Nanocolumnar coatings with selective behavior towards osteoblast and Staphylococcus aureus proliferation

In vitro co-culture models for the assessment of orthopedic antibacterial biomaterials

The antibacterial biofunctionality of bone implants is essential for the prevention and treatment of implant-associated infections (IAI). In vitro co-culture models are utilized to assess this and study bacteria-host cell interactions at the implant interface, aiding our understanding of biomaterial and the immune response against IAI without impeding the peri-implant bone tissue regeneration. This paper reviews existing co-culture models together with their characteristics, results, and clinical relevance. A total of 36 studies were found involving in vitro co-culture models between bacteria and osteogenic or immune cells at the interface with orthopedic antibacterial biomaterials. Most studies (∼67%) involved co-culture models of osteogenic cells and bacteria (osteo-bac), while 33% were co-culture models of immune cells and bacterial cells (im-bac). All models involve direct co-culture of two different cell types. The cell seeding sequence (simultaneous, bacteria-first, and cell-first) was used to mimic clinically relevant conditions and showed the greatest effect on the outcome for both types of co-culture models. The im-bac models are considered more relevant for early peri-implant infections, whereas the osteo-bac models suit late infections. The limitations of the current models and future directions to develop more relevant co-culture models to address specific research questions are also discussed.

Mesoporous Bioactive Nanoparticles for Bone Tissue Applications

Research in nanomaterials with applications in bone regeneration therapies has experienced a very significant advance with the development of bioactive mesoporous nanoparticles (MBNPs). These nanomaterials consist of small spherical particles that exhibit chemical properties and porous structures that stimulate bone tissue regeneration, since they have a composition similar to that of conventional sol-gel bioactive glasses and high specific surface area and porosity values. The rational design of mesoporosity and their ability to incorporate drugs make MBNPs an excellent tool for the treatment of bone defects, as well as the pathologies that cause them, such as osteoporosis, bone cancer, and infection, among others. Moreover, the small size of MBNPs allows them to penetrate inside the cells, provoking specific cellular responses that conventional bone grafts cannot perform. In this review, different aspects of MBNPs are comprehensively collected and discussed, including synthesis strategies, behavior as drug delivery systems, incorporation of therapeutic ions, formation of composites, specific cellular response and, finally, in vivo studies that have been performed to date.

Nanomaterial-assisted theranosis of bone diseases

Bone-related diseases refer to a group of skeletal disorders that are characterized by bone and cartilage destruction. Conventional approaches can regulate bone homeostasis to a certain extent. However, these therapies are still associated with some undesirable problems. Fortunately, recent advances in nanomaterials have provided unprecedented opportunities for diagnosis and therapy of bone-related diseases. This review provides a comprehensive and up-to-date overview of current advanced theranostic nanomaterials in bone-related diseases. First, the potential utility of nanomaterials for biological imaging and biomarker detection is illustrated. Second, nanomaterials serve as therapeutic delivery platforms with special functions for bone homeostasis regulation and cellular modulation are highlighted. Finally, perspectives in this field are offered, including current key bottlenecks and future directions, which may be helpful for exploiting nanomaterials with novel properties and unique functions. This review will provide scientific guidance to enhance the development of advanced nanomaterials for the diagnosis and therapy of bone-related diseases.

Influence of Indium (III) Chloride on Human Dermal Fibroblast Cell Adhesion on Tantalum/Silicon Oxide Nano-Composites

Cell adhesion is an essential biological function for division, migration, signaling and tissue development. While it has been demonstrated that this cell function can be modified by using nanometer-scale surface topographic structures, it remains unknown how contaminants such as indium (III) ion might influence this specific cell behavior. Herein, the influence of indium chloride on human dermal fibroblast (GM5565) adhesion characteristics was investigated, given the frequent contact of contaminants with skin. The morphology of the adherent cells and their mitochondrial reticulum was characterized on cell culture dishes and nanopatterned surfaces by using fluorescence confocal microscopy and scanning electron microscopy. Results showed a significant proportion of cells lost their ability to align preferentially along the line axes of the nanopattern upon exposure to 3.2 mM indium chloride, with cells aligned within 10° of the pattern line axes reduced by as much as ~70%. Concurrent with the cell adhesion behaviors, the mitochondria in cells exposed to indium chloride exhibit a punctate staining that contrasts with the normal network of elongated tubular geometry seen in control cells. Our results demonstrate that exposure to indium chloride has detrimental effects on the behavior of human fibroblasts and adversely impacts their mitochondrial morphology. This shows the importance of evaluating the biological impacts of indium compounds.

Effects of nanostructuration on the electrochemical performance of metallic bioelectrodes

The use of metallic nanostructures in the fabrication of bioelectrodes (e.g., neural implants) is gaining attention nowadays. Nanostructures provide increased surface area that might benefit the performance of bioelectrodes. However, there is a need for comprehensive studies that assess electrochemical performance of nanostructured surfaces in physiological and relevant working conditions. Here, we introduce a versatile scalable fabrication method based on magnetron sputtering to develop analogous metallic nanocolumnar structures (NCs) and thin films (TFs) from Ti, Au, and Pt. We show that NCs contribute significantly to reduce the impedance of metallic surfaces. Charge storage capacity of Pt NCs is remarkably higher than that of Pt TFs and that of the other metals in both morphologies. Circuit simulations of the electrode/electrolyte interface show that the signal delivered in voltage-controlled systems is less filtered when nanocolumns are used. In a current-controlled system, simulation shows that NCs provide safer stimulation conditions compared to TFs. We have assessed the durability of NCs and TFs for potential use in vivo by reactive accelerated aging test, mimicking one-year in vivo implantation. Although each metal/morphology reveals a unique response to aging, NCs show overall more stable electrochemical properties compared to TFs in spite of their porous structure.

Nosocomial Infections and Role of Nanotechnology

Nosocomial infections, termed hospital-acquired infections (HAIs), are acquired from a healthcare or hospital setting. HAI is mainly caused by bacteria, such as Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, Enterococci spp., Methicillin-resistant Staphylococcus aureus (MRSA), and many more. Due to growing antibacterial resistance, nanotechnology has paved the way for more potent and sensitive methods of detecting and treating bacterial infections. Nanoparticles have been used with molecular beacons for identifying bactericidal activities, targeting drug delivery, and anti-fouling coatings, etc. This review addresses the looming threat of nosocomial infections, with a focus on the Indian scenario, and major initiatives taken by medical bodies and hospitals in spreading awareness and training. Further, this review focuses on the potential role nanotechnology can play in combating the spread of these infections.

A versatile multicomponent mesoporous silica nanosystem with dual antimicrobial and osteogenic effects

In this manuscript, we propose a simple and versatile methodology to design nanosystems based on biocompatible and multicomponent mesoporous silica nanoparticles (MSNs) for infection management. This strategy relies on the combination of antibiotic molecules and antimicrobial metal ions into the same nanosystem, affording a significant improvement of the antibiofilm effect compared to that of nanosystems carrying only one of these agents. The multicomponent nanosystem is based on MSNs externally functionalized with a polyamine dendrimer (MSN-G3) that favors internalization inside the bacteria and allows the complexation of multiactive metal ions (MSN-G3-Mⁿ⁺). Importantly, the selection of both the antibiotic and the cation may be done depending on clinical needs. Herein, levofloxacin and Zn²⁺ ion, chosen owing to both its antimicrobial and osteogenic capability, have been incorporated. This dual biological role of Zn²⁺ could have and adjuvant effect thought destroying the biofilm in combination with the antibiotic as well as aid to the repair and regeneration of lost bone tissue associated to osteolysis during infection process. The versatility of the nanosystem has been demonstrated incorporating Ag⁺ ions in a reference nanosystem. In vitro antimicrobial assays in planktonic and biofilm state show a high antimicrobial efficacy due to the combined action of levofloxacin and Zn²⁺, achieving an antimicrobial efficacy above 99% compared to the MSNs containing only one of the microbicide agents. In vitro cell cultures with MC3T3-E1 preosteoblasts reveal the osteogenic capability of the nanosystem, showing a positive effect on osteoblastic differentiation while preserving the cell viability. STATEMENT OF SIGNIFICANCE: A simple and versatile methodology to design biocompatible and multicomponent MSNs based nanosystems for infection management is proposed. These nanosystems, containing two antimicrobial agents, levofloxacin and Zn²⁺, have been synthetized by external functionalization of MSNs with a polycationic dendrimer (MSNs-G3), which favours its internalization inside the bacteria and lead the complexation with metal ions through the amines of the dendrimer. The nanosystems offer a notable improvement of the antibiofilm effect (above 99%) than both components separately as well as osteogenic capability with positive effect on the osteoblastic differentiation and preserved cell viability.

Influence of Bioinspired Lithium-Doped Titanium Implants on Gingival Fibroblast Bioactivity and Biofilm Adhesion

Soft tissue integration (STI) at the transmucosal level around dental implants is crucial for the long-term success of dental implants. Surface modification of titanium dental implants could be an effective way to enhance peri-implant STI. The present study aimed to investigate the effect of bioinspired lithium (Li)-doped Ti surface on the behaviour of human gingival fibroblasts (HGFs) and oral biofilm in vitro. HGFs were cultured on various Ti surfaces—Li-doped Ti (Li_Ti), NaOH_Ti and micro-rough Ti (Control_Ti)—and were evaluated for viability, adhesion, extracellular matrix protein expression and cytokine secretion. Furthermore, single species bacteria (Staphylococcus aureus) and multi-species oral biofilms from saliva were cultured on each surface and assessed for viability and metabolic activity. The results show that both Li_Ti and NaOH_Ti significantly increased the proliferation of HGFs compared to the control. Fibroblast growth factor-2 (FGF-2) mRNA levels were significantly increased on Li_Ti and NaOH_Ti at day 7. Moreover, Li_Ti upregulated COL-I and fibronectin gene expression compared to the NaOH_Ti. A significant decrease in bacterial metabolic activity was detected for both the Li_Ti and NaOH_Ti surfaces. Together, these results suggest that bioinspired Li-doped Ti promotes HGF bioactivity while suppressing bacterial adhesion and growth. This is of clinical importance regarding STI improvement during the maintenance phase of the dental implant treatment.

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.

Regulation of cell locomotion by nanosecond-laser-induced hydroxyapatite patterning

Hydroxyapatite, an essential mineral in human bones composed mainly of calcium and phosphorus, is widely used to coat bone graft and implant surfaces for enhanced biocompatibility and bone formation. For a strong implant-bone bond, the bone-forming cells must not only adhere to the implant surface but also move to the surface requiring bone formation. However, strong adhesion tends to inhibit cell migration on the surface of hydroxyapatite. Herein, a cell migration highway pattern that can promote cell migration was prepared using a nanosecond laser on hydroxyapatite coating. The developed surface promoted bone-forming cell movement compared with the unpatterned hydroxyapatite surface, and the cell adhesion and movement speed could be controlled by adjusting the pattern width. Live-cell microscopy, cell tracking, and serum protein analysis revealed the fundamental principle of this phenomenon. These findings are applicable to hydroxyapatite-coated biomaterials and can be implemented easily by laser patterning without complicated processes. The cell migration highway can promote and control cell movement while maintaining the existing advantages of hydroxyapatite coatings. Furthermore, it can be applied to the surface treatment of not only implant materials directly bonded to bone but also various implanted biomaterials implanted that require cell movement control.

Nanomaterials as a Successor of Antibiotics in Antibiotic-Resistant, Biofilm Infected Wounds?

Chronic wounds are a growing problem for both society and patients. They generate huge costs for treatment and reduce the quality of life of patients. The greatest challenge when treating a chronic wound is prolonged infection, which is commonly caused by biofilm. Biofilm makes bacteria resistant to individuals’ immune systems and conventional treatment. As a result, new treatment options, including nanomaterials, are being tested and implemented. Nanomaterials are particles with at least one dimension between 1 and 100 nM. Lipids, liposomes, cellulose, silica and metal can be carriers of nanomaterials. This review’s aim is to describe in detail the mode of action of those molecules that have been proven to have antimicrobial effects on biofilm and therefore help to eradicate bacteria from chronic wounds. Nanoparticles seem to be a promising treatment option for infection management, which is essential for the final stage of wound healing, which is complete wound closure.

The Synergy of Topographical Micropatterning and Ta|TaCu Bilayered Thin Film on Titanium Implants Enables Dual-Functions of Enhanced Osteogenesis and Anti-Infection

Poor osteogenesis and implant-associated infection are the two leading causes of failure for dental and orthopedic implants. Surface design with enhanced osteogenesis often fails in antibacterial activity, or vice versa. Herein, a surface design strategy, which overcomes this trade-off via the synergistic effects of topographical micropatterning and a bilayered nanostructured metallic thin film is presented. A specific microgrooved pattern is fabricated on the titanium surface, followed by sequential deposition of a nanostructured copper (Cu)-containing tantalum (Ta) (TaCu) layer and a pure Ta cap layer. The microgrooved patterns coupled with the nanorough Ta cap layer shows strong contact guidance to preosteoblasts and significantly enhances the osteogenic differentiation in vitro, while the controlled local sustained release of Cu ions is responsible for high antibacterial activity. Importantly, rat calvarial defect models in vivo further confirm that the synergy of microgrooved patterns and the Ta|TaCu bilayered thin film on titanium surface could effectively promote bone regeneration. The present effective and versatile surface design strategy provides significant insight into intelligent surface engineering that can control biological response at the site of healing in dental and orthopedic implants.

Topographical nanostructures for physical sterilization

The development in nanobiotechnology provides an in-depth understanding of cell-surface interactions at the nanoscale level. Particularly, several surface features have shown the ability to interrogate the bacterial behavior and fate. In the past decade, the mechanical and physical sterilization has attracted considerable attention, as paradigms of such do not rely on chemical substances to damage or kill bacteria, whereas it is associated with natural living organisms or synthetic materials. Of note, such antibacterial scenario does not cause bacterial resistance, as the morphology of nanometer can directly cause bacterial death through physical and mechanical interactions. In this review, we provide an overview of recently developed technologies of leveraging topographical nanofeatures for physical sterilization. We mainly discuss the development of various morphologic nanostructures, and colloidal nanostructures show casing the capacity of "mechanical sterilization." Mechanically sterilized nanostructures can penetrate or cut through bacterial membranes. In addition, surface morphology, such as mechanical bactericidal nanoparticles and nanoneedles, can cause damage to the membrane of microorganisms, leading to cell lysis and death. Although the research in the field of mechanical sterilization is still in infancy, the effect of these nanostructure morphologies on sterilization has shown remarkable antibacterial potential, which could provide a new toolkit for anti-infection and antifouling applications. The mechanical and physical sterilization has attracted considerable attention, as paradigms of such do not rely on chemical substances to damage or kill bacteria. Moreover, such antibacterial scenario does not cause bacterial resistance, as the morphology of nanometer can directly cause bacterial death through physical and mechanical interactions. In this review, we focus on the advanced development of various morphologic nanostructures and colloidal nanostructures that show the capacity of "mechanical sterilization."

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.

Biomaterials against Bone Infection

Chronic bone infection is considered as one of the most problematic biofilm-related infections. Its recurrent and resistant nature, high morbidity, prolonged hospitalization, and costly medical care expenses have driven the efforts of the scientific community to develop new therapies to improve the standards used today. There is great debate on the management of this kind of infection in order to establish consistent and agreed guidelines in national health systems. The scientific research is oriented toward the design of anti-infective biomaterials both for prevention and cure. The properties of these materials must be adapted to achieve better anti-infective performance and good compatibility, which allow a good integration of the implant with the surrounding tissue. The objective of this review is to study in-depth the antibacterial biomaterials and the strategies underlying them. In this sense, this manuscript focuses on antimicrobial coatings, including the new technological advances on surface modification; scaffolding design including multifunctional scaffolds with both antimicrobial and bone regeneration properties; and nanocarriers based on mesoporous silica nanoparticles with advanced properties (targeting and stimuli-response capabilities).

Preparation of Low-Resistance and Residue-free ITO Films for Large-scale 3D Displays

The large-sized naked-eye three-dimensional (3D) display is a critical device in the real-time topographic survey for deep-sea scientific research. As a core component, the low-impedance transparent conductive indium tin oxide (ITO) thin-film electrode lacks a reliable industrial preparation method. In the 3D display, the grating element with a low-resistance ITO film electrode should have a good binocular parallax to drive the display favorably. However, an increase in the ITO film temperature during deposition may induce its crystallization, and its etching residue may cause a short circuit between the ITO electrodes and abnormal display operation. In this work, we propose a simple and straightforward technique to produce amorphous thin ITO films by controlling the water vapor flow rate during the deposition process. The obtained ITO amorphous thick film (300 nm) can be etched without leaving residues on the display surface, ensuring vivid display performance of the 3D display. A field test employing the 3D display, consisting of a 3D parallax barrier and a two-dimensional (2D) display, does not exhibit a short-circuit phenomenon caused by residues encountered in previous devices. This work makes the 3D display applicable for the real-time topographic survey on the basis of both satisfying the nonetching residue and the decrease of the resistance value.

Tunable morphological changes of asymmetric titanium nanosheets with bactericidal properties

HYPOTHESIS

Titanium and titanium alloys are often the most popular choice of material for the manufacture of medical implants; however, they remain susceptible to the risk of device-related infection caused by the presence of pathogenic bacteria. Hydrothermal etching of titanium surfaces, to produce random nanosheet topologies, has shown remarkable ability to inactivate pathogenic bacteria via a physical mechanism. We expect that systematic tuning of the nanosheet morphology by controlling fabrication parameters, such as etching time, will allow for optimisation of the surface pattern for superior antibacterial efficacy.

EXPERIMENTS

Using time-dependent hydrothermal processing of bulk titanium, we fabricated bactericidal nanosheets with variable nanoedge morphologies according to a function of etching time. A systematic study was performed to compare the bactericidal efficiency of nanostructured titanium surfaces produced at 0.5, 1, 2, 3, 4, 5, 6, 24 and 60 h of hydrothermal etching.

FINDINGS

Titanium surfaces hydrothermally treated for a period of 6 h were found to achieve maximal antibacterial efficiency of 99 ± 3% against Gram-negative Pseudomonas aeruginosa and 90 ± 9% against Gram-positive Staphylococcus aureus bacteria, two common human pathogens. These surfaces exhibited nanosheets with sharp edges of approximately 10 nm. The nanotopographies presented in this work exhibit the most efficient mechano-bactericidal activity against both Gram-negative and Gram-positive bacteria of any nanostructured titanium topography reported thus far.

Antibacterial Nanostructured Ti Coatings by Magnetron Sputtering: From Laboratory Scales to Industrial Reactors

Based on an already tested laboratory procedure, a new magnetron sputtering methodology to simultaneously coat two-sides of large area implants (up to ~15 cm²) with Ti nanocolumns in industrial reactors has been developed. By analyzing the required growth conditions in a laboratory setup, a new geometry and methodology have been proposed and tested in a semi-industrial scale reactor. A bone plate (DePuy Synthes) and a pseudo-rectangular bone plate extracted from a patient were coated following the new methodology, obtaining that their osteoblast proliferation efficiency and antibacterial functionality were equivalent to the coatings grown in the laboratory reactor on small areas. In particular, two kinds of experiments were performed: Analysis of bacterial adhesion and biofilm formation, and osteoblasts–bacteria competitive in vitro growth scenarios. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation, demonstrating that the proposed methodology represents a valid approach for industrial production and practical application of nanostructured titanium coatings.

Nanomaterials as Promising Alternative in the Infection Treatment

Both the prevalence of antibiotic resistance and the increased biofilm-associated infections are boosting the demand for new advanced and more effective treatment for such infections. In this sense, nanotechnology offers a ground-breaking platform for addressing this challenge. This review shows the current progress in the field of antimicrobial inorganic-based nanomaterials and their activity against bacteria and bacterial biofilm. Herein, nanomaterials preventing the bacteria adhesion and nanomaterials treating the infection once formed are presented through a classification based on their functionality. To fight infection, nanoparticles with inherent antibacterial activity and nanoparticles acting as nanovehicles are described, emphasizing the design of the carrier nanosystems with properties targeting the bacteria and the biofilm.

Rapid mineralization of hierarchical poly(l-lactic acid)/poly(ε-caprolactone) nanofibrous scaffolds by electrodeposition for bone regeneration

Introduction: Hierarchical nanofibrous scaffolds are emerging as a promising bone repair material due to their high cell adhesion activity and nutrient permeability. However, the existing method for hierarchical nanofibrous scaffolds fabrication is complicated and not perfectly suitable for further biomedical application in view of both structure and function. In this study, we constructed a hierarchical nanofibrous poly (l-lactic acid)/poly(ε-caprolactone) (PLLA/PCL) scaffold and further evaluated its bone healing ability. Methods: The hierarchical PLLA/PCL nanofibrous scaffold (PLLA/PCL) was prepared by one-pot TIPS and then rapidly mineralized at room temperature by an electrochemical deposition technique. After electrode-positioning at 2 V for 2 hrs, a scaffold coated with hydroxyapatite (M-PLLA/PCL) could be obtained. Results: The pore size of the M-PLLA/PCL scaffold was hierarchically distributed so as to match the biophysical structure for osteoblast growth. The M-PLLA/PCL scaffold showed better cell proliferation and osteogenesis activity compared to the PLLA/PCL scaffold. Further in vivo bone repair studies indicated that the M-PLLA/PCL scaffold could accelerate defect healing in 12 weeks. Conclusion: The results of this study implied that the as-prepared hydroxyapatite coated hierarchical PLLA/PCL nanofibrous scaffolds could be developed as a promising material for efficient bone tissue repair after carefully tuning the TIPS and electrodeposition parameters.

Cytocompatible and Anti-bacterial Adhesion Nanotextured Titanium Oxide Layer on Titanium Surfaces for Dental and Orthopedic Implants

It is widely recognized that surface nanotextures applied on a biomaterial can affect wettability, protein absorption and cellular and/or bacterial adhesion; accordingly, they are nowadays of great interest to promote fast osseointegration and to maintain physiological healing around biomedical implants. In order to be suitable for clinical applications, surface nanotextures must be not only safe and effective, but also, they should be produced through industrial processes scalable to real devices with sustainable processes and costs: this is often a barrier to the market entry. Based on these premises, a chemical surface treatment designed for titanium and its alloys able to produce an oxide layer with a peculiar sponge like nanotexture coupled with high density of hydroxyl group is here presented. The modified Ti-based surfaces previously showed inorganic bioactivity intended as the ability to induce apatite precipitation in simulated body fluid. Physicochemical properties and morphology of the obtained layers have been characterized by means of FESEM, XPS, and Zeta-potential. Biological response to osteoblasts progenitors and bacteria has been tested. The here proposed nanotextured surfaces successfully supported osteoblasts progenitors' adhesion, proliferation and extracellular matrix deposition thus demonstrating good biocompatibility. Moreover, the nanotexture was able to significantly reduce bacteria surface colonization when the orthopedic and the periodontal pathogens Staphylococcus aureus and Aggregatibacter actinomycetemcomitans strains were applied for a short time. Finally, the applicability of the proposed surface treatment to real biomedical devices (a 3D acetabular cup, a dental screw and a micro-sphered laryngeal implant) has been here demonstrated.

Advanced antibacterial activity of biocompatible tantalum nanofilm via enhanced local innate immunity

Tantalum (Ta) has been shown to enhance osseointegration in clinical practice, yet little is known about whether Ta nanofilms can be used as antimicrobial coatings in vivo. A highly biocompatible Ta nanofilm was developed using magnetron sputtering technology to further study the mechanism of its antibacterial effects in vivo and elucidate its potential for clinical translation. The Ta nanofilms exhibited effective antimicrobial activity against soft tissue infections but did not show an intrinsic antimicrobial effect in vitro. This inconsistency between the in vivo and in vitro antimicrobial effects was further investigated using ex vivo models. The Ta nanofilms could enhance the phagocytosis of bacteria by polymorphonuclear neutrophils (PMNs, neutrophils), reduce the lysis of neutrophils and enhance the proinflammatory cytokine release of macrophages. This accumulative enhancement of the local host defenses contributed to the favorable antibacterial effect in vivo. The alleviated osteolysis observed in the presence of the Ta nanofilms in the osteomyelitis model further proved the practicality of this antibacterial strategy in the orthopedic field. In summary, Ta nanofilms show excellent biocompatibility and in vivo antimicrobial activity mediated by the enhancement of local innate immunity and are promising for clinical application. STATEMENT OF SIGNIFICANCE: In this study, Ta nanofilms were deposited on titanium substrate by magnetron sputtering. Ta nanofilms exhibited excellent in vivo and in vitro biocompatibility. In vivo antimicrobial effects of Ta nanofilms were revealed by soft tissue infection and osteomyelitis models, while no direct antibacterial activity was observed in vitro. Comprehensive ex vivo models revealed that Ta nanofilms could enhance the phagocytosis of bacteria by neutrophils, reduce the lysis of neutrophils and promote the release of proinflammatory cytokines from macrophages. This immunomodulatory effect helps host to eliminate bacteria. In contrast to traditional antimicrobial nanocoatings which apply toxic materials to kill bacteria, this work proposes a safe, practical and effective Ta nanofilm immunomodulatory antimicrobial strategy with clinical translational prospect.

Fabrication of a nanoparticle-containing 3D porous bone scaffold with proangiogenic and antibacterial properties

3D porous scaffolds based on agarose and nanocrystalline apatite, two structural components that act as a temporary mineralized extracellular matrix, were prepared by the GELPOR3D method. This shaping technology allows the introduction of thermally-labile molecules within the scaffolds during the fabrication procedure. An angiogenic protein, Vascular Endothelial Growth Factor, and an antibiotic, cephalexin, loaded in mesoporous silica nanoparticles, were included to design multifunctional scaffolds for bone reconstruction. The dual release of both molecules showed a marked increase in the number of blood vessels on embryonic day 14 in chicken embryos grown ex ovo, while, at the same time providing an antibiotic local concentration capable of inhibiting Staphylococcus aureus bacterial growth. In this sense, different release patterns, monitored by UV-spectroscopy, could be tailored as a function of the cephalexin loading strategy, either releasing all the loaded cephalexin in the first 4 h or less than 50% after 24 h. The scaffold surface was characterized by a high hydrophilicity, with contact angles between 50° and 63°, which enabled the adhesion and proliferation of preosteoblastic cells. STATEMENT OF SIGNIFICANCE: The localized delivery of bioactive molecules has attracted significant attention due to the potential for dose reduction as well as reduced side effects compared to systemic delivery. In this article multifunctional 3D porous scaffolds with a designed porosity have been fabricated. The method also enables the controlled loading of an antibiotic drug and an angiogenic protein into the scaffold. These scaffolds, whose composition resembles the extracellular matrix are suitable for the adhesion of preosteoblast cells, exhibit a sustained cephalexin delivery adequate for inhibiting bacterial growth as well as release the proangiogenic molecule which induces blood vessel formation in chicken embryos grown ex ovo.

Synergic antibacterial coatings combining titanium nanocolumns and tellurium nanorods

Nanocolumnar titanium coatings have been fabricated in two sputtering systems with very different characteristics (a laboratory setup and semi-industrial equipment), thus possessing different morphologies (150 nm long columns tilted 20° from the normal and 300 nm long ones tilted 40°, respectively). These coatings exhibit similar antibacterial properties against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria. When a synergic route is followed and these coatings are functionalized with tellurium (Te) nanorods, the antibacterial properties are enhanced, especially for the long nanocolumns case. The biocompatibility is preserved in all the nanostructured coatings.

Glancing-Angle Deposition of Nanostructures on an Implant Material Surface

Cell-compatible and antibacterial surfaces are needed for implants, which frequently have complex and rough surfaces. Bio-inspired columnar nanostructures can be grown on flat substrates; however, the application of these nanostructures on clinically relevant, complex, and rough surfaces was pending. Therefore, a titanium plasma spray (TPS) implant surface was coated with titanium nano-spikes via glancing angle magnetron sputter deposition (GLAD) at room temperature. Using GLAD, it was possible to cover the three-dimensional, highly structured macroscopic surface (including cavities, niches, clefts, and curved areas) of the TPS homogeneously with nano-spikes (TPS+), creating a cell-compatible and antibacterial surface. The adherence and spreading of mesenchymal stem cells (MSC) were similar for TPS and TPS+ surfaces. However, MSC adherent to TPS+ expressed less and shorter pseudopodia. The induced osteogenic response of MSC was significantly increased in cells cultivated on TPS+ compared with TPS. In addition, Gram-negative bacteria (E. coli) adherent to the nano-spikes were partly destructed by a physico-mechanical mechanism; however, Gram-positive bacteria (S. aureus) were not significantly damaged.

Recent advances in functional nanostructured materials for bone-related diseases

Bone-related diseases seriously threaten people's health and research studies have been dedicated towards searching for new and effective treatment methods. Nanotechnologies have opened up a new field in recent decades and nanostructured materials, which exist in a variety of forms, are considered to be promising materials in this field. This article reviews the most recent progress in the development of nanostructured materials for bone-related diseases, including osteoporosis, osteoarthritis, bone metastasis, osteomyelitis, myeloma, and bone defects. We highlight the advantages and functions of nanostructured materials, including sustained release, bone targeting, scaffolding in bone tissue engineering, etc., in bone-related diseases. We also include the remaining challenges of these emerging materials.

Bactericidal effects of nanopatterns: A systematic review

We systematically reviewed the currently available evidence on how the design parameters of surface nanopatterns (e.g. height, diameter, and interspacing) relate to their bactericidal behavior. The systematic search of the literature resulted in 46 studies that satisfied the inclusion criteria of examining the bactericidal behavior of nanopatterns with known design parameters in absence of antibacterial agents. Twelve of the included studies also assessed the cytocompatibility of the nanopatterns. Natural and synthetic nanopatterns with a wide range of design parameters were reported in the included studies to exhibit bactericidal behavior. However, most design parameters were in the following ranges: heights of 100-1000 nm, diameters of 10-300 nm, and interspacings of  <500 nm. The most commonly used type of nanopatterns were nanopillars, which could kill bacteria in the following range of design parameters: heights of 100-900 nm, diameters of 20-207 nm, and interspacings of 9-380 nm. The vast majority of the cytocompatibility studies (11 out of 12) showed no adverse effects of bactericidal nanopatterns with the only exception being nanopatterns with extremely high aspect ratios. The paper concludes with a discussion on the evidence available in the literature regarding the killing mechanisms of nanopatterns and the effects of other parameters including surface affinity of bacteria, cell size, and extracellular polymeric substance (EPS) on the killing efficiency. STATEMENT OF SIGNIFICANCE: The use of nanopatterns to kill bacteria without the need for antibiotics represents a rapidly growing area of research. However, the optimum design parameters to maximize the bactericidal behavior of such physical features need to be fully identified. The present manuscript provides a systematic review of the bactericidal nanopatterned surfaces. Identifying the effective range of dimensions in terms of height, diameter, and interspacings, as well as covering their impact on mammalian cells, has enabled a comprehensive discussion including the bactericidal mechanisms and the factors controlling the bactericidal efficiency. Overall, this review helps the readers have a better understanding of the state-of-the-art in the design of bactericidal nanopatterns, serving as a design guideline and contributing to the design of future experimental studies.

Multifunctional Coatings and Nanotopographies: Toward Cell Instructive and Antibacterial Implants

In biomaterials science, it is nowadays well accepted that improving the biointegration of dental and orthopedic implants with surrounding tissues is a major goal. However, implant surfaces that support osteointegration may also favor colonization of bacterial cells. Infection of biomaterials and subsequent biofilm formation can have devastating effects and reduce patient quality of life, representing an emerging concern in healthcare. Conversely, efforts toward inhibiting bacterial colonization may impair biomaterial-tissue integration. Therefore, to improve the long-term success of medical implants, biomaterial surfaces should ideally discourage the attachment of bacteria without affecting eukaryotic cell functions. However, most current strategies seldom investigate a combined goal. This work reviews recent strategies of surface modification to simultaneously address implant biointegration while mitigating bacterial infections. To this end, two emerging solutions are considered, multifunctional chemical coatings and nanotopographical features.

Mesoporous Silica Materials as Drug Delivery: "The Nightmare" of Bacterial Infection

Mesoporous silica materials (MSM) have a great surface area and a high pore volume, meaning that they consequently have a large loading capacity, and have been demonstrated to be unique candidates for the treatment of different pathologies, including bacterial infection. In this text, we review the multiple ways of action in which MSM can be used to fight bacterial infection, including early detection, drug release, targeting bacteria or biofilm, antifouling surfaces, and adjuvant capacity. This review focus mainly on those that act as a drug delivery system, and therefore that have an essential characteristic, which is their great loading capacity. Since MSM have advantages in all stages of combatting bacterial infection; its prevention, detection and finally in its treatment, we can venture to talk about them as the "nightmare of bacteria".

The Role of Zwitterionic Materials in the Fight against Proteins and Bacteria

Zwitterionization of biomaterials has been heightened to a potent tool to develop biocompatible materials that are able to inhibit bacterial and non-specific proteins adhesion. This constitutes a major progress in the biomedical field. This manuscript overviews the main functionalization strategies that have been reported up to date to design and develop these advanced biomaterials. On this regard, the recent research efforts that were dedicated to provide their surface of zwitterionic nature are summarized by classifying biomaterials in two main groups. First, we centre on biomaterials in clinical use, concretely bioceramics, and metallic implants. Finally, we revise emerging nanostructured biomaterials, which are receiving growing attention due to their multifunctionality and versatility mainly in the local drug delivery and bone tissue regeneration scenarios.

Antioxidant/Antibacterial Electrospun Nanocoatings Applied onto PLA Films

Polylactic acid (PLA) films were coated by coaxial electrospinning with essential and vegetable oils (clove and argan oils) and encapsulated into chitosan, in order to combine the biodegradability and mechanical properties of PLA substrates with the antimicrobial and antioxidant properties of the chitosan⁻oil nanocoatings. It has been established that the morphology of the electrospun nanocoatings mainly depend on the average molecular weight (MW) of chitosan. Oil beads, encapsulated into the main chitosan nanofibers, were obtained using high-MW chitosan (Chit-H). Oil encapsulated in chitosan naoparticles resulted when low-MW chitosan (Chit-L) was used. The coating layer, with a thickness of 100 ± 20 nm, had greater roughness for the samples containing Chit-H compared with the samples containing Chit-L. The coated PLA films had higher antibacterial activity when the nanocoating contained clove oil rather than when argan oil was used, for both types of chitosan. Nanocoatings containing Chit-H had higher antibacterial activity compared with those containing Chit-L, for both types of oil tested, due to the larger surface area of the rougher nanoscaled morphology of the coating layer that contained Chit-L. The chitosan⁻clove oil combination had higher antioxidant activity compared to the simple chitosan nanocoating, which confirmed their synergistic activities. The low activity of systems containing argan oil was explained by big differences between their chemical composition and viscosity.

Drug Delivery and Bone Infection

Bone infection represents greatest challenge in public health care with serious social and economic implications. The efforts of the scientific community are focused in the development of innovative and advanced biomaterials with anti-infective properties related to their non-fouling, bactericidal and/or antibiofilm capabilities. This chapter aims at thoroughly surveying the different approaches based on silica mesoporous materials (SMMs) for bone infection management. Bacteria repelling surfaces by zwitterionization process, bactericidal effect by implantable devices with antimicrobial local delivery agents and antibiofilm effect by more sophisticated systems based on targeted nanocarriers will be considered.

A comparative in vivo study of strontium-functionalized and SLActive™ implant surfaces in early bone healing

Purpose

Studies have shown that strontium-doped medical applications benefit bone metabolism leading to improved bone healing and osseointegration. Based on this knowledge, the aim of the study was to evaluate the performance of an implant surface, functionalized by a physical vapor deposition (PVD) coating (Ti-Sr-O), designed to yield predictable release of strontium. The Ti-Sr-O functionalized surface is compared to a routinely used, commercially available surface (SLActive™) with respect to bone-to-implant contact (BIC%) and new bone formation (BF%) in two defined regions of interest (ROI-I and ROI-II, respectively).

Materials and methods:

Ti-Sr-O functionalized, SLActive, and Grade 4 titanium implants were inserted in the femoral condyle of adult male New Zealand White rabbits. The PVD magnetron-sputtered Ti-Sr-O surface coating was characterized using scanning electron microscopy (SEM) for morphology and coating thickness. Strontium release and mechanical stability of the coating, under simulated insertion conditions, were evaluated. Furthermore, histomorphometrical BIC and BF were carried out 2 weeks after insertion.

Results

Histomorphometry revealed increased bone formation of Ti-Sr-O with significant differences compared to SLActive and Grade 4 titanium in both regions of interest, ROI-I and ROI-II, at 0–250 µm and 250–500 µm distance from the implant surfaces. Analogous results of bone-to-implant contact were observed for the two modified surfaces.

Conclusion

The results show that a nanopatterned Ti-Sr-O functionalized titanium surface, with sustained release of strontium, increases peri-implant bone volume and could potentially contribute to enhancement of bone anchorage of osseointegrated implants.

Mesoporous silica nanoparticles decorated with polycationic dendrimers for infection treatment

This work aims to provide an effective and novel solution for the treatment of infection by using nanovehicles loaded with antibiotics capable of penetrating the bacterial wall, thus increasing the antimicrobial effectiveness. These nanosystems, named "nanoantibiotics", are composed of mesoporous silica nanoparticles (MSNs), which act as nanocarriers of an antimicrobial agent (levofloxacin, LEVO) localized inside the mesopores. To provide the nanosystem of bacterial membrane interaction capability, a polycationic dendrimer, concretely the poly(propyleneimine) dendrimer of third generation (G3), was covalently grafted to the external surface of the LEVO-loaded MSNs. After physicochemical characterization of this nanoantibiotic, the release kinetics of LEVO and the antimicrobial efficacy of each released dosage were evaluated. Besides, internalization studies of the MSNs functionalized with the G3 dendrimer were carried out, showing a high penetrability throughout Gram-negative bacterial membranes. This work evidences that the synergistic combination of polycationic dendrimers as bacterial membrane permeabilization agents with LEVO-loaded MSNs triggers an efficient antimicrobial effect on Gram-negative bacterial biofilm. These positive results open up very promising expectations for their potential application in new infection therapies.

STATEMENT OF SIGNIFICANCE

Seeking new alternatives to current available treatments of bacterial infections represents a great challenge in nanomedicine. This work reports the design and optimization of a new class of antimicrobial agent, named "nanoantibiotic", based on mesoporous silica nanoparticles (MSNs) decorated with polypropyleneimine dendrimers of third generation (G3) and loaded with levofloxacin (LEVO) antibiotic. The covalently grafting of these G3 dendrimers to MSNs allows an effective internalization in Gram-negative bacteria. Furthermore, the LEVO loaded into the mesoporous cavities is released in a sustained manner at effective antimicrobial dosages. The novelty and originality of this manuscript relies on proving that the synergistic combination of bacteria-targeting and antimicrobial agents into a unique nanosystem provokes a remarkable antimicrobial effect against bacterial biofilm.

Preparation of well-distributed titania nanopillar arrays on Ti6Al4V surface by induction heating for enhancing osteogenic differentiation of stem cells

Great effort has recently been devoted to the preparation of nanoscale surfaces on titanium-based implants to achieve clinically fast osteoinduction and osseointegration, which relies on the unique characteristics of the nanostructure. In this work, we used induction heating treatment (IHT) as a rapid oxidation method to fabricate a porous nanoscale oxide layer on the Ti6Al4V surface for better medical application. Well-distributed vertical nanopillars were yielded by IHT for 20-35 s on the alloy surface. The composition of the oxides contained rutile/anatase TiO₂ and a small amount of Al₂O₃ between the TiO₂ grain boundaries (GBs). This technology resulted in a reduction and subsequent increase of surface roughness of 26-32 nm when upregulating the heating time, followed by the successive enhancement of the thickness, wettability and adhesion strength of the oxidation layer to the matrix. The surface hardness also distinctly rose to 554 HV in the IHT-35 s group compared with the 350 HV of bare Ti6Al4V. The massive small-angle GBs in the bare alloy promoted the formation of nanosized oxide crystallites. The grain refinement and deformation texture reduction further improved the mechanical properties of the matrix after IHT. Moreover, in vitro experiments on a mesenchymal stem cell (BMSC) culture derived from human bone marrow for 1-7 days indicated that the nanoscale layers did not cause cytotoxicity, and facilitated cell differentiation in osteoblasts by enhancing the gene and osteogenesis-related protein expressions after 1-3 weeks of culturing. The increase of the IHT time slightly advanced the BMSC proliferation and differentiation, especially during long-term culture. Our findings provide strong evidence that IHT oxidation technology is a novel nanosurface modification technology, which is potentially promising for further clinical development.

Inhibition of Bacterial Adhesion on Nanotextured Stainless Steel 316L by Electrochemical Etching

Bacterial adhesion to stainless steel 316L (SS316L), which is an alloy typically used in many medical devices and food processing equipment, can cause serious infections along with substantial healthcare costs. This work demonstrates that nanotextured SS316L surfaces produced by electrochemical etching effectively inhibit bacterial adhesion of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, but exhibit cytocompatibility and no toxicity toward mammalian cells in vitro. Additionally, the electrochemical surface modification on SS316L results in formation of superior passive layer at the surface, improving corrosion resistance. The nanotextured SS316L offers significant potential for medical applications based on the surface structure-induced reduction of bacterial adhesion without use of antibiotic or chemical modifications while providing cytocompatibility and corrosion resistance in physiological conditions.

Multifunctional pH sensitive 3D scaffolds for treatment and prevention of bone infection

Multifunctional-therapeutic three-dimensional (3D) scaffolds have been prepared. These biomaterials are able to destroy the S. aureus bacterial biofilm and to allow bone regeneration at the same time. The present study is focused on the design of pH sensitive 3D hierarchical meso-macroporous 3D scaffolds based on MGHA nanocomposite formed by a mesostructured glassy network with embedded hydroxyapatite nanoparticles, whose mesopores have been loaded with levofloxacin (Levo) as antibacterial agent. These 3D platforms exhibit controlled and pH-dependent Levo release, sustained over time at physiological pH (7.4) and notably increased at infection pH (6.7 and 5.5), which is due to the different interaction rate between diverse Levo species and the silica matrix. These 3D systems are able to inhibit the S. aureus growth and to destroy the bacterial biofilm without cytotoxic effects on human osteoblasts and allowing an adequate colonization and differentiation of preosteoblastic cells on their surface. These findings suggest promising applications of these hierarchical MGHA nanocomposite 3D scaffolds for the treatment and prevention of bone infection.

STATEMENT OF SIGNIFICANCE

Multifunctional 3D nanocomposite scaffolds with the ability for loading and sustained delivery of an antimicrobial agent, to eliminate and prevent bone infection and at the same time to contribute to bone regeneration process without cytotoxic effects on the surrounding tissue has been proposed. These 3D scaffolds exhibit a sustained levofloxacin delivery at physiological pH (pH 7.4), which increasing notably when pH decreases to characteristic values of bone infection process (pH 6.7 and pH 5.5). In vitro competitive assays between preosteoblastic and bacteria onto the 3D scaffold surface demonstrated an adequate osteoblast colonization in entire scaffold surface together with the ability to eliminate bacteria contamination.

Structural control in porous/compact multilayer systems grown by magnetron sputtering

In this work we analyze a phenomenon that takes place when growing magnetron sputtered porous/compact multilayer systems by alternating the oblique angle and the classical configuration geometries. We show that the compact layers develop numerous fissures rooted in the porous structures of the film below, in a phenomenon that amplifies when increasing the number of stacked layers. We demonstrate that these fissures emerge during growth due to the high roughness of the porous layers and the coarsening of a discontinuous interfacial region. To minimize this phenomenon, we have grown thin interlayers between porous and compact films under the impingement of energetic plasma ions, responsible for smoothing out the interfaces and inhibiting the formation of structural fissures. This method has been tested in practical situations for compact TiO₂/porous SiO₂ multilayer systems, although it can be extrapolated to other materials and conditions.

Lysine-Grafted MCM-41 Silica as an Antibacterial Biomaterial

This paper proposes a facile strategy for the zwitterionization of bioceramics that is based on the direct incorporation of l-lysine amino acid via the ε-amino group onto mesoporous MCM-41 materials. Fourier transform infrared (FTIR) studies of lysine-grafted MCM-41 (MCM-LYS) simultaneously showed bands at 3080 and 1540 cm-1 and bands at 1625 and 1415 cm-1 corresponding to -NH3+/COO- pairs, which demonstrate the incorporation of the amino acid on the material surface keeping its zwitterionic character. Both elemental and thermogravimetric analyses showed that the amount of grafted lysine was 8 wt. % based on the bioceramic total weight. Moreover, MCM-LYS exhibited a reduction of adhesion of S. aureus and E. coli bacteria in 33% and 50%, respectively at physiological pH, as compared with pristine MCM-41. Biofilm studies onto surfaces showed that lysine functionalization elicited a reduction of the area covered by S. aureus biofilm from 42% to only 5% (88%). This research shows a simple and effective approach to chemically modify bioceramics using single amino acids that provides zwitterionic functionality, which is useful to develop new biomaterials that are able to resist bacterial adhesion.

Antibacterial properties of PEKK for orthopedic applications

Orthopedic implant infections have been steadily increasing while, at the same time, antibiotics developed to kill such bacteria have proven less and less effective with every passing day. It is clear that new approaches that do not rely on the use of antibiotics are needed to decrease medical device infections. Inspired by cicada wing surface topographical features, nanostructured surfaces represent a new approach for imposing antibacterial properties to biomaterials without using drugs. Moreover, new chemistries with altered surface energetics may decrease bacterial attachment and growth. In this study, a nanostructured surface was fabricated on poly-ether-ketone-ketone (PEKK), a new orthopedic implant chemistry, comprised of nanopillars with random interpillar spacing. Specifically, after 5 days, when compared to the orthopedic industry standard poly-ether-ether-ketone (PEEK), more than 37% less Staphylococcus epidermidis were found on the PEKK surface. Pseudomonas aeruginosa attachment and growth also decreased 28% after one day of culture, with around a 50% decrease after 5 days of culture when compared to PEEK. Such decreases in bacteria function were achieved without using antibiotics. In this manner, this study demonstrated for the first time, the promise that nanostructured PEKK has for numerous anti-infection orthopedic implant applications.

Enhanced antifungal activity by disinfected titanium dioxide nanotubes via reduced nano-adhesion bonds

We have provided evidence that the beneficial effect of super-oxidized water (SOW) disinfected Ti6Al4V-TiO₂ nanotubes (NTs) can reduce bacterial adhesion and biofilm formation. However, the need of antifungal nanostructured surfaces with osteoactive capabilities is an important goal that has been arising for dental implants (DI) applications. Thus, in the present study we isolated and tested the effects of Candida albicans (C. albicans) on disinfected, wetter and nanoroughness NTs compared to a non-modified control. Moreover, we elucidated part of the fungal adhesion mechanism by studying and relating the mycotic adhesion kinetics and the formation of fungal nanoadhesion bonds among the experimental materials, to gain new insight of the fungal-material-interface. Similarly, the initial behavior of human alveolar bone osteoblasts (HAOb) was microscopically evaluated. NTs significantly reduced the yeasts adhesion and viability with non-outcomes of biofilm than the non-modified surface. Cross-sectioning of the fungal cells revealed promoted nano-contact bonds with superior fungal spread on the control alloy interface; meanwhile NTs evidenced decreased tendency along time; suggesting, down-regulation by the nanostructured morphology and the SOW treatment. Importantly, the initial performance of HAOb demonstrated strikingly promoted anchorage with effects of filopodia formation and increased vital cell on NTs with SOW. The present study proposes SOW treatment as an active protocol for synthesis and disinfection of NTs with potent antifungal capability, acting in part by the reduction of nano-adhesion bonds at the surface-fungal interface; opening up a novel route for the investigation of mycotic-adhesion processes at the nanoscale for bone implants applications.

3D scaffold with effective multidrug sequential release against bacteria biofilm

Bone infection is a feared complication following surgery or trauma that remains as an extremely difficult disease to deal with. So far, the outcome of therapy could be improved with the design of 3D implants, which combine the merits of osseous regeneration and local multidrug therapy so as to avoid bacterial growth, drug resistance and the feared side effects. Herein, hierarchical 3D multidrug scaffolds based on nanocomposite bioceramic and polyvinyl alcohol (PVA) prepared by rapid prototyping with an external coating of gelatin-glutaraldehyde (Gel-Glu) have been fabricated. These 3D scaffolds contain three antimicrobial agents (rifampin, levofloxacin and vancomycin), which have been localized in different compartments of the scaffold to obtain different release kinetics and more effective combined therapy. Levofloxacin was loaded into the mesopores of nanocomposite bioceramic part, vancomycin was localized into PVA biopolymer part and rifampin was loaded in the external coating of Gel-Glu. The obtained results show an early and fast release of rifampin followed by sustained and prolonged release of vancomycin and levofloxacin, respectively, which are mainly governed by the progressive in vitro degradability rate of these scaffolds. This combined therapy is able to destroy Gram-positive and Gram-negative bacteria biofilms as well as inhibit the bacteria growth. In addition, these multifunctional scaffolds exhibit excellent bioactivity as well as good biocompatibility with complete cell colonization of preosteoblast in the entire surface, ensuring good bone regeneration. These findings suggest that these hierarchical 3D multidrug scaffolds are promising candidates as platforms for local bone infection therapy.

STATEMENT OF SIGNIFICANCE

The present study is focused in finding an adequate therapeutic solution for the treatment of bone infection based on 3D multifunctional scaffolds, which combines the merits of osseous regeneration and local multidrug delivery. These 3D multidrug scaffolds, containing rifampin, levofloxacin and vancomycin, localized in different compartments to achieve different release kinetics. These 3D multidrug scaffolds displays an early and fast release of rifampin followed by sustained and prolonged release of vancomycin and levofloxacin, which are able to destroy Staphylococcus and Escherichia biofilms as well as inhibit bacteria growth in very short time periods. This new combined therapy approach involving the sequential delivery of antibiofilms with antibiotics constitutes an excellent and promising alternative for bone infection treatment.

Nanocolumnar association and domain formation in porous thin films grown by evaporation at oblique angles

Porous thin films grown at oblique angles by evaporation techniques are formed by tilted nanocolumnar structures which, depending on the material type and growth conditions, associate along certain preferential directions, giving rise to large domains. This arrangement, commonly denoted as bundling association, is investigated in the present work by performing fundamental experiments and growth simulations. It is proved that trapping processes of vapor species at the film surface, together with the shadowing mechanism, mediate the anisotropic widening of the nanocolumns and promote their preferential coalescence along certain directions, giving rise to domains with different shape and size. The role of these two processes is thoroughly studied in connection with the formation of these domains in materials as different as SiO2 and TiO2.