Multi-scale surface topography to minimize adherence and viability of nosocomial drug-resistant bacteria

The effects of submicron-textured surface topography on antibiotic efficacy against biofilms

Submicron-textured surfaces have been a promising approach to mitigate biofilm development and control microbial infection. However, the use of the single surface texturing approach is still far from ideal for achieving complete control of microbial infections on implanted biomedical devices. The use of a surface topographic modification that might improve the utility of standard antibiotic therapy could alleviate the complications of biofilms on devices. In this study, we characterized the biofilms of Staphylococcus aureus and Pseudomonas aeruginosa on smooth and submicron-textured polyurethane surfaces after 1, 2, 3, and 7 days, and measured the efficacy of common antibiotics against these biofilms. Results show that the submicron-textured surfaces significantly reduced biofilm formation and growth, and that the efficacy of antibiotics against biofilms grown on textured surfaces was improved compared with smooth surfaces. The antibiotic efficacy appears to be related to the degree of biofilm development. At early time points in biofilm formation, antibiotic treatment reveals reasonably good antibiotic efficacy against biofilms on both smooth and textured surfaces, but as biofilms mature, the efficacy of antibiotics drops dramatically on smooth surfaces, with lesser decreases seen for the textured surfaces. The results demonstrate that surface texturing with submicron patterns is able to improve the use of standard antibiotic therapy to treat device-centered biofilms by slowing the development of the biofilm, thereby offering less resistance to antibiotic delivery to the bacteria within the biofilm community.

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.

Replicated biopolymer pattern on PLLA-Ag basis with an excellent antibacterial response

The design of functional micro or nanostructured surfaces is undergoing extensive research for their intriguing multifunctional properties and for large variety of potential applications in biomedical field (tissue engineering or cell adhesion), electronics, optics or microfluidics. Such nanosized topographies can be easily fabricated by various lithography techniques and can be also further reinforced by synergic effect by combining aforementioned structures along materials with already outstanding antibacterial properties. In this work we fabricated novel micro/nanostructured substrates using soft lithography replication method and subsequent thermal nanoimprint lithography method, creating nanostructured films based on poly (l-lactic acid) (PLLA) fortified by thin silver films deposited by PVD. Main nanoscale patterns were fabricated by replicating surface patterns of optical discs (CDs and DVDs), which proved to be easy, fast and inexpensive method for creating relatively large area patterned surfaces. Their antimicrobial activity was examined in vitro against the bacteria Escherichia coli and Staphylococcus epidermidis strains. The results demonstrated that nanopatterned films actually improved the conditions for bacterial growth compared to pristine PLLA films, the novelty is based on formation of Ag nanoparticles on the surface/and in bulk, while silver nanoparticle enhanced and nanopatterned films exhibited excellent antibacterial activity against both bacterial strains, with circa 80 % efficacy in 4 h and complete bactericidal effect in span of 24 h.

Bacterial Biofilm Formation on Biomaterials and Approaches to Its Treatment and Prevention

Bacterial biofilms can cause widespread infection. In addition to causing urinary tract infections and pulmonary infections in patients with cystic fibrosis, biofilms can help microorganisms adhere to the surfaces of various medical devices, causing biofilm-associated infections on the surfaces of biomaterials such as venous ducts, joint prostheses, mechanical heart valves, and catheters. Biofilms provide a protective barrier for bacteria and provide resistance to antimicrobial agents, which increases the morbidity and mortality of patients. This review summarizes biofilm formation processes and resistance mechanisms, as well as the main features of clinically persistent infections caused by biofilms. Considering the various infections caused by clinical medical devices, we introduce two main methods to prevent and treat biomaterial-related biofilm infection: antibacterial coatings and the surface modification of biomaterials. Antibacterial coatings depend on the covalent immobilization of antimicrobial agents on the coating surface and drug release to prevent and combat infection, while the surface modification of biomaterials affects the adhesion behavior of cells on the surfaces of implants and the subsequent biofilm formation process by altering the physical and chemical properties of the implant material surface. The advantages of each strategy in terms of their antibacterial effect, biocompatibility, limitations, and application prospects are analyzed, providing ideas and research directions for the development of novel biofilm infection strategies related to therapeutic materials.

Bioinspired nanotopography on 3D printed tissue scaffold to impart mechanobactericidal and osteogenic activities

The great demand for bone grafts has motivated the development of tissue scaffolds with osteogenic activity, whereas the risk of implant-associated infection, especially given the rise of antimicrobial resistance, has compelled the development of scaffolds with innovative antimicrobial strategies. Bioinspired mechanobactericidal nanostructures are highly appealing as an alternative to traditional chemical approaches. This study presents an innovative spin-coating setup for the generation of nanotopography on the surfaces of a three-dimensional (3D)-printed porous polylactide (PLA) scaffold based on the principle of polymer demixing. The nanostructured PLA surface exhibited excellent bactericidal activity by contact killing of P. aeruginosa (86.60 % dead cells in 24 h) and S. aureus (92.36 %). The nanoscale topography supported the attachment and proliferation of pre-osteoblasts and better supported osteogenic differentiation than the unmodified scaffold. These findings demonstrate a single-step spin coating to yield nanotopography on 3D-printed polymer scaffolds that concurrently impart mechanobactericidal and osteogenic activities. Taken together, this work has important implications for engineering the next-generation 3D printed bioactive tissue scaffolds.

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

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

Modulation of MG-63 Osteogenic Response on Mechano-Bactericidal Micronanostructured Titanium Surfaces

Despite recent advances in the development of orthopedic devices, implant-related failures that occur as a result of poor osseointegration and nosocomial infection are frequent. In this study, we developed a multiscale titanium (Ti) surface topography that promotes both osteogenic and mechano-bactericidal activity using a simple two-step fabrication approach. The response of MG-63 osteoblast-like cells and antibacterial activity toward Pseudomonas aeruginosa and Staphylococcus aureus bacteria was compared for two distinct micronanoarchitectures of differing surface roughness created by acid etching, using either hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), followed by hydrothermal treatment, henceforth referred to as either MN-HCl or MN-H₂SO₄. The MN-HCl surfaces were characterized by an average surface microroughness (S_a) of 0.8 ± 0.1 μm covered by blade-like nanosheets of 10 ± 2.1 nm thickness, whereas the MN-H₂SO₄ surfaces exhibited a greater S_a value of 5.8 ± 0.6 μm, with a network of nanosheets of 20 ± 2.6 nm thickness. Both micronanostructured surfaces promoted enhanced MG-63 attachment and differentiation; however, cell proliferation was only significantly increased on MN-HCl surfaces. In addition, the MN-HCl surface exhibited increased levels of bactericidal activity, with only 0.6% of the P. aeruginosa cells and approximately 5% S. aureus cells remaining viable after 24 h when compared to control surfaces. Thus, we propose the modulation of surface roughness and architecture on the micro- and nanoscale to achieve efficient manipulation of osteogenic cell response combined with mechanical antibacterial activity. The outcomes of this study provide significant insight into the further development of advanced multifunctional orthopedic implant surfaces.

Finite Element Modelling of a Gram-Negative Bacterial Cell and Nanospike Array for Cell Rupture Mechanism Study

Inspired by nature, it is envisaged that a nanorough surface exhibits bactericidal properties by rupturing bacterial cells. In order to study the interaction mechanism between the cell membrane of a bacteria and a nanospike at the contact point, a finite element model was developed using the ABAQUS software package. The model, which saw a quarter of a gram-negative bacteria (Escherichia coli) cell membrane adhered to a 3 × 6 array of nanospikes, was validated by the published results, which show a reasonably good agreement with the model. The stress and strain development in the cell membrane was modeled and were observed to be spatially linear and temporally nonlinear. From the study, it was observed that the bacterial cell wall was deformed around the location of the nanospike tips as full contact was generated. Around the contact point, the principal stress reached above the critical stress leading to a creep deformation that is expected to cause cell rupture by penetrating the nanospike, and the mechanism is envisaged to be somewhat similar to that of a paper punching machine. The obtained results in this project can provide an insight on how bacterial cells of a specific species are deformed when they adhere to nanospikes, and how it is ruptured using this mechanism.

Mechanobactericidal Nanotopography on Nitrile Surfaces toward Antimicrobial Protective Gear

We have much to learn from other living organisms when it comes to engineering strategies to combat bacterial infections. This study describes the fabrication of cicada wing-inspired nanotopography on commercially pure (CP) nitrile sheets and nitrile gloves for medical use using the reactive ion etching (RIE) technique. Antibacterial activity against P. aeruginosa was tested using two different surface morphologies. It was observed that the etched nitrile surfaces effectively minimized bacterial colonization by inducing membrane damage. Our findings demonstrate a single-step dry etching method for creating mechanobactericidal topographies on nitrile-based surfaces. These findings have utility in designing next-generation personal protective gear in the clinical setting and for many other important applications in the age of antimicrobial resistance.

Innovative Antibacterial, Photocatalytic, Titanium Dioxide Microstructured Surfaces Based on Bacterial Adhesion Enhancement

Bacterial colonization and biofilm formation are found on nearly all wet surfaces, representing a serious problem for both human healthcare and industrial applications, where traditional treatments may not be effective. Herein, we describe a synergistic approach for improving the performance of antibacterial surfaces based on microstructured surfaces that embed titanium dioxide nanoparticles (TiO₂ NPs). The surfaces were designed to enhance bacteria entrapment, facilitating their subsequent eradication by a combination of UVC disinfection and TiO₂ NPs photocatalysis. The efficacy of the engineered TiO₂-modified microtopographic surfaces was evaluated using three different designs, and it was found that S2-lozenge and S3-square patterns had a higher concentration of trapped bacteria, with increases of 70 and 76%, respectively, compared to flat surfaces. Importantly, these surfaces showed a significant reduction (99%) of viable bacteria after just 30 min of irradiation with UVC 254 nm light at low intensity, being sixfold more effective than flat surfaces. Overall, our results showed that the synergistic effect of combining microstructured capturing surfaces with the chemical functionality of TiO₂ NPs paves the way for developing innovative and efficient antibacterial surfaces with numerous potential applications in the healthcare and biotechnology market.

Strategies to Mitigate and Treat Orthopaedic Device-Associated Infections

Orthopaedic device implants play a crucial role in restoring functionality to patients suffering from debilitating musculoskeletal diseases or to those who have experienced traumatic injury. However, the surgical implantation of these devices carries a risk of infection, which represents a significant burden for patients and healthcare providers. This review delineates the pathogenesis of orthopaedic implant infections and the challenges that arise due to biofilm formation and the implications for treatment. It focuses on research advancements in the development of next-generation orthopaedic medical devices to mitigate against implant-related infections. Key considerations impacting the development of devices, which must often perform multiple biological and mechanical roles, are delineated. We review technologies designed to exert spatial and temporal control over antimicrobial presentation and the use of antimicrobial surfaces with intrinsic antibacterial activity. A range of measures to control bio-interfacial interactions including approaches that modify implant surface chemistry or topography to reduce the capacity of bacteria to colonise the surface, form biofilms and cause infections at the device interface and surrounding tissues are also reviewed.

Surface Texturing and Combinatorial Approaches to Improve Biocompatibility of Implanted Biomaterials

Biomaterial associated microbial infection and blood thrombosis are two of the barriers that inhibit the successful use of implantable medical devices in modern healthcare. Modification of surface topography is a promising approach to combat microbial infection and thrombosis without altering bulk material properties necessary for device function and without contributing to bacterial antibiotic resistance. Similarly, the use of other antimicrobial techniques such as grafting poly(ethylene glycol) (PEG) and nitric oxide (NO) release also improve the biocompatibility of biomaterials. In this review, we discuss the development of surface texturing techniques utilizing ordered submicron-size pillars for controlling bacterial adhesion and biofilm formation, and we present combinatorial approaches utilizing surface texturing in combination with poly(ethylene glycol) (PEG) grafting and NO release to improve the biocompatibility of biomaterials. The manuscript also discusses efforts towards understanding the molecular mechanisms of bacterial adhesion responses to the surface texturing and NO releasing biomaterials, focusing on experimental aspects of the approach.

Preventing Peri-implantitis: The Quest for a Next Generation of Titanium Dental Implants

Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro, in vivo, and clinical studies of titanium and its alloys for dental implants.

A nanoconcrete welding strategy for constructing high-performance wound dressing

Engineering biomaterials to meet specific biomedical applications raises high requirements of mechanical performances, and simultaneous strengthening and toughening of polymer are frequently necessary but very challenging in many cases. In this work, we propose a new concept of nanoconcrete welding polymer chains, where mesoporous CaCO₃ (mCaCO₃) nanoconcretes which are composed of amorphous and nanocrystalline phases are developed to powerfully weld polymer chains through siphoning-induced occlusion, hydration-driven crystallization and dehydration-driven compression of nanoconcretes. The mCaCO₃ nanoconcrete welding technology is verified to be able to remarkably augment strength, toughness and anti-fatigue performances of a model polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-based porous membrane. Mechanistically, we have revealed polymer-occluded nanocrystal structure and welding-derived microstress which is much stronger than interfacial Van der Waals force, thus efficiently preventing the generation of microcracks and repairing initial microcracks by microcracks-induced hydration, crystallization and polymer welding of mCaCO₃ nanoconcretes. Constructed porous membrane is used as wound dressing, exhibiting a special nanoplates-constructed surface topography as well as a porous structure with plentiful oriented, aligned and opened pore channels, improved hydrophilicity, water vapor permeability, anti-bacterial and cell adherence, in support of wound healing and skin structural/functional repairing. The proposed nanoconcrete-welding-polymer strategy breaks a new pathway for improving the mechanical performances of polymers.

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An innovative nanoconcrete welding technology is developed for improving the mechanical performances of composite.

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A new kind of mesoporous CaCO₃ nanoconcretes is synthesized by an ion etching method.

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High-performance artificial skin is constructed based on a porous CaCO₃-PHBV membrane.

Fluid Flow Induces Differential Detachment of Live and Dead Bacterial Cells from Nanostructured Surfaces

Nanotopographic surfaces are proven to be successful in killing bacterial cells upon contact. This non-chemical bactericidal property has paved an alternative way of fighting bacterial colonization and associated problems, especially the issue of bacteria evolving resistance against antibiotic and antiseptic agents. Recent advancements in nanotopographic bactericidal surfaces have made them suitable for many applications in medical and industrial sectors. The bactericidal effect of nanotopographic surfaces is classically studied under static conditions, but the actual potential applications do have fluid flow in them. In this study, we have studied how fluid flow can affect the adherence of bacterial cells on nanotopographic surfaces. Gram-positive and Gram-negative bacterial species were tested under varying fluid flow rates for their retention and viability after flow exposure. The total number of adherent cells for both species was reduced in the presence of flow, but there was no flowrate dependency. There was a significant reduction in the number of live cells remaining on nanotopographic surfaces with an increasing flowrate for both species. Conversely, we observed a flowrate-independent increase in the number of adherent dead cells. Our results indicated that the presence of flow differentially affected the adherent live and dead bacterial cells on nanotopographic surfaces. This could be because dead bacterial cells were physically pierced by the nano-features, whereas live cells adhered via physiochemical interactions with the surface. Therefore, fluid shear was insufficient to overcome adhesion forces between the surface and dead cells. Furthermore, hydrodynamic forces due to the flow can cause more planktonic and detached live cells to collide with nano-features on the surface, causing more cells to lyse. These results show that nanotopographic surfaces do not have self-cleaning ability as opposed to natural bactericidal nanotopographic surfaces, and nanotopographic surfaces tend to perform better under flow conditions. These findings are highly useful for developing and optimizing nanotopographic surfaces for medical and industrial applications.

Fluid-driven bacterial accumulation in proximity of laser-textured surfaces

In this work we investigated the role of fluid in the initial phase of bacterial adhesion on textured surfaces, focusing onto the approach of the bacterial cells towards the surface. In particular, stainless steel surfaces textured via femtosecond laser interaction have been considered. The method combined a simulation routine, based on the numerical solution of Navier-Stokes equations, and the use of a theoretical model, based on the Smoluchowski's equation. Results highlighted a slowdown of the fluid velocity field in correspondence of the surface dales. In addition, a shear induced accumulation on the top of the surface protrusions was predicted for motile bacterial species, E. coli. In particular, we observed a role of the surface protrusions in increasing the range over which motile bacterial species are attracted towards the surface through a rheotactic mechanism. In other words, we found that, in certain conditions of fluid flow and textured surface morphology, surface protrusions act as a sort of "rheotactic antennas".

Anodized Aluminum Surface with Topography-Mediated Antibacterial Properties

Topography-mediated antibacterial surfaces that inactivate bacteria by physical contact have gained attention in recent years. Contrary to conventional antibacterial coatings, topography-mediated antibacterial surfaces do not suffer from coating instability and possible toxicity problems. In this study, a one-step hard anodization process has been deployed to fabricate a topography-mediated antibacterial aluminum surface. By optimizing anodization parameters, such as the concentration of the electrolyte, current density, and anodization time, desirable features of micronanoscale morphology were achieved. The optimum conditions of anodized aluminum that provided pores of a diameter of 151 ± 37 nm effectively killed 100% of E. coli bacteria.

NIR-Reflective and Hydrophobic Bio-Inspired Nano-Holed Configurations on Titanium Alloy

Near-infrared (NIR) radiation plays an important role in guided external stimulus therapies; its application in bone-related treatments is becoming more and more frequent. Therefore, metallic biomaterials that exhibit properties activated by NIR are promising for further orthopedic procedures. In this work, we present an adapted electroforming approach to attain a biomorphic nano-holed TiO₂ coating on Ti6Al4V alloy. Through a precise control of the anodization conditions, structures revealed the formation of localized nano-pores arranged in a periodic assembly. This specific organization provoked higher stability against thermal oxidation and precise hydrophobic wettability behavior according to Cassie-Baxter's model; both characteristics are a prerequisite to ensure a favorable biological response in an implantable structure for guided bone regeneration. In addition, the periodically arranged sub-wavelength-sized unit cell on the metallic-dielectric structure exhibits a peculiar optical response, which results in higher NIR reflectivity. Accordingly, we have proved that this effect enhances the efficiency of the scattering processes and provokes a significant improvement of light confinement producing a spontaneous NIR fluorescence emission. The combination of the already favorable mechanical and biocompatibility properties of Ti6Al4V, along with suitable thermal stability, wetting, and electro-optical behavior, opens a promising path toward strategic bone therapeutic procedures.

A Novel Strategy for Creating an Antibacterial Surface Using a Highly Efficient Electrospray-Based Method for Silica Deposition

Adhesion of bacteria on biomedical implant surfaces is a prerequisite for biofilm formation, which may increase the chances of infection and chronic inflammation. In this study, we employed a novel electrospray-based technique to develop an antibacterial surface by efficiently depositing silica homogeneously onto polyethylene terephthalate (PET) film to achieve hydrophobic and anti-adhesive properties. We evaluated its potential application in inhibiting bacterial adhesion using both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria. These silica-deposited PET surfaces could provide hydrophobic surfaces with a water contact angle greater than 120° as well as increased surface roughness (root mean square roughness value of 82.50 ± 16.22 nm and average roughness value of 65.15 ± 15.26 nm) that could significantly reduce bacterial adhesion by approximately 66.30% and 64.09% for E. coli and S. aureus, respectively, compared with those on plain PET surfaces. Furthermore, we observed that silica-deposited PET surfaces showed no detrimental effects on cell viability in human dermal fibroblasts, as confirmed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide and live/dead assays. Taken together, such approaches that are easy to synthesize, cost effective, and efficient, and could provide innovative strategies for preventing bacterial adhesion on biomedical implant surfaces in the clinical setting.

Isolation and molecular identification of biofilm producing P. aeruginosa and K. pneumoniae from urinary tract infections patient urine sample

BACKGROUND

Recent years, multi drug resistant pathogens and their pathogenicity were increased worldwide due to unauthorized consumption of antibiotics. In addition, correlation between multi drug resistant bacteria and biofilm formation is heightened due to the production of more virulence behavior. There is no better identification methods are available for detection of biofilm producing gram negative bacteria.

MATERIALS AND METHODS

In this research work, multi drug resistant strains of Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were identified based on the specific antibiotics and third generation cephalosporin discs by disc diffusion assay. Subsequently, biofilm forming ability of selected pathogens were identified tissue culture plate and tube test. Based on the multi-drug resistant ability and biofilm production, the molecular identification of P. aeruginosa and K. pneumoniae were confirmed by PCR using universal primers.

RESULTS AND CONCLUSIONS

No zone of inhibition present around the discs of muller hinton agar plates were confirm, selected P. aeruginosa and K. pneumoniae strains were multi drug resistant pathogens. Performed third generation cephalosporin antibiotics were also highly sensitive to selected pathogens of P. aeruginosa and K. pneumoniae. Further, biofilm forming ability of selected P. aeruginosa and K. pneumoniae was confirmed by tissue culture plate and tube methods. Finally, molecular identification of P. aeruginosa and K. pneumoniae was named as P. aeruginosa and K. pneumoniae. Our result was conclude, selected P. aeruginosa and K. pneumoniae as biofilm producing pathogens and also highly resistant to current antibiotics.

Trends in Bactericidal Nanostructured Surfaces: An Analytical Perspective

Since the discovery of the bactericidal properties of cicada wing surfaces, there has been a surge in the number of studies involving antibacterial nanostructured surfaces (NSS). Studies show that there are many parameters (and thus, thousands of parameter combinations) that influence the bactericidal efficiency (BE) of these surfaces. Researchers attempted to correlate these parameters to BE but have so far been unsuccessful. This paper presents a meta-analysis and perspective on bactericidal NSS, aiming to identify trends and gaps in the literature and to provide insights for future research. We have attempted to synthesize data from a wide range of published studies and establish trends in the literature on bactericidal NSS. Numerous research gaps and findings based on correlations of various parameters are presented here, which will assist in the design of efficient bactericidal NSS and shape future research. Traditionally, it is accepted that BE of NSS depends on the bacterial Gram-stain type. However, this review found that factors beyond Gram-stain type are also influential. Furthermore, it is found that despite their higher BE, hydrophobic NSS are less commonly studied for their bactericidal effect. Interestingly, the impacts of surface hydrophobicity and roughness on the bactericidal effect were found to be influenced by a Gram-stain type of the tested bacteria. In addition, cell motility and shape influence BE, but research attention into these factors is lacking. It was found that hydrophobic NSS demonstrate more promising results than their hydrophilic counterparts; however, these surfaces have been overlooked. Confirming the common belief of the influence of nanofeature diameter on bactericidal property, this analysis shows the feature aspect ratio is also decisive. NSS fabricated on silicon substrates perform better than their titanium counterparts, and the success of these silicon structures maybe attributed to the fabrication processes. These insights benefit engineers and scientists alike in developing next-generation NSS.

Surface Design for Antibacterial Materials: From Fundamentals to Advanced Strategies

Healthcare-acquired infections as well as increasing antimicrobial resistance have become an urgent global challenge, thus smart alternative solutions are needed to tackle bacterial infections. Antibacterial materials in biomedical applications and hospital hygiene have attracted great interest, in particular, the emergence of surface design strategies offer an effective alternative to antibiotics, thereby preventing the possible development of bacterial resistance. In this review, recent progress on advanced surface modifications to prevent bacterial infections are addressed comprehensively, starting with the key factors against bacterial adhesion, followed by varying strategies that can inhibit biofilm formation effectively. Furthermore, "super antibacterial systems" through pre-treatment defense and targeted bactericidal system, are proposed with increasing evidence of clinical potential. Finally, the advantages and future challenges of surface strategies to resist healthcare-associated infections are discussed, with promising prospects of developing novel antimicrobial materials.

Effects of Nanopillar Size and Spacing on Mechanical Perturbation and Bactericidal Killing Efficiency

Nanopatterned surfaces administer antibacterial activity through contact-induced mechanical stresses and strains, which can be modulated by changing the nanopattern's radius, spacing and height. However, due to conflicting recommendations throughout the theoretical literature with poor agreement to reported experimental trends, it remains unclear whether these key dimensions-particularly radius and spacing-should be increased or decreased to maximize bactericidal efficiency. It is shown here that a potential failure of biophysical models lies in neglecting any out-of-plane effects of nanopattern contact. To highlight this, stresses induced by a nanopattern were studied via an analytical model based on minimization of strain and adhesion energy. The in-plane (areal) and out-of-plane (contact pressure) stresses at equilibrium were derived, as well as a combined stress (von Mises), which comprises both. Contour plots were produced to illustrate which nanopatterns elicited the highest stresses over all combinations of tip radius between 0 and 100 nm and center spacing between 0 and 200 nm. Considering both the in-plane and out-of-plane stresses drastically transformed the contour plots from those when only in-plane stress was evaluated, clearly favoring small tipped, tightly packed nanopatterns. In addition, the effect of changes to radius and spacing in terms of the combined stress showed the best qualitative agreement with previous reported trends in killing efficiency. Together, the results affirm that the killing efficiency of a nanopattern can be maximized by simultaneous reduction in tip radius and increase in nanopattern packing ratio (i.e., radius/spacing). These findings provide a guide for the design of highly bactericidal nanopatterned surfaces.

Biomaterials for human space exploration: A review of their untapped potential

As biomaterial advances make headway into lightweight radiation protection, wound healing dressings, and microbe resistant surfaces, a relevance to human space exploration manifests itself. To address the needs of the human in space, a knowledge of the space environment becomes necessary. Both an understanding of the environment itself and an understanding of the physiological adaptations to that environment must inform design parameters. The space environment permits the fabrication of novel biomaterials that cannot be produced on Earth, but benefit Earth. Similarly, designing a biomaterial to address a space-based challenge may lead to novel biomaterials that will ultimately benefit Earth. This review describes several persistent challenges to human space exploration, a variety of biomaterials that might mitigate those challenges, and considers a special category of space biomaterial. STATEMENT OF SIGNIFICANCE: This work is a review of the major human and environmental challenges facing human spaceflight, and where biomaterials may mitigate some of those challenges. The work is significant because a broad range of biomaterials are applicable to the human space program, but the overlap is not widely known amongst biomaterials researchers who are unfamiliar with the challenges to human spaceflight. Additionaly, there are adaptations to microgravity that mimic the pathology of certain disease states ("terrestrial analogs") where treatments that help the overwhelmingly healthy astronauts can be applied to help those with the desease. Advances in space technology have furthered the technology in that field on Earth. By outlining ways that biomaterials can promote human space exploration, space-driven advances in biomaterials will further biomaterials technology.

Validation of the mechano-bactericidal mechanism of nanostructured surfaces with finite element simulation

The mechano-bactericidal property of nanostructured surfaces has become the focus of intensive research toward the development of a new generation of antibacterial surfaces, especially in the current era of spreading antibiotic resistance. However, the mechanisms underlying nanostructured surfaces mechanically damaging bacteria remain unclear, which ultimately limits translational potential toward real-world applications. Using finite element simulation technique, we developed the three-dimensional thin wall with turgor pressure finite element model (3D-TWTP-FEM) of bacterial cell and verified the reliability of this model by the AFM indentation experiment simulation of the cell, and the cell model is able to simulate suspended bacterial cell and the process of cell adhering to the flat and nanopillar surfaces. Since bacterial cells suffer greater stress and deformation on the nanopillar surfaces, a two-stage model of the elastic and creep deformation stage of the cells on the nanostructured surfaces was developed. The calculations show that the location of the maximum stress/strain on the cells adhered to the nanopillar surfaces is at the liquid-cell-nanopillar three phase contact line. The computational results confirmed the ability of nanostructured surfaces to mechanically lyse bacteria and gave the effect of nanopillar geometry on the efficiency and speed of bacterial cell rupture. This study provides fundamental physical insights into how nanopillar surfaces can serve as effective and fast mechanical antimicrobial materials.

Fabrication of biomimetic patterned PCL membranes mimicking the complexity of Rubus fruticosus leaves surface

The development of bioresponsive interfaces that can induce a beneficial impact on cell mechanisms, such as adhesion, proliferation, migration and differentiation are of utmost relevance in Tissue engineering (TE) approaches. The surface topography is a captivating property that contribute to interesting cell responses, being inspired by several cues found in nature. Therefore, the study herein presented reports the fabrication of a surface topography using the Rubus fruticosus leaf on spin casting polycaprolactone (PCL) membranes. The topography was replicated by replica molding rapid fabrication technique and nanoimprint lithography (NIL). The biomimetic patterned PCL membranes (bpM) were successfully produced revealing high detail due to the complexity of the leaf's surface ranging from the stroma structures to nerves structures. The thermal evaluation revealed a slight increase of crystallinity of the bpM compared with the other tested conditions. However, did not induce significant effects on the melting and recrystallization temperatures. The mechanical properties revealed that the young modulus increase from 3.2 MPa to 4.4 MPa during the imprinting process. However, bpM presents a lowest elongation capacity than bare membrane (bM) (1076 to 444 %, respectively) due to the heterogeneous thickness induced by the topography. The selected topography revealed to promote a positive bioresponse, depicted by the improvement of the cellular behaviour and different organization. This promising strategy revealed that circumventing the traditional topographies by nature mimetic topographies is fundamental for the development of innovative bioresponsive substrates that can tune cellular behaviour in TE strategies.

Low-Temperature Hydrothermal Synthesis of Novel 3D Hybrid Nanostructures on Titanium Surface with Mechano-bactericidal Performance

Titanium is extensively employed in modern medicines as orthopedic and dental implants, but implant failures frequently occur because of bacterial infections. Herein, three types of 3D nanostructured titanium surfaces with nanowire clusters (NWC), nanowire/sheet clusters (NW/SC) and nanosheet clusters (NSC), were fabricated using the low-temperature hydrothermal synthesis under normal pressure, and assessed for the sterilization against two common human pathogens. The results show that the NWC and NSC surfaces merely display good bactericidal activity against Escherichia coli, whereas the NW/SC surface represents optimal bactericidal efficiency against both Escherichia coli (98.6 ± 1.23%) and Staphylococcus aureus (69.82 ± 2.79%). That is attributed to the hybrid geometric nanostructure of NW/SC, i.e., the pyramidal structures of ∼23 nm in tip diameter formed with tall clustered wires, and the sharper sheets of ∼8 nm in thickness in-between these nanopyramids. This nanostructure displays a unique mechano-bactericidal performance via the synergistic effect of capturing the bacteria cells and penetrating the cell membrane. This study proves that the low-temperature hydrothermal synthesized hybrid mechano-bactericidal titanium surfaces provide a promising solution for the construction of bactericidal biomedical implants.

The drug resistance of multidrug-resistant bacterial organisms in pediatric pneumonia patients

OBJECTIVE

This study aimed to investigate the distribution of multidrug-resistant organisms in pediatric patients with infectious pneumonia and to analyze their resistance and risk factors.

METHODS

Pediatric patients infected with five MDROs (MRSA, MDR-PA, MDRAB, ESBL KP, and ESBL E. coli) and five sensitive bacteria (MSSA, PA, AB, KP, and E. coli) were recruited as the study cohort. The distribution of the MDROs and the risk factors for MDRO-infected pneumonia were investigated. The two groups' treatment costs, hospitalization times, and prognoses were compared.

RESULTS

A total of 219 children were included, including 3 cases of mixed infections with MDRO and sensitive bacteria (1.37%), 110 cases of MDRO infections (50.23%), and 106 cases of sensitive bacterial infections (48.40%). Imipramine was sensitive to MDR-PA, MDRAB, ESBL KP, and ESBL E. coli, and vancomycin was sensitive to MRSA. A logistic regression model and a multifactorial analysis showed that ICU treatment, mechanical ventilation, arterial and venous intubation, fiberoptic bronchoscopy, concomitant chronic lung disease, and chronic cardiovascular disease were the independent risk factors for MDRO (P < 0.05). The hospitalization times, the treatment costs, and the 30-day mortality rate of the children in the MDRO group were significantly higher than they were in the children infected with sensitive bacteria (P < 0.05).

CONCLUSION

Vancomycin or imipenem may result in good clinical outcomes in children treated in the ICU subject to mechanical ventilation, arterial and venous intubation, fiberoptic bronchoscopy, the overuse of antimicrobial drugs, and children with concomitant chronic lung disease or chronic cardiovascular disease.

Antibacterial Titanium Implants Biofunctionalized by Plasma Electrolytic Oxidation with Silver, Zinc, and Copper: A Systematic Review

Patients receiving orthopedic implants are at risk of implant-associated infections (IAI). A growing number of antibiotic-resistant bacteria threaten to hamper the treatment of IAI. The focus has, therefore, shifted towards the development of implants with intrinsic antibacterial activity to prevent the occurrence of infection. The use of Ag, Cu, and Zn has gained momentum as these elements display strong antibacterial behavior and target a wide spectrum of bacteria. In order to incorporate these elements into the surface of titanium-based bone implants, plasma electrolytic oxidation (PEO) has been widely investigated as a single-step process that can biofunctionalize these (highly porous) implant surfaces. Here, we present a systematic review of the studies published between 2009 until 2020 on the biomaterial properties, antibacterial behavior, and biocompatibility of titanium implants biofunctionalized by PEO using Ag, Cu, and Zn. We observed that 100% of surfaces bearing Ag (Ag-surfaces), 93% of surfaces bearing Cu (Cu-surfaces), 73% of surfaces bearing Zn (Zn-surfaces), and 100% of surfaces combining Ag, Cu, and Zn resulted in a significant (i.e., >50%) reduction of bacterial load, while 13% of Ag-surfaces, 10% of Cu-surfaces, and none of Zn or combined Ag, Cu, and Zn surfaces reported cytotoxicity against osteoblasts, stem cells, and immune cells. A majority of the studies investigated the antibacterial activity against S. aureus. Important areas for future research include the biofunctionalization of additively manufactured porous implants and surfaces combining Ag, Cu, and Zn. Furthermore, the antibacterial activity of such implants should be determined in assays focused on prevention, rather than the treatment of IAIs. These implants should be tested using appropriate in vivo bone infection models capable of assessing whether titanium implants biofunctionalized by PEO with Ag, Cu, and Zn can contribute to protect patients against IAI.

Theoretical and computational investigations into mechanobactericidal activity of nanostructures at the bacteria-biomaterial interface: a critical review

Mechanobactericidal surfaces kill bacteria upon contact by posing landscapes hostile to them and have rapidly gained popularity amongst researchers over the past decade. But several fundamental aspects of the physical interactions between bacteria and nanostructures and the underlying killing mechanisms are still poorly understood. This is partly attributable to the difficulties associated with the characterization of the bacteria-nanostructure interface in a biological environment during the killing process and to the stochastic and non-linear behaviors generally associated with biological systems. However, several analytical and computational models have presented and analyzed possible killing routes and have proven useful in understanding different aspects of the phenomena. Analytical models formulate equations, often based on energy considerations, and aim to predict optimal nanostructure dimensions. They are more widely used than computational models that try to simulate the killing process and the stress or strain fields in the cell membrane through numerical methods. These models provide insights into the forces responsible for the spontaneous penetration of the cell into the nanostructures, which are still highly debated in the field. They have also helped to correlate the nanostructure dimensions with their bactericidal activity to optimize such values and facilitate the translation of this technology to physiological conditions. This review focuses on the rupture of the bacterial cell wall by nanopillars or similar high aspect ratio structures and applying these principles to the deformation of the cell membrane. Many recent interesting experimental results that either refute our current understanding or have the potential to challenge the current consensus are also discussed. Lastly, the limitations of the current strategies and opportunities to address the unresolved gaps in the field are also presented.

Bactericidal efficiency of micro- and nanostructured surfaces: a critical perspective

Micro/nanostructured surfaces (MNSS) have shown the ability to inactivate bacterial cells by physical means. An enormous amount of research has been conducted in this area over the past decade. Here, we review the various surface factors that affect the bactericidal efficiency. For example, surface hydrophobicity of the substrate has been accepted to be influential on the bactericidal effect of the surface, but a review of the literature suggests that the influence of hydrophobicity differs with the bacterial species. Also, various bacterial viability quantification methods on MNSS are critically reviewed for their suitability for the purpose, and limitations of currently used protocols are discussed. Presently used static bacterial viability assays do not represent the conditions of which those surfaces could be applied. Such application conditions do have overlaying fluid flow, and bacterial behaviours are drastically different under flow conditions compared to under static conditions. Hence, it is proposed that the bactericidal effect should be assessed under relevant fluid flow conditions with factors such as shear stress and flowrate given due significance. This review will provide a range of opportunities for future research in design and engineering of micro/nanostructured surfaces with varying experimental conditions.

Mechanics of Bacterial Interaction and Death on Nanopatterned Surfaces

Nanopatterned surfaces are believed to kill bacteria through physical deformation, a mechanism that has immense potential against biochemical resistance. Because of its elusive nature, this mechanism is mostly understood through biophysical modeling. Problematically, accurate descriptions of the contact mechanics and various boundary conditions involved in the bacteria-nanopattern interaction remain to be seen. This may underpin conflicting predictions, found throughout the literature, regarding two important aspects of the mechanism-that is, its critical action site and relationship with geometry. Herein, a robust computational analysis of bacteria-nanopattern interaction is performed using a three-dimensional finite element modeling that incorporates relevant continuum mechanical properties, multilayered envelope structure, and adhesion interaction conditions. The model is applied to more accurately study the elusory mechanism and its enhancement via nanopattern geometry. Additionally, micrographs of bacteria adhered on a nanopatterned cicada wing are examined to further inform and verify the major modeling predictions. Together, the results indicate that nanopatterned surfaces do not kill bacteria predominantly by rupture in between protruding pillars as previously thought. Instead, nondevelopable deformation about pillar tips is more likely to create a critical site at the pillar apex, which delivers significant in-plane strains and may locally rupture and penetrate the cell. The computational analysis also demonstrates that envelope deformation is increased by adhesion to nanopatterns with smaller pillar radii and spacing. These results further progress understanding of the mechanism of nanopatterned surfaces and help guide their design for enhanced bactericidal efficiency.

How microbes read the map: Effects of implant topography on bacterial adhesion and biofilm formation

Microbes have remarkable capabilities to attach to the surface of implanted medical devices and form biofilms that adversely impact device function and increase the risk of multidrug-resistant infections. The physicochemical properties of biomaterials have long been known to play an important role in biofilm formation. More recently, a series of discoveries in the natural world have stimulated great interest in the use of 3D surface topography to engineer antifouling materials that resist bacterial colonization. There is also increasing evidence that some medical device surface topographies, such as those designed for tissue integration, may unintentionally promote microbial attachment. Despite a number of reviews on surface topography and biofilm control, there is a missing link between how bacteria sense and respond to 3D surface topographies and the rational design of antifouling materials. Motivated by this gap, we present a review of how bacteria interact with surface topographies, and what can be learned from current laboratory studies of microbial adhesion and biofilm formation on specific topographic features and medical devices. We also address specific biocompatibility considerations and discuss how to improve the assessment of the anti-biofilm performance of topographic surfaces. We conclude that 3D surface topography, whether intended or unintended, is an important consideration in the rational design of safe medical devices. Future research on next-generation smart antifouling materials could benefit from a greater focus on translation to real-world applications.

Titanium for Orthopedic Applications: An Overview of Surface Modification to Improve Biocompatibility and Prevent Bacterial Biofilm Formation

Titanium and its alloys have emerged as excellent candidates for use as orthopedic biomaterials. Nevertheless, there are often complications arising after implantation of orthopedic devices, most notably prosthetic joint infection and aseptic loosening. To ensure that implanted devices remain functional in situ, innovation in surface modification has attracted much attention in the effort to develop orthopedic materials with optimal characteristics at the biomaterial-tissue interface. This review will draw together metallurgy, surface engineering, biofilm microbiology, and biomaterial science. It will serve to appreciate why titanium and its alloys are frequently used orthopedic biomaterials and address some of the challenges facing these biomaterials currently, including the significant problem of device-associated infection. Finally, the authors shall consolidate and evaluate surface modification techniques employed to overcome some of these issues by offering a unique perspective as to the direction in which research is headed from a broad, interdisciplinary point of view.

Salt coatings functionalize inert membranes into high-performing filters against infectious respiratory diseases

Respiratory protection is key in infection prevention of airborne diseases, as highlighted by the COVID-19 pandemic for instance. Conventional technologies have several drawbacks (i.e., cross-infection risk, filtration efficiency improvements limited by difficulty in breathing, and no safe reusability), which have yet to be addressed in a single device. Here, we report the development of a filter overcoming the major technical challenges of respiratory protective devices. Large-pore membranes, offering high breathability but low bacteria capture, were functionalized to have a uniform salt layer on the fibers. The salt-functionalized membranes achieved high filtration efficiency as opposed to the bare membrane, with differences of up to 48%, while maintaining high breathability (> 60% increase compared to commercial surgical masks even for the thickest salt filters tested). The salt-functionalized filters quickly killed Gram-positive and Gram-negative bacteria aerosols in vitro, with CFU reductions observed as early as within 5 min, and in vivo by causing structural damage due to salt recrystallization. The salt coatings retained the pathogen inactivation capability at harsh environmental conditions (37 °C and a relative humidity of 70%, 80% and 90%). Combination of these properties in one filter will lead to the production of an effective device, comprehensibly mitigating infection transmission globally.

The Effectiveness of Nafion-Coated Stainless Steel Surfaces for Inhibiting Bacillus Subtilis Biofilm Formation

Stainless steel is one of most commonly used materials in the world; however, biofilms on the surfaces of stainless steel cause many serious problems. In order to find effective methods of reducing bacterial adhesion to stainless steel, and to investigate the role of electrostatic effects during the formation of biofilms, this study used a stainless steel surface that was negatively charged by being coated with Nafion which was terminated by sulfonic groups. The results showed that the roughness of stainless steel discs coated with 1% Nafion was similar to an uncoated surface; however the hydrophobicity increased, and the Nafion-coated surface reduced the adhesion of Bacillus subtilis by 75% compared with uncoated surfaces. Therefore, a facile way to acquire antibacterial stainless steel was found, and it is proved that electrostatic effects have a significant influence on the formation of biofilms.

UV-Curable Surface-Attached Antimicrobial Polymeric Onium Coatings: Designing Effective, Solvent-Resistant Coatings for Plastic Surfaces

Contact-active ammonium and phosphonium antimicrobial polymeric coatings grafted to plastic surfaces by UV treatment are described. Robust, antimicrobial styrenic polymeric scaffolds copolymerized with a low loading of UV-curable benzophenone were prepared by nitroxide-mediated polymerization (NMP). Similar reversible addition-fragmentation chain-transfer (RAFT)-controlled radical polymerizations were attempted for comparison. These random styrenics were further functionalized into partially quaternarized water-soluble cationic polymers. UV-cured polymeric thin film coatings possessing cationic groups with n-alkyl substituents of n ≤ 2 demonstrate antimicrobial properties against both Gram-positive and Gram-negative bacteria, while species containing bulkier or longer substituents were biologically inactive. The UV-cured cationic antimicrobial polymeric onium thin films also demonstrate enhanced abrasion and chemical resistance.

Natural Architectures for Tissue Engineering and Regenerative Medicine

The ability to control the interactions between functional biomaterials and biological systems is of great importance for tissue engineering and regenerative medicine. However, the underlying mechanisms defining the interplay between biomaterial properties and the human body are complex. Therefore, a key challenge is to design biomaterials that mimic the in vivo microenvironment. Over millions of years, nature has produced a wide variety of biological materials optimised for distinct functions, ranging from the extracellular matrix (ECM) for structural and biochemical support of cells to the holy lotus with special wettability for self-cleaning effects. Many of these systems found in biology possess unique surface properties recognised to regulate cell behaviour. Integration of such natural surface properties in biomaterials can bring about novel cell responses in vitro and provide greater insights into the processes occurring at the cell-biomaterial interface. Using natural surfaces as templates for bioinspired design can stimulate progress in the field of regenerative medicine, tissue engineering and biomaterials science. This literature review aims to combine the state-of-the-art knowledge in natural and nature-inspired surfaces, with an emphasis on material properties known to affect cell behaviour.

Antiviral and Antibacterial Nanostructured Surfaces with Excellent Mechanical Properties for Hospital Applications

With the rise of bacterial and viral infections including the recent outbreak of coronavirus, the requirement for novel antimicrobial strategies is also rising with urgency. To solve this problem, we have used a wet etching technique to fabricate 23 nm wide nanostructures randomly aligned as ridges on aluminum (Al) 6063 alloy surfaces. The surfaces were etched for 0.5, 1, and 3 h. The surfaces were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, contact angle goniometry, nanoindentation and atomic force microscopy. Strains of the Gram negative bacteria Pseudomonas aeruginosa and the Gram positive bacteria Staphylococcus aureus were used to evaluate the bacterial attachment behavior. For the first time, common respiratory viruses, respiratory syncytial virus (RSV) and rhinovirus (RV), were investigated for antiviral activity on nanostructured surfaces. It was found that the etched Al surfaces were hydrophilic and the nanoscale roughness enhanced with the etching time with R_rms ranging from 69.9 to 995 nm. Both bacterial cells of P. aeruginosa and S. aureus were physically deformed and were nonviable upon attachment after 3 h on the etched Al 6063 surface. This nanoscale surface topography inactivated 92 and 87% of the attached P. aeruginosa and S. aureus cells, respectively. The recovery of infectious RSV was also reduced significantly within 2 h of exposure to the nanostructured surfaces compared to the smooth Al control surfaces. There was a 3-4 log₁₀ reduction in the viability counts of rhinovirus after 24 h on the nanostructured surfaces. The nanostructured surfaces exhibited excellent durability as the surfaces sustained 1000 cycles of 2000 μN load without any damage. This is the first report that has shown the combined antibacterial and antiviral property of the nanostructured surface with excellent nanomechanical properties that could be potentially significant for use in hospital environments to stop the spread of infections arising from physical surfaces.

Bacterial Adhesion on Femtosecond Laser-Modified Polyethylene

In this study, femtosecond laser-induced sub-micrometer structures are generated to modify polyethylene (PE) surface topographies. These surfaces were subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. The results reveal that the nanostructures do not influence S. aureus coverage, while the adhesion of E. coli is reduced.

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

The pursuit of antibacterial properties on the surfaces of food container, medical equipment, and pharmaceutical tanks has been a compelling challenge for decades. Inspired by the biomimetic superhydrophobic surfaces that have self-cleaning, antifog, antisnow, and reduced bacterial adhesion properties, we use a simple and effective technology of a picosecond laser texturing for the fabrication of a superhydrophobic antibacterial surface on AISI 420 martensitic stainless steel plates. The laser-textured surface with micropapillae patterns with superimposed nanostructures exhibits outstanding in-air superhydrophobic and superaerophilicity underwater, which under the oscillation state resists an adhesion of 99% Escherichia coli and 93% Staphylococcus aureus and has hardly any bacterial adhesion under a stationary state. The comparative experiments verify that the robust air layer and hierarchical micro-nanostructures have come together to comprise the antibacterial mechanism. The laser-textured superhydrophobic surface also exhibits superior anticorrosion and antidestructive abilities with excellent antibacterial durability especially if deep cleaning is carried out after each dipping time in the bacterial suspension, promoting its leading-edge applications in medical, food, and pharmaceutical fields.

Multi-biofunctional properties of three species of cicada wings and biomimetic fabrication of nanopatterned titanium pillars

Recently, multi-biofunctional properties of cicada wings have drawn keen interest for biomedical device applications due to their superhydrophobic, self-cleaning and bactericidal effects. We present a systematic evaluation of bactericidal and cytocompatible properties of cicada wings. We also present biomimetic nanofabrication of a patterned array of titanium nanopillars using electron beam lithography. We have characterized the nanoscale architecture of the wings of three different Australian species of cicadas (Psaltoda claripennis, Aleeta curvicosta and Palapsalta eyrei) using helium ion microscopy (HIM), scanning electron microscopy, atomic force measurement (AFM) and transmission electron microscopy (TEM). The chemical nature of the nanopatterned substrates was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Pseudomonas aeruginosa and Staphylococcus aureus cells were attached to determine the bactericidal activity of the insect wings. Human osteoblast cells were attached to examine the biocompatibility of the insect wings. It was found that all the three cicada species have unique surface topography on their wing membranes and veins. The height, spacing, diameter, density and aspect ratio of the three species varied between the species and between the membrane and the veins. The density and aspect ratio of the nanopillars on the membranes were significantly higher than on the veins. Bacterial attachment investigation confirmed that P. aeruginosa cells and S. aureus cells were damaged by the nanopatterned array of pillars. A significant reduction in colonies of P. aeruginosa cells was found on the wings of the three species compared to the control after 18 hours. A significant reduction of S. aureus cells on the wings was observed at 2 and 4 hours but not at 18 hours compared to the control. The cell morphology of the human osteoblast cells appeared intact after 24 hours of attachment, indicating the biocompatibility of the insect wings. As a proof of concept, patterned nanopillars of titanium have been fabricated using the electron beam lithography technique directly inspired by the cicada wing architecture. The titanium nanopillars were observed to damage the bacterial cells of P. aeruginosa in a manner similar to the cicada wing species and remain compatible to osteoblast cells. The outcomes of this research can help to engineer an optimum nano-patterned surface to enhance the bioactivity and bactericidal effect on biomedical devices.