Ultrasound-responsive catalytic microbubbles enhance biofilm elimination and immune activation to treat chronic lung infections

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.

Antibacterial carbon dots

Bacterial infections significantly threaten human health, leading to severe diseases and complications across multiple systems and organs. Antibiotics remain the primary treatment strategy for these infections. However, the growing resistance of bacteria to conventional antibiotics underscores the urgent need for safe and effective alternative treatments. In response, several approaches have been developed, including carbon dots (CDs), antimicrobial peptides, and antimicrobial polymers, all of which have proven effective in combating bacterial resistance. Among these, CDs stand out due to their unique advantages, including low preparation cost, stable physicochemical properties, high biocompatibility, tunable surface chemistry, strong photoluminescence, and efficient generation of reactive oxygen species. These features make CDs highly promising in antibacterial applications. This review explores the development of antibacterial CDs, focusing on their mechanisms of action-physical destroy, biochemical damage, and synergistic effects-while highlighting their potential for clinical use as antibacterial agents.

Ultrasound-Triggered Oxygen Release System for Accelerating Wound Healing of Diabetic Foot Ulcers

Diabetic foot ulcer (DFU) is a common complication of chronic diabetes mellitus. Oxygen plays a critical role in the healing process of DFU wounds by promoting cell migration and neovascularization. However, clinical hyperbaric oxygen (HBO) therapy predominantly uses systemic oxygen administration, posing challenges in inadequate DFU local oxygen penetration and potential ectopic organs oxygen toxicity. To address these challenges, a strategy to encapsulate oxygen with lipid microbubbles (OMBs) and incorporate them into a body temperature-sensitive heparin-pluronic copolymer hydrogel (HP/OMBs) have been developed. HP/OMBs showed high biocompatibility both in vitro and in vivo. After in situ administration, oxygen can be released from HP/OMBs to the local deep site of the DFU wounds under ultrasound (US) triggering. Thus, given its biocompatibility and practicality, the combined action of HP/OMBs and the US has important translational value in accelerating diabetic chronic wound healing.

Biofilm Microenvironment-Sensitive Anti-Virulent and Immunomodulatory Nano-on-Nanodroplets to Combat Refractory Biofilm Infection Through Toxin Neutralization and Phagocytosis

Biofilm-associated wound infection is principally perceived as the bacterial defense mechanism that hinders antibiotic penetration, causes toxin impairment, and suppresses the immunological responses of the host immune system. Several antibiofilm agents have been developed, but the least of these agents can simultaneously cornerstone on the biofilm-associated immunosuppression and bacterial toxin-induced cellular dysfunction. Inspired by the fusogenic property of nanodroplets and immunomodulatory functions of metal nanoparticles, biofilm targeted anti-virulent immunomodulatory cationic nanoparticle shelled nanodroplets (C-AgND) is fabricated to completely disintegrate and eradicate the Staphylococcus aureus (S. aureus) biofilm. The specific binding of C-AgND neutralizes the negatively charged EPS layer, causing their destabilization followed by penetration of the nanoformulation into the biofilm matrix, killing the persister cells. Consequently, C-AgND eliminates the virulence property of the S. aureus biofilm through α-hemolysin neutralization. C-AgND promotes a strong immunomodulatory effect by polarizing macrophages into their M1 phenotype to induce phagocytosis of the disintegrated biofilm-released residual cells, rejuvenating the host's innate immune responses for the complete eradication of the biofilm. Moreover, the ex vivo skin wound infection model illustrates an excellent biofilm eradication efficacy of C-AgND in comparison to the commercial ones, rendering them to be a promising replacement of existing antibiofilm agents in clinical application.

Hybrid Cell Membrane-Engineered Nanocarrier for Triple-Action Strategy to Address Pseudomonas aeruginosa Infection

Bacterial infections resistant to antimicrobial treatments, particularly those caused by Pseudomonas aeruginosa (P. aeruginosa), frequently lead to elevated mortality rates. Tackling this resistance using therapeutic combinations with varied mechanisms has shown considerable promise. In this study, a bioinspired nanocarrier is successfully designed and engineered for targeted antibiotic delivery and toxin/bacteria clearance. This is achieved by encapsulating antibiotic-loaded framework nucleic acids with hybrid cell membranes acquired from neutrophils and platelets. By coating the hybrid membrane outside the shell, nanocarriers are endowed with the function of neutrophil-like chemotaxis and platelet-like bacteria adhesion to achieve the first stage of inflammation targeting. Based on the specific binding of bacteria toxin to the hybrid membrane, the release of antibiotic-loaded framework nucleic acids is triggered by toxin-mediated membrane lysis to fulfill the second stage of toxin neutralization and bacteria killing. Meanwhile, the immunomodulation potential of framework nucleic acids enables nanocarriers to accomplish the third stage of reversing the immunosuppressive microenvironment. In mouse models of acute and chronic P. aeruginosa pneumonia, the nanocarriers can reduce bacterial burden at a low dosage and decrease mortality with negligible toxicity. In sum, these findings have illustrated the remarkable capability of nanocarriers in treating recalcitrant bacterial infections.

Nanomaterial-based synergistic strategies for combating dental caries: progress and perspectives

Dental caries, as the predominant global oral disease, remains a critical public health issue worldwide, particularly in socioeconomically disadvantaged communities. However, common caries prevention approaches (e.g., oral health education, mechanical plaque removal, and delivery of fluoride agents) are still insufficient for optimal caries management, and therefore, alternative regimens that can supplement existing strategies are highly warranted. Nanomaterials exhibit considerable potential in combating cariogenic pathogens and biofilms owing to their promising antimicrobial capacity, improved penetration into biofilms, targeted precision delivery, and versatile physicochemical properties. As unifunctional materials are limited in caries management, this review underscores the latest advancement in multifunctional anti-caries nanomaterials/nanomedicines. It highlights the cutting-edge materials developed or engineered to (i) incorporate diagnostic capabilities to prevent caries at an early stage, thus enhancing treatment efficiency, (ii) integrate mechanical "brushing" with anti-caries approaches to mechanochemically eradicate biofilms, (iii) exert antimicrobial/antibiofilm effects while preserving dental hard tissue. The current work also outlines future directions for optimizing nanosystems in the management of dental caries while emphasizing the need for innovative solutions to improve preventive and therapeutic efficacies.

Advancing Anti-Biofilm Strategies: Innovations to Combat Biofilm-Related Challenges and Enhance Efficacy

Biofilms are complex communities of microorganisms that can cause significant challenges in various settings, including industrial processes, environmental systems, and human health. The protective nature of biofilms makes them resistant to traditional anti-biofilm strategies, such as chemical agents, mechanical interventions, and surface modifications. To address the limitations of conventional anti-biofilm methods, researchers have explored emerging strategies that encompass the use of natural compounds, nanotechnology-based methods, quorum-sensing inhibition, enzymatic degradation, and antimicrobial photodynamic/sonodynamic therapy. There is an increasing focus on combining multiple anti-biofilm strategies to combat resistance and enhance effectiveness. Researchers are continuously investigating the mechanisms of biofilm formation and developing innovative approaches to overcome the limitations of conventional anti-biofilm methods. These efforts aim to improve the management of biofilms and prevent infections while preserving the environment. This study provides a comprehensive overview of the latest advancements in anti-biofilm strategies. Given the dynamic nature of this field, exploring new approaches is essential to stimulate further research and development initiatives. The effective management of biofilms is crucial for maintaining the health of industrial processes, environmental systems, and human populations.

Recent advances in reactive oxygen species (ROS)-responsive drug delivery systems for photodynamic therapy of cancer

Reactive oxygen species (ROS)-responsive drug delivery systems (DDSs) have garnered significant attention in cancer research because of their potential for precise spatiotemporal drug release tailored to high ROS levels within tumors. Despite the challenges posed by ROS distribution heterogeneity and endogenous supply constraints, this review highlights the strategic alliance of ROS-responsive DDSs with photodynamic therapy (PDT), enabling selective drug delivery and leveraging PDT-induced ROS for enhanced therapeutic efficacy. This review delves into the biological importance of ROS in cancer progression and treatment. We elucidate in detail the operational mechanisms of ROS-responsive linkers, including thioether, thioketal, selenide, diselencide, telluride and aryl boronic acids/esters, as well as the latest developments in ROS-responsive nanomedicines that integrate with PDT strategies. These insights are intended to inspire the design of innovative ROS-responsive nanocarriers for enhanced cancer PDT.

Magnetic Field/Ultrasound-Responsive Fe3O4 Microbubbles for Targeted Mechanical/Catalytic Removal of Bacterial Biofilms

Conventional antibiotics are limited by drug resistance, poor penetration, and inadequate targeting in the treatment of bacterial biofilm-associated infections. Microbubble-based ultrasound (US)-responsive drug delivery systems can disrupt biofilm structures and enhance antibiotic penetration through cavitation effects. However, currently developed US-responsive microbubbles still depend on antibiotics and lack targeting capability. In this work, magnetic field/ultrasound (MF/US)-responsive Fe3O4 microbubbles (FMB) were constructed based on Fe3O4 nanoparticles (NPs) with superparamagnetic and peroxidase-like catalytic properties. In vitro experiments demonstrated that FMB can be targeted to methicillin-resistant Staphylococcus aureus (MRSA) biofilms by the direction of MF. Upon US irradiation, FMB collapse due to inertial cavitation and generate mechanical forces to disrupt the structure of MRSA biofilms and releases Fe3O4 NPs, which catalyze the generation of reactive oxygen species (ROS) from H2O2 in the biofilm microenvironment and kill the bacteria within the biofilm. In a mouse biofilm infection model, FMB efficiently destroyed MRSA biofilms grown in subcutaneous catheters with the MF and US. Magnetic-targeted mechanical/catalytic therapy based on FMB provides a promising strategy for effectively combating bacterial biofilm infection.

Isovanillin decreases the virulence regulated by the quorum sensing system of Pseudomonas aeruginosa

The quorum-sensing (QS) system of Pseudomonas aeruginosa dominates the pathogenicity of the acute or chronic infection process. Hence, curbing the pathogenicity of P. aeruginosa by targeting QS system is an ideal strategy. This study aims to identify potential anti-virulence compounds that can effectively disrupt the QS system of P. aeruginosa using a combination of virtual screening and experimental validation techniques. We explored inhibitory effect of isovanillin obtained by virtual screening on P. aeruginosa QS regulated virulence factors extracellular protease, biofilm, and pyocyanin. Results displayed that isovanillin could inhibit the virulence phenotypes regulated by the las- and pqs-QS systems of P. aeruginosa. The synthesis of extracellular proteases, pyocyanin, and biofilm formation by P. aeruginosa were dramatically inhibited by sub-MICs doses of isovanillin. The results of RNA sequencing and quantitative PCR revealed that the QS-activated genes down-regulated by subinhibitory isovanillin in the transcriptional evels. Furthermore, the presence of isovanillin increased the susceptibility of drug-resistant P. aeruginosa to kanamycin, meropenem, and polymyxin B. Treatment of isovanillin as a monotherapy significantly decreased the mortality of C. elegans in P. aeruginosa PAO1 or UCBPP-PA14 (PA14) infection. Our study reported the anti-virulence activity of isovanillin against P. aeruginosa, and provided a structural foundation for developing anti-virulence drugs targeting the QS system of P. aeruginosa.

Ultrasound-Mediated Antibiotic Delivery to In Vivo Biofilm Infections: A Review

Bacterial biofilms are a significant concern in various medical contexts due to their resilience to our immune system as well as antibiotic therapy. Biofilms often require surgical removal and frequently lead to recurrent or chronic infections. Therefore, there is an urgent need for improved strategies to treat biofilm infections. Ultrasound-mediated drug delivery is a technique that combines ultrasound application, often with the administration of acoustically-active agents, to enhance drug delivery to specific target tissues or cells within the body. This method involves using ultrasound waves to assist in the transportation or activation of medications, improving their penetration, distribution, and efficacy at the desired site. The advantages of ultrasound-mediated drug delivery include targeted and localized delivery, reduced systemic side effects, and improved efficacy of the drug at lower doses. This review scrutinizes recent advances in the application of ultrasound-mediated drug delivery for treating biofilm infections, focusing on in vivo studies. We examine the strengths and limitations of this technology in the context of wound infections, device-associated infections, lung infections and abscesses, and discuss current gaps in knowledge and clinical translation considerations.

Nanozyme-Shelled Microcapsules for Targeting Biofilm Infections in Confined Spaces

Bacterial infections in irregular and branched confinements pose significant therapeutic challenges. Despite their high antimicrobial efficacy, enzyme-mimicking nanoparticles (nanozymes) face difficulties in achieving localized catalysis at distant infection sites within confined spaces. Incorporating nanozymes into microrobots enables the delivery of catalytic agents to hard-to-reach areas, but poor nanoparticle dispersibility and distribution during fabrication hinder their catalytic performance. To address these challenges, a nanozyme-shelled microrobotic platform is introduced using magnetic microcapsules with collective and adaptive mobility for automated navigation and localized catalysis within complex confinements. Using double emulsions produced from microfluidics as templates, iron oxide and silica nanoparticles are assembled into 100-µm microcapsules, which self-organize into multi-unit, millimeter-size assemblies under rotating magnetic fields. These microcapsules exhibit high peroxidase-like activity, efficiently catalyzing hydrogen peroxide to generate reactive oxygen species (ROS). Notably, microcapsule assemblies display remarkable collective navigation within arched and branched confinements, reaching the targeted apical regions of the tooth canal with high accuracy. Furthermore, these nanozyme-shelled microrobots perform rapid catalysis in situ and effectively kill biofilms on contact via ROS generation, enabling localized antibiofilm action. This study demonstrates a facile method of integrating nanozymes onto a versatile microrobotic platform to address current needs for targeted therapeutic catalysis in complex and confined microenvironments.

Magnetic silk fibroin nanospheres loaded with amphiphilic polypeptides and antibiotics for biofilm eradication

The eradication of established biofilms is a highly challenging task, due to the protective barrier effect of extracellular polymeric substances (EPS) and the presence of persister cells. Both increased drug permeability and elimination of persister cells are essential for the eradication of biofilms. Here, magnetic silk fibroin nanospheres loaded with antibiotics and host defense peptide (HDP) mimics (MPSN/S@P) were developed to demonstrate a new strategy for biofilm eradication. As an HDP mimic, an amphiphilic polypeptide containing 90% L-lysine and 10% L-valine (Lys90Val10) was selected for loading onto magnetic silk fibroin nanospheres via electrostatic interactions. Lys90Val10 exhibited excellent antibacterial activities against both planktonic and persister cells of Staphylococcus aureus (S. aureus). As a representative of the hydrophobic drug, spiramycin (SPM) was conveniently embedded into the β-sheet domain during the self-assembly process of silk fibroin. The sustained release of SPM during biofilm eradication enhanced the antibacterial efficacy of MPSN/S@P. The antibacterial test demonstrated that the extract from the MPSN/S@P suspension can kill both planktonic and persister cells of S. aureus, as well as inhibiting biofilm formation. Importantly, with the assistance of magnetic guidance and photothermal effects derived from Fe3O4 nanoparticles (Fe3O4 NPs), over 92% of bacteria in the biofilm were killed by MPSN/S@P, indicating the successful eradication of mature biofilms. The simple preparation method, integration of photothermal and magnetic responsiveness, and persister cell killing functions of MPSN/S@P provide an accessible strategy and illustrative paradigm for efficient biofilm eradication.

Customized A-D-A type molecule to construct a nitric oxide nanogenerator with enhanced antibacterial activity for infected wound healing

Bacterial infections pose an increasingly serious threat to global health due to the development of drug-resistant strains. Developing a method to efficiently kill bacteria and promote tissue repair is imperative to decrease the damage from bacterial infection, especially infected wounds. Herein, a biofriendly and light-controlled nitric oxide (NO) generator HFB with simultaneous bacterial killing and wound repair properties is reported based on a tailored light-responsive molecule F(EIBC)2. HFB demonstrates an appropriate photothermal conversion efficiency of 33.4% and type I reactive oxygen species (˙OH and H2O2) generation capability to simultaneously trigger NO generation and potently kill bacteria. Furthermore, HFB can effectively eradicate mature bacterial biofilms with the aid of favorable permeability of NO. Additionally, HFB effectively eradicates Staphylococcus aureus in infected wounds of living mice and accelerates healing via NO-induced angiogenesis and collagen deposition. Owing to the encapsulated human serum albumin (HSA), heavy metal-free feature, and synergistic killing mechanism, HFB exhibits good biosafety to surrounding tissue and major organs. This work provides a novel dual-functional photo-responsive molecule and a potential light-controlled release platform for the treatment of bacterial infections.

Dual tobramycin and docosahexaenoic acid loaded nanoemulsions combating Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa (P. aeruginosa) typically forms biofilms in vivo, which exhibit high resistance and complicate eradication efforts. Additionally, persistent inflammation and excessive oxidative stress can lead to severe lung dysfunction, facilitating bacterial colonization and infection. Herein, we prepared oil-in-water (O/W) nanoemulsions (TD-αT NEs) by using PEG5k-block-PCL5k and α-tocopherol to encapsulate tobramycin (TOB). To enhance TOB's drug load, a hydrophobic ion pair (TDIP) composed of TOB and docosahexaenoic acid (DHA) was pre-prepared. TD-αT NEs was not only easily prepared and aerosolized, but stable in both physics and chemistry. The negatively charged TD-αT NEs facilitated penetration through mucus, reaching infection sites. Subsequently, TD-αT NEs permeated biofilms due to their small size and released drugs via lipase-triggered carrier dissociation, aiding in eradicating internal bacteria within biofilms (with a 16-fold reduction in CFU vs. free TOB group). TD-αT NEs simultaneously exerted superior anti-inflammatory effects, reducing levels of pro-inflammatory cytokines (NO, IL-6, IL-8, and TNF-α) while increasing the level of anti-inflammatory cytokine (IL-10). It was achieved through the upregulation of PPAR-γ and downregulation of NF-κB signaling, thus mitigating the lung damage. In addition, TD-αT NEs demonstrated strong antioxidant activity, alleviating the oxidative stress induced by P. aeruginosa. Notably, when administered via inhalation, TD-αT NEs significantly reduced the lung bacterial burden, lung inflammation, and oxidative stress in vivo compared to TOB solution. TD-αT NEs could prove beneficial in treating chronic pulmonary infections induced by P. aeruginosa through a comprehensive strategy, specifically enhancing biofilm eradication, reducing inflammation, and alleviating oxidative stress.

Portable SERS biosensor based on aptamer-assisted catalytic hairpin assembly signal amplification for ultrasensitive detection of Staphylococcus aureus

Bacteria infections pose a serious threat to public health, and it is urgent to develop facile and accurate detection methods. To meet the important need, a potable and high-sensitive surface enhanced Raman scattering (SERS) biosensor based on aptamer recognition and catalytic hairpin assembly (CHA) signal amplification was proposed for point-of-care detection of Staphylococcus aureus (S. aureus). The SERS biosensor contains three parts: recognition probes, SERS sensing chip, and SERS tags. The feasibility of the strategy was verified by gel electrophoresis, and the one-step test route was optimized. The bacteria SERS biosensor has a good linear relationship ranging from 10 to 107 CFU mL-1 with high sensitivity low to 5 CFU mL-1, and shows excellent specificity, uniformity, and repeatability on S. aureus identification and enumeration, which can distinguish S. aureus from other bacteria. The SERS biosensor shows a good recovery rate (95.73 %-109.65 %) for testing S. aureus spiked in milk, and has good practicability for detecting S. aureus infected mouse wound, which provides a facile and reliable approach for detection of trace bacteria in the real samples.

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.

Sonodynamic effect based on vancomycin-loaded microbubbles or meropenem-loaded microbubbles enhances elimination of different biofilms and bactericidal efficacy

Aims

This study investigated vancomycin-microbubbles (Vm-MBs) and meropenem (Mp)-MBs with ultrasound-targeted microbubble destruction (UTMD) to disrupt biofilms and improve bactericidal efficiency, providing a new and promising strategy for the treatment of device-related infections (DRIs).

Methods

A film hydration method was used to prepare Vm-MBs and Mp-MBs and examine their characterization. Biofilms of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli were treated with different groups. Biofilm biomass differences were determined by staining. Thickness and bacterial viability were observed with confocal laser scanning microscope (CLSM). Colony counts were determined by plate-counting. Scanning electron microscopy (SEM) observed bacterial morphology.

Results

The Vm-MBs and Mp-MBs met the experimental requirements. The biofilm biomass in the Vm, Vm-MBs, UTMD, and Vm-MBs + UTMD groups was significantly lower than in the control group. MRSA and E. coli biofilms were most notably damaged in the Vm-MBs + UTMD group and Mp-MBs + UTMD group, respectively, with mean 21.55% (SD 0.08) and 19.73% (SD 1.25) remaining in the biofilm biomass. Vm-MBs + UTMD significantly reduced biofilm thickness and bacterial viability (p = 0.005 and p < 0.0001, respectively). Mp-MBs + UTMD could significantly decrease biofilm thickness and bacterial viability (allp < 0.001). Plate-counting method showed that the numbers of MRSA and E. coli bacterial colonies were significantly lower in the Vm-MBs + UTMD group and the Mp, Mp-MBs, UTMD, Mp-MBs + UTMD groups compared to the control group (p = 0.031). SEM showed that the morphology and structure of MRSA and E. coli were significantly damaged in the Vm-MBs + UTMD and Mp-MBs + UTMD groups.

Conclusion

Vm-MBs or Mp-MBs combined with UTMD can effectively disrupt biofilms and protectively release antibiotics under ultrasound mediation, significantly reducing bacterial viability and improving the bactericidal effect of antibiotics.

Engineered Probiotic Bio-Heterojunction with Robust Antibiofilm Modality via "Eating" Extracellular Polymeric Substances for Wound Regeneration

The compact three-dimensional (3D) structure of extracellular polymeric substances (EPS) within biofilms significantly hinders the penetration of antimicrobial agents, making biofilm eradication challenging and resulting in persistent biofilm-associated infections. To address this challenge, a solution is proposed: a probiotic bio-heterojunction (P-bioHJ) combining Lactobacillus rhamnosus with MXene (Ti3C2) quantum dots (MQDs)/FeS heterojunction. This innovation aims to break down the saccharides in EPS, enabling effective combat against biofilm-associated infections. Initially, the P-bioHJ targets saccharides through metabolic processes, causing the collapse of EPS and allowing infiltration into bacterial colonies. Simultaneously, upon exposure to near-infrared (NIR) irradiation, the P-bioHJ produces reactive oxygen species (ROS) and thermal energy, deploying physical mechanisms to combat bacterial biofilms effectively. Following antibiofilm treatment, the P-bioHJ adjusts the oxidative environment, reduces wound inflammation by scavenging ROS, boosts antioxidant enzyme activity, and mitigates the NF-κB inflammatory pathway, thereby accelerating wound healing. In vitro and in vivo experiments confirm the exceptional antibiofilm, antioxidant/anti-inflammatory, and wound-regeneration properties of P-bioHJ. In conclusion, this study provides a promising approach for treating biofilm-related infections.

[Classification and Application of Ultrasound-Responsive Nanomaterials in Anti-Inflammatory Therapy]

Ultrasound, a high-frequency mechanical wave with excellent tissue penetration, has been widely applied in medical diagnostic imaging. Furthermore, it has been reported that ultrasound has broad prospects for extensive applications in the field of disease treatment in recent years due to its non-invasiveness and high efficiency. Ultrasound-responsive nanomaterials have the unique advantages of a small size and a high reactivity. Such materials have the capability for precision control of drug release under ultrasound stimulation, which provides a new approach to enhancing the efficiency of drug therapy. Therefore, these materials have attracted the attention of a wide range of scholars. Inflammation is a defensive response produced by organisms to deal with injuries. However, excessive inflammatory response may lead to various tissue damages in organisms and even endanger patients' lives. Many studies have demonstrated that limiting the inflammatory response using ultrasound-responsive nanomaterials is a viable way of treating diseases. Currently, there are still challenges in the application of ultrasound-responsive nanomaterials in anti-inflammatory therapy. The design and synthesis process of nanomaterials is complicated, and further verification of the biocompatibility and safety of these materials is needed. Therefore, in this review, we summarized and classified common ultrasound-responsive nanomaterials in the field of anti-inflammation and systematically introduced the properties of different nanomaterials. In addition, the anti-inflammatory applications of ultrasound-responsive nanomaterials in various diseases, such as bone diseases, skin and muscle diseases, autoimmune diseases, and respiratory diseases, are also described in detail. It is expected that this review will provide insights for further research and clinical applications in the realms of precision treatment, targeted drug delivery, and clinical trial validation of ultrasound-responsive nanomaterials used in anti-inflammatory therapies.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Ultrasound-responsive gallium protoporphyrin and oxygen loaded perfluoropentane nanodroplets for effective sonodynamic therapy of implant infections

Implant infections are severe complications in clinical treatment, which often accompany the formation of bacterial biofilms with high antibiotic resistance. Sonodynamic therapy (SDT) is an antibiotic-free method that can generate reactive oxygen species (ROS) to kill bacteria under ultrasound (US) treatment. However, the extracellular polymeric substances (EPS) barrier of bacterial biofilms and the hypoxic microenvironment significantly limit the antibiofilm activity of SDT. In this study, lipid-shelled perfluoropentane (PFP) nanodroplets loaded with gallium protoporphyrin IX (GaPPIX) and oxygen (O2) (LPGO NDs) were developed for the treatment of implant infections. Under US stimulation, LPGO NDs undergo the cavitation effect and disrupt the biofilm structure like bombs due to liquid-gas phase transition. Meanwhile, the LPGO NDs release O2 and GaPPIX upon US stimulation. The released O2 can alleviate the hypoxic microenvironment in the biofilm and enhance the ROS formation by GaPPIX for enhanced bacterial killing. In vivo experimental results demonstrate that the LPGO NDs can efficiently treat implant infections of methicillin-resistant Staphylococcus aureus (MRSA) in a mouse model by disrupting the biofilm structure, alleviating hypoxia, and enhancing bacterial killing by SDT. Therefore, this work provides a new multifunctional sonosensitizer to overcome the limitations of SDT for treating implant infections.

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.

Dry powder inhalation containing muco-inert ciprofloxacin and colistin co-loaded liposomes for pulmonary P. Aeruginosa biofilm eradication

Pseudomonas aeruginosa (PA), a predominant pathogen in lung infections, poses significant challenges due to its biofilm formation, which is the primary cause of chronic and recalcitrant pulmonary infections. Bacteria within these biofilms exhibit heightened resistance to antibiotics compared to their planktonic counterparts, and their secreted toxins exacerbate lung infections. Diverging from traditional antibacterial therapy for biofilm eradication, this study introduces a novel dry powder inhalation containing muco-inert ciprofloxacin and colistin co-encapsulated liposomes (Cipro-Col-Lips) prepared using ultrasonic spray freeze drying (USFD) technique. This USFD dry powder is designed to efficiently deliver muco-inert Cipro-Col-Lips to the lungs. Once deposited, the liposomes rapidly diffuse into the airway mucus, reaching the biofilm sites. The muco-inert Cipro-Col-Lips neutralize the biofilm-secreted toxins and simultaneously trigger the release of their therapeutic payload, exerting a synergistic antibiofilm effect. Our results demonstrated that the optimal USFD liposomal dry powder formulation exhibited satisfactory in vitro aerosol performance in terms of fine particle fraction (FPF) of 44.44 ± 0.78 %, mass median aerodynamic diameter (MMAD) of 4.27 ± 0.21 μm, and emitted dose (ED) of 99.31 ± 3.31 %. The muco-inert Cipro-Col-Lips effectively penetrate the airway mucus and accumulate at the biofilm site, neutralizing toxins and safeguarding lung cells. The triggered release of ciprofloxacin and colistin works synergistically to reduce the biofilm's antibiotic resistance, impede the development of antibiotic resistance, and eliminate 99.99 % of biofilm-embedded bacteria, including persister bacteria. Using a PA-beads induced biofilm-associated lung infection mouse model, the in vivo efficacy of this liposomal dry powder aerosol was tested, and the results demonstrated that this liposomal dry powder aerosol achieved a 99.7 % reduction in bacterial colonization, and significantly mitigated inflammation and pulmonary fibrosis. The USFD dry powder inhalation containing muco-inert Cipro-Col-Lips emerges as a promising therapeutic strategy for treating PA biofilm-associated lung infections.

Reactive Microneedle Patches with Antibacterial and Dead Bacteria-Trapping Abilities for Skin Infection Treatment

Bacterial skin infections are highly prevalent and pose a significant public health threat. Current strategies are primarily focused on the inhibition of bacterial activation while disregarding the excessive inflammation induced by dead bacteria remaining in the body and the effect of the acidic microenvironment during therapy. In this study, a novel dual-functional MgB2 microparticles integrated microneedle (MgB2 MN) patch is presented to kill bacteria and eliminate dead bacteria for skin infection management. The MgB2 microparticles not only can produce a local alkaline microenvironment to promote the proliferation and migration of fibroblasts and keratinocytes, but also achieve >5 log bacterial inactivation. Besides, the MgB2 microparticles effectively mitigate dead bacteria-induced inflammation through interaction with lipopolysaccharide (LPS). With the incorporation of these MgB2 microparticles, the resultant MgB2 MN patches effectively kill bacteria and capture dead bacteria, thereby mitigating these bacteria-induced inflammation. Therefore, the MgB2 MN patches show good therapeutic efficacy in managing animal bacterial skin infections, including abscesses and wounds. These results indicate that reactive metal borides-integrated microneedle patches hold great promise for the treatment of clinical skin infections.

Customized Lanthanide Nanobiohybrids for Noninvasive Precise Phototheranostics of Pulmonary Biofilm Infection

A noninvasive strategy for in situ diagnosis and precise treatment of bacterial biofilm infections is highly anticipated but still a great challenge. Currently, no in vivo biofilm-targeted theranostic agent is available. Herein, we fabricated intelligent theranostic alginate lyase (Aly)-NaNdF4 nanohybrids with a 220 nm sunflower-like structure (NaNdF4@DMS-Aly) through an enrichment-encapsulating strategy, which exhibited excellent photothermal conversion efficiency and the second near-infrared (NIR-II) luminescence. Benefiting from the site-specific targeting and biofilm-responsive Aly release from NaNdF4@DMS-Aly, we not only enabled noninvasive diagnosis but also realized Aly-photothermal synergistic therapy and real-time evaluation of therapeutic effect in mice models with Pseudomonas aeruginosa biofilm-induced pulmonary infection. Furthermore, such nanobiohybrids with a sheddable siliceous shell are capable of delaying the NaNdF4 dissolution and biodegradation upon accomplishing the therapy, which is highly beneficial for the biosafety of theranostic agents.

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.

Chemical multiscale robotics for bacterial biofilm treatment

A biofilm constitutes a bacterial community encased in a sticky matrix of extracellular polymeric substances. These intricate microbial communities adhere to various host surfaces such as hard and soft tissues as well as indwelling medical devices. These microbial aggregates form a robust matrix of extracellular polymeric substances (EPSs), leading to the majority of human infections. Such infections tend to exhibit high resistance to treatment, often progressing into chronic states. The matrix of EPS protects bacteria from a hostile environment and prevents the penetration of antibacterial agents. Modern robots at nano, micro, and millimeter scales are highly attractive candidates for biomedical applications due to their diverse functionalities, such as navigating in confined spaces and targeted multitasking. In this tutorial review, we describe key milestones in the strategies developed for the removal and eradication of biofilms using robots of different sizes and shapes. It can be seen that robots at different scales are useful and effective tools for treating bacterial biofilms, thus preventing persistent infections, the loss of costly implanted medical devices, and additional costs associated with hospitalization and therapies.

Ultrasound-Stimulated "Exocytosis" by Cell-Like Microbubbles Enhances Antibacterial Species Penetration and Immune Activation Against Implant Infection

Host immune systems serving as crucial defense lines are vital resisting mechanisms against biofilm-associated implant infections. Nevertheless, biofilms hinder the penetration of anti-bacterial species, inhibit phagocytosis of immune cells, and frustrate host inflammatory responses, ultimately resulting in the weakness of the host immune system for biofilm elimination. Herein, a cell-like construct is developed through encapsulation of erythrocyte membrane fragments on the surface of Fe3 O4 nanoparticle-fabricated microbubbles and then loaded with hydroxyurea (EMB-Hu). Under ultrasound (US) stimulation, EMB-Hu undergoes a stable oscillation manner to act in an "exocytosis" mechanism for disrupting biofilm, releasing agents, and enhancing penetration of catalytically generated anti-bacterial species within biofilms. Additionally, the US-stimulated "exocytosis" by EMB-Hu can activate pro-inflammatory macrophage polarization and enhance macrophage phagocytosis for clearance of disrupted biofilms. Collectively, this work has exhibited cell-like microbubbles with US-stimulated "exocytosis" mechanisms to overcome the biofilm barrier and signal macrophages for inflammatory activation, finally achieving favorable therapeutic effects against implant infections caused by methicillin-resistant Staphylococcus aureus (MRSA) biofilms.

Neutrophil Function Conversion Driven by Immune Switchpoint Regulator against Diabetes-Related Biofilm Infections

Reinforced biofilm structures and dysfunctional neutrophils induced by excessive oxidative stress contribute to the refractoriness of diabetes-related biofilm infections (DRBIs). Herein, in contrast to traditional antibacterial therapies, an immune switchpoint-driven neutrophil immune function conversion strategy based on a deoxyribonuclease I loaded vanadium carbide MXene (DNase-I@V2 C) nanoregulator is proposed to treat DRBIs via biofilm lysis and redirecting neutrophil functions from NETosis to phagocytosis in diabetes. Owing to its intrinsic superoxide dismutase/catalase-like activities, DNase-I@V2 C effectively scavenges reactive oxygen species (ROS) in a high oxidative stress microenvironment to maintain the biological activity of DNase-I. By increasing the depth of biofilm penetration of DNase-I, DNase-I@V2 C thoroughly degrades extracellular DNA and neutrophil extracellular traps (NETs) in extracellular polymeric substances, thus breaking the physical barrier of biofilms. More importantly, as an immune switchpoint regulator, DNase-I@V2 C can skew neutrophil functions from NETosis toward phagocytosis by intercepting ROS-NE/MPO-PAD4 and activating ROS-PI3K-AKT-mTOR pathways in diabetic microenvironment, thereby eliminating biofilm infections. Biofilm lysis and synergistic neutrophil function conversion exert favorable therapeutic effects on biofilm infections in vitro and in vivo. This study serves as a proof-of-principle demonstration of effectively achieving DRBIs with high therapeutic efficacy by regulating immune switchpoint to reverse neutrophil functions.

Stimuli-Actuated Turn-On Theranostic Nanoplatforms for Imaging-Guided Antibacterial Treatment

Antibacterial theranostic nanoplatforms, which integrate diagnostic and therapeutic properties, exhibit gigantic application prospects in precision medicine. However, traditional theranostic nanoplatforms usually present an always-on signal output, which leads to poor specificity or selectivity in the treatment of bacterial infections. To address this challenge, stimuli-actuated turn-on nanoplatforms are developed for simultaneous activation of diagnostic signals (e.g., fluorescent, photoacoustic, magnetic signals) and initiation of antibacterial treatment. Specifically, by combining the infection microenvironment-responsive activation of visual signals and antibacterial activity, these theranostic nanoplatforms exert both higher accurate diagnosis rates and more effective treatment effects. In this review, the imaging and treatment strategies that are commonly used in the clinic are first briefly introduced. Next, the recent progress of stimuli-actuated turn-on theranostic nanoplatforms for treating bacterial infectious diseases is summarized in detail. Finally, current bottlenecks and future opportunities of antibacterial theranostic nanoplatforms are also outlined and discussed.

Nanotechnology-Based Drug Delivery Systems to Control Bacterial-Biofilm-Associated Lung Infections

Airway mucus dysfunction and impaired immunological defenses are hallmarks of several lung diseases, including asthma, cystic fibrosis, and chronic obstructive pulmonary diseases, and are mostly causative factors in bacterial-biofilm-associated respiratory tract infections. Bacteria residing within the biofilm architecture pose a complex challenge in clinical settings due to their increased tolerance to currently available antibiotics and host immune responses, resulting in chronic infections with high recalcitrance and high rates of morbidity and mortality. To address these unmet clinical needs, potential anti-biofilm therapeutic strategies are being developed to effectively control bacterial biofilm. This review focuses on recent advances in the development and application of nanoparticulate drug delivery systems for the treatment of biofilm-associated respiratory tract infections, especially addressing the respiratory barriers of concern for biofilm accessibility and the various types of nanoparticles used to combat biofilms. Understanding the obstacles facing pulmonary drug delivery to bacterial biofilms and nanoparticle-based approaches to combatting biofilm may encourage researchers to explore promising treatment modalities for bacterial-biofilm-associated chronic lung infections.

An Immunomodulatory Biomimetic Single-Atomic Nanozyme for Biofilm Wound Healing Management

Nanozyme-driven catalytic antibacterial therapy has become a promising modality for bacterial biofilm infections. However, current catalytic therapy of biofilm wounds is severely limited by insufficient catalytic efficiency, excessive inflammation, and deep tissue infection. Drawing from the homing mechanism of natural macrophages, herein, a hollow mesoporous biomimetic single-atomic nanozyme (SAN) is fabricated to actively target inflamed parts, suppress inflammatory factors, and eliminate deeply organized bacteria for enhance biofilm eradication. In the formulation, this biomimetic nanozyme (Co@SAHSs@IL-4@RCM) consists of IL-4-loaded cobalt SANs-embedded hollow sphere encapsulate by RAW 264.7 cell membrane (RCM). Upon accumulation at the infected sites through the specific receptors of RCM, Co@SAHS catalyze the conversion of hydrogen peroxide into hydroxyl radicals and are further amplify by NIR-II photothermal effect and glutathione depletion to permeate and destroy biofilm structure. This behavior subsequently causes the dissociation of RCM shell and the ensuing release of IL-4 that can reprogram macrophages, enabling suppression of oxidative injury and tissue inflammation. The work paves the way to engineer alternative "all-in-one" SANs with an immunomodulatory ability and offers novel insights into the design of bioinspired materials.

Environment-Responsive Therapeutic Platforms for the Treatment of Implant Infection

The application of medical implants has greatly improved the survival rate and life quality of patients. Nevertheless, in recent years, there are increasing cases of implant dysfunction or failure because of bacterial infections. Despite significant improvements in biomedicine, there are still serious challenges in the treatment of implant-related infections. With the formation of bacterial biofilms and the development of bacterial resistance, these limitations lead to a low efficacy of conventional antibiotics. To address these challenges, it is urgent to exploit innovative treatment strategies for implant-related infections. Based on these ideas, environment-responsive therapeutic platforms with high selectivity, low drug resistance, and minor dose-limiting toxicity have attracted widespread attention. By using exogenous/endogenous stimuli, the antibacterial activity of therapeutics can be activated on demand and exhibit remarkable therapeutic effects. Exogenous stimuli include photo, magnetism, microwave, and ultrasound. Endogenous stimuli mainly include the pathological characteristics of bacterial infections such as acidic pH, anomalous temperature, and abnormal enzymatic activities. In this review, the recent progress of environment-responsive therapeutic platforms with spatiotemporally controlled drug release/activation is systematically summarized. Afterward, the limitations and opportunities of these emerging platforms are highlighted. Finally, it is hoped that this review will offer novel ideas and techniques to combat implant-related infections.

Nanotherapeutics with immunoregulatory functions for the treatment of bacterial infection

The advent of drug-resistant pathogens results in the occurrence of stubborn bacterial infections that cannot be treated with traditional antibiotics. Antibacterial immunotherapy by reviving or activating the body's immune system to eliminate pathogenic bacteria has confirmed promising therapeutic strategies in controlling bacterial infections. Subsequent studies found that antimicrobial immunotherapy has its own benefits and limitations, such as avoiding recurrence of infection and autoimmunity-induced side effects. Current studies indicate that the various antibacterial therapeutic strategies inducing immune regulation can achieve superior therapeutic efficacy compared with monotherapy alone. Therefore, summarizing the recent advances in nanomedicine with immunomodulatory functions for combating bacterial infections is necessary. Herein, we briefly introduce the crisis caused by drug-resistant bacteria and the opportunity for antibacterial immunotherapy. Then, immune-involved multimodal antibacterial therapy for the treatment of infectious diseases was systematically summarized. Finally, the prospects and challenges of immune-involved combinational therapy are discussed.