Picosecond Laser-Textured Stainless Steel Superhydrophobic Surface with an Antibacterial Adhesion Property

Dual-Layer Nanoengineered Urinary Catheters for Enhanced Antimicrobial Efficacy and Reduced Cytotoxicity

Catheter-associated urinary tract infection (CAUTI) is the most common healthcare-associated infection; however, current therapeutic strategies remain insufficient for standard clinical application. A novel urinary catheter featuring a dual-layer nanoengineering approach using zinc (Zn) and silver nanoparticles (AgNPs) is successfully fabricated. This design targets microbial resistance, minimizes cytotoxicity, and maintains long-term efficacy. The inner AgNPs layer provides immediate antibacterial effects against the UTI pathogens, while the outer porous Zn layer controls zero-order Ag release and generates reactive oxygen species, thus enhancing long-term bactericidal performance. Enhanced antibacterial properties of Zn/AgNPs-coated catheters are observed, resulting in 99.9% of E. coli and 99.7% of S. aureus reduction, respectively. The Zn/AgNPs-coated catheter significantly suppresses biofilm with sludge formation compared to AgNP-coated and uncoated catheters (all, p < 0.05). The Zn/AgNP-coated catheter in a rabbit model demonstrated a durable, effective barrier against bacterial colonization, maintaining antimicrobial properties during the catheter indwelling period with significantly reduced inflammation and epithelial disruption compared with AgNP and uncoated groups. This innovation has the potential to revolutionize the design of antimicrobial medical devices, particularly for applications requiring long-term implantation. Although further preclinical studies are required to verify its efficacy and safety, this strategy seems to be a promising approach to preventing CAUTI-related complications.

Mechanism of antibacterial property of micro scale rough surface formed by fine-particle bombarding

Fine-particle bombardment (FPB) is typically used to modify metal surfaces by bombarding them with fine particles at high speed. FPB is not a coating technique but is used for forming microscale concavities and convexities on a surface. Previously, we reported that an FPB-treated surface showed antibacterial effects; however, the underlying mechanisms remain unclear. We hypothesized that the pitch size of concavity and convexity, and irregular microscale pattern of FPB-treated surfaces might contribute to the antibacterial performance. In this study, we applied FPB to stainless-steel surfaces and evaluated the antibacterial effects of the FPB-treated surfaces based on ISO 22,196:2007. The FPB-treated surfaces exhibited antibacterial activity against Escherichia coli, with an antibacterial activity value (R) of two or more. Furthermore, our experiments suggest that the antibacterial mechanism of the FPB-treated surface can be attributed to increased oxidative stress in bacteria owing to physical stress from the rough surface. The antibacterial effect of FPB-treated surfaces offers an effective measure against drug-resistant bacteria.

Robust superhydrophobic cotton fabric based on dual-sized silica particles with self-healing nature

Improving the durability of wear-resistant superhydrophobic surfaces is crucial for their practical use. To tackle this, research is now delving into self-healing superhydrophobic surfaces. In our study, we developed superhydrophobic cotton fabrics by embedding nano-silica particles, micro-silica powder, and polydimethylsiloxane (PDMS) using a dipping method. This innovative design grants the SiO2/PDMS cotton fabric remarkable superhydrophobicity, reflected by a water contact angle of 155°. Moreover, the PDMS was stored in the amorphous areas of cellulose of cotton fabrics, attaching to the fiber surface and playing a role in connecting micro-blocks and nano-particles. This causes a self-diffusion of PDMS molecules in these fabrics, allowing the surface to regain its superhydrophobicity even after abrasion damage. Impressively, this self-healing property can be renewed at least 8 times, showcasing the fabric's resilience. Moreover, these superhydrophobic cotton fabrics exhibit outstanding self-cleaning abilities and repel various substances such as blood, milk, cola, and tea. This resilience, coupled with its simplicity, low cost-effectiveness, and eco-friendliness, makes this coating highly promising for applications across construction, chemical, and medical fields. Our study also delves into understanding the self-healing mechanism of the SiO2/PDMS cotton fabric, offering insights into their long-term performance and potential advancements in this field.

Construction of antibacterial bone implants and their application in bone regeneration

Bacterial infection represents a prevalent challenge during the bone repair process, often resulting in implant failure. However, the extensive use of antibiotics has limited local antibacterial effects at the infection site and is prone to side effects. In order to address the issue of bacterial infection during the transplantation of bone implants, four types of bone scaffold implants with long-term antimicrobial functionality have been constructed, including direct contact antimicrobial scaffold, dissolution-penetration antimicrobial scaffold, photocatalytic antimicrobial scaffold, and multimodal synergistic antimicrobial scaffold. The direct contact antimicrobial scaffold involves the physical penetration or disruption of bacterial cell membranes by the scaffold surface or hindrance of bacterial adhesion through surface charge, microstructure, and other factors. The dissolution-penetration antimicrobial scaffold releases antimicrobial substances from the scaffold's interior through degradation and other means to achieve local antimicrobial effects. The photocatalytic antimicrobial scaffold utilizes the absorption of light to generate reactive oxygen species (ROS) with enhanced chemical reactivity for antimicrobial activity. ROS can cause damage to bacterial cell membranes, deoxyribonucleic acid (DNA), proteins, and other components. The multimodal synergistic antimicrobial scaffold involves the combined use of multiple antimicrobial methods to achieve synergistic effects and effectively overcome the limitations of individual antimicrobial approaches. Additionally, the biocompatibility issues of the antimicrobial bone scaffold are also discussed, including in vitro cell adhesion, proliferation, and osteogenic differentiation, as well as in vivo bone repair and vascularization. Finally, the challenges and prospects of antimicrobial bone implants are summarized. The development of antimicrobial bone implants can provide effective solutions to bacterial infection issues in bone defect repair in the foreseeable future.

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.

Rising to the surface: capturing and detecting bacteria by rationally-designed surfaces

Analytical microbiology has made substantial progress since its conception, starting from potato slices, through selective agar media, to engineered surfaces modified with capture probes. While the latter represents the dominant approach in designing sensors for bacteria detection, the importance of sensor surface properties is frequently ignored. Herein, we highlight their significant role in the complex process of bacterial transition from planktonic to sessile, representing the first and critical step in bacteria detection. We present the main surface features and discuss their effect on the bio-solid interface and the resulting sensing capabilities for both flat and particulate systems. The concepts of rationally-designed surfaces for enhanced bacterial detection are presented with recent examples of sensors (capture probe-free) relying solely on surface cues.

Synergetic Effects of Nanoscale ALD-HfO2 Coatings and Bionic Microstructures for Antiadhesive Surgical Electrodes: Improved Cutting Performance, Antibacterial Property, and Biocompatibility

The high temperature induced by surgical electrodes is highly susceptible to severe surface adhesion and thermal damage to adjacent tissues, which is a major challenge in improving the quality of electrosurgery. Herein, we reported a coupled electrode with micro/nano hierarchical structures fabricated by depositing nanoscale hafnium oxide (HfO2) coatings on bionic microstructures (BMs) via laser texturing, acid washing, and atomic layer deposition (ALD) techniques. The synergistic effect of HfO2 coatings and BMs greatly enhanced the hemophobicity of the electrode with a blood contact angle of 162.15 ± 3.16°. Furthermore, the coupled surface was proven to have excellent antiadhesive properties to blood when heated above 100 °C, and the underlying mechanism was discussed. Further experiments showed that the coupled electrode had significant advantages in reducing cutting forces, thermal damage, and tissue adhesion mass. Moreover, the antibacterial rates against Escherichia coli and Staphylococcus aureus were 97.2% and 97.9%, respectively. In addition, the noncytotoxicity levels of HfO2 coatings were verified by cell apoptosis and cycle assays, indirectly endowing the coupled electrode with biocompatibility. Overall, the coupled electrode was shown to have broad potential for application in the field of electrosurgery, and this work could provide new insights into antiadhesion properties under high-temperature conditions.

Superhydrophobic cellulose paper with sustained antibacterial activity prepared by in-situ growth of carvacrol-loaded zinc-based metal organic framework nanorods for food packaging application

Cellulose paper packaging materials have gained considerable attention as substitutes for petroleum-based plastics owing to their biodegradability, renewability, flexibility, and good mechanical strength. However, high hydrophilicity and the absence of essential antibacterial activity limit their application in food packaging. In this study, a facile and energy-saving method was developed to improve the hydrophobicity of cellulose paper and endow it with a long-acting antibacterial effect by integrating cellulose paper substrate with metal-organic frameworks (MOFs). A dense and homogenous coating of regular hexagonal ZnMOF-74 nanorods was in-situ formed on a paper surface by layer-by-layer assembly followed by low-surface-energy polydimethylsiloxane (PDMS) modification to prepare a superhydrophobic PDMS@(ZnMOF-74)₅@paper. Excellent anti-fouling, self-cleaning, and antibacterial adhesion performances were obtained for this superhydrophobic paper. In addition, active carvacrol was loaded into the pores of ZnMOF-74 nanorods on PDMS@(ZnMOF-74)₅@paper to combine antibacterial adhesion together with bactericidal ability, ultimately resulting in a completely "bacteria-free" surface and sustained antibacterial performance. The resultant superhydrophobic papers not only showed overall migration values within the limit of 10 mg/dm² but also good stability against various harsh mechanical, environmental, and chemical treatments. This work gave insights into the potential of in-situ-developed MOFs-dopped coating as a functionally modified platform for preparing active superhydrophobic paper-based packaging.

Influence of Laser Parameters on the Texturing of 420 Stainless Steel

AISI 420 martensitic stainless steel is widely used in the mould industry due to its high tensile strength, hardness, and corrosion properties. Another requirement concerning any material used for this type of application is high thermal conductivity to minimise the time between consecutive injection cycles. The surfaces of some parts of the mould may be textured and reinforced with a material with higher thermal conductivity to achieve this aim. The results of a detailed study on the texturing of annealed 420 stainless steel using a Nd:YVO₄ fibre laser are presented in this work. The influence of the laser's processing parameters (laser power, scanning speed, number of passes, and line spacing) on the dimensions of the track, microstructure, and hardness of the modified surfaces was studied. Based on the continuity and dimensions of the machined grooves, several promising textures could be produced with laser power values from 5 to 30 W, scanning speeds of 500 to 2000 mm/s, 8 passes or more, and line spacings of 40 and 50 µm. High laser powers were responsible for the dissolution of chromium carbides in the laser tracks, the incorporation of chromium in austenite, and the consequent hardening of the microstructure.

Biomimetic superhydrophobic metal/nonmetal surface manufactured by etching methods: A mini review

As an emerging fringe science, bionics integrates the understanding of nature, imitation of nature, and surpassing nature in one aspect, and it organically combines the synergistic complementarity of function and structure–function integrated materials which is of great scientific interest. By imitating the microstructure of a natural biological surface, the bionic superhydrophobic surface prepared by human beings has the properties of self-cleaning, anti-icing, water collection, anti-corrosion and oil–water separation, and the preparation research methods are increasing. The preparation methods of superhydrophobic surface include vapor deposition, etching modification, sol–gel, template, electrostatic spinning, and electrostatic spraying, which can be applied to fields such as medical care, military industry, ship industry, and textile. The etching modification method can directly modify the substrate, so there is no need to worry about the adhesion between the coating and the substrate. The most obvious advantage of this method is that the obtained superhydrophobic surface is integrated with the substrate and has good stability and corrosion resistance. In this article, the different preparation methods of bionic superhydrophobic materials were summarized, especially the etching modification methods, we discussed the detailed classification, advantages, and disadvantages of these methods, and the future development direction of the field was prospected.

Synergistic Poly(lactic acid) Antibacterial Surface Combining Superhydrophobicity for Antiadhesion and Chlorophyll for Photodynamic Therapy

The problem of nosocomial infections caused by bacterial growth on material surfaces is an urgent threat to public health. Although numerous materials and methods have been explored to fight against infections, the methods are complicated and the materials are slightly toxic. It is highly desirable to develop an antibacterial strategy that kills bacteria effectively without drug resistance and cytotoxicity. Herein, we present a synergistic antibacterial polylactic acid (PLA) surface with superhydrophobic antibacterial adhesion and photodynamic bactericidal activity. Initially, the surface displayed low-adhesion superhydrophobicity and resisted most bacterial adhesion. Furthermore, completely non-toxic chlorophyll possessed excellent photodynamic bactericidal properties under non-toxic visible light, which was incorporated into micro-/nanoscale PLA surfaces. We achieved efficient antibacterial activity using completely non-toxic materials and a facile non-solvent-induced phase separation process. This non-toxic, simple, good biocompatible, and no drug-resistant strategy has great advantages in combating bacterial infections.

Antibacterial effect on microscale rough surface formed by fine particle bombarding

Fine particle bombarding (FPB) is typically utilized to modify metal surfaces by bombarding them with fine particles at high-speed. The diameters of the particles range from several to tens of micrometers. FPB forms fine microscale concavities and convexities on a surface. As FPB-treated surfaces are widely used in the food industry, the influence of bacteria on their surface must be considered. In this study, we examined the antibacterial activity of microscale rough surfaces formed by FPB. We applied FPB to a stainless-steel surface and evaluated the antibacterial effect of FPB-treated surfaces based on JIS Z 2801 (a modified test method from ISO 22196:2007). Our results indicated that the FPB-treated surfaces (FPB-1 (avg. pitch: 0.72 µm) and FPB-2 (avg. pitch: 3.56 µm)) exhibited antibacterial activity both against Escherichia coli and Staphylococcus aureus.

Innovative fouling-resistant materials for industrial heat exchangers: a review

Fouling of heat exchangers (HEs) has become a major concern across the industrial sector. Fouling is an omnipresent phenomenon but is particularly prevalent in the dairy, oil, and energy industries. Reduced energy performance that results from fouling represents significant operating loss in terms of both maintenance and impact on product quality and safety. In most industries, cleaning or replacing HEs are currently the only viable solutions for controlling fouling. This review examines the latest advances in the development of innovative materials and coatings for HEs that could mitigate the need for costly and frequent cleaning and potentially extend their operational life. To better understand the correlation between surface properties and fouling occurrence, we begin by providing an overview of the main mechanisms underlying fouling. We then present selected key strategies, which can differ considerably, for developing antifouling surfaces and conclude by discussing the current trends in the search for ideal materials for a range of applications. In our presentation of all these aspects, emphasis is given wherever possible to the potential transfer of these innovative surfaces from the laboratory to the three industries most concerned by HE fouling problems: food, petrochemicals, and energy production.

Spontaneous Adsorption-Induced Salvinia-like Micropillars with High Adhesion

Superhydrophobic surfaces with high adhesion provide high potential for underwater applications. Inspired by Salvinia leaf, here, we have reported a simple method for fabricating adhesive Salvinia-like micropillars via photolithography and spontaneous adsorption of organic molecules from the atmosphere. With continuous hydrocarbon adsorption on sputtered cerium dioxide (CeO₂) films, the surface gradually evolved and eventually became chemically heterogeneous. Huge wetting contrast from superhydrophilic to superhydrophobic over exposure time was observed; meanwhile, the wetting mode changed from the Wenzel (W) state to Cassie-Baxter (C-B) state. As a result, hydrophobic hydrocarbons (C-C/C-H) and trapped air between adjacent pillars contributed to the high apparent contact angle (CA), while the hydrophilic domains of C-O/O═C-O and CeO₂ on the top layer made the surface highly adhesive with water droplets. In comparison with traditional fluorinated superhydrophobic surfaces, CeO₂-coated surfaces showed high adhesive force with water droplets and can be used as a "mechanical hand" for water droplet transport. The adsorption-induced Salvinia-like micropillars with high adhesion may find many other droplet-based applications in microfluidic fields.

Blood repellent superhydrophobic surfaces constructed from nanoparticle-free and biocompatible materials

Durable and environment friendly superhydrophobic surfaces are needed for a set of important applications. Biomedical applications, in particular, impose stringent requirements on the biocompatibility of the materials used in the fabrication of superhydrophobic surfaces. In this study, we demonstrate the fabrication of mechanically durable superhydrophobic surfaces via an in-situ structuring strategy starting from natural carnauba wax and biocompatible polydimethylsiloxane (PDMS) materials. The transfer of the structure of the paper to a free-standing PDMS film provided the microscale structure. On top of this structured surface, the wax was spray-coated, initially resulting in a relatively homogeneous film with limited liquid repellence. The key in achieving superhydrophobicity was rubbing the surface for in-situ generation of a finely textured wax coating with a water contact angle of 169° and a sliding angle of 3°. The hierarchically structured surface exhibits mechanical robustness as demonstrated with water impact and linear abrasion tests. We finally demonstrate repellence of the surfaces against a range of blood products including platelet suspension, erythrocyte suspension, fresh plasma, and whole blood.

Implication of Surface Properties, Bacterial Motility, and Hydrodynamic Conditions on Bacterial Surface Sensing and Their Initial Adhesion

Biofilms are structured microbial communities attached to surfaces, which play a significant role in the persistence of biofoulings in both medical and industrial settings. Bacteria in biofilms are mostly embedded in a complex matrix comprised of extracellular polymeric substances that provide mechanical stability and protection against environmental adversities. Once the biofilm is matured, it becomes extremely difficult to kill bacteria or mechanically remove biofilms from solid surfaces. Therefore, interrupting the bacterial surface sensing mechanism and subsequent initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Noting that the process of bacterial adhesion is influenced by many factors, including material surface properties, this review summarizes recent works dedicated to understanding the influences of surface charge, surface wettability, roughness, topography, stiffness, and combination of properties on bacterial adhesion. This review also highlights other factors that are often neglected in bacterial adhesion studies such as bacterial motility and the effect of hydrodynamic flow. Lastly, the present review features recent innovations in nanotechnology-based antifouling systems to engineer new concepts of antibiofilm surfaces.

Bioinspired surfaces with wettability: biomolecule adhesion behaviors

Surface wettability plays an important role in regulating biomolecule adhesion behaviors. The biomolecule adhesion behaviors of superwettable surfaces have become an important topic as an important part of the interactions between materials and organisms. In addition to general research on the moderate wettability of surfaces, the studies of biomolecule adhesion behaviors extend to extreme wettability ranges such as superhydrophobic, superhydrophilic and slippery surfaces and attract both fundamental and practical interest. In this review, we summarize the recent studies on biomolecule adhesion behaviors on superwettable surfaces, especially superhydrophobic, superhydrophilic and slippery surfaces. The first part will focus on the influence of extreme wettability on cell adhesion behaviors. The second part will concentrate on the adhesion behaviors of biomacromolecules on superwettable surfaces including proteins and nucleic acids. Finally, the influences of wettability on small molecule adhesion behaviors on material surfaces have also been investigated. The mechanism of superwettable surfaces and their influences on biomolecule adhesion behaviors have been studied and highlighted.

Enhancing Staphylococcus aureus sterilization of stainless steel by the synergistic effect of surface structure and physical washing

Staphylococcus aureus infection is common in the clinical environment. It has been shown that the presence of micro/nano structures on material surfaces promote bacterial adhesion resistance. Herein, we assessed the S. aureus adhesion properties on laser micro/nano structured stainless-steel (316 L) surfaces after mechanical rotation and ultrasonic washing. The interaction force between S. aureus and structured surfaces was evaluated. A high concentration S. aureus solution was used to evaluate the bacterial sterilization efficiency after film formation on the stainless-steel surface. After 24 h of incubation, S. aureus films were formed on material surfaces. The comparison of static washing, surface mechanical rotation, and ultrasonic washing showed a decrease of S. aureus adhesion on the polished and laser induced periodic surface structures. However, S. aureus adhesion on the micro/nanoparticle surface after mechanical rotation washing did not display any obvious change compared to the polished one. Additionally, specimens after ultrasonic cleaning showed clear antibacterial adhesion than mechanical rotation. After the ultrasonic sterilization process, the laser induced periodic laser surface sample showed optimal bacterial adhesion inhibition. Finally, in vitro tests showed that the biocompatibility of the laser-induced structured surface did not change significantly from the polished surface one.

Self-Propelled Active Photothermal Nanoswimmer for Deep-Layered Elimination of Biofilm In Vivo

Increasing penetration of antibacterial agents into biofilm is a promising strategy for improvement of therapeutic effect and slowdown of the progression of antibiotic resistance. Herein, we design a near-infrared (NIR) light-driven nanoswimmer (HSMV). Under NIR light irradiation, HSMV performs efficient self-propulsion and penetrates into the biofilm within 5 min due to photothermal conversion of asymmetrically distributed AuNPs. The localized thermal (∼45 °C) and thermal-triggered release of vancomycin (Van) leads to an efficient combination of photothermal therapy and chemotherapy in one system. The active motion of HSMV increases the effective distance of photothermal therapy (PTT) and also improves the therapeutic index of the antibiotic, resulting in superior biofilm removal rate (>90%) in vitro. Notably, HSMV can eliminate S. aureus biofilms grown in vivo under 10 min of laser irradiation without damage to healthy tissues. This work may shed light on therapeutic strategies for in vivo treatment of biofilm-associated infections.

Anti-Biofouling Properties of Femtosecond Laser-Induced Submicron Topographies on Elastomeric Surfaces

Antibacterial coatings are often employed to elastomer surfaces to inhibit bacterial attachment. However, such approaches could lead to increased antibiotic resistance. Surface micro-/nanotexturing is gaining significant attention recently, as it is a passive approach to reduce bacterial adhesion to surfaces. To this end, this work aims to assess the anti-biofouling functionality of femtosecond laser-induced submicron topographies on biomedical elastomer surfaces. Femtosecond laser processing was employed to produce two types of topographies on stainless-steel substrates. The first one was highly regular and single scale submicron laser-induced periodic surface structures (LIPSS) while the second one was multiscale structures (MSs) containing both submicron- and micron-scale features. Subsequently, these topographies were replicated on polydimethylsiloxane (PDMS) and polyurethane (PU) elastomers to evaluate their bacterial retention characteristics. The submicron textured PDMS and PU surfaces exhibited long-term hydrophobic durability up to 100 h under immersed conditions. Both LIPSS and MS topographies on PDMS and PU elastomeric surfaces were shown to substantially reduce (>89%) the adhesion of Gram-negative Escherichia coli bacteria. At the same time, the anti-biofouling performance of LIPSS and MS topographies was found to be comparable with that of lubricant-impregnated surfaces. The influence of physical defects on textured surfaces on the adhesion behavior of bacteria was also elucidated. The results presented here are significant because the polymeric biomedical components that can be produced by replication cost effectively, while their biocompatibility can be improved through femtosecond surface modification of the respective replication masters.

Creating superhydrophobic and antibacterial surfaces on gold by femtosecond laser pulses

Femtosecond laser-induced surface structuring is a promising technique for the large-scale formation of nano- and microscale structures that can effectively modify materials' optical, electrical, mechanical, and tribological properties. Here we perform a systematic study on femtosecond laser-induced surface structuring on gold (Au) surface and their effect on both hydrophobicity and bacterial-adhesion properties. We created various structures including subwavelength femtosecond laser-induced periodic surface structures (fs-LIPSSs), fs-LIPSSs covered with nano/microstructures, conic and 1D-rod-like structures ( ≤ 6 μm), and spherical nanostructures with a diameter ≥ 10 nm, by raster scanning the laser beam, at different laser fluences. We show that femtosecond laser processing turns originally hydrophilic Au to a superhydrophobic surface. We determine the optimal conditions for the creation of the different surface structures and explain the mechanism behind the formed structures and show that the laser fluence is the main controlling parameter. We demonstrate the ability of all the formed surface structures to reduce the adhesion of Escherichia coli (E. coli) bacteria and show that fs-LIPSSs enjoys superior antibacterial adhesion properties due to its large-scale surface coverage. Approximately 99.03% of the fs-LIPSSs surface is free from bacterial adhesion. The demonstrated physical inhibition of bacterial colonies and biofilm formation without antibiotics is a crucial step towards reducing antimicrobial-resistant infections.

Targeting Pathogenic Biofilms: Newly Developed Superhydrophobic Coating Favors a Host-Compatible Microbial Profile on the Titanium Surface

Polymicrobial infections are one of the most common reasons for inflammation of surrounding tissues and failure of implanted biomaterials. Because microorganism adhesion is the first step for biofilm formation, physical-chemical modifications of biomaterials have been proposed to reduce the initial microbial attachment. Thus, the use of superhydrophobic coatings has emerged because of their anti-biofilm properties. However, these coatings on the titanium (Ti) surface have been developed mainly by dual-step surface modification techniques and have not been tested using polymicrobial biofilms. Therefore, we developed a one-step superhydrophobic coating on the Ti surface by using a low-pressure plasma technology to create a biocompatible coating that reduces polymicrobial biofilm adhesion and formation. The superhydrophobic coating on Ti was created by the glow discharge plasma using Ar, O_2, and hexamethyldisiloxane gases, and after full physical, chemical, and biological characterizations, we evaluated its properties regarding oral biofilm inhibition. The newly developed coating presented an increased surface roughness and, consequently, superhydrophobicity (contact angle over 150°) and enhanced corrosion resistance (p < 0.05) of the Ti surface. Furthermore, proteomic analysis showed a unique pattern of protein adsorption on the superhydrophobic coating without drastically changing the biologic processes mediated by proteins. Additionally, superhydrophobic treatment did not present a cytotoxic effect on fibroblasts or reduction of proliferation; however, it significantly reduced (≈8-fold change) polymicrobial adhesion (bacterial and fungal) and biofilm formation in vitro. Interestingly, superhydrophobic coating shifted the microbiological profile of biofilms formed in situ in the oral cavity, reducing by up to ≈7 fold pathogens associated with the peri-implant disease. Thus, this new superhydrophobic coating developed by a one-step glow discharge plasma technique is a promising biocompatible strategy to drastically reduce microbial adhesion and biofilm formation on Ti-based biomedical implants.

Role of Trapped Air in the Attachment of Staphylococcus aureus on Superhydrophobic Silicone Elastomer Surfaces Textured by a Femtosecond Laser

Surface texturing is an easy way to control wettability as well as bacterial adhesion. Air trapped in the surface texture of an immersed sample was often proposed as the origin of the low adhesion of bacteria to surfaces showing superhydrophobic properties. In this work, we identified two sets of femtosecond laser processing parameters that led to extreme superhydrophobic textures on a silicone elastomer but showed opposite behavior against Staphylococcus aureus (S. aureus, ATCC 25923) over a short incubation times (6 h). The main difference from most of the previous studies was that the air trapping was not evaluated from the extrapolation of the results of the classical sessile drop technique but from the drop rebound and Wilhelmy plate method. Additionally, all wetting tests were performed with bacteria culture medium and at 37 °C in the case of the Wilhelmy plate method. Following this approach, we were able to study the formation of the liquid/silicone interface and the associated air trapping for immersed samples that is, by far, most representative of the cell culture conditions than those associated with the sessile drop technique. Finally, the conversion of these superhydrophobic coatings into superhydrophilic ones revealed that air trapping is not a necessary condition to avoid Staphylococcus aureus retention on one of these two textured surfaces at short incubation times.

Iron-based nano-structured surfaces with antimicrobial properties

Bactericidal nanopillar array surfaces of FeOOH and Fe₂O₃ have been prepared as a cicada wing mimic. An even simpler structure-based antimicrobial surface was also made by coating with sea urchin-like FeOOH and Fe₂O₃ particles with a binder.