Molecular Sizes and Antibacterial Performance Relationships of Flexible Ionic Liquid Derivatives

Utilization of deep eutectic solvent as a degumming protocol for raw silk: Towards performance and mechanism elucidation

Degumming is the most critical step for the silk textile industry and the process of silk-based advanced materials. However, current common degumming techniques are largely limited because of insufficient efficiency, obvious hydrolysis damage and difficulty in long-term storage. Here, deep eutectic solvent (DES) constituted of choline chloride (ChCl) and urea was explored to Bombyx mori silk fibers degumming without combining any further treatment. Compared to traditional alkali methods, DES could quickly remove about 26.5 % of sericin in just 40 min, and its degumming efficiency hardly decrease after seven cycles. Owing to the "tear off" degumming mechanism of DES molecules with "large volume", the resulted sericin has a large molecular weight of 250 kDa. In addition, because of antibacterial activity and stabilizing effect, no aggregation occurred and strong bacterial growth inhibition was triggered in the obtained sericin/DES solution. Furthermore, thanks to the good retention of crystalline region and slight swelling of amorphous area, the sericin-free fibroin showed significant increases in moisture absorption and dye uptake, while maintaining good mechanical properties. Featured with high efficiency, reduction in water pollution, easy storage of sericin as well as high quality fibers, this approach is of great potential for silk wet processing.

Antimicrobial and Antiviral Nanofibers Halt Co-Infection Spread via Nuclease-Mimicry and Photocatalysis

The escalating spread of drug-resistant bacteria and viruses is a grave concern for global health. Nucleic acids dominate the drug-resistance and transmission of pathogenic microbes. Here, imidazolium-type poly(ionic liquid)/porphyrin (PIL-P) based electrospun nanofibrous membrane and its cerium (IV) ion complex (PIL-P-Ce) are developed. The obtained PIL-P-Ce membrane exhibits high and stable efficiency in eradicating various microorganisms (bacteria, fungi, and viruses) and decomposing microbial antibiotic resistance genes and viral nucleic acids under light. The nuclease-mimetic and photocatalytic mechanisms of the PIL-P-Ce are elucidated. Co-infection wound models in mice with methicillin-resistant S. aureus and hepatitis B virus demonstrate that PIL-P-Ce integrate the triple effects of cationic polymer, photocatalysis, and nuclease-mimetic activities. As revealed by proteomic analysis, PIL-P-Ce shows minimal phototoxicity to normal tissues. Hence, PIL-P-Ce has potential as a "green" wound dressing to curb the spread of drug-resistant bacteria and viruses in clinical settings.

Intracellular infection-responsive macrophage-targeted nanoparticles for synergistic antibiotic immunotherapy of bacterial infection

Intracellular bacteria are considered to play a key role in the failure of bacterial infection therapy and increase of antibiotic resistance. Nanotechnology-based drug delivery carriers have been receiving increasing attention for improving the intracellular antibacterial activity of antibiotics, but are accompanied by disadvantages such as complex preparation procedures, lack of active targeting, and monotherapy, necessitating further design improvements. Herein, nanoparticles targeting bacteria-infected macrophages are fabricated to eliminate intracellular bacterial infections via antibiotic release and upregulation of intracellular reactive oxygen species (ROS) levels and proinflammatory responses. These nanoparticles were formed through the reaction of the amino group on selenocystamine dihydrochloride and the aldehyde group on oxidized dextran (ox-Dex), which encapsulates vancomycin (Van) through hydrophobic interactions. These nanoparticles could undergo targeted uptake by macrophages via endocytosis and respond to the bacteria-infected intracellular microenvironment (ROS and glutathione (GSH)) for controlled release of antibiotics. Furthermore, these nanoparticles could consume intracellular GSH and promote a significant increase in the level of ROS in macrophages, subsequently up-regulating the proinflammatory response to reinforce antibacterial activity. These nanoparticles can accelerate bacteria-infected wound healing. In this work, nanoparticles were fabricated for bacteria-infected macrophage-targeted and microenvironment-responsive antibiotic delivery, cellular ROS generation, and proinflammatory up-regulation activity to eliminate intracellular bacteria, which opens up a new possibility for multifunctional drug delivery against intracellular infection.

Ionic Liquid Gating Induces Anomalous Permeation through Membrane Channel Proteins

Membrane channel proteins (MCPs) play key roles in matter transport through cell membranes and act as major targets for vaccines and drugs. For emerging ionic liquid (IL) drugs, a rational understanding of how ILs affect the structure and transport function of MCP is crucial to their design. In this work, GPU-accelerated microsecond-long molecular dynamics simulations were employed to investigate the modulating mechanism of ILs on MCP. Interestingly, ILs prefer to insert into the lipid bilayer and channel of aquaporin-2 (AQP2) but adsorb on the entrance of voltage-gated sodium channels (Nav). Molecular trajectory and free energy analysis reflect that ILs have a minimal impact on the structure of MCPs but significantly influence MCP functions. It demonstrates that ILs can decrease the overall energy barrier for water through AQP2 by 1.88 kcal/mol, whereas that for Na+ through Nav is increased by 1.70 kcal/mol. Consequently, the permeation rates of water and Na+ can be enhanced and reduced by at least 1 order of magnitude, respectively. Furthermore, an abnormal IL gating mechanism was proposed by combining the hydrophobic nature of MCP and confined water/ion coordination effects. More importantly, we performed experiments to confirm the influence of ILs on AQP2 in human cells and found that treatment with ILs significantly accelerated the changes in cell volume in response to altered external osmotic pressure. Overall, these quantitative results will not only deepen the understanding of IL-cell interactions but may also shed light on the rational design of drugs and disease diagnosis.

A Hemoglobin Bionics-Based System for Combating Antibiotic Resistance in Chronic Diabetic Wounds via Iron Homeostasis Regulation

Owing to the increased tissue iron accumulation in patients with diabetes, microorganisms may activate high expression of iron-involved metabolic pathways, leading to the exacerbation of bacterial infections and disruption of systemic glucose metabolism. Therefore, an on-demand transdermal dosing approach that utilizes iron homeostasis regulation to combat antimicrobial resistance is a promising strategy to address the challenges associated with low administration bioavailability and high antibiotic resistance in treating infected diabetic wounds. Here, it is aimed to propose an effective therapy based on hemoglobin bionics to induce disturbances in bacterial iron homeostasis. The preferred "iron cargo" is synthesized by protoporphyrin IX chelated with dopamine and gallium (PDGa), and is delivered via a glucose/pH-responsive microneedle bandage (PDGa@GMB). The PDGa@GMB downregulates the expression levels of the iron uptake regulator (Fur) and the peroxide response regulator (perR) in Staphylococcus aureus, leading to iron nutrient starvation and oxidative stress, ultimately suppressing iron-dependent bacterial activities. Consequently, PDGa@GMB demonstrates insusceptibility to genetic resistance while maintaining sustainable antimicrobial effects (>90%) against resistant strains of both S. aureus and E. coli, and accelerates tissue recovery (<20 d). Overall, PDGa@GMB not only counteracts antibiotic resistance but also holds tremendous potential in mediating microbial-host crosstalk, synergistically attenuating pathogen virulence and pathogenicity.

Cascade-Targeted Nanoplatforms for Synergetic Antibiotic/ROS/NO/Immunotherapy against Intracellular Bacterial Infection

Intracellular bacteria in dormant states can escape the immune response and tolerate high-dose antibiotic treatment, leading to severe infections. To overcome this challenge, cascade-targeted nanoplatforms that can target macrophages and intracellular bacteria, exhibiting synergetic antibiotic/reactive oxygen species (ROS)/nitric oxide (NO)/immunotherapy, were developed. These nanoplatforms were fabricated by encapsulating trehalose (Tr) and vancomycin (Van) into phosphatidylserine (PS)-coated poly[(4-allylcarbamoylphenylboric acid)-ran-(arginine-methacrylamide)-ran-(N,N'-bisacryloylcystamine)] nanoparticles (PABS), denoted as PTVP. PS on PTVP simulates a signal of "eat me" to macrophages to promote cell uptake (the first-step targeting). After the uptake, the nanoplatform in the acidic phagolysosomes could release Tr, and the exposed phenylboronic acid on the nanoplatform could target bacteria (the second-step targeting). Nanoplatforms can release Van in response to infected intracellular overexpressed glutathione (GSH) and weak acid microenvironment. l-arginine (Arg) on the nanoplatforms could be catalyzed by upregulated inducible nitric oxide synthase (iNOS) in the infected macrophages to generate nitric oxide (NO). N,N'-Bisacryloylcystamine (BAC) on nanoplatforms could deplete GSH, allow the generation of ROS in macrophages, and then upregulate proinflammatory activity, leading to the reinforced antibacterial capacity. This nanoplatform possesses macrophage and bacteria-targeting antibiotic delivery, intracellular ROS, and NO generation, and pro-inflammatory activities (immunotherapy) provides a new strategy for eradicating intracellular bacterial infections.

Protein Interface Regulating the Inserting Process of Imidazole Ionic Liquids into the Cell Membrane

Ionic liquids (ILs) have shown promising potential in membrane protein extraction; however, the underlying mechanism remains unclear. Herein, we employed GPU-accelerated molecular dynamics (MD) simulations to investigate the dynamic insertion process of ILs into cell membranes containing membrane proteins. Our findings reveal that ILs spontaneously insert into the membrane, and the presence of membrane proteins significantly decelerates the rate of IL insertion into the membrane. Specifically, the relationship between the insertion rate and inserting free energy exhibits non-monotonic changes, which can be attributed to interfacial effects. The protein-water interface acts as trap for free ions and ionic clusters, while free ions preferentially insert into the membrane from the protein-lipid interface, which limits the insertion rate due to its narrowness. Thus, the insertion rate is governed by a combination of the free energy and interfacial effects. These findings provide valuable insights into the interfacial effects of protein-lipid bilayers and have implications for various biochemical-related applications.

Polydopamine contained hydrogel nanocomposites with combined antimicrobial and antioxidant properties for accelerated wound healing

Overproduction of reactive oxygen species (ROS) in infected wounds induces a tremendous inflammatory reaction to delay wound healing. To address this problem, we designed a multifunctional polyacrylamide/PVA-based hydrogel containing synthesized poly(1-glycidyl-3-butylimidazolium salicylate) (polyGBImSal) and fabricated polydopamine-coated polyphenolic nanosheet (PDA@PNS) for wound dressing. The PDA@PNS particles were designed to induce I) antioxidant and anti-inflammatory features through ROS-scavenging and II) cell adhesive properties by the existing polydopamine into the hydrogels. The poly(ionic liquid)-based polyGBImSal was designed to allocate effective hydrogel antimicrobial activity. The fabricated hydrogel nanocomposites showed excellent properties in the swelling ratio, cell adhesiveness, protein adsorption, and anti-inflammatory, proving their general performance for application in wound healing. Furthermore, these hydrogels showed high antimicrobial activity (over 95 %) against three common wound-infecting pathogenic microbes: Escherichia coli, Staphylococcus aureus, and Candida albicans. The healing process of full-thickness dermal wounds in rats was accelerated by applying hydrogel nanocomposites with 0.5 wt% of PDA@PNS and 28 wt% of polyGBImSal. The wound closure contraction attained full closure, reaching 100 %, after 14 days, contrasted with the control group employing commercial wound dressing (Tegaderm), which achieved a closure rate of 68 % within the equivalent timeframe. These results make these hydrogel nanocomposites promising candidates for multifunctional wound dressing applications.

Grafting of Poly(ionic liquid) Brushes through Fe0-Mediated Surface-Initiated Atom Transfer Radical Polymerization for Marine Antifouling

Surface-tethered poly(ionic liquid) brushes have attracted considerable attention in widespread fields, from bioengineering to marine antifouling. However, their applications have been constrained due to the poor polymerization efficiency and sophisticated operation process. In this work, we efficiently synthesized the poly(ionic liquid) brushes with unparalleled speed (up to 98 nm h-1) through Fe0-mediated surface-initiated atom transfer radical polymerization (Fe0 SI-ATRP) while consuming only microliter of monomer solution under ambient conditions. We also demonstrated that poly(ionic liquid) brushes with gradient thickness and wettability were easily accessible by regulating the distance between the opposite plates of Fe0 SI-ATRP. Moreover, the resultant poly(ionic liquid) brushes presented excellent antibacterial activities against Escherichia coli (99.2%) and Bacillus subtilis (88.1%) after 24 h and low attachment for proteins and marine algae (≤5%) for over 2 weeks. This research provided pathways to the facile and controllable fabrication of poly(ionic liquid) materials for marine antifouling applications.

Tracing the Antibacterial Performance of Bis-Imidazolium-based Ionic Liquid Derivatives

Ionic liquid (IL) cationic species have recently captivated the attention of pharmacists, biochemists, and biomedical scientists as promising antibacterial agents to deal with the multidrug resistance bacteria crisis. The structure and functional groups of ILs influence their physiochemical properties and biological activities. However, a comprehensive study is required to fully understand the details of the antibacterial activity of ILs carrying various functional groups. Herein, dicationic ILs (DCILs) are reported based on imidazolium rings as efficient antibacterial agents. The DCILs carried various functionalities such as 2-hydroxybutyl (DCIL-1), 2-hydroxy-3-isopropoxypropyl (DCIL-2), 2-hydroxy-3-(methacryloyloxy)propyl (DCIL-3), 2-hydroxy-2-phenylethyl (DCIL-4), and 2-hydroxy-3-phenoxypropyl (DCIL-5). The structure-antibacterial activity relationships of the DCILs against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were comprehensively studied through antibacterial tests, morphology analysis, and adhesion tests. The experimental assays revealed an antibacterial efficacy order of DCIL-5 > DCIL-1 > DCIL-4 > DCIL-2 > DCIL-3. The all-atom molecular dynamics (MD) simulation showed a deep permeation of the hydrophobic -OPh functional group of DCIL-5 through the E. coli membrane model in agreement with the experimental observations. Current findings assist scientists in designing new task-specific DCILs for effective interactions with biological membranes for different applications.

Design, synthesis and antibacterial evaluation of low toxicity amphiphilic-cephalosporin derivatives

Global public health is facing a serious problem as a result of the rise in antibiotic resistance and the decline in the discovery of new antibiotics. In this study, two series of amphiphilic-cephalosporins were designed and synthesized, several of which showed good antibacterial activity against both Gram-positive and Gram-negative bacteria. Structure-activity relationships indicated that the length of the hydrophobic alkyl chain significantly affects the antibacterial activity against Gram-negative bacteria. The best compound 2d showed high activity against drug-susceptible Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with MICs of 0.5 and 2-4 μg/mL, respectively. Furthermore, 2d remained active in complex mammalian body fluids and had a longer post-antibiotic effect (PAE) than vancomycin. Mechanism studies indicated that compound 2d lacks membrane-damaging properties and can target penicillin-binding proteins to disrupt bacterial cell wall structure, inhibit the metabolic activity and induce the accumulation of reactive oxygen species (ROS) in bacteria. Compound 2d showed minimal drug resistance and was nontoxic to HUVEC and HBZY-1 cells with CC50 > 128 μg/mL. These findings suggest that 2d is a promising drug candidate for treating bacterial infections.

Novel aminothiazoximone-corbelled ethoxycarbonylpyrimidones with antibiofilm activity to conquer Gram-negative bacteria through potential multitargeting effects

The emergence of drug-resistant microorganisms threatens human health, and it is usually exacerbated by the formation of biofilm, which forces the development of new antibacterial agents with antibiofilm activity. In this work, a novel category of aminothiazoximone-corbelled ethoxycarbonylpyrimidones (ACEs) was designed and synthesized, and some of the prepared ACEs showed potent bioactivity against the tested bacteria. In particular, imidazolyl ACE 6c showed better inhibitory activity towards Acinetobacter baumannii and Escherichia coli with MIC values both of 0.0066 mmol/L than norfloxacin. It was also revealed that imidazolyl ACE 6c not only possessed inconspicuous hemolytic rate and cytotoxicity, low drug resistance and no risk of penetrating the blood-brain barrier, but also exhibited obvious biofilm inhibition and eradication activities. The preliminary mechanism research suggested that imidazolyl ACE 6c could induce metabolic dysfunction by deactivating lactate dehydrogenase and promote the accumulation of reactive oxygen species to decrease the reduced glutathione and ultimately cause oxidative damage in bacteria. Furthermore, ACE 6c was also found that could insert into DNA to form the supramolecular complex of 6c-DNA and trigger cell death. The multidimensional effect might promote bacterial cell rupture, leading to the leakage of intracellular content. These findings manifested that novel imidazolyl ACE 6c as a potential multitargeting antibacterial agent with potent antibiofilm activity could provide new possibility for the treatment of refractory biofilm-intensified bacterial infections.

Recent progress on bismuth-based light-triggered antibacterial nanocomposites: Synthesis, characterization, optical properties and bactericidal applications

Bacterial infections pose a seriously threat to the safety of the environment and human health. In particular, the emergence of drug-resistant pathogens as a result of antibiotic abuse and high trauma risk has rendered conventional therapeutic techniques insufficient for treating infections by these so-called "superbugs". Therefore, there is an urgent need to develop highly efficient and environmentally-friendly antimicrobial agents. Bismuth-based nanomaterials with unique structures and physicochemical characteristics have attracted considerable attention as promising antimicrobial candidates, with many demonstratingoutstanding antibacterial effects upon being triggered by broad-spectrum light. These nanomaterials have also exhibited satisfactory energy band gaps and electronic density distribution with improved photonic properties for extensive and comprehensive applications after being modified through various engineering methods. This review summarizes the latest research progress made on bismuth-based nanomaterials with different morphologies, structures and compositions as well as the different methods used for their synthesis to meet their rapidly increasing demand, especially for antibacterial applications. Moreover, the future prospects and challenges regarding the application of these nanomaterials are discussed. The aim of this review is to stimulate interest in the development and experimental transformation of novel bismuth-based nanomaterials to expand the arsenal of effective antimicrobials.

Effective ciprofloxacin cationic antibacterial agent against persister bacteria with low hemolytic toxicity

With the widespread use of antibiotics, bacterial resistance has developed rapidly. To make matters worse, infections caused by persistent bacteria and biofilms often cannot be completely eliminated, which brings great difficulties to clinical medication. In this work, three series of quinolone pyridinium quaternary ammonium small molecules were designed and synthesized. Most of the compounds showed good antibacterial activity against Gram-positive bacteria (S. aureus and E. faecalis) and Gram-negative bacteria (E. coli and S. maltophilia). The activity of the para-pyridine quaternary ammonium salt was better than that of the meta-pyridine. 3f was the optimal compound with good stability in body fluids and was unlikely to induce bacterial resistance. The hemolysis rate of erythrocytes at 1280 μg/mL for 3f was only 5.1%. Encouragingly, 3f rapidly killed bacteria within 4 h at 4 × MIC concentration and was effective in killing persistent bacteria in biofilms. The antibacterial mechanism experiments showed that 3f could cause disorder of bacterial membrane potential, increase bacterial membrane permeability, dissolve and destroy the membrane. Incomplete bacterial membranes lead to leakage of bacterial genetic material, concomitant production of ROS, and bacterial death due to these multiple effects.

Tannic acid and carboxymethyl chitosan-based multi-functional double-layered hydrogel with pH-stimulated response behavior for smart real-time infection monitoring and wound treatment

The dramatic increase of drug-resistant pathogenic bacteria has seriously effect on human health, appealing the needs of developing theranostic platforms with stimuli-responsive materials to realize the accurate bacterial diagnostics and therapeutics. Herein, a tannic acid and carboxymethyl chitosan-based multifunctional ZIF-90@i-PPOPs-phenol red double-layered hydrogel with stimuli-responsiveness and antibacterial activity was fabricated. The inner layer hydrogel (ZIF-90@i-PPOPs-based TFC hydrogels) was fabricated based on ZIF-90@i-PPOPs, integrate tannic acid and carboxymethyl chitosan linked by formylphenylboronic acid (FPBA), which exhibited outstanding injectable, biodegradability and antibacterial activity. The outer layer hydrogel (PR@PAM hydrogels) were constructed from polyacrylamide (PAM) and pH indicator phenol red, owning porous structure and excellent tissue adhesion. Due to the weakly acidic microenvironment within wound, the inner-layer hydrogel was stimulus-responsively decomposed, resulting in the accurate delivery of the positively charged ZIF-90@i-PPOPs to the lesion site to capture and kill bacteria by enhanced Zn2+ and ROS release. Meantime, the outer-layer hydrogel could real-timely monitor the pH changes to evaluate the wound recovery status. These double-layered hydrogels possessed precisely pH monitoring capacity, excellent antibacterial ability and negligible side effect to normal tissue in vivo, implying the high potential of the suggested hydrogels as theranostic platform for antibacterial treatment.

Influence of the linkage between long alkyl tails and cationic groups on membrane activity of nano-sized hyperbranched polyquaterniums

The recurrent emergence of serious pathogens necessitates novel insights and highly efficient antibacterial agents. However, the innate inability of metal ions and reactive oxygen species (ROS) to differentiate between bacteria and mammalian cells presents a challenge, limiting the selectivity crucial for an ideal antimicrobial solution. Herein, we present a systematic exploration involving two variants of nano-sized hyperbranched polyquaterniums (NHBPQs) - one featuring a lengthy alkyl tail linked to the ammonium unit at the N-atom center (NHBPQ-A), and the other in a segregated configuration (NHBPQ-B). The exterior alkyl chain chains act as a barrier to the cationic group's non-specific adsorption due to spatial site resistance, causing NHBPQ-A in broad-spectrum cytotoxicity. Conversely, the distinct molecular configuration of NHBPQ-B in the segregated state affords greater flexibility, allowing the cationic groups to be released and interact non-specifically, finally resulting in selective bactericidal activity. Leveraging this selectivity, the optimized NHBPQ-B exhibits robust anti-infectious performance in a model of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds. This work establishes a promising avenue for biocompatible NHBPQs, holding significant potential in addressing MRSA infections and ameliorating both genetically encoded and phenotypic antibiotic resistance mechanisms.

Supramolecular pyrrole radical cations for bacterial theranostics

Bacterial infections with emerging resistance to antibiotics require urgent development of antibacterial agents with new core skeletons. Recently, a series of antibacterial agents have been reported based on positively charged organic groups, such as ammonium, guanidine, and phosphonium groups, which can selectively bind and destroy negatively charged bacterial membranes. To achieve imaging-guided precise antibacterial therapy, these positively charged organic groups usually require further decoration with imaging modalities, such as fluorescence. However, most fluorophores with electron-closed shell structures usually suffer from tedious synthetic procedures for preparation. We herein prepare a series of positively charged and deep-red fluorescent supramolecular pyrrole radical cations (P˙+-CB[7]) based on the simple mixing of pyrroles and CB[7] in water under air. The readily available deep-red fluorescent P˙+-CB[7] can not only be used for selective imaging and killing of live Gram-positive bacteria with excellent biocompatibility, but also for imaging of dead Gram-negative bacteria killed by drugs and in vivo monitoring of phagocytosis of bacteria by innate immune cells in zebrafish. It is believed that the deep-red fluorescent pyrrole radical cations as a new core skeleton are promising in bacterial theranostics.

Design of biodegradable polyurethanes and post-modification with long alkyl chains via inhibiting biofilm formation and killing drug-resistant bacteria for the treatment of wound bacterial infection

The development of cationic polymers that simulate antimicrobial peptides to treat bacterial infections has received much research interest. In order to obtain polymers that can not only eradicate bacteria but also inhibit biofilm formation, without inducing bacterial drug resistance, a series of cationic polymers have been developed. Despite recent progress, the chemical structures of these polymers are stable, making them recalcitrant to biodegradation and metabolism within organisms, potentially inducing long-term toxicity. To overcome this limitation, herein, a novel strategy of designing biodegradable polyurethanes with tertiary amines and quaternary ammonium salts via condensation polymerization and post-functionalizing them is reported. These polymers were found to exhibit potent antibacterial activity against Staphylococcus aureus and Escherichia coli, effectively prevent the formation of Staphylococcus aureus biofilms, act quickly and effectively against bacteria and display no resistance after repeated use. In addition, the potent in vivo antibacterial effects of these antimicrobial polyurethanes in a mouse model with methicillin-resistant Staphylococcus aureus skin infection are demonstrated.

Cationic Porphyrin-Based Ionic Nanomedicines for Improved Photodynamic Therapy

This study presents the synthesis and characterization of monosubstituted cationic porphyrin as a photodynamic therapeutic agent. Cationic porphyrin was converted into ionic materials by using a single-step ion exchange reaction. The small iodide counteranion was replaced with bulky BETI and IR783 anions to reduce aggregation and enhance the photodynamic effect of porphyrin. Carrier-free ionic nanomedicines were then prepared by using the reprecipitation method. The photophysical characterization of parent porphyrin, ionic materials, and ionic nanomaterials, including absorbance, fluorescence and phosphorescence emission, quantum yield, radiative and nonradiative rate, and lifetimes, was performed. The results revealed that the counteranion significantly affects the photophysical properties of porphyrin. The ionic nanomaterials exhibited an increase in the reactive oxygen yield and enhanced cytotoxicity toward the MCF-7 cancer cell line. Examination of results revealed that the ionic materials exhibited an enhanced photodynamic therapeutic activity with a low IC50 value (nanomolar) in cancerous cells. These nanomedicines were mainly localized in the mitochondria. The improved light cytotoxicity is attributed to the enhanced photophysical properties and positive surface charge of the ionic nanomedicines that facilitate efficient cellular uptake. These results demonstrate that ionic material-based nanodrugs are promising photosensitizers for photodynamic therapy.

A novel fluorescent traceable carbon quantum dots with selective antibacterial activity against Porphyromonas gingivalis

Antibiotics can kill bacteria, but their continued use can easily lead to drug resistance, particularly the main pathogenic bacteria of periodontitis, Porphyromonas gingivalis. However, to avoid drug resistance, carbon quantum dots (CDs) have great potential as a bioactive material in antimicrobial therapy. Herein, we use ornidazole as raw material to prepare CDs of different sizes by microwave irradiation and screen CDs with fluorescence and bacteriostatic properties. The inhibition experiments and live/dead assays of P. gingivalis exhibited outstanding antibacterial effects. This research aimed to develop nano-level antibacterial active materials that also have fluorescence traceability. This study offers a different method for the development of multifunctional CDs, provides valuable strategies for the treatment of diseases associated with P. gingivalis, and predicts great application prospects in the field of biomedicine.

Ionic liquids revolutionizing biomedicine: recent advances and emerging opportunities

Ionic liquids (ILs), due to their inherent structural tunability, outstanding miscibility behavior, and excellent electrochemical properties, have attracted significant research attention in the biomedical field. As the application of ILs in biomedicine is a rapidly emerging field, there is still a need for systematic analyses and summaries to further advance their development. This review presents a comprehensive survey on the utilization of ILs in the biomedical field. It specifically emphasizes the diverse structures and properties of ILs with their relevance in various biomedical applications. Subsequently, we summarize the mechanisms of ILs as potential drug candidates, exploring their effects on various organisms ranging from cell membranes to organelles, proteins, and nucleic acids. Furthermore, the application of ILs as extractants and catalysts in pharmaceutical engineering is introduced. In addition, we thoroughly review and analyze the applications of ILs in disease diagnosis and delivery systems. By offering an extensive analysis of recent research, our objective is to inspire new ideas and pathways for the design of innovative biomedical technologies based on ILs.

Nitrogen-phosphorous co-doped carbonized chitosan nanoparticles for chemotherapy and ROS-mediated immunotherapy of intracellular Staphylococcus aureus infection

Staphylococcus aureus (S. aureus) residing in host macrophages is hard to clear because intracellular S. aureus has evolved mechanisms to hijack and subvert the immune response to favor intracellular infection. To overcome this challenge, nitrogen-phosphorous co-doped carbonized chitosan nanoparticles (NPCNs), which possess the polymer/carbon hybrid structures, were fabricated to clear intracellular S. aureus infection through chemotherapy and immunotherapy. Multi-heteroatom NPCNs were fabricated through the hydrothermal method, where chitosan and imidazole were used as the C and N sources and phosphoric acid as the P source. NPCNs can not only be used as a fluorescent probe for bacteria imaging but also kill extracellular and intracellular bacteria with low cytotoxicity. NPCNs could generate ROS and polarize macrophages into classically activated (M1) phenotypes to increase antibacterial immunity. Furthermore, NPCNs could accelerate intracellular S. aureus-infected wound healing in vivo. We envision that these carbonized chitosan nanoparticles may provide a new platform for clearing intracellular bacterial infection through chemotherapy and ROS-mediated immunotherapy.

Flexible Modulation of Cellular Activities with Cationic Photosensitizers: Insights of Alkyl Chain Length on Reactive Oxygen Species Antimicrobial Mechanisms

Cationic photosensitizers have good binding ability with negatively charged bacteria and fungi, exhibiting broad applications potential in antimicrobial photodynamic therapy (aPDT). However, cationic photosensitizers often display unsatisfactory transkingdom selectivity between mammalian cells and pathogens, especially for eukaryotic fungi. It is unclear which biomolecular sites are more efficient for photodynamic damage, owing to the lack of systematic research with the same photosensitizer system. Herein, a series of cationic aggregation-induced emission (AIE) derivatives (CABs) (using berberine (BBR) as the photosensitizers core) with different length alkyl chains are successfully designed and synthesized for flexible modulation of cellular activities. The BBR core can efficiently produce reactive oxygen species (ROS) and achieve high-performance aPDT . Through the precise regulation of alkyl chain length, different bindings, localizations, and photodynamic killing effects of CABs are achieved and investigated systematically among bacteria, fungi, and mammalian cells. It is found that intracellular active substances, not membranes, are more efficient damage sites of aPDT. Moderate length alkyl chains enable CABs to effectively kill Gram-negative bacteria and fungi with light, while still maintaining excellent mammalian cell and blood compatibility. This study is expected to provide systematic theoretical and strategic research guidance for the construction of high-performance cationic photosensitizers with good transkingdom selectivity.

Electropolymerization of Pyrrole-Tailed Imidazolium Ionic Liquid for the Elaboration of Antibacterial Surfaces

A strategy was developed to prepare antibacterial surfaces by electropolymerization of a pyrrole-functionalized imidazolium ionic liquid bearing an halometallate anion. The objective was to combine the antibacterial efficiency of polypyrrole (PPy) with those of the ionic liquid's components (cation and anion). For this, N-(1-methyl-3-octylimidazolium)pyrrole bromide monomer [PyC₈MIm]Br was synthesized and coordinated to ZnCl₂ affording [PyC₈MIm]Br-ZnCl₂. The antibacterial properties of [PyC₈MIm]Br-ZnCl₂ monomer were evaluated against Escherichia coli and Staphylococcus aureus by measurement of the minimum inhibitory concentration (MIC) values. This monomer presents higher activity against S. aureus (MIC = 0.098 μmol·mL^-1) than against E. coli (MIC = 2.10 μmol·mL^-1). Mixtures of pyrrole and the pyrrole-functionalized ionic liquid [PyC₈MIm]Br-ZnCl₂ were then used for the electrodeposition of PPy films on Fluorine-doped tin oxide (FTO) substrates. The concentration of pyrrole was fixed to 50 mM, while the concentration of [PyC₈MIm]Br-ZnCl₂ was varied from 5 to 100 mM. The efficient incorporation of the imidazolium cation and zinc halometallate anion into the films was confirmed by X-ray photoelectron spectroscopy (XPS) measurements. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements confirmed the homogeneity of the different films with structures that depend on the [PyC₈MIm]Br-ZnCl₂ concentration. The films' thickness determined by profilometry varies only slightly with the [PyC₈MIm]Br-ZnCl₂ concentration from 7.4 μm at 5 mM to 8.9 μM at 100 mM. The films become more hydrophilic with an increase of [PyC₈MIm]Br-ZnCl₂ concentration with water contact angles varying from 47° at the lowest concentration to 32° at the highest concentration. The antibacterial activities of the different PPy films were determined both by the halo inhibition method and by the colony forming units (CFUs) counting method over time against Gram-positive S. aureus and Gram-negative E. coli bacteria. Films obtained by incorporation of [PyC₈MIm]Br-ZnCl₂ showed excellent antibacterial properties, at least two times higher than those of neat PPy, validating our strategy. Furthermore, a comparison of the antibacterial properties of the films obtained using the same [PyC₈MIm]Br-ZnCl₂ concentration (50 mM) evidenced much better activity against Gram-positive (no bacterial survival within 5 min) than against Gram-negative bacteria (no bacterial survival within 3 h). Finally, the antibacterial performances over time could be tuned by the concentration of the employed pyrrole-functionalized ionic liquid monomer. Against E. coli, using 100 mM of [PyC₈MIm]Br-ZnCl₂, the bacteria were totally killed within a few minutes, using 50 mM, they were killed after 2 h while using 10 mM, about 20% of bacteria survived even after 6 h.

Enzymatic Self-Assembly of Adamantane-Peptide Conjugate for Combating Staphylococcus aureus Infection

Staphylococcus aureus (S. aureus) remains a leading cause of bacterial infections. However, eradication of S. aureus infections with common antibiotics is increasingly difficult due to outbreaks of drug resistance. Therefore, new antibiotic classes and antibacterial strategies are urgently in demand. Herein, it is shown that an adamantane-peptide conjugate, upon dephosphorylation by alkaline phosphatase (ALP) constitutively expressed on S. aureus, generates fibrous assemblies in situ to combat S. aureus infection. By attaching adamantane to a phosphorylated tetrapeptide Nap-Phe-Phe-Lys-Tyr(H2 PO3 )-OH, the rationally designed adamantane-peptide conjugate Nap-Phe-Phe-Lys(Ada)-Tyr(H2 PO3 )-OH (Nap-FYp-Ada) is obtained. Upon bacterial ALP activation, Nap-FYp-Ada is dephosphorylated and self-assembles into nanofibers on the surface of S. aureus. As revealed by cell assays, the assemblies of adamantane-peptide conjugates interact with cell lipid membrane and thereby disrupt membrane integrity to kill S. aureus. Animal experiments further demonstrate the excellent potential of Nap-FYp-Ada in the treatment of S. aureus infection in vivo. This work provides an alternative approach to design antimicrobial agents.

Robust Mechanical Destruction to the Cell Membrane of Carbon Nitride Polyaniline (C3N): A Molecular Dynamics Simulation Study

The drug-resistant bacteria, particularly multidrug-resistant bacteria, has emerged as a major global public health concern posing serious threats to human life and survival. Nanomaterials, including graphene, have shown promise as effective antibacterial agents owing to their unique antibacterial mechanism compared with traditional drugs. Despite the structural similarity to graphene, the potential antibacterial activity of carbon nitride polyaniline (C₃N) remains unexplored. In this study, we employed molecular dynamics simulations to investigate the effects of the interaction between the C₃N nanomaterial and the bacterial membrane to evaluate the potential antibacterial activity of C₃N. Our results suggest that C₃N is capable of inserting deep into the bacterial membrane interior, regardless of the presence or absence of positional restraints in the C₃N. The insertion process also resulted in local lipid extraction by the C₃N sheet. Additional structural analyses revealed that C₃N induced significant changes in membrane parameters, including mean square displacement, deuterium order parameters, membrane thickness, and area per lipid. Docking simulations, where all the C₃N are restraint to a specific positions, confirmed that C₃N can extract lipids from the membrane, indicating the strong interaction between the C₃N material and the membrane. Free-energy calculations further revealed that the insertion of the C₃N sheet is energetically favorable and that C₃N exhibits membrane insertion capacity comparable to that observed for graphene, suggesting their potential for similar antibacterial activity. This study provides the first evidence of the potential antibacterial properties of C₃N nanomaterials via bacterial membrane damage and underscores the potential for its use as antibacterial agents in the future applications.

Catalytic Amounts of an Antibacterial Monomer Enable the Upcycling of Poly(Ethylene Terephthalate) Waste

Poly(ethylene terephthalate) (PET) is an important polymer with an annual output second only to polyethylene. The development of PET recycling technologies is therefore necessary to not only eliminate the harm associated with white pollution and microplastics, but also to reduce carbon emissions. Antibacterial PET, one of the most high-value advanced materials, has improved the ability to treat bacterial infections. However, current methods of manufacturing commercial antibacterial PET require blending with an excess of metal-based antibacterial agents, which leads to biotoxicity and a nonpersistent antibacterial activity. In addition, high-efficiency organic antibacterial agents have yet to be employed in antibacterial PET due to their poor thermal stabilities. Herein, a solid-state reaction for the upcycling of PET waste using a novel hyperthermostable antibacterial monomer is described. This reaction is catalyzed by the residual catalyst present in the PET waste. It is found that a catalytic amount of the antibacterial monomer enabled the low-cost upcycling of PET waste to produce high-value recycled PET with a strong and persistent antibacterial activity, as well as similar thermal properties to the virgin PET. This work provides a feasible and economic strategy for the large-scale upcycling of PET waste and exhibits potential for application in the polymer industry.

Molecular Charge and Antibacterial Performance Relationships of Aggregation-Induced Emission Photosensitizers

Bacterial infections remain a major cause of morbidity worldwide due to drug resistance of pathogenic bacteria. Photodynamic therapy (PDT) has emerged as a promising approach to overcome this drug resistance. However, existing photosensitizers (PSs) are broad-spectrum antibacterial agents that dysregulate the microflora balance resulting in undesirable side effects. Herein, we synthesized a series of aggregation-induced emission (AIE)-active PSs with a lipophilic cationic AIE core with varying charges, named TBTCP and its derivatives. The association of the difference in their molecular charge with the antibacterial effects was systemically investigated. Among the derivatives presented, TBTCP-SF with the electronegative sulfonate group nulled its ability to bind to and ablate Gram-positive (G+) or Gram-negative (G-) bacteria. TBTCP-QY modified by electropositive quaternary ammonium facilitated binding and augmented the photodynamic antibacterial activity for both G+ and G- bacteria. TBTCP-PEG with hydrophilic neutral ligands selectively bound and inactivated G+ bacteria. Under white-light illumination, TBTCP-PEG ablated 99.9% methicillin-resistant Staphylococcus aureus (MRSA) and promoted wound healing in MRSA-infected mice, eliminating MRSA infection both in vitro and in vivo. Our work provides unprecedented insight into the utility of AIE-active PSs for highly targeted and efficient photodynamic ablation of either G+ or G- bacteria that can be translated to next-generation antibacterial materials.

Novel Sulfonamide Derivatives Containing a Piperidine Moiety as New Bactericide Leads for Managing Plant Bacterial Diseases

Plant bacterial diseases are an intractable problem due to the fact that phytopathogens have acquired strong resistances for traditional pesticides, resulting in restricting the quality and yield of agricultural products around the world. To develop new agrochemical alternatives, we prepared a novel series of sulfanilamide derivatives containing piperidine fragments and assessed their antibacterial potency. The bioassay results revealed that most molecules displayed excellent in vitro antibacterial potency towards Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac). In particular, molecule C₄ exhibited outstanding inhibitory activity toward Xoo with EC₅₀ value of 2.02 µg mL^-1, which was significantly better than those of the commercial agents bismerthiazol (EC₅₀ = 42.38 µg mL^-1) and thiodiazole copper (EC₅₀ = 64.50 µg mL^-1). A series of biochemical assays confirmed that compound C₄ interacted with dihydropteroate synthase, and irreversibly damaged the cell membrane. In vivo assays showed that the molecule C₄ presented acceptable curative and protection activities of 34.78% and 39.83%, respectively, at 200 µg mL^-1, which were greater than those of thiodiazole and bismerthiazol. This study highlights the valuable insights for the excavation and development of new bactericides that can concurrently target dihydropteroate synthase and bacterial cell membranes.

Phospholipid-Mimetic Aggregation-Induced Emission Luminogens for Specific Elimination of Gram-Positive and Gram-Negative Bacteria

Precise elimination of both Gram-positive and Gram-negative bacteria greatly contributes to the fight against bacterial infection but remains challenging. Herein, we present a series of phospholipid-mimetic aggregation-induced emission luminogens (AIEgens) that selectively kill bacteria by capitalizing on both the different structure of two bacterial membrane and the regulated length of substituted alkyl chains of AIEgens. Because of the positive charges that they contain, these AIEgens are able to kill bacteria by anchoring onto the bacterial membrane. For AIEgens with short alkyl chains, they could combine with the membrane of Gram-positive bacteria other than Gram-negative bacteria, because of their complicated outer layers, thus exhibiting selective ablation to Gram-positive bacteria. On the other hand, AIEgens with long alkyl chains have strong hydrophobicity with bacterial membranes, as well as large sizes. This inhibits the combination with Gram-positive bacterial membrane but destroys the membranes of Gram-negative bacteria, resulting in selective ablation to Gram-negative bacteria. Moreover, the combined processes to two bacteria are clearly observed by fluorescent imaging, and in vitro and in vivo experiments show the extraordinary antibacterial selectivity toward a Gram-positive and Gram-negative bacterium. This work could facilitate the development of species-specific antibacterial agents.

Structural optimization of BODIPY photosensitizers for enhanced photodynamic antibacterial activities

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

Novel Uracil-Functionalized Poly(ionic liquid) Hydrogel: Highly Stretchable and Sensitive as a Direct Wearable Ionic Skin for Human Motion Detection

Conductive hydrogel-based ionic skins have attracted immense attention due to their great application prospects in wearable electronic devices. However, simultaneously achieving a combination of a single hydrogel system and excellent comprehensive performance (i.e., mechanical durability, electrical sensitivity, broad-spectrum antibacterial activity, and biocompatibility) remains a challenge. Thus, a novel poly(ionic liquid) hydrogel consisting of poly(acrylamide-co-lauryl methacrylate-co-methyl-uracil-imidazolium chloride-co-2-acryloylamino-2-methyl-1-propane sulfonic acid) (AAm-LMA-MUI-AMPS) was prepared by a micellar copolymerization method. Herein, MUI serves as a supramolecular crosslinker and conductive and bacteriostatic components. Owing to the multiple supramolecular crosslinks and hydrophobic association in the network, the hydrogel exhibits excellent mechanical properties (624 kPa of breaking stress and 1243 kPa of compression stress), skin-like modulus (46.2 kPa), stretchability (1803%), and mechanical durability (200 cycles under 500% strain can be completely recovered). Moreover, with the coordinated combination of each monomer, the hydrogel exhibits the unique advantage of high conductivity (up to 59.34 mS/cm). Hence, the hydrogel was further assembled as an ionic skin sensor, which exhibited a gauge factor (GF) of 10.74 and 7.27 with and without LiCl over a broad strain range (1-1000%), respectively. Furthermore, the hydrogel sensor could monitor human movement in different strain ranges, including body movement and vocal cord vibration. In addition, the antibacterial activity and biocompatibility of the hydrogel sensor were investigated. These findings present a new strategy for the design of new-generation wearable devices with multiple functions.

A metalloporphyrin and hydantoin functionalized nanozyme with synergistically enhanced bacterial inhibition

An elaborate design of multimodal antibacterial agents has been revealed to be a promising strategy to address bacterial resistance, originating from the abuse of antibiotics. In this work, we have developed a positively charged and porous material, FePPOP_Hydantoin, as a disinfectant via introducing 1,3-dibromo-5,5-dimethylhydantoin (Hydantoin) and porphyrin iron units into a polymer framework. The extended π conjugated networks of FePPOP_Hydantoin endowed the material with strong near-infrared (NIR) absorption, high density of surface catalytic active centers, superior stability, and reproducibility. FePPOP_Hydantoin exhibits high peroxidase mimetic and photo-Fenton activity, which can catalyze the biologically allowable maximum concentrations of hydrogen peroxide (100 μM) to produce a vast amount of hydroxyl radicals. Simultaneously, the effective electrostatic interaction between the positively charged FePPOP_Hydantoin and the negatively charged bacteria facilitates the binding of FePPOP_Hydantoin on the bacterial membrane, restricting bacteria within the destruction range of hydroxyl radicals and thus making the bacteria more vulnerable. Finally, further close contact between bacteria and Hydantoin units in FePPOP_Hydantoin gave the material an antibacterial efficiency of over 99.999%. Compared with chemical therapy, photo-Fenton therapy, or peroxidase catalytic therapy alone, FePPOP_Hydantoin had a noteworthy multi-amplified antibacterial efficiency. Furthermore, FePPOP_Hydantoin exhibited good biocompatibility and negligible cytotoxicity. The in vivo antibacterial therapy on the Staphylococcus aureus (S. aureus) infected mouse wound model clearly proved the effectiveness of FePPOP_Hydantoin for fighting bacterial infections. This work highlights opportunities for the design of nanozymes with enhanced bacteriostatic activity, providing a new avenue for the construction of novel antibiotics.

Development of biaromatic core-linked antimicrobial peptide mimics: Substituent position significantly affects antibacterial activity and hemolytic toxicity

The development of bacterial resistance to the majority of clinically significant antimicrobials has made it more difficult to treat bacterial infections with conventional antibiotics. As part of ongoing research on antimicrobial peptide mimetics, a series of quaternary ammonium cationic compounds with various linkers were designed and synthesized, with some demonstrating high antibacterial activity against Gram-negative and Gram-positive bacteria. The structure-activity relationship study revealed that the spatial position of substituents had a significant impact on antibacterial activity and hemolytic toxicity. The best compound, 3e, has good antibacterial activity against Staphylococcus aureus [minimum inhibitory concentration (MIC = 1 μg/mL)] and the least hemolytic toxicity [hemolytic concentration (HC₅₀ = 905 μg/mL)], is stable in mammalian body fluids, and rarely induces bacterial resistance. The mechanism study revealed that the membrane action mode may be its potential bactericidal mechanism, and it can effectively cause the accumulation of intracellular reactive oxygen species (ROS) for killing bacteria. Importantly, 3e can effectively reduce the load of methicillin-resistant Staphylococcus aureus (MRSA) in mouse skin and has a higher in vivo bactericidal efficiency than vancomycin. These findings highlight the significance of divergent linkers in quaternary ammonium cations as antimicrobial peptide mimics and the potential of these cations to treat bacterial infections.

Switching from membrane disrupting to membrane crossing, an effective strategy in designing antibacterial polypeptide

Drug-resistant bacterial infections have caused serious threats to human health and call for effective antibacterial agents that have low propensity to induce antimicrobial resistance. Host defense peptide-mimicking peptides are actively explored, among which poly-β-l-lysine displays potent antibacterial activity but high cytotoxicity due to the helical structure and strong membrane disruption effect. Here, we report an effective strategy to optimize antimicrobial peptides by switching membrane disrupting to membrane penetrating and intracellular targeting by breaking the helical structure using racemic residues. Introducing β-homo-glycine into poly-β-lysine effectively reduces the toxicity of resulting poly-β-peptides and affords the optimal poly-β-peptide, βLys₅₀HG₅₀, which shows potent antibacterial activity against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and MRSA persister cells, excellent biosafety, no antimicrobial resistance, and strong therapeutic potential in both local and systemic MRSA infections. The optimal poly-β-peptide demonstrates strong therapeutic potential and implies the success of our approach as a generalizable strategy in designing promising antibacterial polypeptides.

Recent advances in bio-inspired ionic liquid-based interfacial materials from preparation to application

Natural creatures always display unique and charming functions, such as the adhesion of mussels and the lubrication of Nepenthes, to maintain their life activities. Bio-inspired interfacial materials infused with liquid, especially for ionic liquids (ILs), have been designed and prepared to meet the emerging and rising needs of human beings. In this review, we first summarize the recent development of bio-inspired IL-based interfacial materials (BILIMs), ranging from the synthesis strategy to the design principle. Then, we discuss the advanced applications of BILIMs from anti-adhesive aspects (e.g., anti-biofouling, anti-liquid fouling, and anti-solid fouling) to adhesive aspects (e.g., biological sensor, adhesive tape, and wound dressing). Finally, the current limitations and future prospects of BILIMs are provided to feed the actual needs.

Biomimetic electrodynamic nanoparticles comprising ginger-derived extracellular vesicles for synergistic anti-infective therapy

Nanotechnology enlightens promising antibacterial strategies while the complex in vivo infection environment poses a great challenge to the rational design of nanoplatforms for safe and effective anti-infective therapy. Herein, a biomimetic nanoplatform (EV-Pd-Pt) integrating electrodynamic Pd-Pt nanosheets and natural ginger-derived extracellular vesicles (EVs) is proposed. The introduction of ginger-derived EVs greatly endows EV-Pd-Pt with prolonged blood circulation without immune clearance, as well as accumulation at infection sites. More interestingly, EV-Pd-Pt can enter the interior of bacteria in an EV lipid-dependent manner. At the same time, reactive oxygen species are sustainably generated in situ to overcome the limitations of their short lifetime and diffusion distance. Notably, EV-Pd-Pt nanoparticle-mediated electrodynamic and photothermal therapy exhibit synergistic effects. Furthermore, the desirable biocompatibility and biosafety of the proposed nanoplatform guarantee the feasibility of in vivo applications. This proof-of-concept work holds significant promise for developing biomimetic nanoparticles by exploiting their intrinsic properties for synergistic anti-infective therapy.

ε-Polylysine-Based Macromolecules with Catalase-Like Activity to Accelerate Wound Healing by Clearing Bacteria and Attenuating Inflammatory Response

Wound healing has remained a critical challenge due to its susceptibility to bacterial infection and the unique biological inflammatory response. Safe and effective therapeutics are still lacking. Biodegradable macromolecules (ε-polylysine-g-ferrocene, EPL-g-Fc) were developed to accelerate wound healing by combating bacterial infection and attenuating inflammatory responses. The biodegradable macromolecules were prepared via a Schiff-based reaction between ferrocene carboxaldehyde (Fc) and ε-polylysine (EPL). Through the synergistic combination of positive-charged EPL and π-π stacked Fc, the macromolecules possess excellent antibacterial activities. EPL-g-Fc with catalase-like activity could modulate the oxidative microenvironment in mammalian cells and zebrafish by catalyzing H₂O₂ into H₂O and O₂. EPL-g-Fc could alleviate inflammatory response in vitro. Furthermore, the macromolecules could accelerate bacteria-infected wound healing in vivo. This work provides a versatile strategy for repairing bacteria-infected wounds by eliminating bacteria, modulating oxidative microenvironment, and alleviating inflammatory response.

pH-Responsive Hyperbranched Polymer Nanoparticles to Combat Intracellular Infection by Disrupting Bacterial Wall and Regulating Macrophage Polarization

Intracellular bacterial infections pose a serious threat to public health. Macrophages are a heterogeneous population of immune cells that play a vital role in intracellular bacterial infection. However, bacteria that survive inside macrophages could subvert the cell signaling and eventually reduce the antimicrobial activity of macrophages. Herein, dual pH-responsive polymer (poly[(3-phenylprop-2-ene-1,1-diyl)bis(oxy)bis(enthane-2,1-diyl)diacrylate-co-N-aminoethylpiperazine] (PCA)) nanoparticles were developed to clear intracellular bacteria by activating macrophages and destructing bacterial walls. The presence of acid-labile acetal linkages and tertiary amine groups in the polymer's backbone endow hyperbranched PCA dual pH-response activity that shows acid-induced positive charge increase and cinnamaldehyde release properties. The biodegraded PCA nanoparticles could significantly inhibit the growth of bacteria by damaging the bacterial walls. Meanwhile, PCA nanoparticles could uptake by macrophages, generate reactive oxygen species (ROS), and remodel the immune response by upregulating M1 polarization, leading to the reinforced antimicrobial capacity. Furthermore, PCA nanoparticles could promote bacteria-infected wound healing in vivo. Therefore, these dual pH-responsive PCA nanoparticles enabling bacteria-killing and macrophage activation provide a novel outlook for treating intracellular infection.

N-Arylimidazoliums as Highly Selective Biomimetic Antimicrobial Agents

Antibiotic resistance has become one of the greatest health threats in the world. In this study, a charge-dispersed dimerization strategy is described for the antimicrobial peptide (AMP) mimics via a tunable cationic charge to improve the selectivity between prokaryotic microbes and eukaryotic cells. This strategy is demonstrated with a series of charge-dispersed AMP mimics based on N-arylimidazolium skeletons. These N-arylimidazolium AMP mimics show potent antibacterial activity against strains along with a low rate of drug resistance, good hemocompatibility, and low cytotoxicity. In addition to the elimination of planktonic bacteria, N-arylimidazolium AMP mimics can also inhibit biofilm formation and destroy the established biofilm. More importantly, methicillin-resistant Staphylococcus aureus (MRSA)-induced lung-infected mice can be effectively treated by the intravenous administration of N-arylimidazolium AMP mimic, which enable the design of N-arylimidazolium AMP mimics to offer an alternative avenue to eradicate drug-resistant bacterial infection.

Ionic Liquids: Emerging Antimicrobial Agents

Antimicrobial resistance has become a serious threat to global health. New antimicrobials are thus urgently needed. Ionic liquids (ILs), salts consisting of organic cations and anions with melting points less than 100°C, have been recently found to be promising in antimicrobial field as they may disrupt the bacterial wall and membrane and consequently lead to cell leakage and death. Different types of antimicrobial ILs are introduced in the review, including cationic, polymeric, and anionic ILs. Being the main type of the antimicrobial ILs, the review focuses on the structure and the antimicrobial mechanisms of cationic ILs. The quantitative structure-activity relationship (QSAR) models of the cationic ILs are also included. Increase in alkyl chain length and lipophilicity is beneficial to increase the antimicrobial effects of cationic ILs. Polymeric ILs are homopolymers of monomer ILs or copolymers of ILs and other monomers. They have great potential in the field of antibiotics as they provide stronger antimicrobial effects than the sum of the monomer ILs. Anionic ILs are composed of existing anionic antibiotics and organic cations, being capable to enhance the solubility and bioavailability of the original form. Nonetheless, the medical application of antimicrobial ILs is limited by the toxicity. The structural optimization aided by QSAR model and combination with existing antibiotics may provide a solution to this problem and expand the application range of ILs in antimicrobial field.

Supramolecular Hydrogel Based on Pseudopolyrotaxanes Aggregation for Bacterial Microenvironment-Responsive Antibiotic Delivery

Due to the extensive use of antibiotics, the variety and number of drug-resistant pathogens have increased dramatically and have become a major global health problem. This imposes significant demands on the rational and effective use of antibiotics. To this end, a supramolecular hydrogel based on pseudopolyrotaxanes aggregation is proposed for antibiotic delivery. Supramolecular cross-linking strategies allow hydrogels to be obtained under mild conditions that facilitate the encapsulation of antibiotics. The presence of pH-sensitive imine bonds allows for the reversible detachment of PEG residues from the PEGylated hyaluronic acid backbone in an acidic environment, which leads to reversible changes in hydrogel crosslink density and thus controls antibiotic release behavior. Antimicrobial assessments indicated that the hydrogel exhibited good antimicrobial efficiency against both Gram-positive and negative bacteria, while responding to the bacterial microenvironment and enabling a burst release of antibiotics in severe infections. The proposed hydrogel also has excellent biocompatibility and thus possesses great potential for biomedical applications.

Pressure-sensitive antibacterial hydrogel dressing for wound monitoring in bed ridden patients

Pressure ulcer is a common chronic injury in the bedridden population. The wound is easily subjected to secondary pressure injury due to the inconvenient mobility of patients, which greatly prolongs the hospital stay of patients and is highly prone to wound infection or other complications. It is urgent to develop a multifunctional wound dressing with pressure sensing, real-time monitoring, and wound therapy to overcome the secondary pressure injury during treatment. Here, a polyvinyl alcohol/acrylamide-ionic liquid hydrogel dressing is designed based on the antibacterial property and electrical conductivity of imidazolidine ionic liquids. Compared with existing pressure-sensing hydrogels, the hydrogel exhibits extremely high pressure sensitivity (9.19 kPa^-1). Meanwhile, the good real-time responsiveness, stable signal output as well as excellent mechanical properties enable the hydrogel to monitor human movement on a large scale, and transmit the pressure status of patient wounds to nursing staff in a timely manner to avoid secondary pressure injuries. In addition, this hydrogel dressing exhibits a wide range of antibacterial activities against Gram-negative and Gram-positive bacteria as well as fungi, and has a significant therapeutic effect on full-thickness skin wounds by inhibiting wound infection, rapidly eradicating inflammation, promoting proliferation and tissue remodeling. This multifunctional hydrogel dressing opens a therapeutic and regulatory two-pronged strategy avenue through chronic wound management and pressure sensing monitoring.

An Optimally Designed Engineering Exosome-Reductive COF Integrated Nanoagent for Synergistically Enhanced Diabetic Fester Wound Healing

Oxidative stress and local overactive inflammation have been considered major obstacles in diabetic wound treatment. Although antiphlogistic tactics have been reported widely, they are also challenged by pathogen contamination and compromised angiogenesis. Herein, a versatile integrated nanoagent based on 2D reductive covalent organic frameworks coated with antibacterial immuno-engineered exosome (PCOF@E-Exo) is reported to achieve efficient and comprehensive combination therapy for diabetic wounds. The E-Exo is collected from TNF-α-treated mesenchymal stem cells (MSCs) under hypoxia and encapsulated cationic antimicrobial carbon dots (CDs). This integrated nanoagent not only significantly scavenges reactive oxygen species and induces anti-inflammatory M2 macrophage polarization, but also stabilizes hypoxia-inducible factor-1α (HIF-1α). More importantly, the PCOF@E-Exo exhibits intriguing bactericide capabilities toward Gram-negative, Gram-positive, and drug-resistant bacteria, showing favorable intracellular bacterial destruction and biofilm permeation. In vivo results demonstrate that the synergetic impact of suppressing oxidative injury and tissue inflammation, promoting angiogenesis and eradicating bacterial infection, could significantly accelerate the infected diabetic fester wound healing with better therapeutic benefits than monotherapy or individual antibiotics. The proposed strategy can inspire further research to design more delicate platforms using the combination of immunotherapy with other therapeutic methods for more efficient ulcerated diabetic wounds treatments.

Enhanced photocatalytic and antibacterial activity of acridinium-grafted g-C3N4 with broad-spectrum light absorption for antimicrobial photocatalytic therapy

As a metal-free polymeric photocatalyst, graphitic carbon nitride (g-C₃N₄) has attracted great attention owing to its high stability and low toxicity. However, g-C₃N₄ suffers from low light harvesting ability which limits its applications in antimicrobial photocatalytic therapy (APCT). Herein, acridinium (ADN)-grafted g-C₃N₄ (ADN@g-C₃N₄) nanosheets are prepared via covalent grafting of ADN to g-C₃N₄. The obtained ADN@g-C₃N₄ exhibits a narrow optical band gap (2.12 eV) and a wide optical absorption spectrum (intensity a.u. > 0.30) ranging from ultraviolet to near-infrared region. Moreover, ADN@g-C₃N₄ would produce reactive oxygen species (ROS) under light irradiation to exert effective sterilization and biofilm elimination activities against both gram-negative and gram-positive bacteria. Molecular dynamics simulation reveals that the ADN@g-C₃N₄ may move toward, tile and insert the bacterial lipid bilayer membrane through strong van der Waals and electrostatic interaction, decreasing the order parameter of the lipid while increasing the conducive of ROS migration, inducing ADN@g-C₃N₄ with improved antimicrobial and antibiofilm performance. Moreover, ADN@g-C₃N₄ could efficiently eradicate oral biofilm on artificial teeth surfaces. This work may provide a broad-spectrum light-induced photocatalytic therapy for preventing and treating dental plaque diseases and artificial teeth-related infections, showing potential applications for intractable biofilm treatment applications. An acridinium-grafted g-C₃N₄ (ADN@g-C₃N₄) with a narrow band gap and broad-spectrum light absorption was synthesized. The narrow optical band gap and improved electrostatic interaction with bacterial lipid bilayer membrane of ADN@g-C₃N₄ strengthened the ROS generation and facilitated the diffusion of ROS to bacteria surface, leading to enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation. STATEMENT OF SIGNIFICANCE: An acridinium-grafted g-C₃N₄ (ADN@g-C₃N₄) with a narrow band gap and broad-spectrum light absorption was developed as an antimicrobial photocatalytic therapy agent. The ADN@g-C₃N₄ exhibited enhanced photocatalytic and antibacterial activity against bacteria and corresponding biofilm under light irradiation, showing potential applications for intractable biofilm treatment.

Cyclic topology enhances the killing activity of polycations against planktonic and biofilm bacteria

Bacterial biofilms, as a fortress to protect bacteria, enhance resistance to antibiotics because of their limited penetration, which has become a major threat to current anti-infective therapy. Antimicrobial polycations have received wide attention to kill planktonic bacteria because of their unique antimicrobial mechanism without drug resistance but it is still hard to kill the bacteria in the deep of the biofilm. Unlike linear polymers, the cyclic topology has been demonstrated with enhanced penetration in tissues, which is attributed to the lack of end groups, constrained conformation and a smaller hydrodynamic volume, opening a new sight of polycations in the antibacterial application against biofilms. Here, polycations with different topologies including linear and cyclic polycations were synthesized and their killing activity against planktonic and biofilm bacteria was studied. The experimental results showed the enhanced antibacterial activity of cyclic polycations for planktonic bacteria, which is presumably attributed to their smaller hydrodynamic volume, higher local density of positive charge and more interactions between cation units and the bacterial membrane than their linear analogues. Besides, cyclic polycations exhibit enhanced killing effect for biofilm bacteria and inhibition effect for biofilms with 5-7 times and 2-3 times enhancements than the linear polycations, respectively. Furthermore, an Escherichia coli infection model on mice was established and the therapeutic effects of cyclic and linear polycations were evaluated. Compared with the linear polycations, the cyclic polycations exhibited enhanced antibacterial activity with an ∼4 times increase, promoting the healing of the infected wounds. This work provides a new perspective in the development of antimicrobial polycations, which are promising therapeutic agents to kill planktonic and biofilm bacteria without drug resistance.

Secondary Ammonium-Based Hyperbranched Poly(amidoamine) with Excellent Membrane-Active Property for Multidrug-Resistant Bacterial Infection

With the rapid emergence of microbial infections induced by "superbugs", public health and the global economy are threatened by the lack of effective and biocompatible antibacterial agents. Herein, we systematically design a series of secondary ammonium-based hyperbranched poly(amidoamine) (SAHBP) with different alkyl chain lengths for probing high-efficacy antibacterial agents. SAHBP modified with alkyl tails at the hyperbranched core could efficiently kill Escherichia coli and Staphylococcus aureus, two types of clinically important bacteria worldwide. The best SAHBP with 12-carbon-long alkyl tails (SAHBP-12) also showed high activity against problematic multidrug-resistant bacteria, including Pseudomonas aeruginosa and methicillin-resistant S. aureus (MRSA). Based on ζ potential, isothermal titration microcalorimetry (ITC), and membrane integrity assays, it is found that SAHBP-12 could attach to the cell membrane via electrostatic adsorption and hydrophobic interactions, following which the integrity of the bacterial cell wall and the cell membrane is disrupted, resulting in severe cell membrane damage and the leakage of cytoplasmic contents, finally causing bacterial cell death. Impressively, benefiting from excellent membrane-active property, SAHBP-12 exhibited robust therapeutic efficacy in MRSA-infected mice wounds. Moreover, SAHBP-12 also showed excellent biosafety in vitro and in vivo, which undoubtedly distinguished it as a potent weapon in combating the growing threat of problematic multidrug-resistant bacterial infections.