Potentiating hypoxic microenvironment for antibiotic activation by photodynamic therapy to combat bacterial biofilm infections

Borosilicate bioactive glass synergizing low-dose antibiotic loaded implants to combat bacteria through ATP disruption and oxidative stress to sequentially achieve osseointegration

Bone infection is a catastrophe in clinical orthopedics. Despite being the standard therapy for osteomyelitis, antibiotic-loaded polymethyl methacrylate (PMMA) cement has low efficiency against bacteria in biofilms. Furthermore, high-dose antibiotic-loaded implants carry risks of bacterial resistance, tissue toxicity, and impairment of local tissue healing. By incorporating borosilicate bioactive glass (BSG) into low-dose gentamicin sulfate (GS)-loaded PMMA cement, an intelligent strategy that synergistically eradicates bacteria and sequentially promotes osseointegration, was devised. Results showed that BSG did not compromises the handling properties of the cement, but actually endowed it with an ionic and alkaline microenvironment, thereby damaging the integrity of bacterial cell walls and membranes, inhibiting ATP synthesis by disrupting the respiratory chain in cell membranes and glycogen metabolism, and elevating reactive oxygen species (ROS) levels by weakening antioxidant components (peroxisomes and carotenoids). These antibacterial characteristics of BSG synergistically reinforced the effectiveness of GS, which was far below the actual clinical dosage, achieving efficient bacterial killing and biofilm clearance by binding to the 30S subunit of ribosomes. Furthermore, the released GS and the ionic and alkaline microenvironment from the implants fostered the osteogenic activity of hBMSCs in vitro and coordinately enhanced osseointegration in vivo. Collectively, this study underscores that BSG incorporation offers a promising strategy for reducing antibiotic dosage while simultaneously enhancing the antibacterial activity and osteogenesis of implants. This approach holds potential for resolving the conflict between bacterial resistance and bone infection.

Metal-phenolic network crosslinked nanogel with prolonged biofilm retention for dihydroartemisinin/NIR synergistically enhanced chemodynamic therapy

Chemodynamic therapy (CDT) is emerging as a promising treatment for biofilm infections. However, its effectiveness is significantly hindered by several factors: the body's stable temperature, a limited supply of Fe2+ ions, and inadequate endogenous levels of H2O2 at the infection sites. Herin, our study introduces MPN-crosslinked hyaluronic acid (HA) nanogels as an effective strategy for treating biofilm-associated infections. The DHA@HA-TA/Fe (DHTF) nanogel is synthesized through the coordination reaction between Fe2+ ions and tannic acid (TA)-modified HA, with dihydroartemisinin (DHA) encapsulated within the structure. DHTF exhibits pH-/hyaluronidase-responsiveness in the biofilm infection microenvironment, enabling sustained release of DHA as a substitute for H2O2 and Fe2+ for CDT. The incorporation of Fe2+/TA-based MPN and DHA within the nanogels enables photothermal/DHA dually-enhanced CDT, facilitating efficient disruption of biofilm matrices and bacterial eradication through boosting reactive oxygen species production. In vivo studies demonstrate that DHTF exhibit prolonged retention within biofilms. This ensures a sustained release of therapeutic agents and continuous anti-biofilm activity. Eventually, both in vitro and in vivo evaluations consistently confirm the significant anti-biofilm capacity of DHTF. Our findings highlight the potential of DHTF as a promising nanomedicine for biofilm-related infections, offering efficient treatment strategies that could improve clinical management of these challenging conditions.

Stimuli-responsive and targeted nanomaterials: Revolutionizing the treatment of bacterial infections

Bacterial infections have emerged as a major threat to global public health. The effectiveness of traditional antibiotic treatments is waning due to the increasing prevalence of antimicrobial resistance, leading to an urgent demand for alternative antibacterial technologies. In this context, antibacterial nanomaterials have proven to be powerful tools for treating antibiotic-resistant and recurring infections. Targeting nanomaterials not only enable the precise delivery of bactericidal agents but also ensure controlled release at the infection site, thereby reducing potential systemic side effects. This review collates and categorizes nanomaterial-based responsive and precision-targeted antibacterial strategies into three key types: exogenous stimuli-responsive (including light, ultrasound, magnetism), bacterial microenvironment-responsive (such as pH, enzymes, hypoxia), and targeted antibacterial action (involving electrostatic interaction, covalent bonding, receptor-ligand mechanisms). Furthermore, we discuss recent advances, potential mechanisms, and future prospects in responsive and targeted antimicrobial nanomaterials, aiming to provide a comprehensive overview of the field's development and inspire the formulation of novel, precision-targeted antimicrobial strategies.

Janus PEGylated CuS-engineered Lactobacillus casei combats biofilm infections via metabolic interference and innate immunomodulation

Bacterial implant-associated infections predominantly contribute to the failure of prosthesis implantation. The local biofilm microenvironment (BME), characterized by its hyperacidic condition and high hydrogen peroxide (H2O2) level, inhibits the host's immune response, thereby facilitating recurrent infections. Here, a Janus PEGylated CuS nanoparticle (CuPen) armed engineered Lactobacillus casei (L. casei) denoted as LC@CuPen, is proposed to interfere with bacterial metabolism and arouse macrophage antibiofilm function. Once LC@CuPen reached the BME, NIR irradiation-activated mild heat damages L. casei and biofilm structure. Meanwhile, the BME-responsive LC@CuPen can catalyze local H2O2 to produce toxic •OH, whereas in normal tissues, the effect of •OH production is greatly reduced due to the higher pH and lower H2O2 concentration. The released bacteriocin from damaged L. casei can destroy the bacterial membrane to enhance the penetration of •OH into damaged biofilm. Excessive •OH interferes with normal bacterial metabolism, resulting in reduced resistance of bacteria to heat stress. Finally, under the action of mild heat treatment, the bacterial biofilm lysed and died. Furthermore, the pathogen-associated molecular patterns (PAMPs) in LC@CuPen can induce M1 polarization of macrophages through NF-κB pathway and promote the release of inflammatory factors. Inflammatory factors enhance the migration of macrophages to the site of infection and phagocytose bacteria, thereby inhibiting the recurrence of infection. Generally, this engineered L. casei program presents a novel perspective for the treatment of bacterial implant-associated infections and serves as a valuable reference for future clinical applications of engineered probiotics.

A bacteria-responsive nanoplatform with biofilm dispersion and ROS scavenging for the healing of infected diabetic wounds

Delayed wound healing in patients with diabetes remains a major health challenge worldwide. Uncontrolled bacterial infection leads to excessive production of reactive oxygen species (ROS) and persistent inflammatory responses, which seriously hinder conventional physiological healing processes after injury. Biofilms, as protective barriers for bacteria, pose a critical obstacle to effective bacterial eradication. Herein, an innovative therapeutic nanoplatform with in situ antibacterial and antioxidant properties is developed for enhancing infected diabetic wound healing. The enrichment of phenylboronic acid (PBA) moieties on the nanoplatform enhances biofilm penetration, actively anchors and aggregates the enclosed bacteria through the "multivalent effect", with an anchoring efficiency as high as 80 %. Additionally, glycine moieties on the nanoplatform ensure spatial extensibility by charge repulsion, enabling targeted antibiotic release around bacteria. This precise antibacterial effect increases the bactericidal activities of the nanoplatform against S. aureus or P. aeruginosa by 25 % and 22 % respectively, effectively eliminating the bacteria and dispersing the biofilms. Furthermore, 3,4-dihydropyrimidin-2(1H)-one (DHPM) moieties act as ROS scavengers that alleviate oxidative stress and inflammatory responses, promoting tissue repair progression into the proliferative phase characterized by increased extracellular matrix deposition, angiogenesis, and granulation tissue formation, ultimately accelerating diabetic wound healing. Overall, this work presents an innovative bacterial response strategy for achieving in situ antibacterial and antioxidant effects in infected tissues and provides a promising therapeutic approach for treating infected diabetic wounds. STATEMENT OF SIGNIFICANCE: Infected diabetic wound management remains a major world health issue. Severe bacterial infection leads to excessive oxidative stress and persistent inflammatory response, which seriously hinders the wound healing process. As a protective barrier for bacteria, biofilms are a key obstacle to effective bacterial clearance. This study provides a bacteria-responsive nanoplatform for the healing of infected diabetic wounds. The nanoplatform not only exhibits improved biofilm penetration but also actively anchors the enclosed bacteria and enables targeted antibiotic release to disperse the biofilm. The DHPM moieties of the nanoplatform act as ROS scavengers which could alleviate inflammatory responses, promote tissue repair progression into the proliferative phase, and ultimately accelerate diabetic wound repair.

Synergistic photoinduction of ferroptosis and apoptosis by a mitochondria-targeted iridium complex for bladder cancer therapy

Bladder cancer (BC) is one of the most common malignant tumors of the urinary system, and has a high recurrence rate and treatment resistance. Recent results indicate that mitochondrial metabolism influences the therapeutic outcomes of BC. Mitochondria-targeted photosensitizer (PS) is a promising anticancer therapeutic approach that may overcome the limitations of conventional BC treatments. Herein, two mitochondria-targeted iridium(III) PSs, Ir-Mito1 and Ir-Mito2, have been designed for BC treatment. Mechanically, Ir-Mito2 induced a decrease in mitochondrial membrane potential via white light activation, further triggering a reduction of the B-cell lymphoma 2 protein (Bcl-2)/Bcl-associated X protein (Bax) ratio and increment of cleaved caspase3. Meanwhile, the reduction of glutathione, deactivation of glutathione peroxidase 4 (GPX4), increase of acyl-CoA synthetase long chain family member 4 (ACSL4), and accumulation of lipid peroxide resulted in synergistically activating of ferroptosis and apoptosis. The results demonstrated that Ir-Mito2 exhibited excellent antitumor efficacy with superior biosafety in vivo. This work on light-activated and mitochondrial-targeted PS provides an innovative therapeutic platform for BC.

Blue light-activated 5,10,15,20-tetrakis(4-bromophenyl)porphyrin for photodynamic eradication of drug-resistant Staphylococcus aureus

Photodynamic therapy (PDT) has emerged as an effective way to deal with drug-resistant bacterial infections. Especially, blue light (BL) mediated PDT (BL-PDT) presents unique advantages in the treatments of skin infection due to the strong light absorption of superficial skin, weak penetration of BL and little damage to deep tissues. However, the photosensitizers used for BL-PDT are very limited, and the ongoing development of novel BL photosensitizers is indispensable. Porphyrins are good sources for developing efficient photosensitizers. Herein, for developing more effective BL photosensitizers, five porphyrin derivatives that can be excited by BL [5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(4-bromophenyl)porphyrin (TBPP), 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(4-fluorophenyl)porphyrin (TFPP), 5,10,15,20-tetrakis(4-iodophenyl)porphyrin (TIPP)] are subjected to the investigation of PDT against MRSA (methicillin resistant Staphylococcus aureus). The results reveal that TBPP-mediated BL-PDT shows outstanding bactericidal effects. Mechanism studies show that TBPP + BL can induce reactive oxygen species (ROS) up-regulated in MRSA, rupture cell membrane, inhibit ATP (adenosine triphosphate) production and virulence factor expression. Furthermore, TBPP + BL effectively eliminates MRSA form biofilms, inhibits biofilm formation and disintegrates mature biofilms. More importantly, TBPP-PDT significantly accelerate mouse skin wound healing in a biofilm infection model. Our work offers new insights into the development of novel BL photosensitizers.

Photonic hydrogels combining the slow photon effect and NO gas therapy for synergetic enhanced photodynamic antibacterial therapy

Photodynamic therapy (PDT) offers potential for combating bacterial infections through the generation of reactive oxygen species (ROS). However, the antibacterial efficiency of PDT is largely impeded by the limited photon absorption of photosensitizers and the short diffusion length and lifespan of ROS. Herein, we present a light-harvesting platform based on l-arginine-modified photonic hydrogels loaded with new indocyanine green (PG@Arg/IR820) for synergizing the slow photon effect with NO gas therapy to enhance PDT antibacterial efficiency. Upon near-infrared (NIR) light irradiation, PG@Arg/IR820 can maximize the utilization of photons via the slow photon effect to generate sufficient ROS, which not only acts as the primary bactericidal agent in PDT but also triggers l-arginine to generate NO. NO exhibits a long diffusion distance and lifespan and can freely diffuse to inhibit distant bacterial growth, demonstrating a vital complementary advantage in bacterial inactivation by ROS. The synergistic effect of the slow photon effect combined with NO gas therapy allows PG@Arg/IR820 to intensify bacterial destruction and enhance PDT antibacterial efficiency. This antibacterial system sheds light on an advisable design principle for efficient antibacterial activities in photodynamic inactivation.

Plasmonic Supramolecular Nanozyme-Based Bio-Cockleburs for Synergistic Therapy of Infected Diabetic Wounds

Diabetic wounds are a major devastating complication of diabetes due to hyperglycemia, bacterial invasion, and persistent inflammation, and the current antibiotic treatments can lead to the emergence of multidrug-resistant bacteria. Herein, a bimetallic nanozyme-based biomimetic bio-cocklebur (GNR@CeO2@GNPs) is designed and synthesized for diabetic wound management by depositing spiky ceria (CeO2) shells and gold nanoparticles (GNPs) on a gold nanorod (GNR) nanoantenna. The plasmonic-enhanced nanozyme catalysis and self-cascade reaction properties simultaneously boost the two-step enzyme-mimicking catalytic activity of GNR@CeO2@GNPs, leading to a significant improvement in overall therapeutic efficacy rather than mere additive effects. Under the glucose activation and 808 nm laser irradiation, GNR@CeO2@GNPs material captures photons and promotes the transfer of hot electrons from GNR and GNPs into CeO2, realizing a "butterfly effect" of consuming local glucose, overcoming the limited antibacterial efficiency of an individual PTT modality, and providing substantial reactive oxygen species. In vitro and in vivo experiments demonstrate the material's exceptional antibacterial and antibiofilm properties against Gram-negative and Gram-positive bacteria, which can reduce inflammation, promote collagen deposition, and facilitate angiogenesis, thereby accelerating wound healing. This study provides a promising new strategy to develop plasmonic-enhanced nanozymes with a catalytic cascade mode for the antibiotic-free synergistic treatment of infected diabetic wounds.

Mechanism and nanotechnological-based therapeutics for tolerance and resistance of bacterial biofilms

Bacterial biofilms are one of the most relevant drivers of chronic and recurrent infections and a significant healthcare problem. Biofilms were formed by cross-linking of hydrophobic extracellular polymeric substances (EPS), such as proteins, polysaccharides, and eDNA, which were synthesized by bacteria themselves after adhesion and colonization on biological surfaces. They had the characteristics of dense structure and low drug permeability, leading to tolerance and resistance of biofilms to antibiotics and to host responses. Within a biofilm, microbial cells show increased tolerance to both immune system defense mechanisms and antimicrobials than the same cells in the planktonic state. It is one of the key reasons for the failure of traditional clinical drug to treat infectious diseases. Currently, no drugs are available to attack bacterial biofilms in the clinical setting. The development of novel preventive and therapeutic strategies is urgently needed to allow an effective management of biofilm-associated infections. Based on the properties of nanomaterials and biocompatibility, nanotechnology had the advantages of specific targeting, intelligent delivery and low toxicity, which could realize efficient intervention and precise treatment of biofilm-associated infections. In this paper, the mechanisms of bacterial biofilm resistance to antibiotics and host response tolerance were elaborated. Meanwhile, This paper highlighted multiple strategies of biofilms eradication based on nanotechnology. Nanotechnology can interfere with biofilm formation by destroying mature biofilm, modulating biofilm heterogeneity, inhibiting bacterial metabolism, playing antimicrobial properties, activating immunity and enhancing biofilm penetration, which is an important new anti-biofilm preparation. In addition, we presented the key challenges still faced by nanotechnology in combating bacterial biofilm infections. Utilization of nanotechnology safely and effectively should be further strengthened to confirm the safety aspects of their clinical application.

Antibiotic-Augmented Chemodynamic Therapy for Treatment of Helicobacter pylori Infection in the Dynamic Stomach Environment

Helicobacter pylori (H. pylori) is one of the main causes of peptic ulcer disease and gastric cancer. The overuse of antibiotics leads to bacterial drug resistance and disruption to the gut microbiome. Herein, a nanoparticle (TA-FeHMSN@Amox) was developed, comprising amoxicillin (Amox)-loaded iron-engineered hollow mesoporous silica as the core and a metal-polyphenol shell formed by tannic acid (TA) and Fe3+. In acidic stomach conditions, TA-FeHMSN@Amox generates bactericidal ·OH through Fenton/Fenton-like reactions of the degraded product Fe2+ and hydrogen peroxide (H2O2) at the infection site, achieving chemodynamic therapy (CDT). Moreover, released amoxicillin enhances therapeutic efficacy by impeding the self-repair of the bacterial cell wall damaged by CDT, overcoming the limitations of ineffective CDT under conditions lacking sufficient acidity and H2O2. The acidity-responsive CDT combined with reduced antibiotic usage ensures superior in vivo therapeutic efficacy and biocompatibility with intestinal flora, providing a highly potent strategy for treating H. pylori infections in the dynamic stomach environment.

Targeted Sonodynamic Therapy Platform for Holistic Integrative Helicobacter pylori Therapy

Helicobacter pylori (H. pylori) is a primary pathogen associated with gastrointestinal diseases, including gastric cancer. The increase in resistance to antibiotics, along with the adverse effects caused by complicated medication protocols, has made the eradication of H. pylori a more formidable challenge, necessitating alternative therapeutics. Herein, a targeted nanoplatform is reported based on sonodynamic therapy, the chitosan-conjugated fucose loaded with indocyanine green (ICG@FCS). It penetrates the gastric mucosa and homes in on H. pylori through dual targeting mechanisms: molecular via fucose and physical via ultrasound. Upon ultrasound activation, it generates singlet oxygen, effectively attacking planktonic bacteria, disrupting biofilms, and facilitating the clearance of intracellular bacteria by promoting autophagy, including multidrug-resistant strains. The ICG@FCS nanoplatform minimally affects the gut microbiota and aids in gastric mucosa repair. a holistic integrative H. pylori therapy strategy is proposed that targets eradication while preserving gastrointestinal health. This strategy emphasizes the importance of maintaining patient health while eradicating the pathogen. This advancement is set to refine the comprehensive antibacterial approach, offering a promising horizon in the ongoing battle against antibiotic resistance and more effective gastric cancer prevention strategies.

Drug-Free "Triboelectric Immunotherapy" Activating Immunity for Osteomyelitis Treatment and Recurrence Prevention

Treatment of osteomyelitis is clinically challenging with low therapeutic efficacy and high risk of recurrence owing to the immunosuppressive microenvironment. Existing therapies are limited by drug concentration and single regulatory effect on the immune network, and emphasize the role of anti-inflammatory effects in reducing osteoclast rather than the role of proinflammatory effects in accelerating infection clearance, which is not conducive to complete bacteria elimination and recurrence prevention. Herein, a direct-current triboelectric nanogenerator (DC-TENG) is established to perform antibacterial effects and modulate immunological properties of infectious microenvironments of osteomyelitis through electrical stimulation, namely triboelectric immunotherapy. Seeing from the results, the triboelectric immunotherapy successfully activates polarization to proinflammatory (M1) macrophages in vitro, accompanied by satisfying direct antibacterial effects. The antibacterial and osteogenic abilities of triboelectric immunotherapy are verified in rat cranial osteomyelitis models. The effects on the polarization and differentiation of immune-related cells in vivo are investigated by establishing in situ tibial osteomyelitis models and immunosurveillance models in C57 mice respectively, indicating the ability of activating immunity and producing immunological memory for in situ infection and secondary recurrence, thus accelerating healing and preventing relapse. This study provides an efficient, long-acting, multifunctional, and wearable triboelectric immunotherapy strategy for drug-free osteomyelitis treatment systems.

Ultrasound-Activated Probiotics Vesicles Coating for Titanium Implant Infections Through Bacterial Cuproptosis-Like Death and Immunoregulation

Implant-associated infections (IAIs) are the main cause of prosthetic implant failure. Bacterial biofilms prevent antibiotic penetration, and the unique metabolic conditions in hypoxic biofilm microenvironment may limit the efficacy of conventional antibiotic treatment. Escaping survival bacteria may not be continually eradicated, resulting in the recurrence of IAIs. Herein, a sonosensitive metal-organic framework of Cu-TCPP (tetrakis(4-carboxyphenyl) porphyrin) nanosheets and tinidazole doped probiotic-derived membrane vesicles (OMVs) with high-penetration sonodynamic therapy (SDT), bacterial metabolic state interference, and bacterial cuproptosis-like death to eradicate IAIs is proposed. The Cu-TCPP can convert O2 to toxic 1O2 through SDT in the normoxic conditions, enhancing the hypoxic microenvironment and activating the antibacterial activity of tinidazole. The released Cu(II) under ultrasound can be converted to Cu(I) by exogenous poly(tannic acid) (pTA) and endogenous glutathione. The disruption of the bacterial membrane by SDT can enhance the Cu(I) transporter activity. Transcriptomics indicate that the SDT-enhanced Cu(I) overload and hypoxia-activated therapy hinder the tricarboxylic acid cycle (TCA), leading to bacterial cuproptosis-like death. Moreover, the OMVs-activated therapy can polarize macrophages to a M2-like phenotype and facilitate bone repair. The sonodynamic biofilm microenvironment modulation strategy, whereby the hypoxia-enhanced microenvironment is potentiated to synergize SDT with OMVs-activated therapy, provides an effective strategy for antibacterial and osteogenesis performance.

A Supramolecular Nanoformulation with Adaptive Photothermal/Photodynamic Transformation for Preventing Dental Caries

In the context of an increasingly escalating antibiotics crisis, phototherapy has emerged as a promising therapeutic approach due to its inherent advantages, including high selectivity, noninvasiveness, and low drug resistance. Photothermal therapy (PTT) and photodynamic therapy (PDT) are two complementary and promising phototherapies albeit with inherent limitations, noted as the challenges in achieving precise heat confinement and the associated risk of off-target damage for PTT, while the constraints due to the hypoxic microenvironment are prevalent in biofilms faced by PDT. Herein, we have designed a supramolecular nanoformulation that leverages the complexation-induced quenching of guanidinium-modified calix[5]arene grafted with fluorocarbon chains (GC5AF5), the efficient recognition of adenosine triphosphate (ATP), and the oxygen-carrying capacity of the fluorocarbon chain. This intelligent nanoformulation enables the adaptive enhancement of both photothermal therapy (PTT) and photodynamic therapy (PDT), allowing for on-demand switching between the two modalities. Our nanoformulation utilizes ATP released by dead bacteria to accelerate the elimination of biofilms, rendering bacteria unable to resist while minimizing harm to healthy tissues. This research highlights the particular recognition and assembly capabilities of macrocycles, offering a promising strategy for creating potent, combined antibiofilm therapies.

Bacteriophage-mediated approaches for biofilm control

Biofilms are complex microbial communities in which planktonic and dormant bacteria are enveloped in extracellular polymeric substances (EPS) such as exopolysaccharides, proteins, lipids, and DNA. These multicellular structures present resistance to conventional antimicrobial treatments, including antibiotics. The formation of biofilms raises considerable concern in healthcare settings, biofilms can exacerbate infections in patients and compromise the integrity of medical devices employed during treatment. Similarly, certain bacterial species contribute to bulking, foaming, and biofilm development in water environments such as wastewater treatment plants, water reservoirs, and aquaculture facilities. Additionally, food production facilities provide ideal conditions for establishing bacterial biofilms, which can serve as reservoirs for foodborne pathogens. Efforts to combat antibiotic resistance involve exploring various strategies, including bacteriophage therapy. Research has been conducted on the effects of phages and their individual proteins to assess their potential for biofilm removal. However, challenges persist, prompting the examination of refined approaches such as drug-phage combination therapies, phage cocktails, and genetically modified phages for clinical applications. This review aims to highlight the progress regarding bacteriophage-based approaches for biofilm eradication in different settings.

Wake biofilm up to enhance suicidal uptake of gallium for chronic lung infection treatment

The hypometabolic and nutrient-limiting condition of dormant bacteria inside biofilms reduces their susceptibility to antibacterial agents, making the treatment of biofilm-dominating chronic infections difficult. Herein, we demonstrate an intratracheal aerosolized maltohexaose-modified catalase-gallium integrated nanosystem that can 'wake up' dormant Pseudomonas aeruginosa biofilm to increase the metabolism and nutritional iron demand by reconciling the oxygen gradient. The activated bacteria then enhance suicidal gallium uptake since gallium acts as a 'Trojan horse' to mimic iron. The internalized gallium ions disrupt biofilms by interfering with the physiological processes of iron ion acquisition and utilization, biofilm formation, and quorum sensing. Furthermore, aerosol microsprayer administration and bacteria-specific maltohexaose modification enable accumulation at biofilm-infected lung and targeted release of gallium into bacteria to improve the therapeutic effect. This work provides a potential strategy for treating infection by reversing the dormant biofilm's resistance condition.

Strain-Programmed Adhesive Patch for Accelerated Photodynamic Wound Healing

As an alternative to tissue adhesives, photochemical tissue bonding is investigated for advanced wound healing. However, these techniques suffer from relatively slow wound healing with bleeding and bacterial infections. Here, the versatile attributes of afterglow luminescent particles (ALPs) embedded in dopamine-modified hyaluronic acid (HA-DOPA) patches for accelerated wound healing are presented. ALPs enhance the viscoelastic properties of the patches, and the photoluminescence and afterglow luminescence of ALPs maximize singlet oxygen generation and collagen fibrillogenesis for effective healing in the infected wounds. The patches are optimized to achieve the strong and rapid adhesion in the wound sites. In addition, the swelling and shrinking properties of adhesive patches contribute to a nonlinear behavior in the wound recovery, playing an important role as a strain-programmed patch. The protective patch prevents secondary infection and skin adhesion, and the patch seamlessly detaches during wound healing, enabling efficient residue clearance. In vitro, in vivo, and ex vivo model tests confirm the biocompatibility, antibacterial effect, hemostatic capability, and collagen restructuring for the accelerated wound healing. Taken together, this research collectively demonstrates the feasibility of HA-DOPA/ALP patches as a versatile and promoting solution for advanced accelerated wound healing, particularly in scenarios involving bleeding and bacterial infections.

Acidic biofilm microenvironment-responsive ROS generation via a protein nanoassembly with hypoxia-relieving and GSH-depleting capabilities for efficient elimination of biofilm bacteria

Reactive oxygen species (ROS) are widely considered to the effective therapeutics for fighting bacterial infections especially those associated with biofilm. However, biofilm microenvironments including hypoxia, limited H2O2, and high glutathione (GSH) level seriously limit the therapeutic efficacy of ROS-based strategies. Herein, we have developed an acidic biofilm microenvironment-responsive antibacterial nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The three-in-one nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in a slightly acidic environment, where Cu2+ catalyzes the conversion of H2O2 into hydroxyl radical (•OH) and consumes the highly expressed GSH to disrupt the redox homeostasis. With the assistance of an 808 nm laser, the loaded ICG not only triggers the production of singlet oxygen (1O2) by a photodynamic process, but also provides photonic hyperpyrexia that further promotes the Fenton-like reaction for enhancing •OH production and induces thermal decomposition of CuO2 for the O2-self-supplying 1O2 generation. The CuO2/ICG@CBSA with laser irradiation demonstrates photothermal-augmented multi-mode synergistic bactericidal effect and is capable of inhibiting biofilm formation and eradicating the biofilm bacteria. Further in vivo experiments suggest that the CuO2/ICG@CBSA can effectively eliminate wound infections and accelerate wound healing. The proposed three-in-one nanotherapeutics with O2/H2O2-self-supplied ROS generating capability show great potential in treating biofilm-associated bacterial infections. STATEMENT OF SIGNIFICANCE: Here, we have developed an acidic biofilm microenvironment-responsive nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in an acidic environment, where Cu2+ catalyzes the conversion of H2O2 into •OH and consumes the overexpressed GSH to improve oxidative stress. With the aid of an 808 nm laser, ICG provides photonic hyperpyrexia for enhancing •OH production, and triggers O2-self-supplying 1O2 generation. CuO2/ICG@CBSA with laser irradiation displays photothermal-augmented multi-mode antibacterial and antibiofilm effect. Further in vivo experiments prove that CuO2/ICG@CBSA effectively eliminates wound infection and promotes wound healing. The proposed three-in-one nanotherapeutics show great potential in treating biofilm-associated bacterial infections.

Simultaneous Biofilm Disruption, Bacterial Killing, and Inflammation Elimination for Wound Treatment Using Silver Embellished Polydopamine Nanoplatform

Due to the presence of spatial barriers, persistent bacteria, and excessive inflammation in bacteria biofilm-infected wounds, current nanoplatforms cannot effectively address these issues simultaneously during the therapeutic process. Herein, a novel biomimetic photothermal nanoplatform integrating silver and polydopamine nanoparticles (Ag/PDAs) that can damage biofilms, kill bacterial persisters, and reduce inflammation for wound treatment is presented. These findings reveal that Ag/PDAs exhibit a broad-spectrum antimicrobial activity through direct damage to the bacterial membrane structure. Additionally, Ag/PDAs demonstrate a potent photothermal conversion efficiency. When combined with near-infrared (NIR) irradiation, Ag/PDAs effectively disrupt the spatial structure of biofilms and synergistically eradicate the resident bacteria. Furthermore, Ag/PDAs show remarkable anti-inflammatory properties in counteracting bacterium-induced macrophage polarization. The in vivo results confirm that the topical application of Ag/PDAs significantly suppress Staphylococcus aureus biofilm-infected wounds in murine models, concurrently facilitating wound healing. This research provides a promising avenue for the eradication of bacterial biofilms and the treatment of biofilm-infected wounds.

Unexpectedly high antibacterial ability of water in copper pot with tiny amount of plant leaves

Water disinfection by copper vessels has been prevalent over thousands of years. Unfortunately, people are still suffering from the bacterial pollution in drinking water. Here we show that, only through steeping with tiny amounts of common plant leaves, the room-temperature water in copper pots has unexpectedly high antibacterial ability. Remarkably, copper ions released from copper pots into water are in concentrations lower than the WHO safety threshold for drinking water, and have effective antibacterial ability when water contains specific leave components (polyphenols and/or lignin). Our computations show that the key to enhance antibacterial ability is the great increase in the proportion of Cu+ induced by aromatic rings in these leave components, which has been demonstrated by our experiments. The findings may disclose the mystery of copper vessels for water disinfection, and more importantly, provide effective antibacterial applications in industries and daily lives, by safely using copper ions together with biocompatible natural substances.

Integrated design and application of stimuli-responsive metal-organic frameworks in biomedicine: current status and future perspectives

In recent years, metal-organic frameworks (MOFs) have garnered widespread attention due to their distinctive attributes, such as high surface area, tunable properties, biodegradability, extremely low density, high loading capacity, diverse chemical functionalities, thermal stability, well-defined pore sizes, and molecular dimensions. Increasingly, biomedical researchers have turned their focus towards their multifaceted development. Among these, stimuli-responsive MOFs, with their unique advantages, have captured greater interest from researchers. This review will delve into the merits and drawbacks of both endogenous and exogenous stimuli-responsive MOFs, along with their application directions. Furthermore, it will outline the characteristics of different synthesis routes of MOFs, exploring various design schemes and modification strategies and their impacts on the properties of MOF products, as well as how to control them. Additionally, we will survey different types of stimuli-responsive MOFs, discussing the significance of various MOF products reported in biomedical applications. We will categorically summarize different strategies such as anticancer therapy, antibacterial treatment, tissue repair, and biomedical imaging, as well as insights into the development of novel MOFs nanomaterials in the future. Finally, this review will conclude by summarizing the challenges in the development of stimuli-responsive MOFs in the field of biomedicine and providing prospects for future research endeavors.

Structurally Oriented Carbon Dots as ROS Nanomodulators for Dynamic Chronic Inflammation and Infection Elimination

The selective elimination of cytotoxic ROS while retaining essential ones is pivotal in the management of chronic inflammation. Co-occurring bacterial infection further complicates the conditions, necessitating precision and an efficacious treatment strategy. Herein, the dynamic ROS nanomodulators are rationally constructed through regulating the surface states of herbal carbon dots (CDs) for on-demand inflammation or infection elimination. The phenolic OH containing CDs derived from honeysuckle (HOCD) and dandelion (DACD) demonstrated appropriate redox potentials, ensuring their ability to scavenge cytotoxic ROS such as ·OH and ONOO-, while invalidity toward essential ones such as O2·-, H2O2, and NO. This enables efficient treatment of chronic inflammation without affecting essential ROS signal pathways. The surface C-N/C═N of CDs derived from taxus leaves (TACD) and DACD renders them with suitable band structures, facilitating absorption in the red region and efficient generation of O2·- upon light irradiation for sterilization. Specifically, the facilely prepared DACD demonstrates fascinating dynamic ROS modulating ability, making it highly suitable for addressing concurrent chronic inflammation and infection, such as diabetic wound infection. This dynamic ROS regulation strategy facilitates the realization of the precise and efficient treatment of chronic inflammation and infection with minimal side effects, holding immense potential for clinical practice.

Flexible nanoplatform facilitates antibacterial phototherapy by simultaneously enhancing photosensitizer permeation and relieving hypoxia in bacterial biofilms

Antimicrobial phototherapy has gained recognition as a promising approach for addressing bacterial biofilms, however, its effectiveness is often impeded by the robust physical and chemical defenses of the biofilms. Traditional antibacterial nanoplatforms face challenges in breaching the extracellular polymeric substances barrier to efficiently deliver photosensitizers deep into biofilms. Moreover, the prevalent hypoxia within biofilms restricts the success of oxygen-reliant phototherapy. In this study, we engineered a soft mesoporous organosilica nanoplatform (SMONs) by incorporating polyethylene glycol (PEG), catalase (CAT), and indocyanine green (ICG), forming SMONs-PEG-CAT-ICG (SPCI). We compared the antimicrobial efficacy of SPCI with more rigid nanoplatforms. Our results demonstrated that unique flexible mechanical properties of SPCI enable it to navigate through biofilm barriers, markedly enhancing ICG penetration in methicillin-resistant Staphylococcus aureus (MRSA) biofilms. Notably, in a murine subcutaneous MRSA biofilm infection model, SPCI showed superior biofilm penetration and pharmacokinetic benefits over its rigid counterparts. The embedded catalase in SPCI effectively converts excess H2O2 present in infected tissues into O2, alleviating hypoxia and significantly boosting the antibacterial performance of phototherapy. Both in vitro and in vivo experiments confirmed that SPCI surpasses traditional rigid nanoplatforms in overcoming biofilm barriers, offering improved treatment outcomes for infections associated with bacterial biofilms. This study presents a viable strategy for managing bacterial biofilm-induced diseases by leveraging the unique attributes of a soft mesoporous organosilica-based nanoplatform. STATEMENT OF SIGNIFICANCE: This research introduces an innovative antimicrobial phototherapy soft nanoplatform that overcomes the inherent limitations posed by the protective barriers of bacterial biofilms. By soft nanoplatform with flexible mechanical properties, we enhance the penetration and delivery of photosensitizers into biofilms. The inclusion of catalase within this soft nanoplatform addresses the hypoxia in biofilms by converting hydrogen peroxide into oxygen in infected tissues, thereby amplifying the antibacterial effectiveness of phototherapy. Compared to traditional rigid nanoplatforms, this flexible nanoplatform not only promotes the delivery of therapeutic agents but also sets a new direction for treating bacterial biofilm infections, offering significant implications for future antimicrobial therapies.

Janus liposozyme for the modulation of redox and immune homeostasis in infected diabetic wounds

Diabetic foot ulcers often become infected, leading to treatment complications and increased risk of loss of limb. Therapeutics to manage infection and simultaneously promote healing are needed. Here we report on the development of a Janus liposozyme that treats infections and promotes wound closure and re-epithelialization. The Janus liposozyme consists of liposome-like selenoenzymes for reactive oxygen species (ROS) scavenging to restore tissue redox and immune homeostasis. The liposozymes are used to encapsulate photosensitizers for photodynamic therapy of infections. We demonstrate application in methicillin-resistant Staphylococcus aureus-infected diabetic wounds showing high ROS levels for antibacterial function from the photosensitizer and nanozyme ROS scavenging from the liposozyme to restore redox and immune homeostasis. We demonstrate that the liposozyme can directly regulate macrophage polarization and induce a pro-regenerative response. By employing single-cell RNA sequencing, T cell-deficient Rag1-/- mice and skin-infiltrated immune cell analysis, we further reveal that IL-17-producing γδ T cells are critical for mediating M1/M2 macrophage transition. Manipulating the local immune homeostasis using the liposozyme is shown to be effective for skin wound repair and tissue regeneration in mice and mini pigs.

Robust Gradient Hydrogel-Loaded Nanofiber Fleshy Artificial Skin Via A Coupled Microfluidic Electrospinning-Reactive Coating Strategy

Skin regeneration attracts tremendous interest due to the important role of skin for human protection and beauty. Thus, methods allowing artificial skin to be carried out in a controllable fashion are potentially important for wound healing, which involves an intersection of materials, medicine, biology, and other disciplines. Herein, aiming at a new general methodology for fleshy materials, a new hydrogel-loaded hydrophobic-hydrophilic nanofiber fleshy artificial skin is designed and fabricated. The gradient hydrogel-loaded nanofiber artificial skin integrates both advantages of nanofiber and hydrogel, exhibiting fleshy feature (comparability to real skin in terms of appearance, texture, and function), excellent air permeability, compatibility, and good mechanical and antibacterial property. Interestingly, the efficient transport channels are formed throughout the hydrogel-loaded nanofiber structure, which is beneficial for water absorption and transfer. These advantages enable the establishment of a moist and favorable microenvironment; thus, greatly accelerating wound healing process. This work couples microfluidic electrospinning with reactive coating technique, which is in favor of material design and fabrication with controllable and uniform structures. The hydrogel-loaded nanofiber fleshy artificial skin shows comparability to real skin in terms of beauty, texture, and function, which would definitely provide new opportunities for the further optimization and upgrading of artificial skin.

Nitroreductase-responsive nanoparticles for in situ fluorescence imaging and synergistic antibacterial therapy of bacterial keratitis

As bacterial keratitis progresses rapidly, prompt intervention is necessary. Current diagnostic processes are time-consuming and invasive, leading to improper antibiotics for treatment. Therefore, innovative strategies for diagnosing and treating bacterial keratitis are urgently needed. In this study, Cu2-xSe@BSA@NTRP nanoparticles were developed by loading nitroreductase-responsive probes (NTRPs) onto Cu2-xSe@BSA. These nanoparticles exhibited integrated fluorescence imaging and antibacterial capabilities. In vitro and in vivo experiments showed that the nanoparticles produced responsive fluorescence signals in bacteria within 30 min due to an interaction between the released NTRP and bacterial endogenous nitroreductase (NTR). When combined with low-temperature photothermal therapy (PTT), the nanoparticles effectively eliminated E. coli and S. aureus, achieved antibacterial efficacy above 95% and facilitated the re-epithelialization process at the corneal wound site in vivo. Overall, the Cu2-xSe@BSA@NTRP nanoparticles demonstrated potential for rapid, noninvasive in situ diagnosis, treatment, and visualization assessment of therapy effectiveness in bacterial keratitis.

Photodynamic treatment of Staphylococcus aureus with non-iron hemin analogs in the presence of hydrogen peroxide

Bacteria subjected to antiseptic or antibiotic stress often develop tolerance, a trait that can lead to permanent resistance. To determine whether photodynamic agents could be used to counter tolerance, we evaluated three non-iron hemin analogs (M-PpIX; M = Al, Ga, In) as targeted photosensitizers for antimicrobial photodynamic inactivation (aPDI) following exposure to sublethal H2O2. Al-PpIX is an active producer of ROS whereas Ga- and In-PpIX are more efficient at generating singlet oxygen. Al- and Ga-PpIX are highly potent aPDI agents against S. aureus and methicillin-resistant strains (MRSA) with antimicrobial activity (3 log reduction in colony-forming units) at nanomolar concentrations. The aPDI activities of Al- and Ga-PpIX against S. aureus were tested in the presence of 1 mM H2O2 added at different stages of growth. Bacteria exposed to H2O2 during log-phase growth were less susceptible to aPDI but bacteria treated with H2O2 in their postgrowth phase exhibited aPDI hypersensitivity, with no detectable colony growth after treatment with 15 nM Ga-PpIX.

Near-Infrared Light-Triggered NO Nanogenerator for Gas-Enhanced Photodynamic Therapy and Low-Temperature Photothermal Therapy to Eliminate Biofilms

Purpose

Owing to its noninvasive nature, broad-spectrum effectiveness, minimal bacterial resistance, and high efficiency, phototherapy has significant potential for antibiotic-free antibacterial interventions and combating antibacterial biofilms. However, finding effective strategies to mitigate the detrimental effects of excessive temperature and elevated concentrations of reactive oxygen species (ROS) remains a pressing issue that requires immediate attention.

Methods

In this study, we designed a pH-responsive cationic polymer sodium nitroside dihydrate/branched polyethylenimine-indocyanine green@polyethylene glycol (SNP/PEI-ICG@PEG) nanoplatform using the electrostatic adsorption method and Schiff's base reaction. Relevant testing techniques were applied to characterize and analyze SNP/PEI-ICG@PEG, proving the successful synthesis of the nanomaterials. In vivo and in vitro experiments were performed to evaluate the antimicrobial properties of SNP/PEI-ICG@PEG.

Results

The morphology and particle size of SNP/PEI-ICG@PEG were observed via TEM. The zeta potential and UV-visible (UV-vis) results indicated the synthesis of the nanomaterials. The negligible cytotoxicity of up to 1 mg/mL of SNP/PEI-ICG@PEG in the presence or absence of light demonstrated its biosafety. Systematic in vivo and in vitro antimicrobial assays confirmed that SNP/PEI-ICG@PEG had good water solubility and biosafety and could be activated by near-infrared (NIR) light and synergistically treated using four therapeutic modes, photodynamic therapy (PDT), gaseous therapy (GT), mild photothermal therapy (PTT, 46 °C), and cation. Ultimately, the development of Gram-positive (G+) Staphylococcus aureus (S. aureus) and Gram-negative (G-) Escherichia coli (E. coli) were both completely killed in the free state, and the biofilm that had formed was eliminated.

Conclusion

SNP/PEI-ICG@PEG demonstrated remarkable efficacy in achieving controlled multimodal synergistic antibacterial activity and biofilm infection treatment. The nanoplatform thus holds promise for future clinical applications.

Metabolic Modulation-Mediated Antibiotic and Immune Activation for Treatment of Chronic Lung Infections

The Pseudomonas aeruginosa biofilm in recalcitrant chronic lung infections not only develops high antimicrobial tolerance but also induces an aberrant host inflammatory response. The metabolic condition plays a vital role in both the antimicrobial susceptibility of bacteria and the inflammatory response of immune cells, thereby offering a potential therapeutic target. Herein, we described a metabolic modulation strategy by using ultrasound-responsive liposomal nanoparticles containing a sonosensitizer and a hypoxia-activated prodrug against biofilm-associated chronic lung infections. Under ultrasound stimulation, the sonosensitizer generates antibacterial reactive oxygen species by oxygen consumption. Subsequently, the oxygen consumption-mediated hypoxia not only induces the anaerobic metabolism of bacteria for antibiotic activation but also triggers the glycolysis pathway of immune cells for inflammatory activation. Such metabolic modulation strategy demonstrated efficient therapeutic efficacy for P. aeruginosa biofilm-induced chronic lung infections in mice models and provides a promising way for combating biofilm-associated chronic infections.

Thymoquinone as an electron transfer mediator to convert Type II photosensitizers to Type I photosensitizers

The development of Type I photosensitizers (PSs) is of great importance due to the inherent hypoxic intolerance of photodynamic therapy (PDT) in the hypoxic microenvironment. Compared to Type II PSs, Type I PSs are less reported due to the absence of a general molecular design strategy. Herein, we report that the combination of typical Type II PS and natural substrate carvacrol (CA) can significantly facilitate the Type I pathway to efficiently generate superoxide radical (O2-•). Detailed mechanism study suggests that CA is activated into thymoquinone (TQ) by local singlet oxygen generated from the PS upon light irradiation. With TQ as an efficient electron transfer mediator, it promotes the conversion of O2 to O2-• by PS via electron transfer-based Type I pathway. Notably, three classical Type II PSs are employed to demonstrate the universality of the proposed approach. The Type I PDT against S. aureus has been demonstrated under hypoxic conditions in vitro. Furthermore, this coupled photodynamic agent exhibits significant bactericidal activity with an antibacterial rate of 99.6% for the bacterial-infection female mice in the in vivo experiments. Here, we show a simple, effective, and universal method to endow traditional Type II PSs with hypoxic tolerance.

Photochemical Strategies toward Precision Targeting against Multidrug-Resistant Bacterial Infections

Infectious diseases pose a serious threat and a substantial economic burden on global human and public health security, especially with the frequent emergence of multidrug-resistant (MDR) bacteria in clinical settings. In response to this urgent need, various photobased anti-infectious therapies have been reported lately. This Review explores and discusses several photochemical targeted antibacterial therapeutic strategies for addressing bacterial infections regardless of their antibiotic susceptibility. In contrast to conventional photobased therapies, these approaches facilitate precise targeting of pathogenic bacteria and/or infectious microenvironments, effectively minimizing toxicity to mammalian cells and surrounding healthy tissues. The highlighted therapies include photodynamic therapy, photocatalytic therapy, photothermal therapy, endogenous pigments-based photobleaching therapy, and polyphenols-based photo-oxidation therapy. This comprehensive exploration aims to offer updated information to facilitate the development of effective, convenient, safe, and alternative strategies to counter the growing threat of MDR bacteria in the future.

Aggregation-induced emission photosensitizer for antibacterial therapy of methicillin-resistant Staphylococcus aureus

A cationic aggregation-induced emission photosensitizer (AIE-PS) MNNPyBB has been reported to have antibacterial effects against both Gram-positive and Gram-negative bacteria. The bacterial kill mechanism has been investigated and elucidated. In a methicillin-resistant Staphylococcus aureus subcutaneous infection model, wound closure has been achieved with normal re-epithelialization and preserved skin morphology.

Light-induced antimicrobial activities of porphyrin derivatives as photosensitizers

Antimicrobial photodynamic therapy has considerable promise in the fight against bacterial infections. The superior photophysical characteristics of porphyrins have made them effective photosensitizers in the field of phototherapy. Herein, the light-induced antimicrobial effects of three porphyrins with different substituents have been compared. 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (THPP) shows superior photosensitizing activity and antimicrobial ability under irradiation with green light. THPP can also inhibit and destroy mature Staphylococcus aureus biofilms under irradiation. This work provides a reference for the rational design of photosensitizers for application in antimicrobial photodynamic therapy.

Charge adaptive phytochemical-based nanoparticles for eradication of methicillin-resistant staphylococcus aureus biofilms

The intrinsic resistance of MRSA coupled with biofilm antibiotic tolerance challenges the antibiotic treatment of MRSA biofilm infections. Phytochemical-based nanoplatform is a promising emerging approach for treatment of biofilm infection. However, their therapeutic efficacy was restricted by the low drug loading capacity and lack of selectivity. Herein, we constructed a surface charge adaptive phytochemical-based nanoparticle with high isoliquiritigenin (ISL) loading content for effective treatment of MRSA biofilm. A dimeric ISL prodrug (ISL-G2) bearing a lipase responsive ester bond was synthesized, and then encapsulated into the amphiphilic quaternized oligochitosan. The obtained ISL-G2 loaded NPs possessed positively charged surface, which allowed cis-aconityl-d-tyrosine (CA-Tyr) binding via electrostatic interaction to obtain ISL-G2@TMDCOS-Tyr NPs. The NPs maintained their negatively charged surface, thus prolonging the blood circulation time. In response to low pH in the biofilms, the fast removal of CA-Tyr led to a shift in their surface charge from negative to positive, which enhanced the accumulation and penetration of NPs in the biofilms. Sequentially, the pH-triggered release of d-tyrosine dispersed the biofilm and lipase-triggered released of ISL effectively kill biofilm MRSA. An in vivo study was performed on a MRSA biofilm infected wound model. This phytochemical-based system led to ∼2 log CFU (>99 %) reduction of biofilm MRSA as compared to untreated wound (P < 0.001) with negligible biotoxicity in mice. This phytochemical dimer nanoplatform shows great potential for long-term treatment of resistant bacterial infections.

A type I and type II chemical biology toolbox to overcome the hypoxic tumour microenvironment for photodynamic therapy

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality employed for the treatment of various types of cancers, localized infections, and other diseases. Upon illumination, the photo-excited photosensitizer generates singlet oxygen and other reactive species, thereby inducing cytotoxicity in the target cells. The hypoxic tumour microenvironment (TME), however, poses a limitation on the supply of oxygen in tumour tissues. Moreover, under such conditions, tumour metastasis and drug resistance frequently occur, further compromising the efficacy of PDT in combating tumours. Traditionally, type I photosensitizers with lower oxygen consumption demonstrate significant potential in overcoming hypoxic environments and play a crucial role in determining the therapeutic efficacy of PDT because type I photosensitizers can generate highly cytotoxic free radicals. In comparison, type II photosensitizers exhibit high oxygen dependence. The rate of reactive oxygen species (ROS) generation in the type II process is significantly higher than that in the type I process. Thus, the efficiency and selectivity of PDT depend on the properties of the photosensitizer. Here, the recent development and application of type I and type II photosensitizers, mainly in the past year, are summarized. The design methods, electronic structures, photophysical properties, lipophilic properties, electric charge, and other molecular characteristics of these photosensitizers are discussed in detail. These modifications alter the microstructure of photosensitizers and directly impact the results of PDT. The main content of this paper will have a positive promoting and inspiring effect on the future development of PDT.

Highly Efficient Photodynamic Hydrogel with AIE-Active Photosensitizers toward Methicillin-Resistant Staphylococcus aureus Ultrafast Imaging and Killing

Methicillin-resistant Staphylococcus aureus (MRSA) causes great health hazards to society because most antibiotics are ineffective. Photodynamic treatment (PDT) has been proposed to combat MRSA due to the advantage of imaging-guided no-drug resistance therapy. However, the traditional photosensitizers for PDT are limited by aggregation-caused quenching for imaging and low photodynamic antibacterial efficiency. In this work, we synthesize a new aggregation-induced emission (AIE) photosensitizer (APNO), which can ultrafast distinguish between Gram-positive and Gram-negative bacteria within 3 s by AIE-active photosensitizer imaging. Meanwhile, APNO can generate antibacterial reactive oxygen species under light irradiation, which holds potential for antibacterial PDT. Then, APNO is loaded by PHEAA hydrogel to obtain a highly efficient photodynamic hydrogel (APNO@gel). In vitro results show complete inhibition of MRSA by APNO@gel under lower-power light irradiation. Transcriptome analysis is performed to investigate antibacterial mechanism of APNO@gel. Most importantly, APNO@gel also exhibits significant inhibition and killing ability of MRSA in the MRSA wound infection model, which will further promote rapid wound healing. Therefore, the photodynamic hydrogel provides a promising strategy toward MRSA ultrafast imaging and killing.

Enhanced Chemoradiotherapy for MRSA-Infected Osteomyelitis Using Immunomodulatory Polymer-Reinforced Nanotherapeutics

The eradication of osteomyelitis caused by methicillin-resistant Staphylococcus aureus (MRSA) poses a significant challenge due to its development of biofilm-induced antibiotic resistance and impaired innate immunity, which often leads to frequent surgical failure. Here, the design, synthesis, and performance of X-ray-activated polymer-reinforced nanotherapeutics that modulate the immunological properties of infectious microenvironments to enhance chemoradiotherapy against multidrug-resistant bacterial deep-tissue infections are reported. Upon X-ray radiation, the proposed polymer-reinforced nanotherapeutic generates reactive oxygen species and reactive nitrogen species. To robustly eradicate MRSA biofilms at deep infection sites, these species can specifically bind to MRSA and penetrate biofilms for enhanced chemoradiotherapy treatment. X-ray-activated nanotherapeutics modulate the innate immunity of macrophages to prevent the recurrence of osteomyelitis. The remarkable anti-infection effects of these nanotherapeutics are validated using a rat osteomyelitis model. This study demonstrates the significant potential of a synergistic chemoradiotherapy and immunotherapy method for treating MRSA biofilm-infected osteomyelitis.

Dissolving microneedle system containing Ag nanoparticle-decorated silk fibroin microspheres and antibiotics for synergistic therapy of bacterial biofilm infection

Most cases of delayed wound healing are associated with bacterial biofilm infections due to high antibiotic resistance. To improve patient compliance and recovery rates, it is critical to develop minimally invasive and efficient methods to eliminate bacterial biofilms as an alternative to clinical debridement techniques. Herein, we develop a dissolving microneedle system containing Ag nanoparticles (AgNPs)-decorated silk fibroin microspheres (SFM-AgNPs) and antibiotics for synergistic treatment of bacterial biofilm infection. Silk fibroin microspheres (SFM) are controllably prepared in an incompatible system formed by a mixture of protein and carbohydrate solutions by using a mild all-aqueous phase method and serve as biological templates for the synthesis of AgNPs. The SFM-AgNPs exert dose- and time-dependent broad-spectrum antibacterial effects by inducing bacterial adhesion. The combination of SFM-AgNPs with antibiotics breaks the limitation of the antibacterial spectrum and achieves better efficacy with reduced antibiotic dosage. Using hyaluronic acid (HA) as the soluble matrix, the microneedle system containing SFM-AgNPs and anti-Gram-positive coccus drug (Mupirocin) inserts into the bacterial biofilms with sufficient strength, thereby effectively delivering the antibacterial agents and realizing good antibiofilm effect on Staphylococcus aureus-infected wounds. This work demonstrates the great potential for the development of novel therapeutic systems for eradicating bacterial biofilm infections.

Chaotropic Effect-Induced Sol-Gel Transition and Radical Stabilization for Bacterially Sensitive Near-Infrared Photothermal Therapy

Deep-seated bacterial infections (DBIs) are stubborn and deeply penetrate tissues. Eliminating deep-seated bacteria and promoting tissue regeneration remain great challenges. Here, a novel radical-containing hydrogel (SFT-B Gel) cross-linked by a chaotropic effect was designed for the sensing of DBIs and near-infrared photothermal therapy (NIR-II PTT). A silk fibroin solution stained with 4,4',4″-(1,3,5-triazine-2,4,6-triyl)tris(1-methylpyridin-1-ium) (TPT3+) was employed as the backbone, which could be cross-linked by a closo-dodecaborate cluster (B12H122-) through a chaotropic effect to form the SFT-B Gel. More interestingly, the SFT-B Gel exhibited the ability to sense DBIs, which could generate a TPT2+• radical with obvious color changes in the presence of bacteria. The radical-containing SFT-B Gel (SFT-B★ Gel) possessed strong NIR-II absorption and a remarkable photothermal effect, thus demonstrating excellent NIR-II PTT antibacterial activity for the treatment of DBIs. This work provides a new approach for the construction of intelligent hydrogels with unique properties using a chaotropic effect.

Repurposing cinacalcet suppresses multidrug-resistant Staphylococcus aureus by disruption of cell membrane and inhibits biofilm by targeting IcaR

BACKGROUND

MDR Staphylococcus aureus infections, along with the severity of biofilm-associated infections, continue to threaten human health to a great extent. It necessitates the urgent development of novel antimicrobial and antibiofilm agents.

OBJECTIVES

To reveal the mechanism and target of cinacalcet as an antibacterial and antimicrobial agent for S. aureus.

METHODS

Screening of non-antibiotic drugs for antibacterial and antibiofilm properties was conducted using a small-molecule drug library. In vivo efficacy was assessed through animal models, and the antibacterial mechanism was studied using quantitative proteomics, biochemical assays, LiP-SMap, BLI detection and gene knockout techniques.

RESULTS

Cinacalcet, an FDA-approved drug, demonstrated antibacterial and antibiofilm activity against S. aureus, with less observed development of bacterial resistance. Importantly, cinacalcet significantly improved survival in a pneumonia model and bacterial clearance in a biofilm infection model. Moreover, the antibacterial mechanism of cinacalcet mainly involves the destruction of membrane-targeted structures, alteration of energy metabolism, and production of reactive oxygen species (ROS). Cinacalcet was found to target IcaR, inhibiting biofilm formation through the negative regulation of IcaADBC.

CONCLUSIONS

The findings suggest that cinacalcet has potential for repurposing as a therapeutic agent for MDR S. aureus infections and associated biofilms, warranting further investigation.

Interdisciplinary-Inspired Smart Antibacterial Materials and Their Biomedical Applications

The discovery of antibiotics has saved millions of lives, but the emergence of antibiotic-resistant bacteria has become another problem in modern medicine. To avoid or reduce the overuse of antibiotics in antibacterial treatments, stimuli-responsive materials, pathogen-targeting nanoparticles, immunogenic nano-toxoids, and biomimetic materials are being developed to make sterilization better and smarter than conventional therapies. The common goal of smart antibacterial materials (SAMs) is to increase the antibiotic efficacy or function via an antibacterial mechanism different from that of antibiotics in order to increase the antibacterial and biological properties while reducing the risk of drug resistance. The research and development of SAMs are increasingly interdisciplinary because new designs require the knowledge of different fields and input/collaboration from scientists in different fields. A good understanding of energy conversion in materials, physiological characteristics in cells and bacteria, and bactericidal structures and components in nature are expected to promote the development of SAMs. In this review, the importance of multidisciplinary insights for SAMs is emphasized, and the latest advances in SAMs are categorized and discussed according to the pertinent disciplines including materials science, physiology, and biomimicry.

Electrospun L-Lysine/Amorphous Calcium Phosphate Loaded Core-Sheath Nanofibers for Managing Oral Biofilm Infections and Promoting Periodontal Tissue Repairment

Introduction

Periodontitis, a chronic inflammatory disease prevalent worldwide, is primarily treated through GTR for tissue regeneration. The efficacy of GTR, however, remains uncertain due to potential infections and the intricate microenvironment of periodontal tissue. Herein, We developed a novel core-shell structure multifunctional membrane using a dual-drug-loaded coaxial electrospinning technique (Lys/ACP-CNF), contains L-lysine in the outer layer to aid in controlling biofilms after GTR regenerative surgery, and ACP in the inner layer to enhance osteogenic performance for accelerating alveolar bone repair.

Methods

The biocompatibility and cell adhesion were evaluated through CCK-8 and fluorescence imaging, respectively. The antibacterial activity was assessed using a plate counting assay. ALP, ARS, and RT-qPCR were used to examine osteogenic differentiation. Additionally, an in vivo experiment was conducted on a rat model with acute periodontal defect and infection. Micro-CT and histological analysis were utilized to analyze the in vivo alveolar bone regeneration.

Results

Structural and physicochemical characterization confirmed the successful construction of the core-shell fibrous structure. Additionally, the Lys/ACP-CNF showed strong antibacterial coaggregation effects and induced osteogenic differentiation of PDLSCs in vitro. The in vivo experiment confirmed that Lys/ACP-CNF promotes new bone formation.

Conclusion

Lys/ACP-CNF rapidly exhibited excellent antibacterial activity, protected PDLSCs from infection, and was conducive to osteogenesis, demonstrating its potential application for clinical periodontal GTR surgery.

A Comparative Analysis of the Antibacterial Spectrum of Ultrasmall Manganese Ferrite Nanozymes with Varied Surface Modifications

Bacterial infectious diseases pose a significant global challenge. However, conventional antibacterial agents exhibit limited therapeutic effectiveness due to the emergence of drug resistance, necessitating the exploration of novel antibacterial strategies. Nanozymes have emerged as a highly promising alternative to antibiotics, owing to their particular catalytic activities against pathogens. Herein, we synthesized ultrasmall-sized MnFe2O4 nanozymes with different charges (MnFe2O4-COOH, MnFe2O4-PEG, MnFe2O4-NH2) and assessed their antibacterial capabilities. It was found that MnFe2O4 nanozymes exhibited both antibacterial and antibiofilm properties attributed to their excellent peroxidase-like activities and small sizes, enabling them to penetrate biofilms and interact with bacteria. Moreover, MnFe2O4 nanozymes effectively expedite wound healing within 12 days and facilitate tissue repair and regeneration while concurrently reducing inflammation. MnFe2O4-COOH displayed favorable antibacterial activity against Gram-positive bacteria, with 80% bacterial removal efficiency against MRSA by interacting with phosphatidylglycerol (PG) and cardiolipin (CL) of the membrane. By interacting with negatively charged bacteria surfaces, MnFe2O4-NH2 demonstrated the most significant and broad-spectrum antibacterial activity, with 95 and 85% removal efficiency against methicillin-resistant Staphylococcus aureus (MRSA) and P. aeruginosa, respectively. MnFe2O4-PEG dissipated membrane potential and reduced ATP levels in MRSA and P. aeruginosa, showing relatively broad-spectrum antibacterial activity. To conclude, MnFe2O4 nanozymes offer a promising therapeutic approach for treating wound infections.

Type I photodynamic antimicrobial therapy: Principles, progress, and future perspectives

The emergence of drug-resistant bacteria has significantly diminished the efficacy of existing antibiotics in the treatment of bacterial infections. Consequently, the need for finding a strategy capable of effectively combating bacterial infections has become increasingly urgent. Photodynamic therapy (PDT) is considered one of the most promising emerging antibacterial strategies due to its non-invasiveness, low adverse effect, and the fact that it does not lead to the development of drug resistance. However, bacteria at the infection sites often exist in the form of biofilm instead of the planktonic form, resulting in a hypoxic microenvironment. This phenomenon compromises the treatment outcome of oxygen-dependent type-II PDT. Compared to type-II PDT, type-I PDT is not constrained by the oxygen concentration in the infected tissues. Therefore, in the treatment of bacterial infections, type-I PDT exhibits significant advantages over type-II PDT. In this review, we first introduce the fundamental principles of type-I PDT in details, including its physicochemical properties and how it generates reactive oxygen species (ROS). Next, we explore several specific antimicrobial mechanisms utilized by type-I PDT and summarize the recent applications of type-I PDT in antimicrobial treatment. Finally, the limitations and future development directions of type-I photosensitizers are discussed. STATEMENT OF SIGNIFICANCE: The misuse and overuse of antibiotics have accelerated the development of bacterial resistance. To achieve the effective eradication of resistant bacteria, pathfinders have devised various treatment strategies. Among these strategies, type I photodynamic therapy has garnered considerable attention owing to its non-oxygen dependence. The utilization of non-oxygen-dependent photodynamic therapy not only enables the effective elimination of drug-resistant bacteria but also facilitates the successful eradication of hypoxic biofilms, which exhibits promising prospects for treating biofilm-associated infections. Based on the current research status, we anticipate that the novel type I photodynamic therapy agent can surmount the biofilm barrier, enabling efficient treatment of hypoxic biofilm infections.

Breaking CHIPS-Mediated immune evasion with tripterin to promote neutrophil chemotaxis against MRSA infection

Neutrophils are the most important innate immune cells in host defense against methicillin-resistant Staphylococcus aureus (MRSA). However, MRSA orchestrates precise and timely expression of a series of virulence factors, especially the chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS), to evade neutrophil-mediated host defenses. Here, we demonstrated that tripterin, a plant-derived bioactive pentacyclic triterpenoid, had a low minimum inhibitory concentration (MIC) of 1.28 µg/mL and displayed excellent anti-MRSA activity in vitro and in vivo. RNA-seq and further knockdown experiments revealed that tripterin could dramatically downregulate the expression of CHIPS by regulating the SaeRS two-component regulatory system, thereby enhancing the chemotactic response of neutrophils. Furthermore, tripterin also displayed a potential inhibitory effect on biofilm components to enhance neutrophil infiltration into the interior of the biofilm. In a mouse bacteremia model, tripterin could still maintain an excellent therapeutic effect that was significantly better than that of the traditional antibiotic vancomycin. Overall, these results suggest that tripterin possesses a superior antibacterial activity via breaking CHIPS-mediated immune evasion to promote neutrophil chemotaxis, thus providing a novel strategy for combating serious pathogenic infections.

Insights into the eradication of drug resistant Staphylococcus aureus via compound 6-nitrobenzo[cd]indole-2(1H)-ketone

6-Nitrobenzo[cd]indole-2(1H)-ketone (compound C2) exhibits an excellent germicidal effect against methicillin-resistant Staphylococcus aureus (MRSA). Mechanism studies show that C2 induces ROS over-production, cell membrane damage, and ATP and virulence factor down-regulation in bacteria. More importantly, C2 can inhibit biofilm formation and accelerate wound healing in a mouse infection model induced by MRSA.

A H2 S-Generated Supramolecular Photosensitizer for Enhanced Photodynamic Antibacterial Infection and Relieving Inflammation

Photodynamic therapy (PDT) is a promising treatment against bacteria-caused infections. By producing large amounts of reactive oxygen species (ROS), PDT can effectively eliminate pathogenic bacteria, without causing drug resistance. However, excessive ROS may also impose an oxidative stress on surrounding tissues, resulting in local inflammation. To avoid this major drawback and limit pro-inflammation during PDT, this work prepared a supramolecular photosensitizer (TPP-CN/CP5) based on host-guest interactions between a cysteine-responsive cyano-tetraphenylporphyrin (TPP-CN) and a water-soluble carboxylatopillar[5]arene (CP5). TPP-CN/CP5 not only possesses excellent photodynamic antibacterial properties, but also shows good anti-inflammatory and cell protection capabilities. Under 660 nm light irradiation, TPP-CN/CP5 could rapidly produce abundant ROS for sterilization. After the PDT process, the addition of cysteine (Cys) triggers the release of H2 S from TPP-CN. H2 S then stops the induced inflammation by inhibiting the production of related inflammatory factors. Both in vitro and in vivo experiments show the excellent antibacterial effects and anti-inflammatory abilities of TPP-CN/CP5. These results will certainly promote the clinical application of PDT in the treatment of bacterial infectious diseases.

Nanomaterials for Anti-Infection in Orthopedic Implants: A Review

Postoperative implant infection is a severe complication in orthopedic surgery, often leading to implant failure. Current treatment strategies mainly rely on systemic antibiotic therapies, despite contributing to increasing bacterial resistance. In recent years, nanomaterials have gained attention for their potential in anti-infection methods. They exhibit more substantial bactericidal effects and lower drug resistance than conventional antimicrobial agents. Nanomaterials also possess multiple bactericidal mechanisms, such as physico-mechanical interactions. Additionally, they can serve as carriers for localized antimicrobial delivery. This review explores recent applications of nanomaterials with different morphologies in post-orthopedic surgery infections and categorizes their bactericidal mechanisms.

Polysaccharide-Based Coating with Excellent Antibiofilm and Repeatable Antifouling-Bactericidal Properties for Treating Infected Hernia

In recent years, the utilization of medical devices has gradually increased and implantation procedures have become common treatments. However, patients are susceptible to the risk of implant infections. This study utilized chemical grafting to immobilize polyethylenimine (QPEI) and hyaluronic acid (HA) on the surface of the mesh to improve biocompatibility while being able to achieve antifouling antimicrobial effects. From the in vitro testing, PP-PDA-Q-HA exhibited a high antibacterial ratio of 93% against S. aureus, 93% against E. coli, and 85% against C. albicans. In addition, after five rounds of antimicrobial testing, the coating continued to exhibit excellent antimicrobial properties; PP-PDA-Q-HA also inhibits the formation of bacterial biofilms. In addition, PP-PDA-Q-HA has good hemocompatibility and cytocompatibility. In vivo studies in animal implantation infection models also demonstrated the excellent antimicrobial properties of PP-PDA-Q-HA. Our study provides a promising strategy for the development of antimicrobial surface medical materials with excellent biocompatibility.