High-Efficiency Near-Infrared Light Responsive Antibacterial System for Synergistic Ablation of Bacteria and Biofilm

Ti3C2/CuWO4/Pt nanozyme: photothermal-enhanced chemodynamic antibacterial effects induced by NIR

With the growing issue of antibiotic resistance, it has become increasingly crucial to develop highly efficient antimicrobial materials. While the single-component nanozyme systems exhibited some catalytic activity, their efficiency remains suboptimal. This study presents a Ti3C2/CuWO4/Pt hybrid nanozyme composed of photothermal agents and nanozymes, which leverages the photothermal effect to enhance nanozyme activity and achieve efficient antimicrobial effects. The composite material exhibited peroxidase (POD)-like catalytic activity, effectively converting hydrogen peroxide (H2O2) into hydroxyl radicals (·OH). Meanwhile, the Ti3C2/CuWO4/Pt material demonstrated high photothermal conversion ability, which not only promoted the generation of ·OH under near-infrared (NIR) light irradiation, but also facilitated copper (Cu2+) ions release from the CuWO4 nanozyme, thereby further augmenting its catalytic activity. After 4 to 5 min of light irradiation, the Ti3C2/CuWO4/Pt nanozyme exhibited significant antimicrobial performance against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In summary, this work presents a Ti3C2/CuWO4/Pt nanoplatform that utilizes the photothermal effect to enhance the chemodynamic antimicrobial activity, showcasing its potential applications in antibiotic-free antimicrobial fields.

Peroxidase-like copper-doped carbon-dots embedded in hydrogels for stimuli-responsive bacterial biofilm elimination and wound healing

Bacterial biofilms and their microenvironment are significant challenges that must be faced in the design of antibacterial drugs. Microenvironment-responsive mimetic peroxidases (POD) have been demonstrated to be an efficient solution to eliminating bacterial biofilms. However, they inevitably require additional H2O2 and/or acid due to the poor permeabilities towards biofilms. Herein, we report POD-like copper-doped carbon dots (named CuCD1) synthesized through a facile microwave-assisted carbonization manner. The characteristics of ultrasmall size (< 5 nm) and positive charge enabled it to possess good penetrability toward bacterial biofilm. As expected, CuCD1 showed great damage to bacteria due to the generation of hydroxyl radicals (•OH), which originated from the catalytic decomposition of endogenous H2O2 under a weak acid bacterial biofilm microenvironment. This highly increased oxidative stress resulted in the alteration of cell membrane permeability, subsequent cell death, and the final eradication of bacterial biofilm and the exposed bacteria. Moreover, to verify the practicality in vivo, CuCD1 was introduced to a routine hydrogel that was crosslinked by carboxymethyl chitosan (CMCS) and oxidized dextran (ODEX). In comparison with the control groups, the composite hydrogel, i.e., CuCD1-CMCS-ODEX revealed better antibacterial performance and thus accelerated wound healing and collagen disposition. This work would open opportunities to design CDs-based biofilm microenvironment-responsive antibacterial nanoagents. STATEMENT OF SIGNIFICANCE: (1) Ultrasmall size, positively charged, peroxidase (POD)-like CuCD1 were designed and harvested by a facile microwave-assisted carbonization method. (2) CuCD1 revealed a competitive in vitro antibacterial performance, good penetrability, and microenvironment-responsive clearing capacity towards bacterial biofilm. (3) By composing with CMCS-ODEX hydrogel, the composite hydrogel could continuously eliminate bacteria, promote wound healing, as well as collagen disposition. (4) This work would provide a new strategy in the design of CDs-based biofilm microenvironment-responsive antibacterial nano-agents.

Synergetic antibacterial nanosheet based on Ti3C2Tx photothermal therapy and cationic polymer to eradicate drug-resistant bacterial biofilms

Drug-resistant bacteria infection and biofilm formation on the wound still pose a tremendous challenge in post-antibiotic era. It has been proposed that multimode synergetic antibacterial strategies may be employed to eradicate drug-resistant bacteria and biofilms effectively. In this study, we synthesized non-invasive antibacterial two-dimension (2D) composite nanosheet BPG using Ti3C2Tx MXene and cationic borneol-guanidine based polymers (B-PGMA-Gu) via simple electrostatically co-assemble. BPG can target bacteria and efficiently eliminate Gram-positive bacteria Staphylococcus aureus (S. aureus), Gram-negative bacteria Escherichia coli (E. coli), and methicillin-resistant Staphylococcus aureus (MRSA) under 808 nm radiation. By combining the photothermal properties of Ti3C2Tx MXene and the excellent membrane penetration ability of B-PGMA-Gu, MRSA biofilms can be effectively removed at 100 μg mL-1 under laser irradiation, resulting in a bactericidal efficiency of 99.1%. This method offers a more effective and rapid non-antibiotic method for removing biofilms.

High-frequency ultrasound modulation of Zn2+ release from nanoclay supported ZnO antibacterial composites

Bacterial infections pose considerable health risks, emphasising the critical need for effective and biocompatible antibacterial drugs. Considerably, we developed an efficient antimicrobial system incorporating the combined potential of high-frequency ultrasound and antimicrobial drugs against bacterial infections. A ZnO-kaolinite (Kaol) composite with antibacterial properties was synthesised by growing ZnO on the Kaol nano-clay surface using the co-precipitation method. High-frequency ultrasound efficiently promotes the release of Zn2+, which enhances the antibacterial properties. Furthermore, in-depth in vitro antibacterial studies and bacterial live/dead staining experiments validate the exceptionally high antibacterial performance of the composite. Therefore, owing to the synergistic effects of high-frequency ultrasound and antibacterial properties, the as-prepared novel antibacterial composite is a promising potential substitute for conventional antibacterial agents.

Dual pH- and ATP-Responsive Antibacterial Nanospray: On-Demand Release of Antibacterial Factors, Imaging Monitoring, and Accelerated Healing of Bacteria-Infected Wounds under NIR Activation

The prevalence of pathogenic bacterial infections with high morbidity and mortality poses a widespread challenge to the healthcare system. Therefore, it is imperative to develop nanoformulations capable of adaptively releasing antimicrobial factors and demonstrating multimodal synergistic antimicrobial activity. Herein, an NIR-activated multifunctional synergistic antimicrobial nanospray MXene/ZIF-90@ICG was prepared by incorporating ZIF-90@ICG nanoparticles onto MXene-NH2 nanosheets. MXene/ZIF-90@ICG can on-demand release the antimicrobial factors MXenes, ICG, and Zn2+ in response to variations in pH and ATP levels within the bacterial infection microenvironment. Under NIR radiation, the combination of MXenes, Zn2+, and ICG generated a significant amount of ROS and elevated heat, thereby enhancing the antimicrobial efficacy of PDT and PTT. Meanwhile, NIR excitation could accelerate the further release of ICG and Zn2+, realizing the multimodal synergistic antibacterial effect of PDT/PTT/Zn2+. Notably, introducing MXenes improved the dispersion of the synthesized antimicrobial nanoparticles in aqueous solution, rendering MXene/ZIF-90@ICG a candidate for application as a nanospray. Importantly, MXene/ZIF-90@ICG demonstrated antimicrobial activity and accelerated wound healing in the constructed in vivo subcutaneous Staphylococcus aureus infection model with NIR activation, maintaining a favorable biosafety level. Therefore, MXene/ZIF-90@ICG holds promise as an innovative nanospray for adaptive multimodal synergistic and efficient antibacterial applications with NIR activation.

Research Progress on Ti3C2Tx-Based Composite Materials in Antibacterial Field

The integration of two-dimensional Ti3C2Tx nanosheets and other materials offers broader application options in the antibacterial field. Ti3C2Tx-based composites demonstrate synergistic physical, chemical, and photodynamic antibacterial activity. In this review, we aim to explore the potential of Ti3C2Tx-based composites in the fabrication of an antibiotic-free antibacterial agent with a focus on their systematic classification, manufacturing technology, and application potential. We investigate various components of Ti3C2Tx-based composites, such as metals, metal oxides, metal sulfides, organic frameworks, photosensitizers, etc. We also summarize the fabrication techniques used for preparing Ti3C2Tx-based composites, including solution mixing, chemical synthesis, layer-by-layer self-assembly, electrostatic assembly, and three-dimensional (3D) printing. The most recent developments in antibacterial application are also thoroughly discussed, with special attention to the medical, water treatment, food preservation, flexible textile, and industrial sectors. Ultimately, the future directions and opportunities are delineated, underscoring the focus of further research, such as elucidating microscopic mechanisms, achieving a balance between biocompatibility and antibacterial efficiency, and investigating effective, eco-friendly synthesis techniques combined with intelligent technology. A survey of the literature provides a comprehensive overview of the state-of-the-art developments in Ti3C2Tx-based composites and their potential applications in various fields. This comprehensive review covers the variety, preparation methods, and applications of Ti3C2Tx-based composites, drawing upon a total of 171 English-language references. Notably, 155 of these references are from the past five years, indicating significant recent progress and interest in this research area.

NF-κB-Signaling-Targeted Immunomodulatory Nanoparticle with Photothermal and Quorum-Sensing Inhibition Effects for Efficient Healing of Biofilm-Infected Wounds

The development of therapeutics with high antimicrobial activity and immunomodulatory effects is urgently needed for the treatment of infected wounds due to the increasing danger posed by recalcitrant-infected wounds. In this study, we developed light-controlled antibacterial, photothermal, and immunomodulatory biomimetic N/hPDA@M nanoparticles (NPs). This nanoplatform was developed by loading flavonoid naringenin onto hollow mesoporous polydopamine NPs in a π-π-stacked configuration and encasing them with macrophage membranes. First, our N/hPDA@M NPs efficiently neutralized inflammatory factors present within the wound microenvironment by the integration of macrophage membranes. Afterward, the N/hPDA@M NPs effectively dismantled bacterial biofilms through a combination of the photothermal properties of PDA and the quorum sensing inhibitory effects of naringenin. It is worth noting that N/hPDA@M NPs near-infrared-enhanced release of naringenin exhibited specificity toward the NF-κB-signaling pathway, effectively mitigating the inflammatory response. This innovative design not only conferred remarkable antibacterial properties upon the N/hPDA@M NPs but also endowed them with the capacity to modulate inflammatory responses, curbing excessive inflammation and steering macrophage polarization toward the M2 phenotype. As a result, this multifaceted approach significantly contributes to expediting the healing process of infected skin wounds.

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

Metal-amplified sonodynamic therapy of Ti-based chitosan-polyvinyl alcohol hybrid hydrogel dressing against subcutaneous Staphylococcus aureus infection

Ultrasound (US)-mediated sonodynamic therapy (SDT) has received extensive attention in pathogen elimination for non-invasiveness and high spatial and temporal accuracy. Considering that hydrogel can provide a healing-friendly environment for wounds, in this work, hybrid hydrogels are constructed by embedding Ag doped TiO2 nanoparticles in chitosan-polyvinyl alcohol hydrogels for enhanced sonodynamic antibacterial therapy. With metal silver doped, TiO2 nanoparticles sonosensitivity is improved to generate more reactive oxygen species (ROS), which endows hybrid hydrogels with high-efficient antibacterial properties. In vivo results show that hybrid hydrogel dressing can prevent infection and promote wound closure within 2 days. The healing ratio excess 95 % with no pus produced at the end of treatment. The therapeutic mechanism was identified that heterojunction formed in Ag doped TiO2 facilitates the separation of charge carriers under US irradiation, leading to elevating ROS generation. The generated ROS promote hybrid hydrogels sonodynamic antibacterial therapeutic efficacy to thoroughly eliminate pathogen via disrupting bacterial cell membrane integrity, decreasing membrane fluidity and increasing membrane permeability. Besides, biofilm formation could be effectively inhibited. This work developed a hybrid hydrogel with amplified SDT effect for wound healing, which is expected to provide inspiration of hybrid hydrogels design and Ti-based nanomaterials sonosensitivity enhancement.

MXene-based Membranes for Drinking Water Production

The soaring development of industry exacerbates the shortage of fresh water, making drinking water production an urgent demand. Membrane techniques feature the merits of high efficiency, low energy consumption, and easy operation, deemed as the most potential technology to purify water. Recently, a new type of two-dimensional materials, MXenes as the transition metal carbides or nitrides in the shape of nanosheets, have attracted enormous interest in water purification due to their extraordinary properties such as adjustable hydrophilicity, easy processibility, antifouling resistance, mechanical strength, and light-to-heat transformation capability. In pioneering studies, MXene-based membranes have been evaluated in the past decade for drinking water production including the separation of bacteria, dyes, salts, and heavy metals. This review focuses on the recent advancement of MXene-based membranes for drinking water production. A brief introduction of MXenes is given first, followed by descriptions of their unique properties. Then, the preparation methods of MXene membranes are summarized. The various applications of MXene membranes in water treatment and the corresponding separation mechanisms are discussed in detail. Finally, the challenges and prospects of MXene membranes are presented with the hope to provide insightful guidance on the future design and fabrication of high-performance MXene membranes.

Precise antibacterial therapeutics based on stimuli-responsive nanomaterials

Bacterial infection refers to the process in which bacteria invade, grow, reproduce, and interact with the body, ultimately causing a series of pathological changes. Nowadays, bacterial infection remains a significant public health issue, posing a huge threat to human health and a serious financial burden. In the post-antibiotic era, traditional antibiotics are prone to inducing bacterial resistance and difficulty in removing bacterial biofilm. In recent years, antibacterial therapy based on nanomaterials has developed rapidly. Compared with traditional antibiotics, nanomaterials effectively remove bacterial biofilms and rarely result in bacterial resistance. However, due to nanomaterials' strong permeability and effectiveness, they will easily cause cytotoxicity when they are not controlled. In addition, the antibacterial effect of non-responsive nanomaterials cannot be perfectly exerted since the drug release property or other antibacterial effects of these nano-materials are not be positively correlated with the intensity of bacterial infection. Stimuli-responsive antibacterial nanomaterials are a more advanced and intelligent class of nano drugs, which are controlled by exogenous stimuli and microenvironmental stimuli to change the dosage and intensity of treatment. The excellent spatiotemporal controllability enables stimuli-responsive nanomaterials to treat bacterial infections precisely. In this review, we first elaborate on the design principles of various stimuli-responsive antibacterial nanomaterials. Then, we analyze and summarizes the antibacterial properties, advantages and shortcomings of different applied anti-bacterial strategies based on stimuli-responsive nanomaterials. Finally, we propose the challenges of employing stimuli-responsive nanomaterials and corresponding potential solutions.

Self-assembly fabrication of chitosan-tannic acid/MXene composite film with excellent antibacterial and antioxidant properties for fruit preservation

It is highly urgent to develop a simple and effective strategy to extend the shelf life of time-sensitive fruits, which are very susceptible to spoilage over time, resulting in considerable food waste. Herein, a biopolymer-based composite film with superior antibacterial and antioxidant properties was developed by introducing MXene and tannic acid into a chitosan network via hydrogen bonding and an electrostatic self-assembly method. The results show that the mechanical properties, water and heat resistance, antibacterial and antioxidant capabilities of the obtained Chitosan-Tannic acid/MXene film are significantly increased to meet the use of packaging film scenarios. The fruit preservation experiments also confirmed that the composite film can effectively extend the shelf life of bananas and grapes through its excellent water vapor and oxygen barrier. These desirable performances enable our newly designed composite film to be an effective and competitive packaging material to solve the fresh fruit preservation dilemma.

Recent nanotechnology-based strategies for interfering with the life cycle of bacterial biofilms

Biofilm formation plays an important role in the resistance development in bacteria to conventional antibiotics. Different properties of the bacterial strains within biofilms compared with their planktonic states and the protective effect of extracellular polymeric substances contribute to the insusceptibility of bacterial cells to conventional antimicrobials. Although great effort has been devoted to developing novel antibiotics or synthetic antibacterial compounds, their efficiency is overshadowed by the growth of drug resistance. Developments in nanotechnology have brought various feasible strategies to combat biofilms by interfering with the biofilm life cycle. In this review, recent nanotechnology-based strategies for interfering with the biofilm life cycle according to the requirements of different stages are summarized. Additionally, the importance of strategies that modulate the bacterial biofilm microenvironment is also illustrated with specific examples. Lastly, we discussed the remaining challenges and future perspectives on nanotechnology-based strategies for the treatment of bacterial infection.

A Superhydrophilic, Light/Microwave-Absorbing Coating with Remarkable Antibacterial Efficacy

Driven by the overuse of antibiotics, pathogenic infections, dominated by the rapid emergence of antibiotic resistant bacteria, have become one of the greatest current global health challenges. Thus, there is an urgent need to explore novel strategies that integrate multiple antibacterial modes to deal with bacterial infections. In this work, a Co(Ni,Ag)/Fe(Al,Cr)₂O₄ composite duplex coating was fabricated using template-free sputtering deposition technology. The phase constitution of the coating was estimated to be 79 wt % Fe(Al,Cr)₂O₄ phase and 21 wt % of an Ag-containing metallic phase. The composite coating consisted of a ∼10 μm-thick porous outer-layer and a ∼6 μm-thick compact inner-layer, in which the outer-layer is composed of a densely stacked array of microscale cones. After exposure to ambient air for 14 days, the composite coating showed a wettability transition from a superhydrophilic nature to exhibit adhesive superhydrophobic behavior with a water contact angle of 142° ± 2.8°, but it reverted to its initial superhydrophilic state after annealing in air at 200 °C for 5 h. The absorption rate of the as-received composite coating exceeds 99% in a broad band spanning both the visible and NIR regions and showed a high photothermal efficiency to convert photon energy into heat. Similarly, the composite coating showed microwave absorption behavior with a minimum reflection loss value of 38 dB at 4.4 GHz. In vitro antibacterial tests were used to determine the antibacterial behavior of the composite coating against Escherichia coli and Staphylococcus aureus after 60 min of visible light irradiation. After this exposure, the as-prepared composite coating exhibited nearly 100% bactericidal efficiency against these bacteria. The antibacterial behavior of the coating was attributed to the synergistic effects of the superhydrophilic surface, the release of Ag⁺ ions, and the photothermal effect. Therefore, this composite coating may be a promising candidate to efficiently combat medical device-associated infections.