Magnetic Composite Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Thermal Effects and Reactive Oxygen Species

Semiconductor photocatalytic antibacterial materials and their application for bone infection treatment

Bacterial infection in bone tissue engineering is a severe clinical issue. Traditional antimicrobial methods usually cause problems such as bacterial resistance and biosecurity. Employing semiconductor photocatalytic antibacterial materials is a more controlled and safer strategy, wherein semiconductor photocatalytic materials generate reactive oxygen species under illumination for killing bacteria by destroying their cell membranes, proteins, DNA, etc. In this review, P-type and N-type semiconductor photocatalytic materials and their antibacterial mechanisms are introduced. Type II heterojunctions, P-N heterojunctions, type Z heterojunctions and Schottky junctions have been reported to reduce the recombination of carriers, while element doping, sensitization and up-conversion luminescence expand the photoresponse range. Furthermore, the applications of semiconductor photocatalytic antibacterial materials in bone infection treatment such as osteomyelitis treatment, bone defect repair and dental tissue regeneration are summarized. Finally, the conclusion and future prospects of semiconductor photocatalytic antibacterial materials in bone tissue engineering were analyzed.

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.

Synergistic microwave hyperthermia treatment for subcutaneous deep in situ breast cancer using conformal array antennas and a microwave-thermal-sensitive nanomaterial

When microwave hyperthermia (MWH) array antenna technology is used to treat breast cancer, how to effectively target and heat deep tumors and reduce thermal damage to healthy tissues is still a challenge in clinical applications. In this study, the synergistic MWH effect of conformal-array antennas (CAA) and a novel microwave-thermal-sensitive nanomaterial (MTSN) was investigated for the treatment of subcutaneous deep in situ breast cancer. At the beginning of the study, the thermal damage score was used to evaluate the therapeutic efficacy of the CAA. It was found that although array antenna technology can achieve effective heating of deep tumors, its damage to healthy tissues is unacceptable. Consequently, we developed a novel MTSN, ZIF-8@HA, whose unique structure significantly enhanced the absorption of MW energy and MW thermal conversion efficiency in the local tumor region. The MW thermal conversion efficiency of ZIF-8@HA achieved was as high as 46.46% in in vivo MW heating experiments. In the phantom that simulates the electromagnetic environment of the human body, the microwave-thermal sensitization (MTS) effect is also significant, and the reduction in the average thermal damage score of healthy tissues by more than 10% was verified through measurements using the coaxial probe method and COMSOL simulations. Cellular experiments confirmed that the combination of ZIF-8@HA and MW irradiation could significantly reduce the survival rate of tumor cells. In addition, cross-tissue MW heating experiments revealed the advantages of ZIF-8@HA combined with the CAA. Finally, phantom experiments confirmed that the synergistic use of the CAA with ZIF-8@HA significantly accelerated the local heating rate of deep tumors, reduced the time required for the tumor region to achieve 100% thermal damage, and effectively minimized the thermal damage to healthy tissues.

Emodin Enhanced Microwave-Responsive Heterojunction with Powerful Bactericidal Capacity and Immunoregulation for Curing Bacteria-Infected Osteomyelitis

Eradication of osteomyelitis caused by bacterial infections is still a major challenge. Microwave therapy has the inherent advantage of deep penetration in curing deep tissue infections. However, the antibacterial efficiency of sensitizers is limited by the weak energy of microwaves. Here, a hybrid heterojunction system (Fe3O4/CuS/Emo) is designed for curing bacterially infected osteomyelitis. As an enhanced microwave sensitizer, it shows supernormal microwave response ability. Specifically, Fe3O4 acts as a matrix to mediate magnetic loss. After CuS loading, the heterogeneous interface forms induce significant interfacial polarization, which increasing dielectric loss. On the basis of the heterojunction formed by the two semiconductors, emodin is innovatively introduced to modify it. This integration not only accelerates the movement of charge carriers but also enhances polarization loss due to the numerous functional groups present on the surface. This further optimizes the microwave thermal and catalytic response. In addition, the unique anti-inflammatory properties of emodin confer the ability of hybrid heterojunction to regulate the immune microenvironment. In vivo studies reveal that heterojunction modified by emodin programmed elimination of bacteria and regulation of the immune microenvironment. It offers a revolutionary approach to the treatment of bacterial osteomyelitis.

A Bacterial Capturing, Neural Network-Like Carbon Nanotubes/Prussian Blue/Puerarin Nanocomposite for Microwave Treatment of Staphylococcus Aureus-Infected Osteomyelitis

Staphylococcus aureus (S. aureus)-infected osteomyelitis is a deep tissue infection that cannot be effectively treated with antibiotics. Microwave (MW) thermal therapy (MTT) and MW dynamic therapy (MDT) based on MW-responsive materials are promising for the therapy of bacteria-infected osteomyelitis occurring in deep tissues that cannot be effectively treated with antibiotics. In this work, the MW-responsive system of carbon nanotubes (CNTs)/Prussian blue (PB)/puerarin (Pue) with stable network-like structures is constructed. The PB is grown in situ on the CNTs, and its introduction not only reduces the aggregation of the network-like structures of the CNTs, but the large specific surface area and mesoporous structure can also provide many active sites for the adsorption of oxygen and polar molecules. Pue is a natural anti-inflammatory material that reduces inflammation at the infection site. The composite of the CNTs and PB avoids the skin effect and thus can improve dielectric and reflection losses. The MW thermal response of CNTs/PB/Pue is mainly due to the occurrence of reflection loss, dielectric loss, multiple reflections and scattering, interface polarization, and dipole polarization. In addition, under MW irradiation, the CNTs/PB/Pue can produce reactive oxygen species (ROS), such as singlet oxygen (1O2), hydroxyl radical (·OH).

Interface/Dipole Polarized Antibiotics-Loaded Fe3O4/PB Nanoparticles for Non-Invasive Therapy of Osteomyelitis Under Medical Microwave Irradiation

Due to their poor light penetration, photothermal therapy and photodynamic therapy are ineffective in treating deep tissue infections, such as osteomyelitis caused by Staphylococcus aureus (S. aureus). Here, a microwave (MW)-responsive magnetic targeting composite system consisting of ferric oxide (Fe3O4)/Prussian blue (PB) nanoparticles, gentamicin (Gent), and biodegradable poly(lactic-co-glycolic acid) (PLGA) is reported. The PLGA/Fe3O4/PB/Gent complex is used in combination with MW thermal therapy (MTT), MW dynamic therapy (MDT), and chemotherapy (CT) to treat acute osteomyelitis infected with S. aureus-infected. The powerful antibacterial effect of the PLGA/Fe3O4/PB/Gent is determined by the synergistic effects of heat and reactive oxygen species (ROS) generation by the Fe3O4/PB nanoparticles under MW irradiation and the effective release of Gent at the infection site via magnetic targeting. The antibacterial mechanism of the PLGA/Fe3O4/PB/Gent under MW irradiation is analyzed using bacterial transcriptome RNA sequencing. The MW heat and ROS reduce the activity of the protein transporters on the bacterial membrane, along with the transport of various ions and the acceleration of phosphate metabolism, which can lead to increased permeability of the bacterial membrane, damage the ribosome and DNA, and accompany the internal protein efflux of the bacteria, thus effectively killing the bacteria.

Oxygen vacancy formation strengthened microwave catalysis of Zn-Zr solid solution for antibiotic-free therapy strategies of bacteria-infected osteomyelitis

Osteomyelitis, a grave deep tissue infection primarily caused by Staphylococcus aureus, results in serious complications such as abscesses and sepsis. With the incidence from open fractures exceeding 30 % and prevalent antibiotic resistance due to extensive treatment regimens, there's an urgent need for innovative, antibiotic-free strategies. Photothermal therapy (PTT) and photodynamic therapy (PDT) renowned for generating localized reactive oxygen species (ROS), face limitations in penetration depth. To overcome this, our method combines the deep penetration attributes of medical microwaves (MW) with the synergistic effects of the ZnO/ZrO2 solid solution. Comprehensive in vitro and in vivo evaluations showcased the solid-solution's potent antibacterial efficacy and biocompatibility. The ZnO/ZrO2 solid solution, especially in a 7:3 M ratio, manifests superior microstructural characteristics, optimizing MW-assisted therapy. Our findings highlight the potential of this integrated strategy as a promising avenue in osteomyelitis management.

Electron Aggregation and Oxygen Fixation Reinforced Microwave Dynamic and Thermal Therapy for Effective Treatment of MRSA-Induced Osteomyelitis

Antibiotics are frequently used to clinically treat osteomyelitis caused by bacterial infections. However, extended antibiotic use may result in drug resistance, which can be life threatening. Here, a heterojunction comprising Fe2O3/Fe3S4 magnetic composite is constructed to achieve short-term and efficient treat osteomyelitis caused by methicillin-resistant Staphylococcus aureus (MRSA). The Fe2O3/Fe3S4 composite exhibits powerful microwave (MW) absorption properties, thereby effectively converting incident electromagnetic energy into thermal energy. Density functional theory calculations demonstrate that Fe2O3/Fe3S4 possesses significant charge accumulation and oxygen-fixing capacity at the heterogeneous interface, which provides more active sites and oxygen sources for trapping electromagnetic hotspots. The finite element analysis indicates that Fe2O3/Fe3S4 displays a larger electromagnetism field enhancement parameter than Fe2O3 owing to a significant increase in electromagnetic hotspots. These hotspots contribute to charge differential accumulation and depletion motions at the interface, thereby augmenting the release of free electrons that subsequently combine with the oxygen adsorbed by Fe2O3/Fe3S4 to generate reactive oxygen species (ROS) and heat. This research, which achieves extraordinary bacterial eradication through the synergistic effect of microwave thermal therapy (MWTT) and microwave dynamic therapy (MDT), presents a novel strategy for treating deep-tissue bacterial infections.

A Smart Bacteria-Capture-Killing Vector for Effectively Treating Osteomyelitis Through Synergy Under Microwave Therapy

Osteomyelitis caused by deep tissue infections is difficult to cure through phototherapy due to the poor penetration depth of the light. Herein, Cu/C/Fe3O4-COOH nanorod composites (Cu/C/Fe3O4-COOH) with nanoscale tip convex structures are successfully fabricated as a microwave-responsive smart bacteria-capture-killing vector. Cu/C/Fe3O4-COOH exhibited excellent magnetic targeting and bacteria-capturing ability due to its magnetism and high selectivity affinity to the amino groups on the surface of Staphylococcus aureus (S. aureus). Under microwave irradiation, Cu/C/Fe3O4-COOH efficiently treated S. aureus-infected osteomyelitis through the synergistic effects of microwave thermal therapy, microwave dynamic therapy, and copper ion therapy. It is calculated the electric field intensity in various regions of Cu/C/Fe3O4-COOH under microwave irradiation, demonstrating that it obtained the highest electric field intensity on the surface of copper nanoparticles of Cu/C/Fe3O4-COOH due to its high-curvature tips and metallic properties. This led to copper nanoparticles attracted more charged particles compared with other areas in Cu/C/Fe3O4-COOH. These charges are easier to escape from the high curvature surface of Cu/C/Fe3O4-COOH, and captured by adsorbed oxygen, resulting in the generation of reactive oxygen species. The Cu/C/Fe3O4-COOH designed in this study is expected to provide insight into the treatment of deep tissue infections under the irradiation of microwave.

Injectable Nano-Micro Composites with Anti-bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

The effective management of osteomyelitis remains extremely challenging due to the difficulty associated with treating bone defects, the high probability of recurrence, the requirement of secondary surgery or multiple surgeries, and the difficulty in eradicating infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Hence, smart biodegradable biomaterials that provide effective and precise local anti-infection effects and can promote the repair of bone defects are actively being developed. Here, a novel nano-micro composite is fabricated by combining calcium phosphate (CaP) nanosheets with drug-loaded GelMA microspheres via microfluidic technology. The microspheres are covalently linked with vancomycin (Van) through an oligonucleotide (oligo) linker using an EDC/NHS carboxyl activator. Accordingly, a smart nano-micro composite called "CaP@MS-Oligo-Van" is synthesized. The porous CaP@MS-Oligo-Van composites can target and capture bacteria. They can also release Van in response to the presence of bacterial micrococcal nuclease and Ca2+, exerting additional antibacterial effects and inhibiting the inflammatory response. Finally, the released CaP nanosheets can promote bone tissue repair. Overall, the findings show that a rapid, targeted drug release system based on CaP@MS-Oligo-Van can effectively target bone tissue infections. Hence, this agent holds potential in the clinical treatment of osteomyelitis caused by MRSA.

Magnetic Bimetallic Heterointerface Nanomissiles with Enhanced Microwave Absorption for Microwave Thermal/Dynamics Therapy of Breast Cancer

Microwave thermotherapy (MWT) has shown great potential in cancer treatment due to its deep tissue penetration and minimally invasive nature. However, the poor microwave absorption (MA) properties of the microwave thermal sensitizer in the medical frequency band significantly limit the thermal effect of MWT and then weaken the therapeutic efficacy. In this paper, a Ni-based multilayer heterointerface nanomissile of MOFs-Ni-Ru@COFs (MNRC) with improved MA performance in the desired frequency band via introducing magnetic loss and dielectric loss is developed for MWT-based treatment. The loading of the Ni nanoparticle in MNRC mediates the magnetic loss, introducing the MA in the medical frequency band. The heterointerface formed in the MNRC by nanoengineering induces significant interfacial polarization, increasing the dielectric loss and then enhancing the generated MA performance. Moreover, MNRC with the strong MA performance in the desired frequency range not only enhances the MW thermal effect of MWT but also facilitates the electron and energy transfer, generating reactive oxygen species (ROS) at tumor sites to mediate microwave dynamic therapy (MDT). The strategy of strengthening the MA performance of the sensitizer in the medical frequency band to improve MWT-MDT provides a direction for expanding the clinical application of MWT in tumor treatment.

Nanotherapeutic System with Effective Microwave Sensitization and Pyroptosis Programming Enable Synergistic Microwave-Immunotherapy in Bladder Cancer

Currently, the prognosis for patients with advanced bladder cancer remains poor, with only a minority being sensitive to immune checkpoint inhibitors. There is a need to develop additional treatment strategies. Microwave therapy, as a promising approach for some inoperable tumors, still faces challenges such as limited efficacy and high recurrence rates. Additionally, the cell damage and necrosis induced by conventional microwave treatment only act as weak immunostimulatory factors for antitumor immunity, failing to activate effective antitumor immune responses. Recent discoveries have shown that inducing pyroptosis can provide a good opportunity for enhancing systemic immune responses and alleviating immune suppression in cancer therapy. Here, we have developed Mn-ZrMOF@DAC, a microwave-sensitized nanoparticle loaded with the DNA methylation inhibitor decitabine. The Mn-ZrMOF@DAC can enhance the effect of microwave thermal therapy and generate reactive oxygen species under microwave irradiation, causing thermal and oxidative damage to cancer cells. Furthermore, there was an important up-regulation of the key pyroptosis protein GSDME, with a marked increase in pyroptotic cell numbers. In vivo experiments demonstrated that mice injected with Mn-ZrMOF@DAC nanoparticles followed by microwave radiation treatment exhibited potent antitumor effects and enhanced the efficacy of anti-PD-1 therapy. This therapy not only enhanced the efficacy of microwave treatment, exhibiting significant antitumor effects, but also activated antitumor immunity by inducing pyroptosis, thus enhancing the efficacy of immunotherapy for bladder cancer. It holds promise for providing new avenues in the treatment of bladder cancer.

Rapid and effective treatment of chronic osteomyelitis by conductive network-like MoS2/CNTs through multiple reflection and scattering enhanced synergistic therapy

Staphylococcus aureus (S. aureus)-infected chronic osteomyelitis (COM) is one of the most devastating infectious diseases with a high recurrence rate, often leading to amputation and even death. It is incurable by all the current strategies involving the clinical use of radical debridement and systemic intravenous antibiotics. Here, we reported on a microwave (MW)-assisted therapy for COM by constructing a heterojunction formed by flake nanoflower-shaped molybdenum disulfide (MoS2) and tubular carbon nanotubes (CNTs). This composite could achieve a combination of MW thermal therapy (MTT) and MW dynamic therapy (MDT) to accurately and rapidly treat COM with deep tissue infection. In vitro and in vivo experiments showed that MoS2/CNTs were effective in non-invasively treating S. aureus-induced COM due to the heat and reactive oxygen species (ROS) produced under MW irradiation. The mechanism of heat and ROS generation was explained by MW network vector analysis, density of states (DOS), oxygen adsorption energy, differential charge and finite element (FEM) under MW irradiation. Since the Fermi layer was mainly contributed by the Mo-4d and C-2P orbitals, MoS2/CNTs could store a large amount of charge and easily release more electrons. In addition, charge accumulation and dissipation motion were strong on the surface of and inside MoS2/CNTs because of electromagnetic hot spots, resulting in the spilling out of a great deal of high-energy electrons. Due to the low oxygen adsorption energy of MoS2/CNTs-O2, these high-energy electrons combined further with the adsorbed oxygen to produce ROS.

Interfacial and Defect Polarization Enhanced Microwave Noninvasive Therapy for Staphylococcus aureus-Infected Chronic Osteomyelitis

Chronic osteomyelitis (COM), is a long-term, constant, and intractable disease mostly induced by infection from the invasion of Staphylococcus aureus (S. aureus) into bone cells. Here, we describe a highly effective microwave (MW) therapeutic strategy for S. aureus-induced COM based on the in situ growth of interfacial oxygen vacancy-rich molybdenum disulfide (MoS2)/titanium carbide (Ti3C2Tx) MXene with oxygen-deficient titanium dioxide (TiO2-x) on Ti3C2Tx (labeled as HU-MoS2/Ti3C2Tx) by producing reactive oxygen species (ROS) and heat. HU-MoS2/Ti3C2Tx produced heat and ROS, which could effectively treat S. aureus-induced COM under MW irradiation. The underlying mechanism determined by density functional theory (DFT) and MW vector network analysis was that HU-MoS2/Ti3C2Tx formed a high-energy local electric field under MW irradiation, consequently generating more high-energy free electrons to pass and move across the interface at a high speed and accelerate by the heterointerface, which enhanced the charge accumulation on both sides of the interface. Moreover, these charges were captured by the oxygen species adsorbed at the HU-MoS2/Ti3C2Tx interface to produce ROS. MoS2 facilitated multiple reflections and scattering of electromagnetic waves as well as enhanced impedance matching. Ti3C2Tx enhanced the conduction loss of electromagnetic waves, while functional groups induced dipole polarization to enhance attenuation of MW.

Microwave-Excited, Antibacterial Core-Shell BaSO4/BaTi5O11@PPy Heterostructures for Rapid Treatment of S. aureus-Infected Osteomyelitis

Owing to its deep penetration capability, microwave (MW) therapy has emerged as a promising method to eradicate deep-seated acute bone infection diseases such as osteomyelitis. However, the MW thermal effect still needs to be enhanced to achieve rapid and efficient treatment of deep focal infected areas. In this work, the multi-interfacial core-shell structure barium sulfate/barium polytitanates@polypyrrole (BaSO₄/BaTi₅O₁₁@PPy) was prepared, which exhibited enhanced MW thermal response via the well-designed multi-interfacial structure. To be specific, BaSO₄/BaTi₅O₁₁@PPy achieved rapid temperature increases in a short period and efficient clearance of Staphylococcus aureus (S. aureus) infections under MW irradiation. After 15 min MW irradiation, the antibacterial efficacy of BaSO₄/BaTi₅O₁₁@PPy can reach up to 99.61 ± 0.22%. Their desirable thermal production capabilities originated from enhanced dielectric loss including multiple interfacial polarization and conductivity loss. Additionally, in vitro analysis illuminated that the underlying antimicrobial mechanism was attributed to the noticeable MW thermal effect and changes in energy metabolic pathways on bacterial membrane instigated by BaSO₄/BaTi₅O₁₁@PPy under MW irradiation. Considering remarkable antibacterial efficiency and acceptable biosafety, we envision that it has significant value in broadening the pool of desirable candidates to fight against S. aureus-infected osteomyelitis. STATEMENT OF SIGNIFICANCE: : The treatment of deep bacterial infection remains challenging due to the ineffectiveness of antibiotic treatment and the susceptibility to bacterial resistance. Microwave (MW) thermal therapy (MTT) is a promising approach with remarkable penetration to centrally heat up the infected area. This study proposes to utilize the core-shell structure BaSO₄/BaTi₅O₁₁@PPy as an MW absorber to achieve localized heating under MW radiation for MTT. In vitro experiments demonstrated that the disrupted bacterial membrane is primarily due to the localized high temperature and interrupted electron transfer chain. As a consequence, its antibacterial rate is as high as 99.61% under MW irradiation. It is shown that the BaSO₄/BaTi₅O₁₁@PPy is a promising candidate for eliminating bacterial infection in deep-seated tissues.

CuCeO Bimetallic Oxide Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Microwave Catalysis and Fenton-Therapy

Osteomyelitis caused by bacteria is a deep-seated lesion and is often treated clinically with antibiotics. Long-term use of antibiotics may predispose bacteria to develop resistance. Here, CuCeO_x material is applied to treat infectious bacterial osteomyelitis using microwave (MW)-assisted bacterial killing. Heat generation occurs as a result of the dielectric properties of the material under MW irradiation, and the material generates reactive oxygen species (ROS) under MW irradiation. Heat and ROS increase the thermal sensitivity and permeability of bacterial cell membranes, and the released copper ions easily penetrate the bacterial membrane and react with H₂ O₂ to produce a toxic hydroxyl group inside the bacteria, leading to the bacteria's eventual death. This is due to the synergistic effect of the MW thermal effect, ROS, and the breaking of the equilibrium within the bacteria. CuCeO_x can effectively treat osteomyelitis caused by Staphylococcus aureus using MW irradiation. This study can safely and effectively address the challenge of deep tissue infections by shedding light on non-invasive antimicrobial systems and using MW thermal therapy and MW dynamics to achieve therapeutic results.