Infection microenvironment-activated core-shell nanoassemblies for photothermal/chemodynamic synergistic wound therapy and multimodal imaging

Ultra-Photostable Bacterial-Seeking Near-Infrared CPDs for Simultaneous NIR-II Bioimaging and Antibacterial Therapy

Bacterial infections can pose significant health risks as they have the potential to cause a range of illnesses. These infections can spread rapidly and lead to complications if not promptly diagnosed and treated. Therefore, it is of great significance to develop a probe to selectively target and image pathogenic bacteria while simultaneously killing them, as there are currently no effective clinical solutions available. This study presents a novel approach using near-infrared carbonized polymer dots (NIR-CPDs) for simultaneous in vivo imaging and treatment of bacterial infections. The core-shell structure of the NIR-CPDs facilitates their incorporation into bacterial cell membranes, leading to an increase in fluorescence brightness and photostability. Significantly, the NIR-CPDs exhibit selective bacterial-targeting properties, specifically identifying Staphylococcus aureus (S. aureus) while sparing Escherichia coli (E. coli). Moreover, under 808 nm laser irradiation, the NIR-CPDs exhibit potent photodynamic effects by generating reactive oxygen species that target and damage bacterial membranes. In vivo experiments on infected mouse models demonstrate not only precise imaging capabilities but also significant therapeutic efficacy, with marked improvements in wound healing. The study provides the dual-functional potential of NIR-CPDs as a highly effective tool for the advancement of medical diagnostics and therapeutics in the fight against bacterial infections.

Tailored Phototherapy Agent by Infection Site In Situ Activated Against Methicillin-Resistant S. aureus

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is a promising treatment approach for multidrug resistant infections. PDT/PTT combination therapy can more efficiently eliminate pathogens without drug resistance. The key to improve the efficacy of photochemotherapy is the utilization efficiency of non-radiation energy of phototherapy agents. Herein, a facile phototherapy molecule (SCy-Le) with the enhancement of non-radiative energy transfer is designed by an acid stimulation under a single laser. Introduction of the protonated receptor into SCy-Le results in a distorted intramolecular charge in the infected acidic microenvironment, pH ≈ 5.5, which in turn, enhances light capture, reduces the singlet-triplet transition energies (ΔES1-T1), promotes electron system crossing, enhances capacity of reactive oxygen species generation, and causes a significant increase in temperature by improving vibrational relaxation. SCy-Le shows more than 99% bacterial killing rate against both methicillin-resistant Staphylococcus aureus and its biofilms in vitro and causes bacteria-induced wound healing in mice. This work will provide a new perspective for the design of phototherapy agents, and the emerging photochemotherapy will be a promising approach to combat the problem of antibiotic resistance.

Exosome prospects in the diagnosis and treatment of non-alcoholic fatty liver disease

The growing prevalence of NAFLD and its global health burden have provoked considerable research on possible diagnostic and therapeutic options for NAFLD. Although various pathophysiological mechanisms and genetic factors have been identified to be associated with NAFLD, its treatment remains challenging. In recent years, exosomes have attracted widespread attention for their role in metabolic dysfunctions and their efficacy as pathological biomarkers. Exosomes have also shown tremendous potential in treating a variety of disorders. With increasing evidence supporting the significant role of exosomes in NAFLD pathogenesis, their theragnostic potential has become a point of interest in NAFLD. Expectedly, exosome-based treatment strategies have shown promise in the prevention and amelioration of NAFLD in preclinical studies. However, there are still serious challenges in preparing, standardizing, and applying exosome-based therapies as a routine clinical option that should be overcome. Due to the great potential of this novel theragnostic agent in NAFLD, further investigations on their safety, clinical efficacy, and application standardization are highly recommended.

Infection microenvironment-triggered nanoparticles eradicate MRSA by thermally amplified chemodynamic therapy and M1 macrophage

It is of great significance to develop a novel approach to treat bacterial infections, as the frequent misuse of antibiotics leads to the serious problem of bacterial resistance. This study proposed antibiotic-free antibacterial nanoparticles for eliminating methicillin-resistant Staphylococcus aureus (MRSA) based on a multi-model synergistic antibacterial ability of chemodynamic therapy (CDT), photothermal effect, and innate immunomodulation. Specifically, a polydopamine (PDA) layer coated and Ag nanoparticles loaded core-shell structure Fe3O4 nanoparticles (Fe3O4@PDA-Ag) is prepared. The Fe3O4 catalyzes H2O2 present in acidic microenvironment of bacterial infection into more toxic reactive oxygen species (ROS) and synergizes with the released Ag ions to exert a stronger bactericidal capacity, which can be augmented by photothermal action of PDA triggered by near-infrared light and loosen the biofilm by photothermal action to promote the penetration of ROS and Ag ion into the biofilm, result in disrupting biofilm structure along with killing encapsulated bacteria. Furthermore, Fe3O4@PDA-Ag exerts indirect antibacterial effects by promoting M1 macrophage polarizing. Animal models demonstrated that Fe3O4@PDA-Ag effectively controlled MRSA-induced infections through photothermal enhanced CDT, Ag+ releasing, and macrophage-mediated bactericidal properties. The acid-triggered antibacterial nanoparticles are expected to combat drug-resistant bacteria infection.

Iron/Molybdenum Sulfide Nanozyme Cocatalytic Fenton Reaction for Photothermal/Chemodynamic Efficient Wound Healing

The issue of bacterial infectious diseases remains a significant concern worldwide, particularly due to the misuse of antibiotics, which has caused the emergence of antibiotic-resistant strains. Fortunately, the rapid development of nanomaterials has propelled significant progress in antimicrobial therapy, offering promising solutions. Among them, the utilization of nanoenzyme-based chemodynamic therapy (CDT) has become a highly hopeful approach to combating bacterial infectious diseases. Nevertheless, the application of CDT appears to be facing certain constraints for its low efficiency in the Fenton reaction at the infected site. In this study, we have successfully synthesized a versatile nanozyme, which was a composite of molybdenum sulfide (MoS2) and iron sulfide (FeS2), through the hydrothermal method. The results showed that iron/molybdenum sulfide nanozymes (Fe/Mo SNZs) with desirable peroxidase (POD) mimic activity can generate cytotoxic reactive oxygen species (ROS) by successfully triggering the Fenton reaction. The presence of MoS2 significantly accelerates the conversion of Fe2+/Fe3+ through a cocatalytic reaction that involves the participation of redox pairs of Mo4+/Mo6+, thereby enhancing the efficiency of CDT. Additionally, based on the excellent photothermal performance of Fe/Mo SNZs, a near-infrared (NIR) laser was used to induce localized temperature elevation for photothermal therapy (PTT) and enhance the POD-like nanoenzymatic activity. Notably, both in vitro and in vivo results demonstrated that Fe/Mo SNZs with good broad-spectrum antibacterial properties can help eradicate Gram-negative bacteria like Escherichia coli and Gram-positive bacteria like Staphylococcus aureus. The most exciting thing is that the synergistic PTT/CDT exhibited astonishing antibacterial ability and can achieve complete elimination of bacteria, which promoted wound healing after infection. Overall, this study presents a synergistic PTT/CDT strategy to address antibiotic resistance, providing avenues and directions for enhancing the efficacy of wound healing treatments and offering promising prospects for further clinical use in the near future.

20- Deoxyingenol attenuate morphine-induced hippocampus neurotoxicity and memory impairments in rats

Objective

The present study aimed to see if 20-Deoxyingenol(20-DOI) could protect hippocampus neurons from the neurotoxic effects of morphine and reduce memory loss in rats.

Method

Male Wistar rats were given morphine hydrochloride (45 mg/kg, sc, four weeks) and 20-DOI (10, 20 mg/kg, ip., coadministered with morphine) for the Morris Water Maze (MWM) test to investigate the effects of 20-DOI on spatial learning and memory. Western blotting was used to evaluate the expression of the hippocampal CA1 region of the cleaved caspase-3, Bax, and Bcl2 proteins and so on. Moreover, these assays were used to evaluate the expression of superoxide dismutase (SOD)2, heme oxygenase 1(HO1) protein, and glutathione peroxidase (GPx) activity within the hippocampus CA1 area.

Results

The administration of 20-DOI (10 and 20 mg/kg) to morphine-treated mice enhanced spatial learning and reduced memory deficits. Additionally, 20-DOI treatment reduced apoptosis and oxidative stress in the hippocampal CA1 region of morphine-treated rats. Moreover, 20-DOI improved the autophagy level of the hippocampal CA1 area of morphine-treated rats using Transcription factor EB (TFEB), and 20-DOI prevented spatial learning and memory impairment in morphine-treated rats. The current observation could be partially due to the inhibition of neuronal apoptosis and oxidative stress in the hippocampal CA1 region of rats treated with morphine and the improved autophagy in this region.

Conclusions

20-DOI attenuated morphine administration in rats with chronic disease caused spatial learning and memory dysfunction. These mechanistic effects could be partially related to 20-DOI protecting the CA1 region of rat hippocampal neurons from the morphine-induced oxidative stress, apoptosis, and autophagy through TFEB.

Recent design strategies for boosting chemodynamic therapy of bacterial infections

The emergence of drug-resistant bacteria poses a significant threat to people's lives and health as bacterial infections continue to persist. Currently, antibiotic therapy remains the primary approach for tackling bacterial infections. However, the escalating rates of drug resistance coupled with the lag in the development of novel drugs have led to diminishing effectiveness of conventional treatments. Therefore, the development of nonantibiotic-dependent therapeutic strategies has become imperative to impede the rise of bacterial resistance. The emergence of chemodynamic therapy (CDT) has opened up a new possibility due to the CDT can convert H2O2 into •OH via Fenton/Fenton-like reaction for drug-resistant bacterial treatment. However, the efficacy of CDT is limited by a variety of practical factors. To overcome this limitation, the sterilization efficiency of CDT can be enhanced by introducing the therapeutics with inherent antimicrobial capability. In addition, researchers have explored CDT-based combined therapies to augment its antimicrobial effects and mitigate its potential toxic side effects toward normal tissues. This review examines the research progress of CDT in the antimicrobial field, explores various strategies to enhance CDT efficacy and presents the synergistic effects of CDT in combination with other modalities. And last, the current challenges faced by CDT and the future research directions are discussed.

Light, Copper, Action: Visible-Light Illumination Enhances Bactericidal Activity of Copper Particles

Bacteria are an old concern to human health, as they are responsible for nosocomial infections, and the number of antibiotic-resistant microorganisms keeps growing. Copper is known for its intrinsic biocidal properties, and therefore, it is a promising material to combat infections when added to surfaces. However, its biocidal properties in the presence of light illumination have not been fully explored, especially regarding the use of microsized particles since nanoparticles have taken over all fields of research and subjugated microparticles despite them being abundant and less expensive. Thus, the present work studied the bactericidal properties of metallic copper particles, in microscale (CuMPs) and nanoscale (CuNPs), in the absence of light and under white LED light illumination. The minimum bactericidal concentration (MBC) of CuMPs against Staphylococcus aureus that achieved a 6-log reduction was 5.0 and 2.5 mg mL-1 for assays conducted in the absence of light and under light illumination, respectively. Similar behavior was observed against Escherichia coli. The bactericidal activity under illumination provided a percentage increase in log reduction values of 65.2% for S. aureus and 166.7% for E. coli when compared to the assays under dark. This assay reproduced the testing CuNPs, which showed superior bactericidal activity since the concentration of 2.5 mg mL-1 promoted a 6-log reduction of both bacteria even under dark. Its superior bactericidal activity, which overcame the effect of illumination, was expected once the nanoscale facilitated the interaction of copper within the surface of bacteria. The results from MBC were supported by fluorescence microscopy and atomic absorption spectroscopy. Therefore, CuMPs and CuNPs proved to have size- and dose-dependent biocidal activity. However, we have shown that CuMPs photoactivity is competitive compared to that of CuNPs, allowing their application as a self-cleaning material for disinfection processes assisted by conventional light sources without additives to contain the spread of pathogens.

Photothermal and Photocatalytic Glycol Chitosan and Polydopamine-Grafted Oxygen Vacancy Bismuth Oxyiodide (BiO1-x I) Nanoparticles for the Diagnosis and Targeted Therapy of Diabetic Wounds

Treatment of diabetic wounds is a significant clinical challenge due to the massive infections caused by bacteria. In this study, multifunctional glycol chitosan and polydopamine-coated BiO1-x I (GPBO) nanoparticles (NPs) with near-infrared (NIR) photothermal and photocatalytic abilities are prepared. When infection occurs, the local microenvironment becomes acidic, and the pH-switchable GPBO can target the bacteria of the wound site. The NIR-assisted GPBO treatment exhibits anti-bacterial effects with fast response, high efficiency, and long duration to Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. GPBO achieves excellent photothermal imaging and CT imaging of the mouse subcutaneous abscess model. With the assistance of NIR irradiation, the GPBO promotes the healing of the diabetic wound model with the effects of anti-bacteria, anti-inflammation, the M2 polarization promotion of macrophages, and angiogenesis. This is the first-time report of nano-sized BiO1-x I. The synthesis and selected application for the imaging and targeted therapy of diabetic wounds are presented. This study offers an example of the NP-assisted precise diagnosis and therapy of bacterial infection diseases.

Nanozyme-Engineered Hydrogels for Anti-Inflammation and Skin Regeneration

Inflammatory skin disorders can cause chronic scarring and functional impairments, posing a significant burden on patients and the healthcare system. Conventional therapies, such as corticosteroids and nonsteroidal anti-inflammatory drugs, are limited in efficacy and associated with adverse effects. Recently, nanozyme (NZ)-based hydrogels have shown great promise in addressing these challenges. NZ-based hydrogels possess unique therapeutic abilities by combining the therapeutic benefits of redox nanomaterials with enzymatic activity and the water-retaining capacity of hydrogels. The multifaceted therapeutic effects of these hydrogels include scavenging reactive oxygen species and other inflammatory mediators modulating immune responses toward a pro-regenerative environment and enhancing regenerative potential by triggering cell migration and differentiation. This review highlights the current state of the art in NZ-engineered hydrogels (NZ@hydrogels) for anti-inflammatory and skin regeneration applications. It also discusses the underlying chemo-mechano-biological mechanisms behind their effectiveness. Additionally, the challenges and future directions in this ground, particularly their clinical translation, are addressed. The insights provided in this review can aid in the design and engineering of novel NZ-based hydrogels, offering new possibilities for targeted and personalized skin-care therapies.

Copper-Single-Atom Coordinated Nanotherapeutics for Enhanced Sonothermal-Parallel Catalytic Synergistic Cancer Therapy

Phototherapy and sonotherapy are recognized by scientific medicine as effective strategies for treating certain cancers. However, these strategies have limitations such as an inability to penetrate deeper tissues and overcome the antioxidant tumor microenvironment. In this study, a novel "BH" interfacial-confined coordination strategy to synthesize hyaluronic acid-functionalized single copper atoms dispersed over boron imidazolate framework-derived nanocubes (HA-NC_Cu) to achieve sonothermal-catalytic synergistic therapy is reported. Notably, HA-NC_Cu demonstrates exceptional sonothermal conversion performance under low-intensity ultrasound irradiation, attained through intermolecular lattice vibrations. In addition, it shows promise as an efficient biocatalyst, able to generate high-toxicity hydroxyl radicals in response to tumor-endogenous hydrogen peroxide and glutathione. Density functional theory calculations reveal that the superior parallel catalytic performance of HA-NC_Cu originates from the CuN4 C/B active sites. Both in vitro and in vivo evaluations consistently demonstrate that the sonothermal-catalytic synergistic strategy significantly improves tumor inhibition rate (86.9%) and long-term survival rate (100%). In combination with low-intensity ultrasound irradiation, HA-NC_Cu triggers a dual death pathway of apoptosis and ferroptosis in MDA-MB-231 breast cancer cells, comprehensively limiting primary triple-negative breast cancer. This study highlights the applications of single-atom-coordinated nanotherapeutics in sonothermal-catalytic synergistic therapy, which may create new opportunities in biomedical research.

Photothermal theranostics with glutathione depletion and enhanced reactive oxygen species generation for efficient antibacterial treatment

Drug-resistant bacteria caused by the abuse of antibiotics have brought great challenges to antimicrobial therapy. Herein an antibiotic-free polydopamine (PDA) modified metal-organic framework (PDA-FDM-23) with photothermal-enhanced chemodynamic effect was developed for synergistic antibacterial treatment. The PDA-FDM-23 antibacterial agent exhibited high peroxidase-like activity. Moreover, the process was significantly accelerated by consuming glutathione (GSH) to generate more efficient oxidizing Cu⁺. In addition, the photothermal therapy (PTT) derived from PDA improved the chemodynamic therapy (CDT) activity triggering a reactive oxygen species explosion. This PTT-enhanced CDT strategy illustrated 100% antibacterial efficiency against both Staphylococcus aureus and Escherichia coli. Cytotoxicity and hemolysis analyses fully demonstrated the excellent biocompatibility of PDA-FDM-23. Overall, our work highlighted the strong peroxidase catalytic activity, excellent GSH consumption and photothermal performance of PDA-FDM-23, providing a new strategy for antibiotic-free reactive oxygen species (ROS) synergistic sterilization.

Antibacterial Chemodynamic Therapy: Materials and Strategies

The wide and frequent use of antibiotics in the treatment of bacterial infection can cause the occurrence of multidrug-resistant bacteria, which becomes a serious health threat. Therefore, it is necessary to develop antibiotic-independent treatment modalities. Chemodynamic therapy (CDT) is defined as the approach employing Fenton and/or Fenton-like reactions for generating hydroxyl radical (•OH) that can kill target cells. Recently, CDT has been successfully employed for antibacterial applications. Apart from the common Fe-mediated CDT strategy, antibacterial CDT strategies mediated by other metal elements such as copper, manganese, cobalt, molybdenum, platinum, tungsten, nickel, silver, ruthenium, and zinc have also been proposed. Furthermore, different types of materials like nanomaterials and hydrogels can be adopted for constructing CDT-involved antibacterial platforms. Besides, CDT can introduce some toxic metal elements and then achieve synergistic antibacterial effects together with reactive oxygen species. Finally, CDT can be combined with other therapies such as starvation therapy, phototherapy, and sonodynamic therapy for achieving improved antibacterial performance. This review first summarizes the advancements in antibacterial CDT and then discusses the present limitations and future research directions in this field, hoping to promote the development of more effective materials and strategies for achieving potentiated CDT.

Doxorubicin-Fe(III)-Gossypol Infinite Coordination Polymer@PDA:CuO2 Composite Nanoparticles for Cost-Effective Programmed Photothermal-Chemodynamic-Coordinated Dual Drug Chemotherapy Trimodal Synergistic Tumor Therapy

To achieve the maximum therapeutic effects and minimize adverse effects of trimodal synergistic tumor therapies, a cost-effective programmed photothermal (PTT)-chemodynamic (CDT)-coordinated dual drug chemotherapy (CT) trimodal synergistic therapy strategy in chronological order is proposed. According to the status or volumes of the tumors, the intensity and time of each therapeutic modality are optimized, and three modalities are combined programmatically and work in chronological order. The optimal synergistic therapy begins with high-intensity PTT for 10 min to ablate larger tumors, followed by medium-intensity CDT for several hours to eliminate medium-sized tumors, and then low-intensity coordinated dual drugs CT lasts over 48 h to clear smaller residual tumors. Composite nanoparticles, made of Fe-coordinated polydopamine mixed with copper peroxide as the cores and their surface dotted with lots of doxorubicin-Fe(III)-gossypol infinite coordination polymers (ICPs), have been developed to implement the strategy. These composite nanoparticles show excellent synergistic effects with the minimum dose of therapeutic agents and result in nearly 100% tumor inhibition for mice bearing PC-3 tumors and no observed recurrence within 60 days of treatment. The ratios of the different therapeutic agents in the composite nanoparticles can be adjusted to accommodate different types of tumors with this cost-effective programmed trimodal therapy strategy.

Near-Infrared Light-Responsive Multifunctional Photothermal/Photodynamic Titanium Diboride Nanocomposites for the Treatment of Antibiotic-Resistant Bacterial Infections

Diseases caused by bacterial infection have resulted in serious harm to human health. It is crucial to develop a multifunctional antibiotic-independent antibacterial platform for combating drug-resistant bacteria. Herein, titanium diboride (TiB₂) nanosheets integrated with quaternized chitosan (QCS) and indocyanine green (ICG) were successfully prepared as a synergetic photothermal/photodynamic antibacterial nanoplatform (TiB₂-QCS-ICG). The TiB₂-QCS-ICG nanocomposites exhibit effective photothermal conversion efficiency (24.92%) and excellent singlet oxygen (¹O₂) production capacity simultaneously under 808 nm near-infrared irradiation. QCS improved TiB₂ stability and dispersion, while also enhancing adhesion to bacteria and further accelerating the destruction of bacteria by heat and ¹O₂. In vitro experiments indicated that TiB₂-QCS-ICG had excellent antibacterial properties with an inhibition rate of 99.99% against Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA), respectively. More importantly, in vivo studies revealed that the nanoplatform can effectively inhibit bacterial infection and accelerate wound healing. The effective wound healing rate in the TiB₂-QCS-ICG treatment group was 99.6% which was much higher than control groups. Taken together, the as-developed TiB₂-QCS-ICG nanocomposite provides more possibilities to develop metal borides for antibacterial infection applications.

Nanosonosensitizers-engineered injectable thermogel for augmented chemo-sonodynamic therapy of melanoma and infected wound healing

Easy recurrence and bacteria infected-wound healing after surgery excision pose severe challenges to clinical melanoma therapy. Herein, an injectable CuO2 nanodots-engineered thermosensitive chitosan hydrogel (CuO2-BSO@Gel) for enhanced melanoma chemo-sonodynamic therapy and improved infected wound healing was rationally constructed by facilely integrating the CuO2 nanodots and L-Buthionine-(S, R)-sulfoximine (BSO) with thermoresponsive hydrogel. Favored by the Fenton catalytic activity of Cu2+, the CuO2 nanodots can achieve enhanced chemodynamic therapy (CDT) by self-supplying H2O2 under acidic tumor microenvironment. Simultaneously, the CuO2 nanodots with a narrow bandgap (2.29 ​eV) were proven to be the efficient sonosensitizers, and the corresponding quantum yield of singlet oxygen (1O2) could be boosted by the O2 generation during Fenton-like reactions. Additionally, combining with the glutathione (GSH) depletion of loaded BSO, intracellular oxidative stress induced by SDT and CDT was further amplified, leading to the specific ferroptosis. Importantly, this multifunctional hydrogel significantly promoted the proliferation of normal skin cells and accelerated the bacteria-infected wound healing by the effective chemo-sonodynamic antibacterial activity and the enhanced angiogenesis. Thus, the engineered thermogel features the distinct chemo-sonodynamic performance, desirable biocompatibility and bioactivity, providing a competitive strategy for eradicating melanoma and infected wound healing.

In Situ Fabrication of Silver Peroxide Hybrid Ultrathin Co-Based Metal-Organic Frameworks for Enhanced Chemodynamic Antibacterial Therapy

Bacterial-induced infectious diseases have always caused an unavoidable problem and lead to an increasing threat to human health. Hence, there is an urgent need for effective antibacterial strategies to treat infectious diseases. Current methods are often ineffective and require large amounts of hydrogen peroxide (H₂O₂), with harmful effects on normal healthy tissue. Chemodynamic therapy (CDT) provides an ideal infection microenvironment (IME)-activated paradigm to tackle bacterial-related diseases. To take full advantage of the specificity of IME and enhanced CDT for wounds with bacterial infection, we have designed an intelligent antibacterial system that exploits nanocatalytic ZIF-67@Ag₂O₂ nanosheets. In this system, silver peroxide nanoparticles (Ag₂O₂ NPs) were grown on ultrathin zeolitic imidazolate framework-67 (ZIF-67) nanosheets by in situ oxidation, and then, ZIF-67@Ag₂O₂ nanosheets with the ability to self-generate H₂O₂ were triggered by the mildly acidic environment of IME. Lamellar ZIF-67 nanosheets were shown to rapidly degrade and release Co²⁺, allowing the conversion of less reactive H₂O₂ into the highly toxic reactive oxygen species hydroxyl radicals (^•OH) for enhanced CDT antibacterial properties. In vivo results revealed that the ZIF-67@Ag₂O₂ nanosheet system exhibits excellent antibacterial performance against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The proposed hybrid strategy demonstrates a promising therapeutic strategy to enable antibacterial agents with IME-responsive nanocatalytic activity to circumvent antibiotic resistance against bacterial infections.

Designing Single-Atom Active Sites on sp2 -Carbon Linked Covalent Organic Frameworks to Induce Bacterial Ferroptosis-Like for Robust Anti-Infection Therapy

With the threat posed by drug-resistant pathogenic bacteria, developing non-antibiotic strategies for eradicating clinically prevalent superbugs remains challenging. Ferroptosis is a newly discovered form of regulated cell death that can overcome drug resistance. Emerging evidence shows the potential of triggering ferroptosis-like for antibacterial therapy, but the direct delivery of iron species is inefficient and may cause detrimental effects. Herein, an effective strategy to induce bacterial nonferrous ferroptosis-like by coordinating single-atom metal sites (e.g., Ir and Ru) into the sp² -carbon-linked covalent organic framework (sp² c-COF-Ir-ppy₂ and sp² c-COF-Ru-bpy₂ ) is reported. Upon activating by light irradiation or hydrogen peroxide, the as-constructed Ir and Ru single-atom catalysts (SACs) can significantly expedite intracellular reactive oxygen species burst, enhance glutathione depletion-related glutathione peroxidase 4 deactivation, and disturb the nitrogen and respiratory metabolisms, leading to lipid peroxidation-driven ferroptotic damage. Both SAC inducers show potent antibacterial activity against Gram-positive bacteria, Gram-negative bacteria, clinically isolated methicillin-resistant Staphylococcus aureus (MRSA), and biofilms, as well as excellent biocompatibility and strong therapeutic and preventive potential in MRSA-infected wounds and abscesses. This delicate nonferrous ferroptosis-like strategy may open up new insights into the therapy of drug-resistant pathogen infection.

Redox ferrocenylseleno compounds modulate longitudinal and transverse relaxation times of FNPs-Gd MRI contrast agents for multimodal imaging and photo-Fenton therapy

Developing a feasible way to feature longitudinal (T₁) and transverse (T₂) relaxation performance of contrast agents for magnetic resonance imaging (MRI) is important in cancer diagnosis and therapy. Improved accessibility to water molecule is essential for accelerating the relaxation rate of water protons around the contrast agents. Ferrocenyl compounds have reversible redox property for modulating the hydrophobicity/hydrophilicity of assemblies. Thus, they could be the candidates that can change water accessibility to the contrast agent surface. Herein, we incorporated ferrocenylseleno compound (FcSe) with Gd³⁺-based paramagnetic UCNPs, to obtain FNPs-Gd nanocomposites using T₁-T₂ MR/UCL trimodal imaging and simultaneous photo-Fenton therapy. When the surface of NaGdF₄:Yb,Tm UNCPs was ligated by FcSe, the hydrogen bonding between hydrophilic selenium and surrounding water molecules accelerated their proton exchange to initially endow FNPs-Gd with high r₁ relaxivity. Then, hydrogen nuclei from FcSe disrupted the homogeneity of the magnetic field around the water molecules. This facilitated T₂ relaxation and resulted in enhanced r₂ relaxivity. Notably, upon the near-infrared light-promoted Fenton-like reaction in the tumor microenvironment, hydrophobic ferrocene(II) of FcSe was oxidized into hydrophilic ferrocenium(III), which further increased the relaxation rate of water protons to obtain r₁ = 1.90±0.12 mM^-1 s^-1 and r₂ = 12.80±0.60 mM^-1 s^-1. With an ideal relaxivity ratio (r₂/r₁) of 6.74, FNPs-Gd exhibited high contrast potential of T₁-T₂ dual-mode MRI in vitro and in vivo. This work confirms that ferrocene and selenium are effective boosters that enhance the T₁-T₂ relaxivities of MRI contrast agents, which could provide a new strategy for multimodal imaging-guided photo-Fenton therapy of tumors. STATEMENT OF SIGNIFICANCE: T₁-T₂ dual-mode MRI nanoplatform with tumor-microenvironment-responsive features has been an attractive prospect. Herein, we designed redox ferrocenylseleno compound (FcSe) modified paramagnetic Gd³⁺-based UCNPs, to modulate T₁-T₂ relaxation time for multimodal imaging and H₂O₂-responsive photo-Fenton therapy. Selenium-hydrogen bond of FcSe with surrounding water molecules facilitated water accessibility for fast T₁ relaxation. Hydrogen nucleus in FcSe perturbed the phase coherence of water molecules in an inhomogeneous magnetic field and thus accelerated T₂ relaxation. In tumor microenvironment, FcSe was oxidized into hydrophilic ferrocenium via NIR light-promoted Fenton-like reaction which further increased both T₁ and T₂ relaxation rates; Meanwhile, the released toxic •OH performed on-demand cancer therapy. This work confirms that FcSe is an effective redox mediate for multimodal imaging-guided cancer therapy.

Nanomaterials as multimodal photothermal agents (PTAs) against 'Superbugs'

Superbugs, also known as multidrug-resistant bacteria, have become a lethal and persistent threat due to their unresponsiveness toward conventional antibiotics. The main reason for this is that superbugs can rapidly mutate and restrict any foreign drug/molecule in their vicinity. Herein, nanomaterial-mediated therapies have set their path and shown burgeoning efficiency toward the ablation of superbugs. Notably, treatment modalities like photothermal therapy (PTT) have shown prominence in killing multidrug-resistant bacteria with their ability to generate local heat shock-mediated hyperthermia in such species. However, photothermal treatment has some serious limitations, such as high cost, complexity, and even toxicity to some extent. Hence, it is important to resolve such shortcomings of PTTs as they provide substantial tissue penetration. This is why multimodal PTTs have emerged and taken over this domain of research for the past few years. In this work, we have summarized and critically reviewed such exceptional works of recent times and provided a perspective to enhance their efficiencies. Profoundly, we discuss the design rationales of some novel photothermal agents (PTAs) and shed light on their mechanisms. Finally, challenges for PTT-derived multimodal therapy are presented, and capable synergistic bactericidal prospects are anticipated.

Electrogenerated copper selenide with positive charge to efficiently capture and combat drug-resistant bacteria for wound healing

Limited by the effective radius of metal ion release, higher concentrations of antibacterial agents are usually required to achieve satisfactory efficacy. Unfortunately, the potential cytotoxicity of metal ions limits the administered dose, which greatly hinders the widespread use of metal antibacterial agents. In this work, we used a convenient electrochemical method to prepare electropositive copper selenide (CuSe) nanosheets gathered from the cathode. Under physiological conditions, trace amounts of electrolytic CuSe (E-CuSe, 1 μg mL^-1) could electrostatically bind to bacterial membranes and almost completely kill three resistant bacteria models (10⁶ colony forming unit (CFU) mL^-1). The extremely low effective dose of E-CuSe reaches a new benchmark in comparison with copper-based nanomaterials in other related studies. In addition, due to the reasonable coupling of selenium and copper, the as-prepared E-CuSe nanosheets exhibit lower cytotoxicity compared to copper oxide. As expected, the E-CuSe performed well in resistant bacteria-infected wound healing in rats, rapidly promoting wound tissue with a diameter of about 1 cm recovery within 7 days. Transcriptome analysis revealed the E-CuSe mainly acted on the membrane transport and DNA synthesis systems of bacterial cells. This work presents an efficient and in-depth paradigm for the scientific design and inactivation mechanism of metal antibacterial agents.

Modulating the local coordination environment of cobalt single-atomic nanozymes for enhanced catalytic therapy against bacteria

Single-atomic nanozymes (SANZs) characterized by atomically dispersed single metal atoms have recently contributed to breakthroughs in biomedicine due to their satisfactory catalytic activity and superior selectivity compared to their nanoscale counterparts. The catalytic performance of SANZs can be improved by modulating their coordination structure. Therefore, adjusting the coordination number of the metal atoms in the active center is a potential method for enhancing the catalytic therapy effect. In this study, we synthesized various atomically dispersed Co nanozymes with different nitrogen coordination numbers for peroxidase (POD)-mimicking single-atomic catalytic antibacterial therapy. Among the single-atomic Co nanozymes with nitrogen coordination numbers of 3 (SACNZs-N₃-C) and 4 (SACNZs-N₄-C), single-atomic Co nanozymes with a coordination number of 2 (SACNZs-N₂-C) had the highest POD-like catalytic activity. Kinetic assays and Density functional theory (DFT) calculations indicated that reducing the coordination number can lower the reaction energy barrier of single-atomic Co nanozymes (SACNZs-N_x-C), thereby increasing their catalytic performance. In vitro and in vivo antibacterial assays demonstrated that SACNZs-N₂-C had the best antibacterial effect. This study provides proof of concept for enhancing single-atomic catalytic therapy by regulating the coordination number for various biomedical applications, such as tumor therapy and wound disinfection. STATEMENT OF SIGNIFICANCE: The use of nanozymes that contain single-atomic catalytic sites has been shown to effectively promote the healing of bacteria-infected wounds by exhibiting peroxidase-like activity. The homogeneous coordination environment of the catalytic site has been associated with high antimicrobial activity, which provides insight into designing new active structures and understanding their mechanisms of action. In this study, we designed a series of cobalt single-atomic nanozymes (PSACNZs-N_x-C) with different coordination environments by shearing the Co-N bond and modifying polyvinylpyrrolidone (PVP). The synthesized PSACNZs-N_x-C demonstrated enhanced antibacterial activity against both Gram-positive and Gram-negative bacterial strains, and showed good biocompatibility in both in vivo and in vitro experiments.

All-in-one CoFe2O4@Tf nanoagent with GSH depletion and tumor-targeted ability for mutually enhanced chemodynamic/photothermal synergistic therapy

In the complex and severe tumor microenvironment, the antitumor efficiency of nanomedicines is significantly limited by their low-efficacy monotherapy, non-tumor targeting, and systemic toxicity. Herein, to achieve tumor-targeted and enhanced chemodynamic/photothermal therapy (CDT/PTT), we fabricated an "all-in-one" biocompatible transferrin-loaded cobalt ferrate nanoparticle (CoFe₂O₄@Tf (CFOT)) with multiple functions by a simple solvothermal method and the following transferrin (Tf) functionalization. Upon exposure to 808 nm laser irradiation, CFOT, as a novel photothermal agent, exhibited outstanding phototherapeutic activity because of its excellent photothermal conversion efficiency (η = 46.5%) for high-performance PTT. Moreover, CFOT with multiple redox pairs could efficiently convert endogenous H₂O₂ to hazardous hydroxyl radicals (˙OH) via Fenton reactions while scavenging overexpressed GSH in the tumor microenvironment to realize self-reinforcing CDT. Importantly, CFOT undergoes a promoted Fenton-type reaction upon increasing the temperature under a photothermal effect and could augment PTT by high-level ˙OH, exhibiting a considerably enhanced synergistic therapeutic effect. In vitro and in vivo experimental results demonstrated that CFOT has good potential as an "all-in-one" nanoagent to combine photothermal, chemodynamic, and tumor targeting for efficient tumor elimination.

Dual-Responsive Nanocomposites for Synergistic Antibacterial Therapies Facilitating Bacteria-Infected Wound Healing

The rising dangers of bacterial infections have created an urgent need for the development of a new generation of antibacterial technologies and therapeutics. Antibacterial photodynamic therapy (PDT), considered as a noninvasive treatment with no drug resistance, has become a new promising photochemistry-involved treatment strategy. Titanium oxide (TiO₂ ) is proved to be a very efficient PDT agent among the photosensitive materials, while the property of a large bandgap of TiO₂ makes it only be excited by ultraviolet light, which is harmful to organisms. In this work, a novel ligand-to-metal charge transfer (LMCT) mediated TiO₂ PDT strategy is proposed via the harmless near-infrared light irradiation. By choosing a mussel-inspired material, polydopamine (PDA) is involved in forming mesoporous TiO₂ @PDA nanoparticles (mTiO₂ @PDA NPs). The catechol groups of PDA can attach the TiO₂ tightly even in colloidal environments, and can also form the LMCT bridge, exciting TiO₂ to exert PDT function via 808 nm irradiation. Combining the sonodynamic therapy (SDT) of TiO₂ and the photothermal therapy properties of PDA, this simple structure mTiO₂ @PDA enables synergistic antibacterial applications with multiple functions under the dual excitation of NIR and ultrasound. This reliable all-in-one NPs can achieve great antibacterial effect and a rapid repair of infected wounds.

Advances in image-guided drug delivery for antibacterial therapy

The emergence of antibiotic-resistant bacterial strains is seriously endangering the global healthcare system. There is an urgent need for combining imaging with therapies to realize the real-time monitoring of pathological condition and treatment progress. It also provides guidance on exploring new medicines and enhance treatment strategies to overcome the antibiotic resistance of existing conventional antibiotics. In this review, we provide a thorough overview of the most advanced image-guided approaches for bacterial diagnosis (e.g., computed tomography imaging, magnetic resonance imaging, photoacoustic imaging, ultrasound imaging, fluorescence imaging, positron emission tomography, single photon emission computed tomography imaging, and multiple imaging), and therapies (e.g., photothermal therapy, photodynamic therapy, chemodynamic therapy, sonodynamic therapy, immunotherapy, and multiple therapies). This review focuses on how to design and fabricate photo-responsive materials for improved image-guided bacterial theranostics applications. We present a potential application of different image-guided modalities for both bacterial diagnosis and therapies with representative examples. Finally, we highlighted the current challenges and future perspectives image-guided approaches for future clinical translation of nano-theranostics in bacterial infections therapies. We envision that this review will provide for future development in image-guided systems for bacterial theranostics applications.

Germanene-modified chitosan hydrogel for treating bacterial wound infection: An ingenious hydrogel-assisted photothermal therapy strategy

The elaborate design of an ingenious hydrogel-assisted photothermal therapy (PTT) platform is a promising strategy for treating bacterial wound infections. Herein, a new generation of germanene nanocrystals (Ge NCs) with excellent photothermal performance are prepared via an ice-bath sonication liquid-phase exfoliation technique. Whereafter, by crosslinking interaction between chitosan and zinc acetate, as well as self-assembly property between Ge NCs and chitosan, we successfully construct an innovative germanene-modified chitosan antimicrobial hydrogel (CS/Ge NCs^0.8) integrating capture and killing bacteria performances. When co-cultured with bacteria, CS/Ge NCs^0.8 hydrogel with the positive charge can adsorb and restrict bacteria in the range of PTT destruction. Once the near-infrared laser is introduced, CS/Ge NCs^0.8 hydrogel will effectively convert light energy into localized heat, further inducing bacterial death. By this entirely novel modality, CS/Ge NCs^0.8 hydrogel exhibits marvelous antibacterial property against E. coli and S. aureus in vitro. Furthermore, in vivo studies demonstrate that CS/Ge NCs^0.8 hydrogel possesses the ability to significantly rescue S. aureus-induced skin wound infections, suggesting CS/Ge NCs^0.8 hydrogel can be served as an antibacterial dressing. Strikingly, this is the first-ever report of CS/Ge NCs^0.8 hydrogel in the antibacterial field, which may spur a wave of developing Ge-based biomaterials to benefit biomedical applications.

Biodegradable Fe(ii)/Fe(iii)-coordination-driven nanoassemblies for chemo/photothermal/chemodynamic synergistic therapy of bacterial infection

This study provides a novel approach for preparing biodegradable nanoassemblies with synergistic chemo/photothermal/chemodynamic performance to selectively combat bacterial infection.