Natural and bioinspired nanostructured bactericidal surfaces

Advanced antimicrobial surfaces in cellulose-based food packaging

This critical review provides a comprehensive framework for selecting engineered colloidal and nanostructured systems for cellulose-based food packaging. Meta-analysis was used as a methodological approach to categorize them according to antimicrobial agents, coating methods, and synergistic effects against a broad spectrum of microorganisms. The most frequent substrate is flexible packaging paper (35-70 g/m2, uncalendered), often intended for food wrapping. Among antimicrobial agents, chitosan-based coatings are a common choice-often combined with essential oils-being particularly effective against Gram-positive bacteria (e.g., Staphylococcus aureus, Listeria monocytogenes, Bacillus subtilis). This is attributed to electrostatic interactions between the polysaccharide's protonated -NH3+ groups and teichoic acids within bacterial cell walls. Inorganic metal nanoparticles, such as ZnO nanorods and Ag nanoparticles, are broadly effective by compromising the membranes of various foodborne pathogens-including Bacillus cereus and Pseudomonas aeruginosa. Terpenoid- or phenolic-rich essential oils-commonly delivered in emulsions or encapsulated in host-guest β-cyclodextrin complexes-inhibit the growth of yeasts and molds, besides some common bacteria when grafted onto bleached paper. Synergistic effects have been observed with complex coatings such as chitosan combined with CuONPs. Despite their promising performance, the widespread industrial adoption of cellulose-based active packaging in the food sector requires addressing not only antimicrobial activity, but also barrier properties and feasible methods to functionalize the paper surface (e.g., bar coating). These challenges, often overlooked, are critically assessed herein. All considered, further studies are required to address the challenges of cellulosic antimicrobial materials in a holistic manner to accelerate its large-scale implementation in the food sector.

Nanowire arrays with programmable geometries as a highly effective anti-biofilm surface

Biofilm-related microbial infections are the Achilles' heel of many implantable medical devices. Surface patterning with nanostructures in the form of vertically aligned silicon (Si) nanowires (VA-SiNWs) holds promise to prevent these often "incurable" infections. In this study, we fabricated arrays of highly ordered SiNWs varying in three geometric parameters, including height, pitch size, and tip diameter (sharpness). Anti-infective efficacies of fabricated SiNW arrays were assessed against representative laboratory reference bacterial strains, Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922, using a modified microwell biofilm assay representing microorganism-implant interactions at a liquid-solid interface. To further understand the role of individual geometric parameters to the SiNW-induced bacterial killing, SiNW arrays with stepwise changes in individual geometric parameters were compared. The force that NWs applied on bacterial cells was mathematically calculated. Our results suggested that NWs with specific geometries were able to kill adherent bacterial cells and prevent further biofilm formation on biomaterial surfaces. Tip diameter and pitch size appeared to be key factors of nanowires predetermining their anti-infectiveness. Mechanistic investigation found that tip diameter and pitch size co-determined the pressure that NWs put on the cell envelope. The most effective anti-infective NWs fabricated in our study (50 nm in tip diameter and 400 nm in pitch size for S. aureus and 50 nm in tip diameter and 800 nm in pitch size for E. coli) put pressures of approximately 2.79 Pa and 8.86 Pa to the cell envelop of S. aureus and E. coli, respectively, and induced cell lyses. In addition, these NWs retained their activities against clinical isolates of S. aureus and E. coli from patients with confirmed device-related infections and showed little toxicity against human fibroblast cells and red blood cells.

Inherent variation in surface roughness of Selective Laser Melting (SLM) printed titanium caused by build angle changes the mechanomicrobiocidal effectiveness of nanostructures

Additively manufactured titanium implant materials are rapidly advancing prosthetics and orthopaedic devices by making them more cost-effective and customisable. However, the surface finish of materials printed via Selective Laser Melting (SLM) currently limits their integration into the medical device field. Printing parameters, such as build angle inclination, can cause variations in the surface roughness of a part, often exceeding what is suitable for implant materials. Excessive roughness can promote microbial attachment and proliferation, potentially leading to implant rejection. Nanostructuring titanium has previously demonstrated success in mitigating bacteria and fungi via a mechanomicrobiocial mechanism on traditionally flat titanium and complex SLM-made parts but its effectiveness on the inherent roughness of three-dimensional (3D) printed titanium remains unexplored. This study examines the surface roughness of 3D-Ti at three build angles (0, 40 and 90 degrees), before and after nanostructuring. Surfaces were assessed against methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans, representative antimicrobial resistant pathogens. Results showed the nanostructures were more effective against MRSA, but microbial attachment increase with steeper angles, regardless of the presence of nanostructures. This study investigates how surface roughness of 3D printed titanium substrates impacts bacterial and fungal adhesion and the resulting nanomorphology of the surface post-hydrothermal modification.

Baicalin Relieves Glaesserella parasuis-Triggered Immunosuppression Through Polarization via MIF/CD74 Signaling Pathway in Piglets

Glaesserella parasuis (G. parasuis) infection is responsible for Glässer's disease in pigs. G. parasuis could trigger piglet immunosuppression, but the mechanism of inducing immunosuppression by G. parasuis remains unknown. Macrophage migration inhibitory factor (MIF)/CD74 axis has been shown to participate in inflammation response and immunosuppression, but the function of MIF/CD74 during immunosuppression elicited by G. parasuis has not been fully explored. This experiment explored the efficacy of baicalin on immunosuppression elicited by G. parasuis alleviation through regulating polarization via the MIF/CD74 signaling pathway. Our data indicated that baicalin reduced IL-1β, IL-6, IL-8, IL-18, TNF-α, and COX-2 expression, and regulated MIF/CD74 axis expression in the spleen. Immunohistochemistry analysis showed that baicalin enhanced CD74 protein levels in the spleen of piglets induced by G. parasuis. Baicalin regulated the PI3K/Akt/mTOR signaling pathway and RAF/MEK/ERK signaling activation, modified the expression of the autophagy-related proteins Beclin-1, P62, and LC3B, promoted M2 polarization to M1 polarization, and enhanced CD3, CD4, CD8, and TIM3 levels in the spleen of piglets elicited by G. parasuis. Our study reveals the important functions of the MIF/CD74 axis in G. parasuis-induced immunosuppression and may offer a new therapeutic method to control G. parasuis infection.

Design and Fabrication of Bioactive and Antibacterial LIPSS Surfaces on Titanium Alloy by Femtosecond Laser

A titanium alloy is widely used in implants for its excellent mechanical properties and corrosion resistance. However, the bonding strength between a titanium alloy and bone tissue is low, and the bacterial adhesion is easily triggered on the implant surface, which may cause the failure of implants. Therefore, surface modification is necessary to improve the biological activity and antibacterial properties. In this work, four different types of laser-induced periodic surface structure (LIPSS) surfaces are designed and fabricated on the TiNi alloy by a femtosecond laser according to the size of MC3T3-E1 mouse embryonic osteoblasts. The in vitro osteogenic activity of the LIPSS surface is investigated. It is found that the LIPSS helps improve the in vitro osteogenic activity, and bonelike apatite tends to deposit and distribute on the LIPSS. The biological activity and antibacterial activity of the LIPSS surface are evaluated through cell culture experiments and Escherichia coli culture experiments. It is demonstrated that the horizontal LIPSS sample with a width of 30 μm has the highest cell proliferation rate (142.5% after 1 day, 132.3% after 3 days) and a good antibacterial rate (50.2%). These results provide guidance for the application of the LIPSS in biocompatibility and antibacterial aspects.

A review of the advances in implant technology: accomplishments and challenges for the design of functionalized surface structures

Biomedical implants are extensively utilized to replace hard-tissue defects owing to their biocompatibility and remarkable tissue-affinity. The materials and functional design are selected based on the resultant osseointegration level and resistance to infection, and these considerations constitute the dominant research topic in this field. However, high rates of implantation failure and peri-implantitis have been reported. Current research on biomedical-implant design encompasses enhancement of the implant surface properties, such as the roughness, nano/micro topography, and hydrophilicity, along with the realization of advanced features including antibacterial properties and cell and immunomodulation regulation. This review considers the two achievements of contemporary implant manufacturing; namely, osseointegration and the realization of antibacterial properties. Present mainstream surface modifications and coatings are discussed, along with functional design technologies and achievements. The impacts of direct surface-treatment techniques and osteogenic functional coatings on osseointegration performance and antibacterial surface structures are elucidated, considering inorganic and organic coatings with antibacterial properties as well as antibiotic-releasing coatings. Furthermore, this review highlights recent advancements in physically driven antimicrobial strategies. Expanding upon existing research, future directions for implant studies are proposed, including the realization of comprehensive functionality that integrates osseointegration and antibacterial properties, as well as patient-specific design. Our study presents a comprehensive review and offers a novel perspective on the design of biomedical implants for enhanced versatility. An in-depth exploration of future research directions will also stimulate subsequent investigations.

Boosting the antibacterial potency of natural products through nanotechnologies

The advent of bacterial resistance has led to a notable challenge in effectively treating bacterial infections. This highlights the urgent need for the development of novel and effective drugs to combat bacterial infections. Medicinal plants, with their rich and diverse natural compounds, represent a valuable source for the discovery of novel antibacterial agents. Many of these natural compounds exhibit strong antibacterial functions, offering a promising direction for the development of antibacterial drugs. Furthermore, the application of nanotechnology in the development of antibacterial natural products has become a topic of considerable interest due to the advantages it offers, including the potential to enhance drug solubility. The efficacy of natural antibacterial agents is significantly enhanced through nanotechnology. This review offers a comprehensive overview of recent advances in the delivery of natural antibacterial compounds using a range of nanoformulation strategies.

Exploring Broad-Spectrum Antimicrobial Nanotopographies: Implications for Bactericidal, Antifungal, and Virucidal Surface Design

Inspired by the natural defense strategies of insect wings and plant leaves, nanostructured surfaces have emerged as a promising tool in various fields, including engineering, biomedical sciences, and materials science, to combat bacterial contamination and disrupt biofilm formation. However, the development of effective antimicrobial surfaces against fungal and viral pathogens presents distinct challenges, necessitating tailored approaches. Here, we aimed to review the recent advancements of the use of nanostructured surfaces to combat microbial contamination, particularly focusing on their mechano-bactericidal and antifungal properties, as well as their potential in mitigating viral transmission. We comparatively analyzed the diverse geometries and nanoarchitectures of these surfaces and discussed their application in various biomedical contexts, such as dental and orthopedic implants, drug delivery systems, and tissue engineering. Our review highlights the importance of preventing microbial attachment and biofilm formation, especially in the context of rising antimicrobial resistance and the economic impact of biofilms. We also discussed the latest progress in materials science, particularly nanostructured surface engineering, as a promising strategy for reducing viral transmission through surfaces. Overall, our findings underscore the significance of innovative strategies to mitigate microbial attachment and surface-mediated transmission, while also emphasizing the need for further interdisciplinary research in this area to optimize antimicrobial efficacy and address emerging challenges.

Surface Modification of Stainless Steel for Enhanced Antibacterial Activity

Stainless-steel grade 316L is widely used in medical and food processing applications due to its corrosion resistance and durability. However, its inherent lack of antibacterial properties poses a challenge in environments requiring high hygiene standards. This study investigates a novel surface modification approach combining electrochemical anodization and nonthermal plasma treatment to enhance the antibacterial efficacy of SS316L. The surface morphology, roughness, chemical composition, and wettability of the modified surfaces were systematically analyzed using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and water contact angle (WCA) measurements. SEM revealed the formation of tunable nanoporous structures with pore diameters ranging from 100 to 300 nm, depending on the applied anodizing voltage (40 and 60 V). AFM measurements demonstrated that surface roughness varied significantly with anodizing voltage, from 4.3 ± 0.4 nm at 40 V to 15.0 ± 0.6 nm at 60 V. XPS analysis confirmed the presence of Cr2O3, a key oxide for corrosion resistance, and revealed increased oxygen concentration after plasma treatment, indicating enhanced surface oxidation. Wettability studies showed that plasma treatment changed the surfaces to superhydrophilic, with WCAs below 5°. Antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was significantly improved, with plasma-treated samples exhibiting up to 92% reduction in bacterial adhesion. These results demonstrate that the combined anodization and plasma treatment process effectively enhances the antibacterial and surface properties of SS316L, making it a promising strategy for applications in medical and food processing industries.

Modifying the antibacterial performance of Cu surfaces by topographic patterning in the micro- and nanometer scale

Antimicrobial surfaces are a promising approach to reduce the spread of pathogenic microorganisms in various critical environments. To achieve high antimicrobial functionality, it is essential to consider the material-specific bactericidal mode of action in conjunction with bacterial surface interactions. This study investigates the effect of altered contact conditions on the antimicrobial efficiency of Cu surfaces against Escherichia coli and Staphylococcus aureus. The fabrication of line-like periodic surface patterns in the scale range of single bacterial cells was achieved utilizing ultrashort pulsed direct laser interference patterning. These patterns create both favorable and unfavorable topographies for bacterial adhesion. The variation in bacteria/surface interaction is monitored in terms of strain-specific bactericidal efficiency and the role of corrosive forces driving quantitative Cu ion release. The investigation revealed that bacterial deactivation on Cu surfaces can be either enhanced or decreased by intentional topography modifications, independent of Cu ion emission, with strain-specific deviations in effective pattern scales observed. The results of this study indicate the potential of targeted topographic surface functionalization to optimize antimicrobial surface designs, enabling strain-specific decontamination strategies.

Design of Antibiofouling Lubricant-Impregnated Surfaces Robust to Cell-Growth-Induced Instability

Biofouling, commonly referred to as the unwanted deposition of cells on wetted solids, is a serious operational and environmental issue in many underwater and biomedical applications. Over the past decade, lubricant-impregnated surfaces (LIS) arose as a potential solution to prevent fouling, owing to their unique layer of lubricant masking the solid from the outer environment, thereby preventing biofouling. However, living microorganisms alter their environment by reproducing and secreting biomolecules, which can threaten the stability of such coatings over time. In this paper, we show that secretion of biomolecules from aquatic cells and subsequent changes in the interfacial tension of the surrounding media can trigger dewetting of the lubricant, ultimately exposing the surface to the outer solution and therefore becoming prone to fouling. By observing LIS immersed in Nannochloropsis oculata algae solutions at various stages of population growth, we establish a correlation between the decrease in interfacial tension and wetting states of the surface. We also visualize dewetting of the lubricant through confocal imaging performed in situ. Finally, we establish a diagram providing fundamental insights to design sturdy LIS circumventing such dewetting, therefore ensuring long-term protection against biofouling upon extended immersion in living cell solutions.

Development of endolysin-integrated pH-responsive antiadhesive and antibacterial coatings with nanorods for the prevention of cross-contamination in fresh produce

Cross-contamination is a major food safety risk during the harvesting and processing of fresh produce, leading to significant losses in global human well-being and the economy. The surface of food contact areas is a high-risk zone for cross-contamination. Therefore, developing an effective antimicrobial coating for food-contact surfaces is essential. This study developed a smart antimicrobial coating that self-regulated in response to environmental conditions, via grafting the stimuli-responsive polymer polyacrylic acid (PAA) and the phage-derived endolysin Lysin81 onto ZnO nanocolumns. During the initial stage of bacterial adhesion, the surface of the nanocolumns exhibited significant mechanical bactericidal activity, while the super hydrophilic PAA layer effectively inhibited bacterial adhesion. At a later stage, when numerous live and dead bacteria adhered to the surface of the nanocolumns, the PAA chains disintegrated, exposing the underlying layer of endolysin that lysed the compromised bacteria. In addition, as the environmental pH increases, the attached dead bacteria can be released once the PAA chains regain their hydrophilicity. This research aimed to apply the antibacterial coating to stainless steel surfaces used in food processing, potentially enhancing surface hygiene and preventing cross-contamination of fresh produce.

2D wrinkle assisted zigzag plasmonic chains for isotropic SERS enhancement

Template-assisted colloidal self-assembly has gained significant attention due to its flexibility and versatility. By precisely controlling the shape of the template, it is possible to achieve custom-designed nanoparticle assemblies. However, a major challenge remains in fabricating these templates over large areas at a low cost. Recently, one-dimensional (1D) nano-wrinkle structures have been effectively used for the linear assembly of single-chain or multi-chain nanoparticles, which feature abundant interparticle nanogaps that facilitate efficient plasmonic coupling. To further enhance these assemblies by incorporating diffraction modes, we develop two-dimensional (2D) zigzag wrinkle structures that successfully assemble nanoparticles into plasmonic zigzag chains. Micro spectral measurements and FDTD simulations reveal that zigzag assemblies of plasmonic nanoparticle chains offer isotropic behavior and exhibit stronger plasmonic coupling compared to 1D assemblies, which could be highly beneficial for sensing applications. Due to the responsive PANI shell encapsulating the gold nanoparticles, this 2D zigzag assembly enables flexible tuning of plasmonic resonance under pH regulation.

Evaluation of the Antibacterial and Cell Culture Properties of Anodic Porous Alumina Prepared in Concentrated H2SO4

The antibacterial activity of anodic porous alumina (APA) prepared using phosphoric, oxalic, and sulfuric acids was tested, and it was found that APA prepared using sulfuric acid had the highest antibacterial activity against Staphylococcus aureus and Escherichia coli. In addition, the results of the antibacterial test using APA prepared with different concentrations of sulfuric acid showed that APA prepared in concentrated sulfuric acid exhibited significantly higher antibacterial activity. APA formed in concentrated sulfuric acid also showed excellent antibacterial activity even at a high culture medium concentration, at which bacterial cells tend to multiply easily. Trace amounts of Al and S that leached out to the culture medium from APA prepared in concentrated sulfuric acid did not affect the antibacterial activity of APA, indicating that the APA surface exhibits excellent antibacterial activity. It was shown that the surface of APA prepared in concentrated sulfuric acid had excellent culture properties for fibroblasts while exhibiting antibacterial activity. APA prepared in concentrated sulfuric acid can be used in various applications that require excellent antibacterial activity as well as on surfaces that suppress bacterial growth and selectively cultivate target cells.

Mechanobactericidal nanotopographies for food industry: A promising strategy for eradicating foodborne pathogens - progress and challenges

Nowadays, food preservation, quality maintenance, and safety are major emerging concerns in the food industry. Methods for removing pathogens from the outside surfaces of food products would be an effective way to prevent bacterial contamination. Nanotopographies found on natural surfaces have been shown to mechanically damage the membranes of foodborne bacteria. Thus, using bioinspired mechanobactericidal nanostructures in food packaging and processing materials has the potential to lower surface bacterial contamination while increasing food safety. However, putting this concept into practice remains a challenge. This review discussed recent advances in understanding mechanobactericidal mechanisms, issues concerning the durability of nanotopography under external forces, and the scalability of nanostructures over larger areas. Furthermore, this review provides insight into critical research on the long-term efficiency of mechanobactericidal nanostructures and their potential for implementation in the food industry.

2-D transition metal trichalcophosphogenide FePS3 against multi-drug resistant microbial infections

Antimicrobial resistance (AMR) is a significant concern to society as it threatens the effectiveness of antibiotics and leads to increased morbidity and mortality rates. Innovative approaches are urgently required to address this challenge. Among promising solutions, two dimensional (2-D) nanomaterials with layered crystal structures have emerged as potent antimicrobial agents owing to their unique physicochemical properties. This antimicrobial activity is largely attributed to their high surface area, which allows for efficient interaction with microbial cell membranes, leading to physical disruption or oxidative stress through the generation of reactive oxygen species (ROS). The latter mechanism is particularly noteworthy as it involves the degradation of these nanomaterials under specific conditions, releasing ROS that can effectively kill bacteria and other pathogens without harming human cells. This study explores the antimicrobial properties of a novel biodegradable nanomaterial based on 2-D transition metal trichalcogenides, FePS3, as a potential solution to drug-resistant microbes. Our findings indicate that FePS3 is an exceptionally effective antimicrobial agent with over 99.9% elimination of various bacterial strains. Crucially, it exhibits no cytotoxic effects on mammalian cells, underscoring the potential for safe biomedical application. The primary mechanism driving the antimicrobial efficacy of FePS3 is the release of ROS during biodegradation. ROS has a crucial role in neutralizing bacterial cells, conferring significant antipathogenic properties to this compound. The unique combination of high antimicrobial activity, biocompatibility, and biodegradability makes FePS3 a promising candidate for developing new antimicrobial strategies. This research contributes to the increasing body of evidence supporting the use of 2-D nanomaterials in addressing the global challenge of AMR, offering a potential pathway for the development of advanced, effective, and safe antimicrobial agents.

A supervised machine learning tool to predict the bactericidal efficiency of nanostructured surface

The emergence and rapid spread of multidrug-resistant bacterial strains is a growing concern of public health. Inspired by the natural bactericidal surfaces of lotus leaves and shark skin, increasing attention has been focused on the use of mechano-bactericidal methods to create surfaces with antibacterial and/or bactericidal effects. There have been several studies exploring the bactericidal effect of nanostructured surfaces under various combinations of parameters. However, the correlation and synergies between these factors still need to be clarified. Recently machine learning (ML), which enables prediction or decision-making based on data, has been used in the field of biomaterials with promising results. In this study, we explored ML in nanotechnology to investigate the antimicrobial potential of nanostructured surfaces. A dataset of nanostructured surfaces and their antimicrobial properties was built by extracting the published literature. Based on the literature review and the distribution of our dataset, 70% bactericidal efficiency was selected as a practical benchmark for our classification model that balances stringent bactericidal performance with achievable targets in diverse conditions. Subsequently, we developed an ML classification model, which demonstrated an 81% accuracy in its predictive capability. A regression model was further developed to predict the value of bactericidal efficiency for nanostructured surfaces. Feature importance analysis of the ML models suggested that nanotopographical features have a greater influence on bactericidal properties than material properties, thus providing insight into the principles of the mechano-bactericidal effect of nanostructured surfaces. Overall, this ML model tool could help researchers to effectively select and design the parameters of the surface structure prior to experimentation, thereby improving the timeliness and reducing the number of experiments and the associated costs.

Advanced Antibacterial Strategies for Combatting Biomaterial-Associated Infections: A Comprehensive Review

Biomaterial-associated infections (BAIs) pose significant challenges in modern medical technologies, being a major postoperative complication and leading cause of implant failure. These infections significantly risk patient health, resulting in prolonged hospitalization, increased morbidity and mortality rates, and elevated treatment expenses. This comprehensive review examines the mechanisms driving bacterial adhesion and biofilm formation on biomaterial surfaces, offering an in-depth analysis of current antimicrobial strategies for preventing BAIs. We explore antimicrobial-eluting biomaterials, contact-killing surfaces, and antifouling coatings, emphasizing the application of antifouling polymer brushes on medical devices. Recent advancements in multifunctional antimicrobial biomaterials, which integrate multiple mechanisms for superior protection against BAIs, are also discussed. By evaluating the advantages and limitations of these strategies, this review aims to guide the design and development of highly efficient and biocompatible antimicrobial biomaterials. We highlight potential design routes that facilitate the transition from laboratory research to clinical applications. Additionally, we provide insights into the potential of synthetic biology as a novel approach to combat antimicrobial resistance. This review aspires to inspire future research and innovation, ultimately improving patient outcomes and advancing medical device technology.

Bioinspired oriented calcium phosphate nanocrystal arrays with bactericidal and osteogenic properties

The global diffusion of antibiotic resistance poses a severe threat to public health. Addressing antibiotic-resistant infections requires innovative approaches, such as antibacterial nanostructured surfaces (ANSs). These surfaces, featuring ordered arrays of nanostructures, exhibit the ability to kill bacteria upon contact. However, most currently developed ANSs utilize bioinert materials, lacking bioactivity crucial for promoting tissue regeneration, particularly in the context of bone infections. This study introduces ANSs composed of bioactive calcium phosphate nanocrystals. Two distinct ANSs were created through a biomineralization-inspired growth of amorphous calcium phosphate (ACP) precursors. The ANSs demonstrated efficient antibacterial properties against both Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) antibiotic resistant bacteria, with up to 75 % mortality in adhered bacteria after only 4 h of contact. Notably, the ANS featuring thinner and less oriented nano-needles exhibited superior efficacy attributed to simultaneous membrane rupturing and oxidative stress induction. Moreover, the ANSs facilitate the proliferation of mammalian cells, enhancing adhesion, spreading, and reducing oxidative stress. The ANSs displayed also significant bioactivity towards human mesenchymal stem cells, promoting colonization and inducing osteogenic differentiation. Specifically, the ANS with thicker and more ordered nano-needles demonstrated heightened effects. In conclusion, ANSs introduced in this work have the potential to serve as foundation for developing bone graft materials capable of eradicate site infections while concurrently stimulating bone regeneration. STATEMENT OF SIGNIFICANCE: Nanostructured surfaces with antibacterial properties through a mechano-bactericidal mechanism have shown significant potential in fighting antibiotic resistance. However, these surfaces have not been fabricated with bioactive materials necessary for developing devices that are both antibacterial and able to stimulate tissue regeneration. This study demonstrates the feasibility of creating nanostructured surfaces of ordered calcium phosphate nano-needles through a biomineralization-inspired growth. These surfaces exhibit dual functionality, serving as effective bactericidal agents against Gram-negative and Gram-positive antibiotic-resistant bacteria while also promoting the proliferation of mammalian cells and inducing osteogenic differentiation of human mesenchymal stem cells. Consequently, this approach holds promise in the context of bone infections, introducing innovative nanostructured surfaces that could be utilized in the development of antimicrobial and osteogenic grafts.

Dual Antibacterial Properties of Copper-Coated Nanotextured Stainless Steel

Bacterial adhesion to stainless steel, an alloy commonly used in shared settings, numerous medical devices, and food and beverage sectors, can give rise to serious infections, ultimately leading to morbidity, mortality, and significant healthcare expenses. In this study, Cu-coated nanotextured stainless steel (nSS) fabrication have been demonstrated using electrochemical technique and its potential as an antibiotic-free biocidal surface against Gram-positive and negative bacteria. As nanotexture and Cu combine for dual methods of killing, this material should not contribute to drug-resistant bacteria as antibiotic use does. This approach involves applying a Cu coating on nanotextured stainless steel, resulting in an antibacterial activity within 30 min. Comprehensive characterization of the surface revealing that the Cu coating consists of metallic Cu and oxidized states (Cu2+ and Cu+), has been performed by this study. Cu-coated nSS induces a remarkable reduction of 97% in Gram-negative Escherichia coli and 99% Gram-positive Staphylococcus epidermidis bacteria. This material has potential to be used to create effective, scalable, and sustainable solutions to prevent bacterial infections caused by surface contamination without contributing to antibiotic resistance.

Recent advances in essential oils and their nanoformulations for poultry feed

Antibiotics in poultry feed to boost growth performance are becoming increasingly contentious due to concerns over antimicrobial resistance development. Essential oils (EOs), as natural, plant-derived compounds, have demonstrated antimicrobial and antioxidant properties. EOs may potentially improve poultry health and growth performance when included in poultry feed. Nevertheless, the incorporation of EOs as nutritional additives is hindered by their high volatility, low water solubility, poor intestinal absorption, and sensitivity to environmental conditions. Recently, nanoencapsulation strategies using nanoformulations have emerged as a potential solution to these challenges, improving the stability and bioavailability of EOs, and enabling targeted delivery in poultry feed. This review provides an overview of the antioxidant and antibacterial properties of EOs, the current limitations of their applications in poultry feed, and the recent advancements in nano-engineering to overcome these limitations. Furthermore, we outline the potential future research direction on EO nanoformulations, emphasizing their promising role in advancing sustainable poultry nutrition.Highlights• Essential oils (EOs) are known as powerful antioxidants and antibacterial agents.• EOs have a high potential to replace antibiotics as feed additives.• Nanoformulations of EOs have shown improved bioactivity and storage stability of EOs.• Nanoformulation promotes the bioavailability and gut adsorption of EOs as feed additives.

Addressing the healthcare waste management barriers: A structural equation modeling approach

Due to the growing population and advancing economy, medical waste accumulation has come to the attention of all facets of society. Although the issue of medical waste management planning has been addressed in developed nations, it still exists in several developing nations. This paper examines the effects of barriers under the Organization action, work handling, and Human Resource Practices section on the healthcare waste management (HCWM) sector in a developing country India. In this study, three hypotheses were constructed and tested using Structural equation modeling. The questionnaire was distributed among 200 health professionals to collect their responses. Ninety-seven responses were received, and 15 barriers were identified affecting the healthcare waste management sector. The results show that all three barriers (i.e., Organizational, Waste handling, and Human resources) hinder the Healthcare waste management sector. Organizational Barriers are the most significant among other barriers. So, the hospitals have to take appropriate actions to overcome these barriers. This paper helps to complete the research gap by providing the different characteristics of barriers. The development of a model for the analysis of barriers influencing HCWM is the Author's original contribution.

Enhancing Bactericidal Properties of Ti6Al4V Surfaces through Micro and Nano Hierarchical Laser Texturing

Orthopedic and dental implants made from Ti6Al4V are widely used due to their excellent mechanical properties and biocompatibility. However, the long-term performance of these implants can be compromised by bacterial infections. This study explores the development of hierarchically textured surfaces with enhanced bactericidal properties to address such challenges. Hierarchical surface structures were developed by combining microscale features produced by a microsecond laser and superimposed submicron features produced using a femtosecond laser. Microscale patterns were produced by the pulsed laser surface melting process, whereas submicrometer laser-induced periodic surface structures were created on top of them by femtosecond laser processing. Escherichia coli bacterial cells were cultured on the textured surface. After 24 h, a staining analysis was performed using SYTO9 and PI dyes to investigate the samples with a confocal microscope for live dead assays. Results showed bacterial colony formation onto the microscale surface textures with live bacterial cells, whereas the hierarchical surface textures display segregated and physically damaged bacterial cell attachments on surfaces. The hierarchical surface textures showed ∼98% dead bacterial cells due to the combined effect of its multiscale surface features and oxide formation during the laser processing steps. The efficacy of hierarchical surface textures in enhancing the antibacterial behavior of Ti6Al4V implants is evident from the conducted research. Such laser-based surface treatments can find potential applications in different industrial sectors.

Optimizing alkaline hydrothermal treatment for biomimetic smart metallic orthopedic and dental implants

Orthopedic and dental implant failure continues to be a significant concern due to localized bacterial infections. Previous studies have attempted to improve implant surfaces by modifying their texture and roughness or coating them with antibiotics to enhance antibacterial properties for implant longevity. However, these approaches have demonstrated limited effectiveness. In this study, we attempted to engineer the titanium (Ti) alloy surface biomimetically at the nanometer scale, inspired by the cicada wing nanostructure using alkaline hydrothermal treatment (AHT) to simultaneously confer antibacterial properties and support the adhesion and proliferation of mammalian cells. The two modified Ti surfaces were developed using a 4 h and 8 h AHT process in 1 N NaOH at 230 °C, followed by a 2-hour post-calcination at 600 °C. We found that the control plates showed a relatively smooth surface, while the treatment groups (4 h & 8 h AHT) displayed nanoflower structures containing randomly distributed nano-spikes. The results demonstrated a statistically significant decrease in the contact angle of the treatment groups, which increased wettability characteristics. The 8 h AHT group exhibited the highest wettability and significant increase in roughness 0.72 ± 0.08 µm (P < 0.05), leading to more osteoblast cell attachment, reduced cytotoxicity effects, and enhanced relative survivability. The alkaline phosphatase activity measured in all different groups indicated that the 8 h AHT group exhibited the highest activity, suggesting that the surface roughness and wettability of the treatment groups may have facilitated cell adhesion and attachment and subsequently increased secretion of extracellular matrix. Overall, the findings indicate that biomimetic nanotextured surfaces created by the AHT process have the potential to be translated as implant coatings to enhance bone regeneration and implant integration.

Bioinspired Nanotopography for Combinatory Osseointegration and Antibacterial Therapy

The ongoing global health has highlighted the critical issue of secondary infections, particularly antibiotic-resistant bacterial infections, which have been significant contributors to mortality rates. Orthopedic implants, while essential for trauma and orthopedic surgeries, are particularly susceptible to these infections, leading to severe complications and economic burdens. The traditional use of antibiotics in treating these infections poses further challenges including the risk of developing antibiotic-resistant bacteria. This study introduces a novel approach to combat this issue by developing nanostructured surfaces for orthopedic implants using target ion-induced plasma sputtering. Inspired by the natural design of dragonfly wings, these surfaces aim to prevent bacterial adhesion while promoting preosteoblast activity, offering a dual-function solution to the problems of bacterial infection and implant integration without relying on antibiotics. The in vitro results demonstrate the effectiveness of these bioinspired surfaces in eradicating bacteria and supporting cell proliferation and differentiation, presenting a promising alternative for the development of biomedical implants.

Enhancing the Biological Performance of Titanium Alloy through In Situ Modulation of the Surface Nanostructure: Near-Infrared-Responsive Antibacterial Function and Osteoinductivity

The poor clinical performance of titanium and its alloy implants is mainly attributed to their lack of antibacterial ability and poor osseointegration. The key and challenge lie in how to enhance their osteoinductivity while imparting antibacterial capability. In this study, a titanium oxide metasurface with light-responsive behavior was constructed on the surface of titanium alloy using an alkaline-acid bidirectional hydrothermal method. The effects of the acid type, acid concentration, hydrothermal time, hydrothermal temperature, and subsequent heat treatments on the optical behavior of the metasurface were systematically investigated with a focus on exploring the influence of the metasurface and photodynamic reaction on the osteogenic activity of osteoblasts. Results show that the type of acid and heat treatment significantly affect the light absorption of the titanium alloy surface, with HCl and post-heat-treatment favoring redshift in the light absorption. Under 808 nm near-infrared (NIR) irradiation for 10 min, in vitro antibacterial experiments demonstrate that the antibacterial rate of the metasurface titanium alloy against Staphylococcus aureus and Escherichia coli were 96.87% and 99.27%, respectively. In vitro cell experiments demonstrate that the nanostructure facilitates cell adhesion, proliferation, differentiation, and expression of osteogenic-related genes. Surprisingly, the nanostructure promoted the expression of relevant osteogenic genes of MC3T3-E1 under 808 nm NIR irradiation. This study provides a method for the surface modification of titanium alloy implants.

Bacterial Surface Appendages Modulate the Antimicrobial Activity Induced by Nanoflake Surfaces on Titanium

Bioinspired nanotopography is a promising approach to generate antimicrobial surfaces to combat implant-associated infection. Despite efforts to develop bactericidal 1D structures, the antibacterial capacity of 2D structures and their mechanism of action remains uncertain. Here, hydrothermal synthesis is utilized to generate two 2D nanoflake surfaces on titanium (Ti) substrates and investigate the physiological effects of nanoflakes on bacteria. The nanoflakes impair the attachment and growth of Escherichia coli and trigger the accumulation of intracellular reactive oxygen species (ROS), potentially contributing to the killing of adherent bacteria. E. coli surface appendages type-1 fimbriae and flagella are not implicated in the nanoflake-mediated modulation of bacterial attachment but do influence the bactericidal effects of nanoflakes. An E. coli ΔfimA mutant lacking type-1 fimbriae is more susceptible to the bactericidal effects of nanoflakes than the parent strain, while E. coli cells lacking flagella (ΔfliC) are more resistant. The results suggest that type-1 fimbriae confer a cushioning effect that protects bacteria upon initial contact with the nanoflake surface, while flagella-mediated motility can lead to elevated membrane abrasion. This finding offers a better understanding of the antibacterial properties of nanoflake structures that can be applied to the design of antimicrobial surfaces for future medical applications.

Preparation, biological activity and antibacterial properties of tantalum surface-doped Ca2+/Zn2+nanorods

In this research, we utilize porous tantalum, known for its outstanding elastic modulus and biological properties, as a base material in biomedical applications. The human skeletal system is rich in elements like Ca and Zn. The role of Zn is crucial for achieving a spectrum of sterilizing effects, while Ca is known to effectively enhance cell differentiation and boost cellular activity. The focus of this study is the modification of porous tantalum using a hydrothermal method to synthesize Ca2+/Zn2+-doped Ta2O5nanorods. These nanorods are subjected to extensive characterization techniques to confirm their structure and composition. Additionally, their biological performance is evaluated through a range of tests, including antibacterial assessments, MTT assays, and bacteria/cell scanning electron microscopy (SEM) analyses. The objective is to determine the most effective method of surface modification for porous tantalum, thereby laying a foundational theoretical framework for its surface enhancement.

MoOxNWs with mechanical damage - oriented synergistic photothermal / photodynamic therapy for highly effective treating wound infections

Reactive oxygen species (ROS)-based therapy has emerged as a promising antibacterial strategy. However, it faces the limitations of uncontrollable space-time release and excessive lipid peroxidation, which may lead to a series of metabolic disorders and decreased immune function. In this study, mechanical damage by molybdenum oxide nanowires (MoOxNWs) is introduced as a synergistic factor to enhance the photothermal and photodynamic effects for controllable and efficient antibacterial therapy. Through their sharp ends, the nanowires can effectively pierce and damage the bacterial cells, thus facilitating the entry of externally generated ROS into the cells. The ROS are generated via photodynamic effect of the nanowires under a mere 5 min of near-infrared light irradiation. This approach enhances the photothermal (by 27.3 %) and photodynamic properties of ROS generation. MoOxNWs (100 μg·mL-1) achieve sterilisation rates of 97.67 % for extended-spectrum β-lactamase-producing E. coli and 96.34 % for methicillin-resistant Staphylococcus aureus, which are comparable or even exceeding the efficacy of most MoOx-based antibacterial agents. Moreover, they exhibit good biocompatibility and low in vivo toxicity.

Interdisciplinary-Inspired Smart Antibacterial Materials and Their Biomedical Applications

The discovery of antibiotics has saved millions of lives, but the emergence of antibiotic-resistant bacteria has become another problem in modern medicine. To avoid or reduce the overuse of antibiotics in antibacterial treatments, stimuli-responsive materials, pathogen-targeting nanoparticles, immunogenic nano-toxoids, and biomimetic materials are being developed to make sterilization better and smarter than conventional therapies. The common goal of smart antibacterial materials (SAMs) is to increase the antibiotic efficacy or function via an antibacterial mechanism different from that of antibiotics in order to increase the antibacterial and biological properties while reducing the risk of drug resistance. The research and development of SAMs are increasingly interdisciplinary because new designs require the knowledge of different fields and input/collaboration from scientists in different fields. A good understanding of energy conversion in materials, physiological characteristics in cells and bacteria, and bactericidal structures and components in nature are expected to promote the development of SAMs. In this review, the importance of multidisciplinary insights for SAMs is emphasized, and the latest advances in SAMs are categorized and discussed according to the pertinent disciplines including materials science, physiology, and biomimicry.

Quantification of Enzymatic Biofilm Removal Using the Sauerbrey Equation: Application to the Case of Pseudomonas protegens

A methodology for the quantitative analysis of enzymatic removal of biofilms (BF) was developed, based on a quartz crystal microbalance (QCM) under stationary conditions. This was applied to the case of Pseudomonas protegens (PP) BFs, through a series of five enzymes, whose removal activity was screened using the presented methodology. The procedure is based on the following: when BFs can be modeled as rigid materials, QCM can be used as a balance under stationary conditions for determining the BFs mass reduction by enzymatic removal. For considering a BF as a rigid model, energy dissipation effects, associated with viscoelastic properties of the BF, must be negligible. Hence, a QCM system with detection of dissipation (referred to as QCM with dissipation) was used for evaluating the energy losses, which, in fact, resulted in negligible energy losses in the case of dehydrated PP BFs, validating the application of the Sauerbrey equation for the change of mass calculations. The stationary methodology reduces operating times and simplifies data analysis in comparison to dynamic approaches based on flow setups, which requires the incorporation of dissipation effects due to the liquid media. By carrying out QCM, glycosidase-type enzymes showed BF removal higher than 80% at enzyme concentration 50 ppm, reaching removal over 90% in the cases of amylase and cellulase/xylanase enzymes. The highest removal percentage produced a reduction from about 15 to 1 μg in the BF mass. Amylase enzyme was tested from below 50 to 1 ppm, reaching around 60% of removal at 1 ppm. The obtained results were supported by other instrumental techniques such as Raman spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, high performance anion exchange chromatography, thermogravimetric analysis, and differential scanning calorimetry. The removal quantifications obtained with QCM were compared with those obtained by well-established screening techniques (UV-vis spectrophotometry using crystal violet and agar diffusion test). The proposed methodology expands the possibility of using a quartz microbalance to perform enzymatic activity screening.

Bioinspired Hierarchical Self-Assembled Nanozyme for Efficient Antibacterial Treatment

Along with the rapid development and ever-deepening understanding of nanoscience and nanotechnology, nanomaterials hold promise to mimic the highly evolved biological exquisite nanostructures and sophisticated functions. Here, inspired by the ubiquitous antibacterial nanostructures on the wing surfaces of some insects, a NiCo2 O4 nanozyme with self-adaptive hierarchical nanostructure is developed that can capture bacteria of various morphotypes via the physico-mechanical interaction between the nanostructure and bacteria. Moreover, the developed biomimetic nanostructure further exhibits superior peroxidase-like catalytic activity, which can catalytically generate highly toxic reactive oxygen species that disrupt bacterial membranes and induce bacterial apoptosis. Therefore, the mechano-catalytic coupling property of this NiCo2 O4 nanozyme allows for an extensive and efficient antibacterial application, with no concerns of antimicrobial resistance. This work suggests a promising strategy for the rational design of advanced antibacterial materials by mimicking biological antibiosis.

Tackling catheter-associated urinary tract infections with next-generation antimicrobial technologies

Urinary catheters and other medical devices associated with the urinary tract such as stents are major contributors to nosocomial urinary tract infections (UTIs) as they provide an access path for pathogens to enter the bladder. Considering that catheter-associated urinary tract infections (CAUTIs) account for approximately 75% of UTIs and that UTIs represent the most common type of healthcare-associated infections, novel anti-infective device technologies are urgently required. The rapid rise of antimicrobial resistance in the context of CAUTIs further highlights the importance of such preventative strategies. In this review, the risk factors for pathogen colonization in the urinary tract are dissected, taking into account the nature and mechanistics of this unique environment. Moreover, the most promising next-generation preventative strategies are critically assessed, focusing in particular on anti-infective surface coatings. Finally, emerging approaches in this field and their likely clinical impact are examined.

Effects of Surface Topography and Cellular Biomechanics on Nanopillar-Induced Bactericidal Activity

Bacteria are mechanically resistant biological structures that can sustain physical stress. Experimental data, however, have shown that high-aspect-ratio nanopillars deform bacterial cells upon contact. If the deformation is sufficiently large, it lyses the bacterial cell wall, ultimately leading to cell death. This has prompted a novel strategy, known as mechano-bactericide technology, to fabricate antibacterial surfaces. Although adhesion forces were originally proposed as the driving force for mechano-bactericidal action, it has been recently shown that external forces, such as capillary forces arising from an air-water interface at bacterial surfaces, produce sufficient loads to rapidly kill bacteria on nanopillars. This discovery highlights the need to theoretically examine how bacteria respond to external loads and to ascertain the key factors. In this study, we developed a finite element model approximating bacteria as elastic shells filled with cytoplasmic fluid brought into contact with an individual nanopillar or nanopillar array. This model elucidates that bacterial killing caused by external forces on nanopillars is influenced by surface topography and cell biomechanical variables, including the density and arrangement of nanopillars, in addition to the cell wall thickness and elastic modulus. Considering that surface topography is an important design parameter, we performed experiments using nanopillar arrays with precisely controlled nanopillar diameters and spacing. Consistent with model predictions, these demonstrate that nanopillars with a larger spacing increase bacterial susceptibility to mechanical puncture. The results provide salient insights into mechano-bactericidal activity and identify key design parameters for implementing this technology.

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.

3D stem cell spheroids with urchin-like hydroxyapatite microparticles enhance osteogenesis of stem cells

Cell therapy (also known as cell transplantation) has been considered promising as a next-generation living-cell therapy strategy to surpass the effects of traditional drugs. However, their practical clinical uses and product conversion are hampered by the unsatisfied viability and efficacy of the transplanted cells. Herein, we propose a synergistic enhancement strategy to address these issues by constructing 3D stem cell spheroids integrated with urchin-like hydroxyapatite microparticles (uHA). Specifically, cell-sized uHA microparticles were synthesized via a simple hydrothermal method using glutamic acid (Glu, E) as the co-template with good biocompatibility and structural antimicrobial performance (denoted as E-uHA). Combining with a hanging drop method, stem cell spheroids integrated with E-uHA were successfully obtained by culturing bone marrow mesenchymal stem cells (BMSCs) with a low concentration of the E-uHA suspensions (10 μg mL-1). The resulting composite spheroids of BMSCs/E-uHA deliver a high cellular viability, migration activity, and a superior osteogenic property compared to the 2D cultured counterpart or other BMSC spheroids. This work provides an effective strategy for integrating a secondary bio-functional component into stem cell spheroids for designing more cell therapy options with boosted cellular viability and therapeutic effect.

Cell Adhesion, Elasticity, and Rupture Forces Guide Microbial Cell Death on Nanostructured Antimicrobial Titanium Surfaces

Naturally occurring and synthetic nanostructured surfaces have been widely reported to resist microbial colonization. The majority of these studies have shown that both bacterial and fungal cells are killed upon contact and subsequent surface adhesion to such surfaces. This occurs because the presence of high-aspect-ratio structures can initiate a self-driven mechanical rupture of microbial cells during the surface adsorption process. While this technology has received a large amount of scientific and medical interest, one important question still remains: what factors drive microbial death on the surface? In this work, the interplay between microbial-surface adhesion, cell elasticity, cell membrane rupture forces, and cell lysis at the microbial-nanostructure biointerface during adsorptive processes was assessed using a combination of live confocal laser scanning microscopy, scanning electron microscopy, in situ amplitude atomic force microscopy, and single-cell force spectroscopy. Specifically, the adsorptive behavior and nanomechanical properties of live Gram-negative (Pseudomonas aeruginosa) and Gram-positive (methicillin-resistant Staphylococcus aureus) bacterial cells, as well as the fungal species Candida albicans and Cryptococcus neoformans, were assessed on unmodified and nanostructured titanium surfaces. Unmodified titanium and titanium surfaces with nanostructures were used as model substrates for investigation. For all microbial species, cell elasticity, rupture force, maximum cell-surface adhesion force, the work of adhesion, and the cell-surface tether behavior were compared to the relative cell death observed for each surface examined. For cells with a lower elastic modulus, lower force to rupture through the cell, and higher work of adhesion, the surfaces had a higher antimicrobial activity, supporting the proposed biocidal mode of action for nanostructured surfaces. This study provides direct quantification of the differences observed in the efficacy of nanostructured antimicrobial surface as a function of microbial species indicating that a universal, antimicrobial surface architecture may be hard to achieve.

Research progress of biomimetic materials in oral medicine

Biomimetic materials are able to mimic the structure and functional properties of native tissues especially natural oral tissues. They have attracted growing attention for their potential to achieve configurable and functional reconstruction in oral medicine. Though tremendous progress has been made regarding biomimetic materials, significant challenges still remain in terms of controversy on the mechanism of tooth tissue regeneration, lack of options for manufacturing such materials and insufficiency of in vivo experimental tests in related fields. In this review, the biomimetic materials used in oral medicine are summarized systematically, including tooth defect, tooth loss, periodontal diseases and maxillofacial bone defect. Various theoretical foundations of biomimetic materials research are reviewed, introducing the current and pertinent results. The benefits and limitations of these materials are summed up at the same time. Finally, challenges and potential of this field are discussed. This review provides the framework and support for further research in addition to giving a generally novel and fundamental basis for the utilization of biomimetic materials in the future.

Development of antibacterial neural stimulation electrodes via hierarchical surface restructuring and atomic layer deposition

Miniaturization and electrochemical performance enhancement of electrodes and microelectrode arrays in emerging long-term implantable neural stimulation devices improves specificity, functionality, and performance of these devices. However, surgical site and post-implantation infections are amongst the most devastating complications after surgical procedures and implantations. Additionally, with the increased use of antibiotics, the threat of antibiotic resistance is significant and is increasingly being recognized as a global problem. Therefore, the need for alternative strategies to eliminate post-implantation infections and reduce antibiotic use has led to the development of medical devices with antibacterial properties. In this work, we report on the development of electrochemically active antibacterial platinum-iridium electrodes targeted for use in neural stimulation and sensing applications. A two-step development process was used. Electrodes were first restructured using femtosecond laser hierarchical surface restructuring. In the second step of the process, atomic layer deposition was utilized to deposit conformal antibacterial copper oxide thin films on the hierarchical surface structure of the electrodes to impart antibacterial properties to the electrodes with minimal impact on electrochemical performance of the electrodes. Morphological, compositional, and structural properties of the electrodes were studied using multiple modalities of microscopy and spectroscopy. Antibacterial properties of the electrodes were also studied, particularly, the killing effect of the hierarchically restructured antibacterial electrodes on Escherichia coli and Staphylococcus aureus-two common types of bacteria responsible for implant infections.

Carbon-infiltrated carbon nanotubes inhibit the development of Staphylococcus aureus biofilms

Staphylococcus aureus forms biofilms that cause considerable morbidity and mortality in patients who receive implanted devices such as prosthetics or fixator pins. An ideal surface for such medical devices would inhibit biofilm growth. Recently, it was reported that surface modification of stainless steel materials with carbon-infiltrated carbon nanotubes (CICNT) inhibits the growth of S. aureus biofilms. The purpose of this study was to investigate this antimicrobial effect on titanium materials with CICNT coated surfaces in a variety of surface morphologies and across a broader spectrum of S. aureus isolates. Study samples of CICNT-coated titanium, and control samples of bare titanium, a common implant material, were exposed to S. aureus. Viable bacteria were removed from adhered biofilms and quantified as colony forming units. Scanning electron microscopy was used to qualitatively analyze biofilms both before and after removal of cells. The CICNT surface was found to have significantly fewer adherent bacteria than bare titanium control surfaces, both via colony forming unit and microscopic analyses. This effect was most pronounced on CICNT surfaces with an average nanotube diameter of 150 nm, showing a 2.5-fold reduction in adherent bacteria. Since S. aureus forms different biofilm structures by isolate and by growth conditions, we tested 7 total isolates and found a significant reduction in the biofilm load in six out of seven S. aureus isolates tested. To examine whether the anti-biofilm effect was due to the structure of the nanotubes, we generated an unstructured carbon surface. Significantly more bacteria adhered to a nonstructured carbon surface than to the 150 nm CICNT surface, suggesting that the topography of the nanotube structure itself has anti-biofilm properties. The CICNT surface possesses anti-biofilm properties that result in fewer adherent S. aureus bacteria. These anti-biofilm properties are consistent across multiple isolates of S. aureus and are affected by nanotube diameter. The experiments performed in this study suggest that this effect is due to the nanostructure of the CICNT surface.

Recent Advances in Dual-Function Superhydrophobic Antibacterial Surfaces

Bacterial adhesion and subsequent biofilm formation on the surfaces of synthetic materials imposes a significant burden in various fields, which can lead to infections in patients or reduce the service life of industrial devices. Therefore, there is increasing interest in imbuing surfaces with antibacterial properties. Bioinspired superhydrophobic surfaces with high water contact angles (>150°) exhibit excellent surface repellency against contaminations, thereby preventing initial bacterial adhesion and inhibiting biofilm formation. However, conventional superhydrophobic surfaces typically lack long-term durability and are incapable of achieving persistent efficacy against bacterial adhesion. To overcome these limitations, in recent decades, dual-function superhydrophobic antibacterial surfaces with both bacteria-repelling and bacteria-killing properties have been developed by introducing bactericidal components. These surfaces have demonstrated improved long-term antibacterial performance in addressing the issues associated with surface-attached bacteria. This review summarizes the recent advancements of these dual-function superhydrophobic antibacterial surfaces. First, a brief overview of the fabrication strategies and bacteria-repelling mechanism of superhydrophobic surfaces is provided and then the dual-function superhydrophobic antibacterial surfaces are classified into three types based on the bacteria-killing mechanism: i) mechanotherapy, ii) chemotherapy, and iii) phototherapy. Finally, the limitations and challenges of current research are discussed and future perspectives in this promising area are proposed.

Progress in Nanostructured Mechano-Bactericidal Polymeric Surfaces for Biomedical Applications

Bacterial infections and antibiotic resistance remain significant contributors to morbidity and mortality worldwide. Despite recent advances in biomedical research, a substantial number of medical devices and implants continue to be plagued by bacterial colonisation, resulting in severe consequences, including fatalities. The development of nanostructured surfaces with mechano-bactericidal properties has emerged as a promising solution to this problem. These surfaces employ a mechanical rupturing mechanism to lyse bacterial cells, effectively halting subsequent biofilm formation on various materials and, ultimately, thwarting bacterial infections. This review delves into the prevailing research progress within the realm of nanostructured mechano-bactericidal polymeric surfaces. It also investigates the diverse fabrication methods for developing nanostructured polymeric surfaces with mechano-bactericidal properties. We then discuss the significant challenges associated with each approach and identify research gaps that warrant exploration in future studies, emphasizing the potential for polymeric implants to leverage their distinct physical, chemical, and mechanical properties over traditional materials like metals.

Chemoselective Coatings of GL13K Antimicrobial Peptides for Dental Implants

Dental implant-associated infection is a clinical challenge which poses a significant healthcare and socio-economic burden. To overcome this issue, developing antimicrobial surfaces, including antimicrobial peptide coatings, has gained great attention. Different physical and chemical routes have been used to obtain these biofunctional coatings, which in turn might have a direct influence on their bioactivity and functionality. In this study, we present a silane-based, fast, and efficient chemoselective conjugation of antimicrobial peptides (Cys-GL13K) to coat titanium implant surfaces. Comprehensive surface analysis was performed to confirm the surface functionalization of as-prepared and mechanically challenged coatings. The antibacterial potency of the evaluated surfaces was confirmed against both Streptococcus gordonii and Streptococcus mutans, the primary colonizers and pathogens of dental surfaces, as demonstrated by reduced bacteria viability. Additionally, human dental pulp stem cells demonstrated long-term viability when cultured on Cys-GL13K-grafted titanium surfaces. Cell functionality and antimicrobial capability against multi-species need to be studied further; however, our results confirmed that the proposed chemistry for chemoselective peptide anchoring is a valid alternative to traditional site-unspecific anchoring methods and offers opportunities to modify varying biomaterial surfaces to form potent bioactive coatings with multiple functionalities to prevent infection.

Bioactivity and antibacterial properties of zinc-doped Ta2O5nanorods on porous tantalum surface

This paper focuses on the preparation of Zn2+-doped Ta2O5nanorods on porous tantalum using the hydrothermal method. Porous tantalum is widely used in biomedical materials due to its excellent elastic modulus and biological activity. Porous tantalum has an elastic modulus close to that of human bone, and its large specific surface area is conducive to promoting cell adhesion. Zinc is an important component of human bone, which not only has spectral bactericidal properties, but also has no cytotoxicity. The purpose of this study is to provide a theoretical basis for the surface modification of porous tantalum and to determine the best surface modification method. The surface structure of the sample was characterized by x-ray diffractometer, x-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, and the Zn-doped Ta2O5nanorods are characterized by antibacterial test, MTT test, ICP and other methods. The sample has good antibacterial properties and no cytotoxicity. The results of this study have potential implications for the development of new and improved biomedical materials.

Laser textured Ti-6Al-7Nb alloy for biomedical applications: An investigation of texturing parameters on surface properties

Surface texturing with a laser beam is an effective method for engraving on the surface of biomaterials. The four laser texturing parameters (scan speed, frequency, fill spacing, and pulse width) having five different values were associated with five different scanning strategies (scan direction), and a total of 25 texturing conditions were tested on the Ti-6Al-7Nb alloy surface. The surface roughness and wettability of the textures created with a 20 W nanosecond fiber laser with a wavelength of 1064 nm on the surface of Ti-6Al-7Nb biocompatible alloy were investigated. Laser texturing parameters were analyzed according to the lowest surface roughness and a hydrophilic surface by creating L25 orthogonal arrays. The surface roughness values ranged between 2 and 26 µm. The lowest surface roughness with a value of 2.21 µm was achieved when the texture was processed with a frequency of 150 kHz, a fill spacing of 0.02 mm, a scan speed of 800 mm/s, a pulse width of 250 ns, and a cross-hatch strategy of 0°/90°. Considering the wettability test results, it was revealed that most of the textured surfaces have super hydrophilic and hydrophilic characteristics except the surface with a contact angle of 92.93°. The relevant surface was textured with 75 kHz frequency, 1000 mm/s scan speed, 0.05 mm fill spacing, 200 ns pulse width, and 45°/-45° cross-hatch strategy.

Nano-Biotechnology for Bacteria Identification and Potent Anti-bacterial Properties: A Review of Current State of the Art

Sepsis is a critical disease caused by the abrupt increase of bacteria in human blood, which subsequently causes a cytokine storm. Early identification of bacteria is critical to treating a patient with proper antibiotics to avoid sepsis. However, conventional culture-based identification takes a long time. Polymerase chain reaction (PCR) is not so successful because of the complexity and similarity in the genome sequence of some bacterial species, making it difficult to design primers and thus less suitable for rapid bacterial identification. To address these issues, several new technologies have been developed. Recent advances in nanotechnology have shown great potential for fast and accurate bacterial identification. The most promising strategy in nanotechnology involves the use of nanoparticles, which has led to the advancement of highly specific and sensitive biosensors capable of detecting and identifying bacteria even at low concentrations in very little time. The primary drawback of conventional antibiotics is the potential for antimicrobial resistance, which can lead to the development of superbacteria, making them difficult to treat. The incorporation of diverse nanomaterials and designs of nanomaterials has been utilized to kill bacteria efficiently. Nanomaterials with distinct physicochemical properties, such as optical and magnetic properties, including plasmonic and magnetic nanoparticles, have been extensively studied for their potential to efficiently kill bacteria. In this review, we are emphasizing the recent advances in nano-biotechnologies for bacterial identification and anti-bacterial properties. The basic principles of new technologies, as well as their future challenges, have been discussed.

Time-dependent plastic behavior of bacteria leading to rupture

A study of the mechanical response of bacteria is essential in designing an antibacterial surface for implants and food packaging applications. This research evaluated the mechanical response of Escherichia coli under different loading conditions. Indentation and prolonged creep tests were performed to understand their viscoelastic-plastic response. The results indicate that varying loading rates from 1 μm/s to 5 μm/s show an increase in modulus of 182% and 90%, calculated in the loading and unloading cycles, respectively, and a decrease in adhesion force by 42%. However, on varying loads from 5 nN to 25 nN, nominal change is observed in both modulus and adhesion force. The rupture curve at 100 nN load shows elastic and a small plastic deformation accompanied by a sharp peak indicating the cell wall rupture. The rupture force at the peak was found to be 34.38 ± 5.15 nN, irrespective of the loading rate, making it a failure criterion for bacteria rupture. The creep response of bacteria increases (for 6 s) and then remains constant (for 15 s) with time, indicating that a standard linear solid (SLS) model applies to this behavior. This work attempts to evaluate the mechanical properties of E. coli bacteria focusing on its rupture by contact killing mechanism.

An overview of SARS-CoV-2 transmission and engineering strategies to mitigate risk

The spread of the COVID-19 pandemic has profoundly affected every aspect of our lives. To date, experts have acknowledged that airborne transmission is a key piece of the SARS-CoV-2 puzzle. Nevertheless, the exact mechanism of airborne transmission of SARS-CoV-2 remains unclear. Recent works have shown the spreading of SARS-CoV-2 through numerical modeling and experimental works, but the successful applications of engineering approaches in reducing the spread of SARS-CoV-2 are lacking. In this review, the environmental factors that influence the transmission risk of SARS-CoV-2, such as ventilation flow rates, humidity, and temperature, are discussed. Besides, additional macro and micro weather factors, regional and global transmission, and the variants of the spread of SARS-CoV-2 are also reviewed. Engineering approaches that practically reduce the risks of SARS-CoV-2 transmissions are reported. Given the complex human behavior, environmental properties, and dynamic nature of the SARS-CoV-2 virus, it is reasonable to summarize that SARS-CoV-2 may not be eradicated even with the timely implementation of interventions. Therefore, more research exploring the potential cost-effective ways to control the transmission rate of SARS-CoV-2 may be a worthwhile pursuit to moderate the current crisis.

Study of Finite Element Simulation on the Mechano-Bactericidal Mechanism of Hierarchical Nanostructure Arrays

Biomimetic nanostructures with bactericidal performance have become the research focus in constructing sterilization surfaces, but the mechano-bactericidal mechanism is still not fully understood, especially for the hierarchical nanostructure arrays with different heights. Herein, the interaction between Escherichia coli cells and nanostructure arrays was simulated by finite element, and the initial rupture points, i.e., critical action sites, of bacterial cells and the effects of nanostructure geometries on the cell rupture speed were analyzed based on the mechano-response of Escherichia coli cells on flat (identical heights) and hierarchical nanostructure arrays. The critical action sites of bacterial cells on nanostructure arrays are all at the three-phase junction zone of cell-liquid-nanostructure, but they are slightly shifted by the height difference ΔH of nanostructures on hierarchical nanopillar (NP)/nanosheet (NS) arrays, where the NP is higher than the NS. When ΔH < 20 nm, the site nears the NS corners, and when ΔH ≥ 20 nm, the site is consistent with that of the NP/NP array, i.e., the site locates at the three-phase junction zone of cell-liquid-high NP. In addition, except for decreasing the NP diameter, the NS thickness/width, or properly increasing the nanostructure spacing, the cell rupture can be accelerated via increasing the ΔH of nanostructures. ΔH = 40 nm is distinguished as the boundary for the effect of nanostructure ΔH on the cell rupture speed. When ΔH < 40 nm, the cell rupture speed rapidly increases as the ΔH increases; when ΔH ≥ 40 nm, the cell rupture speed reaches the maximum value and remains stable. This study provides a new strategy on how to design high-efficiency bactericidal surfaces.