Reducing Bacterial Infections and Biofilm Formation Using Nanoparticles and Nanostructured Antibacterial Surfaces

Biomimetic green synthesis of ZnO nanoflowers using α-amylase: from antimicrobial to toxicological evaluation

Biologically mediated synthesis of nanomaterials has emerged as an ecologically benign and biocompatible approach. Our study explores enzymatic synthesis, utilizing α-amylase to synthesize ZnO nanoflowers (ZnO-NFs). X-ray diffraction and energy-dispersive X-ray spectroscopy revealed crystal structure and elemental composition. Dynamic light scattering analysis indicates that ZnO-NFs possess a size of 101 nm. Transmission electron microscopy showed a star-shaped morphology of ZnO-NFs with petal-like structures. ZnO-NFs exhibit potent photocatalytic properties, degrading 90% eosin, 87% methylene blue, and 81% reactive red dyes under UV light, with kinetics fitting the Langmuir-Hinshelwood pseudo-first-order rate law. The impact of pH and interfering substances on dye degradation was explored. ZnO-NFs display efficient bacteriocidal activity against different Gram-positive and negative strains, antibiofilm potential (especially with P. aeruginosa), and hemocompatibility up to 600 ppm, suggesting versatile potential in healthcare and environmental remediation applications.

From bench to bedside: Platelet biomimetic nanoparticles as a promising carriers for personalized drug delivery

In recent decades, there has been a burgeoning interest in cell membrane coating strategies as innovative approach for targeted delivery systems in biomedical applications. Platelet membrane-coated nanoparticles (PNPs), in particular, are gaining interest as a new route for targeted therapy due to their advantages over conventional drug therapies. Their stepwise approach blends the capabilities of the natural platelet membrane (PM) with the adaptable nature of manufactured nanomaterials, resulting in a synergistic combination that enhances drug delivery and enables the development of innovative therapeutics. In this context, we present an overview of the latest advancements in designing PNPs with various structures tailored for precise drug delivery. Initially, we describe the types, preparation methods, delivery mechanisms, and specific advantages of PNPs. Next, we focus on three critical applications of PNPs in diseases: vascular disease therapy, cancer treatment, and management of infectious diseases. This review presents our knowledge of PNPs, summarizes their advancements in targeted therapies and discusses the promising potential for clinical translation of PNPs.

Nanotopology-Enabled On-Site Pathogen Detection for Managing Atopic Dermatitis

Atopic dermatitis (AD), a prevalent skin condition often complicated by microbial infection, poses a significant challenge in identifying the responsible pathogen for its effective management. However, a reliable, safe tool for pinpointing the source of these infections remains elusive. In this study, a novel on-site pathogen detection that combines chemically functionalized nanotopology with genetic analysis is proposed to capture and analyze pathogens closely associated with severe atopic dermatitis. The chemically functionalized nanotopology features a 3D hierarchical nanopillar array (HNA) with a functional polymer coating, tailored to isolate target pathogens from infected skin. This innovative nanotopology demonstrates superior pathogenic capture efficiency, favorable entrapment patterns, and non-cytotoxicity. An HNA-assembled stick is utilized to directly retrieve bacteria from infected skin samples, followed by extraction-free quantitative loop-mediated isothermal amplification (direct qLAMP) for validation. To mimic human skin conditions, porcine skin is employed to successfully capture Staphylococcus aureus, a common bacterium exacerbating AD cases. The on-site detection method exhibits an impressive detection limit of 103 cells mL-1. The HNA-assembled stick represents a promising tool for on-site detection of bacteria associated with atopic dermatitis. This innovative approach enables to deepen the understanding of AD pathogenesis and open avenues for more effective management strategies for chronic skin conditions.

On the antimicrobial properties and endurance of eugenol and 2-phenylphenol functionalized sol-gel coatings

Preventing microbiological surface contamination in public spaces is nowadays of high priority. The proliferation of a microbial infection may arise through air, water, or direct contact with infected surfaces. Chemical sanitization is one of the most effective approaches to avoid the proliferation of microorganisms. However, extended contact with chemicals for cleaning purposes such as chlorine, hydrogen peroxide or ethanol may lead to long-term diseases as well as drowsiness or respiratory issues, not to mention environmental issues associated to their use. As a potentially safer alternative, in the present work, the efficacy and endurance of the antimicrobial activity of different sol-gel coatings were studied, where one or two biocides were added to the coating matrix resulting on active groups exposed on the surface. Specifically, the coating formulations were synthesized by the sol-gel method. Using the alkoxide route with acid catalysis a hybrid silica-titania-methacrylate matrix was obtained where aromatic liquid eugenol was added with a double function: as a complexing agent for the chelation of the reaction precursor titanium isopropoxide, and as a biocide. In addition, 2-Phenylphenol, ECHA approved biocide, has also been incorporated to the coating matrix. The antibacterial effect of these coatings was confirmed on Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). Additionally, the coatings were non cyto-toxic and displayed virucidal activity. The coating chemical composition was characterized by 29Si NMR, and ATR-FTIR. Furthermore, the thickness and the mechanical properties were characterized by profilometry and nanoindentation, respectively. Finally, the durability of the coatings was studied with tribology tests. Overall, our data support the efficacy of the tested sol-gel coatings and suggest that added features may be required to improve endurance of the antimicrobial effects on operational conditions.

Carbon nanoparticles neutralize carbon dioxide (CO2) in cytotoxicity: Potent carbon emission induced resistance to anticancer nanomedicine and antibiotics

Excessive carbon emissions, especially CO2 release, have been a global concern. Few studies applied nanotechnology to relieve the ecotoxicity of CO2. Here, we applied carbon dots (CDs) to neutralize the CO2. We found CO2 induced the aggregation of CDs, which is of significance for CDs in enhanced fluorescence intensity but decreased CDs function in nanozyme activity, and reduced CDs toxicity to bacteria and cancer cells. Our data suggest the concern of CO2 release in global health in CDs mediated anticancer drug delivery and antibiotics resistance. However, enhanced fluorescence in cells which can be applied for bioimaging or CO2 sensing as simulated investigation by static charged attraction of positively charged CDs with negatively charged soluble HCO3-. Thus, CO2 abrogates the nanomedicine efficacy in cancer cells and antibacterial and may induce drug resistance for patients undergoing chemotherapy or antibiotics therapy. To overcome the resistance, we may apply the CDs for a neutralization of CO2 for impact on anticancer nanomedicine and antibiotics and reducing the ecotoxicity in biological systems.

The role of water matrix on antibiotic resistance genes transmission in substrate layer from stormwater bioretention cells

Recently, extensive attention has been paid to antibiotic resistance genes (ARGs) transmission. However, little available literature could be found about ARGs transmission in stormwater bioretention cells, especially the role of water matrix on ARGs transmission. Batch experiments were conducted to investigate target ARGs (blaTEM, tetR and aphA) transmission behaviors in substrate layer from stormwater bioretention cells under different water matrices, including nutrient elements (e.g., carbon, nitrogen and phosphorus), water environmental conditions (dissolved oxygen (DO), pH and salinity, etc.) and pollution factors (like heavy metals, antibiotics and disinfectants), showing that ARGs conjugation frequency increased sharply with the enhancement of water matrices (expect DO and pH), while there were obvious increasing tendencies for all ARGs transformation frequencies under only the pollution factor. The correlation between dominant bacteria and ARGs transmission implied that conjugation and transformation of ARGs were mainly determined by Firmicutes, Bacteroidota, Latescibacterota, Chloroflexi and Cyanobacteria at the phylum level, and by Sphingomonas, Ensifer, IMCC26256, Rubellimicrobium, Saccharimonadales, Vicinamibacteraceae, Nocardioides, JG30-KF-CM66 at the genus level. The mentioned dominant bacteria were responsible for intracellular reactive oxygen species (ROS) and cell membrane permeability (CMP) in the substrate layer, where the amplification of intracellular ROS variation were the largest with 144 and 147 % under the condition of TP and salinity, respectively, and the one of CMP variation were the highest more than 165 % under various pollution factors. Furthermore, both increasing DO and reducing salinity could be potential approaches for the inhibition of ARGs transmission in bioretention cells taking into account the simultaneous removal of conventional pollutants.

Engineering Bacterial Biofilm Development and Structure via Regulation of Silver Nanoparticle Density in Graphene Oxide Composite Coating

Graphene-based composites have shown significant potential in the treatment of biofilm infections in clinical settings due to their exceptional antimicrobial properties and specific mechanisms. Nevertheless, a comprehensive understanding of the influence exerted by nanoparticles embedded in the composites on the development and structure of biofilms is still lacking. Here, we fabricate different graphene oxide-silver nanoparticle (GAg) composite-modified substrates (GAgS) with varying densities of silver nanoparticles (AgNPs) and investigate their effects on planktonic bacterial adhesion, subsequent biofilm formation, and mature biofilm structure. Our findings indicate that the initial attachment of Pseudomonas aeruginosa cells during biofilm formation is determined by the density of AgNPs on the GAgS surface. In contrast, the subsequent transition from adherent bacteria to the biofilm is determined by GAgS's synergistic antimicrobial effect. There exists a threshold for the inhibitory performance of GAgS, where the 20 μg/cm2 GAg composite completely prevents biofilm formation; below this concentration, GAgS delays the development of the biofilm and causes structural changes in the mature biofilm with enhanced bacterial growth and increased production of extracellular polymeric substance. More importantly, GAgS have minimal impact on mammalian cell morphology and proliferation while not inducing hemolysis in red blood cells. These results suggest that GAg composites hold promise as a therapeutic approach for addressing medical devices and implant-associated biofilm infections.

Capillary-Assisted Assembly of Soft Conductive Polymer Nanopillar/Tube Arrays and Applications

Nanopillar/tube arrays have emerged as encouraging platforms, possessing remarkable advantages, including large specific areas and highly aligned orientations. Despite the progress of nano/microfabrication technologies, facile and controllable fabrication of conductive polymer nanopillar/tube arrays remains challenging. In this study, we demonstrate that the air-liquid interfacial self-assembly can be extended to obtain three-dimensional nanostructured arrays. A smart and novel method is proposed for preparing uniform conductive polymer nanopillar/tube arrays by a template-mediated interfacial synthesis approach. By utilizing capillary force, precise control processes of the nanostructure and patterned structure can be easily realized. Furthermore, a transfer strategy is devised, allowing for scalable fabrication and expansion of the applicability. Applications, including antibacterial surfaces and actuators, have been demonstrated. We extend the air-liquid interfacial synthesis technique as a powerful and universal strategy for producing ordered nanopillar/tube arrays and show the great potential of soft nanostructured arrays as advanced platforms in diverse applications.

Marine-derived κ-carrageenan-coated zinc oxide nanoparticles for targeted drug delivery and apoptosis induction in oral cancer

BACKGROUND

Kappaphycus alvarezii, a marine red algae species, has gained significant attention in recent years due to its versatile bioactive compounds. Among these, κ-carrageenan (CR), a sulfated polysaccharide, exhibits remarkable antimicrobial properties. This study emphasizes the synergism attained by functionalizing zinc oxide nanoparticles (ZnO NPs) with CR, thereby enhancing its antimicrobial efficacy and target specificity against dental pathogens.

METHODS

In this study, we synthesized ZnO-CR NPs and characterized them using SEM, FTIR, and XRD techniques to authenticate their composition and structural attributes. Moreover, our investigation revealed that ZnO-CR NPs possess better free radical scavenging capabilities, as evidenced by their effective activity in the DPPH and ABTS assay.

RESULTS

The antimicrobial properties of ZnO-CR NPs were systematically assessed using a zone of inhibition assay against dental pathogens of S. aureus, S. mutans, E. faecalis, and C. albicans, demonstrating their substantial inhibitory effects at a minimal concentration of 50 μg/mL. We elucidated the interaction between CR and the receptors of dental pathogens to further understand their mechanism of action. The ZnO-CR NPs demonstrated a dose-dependent anticancer effect at concentrations of 5 μg/mL, 25 μg/mL, 50 μg/mL, and 100 μg/mL on KB cells, a type of Human Oral Epidermal Carcinoma. The mechanism by which ZnO-CA NPs induced apoptosis in KB cells was determined by observing an increase in the expression of the BCL-2, BAX, and P53 genes.

CONCLUSION

Our findings unveil the promising potential of ZnO-CR NPs as a candidate with significant utility in dental applications. The demonstrated biocompatibility, potent antioxidant and antiapoptotic activity, along with impressive antimicrobial efficacy position these NPs as a valuable resource in the ongoing fight against dental pathogens and oral cancer.

New insights into nanotherapeutics for periodontitis: a triple concerto of antimicrobial activity, immunomodulation and periodontium regeneration

Periodontitis is a chronic inflammatory disease caused by the local microbiome and the host immune response, resulting in periodontal structure damage and even tooth loss. Scaling and root planning combined with antibiotics are the conventional means of nonsurgical treatment of periodontitis, but they are insufficient to fully heal periodontitis due to intractable bacterial attachment and drug resistance. Novel and effective therapeutic options in clinical drug therapy remain scarce. Nanotherapeutics achieve stable cell targeting, oral retention and smart release by great flexibility in changing the chemical composition or physical characteristics of nanoparticles. Meanwhile, the protectiveness and high surface area to volume ratio of nanoparticles enable high drug loading, ensuring a remarkable therapeutic efficacy. Currently, the combination of advanced nanoparticles and novel therapeutic strategies is the most active research area in periodontitis treatment. In this review, we first introduce the pathogenesis of periodontitis, and then summarize the state-of-the-art nanotherapeutic strategies based on the triple concerto of antibacterial activity, immunomodulation and periodontium regeneration, particularly focusing on the therapeutic mechanism and ingenious design of nanomedicines. Finally, the challenges and prospects of nano therapy for periodontitis are discussed from the perspective of current treatment problems and future development trends.

Surface Nanostructures Enhanced Biocompatibility and Osteoinductivity of Laser-Additively Manufactured CoCrMo Alloys

Cobalt-chromium-molybdenum (CoCrMo) alloys are widely used in orthopedic implants due to their excellent corrosion and wear resistance and superior mechanical properties. However, their limited capability to promote cell adhesion and new bone tissue formation, poor blood compatibility, and risk of microbial infection can lead to implant failure or reduced implant lifespan. Surface structure modification has been used to improve the cytocompatibility and blood compatibility of implant materials and reduce the risk of infection. In this study, we prepared CoCrMo alloys with surface nanostructures of various aspect ratios (AR) using laser-directed energy deposition (L-DED) and biocorrosion. Our results showed that medium and high AR nanostructures reduced platelet adhesion, while all of the alloys demonstrated good blood compatibility and antibacterial properties. Moreover, the medium and high AR nanostructures promoted cell adhesion and spreading of both preosteoblast MC3T3 cells and human bone marrow mesenchymal stem cells (hMSCs). Furthermore, the nanostructure promoted the osteogenic differentiation of both cell types compared with the flat control surface, with a substantial enhancing effect for the medium and high ARs. Our study proposes a promising approach for developing implant materials with improved clinical outcomes.

Porous Polymersomes as Carriers for Silver Nanoparticles and Nanoclusters: Advantages of Compartmentalization for Antimicrobial Usage

The global threat to public health posed by antibiotic-resistant bacterial infections requires the exploration of innovative approaches. Nanomaterials, particularly silver nanoparticles (AgNPs) and nanoclusters (AgNCs), have emerged as potential solutions to address the pressing issue of a bacterial healthcare crisis. However, the high cytotoxicity levels and low stability associated with AgNPs and AgNCs limit their applicability. To overcome these challenges, AgNCs and AgNPs were synthesized in the presence of porous polymersomes, resulting in a compartmentalized system that enhances stability, reduces cytotoxicity, and maintains high antimicrobial activity. The encapsulated particles exhibit a distribution of silver components on both the surface and the core, which is confirmed through the analysis of surface charge and center of mass. Moreover, our investigation demonstrates improved stability of the nanoparticles and nanoclusters upon entrapment in the porous system, as evidenced by the ion release assay. The antimicrobial effectiveness of porous polymersomes containing AgNPs and AgNCs was demonstrated by visualizing the biofilms and quantifying the penetration depth. Furthermore, cytotoxicity studies showed that compartmentalization increases cell compatibility for AgNC-based systems, showcasing the many advantages this system holds.

Nanomaterials-Enabled Physicochemical Antibacterial Therapeutics: Toward the Antibiotic-Free Disinfections

Bacterial infection continues to be an increasing global health problem with the most widely accepted treatment paradigms restricted to antibiotics. However, the overuse and misuse of antibiotics have triggered multidrug resistance of bacteria, frustrating therapeutic outcomes, and leading to higher mortality rates. Even worse, the tendency of bacteria to form biofilms on living and nonliving surfaces further increases the difficulty in confronting bacteria because the extracellular matrix can act as a robust barrier to prevent the penetration of antibiotics and resist environmental damage. As a result, the inability to eliminate bacteria and biofilms often leads to persistent infection, implant failure, and device damage. Therefore, it is of paramount importance to develop alternative antimicrobial agents while avoiding the generation of bacterial resistance to prevent the large-scale growth of bacterial resistance. In recent years, nano-antibacterial materials have played a vital role in the antibacterial field because of their excellent physical and chemical properties. This review focuses on new physicochemical antibacterial strategies and versatile antibacterial nanomaterials, especially the mechanism and types of 2D antibacterial nanomaterials. In addition, this advanced review provides guidance on the development direction of antibiotic-free disinfections in the antibacterial field in the future.

Sonodynamic therapy-based nanoplatforms for combating bacterial infections

The rapid spread and uncontrollable evolution of antibiotic-resistant bacteria have already become urgent global to treat bacterial infections. Sonodynamic therapy (SDT), a noninvasive and effective therapeutic strategy, has broadened the way toward dealing with antibiotic-resistant bacteria and biofilms, which base on ultrasound (US) with sonosensitizer. Sonosensitizer, based on small organic molecules or inorganic nanoparticles, is essential to the SDT process. Thus, it is meaningful to design a sonosensitizer-loaded nanoplatform and synthesize the nanoplatform with an efficient SDT effect. In this review, we initially summarize the probable SDT-based antibacterial mechanisms and systematically discuss the current advancement in different SDT-based nanoplatform (including nanoplatform for organic small-molecule sonosensitizer delivery and nanoplatform as sonosensitizer) for bacterial infection therapy. In addition, the biomedical applications of SDT-involved multifunctional nanoplatforms are also discussed. We believe the innovative SDT-based nanoplatforms would become a highly efficient next-generation noninvasive therapeutic tool for combating bacterial infection.

White-Light-Responsive Prussian Blue Nanophotonic Particles for Effective Eradication of Bacteria and Improved Healing of Infected Cutaneous Wounds

The increasing burden of cutaneous wound infections with drug-resistant bacteria underlines the dire need for novel treatment approaches. Here, we report the preparation steps, characterization, and antibacterial efficacy of novel chitosan-coated Prussian blue nanoparticles loaded with the photosensitizer fluorescein isothiocyanate-dextran (CHPB-FD). With excellent photothermal and photodynamic properties, CHPB-FD nanoparticles can effectively eradicate both Gram-positive methicillin-resistant Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa in vitro and in vivo. The antibacterial efficacy of CHPB-FD nanophotonic particles further increases in the presence of white light. Using a bacteria-infected cutaneous wound rat model, we demonstrate that CHPB-FD particles upregulate genes involved in tissue remodeling, promote collagen deposition, reduce unwanted inflammation, and enhance healing. The light-responsive CHPB-FD nanophotonic particles can, therefore, be potentially used as an economical and safe alternative to antibiotics for effectively decontaminating skin wounds and for disinfecting biomedical equipment and surfaces in hospitals and other places.

Transdermal Delivery of Photosensitizer-Catalase Conjugate by Fluorinated Polyethylenimine for Enhanced Topical Photodynamic Therapy of Bacterial Infections

Pathogenic bacteria induce subcutaneous infections pose serious threats to global public health. Recently, photodynamic therapy (PDT) has been proposed as a non-invasive approach for anti-microbial treatment without the risk to induce drug resistance. However, due to the hypoxic environment of most anaerobiont-infected sites, the therapeutic efficacy of oxygen consuming PDT has been limited. Herein, a transdermal delivery system is reported to allow effective delivery of photosensitizers into infected skin for PDT treatment of skin infections by bacteria. Considering the overproduction of hydrogen peroxide (H2 O2 ) in the abscess area, catalase (CAT), an enzyme that triggers H2 O2 decomposition to generate O2 , is conjugated with chlorine e6 (Ce6) to form a photosensitizer conjugate (Ce6-CAT) as an enhanced PDT agent against Staphylococcus Aureus. After screening a series of fluorinated low molecular weight polyethylenimine (F-PEI) with different fluorination degrees, the optimized F-PEI formulation is identified with the best transdermal delivery ability system. Upon mixing, the formed Ce6-CAT@F-PEI nanocomplex shows effective transdermal penetration after being applied to the skin surface. With light exposure of the infected skin, highly effective in vivo anti-bacterial PDT therapeutic effect with Ce6-CAT@F-PEI is observed. This work proposes a transdermal PDT therapeutic nanomedicine particularly promising for the anti-bacterial treatment of skin infections.

How Combined Macrolide Nanomaterials are Effective Against Resistant Pathogens? A Comprehensive Review of the Literature

Macrolide drugs are among the broad-spectrum antibiotics that are considered as "miracle drugs" against infectious diseases that lead to higher morbidity and mortality rates. Nevertheless, their effectiveness is currently at risk owing to the presence of devastating, antimicrobial-resistant microbes. In view of this challenge, nanotechnology-driven innovations are currently being anticipated for promising approaches to overcome antimicrobial resistance. Nowadays, various nanostructures are being developed for the delivery of antimicrobials to counter drug-resistant microbial strains through different mechanisms. Metallic nanoparticle-based delivery of macrolides, particularly using silver and gold nanoparticles (AgNPs & AuNPs), demonstrated a promising outcome with worthy stability, oxidation resistance, and biocompatibility. Similarly, macrolide-conjugated magnetic NPs resulted in an augmented antimicrobial activity and reduced bacterial cell viability against resistant microbes. Liposomal delivery of macrolides also showed favorable synergistic antimicrobial activities in vitro against resistant strains. Loading macrolide drugs into various polymeric nanomaterials resulted in an enhanced zone of inhibition. Intercalated nanomaterials also conveyed an outstanding macrolide delivery characteristic with efficient targeting and controlled drug release against infectious microbes. This review abridges several nano-based delivery approaches for macrolide drugs along with their recent achievements, challenges, and future perspectives.

Resorbable Membranes for Guided Bone Regeneration: Critical Features, Potentials, and Limitations

Lack of horizontal and vertical bone at the site of an implant can lead to significant clinical problems that need to be addressed before implant treatment can take place. Guided bone regeneration (GBR) is a commonly used surgical procedure that employs a barrier membrane to encourage the growth of new bone tissue in areas where bone has been lost due to injury or disease. It is a promising approach to achieve desired repair in bone tissue and is widely accepted and used in approximately 40% of patients with bone defects. In this Review, we provide a comprehensive examination of recent advances in resorbable membranes for GBR including natural materials such as chitosan, collagen, silk fibroin, along with synthetic materials such as polyglycolic acid (PGA), polycaprolactone (PCL), polyethylene glycol (PEG), and their copolymers. In addition, the properties of these materials including foreign body reaction, mechanical stability, antibacterial property, and growth factor delivery performance will be compared and discussed. Finally, future directions for resorbable membrane development and potential clinical applications will be highlighted.

A photothermal therapy enhanced mechano-bactericidal hybrid nanostructured surface

Polymeric materials that have been extensively applied in medical devices, wearable electronics, and food packaging are readily contaminated by bothersome pathogenic bacteria. Bioinspired mechano-bactericidal surfaces can deliver lethal rupture for contacted bacterial cells through mechanical stress. However, the mechano-bactericidal activity based only on polymeric nanostructures is not satisfactory, especially for the Gram-positive strain which is generally more resistant to mechanical lysis. Here, we show that the mechanical bactericidal performance of polymeric nanopillars can be significantly enhanced by the combination of photothermal therapy. We fabricated the nanopillars through the combination of low-cost anodized aluminum oxide (AAO) template-assisted method with an environment-friendly Layer-by-Layer (LbL) assembly technique of tannic acid (TA) and iron ion (Fe3+). The fabricated hybrid nanopillar exhibited remarkable bactericidal performances (more than 99%) toward both Gram-negative Pseudomonas aeruginosa (P. aeruginosa) and stubborn Gram-positive Staphylococcus aureus (S. aureus) bacteria. Notably, this hybrid nanostructured surface displayed excellent biocompatibility for murine L929 fibroblast cells, indicating a selective biocidal activity between bacterial cells and mammalian cells. Thus, the concept and antibacterial system described here present a low-cost, scalable, and highly repeatable strategy for the construction of physical bactericidal nanopillars on polymeric films with high performance and biosafety, but without any risks of causing antibacterial resistance.

Biofilm modifiers: The disparity in paradigm of oral biofilm ecosystem

A biofilm is a population of sessile microorganisms that has a distinct organized structure and characteristics like channels and projections. Good oral hygiene and reduction in the prevalence of periodontal diseases arise from minimal biofilm accumulation in the mouth, however, studies focusing on modifying the ecology of oral biofilms have not yet been consistently effective. The self-produced matrix of extracellular polymeric substances and greater antibiotic resistance make it difficult to target and eliminate biofilm infections, which lead to serious clinical consequences that are often lethal. Therefore, a better understanding is required to target and modify the ecology of biofilms in order to eradicate the infection, not only in instances of oral disorders but also in terms of nosocomial infections. The review focuses on several biofilm ecology modifiers to prevent biofilm infections, as well as the involvement of biofilm in antibiotic resistance, implants or in-dwelling device contamination, dental caries, and other periodontal disorders. It also discusses recent advances in nanotechnology that may lead to novel strategies for preventing and treating infections caused by biofilms as well as a novel outlook to infection control.

Antibacterial and Antibiofilm Properties of the Alexidine Dihydrochloride (MMV396785) against Acinetobacter baumannii

Antibiotic-resistant Acinetobacter baumannii infections among patients in hospital settings are rising at an alarming rate. The World Health Organization has designated carbapenem-resistant A. baumannii as a priority pathogen for drug discovery. Based on the open drug discovery approach, we screened 400 compounds provided as a Pandemic Response Box by MMV and DNDi to identify compounds with antibacterial and antibiofilm activity against two A. baumannii reference strains using a highly robust resazurin assay. In vitro screening identified thirty compounds with MIC ≤ 50μM having growth inhibitory properties against the planktonic state. Five compounds, with MMV IDs MMV396785, MMV1578568, MMV1578574, MMV1578564, and MMV1579850, were able to reduce metabolically active cells in the biofilm state. Of these five compounds, MMV396785 showed potential antibacterial and antibiofilm activity with MIC, MBIC, and MBEC of 3.125 μM, 12.5, and 25-100 µM against tested A. baumannii strains, respectively, showing biofilm formation inhibition by 93% and eradication of pre-formed biofilms by 60-77.4%. In addition, MMV396785 showed a drastic reduction in the surface area and thickness of biofilms. Further investigations at the molecular level by qRT-PCR revealed the downregulation of biofilm-associated genes when exposed to 50 µM MMV396785 in all tested strains. This study identified the novel compound MMV396785 as showing potential in vitro antibacterial and antibiofilm efficacy against A. baumannii.

Controlling the Evolution of Selective Vancomycin Resistance through Successful Ophthalmic Eye-Drop Preparation of Vancomycin-Loaded Nanoliposomes Using the Active-Loading Method

Vancomycin is the front-line defense and drug of choice for the most serious and life-threatening methicillin-resistant Staphylococcus aureus (MRSA) infections. However, poor vancomycin therapeutic practice limits its use, and there is a consequent rise of the threat of vancomycin resistance by complete loss of its antibacterial activity. Nanovesicles as a drug-delivery platform, with their featured capabilities of targeted delivery and cell penetration, are a promising strategy to resolve the shortcomings of vancomycin therapy. However, vancomycin's physicochemical properties challenge its effective loading. In this study, we used the ammonium sulfate gradient method to enhance vancomycin loading into liposomes. Depending on the pH difference between the extraliposomal vancomycin-Tris buffer solution (pH 9) and the intraliposomal ammonium sulfate solution (pH 5-6), vancomycin was actively and successfully loaded into liposomes (up to 65% entrapment efficiency), while the liposomal size was maintained at 155 nm. Vancomycin-loaded nanoliposomes effectively enhanced the bactericidal effect of vancomycin; the minimum inhibitory concentration (MIC) value for MRSA decreased 4.6-fold. Furthermore, they effectively inhibited and killed heteroresistant vancomycin-intermediate S.aureous (h-VISA) with an MIC of 0.338 μg mL^-1. Moreover, MRSA could not develop resistance against vancomycin that was loaded into and delivered by liposomes. Vancomycin-loaded nanoliposomes could be a feasible solution for enhancing vancomycin's therapeutic use and controlling the emerging vancomycin resistance.

Review of Antimicrobial Nanocoatings in Medicine and Dentistry: Mechanisms of Action, Biocompatibility Performance, Safety, and Benefits Compared to Antibiotics

This review discusses topics relevant to the development of antimicrobial nanocoatings and nanoscale surface modifications for medical and dental applications. Nanomaterials have unique properties compared to their micro- and macro-scale counterparts and can be used to reduce or inhibit bacterial growth, surface colonization and biofilm development. Generally, nanocoatings exert their antimicrobial effects through biochemical reactions, production of reactive oxygen species or ionic release, while modified nanotopographies create a physically hostile surface for bacteria, killing cells via biomechanical damage. Nanocoatings may consist of metal nanoparticles including silver, copper, gold, zinc, titanium, and aluminum, while nonmetallic compounds used in nanocoatings may be carbon-based in the form of graphene or carbon nanotubes, or composed of silica or chitosan. Surface nanotopography can be modified by the inclusion of nanoprotrusions or black silicon. Two or more nanomaterials can be combined to form nanocomposites with distinct chemical or physical characteristics, allowing combination of different properties such as antimicrobial activity, biocompatibility, strength, and durability. Despite their wide range of applications in medical engineering, questions have been raised regarding potential toxicity and hazards. Current legal frameworks do not effectively regulate antimicrobial nanocoatings in matters of safety, with open questions remaining about risk analysis and occupational exposure limits not considering coating-based approaches. Bacterial resistance to nanomaterials is also a concern, especially where it may affect wider antimicrobial resistance. Nanocoatings have excellent potential for future use, but safe development of antimicrobials requires careful consideration of the "One Health" agenda, appropriate legislation, and risk assessment.

In Vitro Studies of Nanoparticles as a Potentially New Antimicrobial Agent for the Prevention and Treatment of Lameness and Digital Dermatitis in Cattle

Digital dermatitis (DD) is the second most prevalent disease in dairy cattle. It causes significant losses for dairy breeders and negatively impacts cows' welfare and milk yield. Despite this, its etiology has not been entirely identified, and available data are limited. Antibiotic therapy is a practical method for managing animal health, but overuse has caused the evolution of antibiotic-resistant bacteria, leading to a loss in antimicrobial efficacy. The antimicrobial properties of metal nanoparticles (NPs) may be a potential alternative to antibiotics. The aim of this study was to determine the biocidal properties of AgNPs, CuNPs, AuNPs, PtNPs, FeNPs, and their nanocomposites against pathogens isolated from cows suffering from hoof diseases, especially DD. The isolated pathogens included Sphingomonas paucimobilis, Ochrobactrum intermedium I, Ochrobactrum intermedium II, Ochrobactrum gallinifaecis, and Actinomyces odontolyticus. Cultures were prepared in aerobic and anaerobic environments. The viability of the pathogens was then determined after applying nanoparticles at various concentrations. The in vitro experiment showed that AgNPs and CuNPs, and their complexes, had the highest biocidal effect on pathogens. The NPs' biocidal properties and their synergistic effects were confirmed, which may forecast their use in the future treatment and the prevention of lameness in cows, especially DD.

Biodegradable and Cytocompatible Hydrogel Coating with Antibacterial Activity for the Prevention of Implant-Associated Infection

Implant-associated infection (IAI) caused by pathogens colonizing on the implant surface is a serious issue in the trauma-orthopedic surgery, which often leads to implant failure. The complications of IAI bring a big threat to the clinical practice of implants, accompanied by significant economic cost and long hospitalization time. In this study, we propose an antibiotics-free strategy to address IAI-related challenges by using a biodegradable and cytocompatible hydrogel coating. To achieve this, a novel hydrogel system was developed to combine the synergistic effects of good cell affinity and antibacterial properties. The hydrogel material was prepared by modifying a photocross-linkable gelatin-based polymer (GelMA) with cationic quaternary ammonium salt (QAS) groups via a mild and simple synthesis procedure. By engineering the length of the hydrophobic carbon chain on the QAS group and the degree of functionalization, the resulting GelMA-octylQAS hydrogel exhibited an integration of good mechanical properties, biodegradability, excellent bactericidal activity against various types of bacteria, and high cytocompatibility with mammalian cells. When coated onto the implant via the in situ cross-linking procedure, our hydrogel demonstrated superior antimicrobial ability in the infective model of femoral fracture of rats. Our results suggest that the GelMA-octylQAS hydrogel might provide a promising platform for preventing and treating IAI.

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

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

Nanoparticle surface stabilizing agents influence antibacterial action

The antibacterial properties of nanoparticles are of particular interest because of their potential to serve as an alternative therapy to combat antimicrobial resistance. Metal nanoparticles such as silver and copper nanoparticles have been investigated for their antibacterial properties. Silver and copper nanoparticles were synthesized with the surface stabilizing agents cetyltrimethylammonium bromide (CTAB, to confer a positive surface charge) and polyvinyl pyrrolidone (PVP, to confer a neutral surface charge). Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and viable plate count assays were used to determine effective doses of silver and copper nanoparticles treatment against Escherichia coli, Staphylococcus aureus and Sphingobacterium multivorum. Results show that CTAB stabilized silver and copper nanoparticles were more effective antibacterial agents than PVP stabilized metal nanoparticles, with MIC values in a range of 0.003 μM to 0.25 μM for CTAB stabilized metal nanoparticles and 0.25 μM to 2 μM for PVP stabilized metal nanoparticles. The recorded MIC and MBC values of the surface stabilized metal nanoparticles show that they can serve as effective antibacterial agents at low doses.

Drug delivery as a sustainable avenue to future therapies

Climate change and the need for sustainable, technological developments are the greatest challenges facing humanity in the coming decades. To address these issues, in 2015 the United Nations have established 17 Sustainable Development Goals. Anthropogenic climate change will not only affect everyone personally in the coming years, it will also reinforce the need to become more sustainable within drug delivery research. In 2021, I was appointed professor for pharmaceutical biology at the Friedrich-Alexander-University Erlangen-Nürnberg. Our research is at the interface between developing biogenic therapies and understanding of bacterial infections. In this contribution to the Orations - New Horizons of the Journal of Controlled Release, I would like to underline the need for future sustainable approaches in our research area, by highlighting selected examples from the fields of infection research, natural product characterisation and extracellular vesicles. My aim is to put into perspective current issues for these research topics, but also encourage our current student-training framework to contribute to education for sustainable development. This contribution is a personal statement to increase the overall awareness for sustainability challenges in drug delivery and beyond.

Chlorella vulgaris Extract-Decorated Gold Nanoparticle Hybridized Antimicrobial Hydrogel as a Potential Dressing

This study reports a novel design of a moisturizing and antimicrobial hydrogel with injectable properties, using a green solvent (glycerol) as a cross-linking agent and gold nanoparticle reduced by Chlorella extract as an antimicrobial approach. We have synthesized gold nanoparticles (AuNPs) with environmentally friendly and bio-safe properties using Chlorella aqueous extracts (AuNPs@Chlorella). Characterization of the nanoparticles by ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), Raman spectrum, and transmission electron microscope (TEM) confirmed that spherical AuNPs with the particle size of 10-20 nm were successfully synthesized. An analysis of the enhancement of the stability of gelatin hydrogels by the addition of glycerol and AuNPs was performed by rheometry. In addition, we also used Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) to confirm the good antibacterial activity. Therefore, the as-prepared gelatin-glycerol hydrogels containing AuNPs@Chlorella are most likely promising alternatives for wound healing dressings.

Synthesis and Characterization of Calcium Alginate-Based Microspheres Entrapped with TiO2 Nanoparticles and Cinnamon Essential Oil Targeting Clinical Staphylococcus aureus

It is important to create new generations of materials that can destroy multidrug-resistant bacterial strains, which are a serious public health concern. This study focused on the biosynthesis of an essential oil entrapped in titanium dioxide (TiO₂) calcium alginate-based microspheres. In this research, calcium alginate-based microspheres with entrapped TiO₂ nanoparticles and cinnamon essential oil (CI-TiO₂-MSs) were synthesized, using an aqueous extract of Nigella sativa seeds for TiO₂ nanoparticle preparation, and the ionotropic gelation method for microsphere preparation. The microspheres obtained were spherical, uniformly sized, microporous, and rough surfaced, and they were fully loaded with cinnamon essential oil and TiO₂ nanoparticles. The synthesized microspheres were analyzed for antibacterial activity against the clinical multidrug-resistant strain of Staphylococcus aureus. Disc diffusion and flow cytometry analysis revealed strong antibacterial activity by CI-TiO₂-MSs. The synthesized CI-TiO₂-MSs were characterized by the SEM/EDX, X-ray diffraction, and FTIR techniques. Results showed that the TiO₂ nanoparticles were spherical and 99 to 150 nm in size, whereas the CI-TiO₂-MSs were spherical and rough surfaced. Apoptosis analysis and SEM micrography revealed that the CI-TiO₂-MSs had strong bactericidal activity against S. aureus. The in vitro antibacterial experiments proved that the encapsulated CI-TiO₂-MSs had strong potential for use as a prolonged controlled release system against multidrug-resistant clinical S. aureus.

Preventing Antibiotic-Resistant Infections: Additively Manufactured Porous Ti6Al4V Biofunctionalized with Ag and Fe Nanoparticles

Implant-associated infections are highly challenging to treat, particularly with the emergence of multidrug-resistant microbials. Effective preventive action is desired to be at the implant site. Surface biofunctionalization of implants through Ag-doping has demonstrated potent antibacterial results. However, it may adversely affect bone regeneration at high doses. Benefiting from the potential synergistic effects, combining Ag with other antibacterial agents can substantially decrease the required Ag concentration. To date, no study has been performed on immobilizing both Ag and Fe nanoparticles (NPs) on the surface of additively manufactured porous titanium. We additively manufactured porous titanium and biofunctionalized its surface with plasma electrolytic oxidation using a Ca/P-based electrolyte containing Fe NPs, Ag NPs, and the combinations. The specimen’s surface morphology featured porous TiO2 bearing Ag and Fe NPs. During immersion, Ag and Fe ions were released for up to 28 days. Antibacterial assays against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa showed that the specimens containing Ag NPs and Ag/Fe NPs exhibit bactericidal activity. The Ag and Fe NPs worked synergistically, even when Ag was reduced by up to three times. The biofunctionalized scaffold reduced Ag and Fe NPs, improving preosteoblasts proliferation and Ca-sensing receptor activation. In conclusion, surface biofunctionalization of porous titanium with Ag and Fe NPs is a promising strategy to prevent implant-associated infections and allow bone regeneration and, therefore, should be developed for clinical application.

Plasma-induced nanostructured metallic silver surfaces: study of bacteriophobic effect to avoid bacterial adhesion on medical devices

Biofilm formation in medical devices represents one of the major problems for the healthcare system, especially those that occur on implantable silicone-based devices. To provide a general solution to avoid biofilm formation in the first stages of development, this work studied how nanostructured metallic silver coatings hinder bacteria-surface interaction by preventing bacteria adhesion. The three studied silver nanostructures (“Sharp blades”, “Thick blades” and “Leaves”) combined superhydrophobic behavior with a physical impediment of the coating nanostructure that produced a bacteriophobic effect avoiding the adhesion mechanism of different bacterial strains. These silver nanostructures are immobilized on stretchable substrates through a polymeric thin film of plasma–polymerized penta-fluorophenyl methacrylate. The control over the nanostructures and therefore its bacteriophobic—bactericidal effect depends on the plasma polymerization conditions of the polymer. The characterization of this bacteriophobic effect through FE-SEM microscopy, live/dead cell staining, and direct bacterial adhesion counts, provided a complete mapping of how bacteria interact with the surface in each scenario. Results revealed that the bacterial adhesion was reduced by up to six orders of magnitude in comparison with uncoated surfaces thereby constituting an effective strategy to avoid the formation of biofilm on medical materials.

In Situ Surface-Directed Assembly of 2D Metal Nanoplatelets for Drug-Free Treatment of Antibiotic-Resistant Bacteria

The development of antibiotic resistance among bacterial strains is a major global public health concern. To address this, drug-free antibacterial approaches are needed. Copper surfaces have long been known for their antibacterial properties. In this work, a one-step surface modification technique is used to assemble 2D copper chloride nanoplatelets directly onto copper surfaces such as copper tape, transmission electron microscopy (TEM) grids, electrodes, and granules. The nanoplatelets are formed using copper ions from the copper surfaces, enabling their direct assembly onto these surfaces in a one-step process that does not require separate nanoparticle synthesis. The synthesis of the nanoplatelets is confirmed with TEM, scanning electron microscopy, energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). Antibacterial properties of the Cu nanoplatelets are demonstrated in multidrug-resistant (MDR) Escherichia coli, MDR Acinetobacter baumannii, MDR Staphylococcus aureus, E. coli, and Streptococcus mutans. Nanoplatelets lead to a marked improvement in antibacterial properties compared to the copper surfaces alone, affecting bacterial cell morphology, preventing bacterial cell division, reducing their viability, damaging bacterial DNA, and altering protein expression. This work presents a robust method to directly assemble copper nanoplatelets onto any copper surface to imbue it with improved antibacterial properties.

Positively charged BODIPY@carbon dot nanocomposites for enhanced photomicrobicidal efficacy and wound healing

Even with advances in diverse antibiotics, bacterial infectious diseases with high mortality and morbidity still seriously endanger human health, which spurs the development of alternative antiseptic and therapeutic strategies for combatting bacteria. Antimicrobial photodynamic inactivation (aPDI) has emerged as an effective treatment protocol for different types of infection. Moreover, the risk from Gram-positive organisms cannot be overlooked. In the present work, fluoroborondipyrrole (BODIPY) was assembled with cationic and anionic carbon dots (CDs) to construct positively charged (termed p-BDP) and negatively charged (termed n-BDP) nanophotosensitizers. Compared with n-BDP, p-BDP showed a stronger photoinactivation activity against Staphylococcus aureus, and its minimal inhibitory concentration (MIC) was as low as 128 ng mL^-1. In addition, p-BDP could act as a more efficacious wound dressing to accelerate the healing of S. aureus infections. This work opens up alternative thinking for the design of highly effective nanobactericides.

Cell membrane-coated nanoparticles for the treatment of bacterial infection

Despite the enormous success of antibiotics in antimicrobial therapy, the rapid emergence of antibiotic resistance and the complexity of the bacterial infection microenvironment make traditional antibiotic therapy face critical challenges against resistant bacteria, antitoxin, and intracellular infections. Consequently, there is a critical need to design antimicrobial agents that target infection microenvironment and alleviate antibiotic resistance. Cell membrane-coated nanoparticles (CMCNPs) are biomimetic materials that can be obtained by wrapping the cell membrane vesicles directly onto the surface of the nanoparticles (NPs) through physical means. Incorporating the biological functions of cell membrane vesicles and the superior physicochemical properties of NPs, CMCNPs have shown great promise in recent years for targeting infections, neutralizing bacterial toxins, and designing bacterial infection vaccines. This review highlights topics where CMCNPs present great value in advancing the treatment of bacterial infections, including drug delivery, detoxification, and vaccination. Lastly, we discuss the future hurdles and prospects of translating this technique into clinical practice, providing a comprehensive review of the technological developments of CMCNPs in the treatment of bacterial infections. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Interaction between Engineered Pluronic Silica Nanoparticles and Bacterial Biofilms: Elucidating the Role of Nanoparticle Surface Chemistry and EPS Matrix

Nanoparticles (NPs) are considered a promising tool in the context of biofilm control. Many studies have shown that different types of NPs can interfere with the bacterial metabolism and cellular membranes, thus making them potential antibacterial agents; however, fundamental understanding is still lacking on the exact mechanisms involved in these actions. The development of NP-based approaches for effective biofilm control also requires a thorough understanding of how the chosen nanoparticles will interact with the biofilm itself, and in particular with the biofilm self-produced extracellular polymeric matrix (EPS). This work aims to provide advances in the understanding of the interaction between engineered fluorescent pluronic silica (PluS) nanoparticles and bacterial biofilms, with a main focus on the role of the EPS matrix in the accumulation and diffusion of the particles in the biofilm. It is demonstrated that particle surface chemistry has a key role in the different lateral distribution and specific affinity to the biofilm matrix components. The results presented in this study contribute to our understanding of biofilm-NP interactions and promote the principle of the rational design of smart nanoparticles as an important tool for antibiofilm technology.

A Flexible Anti-Biofilm Hygiene Coating for Water Devices

Biofilm is a microbiome complex comprising different bacterial colonies that typically adhere to device surfaces in water, which causes serious medical issues such as indwelling infections and outbreaks. Here, we developed a non-nanoparticle, flexible anti-biofilm hygiene coating consisting of lithocholic acid (LCA), zinc pyrithione (Zn), and cinnamaldehyde (Cn) (named as LCA-Zn-Cn) that largely prevents the bacteria adhesion to various water device surfaces such as stainless steel and glass through a synergistic mechanism. The existing chelated groups on LCA and Cn attract plenty of bacteria via hydrophobic interaction. Both the bactericidal reaction by grafting biocidal groups from both LCA and Cn and the bacteriostatic reaction by inhibiting cell division via zinc ions (Zn) lead to a largely improved bacteria/biofilm prevention. The antibacterial performance was assessed by using the JIS Z 2801/ISO 22196 method. The designed LCA-Zn-Cn coating displayed log₁₀ reduction of 4.23 (99.9% reduction) of E. coli and log₁₀ reduction of 3.51 (99.8% reduction) of E. faecalis on stainless steel, which are much higher than the control samples, demonstrating a promising colonization inhibition. In parallel, the polysulfone encapsulated beads also showed >99% reduction efficiency in batch and >97-98% reduction efficiency in continuous column tests using the Lake Michigan water. Due to the strong cross-linked configuration, the coating still showed >90.9% bacterial reduction after 3000 abrasion cycles and over 99.9% bacteria reduction after a high flow velocity of 1.99 m/s test, which confirmed the enhanced mechanical durability. By applying either spray or dip-coating, the designed polymer composite can be coated on a variety of irregular water devices with mass production using an auto-controlled robot arm.

Recent Progress on Bioinspired Antibacterial Surfaces for Biomedical Application

Surface bacterial fouling has become an urgent global challenge that calls for resilient solutions. Despite the effectiveness in combating bacterial invasion, antibiotics are susceptible to causing microbial antibiotic resistance that threatens human health and compromises the medication efficacy. In nature, many organisms have evolved a myriad of surfaces with specific physicochemical properties to combat bacteria in diverse environments, providing important inspirations for implementing bioinspired approaches. This review highlights representative natural antibacterial surfaces and discusses their corresponding mechanisms, including repelling adherent bacteria through tailoring surface wettability and mechanically killing bacteria via engineering surface textures. Following this, we present the recent progress in bioinspired active and passive antibacterial strategies. Finally, the biomedical applications and the prospects of these antibacterial surfaces are discussed.

Accelerated neutral atom beam (ANAB) modified polyethylene for decreased wear and reduced bacteria colonization: An in vitro study

Ultra-high molecular weight polyethylene (UHMWPE) model implants were modified using accelerated neutral atom beam (ANAB) technology and tested for in vitro wear properties and bacteria colonization. Material characterization studies using atomic force microscopy (AFM), surface energy, and in vitro protein adsorption events were also conducted to better understand the mechanism behind such wear properties and bacteria colonization. ANAB modified UHMWPE showed significantly reduced wear properties compared to controls due to nanostructured features, greater surface energy, and improved adsorption of lubricin, a synovial fluid lubricating protein. There was significantly greater adsorption of proteins known to reduce bacteria colonization (specifically, mucin, casein, and lubricin) after 4 h on UHMWPE after ANAB treatment. Such changes in initial protein events led to significantly decreased bacteria (including methicillin resistant Staph. aureus (or MRSA), Staph. aureus, E. coli, multi-drug resistant E. coli, Pseudomonas aeruginosa and Staph. epidermidis) colonization after 24 h without resorting to antibiotic use.

Antibiotic-loaded lipid-based nanocarrier: a promising strategy to overcome bacterial infection

According to the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC), bacterial infections are one of the greatest threats to global health, food production, and life expectancy. In this sense, the development of innovative formulations aiming at greater therapeutic efficacy, safety, and shorter treatment duration compared to conventional products is urgently needed. Lipid-based nanocarriers (LBNs) have demonstrated the potential to enhance the effectiveness of available antibiotics. Among them, liposome, nanoemulsion, solid lipid nanoparticle (SLN), and nanostructured lipid carrier (NLC) are the most promising due to their solid technical background for laboratory and industrial production. This review describes recent advances in developing antibiotic-loaded LBNs against susceptible and resistant bacterial strains and biofilm. LBNs revealed to be a promising alternative to deliver antibiotics due to their superior characteristics compared to conventional preparations, including their modified drug release, improved bioavailability, drug protection against chemical or enzymatic degradation, greater drug loading capacity, and biocompatibility. Antibiotic-loaded LBNs can improve current clinical drug therapy, bring innovative products and rescue discarded antibiotics. Thus, antibiotic-loaded LBNs have potential to open a window of opportunities to continue saving millions of lives and prevent the devastating impact of bacterial infection.

Near-infrared laser-controlled nitric oxide-releasing gold nanostar/hollow polydopamine Janus nanoparticles for synergistic elimination of methicillin-resistant Staphylococcus aureus and wound healing

Recently, nitric oxide (NO) has received increasing interest in combat against bacteria-induced infections because of its ability to sensitize and enhance the antibacterial effectiveness of many therapeutic approaches such as antibiotics. However, high-efficient loading and controlled release of NO remain a big challenge. In the present work, a type of gold nanostar/hollow polydopamine Janus nanostructure (GNS/HPDA JNPs) with precise near infrared (NIR)-controlled NO release property was fabricated using a facile seed-mediated method. Upon NIR laser irradiation, the NO-releasing GNS/HPDA JNPs (GNS/HPDA-BNN6) exhibited a synergistic photothermal and NO antibacterial effect by significantly inhibiting the growth and biofilm formation of both Gram-negative and Gram-positive bacterial strains, including methicillin-resistant Staphylococcus aureus (MRSA). An in-depth mechanism study revealed that two pathways were mainly involved in the synergistic photothermal and NO antibacterial effect. In one pathway, the synergistic effect severely destroyed the bacterial membrane by causing leakage of intracellular components such as DNA. In another pathway, the synergistic effect largely disturbed bacterial metabolism by regulating relative metabolic genes, followed by enhancing ROS generation to cause intracellular GSH depletion and DNA damage. More importantly, the synergistic effect significantly diminished the drug resistance of MRSA by downregulating the expression of the drug-resistant gene mecA and some relative multidrug efflux pumps (e.g., SepA and Tet38). An in vivo evaluation using a rat model with MRSA-infected wounds indicated that the synergistic photothermal and NO effect of GNS/HPDA-BNN6 can effectively eliminate MRSA from wounds, thereby alleviating inflammation and promoting wound healing. STATEMENT OF SIGNIFICANCE: Multidrug-resistant (MDR) bacteria have become a big threat to mankind, and therefore, the development of innovative antibacterial agents with high antibacterial efficiency is urgently required. Nanomaterial-mediated nitric oxide (NO) therapy is a promising strategy to effectively combat MDR bacteria through a synergistic antibacterial effect. Here, a gold nanostar/hollow polydopamine Janus nanostructure with precise near infrared (NIR) light-controlled NO release property (GNS/HPDA-BNN6) was developed. Both in vitro and in vivo evaluations demonstrated that GNS/HPDA-BNN6 could effectively eliminate methicillin-resistant Staphylococcus aureus (MRSA) from infected wounds and promote wound healing through a synergistic photothermal and NO therapeutic effect. Remarkably, the synergistic effect significantly diminished the drug resistance of MRSA by downregulating the expression of some drug-resistant genes and multidrug efflux pumps.

Emerging Concern with Imminent Therapeutic Strategies for Treating Resistance in Biofilm

Biofilm production by bacteria is presumed to be a survival strategy in natural environments. The production of biofilms is known to be influenced by a number of factors. This paper has precisely elaborated on the different factors that directly influence the formation of biofilm. Biofilm has serious consequences for human health, and a variety of infections linked to biofilm have emerged, rapidly increasing the statistics of antimicrobial resistance, which is a global threat. Additionally, to combat resistance in biofilm, various approaches have been developed. Surface modifications, physical removal, and the use of nanoparticles are the recent advances that have enabled drug discovery for treating various biofilm-associated infections. Progress in nanoparticle production has led to the development of a variety of biofilm-fighting strategies. We focus on the present and future therapeutic options that target the critical structural and functional characteristics of microbial biofilms, as well as drug tolerance mechanisms, such as the extracellular matrix, in this review.

Targeting Multidrug Resistance With Antimicrobial Peptide-Decorated Nanoparticles and Polymers

As a category of small peptides frequently found in nature, antimicrobial peptides (AMPs) constitute a major part of the innate immune system of various organisms. Antimicrobial peptides feature various inhibitory effects against fungi, bacteria, viruses, and parasites. Due to the increasing concerns of antibiotic resistance among microorganisms, development of antimicrobial peptides is an emerging tool as a favorable applicability prospect in food, medicine, aquaculture, animal husbandry, and agriculture. This review presents the latest research progress made in the field of antimicrobial peptides, such as their mechanism of action, classification, application status, design techniques, and a review on decoration of nanoparticles and polymers with AMPs that are used in treating multidrug resistance. Lastly, we will highlight recent progress in antiviral peptides to treat emerging viral diseases (e.g., anti-coronavirus peptides) and discuss the outlook of AMP applications.

Bioinspired Phosphorylcholine Coating for Surface Functionalization of Interventional Biomedical Implants with Bacterial Resistance and Anti-Encrustation Properties

Enhancing the lubrication property and bacterial resistance is extremely important for interventional biomedical implants to avoid soft tissue damage and biofilm formation. In this study, a zwitterionic phosphorylcholine coating (PMPC) was successfully developed to achieve surface functionalization of a polyurethane (PU)-based ureteral stent via subsurface "grafting from" photopolymerization. Typical surface characterizations such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and surface wettability and morphology analyses examined by scanning electron microscopy, atomic force microscopy, and transmission electron microscopy demonstrated that the phosphorylcholine polymer was grafted on the substrate with a thickness of 180 nm. Additionally, the tribological experiment performed by a universal material tester showed that the lubrication performance of PU-PMPC was significantly improved compared with that of PU. The in vitro experiments indicated that the PMPC coating was biocompatible and stably modified on the surface of the substrate with an excellent bacterial resistance rate of >90%. Furthermore, the result of the in vivo experiment showed that the anti-encrustation performance of the surface-functionalized ureteral stent was better than that of the bare ureteral stent. The great enhancement in the lubrication, bacterial resistance, and anti-encrustation properties of the phosphorylcholine coating was thought to be due to the hydration effects of the zwitterionic charges. In summary, the bioinspired zwitterionic phosphorylcholine coating developed herein achieved significantly improved lubrication, bacterial resistance, and anti-encrustation performances and could be used as a convenient approach for surface functionalization of interventional biomedical implants.

Biocompatible mechano-bactericidal nanopatterned surfaces with salt-responsive bacterial release

Bio-inspired nanostructures have demonstrated highly efficient mechano-bactericidal performances with no risk of bacterial resistance; however, they are prone to become contaminated with the killed bacterial debris. Herein, a biocompatible mechano-bactericidal nanopatterned surface with salt-responsive bacterial releasing behavior is developed by grafting salt-responsive polyzwitterionic (polyDVBAPS) brushes on a bio-inspired nanopattern surface. Benefiting from the salt-triggered configuration change of the grafted polymer brushes, this dual-functional surface shows high mechano-bactericidal efficiency in water (low ionic strength condition), while the dead bacterial residuals can be easily lifted by the extended polymer chains and removed from the surface in 1 M NaCl solution (high ionic strength conditions). Notably, this functionalized nanopatterned surface shows selective biocidal activity between bacterial cells sand eukaryotic cells. The biocompatibility with red blood cells (RBCs) and mammalian cells was tested in vitro. The histocompatibility and prevention of perioperative contamination activity were verified by in vivo evaluation in a rat subcutaneous implant model. This nanopatterned surface with bacterial killing and releasing activities may open new avenues for designing bio-inspired mechano-bactericidal platforms with long-term efficacy, thus presenting a facile alternative in combating perioperative-related bacterial infection. STATEMENT OF SIGNIFICANCE: Bioinspired nanostructured surfaces with noticeable mechano-bactericidal activity showed great potential in moderating drug-resistance. However, the nanopatterned surfaces are prone to be contaminated by the killed bacterial debris and compromised the bactericidal performance. In this study, we provide a dual-functional antibacterial conception with both mechano-bactericidal and bacterial releasing performances not requiring external chemical bactericidal agents. Additionally, this functionalized antibacterial surface also shows selective biocidal activity between bacteria and eukaryotic cells, and the excellent biocompatibility was tested in vitro and in vivo. The new concept for the functionalized mechano-bactericidal surface here illustrated presents a facile antibiotic-free alternative in combating perioperative related bacterial infection in practical application.

Erythrocyte Membrane-Enveloped Molybdenum Disulfide Nanodots for Biofilm Elimination on Implants via Toxin Neutralization and Immune Modulation

Implant-related infections (IRIs) caused by bacterial biofilms remain a prevalent but tricky clinical issue, which are characterized by drug resistance, toxin impairment and immunity suppression. Recently, antimicrobial therapies based on...

Thermoresponsive Nanostructures: From Mechano-Bactericidal Action to Bacteria Release

Overuse of antibiotics can increase the risk of notorious antibiotic resistance in bacteria, which has become a growing public health concern worldwide. Featured with the merit of mechanical rupture of bacterial cells, the bioinspired nanopillars are promising alternatives to antibiotics for combating bacterial infections while avoiding antibacterial resistance. However, the resident dead bacterial cells on nanopillars may greatly impair their bactericidal capability and ultimately impede their translational potential toward long-term applications. Here, we show that the functions of bactericidal nanopillars can be significantly broadened by developing a hybrid thermoresponsive polymer@nanopillar-structured surface, which retains all of the attributes of pristine nanopillars and adds one more: releasing dead bacteria. We fabricate this surface through coaxially decorating mechano-bactericidal ZnO nanopillars with thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes. Combining the benefits of ZnO nanopillars and PNIPAAm chains, the antibacterial performances can be controllably regulated between ultrarobust mechano-bactericidal action (∼99%) and remarkable bacteria-releasing efficiency (∼98%). Notably, both the mechanical sterilization against the live bacteria and the controllable release for the pinned dead bacteria solely stem from physical actions, stimulating the exploration of intelligent structure-based bactericidal surfaces with persistent antibacterial properties without the risk of triggering drug resistance.

Ovotransferrin Antibacterial Peptide Coupling Mesoporous Silica Nanoparticle as an Effective Antibiotic Delivery System for Treating Bacterial Infection In Vivo

Antibiotic-resistant pathogens are a serious threat to global public health. The emergence of drug-resistant pathogens is due to the improper use of antibiotics, making the treatment of bacterial infections very challenging. Here, we reported an efficient antibiotic delivery nanoparticle to minimize antibiotic resistance. The nanoparticle was designed to target the bacterial membrane using mesoporous silica nanoparticles (MSNs) modified with an ovotransferrin-derived antimicrobial peptide (OVTp12), enabling the antibiotic to be delivered to the vicinity of the pathogenic bacteria. Moreover, we observed that OVTp12-modified nanoparticles effectively inhibited the growth of Escherichia coli in vitro and in vivo. The nanoparticle with high biosafety could significantly downregulate the expression of inflammation-related cytokines in infected tissues. Thus, this novel bacterial targeted nanoparticle provides advantages in minimizing bacterial drug resistance and treating bacterial infection.