Regulating the bacterial oxygen microenvironment via a perfluorocarbon-conjugated bacteriochlorin for enhanced photodynamic antibacterial efficacy

Tumor microenvironment activated mussel-inspired hollow mesoporous nanotheranostic for enhanced synergistic photodynamic/chemodynamic therapy

Anti-tumor therapies reliant on reactive oxygen species (ROS) as primary therapeutic agents face challenges due to a limited oxygen substrate. Photodynamic therapy (PDT) is particularly hindered by inherent hypoxia, while chemodynamic therapy (CDT) encounters obstacles from insufficient endogenous hydrogen peroxide (H2O2) levels. In this study, we engineered biodegradable tumor microenvironment (TME)-activated hollow mesoporous MnO2-based nanotheranostic agents, designated as HAMnO2A. This construct entails loading artemisinin (ART) into the cavity and surface modification with a mussel-inspired polymer ligand, namely hyaluronic acid-linked poly(ethylene glycol)-diethylenetriamine-conjugated (3,4-dihydroxyphenyl) acetic acid, and the photosensitizer Chlorin e6 (mPEG-HA-Dien-(Dhpa/Ce6)), facilitating dual-modal imaging-guided PDT/CDT synergistic therapy. In vitro experimentation revealed that HAMnO2A exhibited ideal physiological stability and enhanced cellular uptake capability via CD44-mediated endocytosis. Additionally, it was demonstrated that accelerated endo-lysosomal escape through the pH-dependent protonation of Dien. Within the acidic and highly glutathione (GSH)-rich TME, the active component of HAMnO2A, MnO2, underwent decomposition, liberating oxygen and releasing both Mn2+ and ART. This process alleviates hypoxia within the tumor region and initiates a Fenton-like reaction through the combination of ART and Mn2+, thereby enhancing the effectiveness of PDT and CDT by generating increased singlet oxygen (1O2) and hydroxyl radicals (•OH). Moreover, the presence of Mn2+ ions enabled the activation of T1-weighted magnetic resonance imaging. In vivo findings further validated that HAMnO2A displayed meaningful tumor-targeting capabilities, prolonged circulation time in the bloodstream, and outstanding efficacy in restraining tumor growth while inducing minimal damage to normal tissues. Hence, this nanoplatform serves as an efficient all-in-one solution by facilitating the integration of multiple functions, ultimately enhancing the effectiveness of tumor theranostics.

Fabrication of photo-induced molecular superoxide radical generator for highly efficient therapy against bacterial wound infection

The pressing need for highly efficient antibacterial strategies arises from the prevalence of microbial biofilm infections and the emergence of rapidly evolving antibiotic-resistant strains of pathogenic bacteria. Photodynamic therapy represents a highly efficient and compelling antibacterial approach, offering promising prospects for effective control of the development of bacterial resistance. However, the effectiveness of many photosensitizers is limited due to the reduced generation of reactive oxygen species (ROS) in hypoxic microenvironment, which commonly occur in pathological conditions such as inflammatory and bacteria-infected wounds. Herein, we designed and prepared two phenothiazine-derived photosensitizers (NB-1 and NB-2), which can effectively generate superoxide anion radicals (O2●-) through the type I process. Both photosensitizers demonstrate significant efficacy in vitro for the eradication of broad-spectrum bacteria. Moreover, NB-2 possesses distinct advantages including strong membrane binding and strong generation of O2●-, rendering it an exceptionally efficient antibacterial agent against mature biofilms. In addition, laser activated NB-2 could be applied to treat MRSA-infected wound in vivo, which offers new opportunities for potential practical applications.

The Application of Drugs and Nano-Therapies Targeting Immune Cells in Hypoxic Inflammation

Immune cells are pivotal in the dynamic interplay between hypoxia and inflammation. During hypoxic conditions, HIF-1α, a crucial transcription factor, facilitates the adaptation of immune cells to the hypoxic micro-environment. This adaptation includes regulating immune cell metabolism, significantly impacting inflammation development. Strategies for anti-inflammatory and hypoxic relief have been proposed, aiming to disrupt the hypoxia-inflammation nexus. Research extensively focuses on anti-inflammatory agents and materials that target immune cells. These primarily mitigate hypoxic inflammation by encouraging M2-macrophage polarization, restraining neutrophil proliferation and infiltration, and maintaining Treg/TH17 balance. Additionally, oxygen-releasing nano-materials play a significant role. By alleviating hypoxia and clearing reactive oxygen species (ROS), these nano-materials indirectly influence immune cell functions. This paper delves into the response of immune cells under hypoxic conditions and the resultant effects on inflammation. It provides a comprehensive overview of various therapies targeting specific immune cells for anti-inflammatory purposes and explores nano-materials that either carry or generate oxygen to alleviate anoxic micro-environments.

Modification of traditional composite nonwovens with stable storage of light absorption transients and photodynamic antibacterial effect

Combining photodynamic antimicrobials with nonwovens is prospective. However, common photosensitizers still have drawbacks such as poor photoactivity and the inability to charge. In this study, a photodynamic and high-efficiency antimicrobial protective material was prepared by grafting bis benzophenone-structured 4,4-terephthaloyl diphthalic anhydride (TDPA) photosensitizer, and antimicrobial agent chlorogenic acid (CA) onto spunbond-meltblown-spunbond (SMS) membranes. The charging rates for ·OH and H2O2 were 6377.89 and 913.52 μg/g/h. The light absorption transients structural storage remained above 69% for 1 month. High electrical capacity remained after seven cycles indicating its rechargeability and recyclability. The SMS/TDPA/CA membrane has excellent bactericidal performance when under illumination or lightless conditions, and the bactericidal efficiency of Escherichia coli and Staphylococcus aureus reached over 99%. The construction of self-disinfection textiles based on the photodynamic strategies proposed in this paper is constructive for expanding and promoting the application of textile materials in the medical field.

Targeted Light-Induced Immunomodulatory Strategy for Implant-Associated Infections via Reversing Biofilm-Mediated Immunosuppression

The clinical treatment efficacy for implant-associated infections (IAIs), particularly those caused by Methicillin-resistant Staphylococcus aureus (MRSA), remains unsatisfactory, primarily due to the formation of biofilm barriers and the resulting immunosuppressive microenvironment, leading to the chronicity and recurrence of IAIs. To address this challenge, we propose a light-induced immune enhancement strategy, synthesizing BSA@MnO2@Ce6@Van (BMCV). The BMCV exhibits precise targeting and adhesion to the S. aureus biofilm-infected region, coupled with its capacity to catalyze oxygen generation from H2O2 in the hypoxic and acidic biofilm microenvironment (BME), promoting oxygen-dependent photodynamic therapy efficacy while ensuring continuous release of manganese ions. Notably, targeted BMCV can penetrate biofilms, producing ROS that degrade extracellular DNA, disrupting the biofilm structure and impairing its barrier function, making it vulnerable to infiltration and elimination by the immune system. Furthermore, light-induced reactive oxygen species (ROS) around the biofilm can lyse S. aureus, triggering bacterium-like immunogenic cell death (ICD), releasing abundant immune costimulatory factors, facilitating the recognition and maturation of antigen-presenting cells (APCs), and activating adaptive immunity. Additionally, manganese ions in the BME act as immunoadjuvants, further amplifying macrophage-mediated innate and adaptive immune responses and reversing the immunologically cold BME to an immunologically hot BME. We prove that our synthesized BMCV elicits a robust adaptive immune response in vivo, effectively clearing primary IAIs and inducing long-term immune memory to prevent recurrence. Our study introduces a potent light-induced immunomodulatory nanoplatform capable of reversing the biofilm-induced immunosuppressive microenvironment and disrupting biofilm-mediated protective barriers, offering a promising immunotherapeutic strategy for addressing challenging S. aureus IAIs.

Gas Therapy: Generating, Delivery, and Biomedical Applications

Oxygen (O2 ), nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2 S), and hydrogen (H2 ) with direct effects, and carbon dioxide (CO2 ) with complementary effects on the condition of various diseases are known as therapeutic gases. The targeted delivery and in situ generation of these therapeutic gases with controllable release at the site of disease has attracted attention to avoid the risk of gas poisoning and improve their performance in treating various diseases such as cancer therapy, cardiovascular therapy, bone tissue engineering, and wound healing. Stimuli-responsive gas-generating sources and delivery systems based on biomaterials that enable on-demand and controllable release are promising approaches for precise gas therapy. This work highlights current advances in the design and development of new approaches and systems to generate and deliver therapeutic gases at the site of disease with on-demand release behavior. The performance of the delivered gases in various biomedical applications is then discussed.

Photodynamic antibacterial application of TiO2/curcumin/hydroxypropyl-cyclodextrin and its konjac glucomannan composite films

Although photodynamic therapy (PDT) has great advantages for the treatment of bacterial infections, photosensitizers (PSs) often have many disadvantages that limit their application. Improving the shortcomings of PSs and developing efficient PDT antimicrobial materials remain serious challenges. In this study, a nanocomposite drug (TiO2/curcumin/hydroxypropyl-cyclodextrin, TiO2/Cur/HPCD) was constructed and combined with konjac glucomannan to form composite films (TiO2/Cur/HPCD films, KTCHD films). The stabilities of TiO2 and Cur were improved in the presence of HPCD. The particle size of TiO2/Cur/HPCD was approximately 33.9 nm, and the addition of TiO2/Cur/HPCD enhanced the mechanical properties of the films. Furthermore, TiO2/Cur/HPCD and KTCHD films exhibited good biocompatibility and PDT antibacterial effects. The antibacterial rate of TiO2/Cur/HPCD was 74.46 % against MRSA at 500 μg/mL and 99.998 % against E. coli at 400 μg/mL, while it was adsorbed on the surface of bacteria to improve the effectiveness of the treatment. In addition, studies in mice confirmed that TiO2/Cur/HPCD and KTCHD films can treat bacterial infections and promote wound healing, with a highest wound healing rate of 84.6 % in the KTCHD-10 films + Light group on day 12. Overall, TiO2/Cur/HPCD is a promising nano-antibacterial agent and KTCHD films have the potential to be employed as antibacterial and environment-friendly trauma dressings.

Type I Photosensitizer Targeting Glycans: Overcoming Biofilm Resistance by Inhibiting the Two-Component System, Quorum Sensing, and Multidrug Efflux

Stubborn biofilm infections pose serious threats to human health due to the persistence, recurrence, and dramatically magnified antibiotic resistance. Photodynamic therapy has emerged as a promising approach to combat biofilm. Nevertheless, how to inhibit the bacterial signal transduction system and the efflux pump to conquer biofilm recurrence and resistance remains a challenging and unaddressed issue. Herein, a boric acid-functionalized lipophilic cationic type I photosensitizer, ACR-DMP, is developed, which efficiently generates •OH to overcome the hypoxic microenvironment and photodynamically eradicates methicillin-resistant Staphylococcus aureus (MRSA) and biofilms. Furthermore, it not only alters membrane potential homeostasis and osmotic pressure balance due to its strong binding ability with plasma membrane but also inhibits quorum sensing and the two-component system, reduces virulence factors, and regulates the activity of the drug efflux pump attributed to the glycan-targeting ability, helping to prevent biofilm recurrence and conquer biofilm resistance. In vivo, ACR-DMP successfully obliterates MRSA biofilms attached to implanted medical catheters, alleviates inflammation, and promotes vascularization, thereby combating infections and accelerating wound healing. This work not only provides an efficient strategy to combat stubborn biofilm infections and bacterial multidrug resistance but also offers systematic guidance for the rational design of next-generation advanced antimicrobial materials.

A nanozyme-reinforced injectable photodynamic hydrogel for combating biofilm infection

Bacterial biofilm-associated infectious diseases remain serious menaces to human health. Recently, photodynamic therapy (PDT) has become a prospective strategy for combating biofilm infection. However, anaerobic conditions in a biofilm greatly inhibit its therapeutic efficacy. Here, a nanozyme-reinforced injectable hydrogel is prepared using Ca2+-crosslinked sodium alginate incorporated with photosensitizer-loaded MnO2 nanosheets and CaO2 nanoparticles for O2 self-sufficient PDT to eradicate biofilm infection. In our design, CaO2 reacts with water to produce locally concentrated H2O2, which could be catalyzed by MnO2 nanosheets (catalase-mimic nanozymes) to generate O2 and greatly relieve the hypoxic conditions in the biofilm, thus significantly strengthening PDT efficacy. In vitro assays confirmed that the hybrid hydrogel not only exhibits high-performance bactericidal activity in combating both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli but also shows great efficacy in eliminating biofilm infection. Moreover, benefiting from its good syringeability, the hybrid hydrogel is prone to fit irregular wounds and exhibits high efficiency in promoting wound healing in a biofilm-infected mice model. Besides, no obvious toxicity is detected in the hybrid hydrogel. Overall, we envision that our designed hydrogel could provide a prospective solution for combating biofilm-associated infections.

Oxygen releasing patches based on carbohydrate polymer and protein hydrogels for diabetic wound healing: A review

Diabetic wounds are among the major healthcare challenges, consuming billions of dollars of resources and resulting in high numbers of morbidity and mortality every year. Lack of sufficient oxygen supply is one of the most dominant causes of impaired healing in diabetic wounds. Numerous clinical and experimental studies have demonstrated positive outcomes as a result of delivering oxygen at the diabetic wound site, including enhanced angiogenesis, antibacterial and cell proliferation activities. However, prolonged and sustained delivery of oxygen to improve the wound healing process has remained a major challenge due to rapid release of oxygen from oxygen sources and limited penetration of oxygen into deep skin tissues. Hydrogels made from sugar-based polymers such as chitosan and hyaluronic acid, and proteins such as gelatin, collagen and hemoglobin have been widely used to deliver oxygen in a sustained delivery mode. This review presents an overview of the recent advances in oxygen releasing hydrogel based patches as a therapeutic modality to enhance diabetic wound healing. Various types of oxygen releasing wound healing patch have been discussed along with their fabrication method, release profile, cytocompatibility and in vivo results. We also briefly discuss the challenges and prospects related to the application of oxygen releasing biomaterials as wound healing therapeutics.

Research Progress in Oxygen Carrier Design and Application

Ischemia or hypoxia can lead to pathological changes in the metabolism and function of tissues and then lead to various diseases. Timely and effective blood resuscitation or improvement of hypoxia is very important for the treatment of diseases. However, there is a need to develop stable, nontoxic, and immunologically inert oxygen carriers due to limitations such as blood shortages, different blood types, and the risk of transmitting infections. With the development of various technologies, oxygen carriers based on hemoglobin and perfluorocarbon have been widely studied in recent years. This paper reviews the development and application of hemoglobin and perfluorocarbon oxygen carriers. The design of oxygen carriers was analyzed, and their application as blood substitutes or oxygen carriers in various hypoxic diseases was discussed. Finally, the characteristics and future research of ideal oxygen carriers were prospected to provide reference for follow-up research.

Recent Advances in Nanoplatform Construction Strategy for Alleviating Tumor Hypoxia

Hypoxia is a typical feature of most solid tumors and has important effects on tumor cells' proliferation, invasion, and metastasis. This is the key factor that leads to poor efficacy of different kinds of therapy including chemotherapy, radiotherapy, photodynamic therapy, etc. In recent years, the construction of hypoxia-relieving functional nanoplatforms through nanotechnology has become a new strategy to reverse the current situation of tumor microenvironment hypoxia and improve the effectiveness of tumor treatment. Here, the main strategies and recent progress in constructing nanoplatforms are focused on to directly carry oxygen, generate oxygen in situ, inhibit mitochondrial respiration, and enhance blood perfusion to alleviate tumor hypoxia. The advantages and disadvantages of these nanoplatforms are compared. Meanwhile, nanoplatforms based on organic and inorganic substances are also summarized and classified. Through the comprehensive overview, it is hoped that the summary of these nanoplatforms for alleviating hypoxia could provide new enlightenment and prospects for the construction of nanomaterials in this field.

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.

Structural optimization of BODIPY photosensitizers for enhanced photodynamic antibacterial activities

Enhancing the interactions between photosensitizers and bacteria is key to developing effective photodynamic antibacterial agents. However, the influence of different structures on the therapeutic effects has not been systematically investigated. Herein, 4 BODIPYs with distinct functional groups, including the phenylboronic acid (PBA) group and pyridine (Py) cations, were designed to explore their photodynamic antibacterial activities. The BODIPY with the PBA group (IBDPPe-PBA) exhibits potent activity against planktonic Staphylococcus aureus (S. aureus) upon illumination, while the BODIPY with Py cations (IBDPPy-Ph) or both the PBA group and Py cations (IBDPPy-PBA) can significantly minimize the growth of both S. aureus and Escherichia coli (E. coli). In particular, IBDPPy-Ph can not only eliminate the mature S. aureus biofilm and E. coli biofilm in vitro, but also promote the healing of the infected wound. Our work provides an alternative for reasonable design of photodynamic antibacterial materials.

Bacterial Toxin-Responsive Biomimetic Nanobubbles for Precision Photodynamic Therapy against Bacterial Infections

With few options available for the effective treatment of multidrug-resistant bacteria, photodynamic therapy (PDT) has emerged as a promising therapeutic strategy that does not promote the development of antibiotic resistance. Unfortunately, the beneficial bactericidal effect of PDT is oftentimes accompanied by the uncontrollable production of reactive oxygen species. To overcome this issue, a pore-forming toxin (PFT)-responsive biomimetic nanobubble is designed, which is constructed by co-encapsulating a perfluorocarbon nanoemulsion and a photosensitizer within the red blood cell membrane. It is shown that PFTs derived from three pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), group A Streptococcus (GAS), and Listeria monocytogenes (LM), can be effectively absorbed by the nanobubble. Upon toxin absorption, the formation of pores on the nanobubble surface allows the accelerated release of oxygen dissolved inside the nanoemulsion along with the photosensitizer, thus resulting in enhanced PDT and bactericidal efficacy. In three skin infection models, treatment with the nanobubbles results in significantly decreased lesion formation and reduced inflammation. In addition to oxygen, the platform can be used to deliver nitric oxide in a bacterial toxin-dependent manner. Overall, biomimetic nanobubbles may work as a broad gas delivery system that is capable of responding to a variety of PFT-based stimuli for precision PDT.

Recent Development of Polydopamine Anti-Bacterial Nanomaterials

Polydopamine (PDA), as a mussel-inspired material, exhibits numerous favorable performance characteristics, such as a simple preparation process, prominent photothermal transfer efficiency, excellent biocompatibility, outstanding drug binding ability, and strong adhesive properties, showing great potential in the biomedical field. The rapid development of this field in the past few years has engendered substantial progress in PDA antibacterial materials. This review presents recent advances in PDA-based antimicrobial materials, including the preparation methods and antibacterial mechanisms of free-standing PDA materials and PDA-based composite materials. Furthermore, the urgent challenges and future research opportunities for PDA antibacterial materials are discussed.