Surfactin-Conjugated Silver Nanoparticles as an Antibacterial and Antibiofilm Agent against Pseudomonas aeruginosa

Phenylboronic Acid-Modified Polyethyleneimine: A Glycan-Targeting Anti-Biofilm Polymer for Inhibiting Bacterial Adhesion to Mucin and Enhancing Antibiotic Efficacy

Bacterial biofilms present significant therapeutic challenges due to their resistance to conventional antimicrobial treatment. Mucins typically serve as a protective barrier against pathogens, yet certain bacteria, such as Pseudomonas aeruginosa (P. aeruginosa), can exploit these glycoproteins as attachment sites for biofilm formation. This study introduces boronic acid-functionalized polyethyleneimine (PEI-BA) as a promising antibiofilm agent that effectively blocks bacterial adhesion to mucin-rich surfaces. Through the multivalent presentation of boronic acid groups, PEI-BA reversibly forms boronate ester bonds with mucin glycans, creating a protective barrier. Our findings show that PEI-BA prevents bacterial attachment through a nonbactericidal mechanism, potentially reducing the risk of resistance development. Notably, PEI-BA synergizes with a conventional antibiotic, tobramycin, significantly enhancing biofilm inhibition compared to either treatment alone. Systematic evaluation of PEI-BA formulations identified optimal functionalization levels, balancing glycan-binding capability with solubility. From a biomaterials design perspective, we demonstrate how rational polymer modification can transform a potent but cytotoxic antimicrobial agent (i.e., PEI) into a safe and effective antibiofilm material, opening further possibilities for managing biofilm-associated infections in clinical settings. This work establishes boronic acid-based nanomaterials as promising candidates for biofilm prevention and antibiotic enhancement, particularly in conditions like cystic fibrosis, where mucin-bacterial interactions contribute to disease progression.

Bio-Based Surfactants and Biosurfactants: An Overview and Main Characteristics

Natural surfactants are surface-active molecules synthesized from renewable resources (i.e., plants, animals, or microorganisms) and possess properties comparable to conventional surfactants, making them an environmentally friendly potential alternative to petrochemical surfactants. Additionally, they exhibit biological properties such as anti-microbial properties, biodegradability, and less toxicity, allowing their use in everyday products with minimal risk to human health and the environment. Based on their mode of production, natural surfactants can be classified into first-generation or bio-based surfactants and second-generation or biosurfactants, although their definition may vary depending on the author in the literature. This review offers an extensive classification of bio-based surfactants and biosurfactants, focusing on their composition, natural sources, production methods, and potential applications across various industries. Furthermore, the main challenges and future perspectives are discussed.

Facile On-Substrate Fabrication of Silver Coordination Polymer Nanowires for Sustainable and Efficient Water Disinfection

Silver, as the oldest antibacterial material, has been almost replaced by other alternatives for its insufficient activity or potential side-effects on the ecosystem due to the over-release of Ag ions (Ag+). Herein, a facile and general strategy is developed to on-substrate fabricate silver coordination polymer nanowire arrays (Ag CPN) by simply immersing Ag-containing substrates into cationic surfactant solution at room temperature. Such a Ag CPN not only provides high-surface-area nano-biointerfaces for destroying microorganisms via physicomechanical interactions but also acts as a safe Ag+ reservoir, steadily releasing Ag+ at a relatively high but safe level (∼40 ppb, but lower than the safe level of 100 ppb). Taking advantage of physicomechanical and chemical effects together, the on-substrate fabricated Ag CPN allows Ag substrates or Ag-coated disposable substrates for efficient and sustainable bacterial disinfection. As a demonstration, the modified silver net shows ∼100% antibacterial activity when the bacterial water with a 1.0 × 106 CFU mL-1 of E. coli flows through in 4.0 m3 h-1 m-2 fluxes. By coating a silver film onto a wide range of cheap or disposable substrates, the present strategy opens up opportunities for reviving ancient silver materials for affordable and recoverable antibacterial applications such as water disinfection.

Nanoparticle-Based Nitric Oxide Donors: Exploring Their Antimicrobial and Anti-Biofilm Capabilities

Background: Nitric oxide (NO) is an antimicrobial and anti-biofilm agent with significant potential for combating biofilm-associated infections and antibiotic resistance. However, owing to its high reactivity due to the possession of a free radical and short half-life (1-5 s), the practical application of NO in clinical settings is challenging. Objectives: This review explores the development of NO-releasing nanoparticles that provide a controlled, targeted delivery system for NO, enhancing its antimicrobial efficacy while minimizing toxicity. The review discusses various NO donors, nanoparticle platforms, and how NO disrupts biofilm formation and eradicates pathogens. Additionally, we examine the highly encouraging and inspiring results of NO-releasing nanoparticles against multidrug-resistant strains and their applications in medical and environmental contexts. This review highlights the promising role of NO-based nanotechnologies in overcoming the challenges posed by increasing antibiotic resistance and biofilm-associated infections. Conclusions: Although NO donors and nanoparticle delivery systems show great potential for antimicrobial and anti-biofilm uses, addressing challenges related to controlled release, toxicity, biofilm penetration, resistance, and clinical application is crucial.

Copper hydrogen phosphate nanosheets functionalized hydrogel with tissue adhesive, antibacterial, and angiogenic capabilities for tracheal mucosal regeneration

Timely and effective interventions after tracheal mucosal injury are lack in clinical practices, which elevate the risks of airway infection, tracheal cartilage deterioration, and even asphyxiated death. Herein, we proposed a biomaterial-based strategy for the repair of injured tracheal mucosal based on a copper hydrogen phosphate nanosheets (CuHP NSs) functionalized commercial hydrogel (polyethylene glycol disuccinimidyl succinate-human serum albumin, PH). Such CuHP/PH hydrogel achieved favorable injectability, stable gelation, and excellent adhesiveness within the tracheal lumen. Moreover, CuHP NSs within the CuHP/PH hydrogel effectively stimulate the proliferation and migration of endothelial/epithelial cells, enhancing angiogenesis and demonstrating excellent tissue regenerative potential. Additionally, it exhibited significant inhibitory effects on both bacteria and bacterial biofilms. More importantly, when injected injured site of tracheal mucosa under fiberoptic bronchoscopy guidance, our results demonstrated CuHP/PH hydrogel adhered tightly to the tracheal mucosa. The therapeutic effects of the CuHP/PH hydrogel were further confirmed, which significantly improved survival rates, vascular and mucosal regeneration, reduced occurrences of intraluminal infections, tracheal stenosis, and cartilage damage complications. This research presents an initial proposition outlining a strategy employing biomaterials to mitigate tracheal mucosal injury, offering novel perspectives on the treatment of mucosal injuries and other tracheal diseases.

Surface modification of medical grade biomaterials by using a low-temperature-processed dual functional Ag-TiO2 coating for preventing biofilm formation

Biofilm development in medical devices is considered the major virulence component that leads to increased mortality and morbidity among patients. Removing a biofilm once formed is challenging and frequently results in persistent infections. Many current antibiofilm coating strategies involve harsh conditions causing damage to the surface of the medical devices. To address the issue of bacterial attachment in medical devices, we propose a novel antibacterial surface modification approach. In this paper, we developed a novel low-temperature based solution-processed approach to deposit silver nanoparticles (Ag NPs) inside a titanium oxide (TiO2) matrix to obtain a Ag-TiO2 nanoparticle coating. The low temperature (120 °C)-based UV annealed drop cast method is novel and ensures no surface damage to the medical devices. Various medical-grade biomaterials were then coated using Ag-TiO2 to modify the surface of the materials. Several studies were performed to observe the antibacterial and antibiofilm properties of Ag-TiO2-coated medical devices and biomaterials. Moreover, the Ag-TiO2 NPs did not show any skin irritation in rats and showed biocompatibility in the chicken egg model. This study indicates that Ag-TiO2 coating has promising potential for healthcare applications to combat microbial infection and biofilm formation.

Screening of Lithium Substituted Ag-TiO2 Nanoparticle Coating for Antibiofilm Application

Bacterial infections and biofilm growth are common mishaps associated with medical devices, and they contribute significantly to ill health and mortality. Removal of bacterial deposition from these devices is a major challenge, resulting in an immediate necessity for developing antibacterial coatings on the surfaces of medical implants. In this context, we developed an innovative coating strategy that can operate at low temperatures (80 °C) and preserve the devices' integrity and functionality. An innovative Ag-TiO2 based coating was developed by ion exchange between silver nitrate (AgNO3) and lithium titanate (Li4Ti5O12) on glass substrates for different periods, ranging from 10 to 60 min. The differently coated samples were tested for their antibacterial and antibiofilm efficacy.

Multifunctional silver nanoparticle embedded eri silk cocoon scaffolds against burn wounds-associated infection

Antimicrobial wound dressings offer enhanced efficacy compared to conventional dressing platforms by limiting bacterial infections, expediting the healing process, and creating a barrier against additional wound contamination. The use of silk derived from silkworm cocoons in wound healing applications is attributed to its exceptional characteristics. Compared to mulberry silk, sericin from non-mulberry cocoons has higher water exchange mobility and moisture retention. Eri, a non-mulberry silkworm, is an unexplored source of silk with an eco-friendly nature of production where the natural life cycle of silkworms is not disrupted, and no moths are sacrificed. This work reports on an eri silk cocoon-based scaffold decorated with silver nanoparticles as a wound dressing material effective against burn-wound-associated multiple-drug-resistant bacteria. The UV-vis spectroscopy showed maximum absorbance at 448 nm due to the surface plasmon resonance of silver nanoparticles. FT-IR spectra exhibited the functional groups in the eri silk proteins accountable for the reduction of Ag+ to Ag0 in the scaffold. SEM-EDX analysis revealed the presence of elemental silver, and XRD analysis confirmed their particle size of 5.66-8.82 nm. The wound dressing platform showed excellent thermal stability and hydrophobicity, fulfilling the criteria of a standard waterproof dressing material, and anticipating the prevention of bacterial biofilm formation in chronic wounds. The scaffold was found to be effective against both Staphylococcus aureus (MTCC 87) and Pseudomonas aeruginosa (MTCC 1688) multiple-drug-resistant pathogens. Electron microscopy revealed the bacterial cell damage, suggesting its bactericidal property. The results further revealed that the scaffold was both hemocompatible and cytocompatible, suggesting its potential application in chronic wounds such as burns. As an outcome, this study presents a straightforward, cost-effective, and sustainable way of developing a multifunctional wound dressing platform, suggesting its significant therapeutic potential in clinical and biomedical sectors and facile commercialization.

Interplay between Bile Acids and Intestinal Microbiota: Regulatory Mechanisms and Therapeutic Potential for Infections

Bile acids (BAs) play a crucial role in the human body's defense against infections caused by bacteria, fungi, and viruses. BAs counteract infections not only through interactions with intestinal bacteria exhibiting bile salt hydrolase (BSH) activity but they also directly combat infections. Building upon our research group's previous discoveries highlighting the role of BAs in combating infections, we have initiated an in-depth investigation into the interactions between BAs and intestinal microbiota. Leveraging the existing literature, we offer a comprehensive analysis of the relationships between BAs and 16 key microbiota. This investigation encompasses bacteria (e.g., Clostridioides difficile (C. difficile), Staphylococcus aureus (S. aureus), Escherichia coli, Enterococcus, Pseudomonas aeruginosa, Mycobacterium tuberculosis (M. tuberculosis), Bacteroides, Clostridium scindens (C. scindens), Streptococcus thermophilus, Clostridium butyricum (C. butyricum), and lactic acid bacteria), fungi (e.g., Candida albicans (C. albicans) and Saccharomyces boulardii), and viruses (e.g., coronavirus SARS-CoV-2, influenza virus, and norovirus). Our research found that Bacteroides, C. scindens, Streptococcus thermophilus, Saccharomyces boulardii, C. butyricum, and lactic acid bacteria can regulate the metabolism and function of BSHs and 7α-dehydroxylase. BSHs and 7α-dehydroxylase play crucial roles in the conversion of primary bile acid (PBA) to secondary bile acid (SBA). It is important to note that PBAs generally promote infections, while SBAs often exhibit distinct anti-infection roles. In the antimicrobial action of BAs, SBAs demonstrate antagonistic properties against a wide range of microbiota, with the exception of norovirus. Given the intricate interplay between BAs and intestinal microbiota, and their regulatory effects on infections, we assert that BAs hold significant potential as a novel approach for preventing and treating microbial infections.

Recent progress in hydrogels combined with phototherapy for bacterial infection: A review

Phototherapy has become one of the most effective antibacterial methods due to its associated lack of drug resistance and its good antibacterial effect. For the purpose of avoiding the aggregation and premature release of photosensitive/photothermal agents during phototherapy, they can be mixed into three-dimensional hydrogels. The combination of hydrogels and phototherapy combines the merits of both hydrogels and phototherapy, overcomes the disadvantages of traditional antibacterial methodologies, and has broad application prospects. This review presents recent advancements in phototherapeutic antibacterial hydrogels including photodynamic antibacterial hydrogels, photothermal antibacterial hydrogels, photodynamic and photothermal synergistic antibacterial hydrogels, and other synergistic antibacterial hydrogels involving phototherapy.

A highly stable electrochemical sensor with antifouling and antibacterial capabilities for mercury ion detection in seawater

The monitoring of heavy metal ions in ocean is crucial for environment protection and assessment of seawater quality. However, the detection of heavy metal ions in seawater with electrochemical sensors, especially for long-term monitoring, always faces challenges due to marine biofouling caused by the nonspecific adsorption of microbial and biomolecules. Herein, an electrochemical aptasensor, integrating both antifouling and antibacterial properties, was developed for the detection of Hg2+ in the ocean. In this electrochemical aptasensor, eco-friendly peptides with superior hydrophilicity served as anti-biofouling materials, preventing nonspecific adsorption on the sensing interface, while silver nanoparticles were employed to eliminate bacteria. Subsequently, a ferrocene-modified aptamer was employed for the specific recognition of Hg2+, leveraging the aptamer's ability to fold into a thymine-Hg2+-thymine (T-Hg2+-T) structure upon interaction, and bringing ferrocene nearer to the sensor surface, significantly amplifying the electrochemical response. The prepared electrochemical aptasensor significantly reduced the nonspecific adsorption in seawater while maintaining sensitive electrochemical response. Furthermore, the biosensor exhibited a linear response range of 0.01-100 nM with a detection limit of 2.30 pM, and realized the accurate monitoring of mercury ions in real marine environment. The research results offer new insights into the preparation of marine antifouling sensing devices, and it is expected that sensors with antifouling and antimicrobial capabilities will find broad applications in the monitoring of marine pollutants.

Aggregation-Induced Emission Photosensitizer with Ag(I)-π Interaction-Enhanced Reactive Oxygen Species for Eliminating Multidrug Resistant Bacteria

Multidrug-resistant (MDR) bacteria pose serious threats to public health due to the lack of effective and biocompatible drugs to kill MDR bacteria. Photodynamic antibacterial therapy has been widely studied due to its low induction of resistance. However, photosensitizers that can efficiently generate reactive oxygen species (ROS) through both type I and type II mechanisms and that have the capability of multiple modes of action are rarely reported. Addressing this issue, we developed a near-infrared-emitting triphenylamine indole iodoethane (TTII) and its silver(I) self-assembled (TTIIS) aggregation-induced emission (AIE) photosensitizer for multimode bacterial infection therapy. TTII can efficiently produce both Type I ROS •OH and Type II ROS 1O2. Interestingly, the Ag(I)-π interaction contributed in TTIIS efficiency promotion of the generation of 1O2. Moreover, by releasing Ag+, TTIIS enabled photodynamic-Ag(I) dual-mode sterilization. As a result, TTIIS achieved an effective enhancement of antibacterial activity, with a 1-2-fold boost against multidrug-resistant Escherichia coli (MDR E. coli). Both TTII and TTIIS at a concentration as low as 0.55 μg mL-1 can kill more than 98% of methicillin resistant Staphylococcus aureus (MRSA) on MRSA-infected full-thickness defect wounds of a mouse, and both TTII and TTIIS were effective in eliminating the bacteria and promoting wound healing.

Highly Cytocompatible Polylactic Acid Based Electrospun Microfibers Loaded with Silver Nanoparticles Generated onto Chestnut Shell Lignin for Targeted Antibacterial Activity and Antioxidant Action

Electrospun (e-spun) fibers are generally regarded as powerful tools for cell growth in tissue regeneration applications, and the possibility of imparting functional properties to these materials represents an increasingly pursued goal. We report herein the preparation of hybrid materials in which an e-spun d,l-polylactic acid matrix, to which chitosan or crystalline nanocellulose was added to improve hydrophilicity, was loaded with different amounts of silver(0) nanoparticles (AgNP) generated onto chestnut shell lignin (CSL) (AgNP@CSL). A solvent-free mechanochemical method was used for efficient (85% of the theoretical value by XRD analysis) Ag(0) production from the reduction of AgNO3 by lignin. For comparison, e-spun fibers containing CSL alone were also prepared. SEM and TEM analyses confirmed the presence of AgNP@CSL (average size 30 nm) on the fibers. Different chemical assays indicated that the AgNP@CSL containing fibers exhibited marked antioxidant properties (EC50 1.6 ± 0.1 mg/mL, DPPH assay), although they were halved with respect to those of the CSL containing fibers, as expected because of the efficient silver ion reduction. All the fibers showed high cytocompatibility toward human mesenchymal stem cells (hMSCs) representative of the self-healing process, and their antibacterial properties were tested against the pathogens Escherichia coli (E. coli), Staphylococcus epidermidis, and Pseudomonas aeruginosa. Finally, competitive surface colonization as simulated by cocultures of hMSC and E. coli showed that AgNP@CSL loaded fibers offered the cells a targeted protection from infection, thus well balancing cytocompatibility and antibacterial properties.

Bactericidal Effect and Cytotoxicity of Graphene Oxide/Silver Nanocomposites

To tackle the proliferation of pathogenic microorganisms without relying on antibiotics, innovative materials boasting antimicrobial properties have been engineered. This study focuses on the development of graphene oxide/silver (GO/Ag) nanocomposites, derived from partially reduced graphene oxide adorned with silver nanoparticles. Various nanocomposites with different amounts of silver (GO/Ag-1, GO/Ag-2, GO/Ag-3, and GO/Ag-4) were synthesized, and their antibacterial efficacy was systematically studied. The silver nanoparticles were uniformly deposited on the partially reduced graphene oxide surface, exhibiting spherical morphologies with an average size of 25 nm. The nanocomposites displayed potent antibacterial properties against both gram-positive bacteria (S. aureus and B. subtilis) and gram-negative bacteria (E. coli and S. enterica) as confirmed by minimum inhibition concentration (MIC) studies and time-dependent experiments. The optimal MIC for Gram-positive bacteria was 62.5 μg/mL and for Gram-negative bacteria was 125 μg/mL for the GO/Ag nanocomposites. Bacterial cells that encountered the nanocomposite films exhibited significantly greater inhibitory effects compared to those exposed to conventional antibacterial materials. Furthermore, the cytotoxicity of these nanocomposites was assessed using human epithelial cells (HEC), revealing that GO/Ag-1 and GO/Ag-2 exhibited lower toxicity levels toward HEC and remained compatible even at higher dilution rates. This study underscores the potential of GO/Ag-based nanocomposites as versatile materials for antibacterial applications, particularly as biocompatible wound dressings, offering promising prospects for wound healing and infection control.

Surfactin and Capric Acid Affect the Posaconazole Susceptibility of Candida albicans Strains with Altered Sterols and Sphingolipids Biosynthesis

Infections caused by Candida spp. pose a continuing challenge for modern medicine, due to widespread resistance to commonly used antifungal agents (e.g., azoles). Thus, there is considerable interest in discovering new, natural compounds that can be used in combination therapy with conventional antibiotics. Here, we investigate whether the natural compounds surfactin and capric acid, in combination with posaconazole, enhance the growth inhibition of C. albicans strains with alterations in sterols and the sphingolipids biosynthesis pathway. We demonstrate that combinations of posaconazole with surfactin or capric acid correspond with the decreased growth of C. albicans strains. Moreover, surfactin and capric acid can independently contribute to the reduced adhesion of C. albicans strains with altered ergosterol biosynthesis to abiotic surfaces (up to 90% reduction in adhesion). A microscopic study of the C. albicans plasma membrane revealed that combinations of those compounds do not correspond with the increased permeabilization of the plasma membrane when compared to cells treated with posaconazole alone. This suggests that the fungistatic effect of posaconazole in combination with surfactin or capric acid is related to the reduction in adhesion of C. albicans.