pathogenic bacteria. The resulting compound (EMP-BP) displayed enhanced stability and activity compared with BP. EMP-BP exhibited an increased antibacterial activity (bactericidal efficiency of 99.999 % after 60 min of light exposure) compared to EMP and BP. Further studies revealed that photocatalytically generated reactive oxygen species (ROS) and active polysaccharides acted collectively on the cell membrane, leading to cell deformation and death. Furthermore, EMP-BP inhibited biofilm formation and reduced expression of virulence factors of Staphylococcus aureus, and material hemolysis and cytotoxicity tests prove that the material had good biocompatibility. In addition, bacteria treated with EMP-BP remained highly sensitive to antibiotics and did not develop significant resistance. In summary, we report an environmentally friendly method for controlling pathogenic foodborne bacteria that is efficient and apparently safe.

Injectable Antioxidant and Oxygen-Releasing Lignin Composites to Promote Wound Healing

The application of engineered biomaterials for wound healing has been pursued since the beginning of tissue engineering. Here, we attempt to apply functionalized lignin to confer antioxidation to the extracellular microenvironments of wounds and to deliver oxygen from the dissociation of calcium peroxide for enhanced vascularization and healing responses without eliciting inflammatory responses. Elemental analysis showed 17 times higher quantity of calcium in the oxygen-releasing nanoparticles. Lignin composites including the oxygen-generating nanoparticles released around 700 ppm oxygen per day at least for 7 days. By modulating the concentration of the methacrylated gelatin, we were able to maintain the injectability of lignin composite precursors and the stiffness of lignin composites suitable for wound healing after photo-cross-linking. In situ formation of lignin composites with the oxygen-releasing nanoparticles enhanced the rate of tissue granulation, the formation of blood vessels, and the infiltration of α-smooth muscle actin⁺ fibroblasts into the wounds over 7 days. At 28 days after surgery, the lignin composite with oxygen-generating nanoparticles remodeled the collagen architecture, resembling the basket-weave pattern of unwounded collagen with minimal scar formation. Thus, our study shows the potential of functionalized lignin for wound-healing applications requiring balanced antioxidation and controlled release of oxygen for enhanced tissue granulation, vascularization, and maturation of collagen.

Jamil SNA, Choong TSY, Mat Azmi ID, Abdul Romli NA, Abdullah LC, Chiang PC, Li F. Synthesis of Calcium Peroxide Nanoparticles with Starch as a Stabilizer for the Degradation of Organic Dye in an Aqueous Solution

One of the most significant environmental problems in the world is the massive release of dye wastewater from the dyeing industry. Therefore, the treatment of dyes effluents has received significant attention from researchers in recent years. Calcium peroxide (CP) from the group of alkaline earth metal peroxides acts as an oxidizing agent for the degradation of organic dyes in water. It is known that the commercially available CP has a relatively large particle size, which makes the reaction rate for pollution degradation relatively slow. Therefore, in this study, starch, a non-toxic, biodegradable and biocompatible biopolymer, was used as a stabilizer for synthesizing calcium peroxide nanoparticles (Starch@CPnps). The Starch@CPnps were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET), dynamic light scattering (DLS), thermogravimetric analysis (TGA), energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). The degradation of organic dyes, methylene blue (MB), using Starch@CPnps as a novel oxidant was studied using three different parameters: initial pH of the MB solution, calcium peroxide initial dosage and contact time. The degradation of the MB dye was carried out via a Fenton reaction, and the degradation efficiency of Starch@CPnps was successfully achieved up to 99%. This study shows that the potential application of starch as a stabilizer can reduce the size of the nanoparticles as it prevents the agglomeration of the nanoparticles during synthesis.

Ultrasound activatable microneedles for bilaterally augmented sono-chemodynamic and sonothermal antibacterial therapy

Chemodynamic therapy (CDT) employs Fenton catalysts to kill bacteria by converting hydrogen peroxide (H₂O₂) into toxic hydroxyl radical (•OH). Among them, Fenton-type metal peroxide nanoparticles fascinate nanomaterials with intriguing physiochemical properties, but research on this antibacterial agent is still in its infancy. Herein, a distinct CuO₂/TiO₂ heterostructure constituted of ultrasmall copper peroxide (CuO₂) nanoclusters and sonosensitized ultrathin oxygen vacancy-rich porous titanium oxide (OV-TiO₂) nanosheets was developed and was incorporated into microneedles for bilaterally augmented sono-chemodynamic and sonothermal antibacterial therapy. Engineering CuO₂ nanoclusters on the surface of TiO₂ nanosheets not only endows the Fenton catalytic activity for sono-chemodynamic therapy (SCDT), but also improves the sonodynamic and sonothermal performance of TiO₂ by narrowing the bandgap of TiO₂ and suppressing the recombination of electron-hole pairs. The high efficacy of this CuO₂/TiO₂ integrated microneedle (CTMN) patch was systematically demonstrated both in vitro and in vivo with the eliminating rate >99.9999% against multidrug resistant (MDR) pathogens in 5 min as well as accelerated wound tissue healing. This work highlights a promisingly new and efficient strategy for the development of sonosensitive and chemoreactive nanomedicine for non-antibiotic therapies. STATEMENT OF SIGNIFICANCE: Feton-type metal peroxides, a novel nanomaterial with self-supplied oxygen and hydrogen peroxide, can achieve effective antimicrobial activity in vitro. However, there is a lack of effective nanomaterial delivery systems and suitable means for in vivo activation/enhancement of antimicrobial activity during bacterial infected skin wound treatment. In this study, we designed and prepared efficient ultrasound activable microneedles that effectively addressed the deficiencies mentioned above and established a new paradigm for efficient utilization of metal peroxide nanomaterials and ultrasound based strategies. Noticeably, copper peroxide nanoclusters/oxygen vacancy-rich porous titanium oxide nanosheets (CuO₂/TiO₂) integrated microneedle (CTMN) patch combines advantages of both sono-chemodynamic and sonothermal antibacterial therapy, achieving one of the most instant and effective antibacterial efficacy (>99.9999% in 5 min) in vivo reported till now.

Carrier-free nanoprodrug for p53-mutated tumor therapy via concurrent delivery of zinc-manganese dual ions and ROS

Human cancers typically express a high level of tumor-promoting mutant p53 protein (Mutp53) with a minimal level of tumor-suppressing wild-type p53 protein (WTp53). In this regard, inducing Mutp53 degradation while activating WTp53 is a viable strategy for precise anti-tumor therapy. Herein, a new carrier-free nanoprodrug (i.e., Mn-ZnO₂ nanoparticles) was developed for concurrent delivery of dual Zn-Mn ions and reactive oxygen species (ROS) within tumor to regulate the p53 protein for high anti-tumor efficacy. In response to the mild tumor acidic environment, the released Zn²⁺ and H₂O₂ from Mn-ZnO₂ NPs induced ubiquitination-mediated proteasomal degradation of Mutp53, while the liberative Mn²⁺ and increased ROS level activated the ATM-p53-Bax pathway to elevate WTp53 level. Both in vitro and in vivo results demonstrated that pH-responsive decomposition of Mn-ZnO₂ NPs could effectively elevate the intracellular dual Zn-Mn ions and ROS level and subsequently generate the cytotoxic hydroxyl radical (•OH) through the Fenton-like reaction. With the integration of multiple functions (i.e., carrier-free ion and ROS delivery, tumor accumulation, p53 protein modulation, toxic •OH generation, and pH-activated MRI contrast) in a single nanosystem, Mn-ZnO₂ NPs demonstrate its superiority as a promising nanotherapeutics for p53-mutated tumor therapy.

A Self-Reinforcing Nanoplatform for Highly Effective Synergistic Targeted Combinatary Calcium-Overload and Photodynamic Therapy of Cancer

While calcium-overload-mediated therapy (COMT) is a promising but largely untapped therapeutic strategy, combinatory therapy greatly boosts treatment outcomes with integrated merits of different therapies. Herein, a BPQD@CaO₂ -PEG-GPC3Ab nanoplatform is formulated by integrating calcium peroxide (CaO₂ ) and black phosphorus quantum dot (BPQD, photosensitizer) with active-targeting glypican-3 antibody (GPC3Ab), for combinatory photodynamic therapy (PDT) and COMT in response to acidic pH and near-infrared (NIR) light, wherein CaO₂ serves as the reservoir of calcium ions (Ca²⁺ ) and hydrogen peroxide (H₂ O₂ ). Navigated by GPC3Ab to tumor cells at acidic pH, the nanoparticle disassembles to CaO₂ and BPQD; CaO₂ produces COMT Ca²⁺ and H₂ O₂ , while H₂ O₂ makes oxygen (O₂ ) to promote PDT; under NIR irradiation BPQD facilitates not only the conversion of O₂ to singlet oxygen (¹ O₂ ) for PDT, but also moderate hyperthermia to accelerate NP dissociation to CaO₂ and BPQD, and conversions of CaO₂ to Ca²⁺ and H₂ O₂ , and H₂ O₂ to O₂ , to enhance both COMT and PDT. After supplementary ionomycin treatment to induce intracellular Ca²⁺ bursts, the multimodal therapeutics strikingly induce hepatocellular carcinoma apoptosis, likely through the activation of the calpains and caspases 12, 9, and 3, up-regulation of Bax and down-regulation of Bcl-2 proteins. This nanoplatform enables a mutually-amplifying and self-reinforcing synergistic therapy.

Stimuli-Activable Metal-Bearing Nanomaterials and Precise On-Demand Antibacterial Strategies

Bacterial infections remain the leading cause of death worldwide today. The emergence of antibiotic resistance has urged the development of alternative antibacterial technologies to complement or replace traditional antibiotic treatments. In this regard, metal nanomaterials have attracted great attention for their controllable antibacterial functions that are less prone to resistance. This review discusses a particular family of stimuli-activable metal-bearing nanomaterials (denoted as SAMNs) and the associated on-demand antibacterial strategies. The various SAMN-enabled antibacterial strategies stem from basic light and magnet activation, with the addition of bacterial microenvironment responsiveness and/or bacteria-targeting selectivity and therefore offer higher spatiotemporal controllability. The discussion focuses on nanomaterial design principles, antibacterial mechanisms, and antibacterial performance, as well as emerging applications that desire on-demand and selective activation (i.e., medical antibacterial treatments, surface anti-biofilm, water disinfection, and wearable antibacterial materials). The review concludes with the authors' perspectives on the challenges and future directions for developing industrial translatable next-generation antibacterial strategies.

Nanoscale CaO2 materials for synergistic transarterial chemoembolization in a VX2 orthotopic rabbit liver cancer model

Transcatheter arterial chemoembolization (TACE) is extensively used in the treatment of hepatocellular carcinoma (HCC), but its efficacy is usually limited to secondary tumor hypoxia and other progressive exacerbation of the abnormal tumor microenvironment (TME). Herein, we synthesized polyvinyl pyrrolidone (PVP)-coated CaO₂ nanoparticles (CaO₂ NPs) and applied them as a synergistic agent to improve the antitumor efficacy of TACE. After injection into the tumor, CaO₂ NPs reacted with water to generate abundant oxygen, hydroxyl ions (OH^-), and calcium ions (Ca²⁺), thereby relieving tumor hypoxia, neutralizing acid, and overloading Ca²⁺ to mediate antitumor effects. Moreover, the effect of chemotherapeutic drugs within the TACE was improved due to the modulated TME. CaO₂ NPs efficiently regulated the TME and improved the antitumor effect of doxorubicin under hypoxia conditions in vitro. Compared to other groups, the TACE+CaO₂ NPs group achieved the lowest tumor growth rate, highest tumor necrosis rate, lowest expression of histological markers associated with hypoxia and angiogenesis (HIF-α, VEGF, and CD31), and highest CD8⁺ T cell recruitment in vivo. Thus, these findings demonstrated that CaO₂ NPs provide synergy for TACE therapy in the VX2 orthotopic rabbit liver cancer model, suggesting that they have a potential broad clinical application. STATEMENT OF SIGNIFICANCE: The efficacy of transcatheter arterial chemoembolization (TACE) for treatment of hepatocellular carcinoma is usually limited to secondary tumor hypoxia and other progressive exacerbation of the abnormal tumor microenvironment (TME). To address this issue, we synthesized CaO₂ nanoparticles (CaO₂ NP_S) which would react with water to generate abundant oxygen, hydroxyl ions (OH^-), and calcium ions (Ca²⁺), thereby relieving tumor hypoxia, neutralizing the acidic TME, and inducing Ca²⁺ overloading. The efficacy of CaO₂ NPs in combination with TACE was investigated in an orthotopic rabbit liver cancer model, and the results showed the great synergetic antitumor effect of TACE and CaO₂ NPs.

Multifunctional Hollow MnO2 @Porphyrin@Bromelain Nanoplatform for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has been showing great potential in cancer treatment. However, the efficacy of PDT is always limited by the intrinsic hypoxic tumor microenvironment (TME) and the low accumulation efficiency of photosensitizers in tumors. To address the issue, a multifunctional hollow multilayer nanoplatform (H-MnO₂ @TPyP@Bro) comprising manganese dioxide, porphyrin (TPyP) and bromelain (Bro), is developed for enhanced photodynamic therapy. MnO₂ catalyzes the intracellular hydrogen peroxide (H₂ O₂ ) to produce oxygen (O₂ ), reversing the hypoxic TME in vivo. The generated O₂ is converted into singlet oxygen (¹ O₂ ) by the TPyP shell under near-infrared light, which can inhibit tumor proliferation. Meanwhile, the Bro can digest collagen in the extracellular matrix around the tumor, and can promote the accumulation of H-MnO₂ @TPyP@Bro in the deeper tumor tissue, further improving the therapeutic effect of PDT. In addition, MnO₂ can react with the overexpressed glutathione in TME to release Mn²⁺ . Consequently, Mn²⁺ not only induces chemo-dynamic therapy based on Fenton reaction by converting H₂ O₂ into hydroxyl radicals, but also activates the Mn²⁺ -based magnetic resonance imaging. Therefore, the developed H-MnO₂ @TPyP@Bro nanoplatform can effectively modulate the unfavorable TME and overcome the limitations of conventional PDT for cancer diagnostic and therapeutic.

Self-reinforcement hydrogel with sustainable oxygen-supply for enhanced cell ingrowth and potential tissue regeneration

Hydrogels composed of natural biopolymers are attractive for tissue regeneration applications owing to their advantages such as biocompatibility and ease of administration, etc.. Yet, the low oxygen level and the crosslinked network inside bulk hydrogels, as well as the hypoxic status in defect areas, hamper cell viability, function, and eventual tissue repair. Herein, based on Ca²⁺-crosslinked alginate hydrogel, oxygen-generating calcium peroxide (CaO₂) was introduced, which could provide a dynamic crosslinking alongside the CaO₂ decomposition. Compared to the CaCl₂-crosslinked alginate hydrogel, bone marrow mesenchymal stromal cells cultured with CaO₂-contained system displayed remarkably improved biological behaviors. Furthermore, in vivo evaluations were carried out on a subcutaneous implantation in rats, and the results demonstrated the importance of the local oxygen availability in a series of crucial events for tissue regeneration, such as activating cell viability, migration, angiogenesis, and osteogenesis. In summary, the obtained Ca²⁺-crosslinked alginate hydrogel achieved a better microenvironment for cell ingrowth and potential tissue regeneration as the CaCl₂ crosslinker being replaced by oxygen-generating CaO₂ nanoparticles, due to its contribution in remedying the local hypoxic condition, promisingly, the release of Ca²⁺ makes the hydrogel to be a possible candidate scaffold for bone tissue engineering.

Self-Propelling Nanomotors Integrated with Biofilm Microenvironment-Activated NO Release to Accelerate Healing of Bacteria-Infected Diabetic Wounds

Diabetic foot ulcer (DFU) treatment is challenged by persistent bacterial infection and hyperglycemia-caused vascular dysplasia. Herein, self-propelled nanomotors are designed to achieve biofilm microenvironment (BME)-activated multistage release of NO for effective sterilization and subsequent angiogenesis promotion. CaO₂ nanoparticles (NPs) are capped with PDA layers, followed by complexation with Fe²⁺ and surface grafting of cysteine-NO to obtain Janus Ca@PDA_Fe -CNO NPs. In response to low pH in BME, the decomposition of CaO₂ cores generates O₂ from one side of Janus NPs to propel biofilm penetration, and the released H₂ O₂ and Fe²⁺ produce •OH through Fenton reaction. The concurrent glutathione-triggered release of NO can be converted into reactive nitrogen species, which exhibit significantly higher bactericidal efficacy than those with only generation of •OH or NO. The slow release of NO for an extended time period promotes endothelial cell proliferation and migration. On Staphylococcus aureus-infected skin wounds of diabetic mice, NP treatment eliminates bacterial infections and significantly elevates blood vessel densities, leading to full wound recovery and regeneration of arranged collagen fibers and skin accessories. Thus, the self-propelling and multistage release of NO provide a feasible strategy to combat biofilm infection without using any antibiotics and accelerate angiogenesis and wound healing for DFU treatment.

Jamil SNA, Li F, Mat Azmi ID, Chiang PC, Choong TSY. Synthesis of Controlled-Release Calcium Peroxide Nanoparticles Coated with Dextran for Removal of Doxycycline from Aqueous System

Nanoscale calcium peroxide (nCP) has turned out to be one of the effective and environmentally friendly approaches for wastewater remediation purposes. The rapid hydrolysis of nCPs and burst oxygen release caused by the high surface-to-volume ratio of nCPs could surpass the appropriate demand for oxygenation and pollutant degradation in the aqueous system. Thus, coated oxidants (COs) have been prepared using polymeric materials to ensure long-term efficacy and slow-release capability. Therefore, the nCPs were first prepared using dextran as a stabilizer to prevent irreversible agglomeration by the chemical precipitation method and had an average mean size of 2.33 ± 0.81 nm. The synthesized nCPs were then coated with dextran to produce dextran-coated nCPs. Their characteristics and effectiveness in doxycycline (DOX) degradation were assessed. The characterization of nCPs and dextran-coated nCPs was performed using X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), fourier transform infrared spectroscopy (FTIR), Brunauer, Emmett and Teller analysis (BET), dynamic light scattering (DLS) and thermogravimetric analysis (TGA) techniques. This work suggests that dextran-coated nCPs are beneficial in wastewater treatment practice in terms of the long-term efficacy of DOX degradation potential.

Aqueous decomposition behavior of solid peroxides: Effect of pH and buffer composition on oxygen and hydrogen peroxide formation

The ability of solid peroxides to provide sustained release of both oxygen and hydrogen peroxide makes them potentially suitable for oxygen release or antibacterial applications. Most recent reports using solid peroxides to augment oxygen levels do so by compounding solid peroxide powders in polymers to retard the aqueous decomposition. Compounds with peroxidase activity may be added to reduce hydrogen peroxide toxicity. Peroxides are rarely pure and are mixed with oxide and themselves decompose to form hydroxides in water. Therefore, even if buffering strategies are used, locally the pH at the surface of aqueously immersed peroxide particles is inevitably alkaline. Since pH affects the decomposition of peroxides and hydrogen peroxide stability, this study compared for the first-time the aqueous decomposition products of hydrogen and inorganic peroxides that are in use or have been used for medical applications of have been evaluated preclinically; calcium peroxide (CaO₂), magnesium peroxide (MgO₂), zinc peroxide (ZnO₂), sodium percarbonate (Na₂CO₃.1.5H₂O₂) and hydrogen peroxide (H₂O₂). Since plasma can be approximated to be carbonate buffered phosphate solution, we maintained pH using carbonate and phosphate buffers and compared results with citrate buffers. For a given peroxide compound, we identified not only a strong effect of pH but also of buffer composition on the extent to which oxygen and hydrogen peroxide formation occurred. The influence of buffer composition was not previously appreciated, thereby establishing in vitro parameters for better design of intentional release of specific decomposition species. STATEMENT OF SIGNIFICANCE: This paper compares for the first time the aqueous decomposition products oxygen and hydrogen peroxide of solid peroxy compounds of metal cations, (calcium, magnesium, sodium and zinc) across a pH range that could feasibly be found in the body, (pH 5,7, 9) either physiologically or pathologically. We find that in addition to pH, buffer composition is also a critically important factor, making translation from in vitro models challenging. Cytotoxicity was related to hydrogen peroxide release, alkalinity and in the case of zinc peroxide to the cation itself. In vitro and preclinical studies generally report release data from polymer-peroxide composites and rarely compare peroxides with one another. Together our data provide guidance for oxygen and ROS delivery from these inorganic materials.

Investigation on visible-light photocatalytic performance and mechanism of zinc peroxide for tetracycline degradation and Escherichia coli inactivation

In this study, zincperoxide (ZnO₂) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO₂ (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4-12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO₂ could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O₂^-) and singlet oxygen (¹O₂) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H₂O₂ under the catalysis of Zn(OH)₂ from the hydrolysis of partial ZnO₂, respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO₂ for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation andE. coli inactivation over ZnO₂.

Open-Source and Reduced-Expenditure Nanosystem with ROS Self-Amplification and Glutathione Depletion for Simultaneous Augmented Chemodynamic/Photodynamic Therapy

Reactive oxygen species (ROS)-induced cell apoptosis has emerged as an efficient strategy for cancer therapy. However, tumor hypoxia and insufficient amounts of endogenous hydrogen peroxide (H₂O₂) in the tumor microenvironment are currently the main limitations of photodynamic therapy (PDT) and chemodynamic therapy (CDT). Moreover, the glutathione (GSH) scavenging effect on ROS further hinders the efficiency of ROS-mediated therapy. Here, a CaO₂-based nanosystem (named as CF@CO@HC) with ROS self-amplification and GSH-depletion abilities was developed by a bottom-up approach. This hybrid nanoparticle consisted of a photosensitizer-doped calcium peroxide (CaO₂) core (CaO₂-FM), a hybrid organosilica framework (Cu-ONS) incorporated with Fenton reagents (Cu²⁺) and tetrasulfide groups, and a local hydrophobic cage (HC) shell. The photosensitizer was fluorescein derivative 4-FM with a thermally activated delayed fluorescence (TADF) property. The HC shell was built to protect the CaO₂ and the photosensitizer from being attacked by water. Upon being internalized into cancer cells, the nanosystem was decomposed through the reduction reactions of Cu²⁺ and the tetrasulfide bond-doped silica shell by GSH, thus releasing Cu⁺ for Cu⁺-mediated CDT. Meanwhile, the exposed CaO₂-FM can react with H₂O to liberate photosensitizer 4-FM and generate H₂O₂ and O₂ to overcome barriers in CDT and PDT. Thus, our study provided an open-source and reduced-expenditure strategy via GSH depletion and ROS self-amplification behaviors for ROS generation and significantly achieved an improved synergistic PDT/CDT for cancers.

Ultrasmall iron oxide nanoparticles cause significant toxicity by specifically inducing acute oxidative stress to multiple organs

Background

Iron oxide nanoparticles have been approved by food and drug administration for clinical application as magnetic resonance imaging (MRI) and are considered to be a biocompatible material. Large iron oxide nanoparticles are usually used as transversal (T₂) contrast agents to exhibit dark contrast in MRI. In contrast, ultrasmall iron oxide nanoparticles (USPIONs) (several nanometers) showed remarkable advantage in longitudinal (T₁)-weighted MRI due to the brighten effect. The study of the toxicity mainly focuses on particles with size of tens to hundreds of nanometers, while little is known about the toxicity of USPIONs.

Results

We fabricated Fe₃O₄ nanoparticles with diameters of 2.3, 4.2, and 9.3 nm and evaluated their toxicity in mice by intravenous injection. The results indicate that ultrasmall iron oxide nanoparticles with small size (2.3 and 4.2 nm) were highly toxic and were lethal at a dosage of 100 mg/kg. In contrast, no obvious toxicity was observed for iron oxide nanoparticles with size of 9.3 nm. The toxicity of small nanoparticles (2.3 and 4.2 nm) could be reduced when the total dose was split into 4 doses with each interval for 5 min. To study the toxicology, we synthesized different-sized SiO₂ and gold nanoparticles. No significant toxicity was observed for ultrasmall SiO₂ and gold nanoparticles in the mice. Hence, the toxicity of the ultrasmall Fe₃O₄ nanoparticles should be attributed to both the iron element and size. In the in vitro experiments, all the ultrasmall nanoparticles (< 5 nm) of Fe₃O₄, SiO₂, and gold induced the generation of the reactive oxygen species (ROS) efficiently, while no obvious ROS was observed in larger nanoparticles groups. However, the ·OH was only detected in Fe₃O₄ group instead of SiO₂ and gold groups. After intravenous injection, significantly elevated ·OH level was observed in heart, serum, and multiple organs. Among these organs, heart showed highest ·OH level due to the high distribution of ultrasmall Fe₃O₄ nanoparticles, leading to the acute cardiac failure and death.

Conclusion

Ultrasmall Fe₃O₄ nanoparticles (2.3 and 4.2 nm) showed high toxicity in vivo due to the distinctive capability in inducing the generation of ·OH in multiple organs, especially in heart. The toxicity was related to both the iron element and size. These findings provide novel insight into the toxicology of ultrasmall Fe₃O₄ nanoparticles, and also highlight the need of comprehensive evaluation for their clinic application.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00465-y.

Silver Peroxide Nanoparticles for Combined Antibacterial Sonodynamic and Photothermal Therapy

Metal peroxide nanoparticles designed to elevate the oxidative stress are considered a promising nanotherapeutics in biomedical applications, including chemotherapy, photodynamic therapy, and bacterial disinfection. However, their lack of specificity towards the therapeutic target can cause toxic side effects to healthy tissues. Here, silver peroxide nanoparticles (Ag₂ O₂ NPs) capable of controlled reactive oxygen species (ROS) release are synthesized. The release of bactericidal Ag⁺ ions and ROS is strictly regulated by external stimuli of ultrasound (US) and near-infrared (NIR) light. In vitro and in vivo investigations show that the Ag₂ O₂ NPs present enhanced antibacterial and antibiofilm capabilities with a killing efficiency >99.9999% in 10 min, significantly accelerate multi-drug resistant Staphylococcus aureus infected skin wound closure with excellent cytocompatibility and hemocompatibility. This work not only provides the first paradigm for fabricating silver peroxide nanoparticle but also introduces a highly efficient noninvasive and safe therapeutic modality for combating bacterial infectious diseases.

Rational design of flexible microneedles coupled with CaO2@PDA-loaded nanofiber films for skin wound healing on diabetic rats

Skin ulcers is one of the complications of diabetes. At present, the treatment of diabetic skin wound is still not satisfactory, and the efficiency of drug delivery is limited by the depth...

pH-Responsive Oxygen and Hydrogen Peroxide Self-Supplying Nanosystem for Photodynamic and Chemodynamic Therapy of Wound Infection

The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) has been continuously explored in the antibacterial aspect and has achieved more effective antibacterial effect than a single therapy. We design a pH-responsive O₂ and H₂O₂ self-supplying zeolitic imidazolate framework-67 (ZIF-67) nanosystem for PDT/CDT of wound infection. Under the acidic inflammatory conditions, ZIF-67 can degrade to produce Co²⁺ and release CaO₂ and graphene quantum dots (GQDs). The exposed CaO₂ reacted with water to generate H₂O₂ and O₂. The self-supplied O₂ alleviates hypoxia at the site of inflammation and enhances external light-initiated GQD-mediated PDT, while H₂O₂ was catalyzed by endogenous Co²⁺ to produce hydroxyl radicals for Co²⁺-triggered CDT. In vitro and in vivo experiments confirm that CaO₂/GQDs@ZIF-67 has a combined PDT/CDT effect. The antibacterial mechanism indicates that bacteria post-treated with CaO₂/GQDs@ZIF-67 may be sterilized by reactive oxygen species-mediated oxidative stress and the leakage of bacterial contents. The experiments also find that CaO₂/GQDs@ZIF-67 may activate the immune response and enhance the therapeutic effect by activating the cyclic GMP-AMP synthase-stimulator of interferon genes signaling pathway.

A smart O2-generating nanocarrier optimizes drug transportation comprehensively for chemotherapy improving

Drug transportation is impeded by various barriers in the hypoxic solid tumor, resulting in compromised anticancer efficacy. Herein, a solid lipid monostearin (MS)-coated CaO₂/MnO₂ nanocarrier was designed to optimize doxorubicin (DOX) transportation comprehensively for chemotherapy enhancement. The MS shell of nanoparticles could be destroyed selectively by highly-expressed lipase within cancer cells, exposing water-sensitive cores to release DOX and produce O₂. After the cancer cell death, the core-exposed nanoparticles could be further liberated and continue to react with water in the tumor extracellular matrix (ECM) and thoroughly release O₂ and DOX, which exhibited cytotoxicity to neighboring cells. Small DOX molecules could readily diffuse through ECM, in which the collagen deposition was decreased by O₂-mediated hypoxia-inducible factor-1 inhibition, leading to synergistically improved drug penetration. Concurrently, DOX-efflux-associated P-glycoprotein was also inhibited by O₂, prolonging drug retention in cancer cells. Overall, the DOX transporting processes from nanoparticles to deep tumor cells including drug release, penetration, and retention were optimized comprehensively, which significantly boosted antitumor benefits.

Catalytic core-shell nanoparticles with self-supplied calcium and H2O2 to enable combinational tumor inhibition

Nanoparticles, presenting catalytic activity to induce intracellular oxidative species, have been extensively explored for tumor treatment, but suffer daunting challenges in the limited intracellular H₂O₂ and thus suppressed therapeutic efficacy. Here in this study, a type of composite nanoparticles, consisting CaO₂ core and Co-ferrocene shell, is designed and synthesized for combinational tumor treatment. The findings indicate that CaO₂ core can be hydrolyzed to produce large amounts of H₂O₂ and calcium ions at the acidic tumor sites. Meanwhile, Co-ferrocene shell acts as an excellent Fenton catalyst, inducing considerable ROS generation following its reaction with H₂O₂. Excessive cellular oxidative stress triggers agitated calcium accumulation in addition to the calcium ions released from the particles. The combined effect of intracellular ROS and calcium overload causes significant tumor inhibition both in vitro and in vivo.

Sprayed copper peroxide nanodots for accelerating wound healing in a multidrug-resistant bacteria infected diabetic ulcer

Vascular dysfunction and bacterial infection are key factors for the non-healing of diabetic ulcers. Growth factors and antibiotics seem to effectively target both issues. However, the short half-life and high cost of growth factors and the antibiotics resistance of bacteria greatly limit their further widespread applications. Novel strategies or agents with both angiogenic and antibacterial activities are urgently desirable. Copper peroxide (CuO₂) nanodots were reported to be decomposed into Cu²⁺ and H₂O₂ under mild acid conditions (pH 5.5). Considering that both decomposed products are acknowledged antibacterial agents (Cu²⁺, H₂O₂) and angiogenesis activator (Cu²⁺), we believe that CuO₂ nanodots are suitable for diabetic ulcer treatment because the pathological environment of infected chronic wounds is mildly acidic with pH 5.5-5.6. As expected, in vitro experiments showed that CuO₂ nanodots possessed excellent bactericidal properties against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and even methicillin-resistant Staphylococcus aureus (MRSA). CuO₂ nanodots induced the high expression of hypoxia-inducible factor (HIF-1α) and vascular endothelial growth factor (VEGF) in human umbilical vein endothelial cells (HUVECs), subsequently promoting the cell migration and tube formation for angiogenesis. In particular, CuO₂ nanodots exhibited good dispersibility and sprayable behavior in water. In vivo experiments demonstrated that the spayed CuO₂ nanodots in the wound area could effectively combat MRSA, reduce inflammation, promote angiogenesis, and consequently accelerate wound healing. Moreover, the sprayed CuO₂ nanodots in the wound sites caused negligible system toxicity. This study provides proof-of-principle evidence for applying the sprayed CuO₂ nanodots for infected diabetic ulcer treatment.

Cancer stem cells and strategies for targeted drug delivery

Cancer stem cells (CSCs) are a small proportion of cancer cells with high tumorigenic activity, self-renewal ability, and multilineage differentiation potential. Standard anti-tumor therapies including conventional chemotherapy, radiation therapy, and molecularly targeted therapies are not effective against CSCs, and often lead to enrichment of CSCs that can result in tumor relapse. Therefore, it is hypothesized that targeting CSCs is key to increasing the efficacy of cancer therapies. In this review, CSC properties including CSC markers, their role in tumor growth, invasiveness, metastasis, and drug resistance, as well as CSC microenvironment are discussed. Further, CSC-targeted strategies including the use of targeted drug delivery systems are examined.

Preparation and evaluation of reduction-responsive micelles based on disulfide-linked chondroitin sulfate A-tocopherol succinate for controlled antitumour drug release

OBJECTIVES

The study was to construct reduction-responsive chondroitin sulfate A (CSA)-conjugated TOS (CST) micelles with disulfide bond linkage, which was used for controlled doxorubicin (DOX) release and improved drug efficacy in vivo.

METHODS

CST and non-responsive CSA-conjugated TOS (CAT) were synthesized, and the chemical structure was confirmed by Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, fluorescence spectrophotometer and dynamic light scattering. Antitumour drug DOX was physically encapsulated into CST and CSA by dialysis method. Cell uptake of DOX-based formulations was investigated by confocal laser scanning microscopy. In vitro cytotoxicity was studied in A549 and AGS cells. Furthermore, antitumour activity was evaluated in A549-bearing mice.

KEY FINDINGS

CST and CAT can form self-assembled micelles, and have low value of critical micelle concentration. Notably, DOX-containing CST (D-CST) micelles demonstrated reduction-triggered drug release in glutathione-containing media. Further, reduction-responsive uptake of D-CST was observed in A549 cells. In addition, D-CST induced stronger cytotoxicity (P < 0.05) than DOX-loaded CAT (D-CAT) against A549 and AGS cells. Moreover, D-CST exhibited significantly stronger antitumour activity in A549-bearing nude mice than doxorubicin hydrochloride and D-CAT.

CONCLUSIONS

The reduction-responsive CST micelles enhanced the DOX effect at tumour site and controlled drug release.

Metal peroxides for cancer treatment

In recent years, metal peroxide (MO2) such as CaO2 has received more and more attention in cancer treatment. MO2 is readily decompose to release metal ions and hydrogen peroxide in the acidic tumor microenvironment (TME), resulting metal ions overloading, decreased acidity and elevated oxidative stress in TME. All of these changes making MO2 an excellent tumor therapeutic agent. Moreover, by combining MO2 with photosensitizers, enzymes or Fenton reagents, MO2 can assist and promote various tumor therapies such as photodynamic therapy and chemodynamic therapy. In this review, the synthesis and modification methods of MO2 are introduced, and the representative studies of MO2-based tumor monotherapy and combination therapy are discussed in detail. Finally, the current challenges and prospects of MO2 in the field of tumor therapy are emphasized to promote the development of MO2-based cancer treatment.

pH-Triggered nanoreactors as oxidative stress amplifiers for combating multidrug-resistant biofilms

Developing radical oxygen species (ROS)-generating nanoreactors as new "antibiotics" is a promising strategy for the treatment of multidrug-resistant (MDR) biofilm infections. Herein, we designed and fabricated silver nanoparticle-decorated calcium peroxide (CaO2) nanoreactors (CPA) for combating MDR biofilms. CPA could locally boost ROS production as oxidative stress amplifiers in a pH-triggered and self-catalytic manner in acidic biofilms, where H2O2 was released by the hydrolysis of CaO2 and sequentially catalyzed by Ag NPs in situ to generate O2˙-, thereby efficiently disrupting mature biofilms and killing bacteria.