Silk fibroin coated TiO2 nanotubes for improved osteogenic property of Ti6Al4V bone implants

The rational design, biofunctionalization and biological properties of orthopedic porous titanium implants: a review

Porous titanium implants are becoming an important tool in orthopedic clinical applications. This review provides a comprehensive survey of recent advances in porous titanium implants for orthopedic use. First, the review briefly describes the characteristics of bone and the design requirements of orthopedic implants. Subsequently, the pore size and structural design of porous titanium alloy materials are presented, then we introduce the application of porous titanium alloy implants in orthopedic clinical practice, including spine surgery, joint surgery, and the treatment of bone tumors. Following that, we describe the surface modifications applied to porous titanium implants to obtain better biological functions. Finally, we discuss incorporating environmental responsive mechanisms into porous titanium alloy materials to achieve additional functionalities.

The synthesis of broccoli sprout extract-loaded silk fibroin nanoparticles as efficient drug delivery vehicles: development and characterization

Targeted drug delivery of biological molecules using the development of biocompatible, non-toxic and biodegradable nanocarriers can be a promising method for cancer therapy. In this study, silk fibroin protein nanoparticles (SFPNPs) were synthesized as a targeted delivery system for sulforaphane-rich broccoli sprout extract (BSE). The BSE-loaded SFPNPs were conjugated with polyethylene glycol and folic acid, and then their physicochemical properties were characterized via UV-Vis, XRD, FTIR, DLS, FE-SEM and EDX analyses. In vitro, the release profile, antioxidant and anticancer activities of NPs were also studied. The FE-SEM and DLS analyses indicated stable NPs with an average size of 88.5 nm and high zeta potential (-32 mV). The sulforaphane release profile from NPs was pH-dependent, with the maximum release value (70%) observed in simulated intestinal fluid (pH = 7.4). Encapsulation of BSE also decreased the release rate of sulforaphane from the capsules compared to free BSE. In vitro cytotoxicity of BSE and NPs on breast cancer cell lines (MCF-7) was concentration-dependent, and the IC50 for BSE and NPs were 54 and 210 μg ml-1, respectively. Moreover, the NPs demonstrated no appreciable cytotoxicity in normal mouse fibroblast (L929) cell lines. These results indicated that biocompatible NPs synthesized as controlled and long-term targeted drug delivery systems can be a potential candidate for breast cancer therapy.

Enhanced antibacterial activity and superior biocompatibility of cobalt-deposited titanium discs for possible use in implant dentistry

The clinical success of implants depends on rapid osseointegration, and new materials are being developed considering the increasing demand. Considering cobalt (Co) antibacterial characteristics, we developed Co-deposited titanium (Ti) using direct current (DC) sputtering and investigated it as a new material for implant dentistry. The material was characterized using atomic absorption spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The material's surface topography, roughness, surface wettability, and hardness were also analyzed. The Co thin film (Ti-Co15) showed excellent antibacterial effects against microbes implicated in peri-implantitis. Furthermore, Ti-Co15 was compatible and favored the attachment and spreading of MG-63 cells. The alkaline phosphatase and calcium mineralization activities of MG-63 cells cultured on Ti-Co15 remained unaltered compared to Ti. These data correlated well with the time-dependent expression of ALP, RUNX-2, and BMP-2 genes involved in osteogenesis. The results demonstrate that Co-deposited Ti could be a promising material in implant dentistry.

Layer-by-Layer Deposition of Regenerated Silk Fibroin─An Approach to the Surface Coating of Biomedical Implant Materials

Biomaterials and coating techniques unlock major benefits for advanced medical therapies. Here, we explored layer-by-layer (LbL) deposition of silk fibroin (SF) by dip coating to deploy homogeneous films on different materials (titanium, magnesium, and polymers) frequently used for orthopedic and other bone-related implants. Titanium and magnesium specimens underwent preceding plasma electrolytic oxidation (PEO) to increase hydrophilicity. This was determined as surface properties were visualized by scanning electron microscopy and contact angle measurements as well as Fourier transform infrared spectroscopy (FTIR) analysis. Finally, biological in vitro evaluations of hemocompatibility, THP-1 cell culture, and TNF-α assays were conducted. A more hydrophilic surface could be achieved using the PEO surface, and the contact angle for magnesium and titanium showed a reduction from 73 to 18° and from 58 to 17°, respectively. Coating with SF proved successful on all three surfaces, and coating thicknesses of up to 5.14 μm (±SD 0.22 μm) were achieved. Using FTIR analysis, it was shown that the insolubility of the material was achieved by post-treatment with water vapor annealing, although the random coil peak (1640-1649 cm-1) and the α-helix peak (at 1650 cm-1) were still evident. SF did not change hemocompatibility, regardless of the substrate, whereas the PEO-coated materials showed improved hemocompatibility. THP-1 cell culture showed that cells adhered excellently to all of the tested material surfaces. Interestingly, SF coatings induced a significantly higher amount of TNF-α for all materials, indicating an inflammatory response, which plays an important role in a variety of physiological processes, including osteogenesis. LbL coatings of SF are shown to be promising candidates to modulate the body's immune response to implants manufactured from titanium, magnesium, and polymers. They may therefore facilitate future applications for bioactive implant coatings. However, further in vivo studies are needed to confirm the proposed effects on osteogenesis in a physiological environment.

Application of silk fibroin coatings for biomaterial surface modification: a silk road for biomedicine

Silk fibroin (SF) as a natural biopolymer has become a popular material for biomedical applications due to its minimal immunogenicity, tunable biodegradability, and high biocompatibility. Nowadays, various techniques have been developed for the applications of SF in bioengineering. Most of the literature reviews focus on the SF-based biomaterials and their different forms of applications such as films, hydrogels, and scaffolds. SF is also valuable as a coating on other substrate materials for biomedicine; however, there are few reviews related to SF-coated biomaterials. Thus, in this review, we focused on the surface modification of biomaterials using SF coatings, demonstrated their various preparation methods on substrate materials, and introduced the latest procedures. The diverse applications of SF coatings for biomedicine are discussed, including bone, ligament, skin, mucosa, and nerve regeneration, and dental implant surface modification. SF coating is conducive to inducing cell adhesion and migration, promoting hydroxyapatite (HA) deposition and matrix mineralization, and inhibiting the Notch signaling pathway, making it a promising strategy for bone regeneration. In addition, SF-coated composite scaffolds can be considered prospective candidates for ligament regeneration after injury. SF coating has been proven to enhance the mechanical properties of the substrate material, and render integral stability to the dressing material during the regeneration of skin and mucosa. Moreover, SF coating is a potential strategy to accelerate nerve regeneration due to its dielectric properties, mechanical flexibility, and angiogenesis promotion effect. In addition, SF coating is an effective and popular means for dental implant surface modification to promote osteogenesis around implants made of different materials. Thus, this review can be of great benefit for further improvements in SF-coated biomaterials, and will undoubtedly contribute to clinical transformation in the future.

Silk Fibroin/ZnO Coated TiO2 Nanotubes for Improved Antimicrobial Effect of Ti Dental Implants

The aim of the present research is to develop a novel hybrid coating for a Ti dental implant that combines nature-inspired biomimetic polymers and TiO2 nanostructures with an entrapped ZnO antimicrobial agent. ZnO was used in other studies to cover the surface of Ti or Ti-Zr to reduce the need of clinical antibiotics, prevent the onset of peri-implantitis, and increase the success rate of oral clinical implantation. We developed an original coating that represents a promising approach in clinical dentistry. The titanium surface was first anodized to obtain TiO2 nanotubes (NT). Subsequently, on the NT surface, silk fibroin isolated from Bombyx mori cocoons was deposited as nanofibers using the electrospun technique. For an improved antibacterial effect, ZnO nanoparticles were incorporated in this biopolymer using three different methods. The surface properties of the newly created coatings were assessed to establish how they are influenced by the most important features: morphology, wettability, topography. The evaluation of stability by electrochemical methods in simulated physiological solutions was discussed more in detail, considering that it could bring necessary information related to the behavior of the implant material. All samples had improved roughness and hydrophilicity, as well as corrosion stability (with protection efficiency over 80%). The antibacterial test shows that the functional hybrid coating has good antibacterial activity because it can inhibit the proliferation of Staphylococcus aureus up to 53% and Enterococcus faecalis up to 55%. All Ti samples with the modified surface have proven superior properties compared with unmodified TiNT, which proved that they have the potential to be used as implant material in dentistry.

Micro/nano-topography promotes osteogenic differentiation of bone marrow stem cells by regulating periostin expression

Micro/nano-topography (MNT) is an important factor affecting cell response. Earlier studies using titania (TiO₂) nanotube as a model of MNT found that they mediated the differentiation of BMSCs into osteoblasts, but the mechanisms are not fully understood. Surprisingly, Periostin (Postn), a secreted protein involved in extracellular matrix (ECM) construction and promoting osteogenic differentiation of bone marrow stem cells (BMSCs), was previously observed to significantly up-regulated on TiO₂ nanotube. We proposed that Postn may act as a MNT signal transduction role. In this study, we investigated the effect of MNT on Postn, and the influence of Postn on osteogenic differentiation-related genes through focal adhesion and downstream signals. It was found that, titanium (Ti) plates carrying TiO₂ nanotubes with diameters of ∼100 nm (TNT-100) significantly up-regulated the expression of Postn compared with flat Ti. Furthermore, Postn activated the downstream focal adhesion kinase (FAK) signal pathway and β-catenin into the nucleus by interacting with integrin αV. Surprisingly, TNT-100 up-regulated the transcription level of Wnt3a, which was independent of the up-regulation of Postn. This new Postn signaling pathway may provide more insights into the signal transduction mechanism of MNT and development of biomaterials with improved osteogenic properties.

Synergistic antibacterial photocatalytic and photothermal properties over bowl-shaped TiO2 nanostructures on Ti-19Zr-10Nb-1Fe alloy

As implant substitutes are increasingly applied to the clinic, the infection caused by implants has become one of the most common complications, and the modification of the antibacterial function of the implant can reduce such complications. In this work, a well-defined bowl-shaped nanostructure coating with photocatalytic and photothermal synergistic antibacterial properties was prepared on Ti-19Zr-10Nb-1Fe (TZNF) alloy. The coating is obtained by spin-coating and sintering TiO2 precursors templated from self-assembled microspheres of polystyrene-poly(4-vinylpyridine) (PS-P4VP) amphiphilic block polymer (BCP) on TZNF alloy. PS-P4VP provides the bowl-shaped TiO2 nanostructures doped with C, N elements, reducing the bandgap of TiO2, which can absorb near-infrared (NIR) light to release reactive oxygen species (ROS) and produce photothermal conversion. The bowl structure is expected to enhance the utilization of light via the reflection in the confined space. The bowl-shaped surface has 100% antibacterial rates after 30 min of NIR light irradiation. In addition to antibacterial properties, the bowl-shaped surface has better hydrophilicity and protein adsorption capacity. The amount of protein adsorbed on TZNF with the bowl-shaped structures was 6 times that of TZNF. Hence, the bowl-shaped nanostructure can promote the proliferation and adhesion of osteoblasts, the cell proliferation rate was increased by 10-30%.

The Deposition of a Lectin from Oreochromis niloticus on the Surface of Titanium Dioxide Nanotubes Improved the Cell Adhesion, Proliferation, and Osteogenic Activity of Osteoblast-like Cells

Titanium and its alloys are used as biomaterials for medical and dental applications, due to their mechanical and physical properties. Surface modifications of titanium with bioactive molecules can increase the osseointegration by improving the interface between the bone and implant. In this work, titanium dioxide nanotubes (TiO2NTs) were functionalized with a lectin from the plasma of the fish Oreochromis niloticus aiming to favor the adhesion and proliferation of osteoblast-like cells, improving its biocompatibility. The TiO2NTs were obtained by anodization of titanium and annealed at 400 °C for 3 h. The resulting TiO2NTs were characterized by high-resolution scanning electron microscopy. The successful incorporation of OniL on the surface of TiO2NTs, by spin coating, was demonstrated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIE), and attenuated total reflection-Fourier transform infrared spectrum (ATR-FTIR). Our results showed that TiO2NTs were successfully synthesized in a regular and well-distributed way. The modification of TiO2NTs with OniL favored adhesion, proliferation, and the osteogenic activity of osteoblast-like cells, suggesting its use to improve the quality and biocompatibility of titanium-based biomaterials.

Electrophoretic deposition of silk fibroin coatings with pre-defined architecture to facilitate precise control over drug delivery

The therapeutic precision and clinical applicability of drug-eluting coatings can be substantially improved by facilitating tunable drug delivery. However, the design of coatings which allows for precise control over drug release kinetics is still a major challenge. Here, a double-layered silk fibroin (SF) coating system was constructed by sequential electrophoretic deposition. A mixture of dissolved Bombyx mori SF (bmSF) molecules and pre-made bmSF nanospheres at different ratios was deposited as under-layer. Subsequently, this underlayer was covered by a top-layer comprising Antheraea pernyi SF (apSF) molecules (rich in arginylglycylaspartic acid, RGD) to improve the cellular response of the resulting double-layered coatings. Additionally, model drug doxycycline was either pre-mixed with dissolved bmSF molecules or pre-loaded into pre-made bmSF nanospheres at the same amount before their mixing and deposition. The thickness and nanosphere content of the under-layer architecture were proportional to the deposition time and nanosphere concentration in precursor mixtures, respectively. The surface topography, wettability, degradation rate and adhesion strength were comparable within the double-layered coating system. As expected, RGD-rich apSF top-layer improved cell adhesion, spreading and proliferation compared with bmSF top-layer. Furthermore, the amount and duration of drug release increased linearly with increasing nanosphere concentration at fixed deposition time, whereas drug release amount increased linearly with increasing deposition time. These results indicate that the dosage and kinetics of loaded drugs can be quantitatively tailored by altering nanosphere concentration and deposition time as main processing parameters. Overall, this study illustrates the strong potential of pre-defining coating architecture to facilitate control over drug delivery.

Properties improvement of titanium alloys scaffolds in bone tissue engineering: a literature review

Owing to their excellent biocompatibility and corrosion-resistant properties, titanium (Ti) (and its alloy) are essential artificial substitute biomaterials for orthopedics. However, flaws, such as weak osteogenic induction ability and higher Young's modulus, have been observed during clinical application. As a result, short- and long-term postoperative follow-up has found that several complications have occurred. For decades, scientists have exerted efforts to compensate for these deficiencies. Different modification methods have been investigated, including changing alloy contents, surface structure transformation, three-dimensional (3D) structure transformation, coating, and surface functionalization technologies. The cell-surface interaction effect and imitation of the natural 3D bone structure are the two main mechanisms of these improved methods. In recent years, significant progress has been made in materials science research methods, including thorough research of titanium alloys of different compositions, precise surface pattern control technology, controllable 3D structure construction technology, improvement of coating technologies, and novel concepts of surface functionalization. These improvements facilitate the possibility for further research in the field of bone tissue engineering. Although the underlying mechanism is still not fully understood, these studies still have some implications for clinical practice. Therefore, for the direction of further research, it is beneficial to summarize these studies according to the basal method used. This literature review aimed to classify these technologies, thereby providing beginners with a preliminary understanding of the field.

Growth of 1D TiO2nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

Different Ti substrates, such as particles (as-received and ball milled), plate and TEM grid were oxidized for the growth of one dimensional (1D) TiO₂nanostructures. The Ti substrates were oxidized for 4 h at temperatures of 700 °C-750 °C in humid and dry Ar containing 5 ppm of O₂. The effects of residual stress on the growth of 1D TiO₂nanostructures were investigated. The residual stress inside the Ti particles was measured by XRD-sin²ψtechnique. The oxidized Ti substrates were characterized using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscope, transmission electron microscope, x-ray diffractometer and x-ray photoelectron spectroscope. Results revealed that humid environment enhances the growth of 1D TiO₂nanostructures. Four different types of 1D morphologies obtained during humid oxidation, e.g. stacked, ribbon, plateau and lamp-post shaped nanostructures. The presence of residual stress significantly enhances the density and coverage of 1D nanostructures. The as-grown TiO₂nanostructures possess tetragonal rutile structure having length up to 10μm along the 〈1 0 1〉 directions. During initial stage of oxidation, a TiO₂layer is formed on Ti substrate. Lower valence oxides (Ti₃O₅, Ti₂O₃and TiO) then form underneath the TiO₂layer and induce stress at the interface of oxide layers. The induced stress plays significant role on the growth of 1D TiO₂nanostructures. The induced stress is relaxed by creating new surfaces in the form of 1D TiO₂nanostructures. A diffusion based model is proposed to explain the mechanism of 1D TiO₂growth during humid oxidation of Ti. The 1D TiO₂nanostructures and TiO₂layer is formed by the interstitial diffusion of Ti⁴⁺ions to the surface and reacts with the surface adsorbed hydroxide ions (OH^-). Lower valence oxides are formed at the metal-oxide interface by the reaction between diffused oxygen ions and Ti ions.

Multifunctional natural polymer-based metallic implant surface modifications

High energy traumas could cause critical damage to bone, which will require permanent implants to recover while functionally integrating with the host bone. Critical sized bone defects necessitate the use of bioactive metallic implants. Because of bioinertness, various methods involving surface modifications such as surface treatments, the development of novel alloys, bioceramic/bioglass coatings, and biofunctional molecule grafting have been utilized to effectively integrate metallic implants with a living bone. However, the applications of these methods demonstrated a need for an interphase layer improving bone-making to overcome two major risk factors: aseptic loosening and peri-implantitis. To accomplish a biologically functional bridge with the host to prevent loosening, regenerative cues, osteoimmunomodulatory modifications, and electrochemically resistant layers against corrosion appeared as imperative reinforcements. In addition, interphases carrying antibacterial cargo were proven to be successful against peri-implantitis. In the literature, metallic implant coatings employing natural polymers as the main matrix were presented as bioactive interphases, enabling rapid, robust, and functional osseointegration with the host bone. However, a comprehensive review of natural polymer coatings, bridging and grafting on metallic implants, and their activities has not been reported. In this review, state-of-the-art studies on multifunctional natural polymer-based implant coatings effectively utilized as a bone tissue engineering (BTE) modality are depicted. Protein-based, polysaccharide-based coatings and their combinations to achieve better osseointegration via the formation of an extracellular matrix-like (ECM-like) interphase with gap filling and corrosion resistance abilities are discussed in detail. The hypotheses and results of these studies are examined and criticized, and the potential future prospects of multifunctional coatings are also proposed as final remarks.

Pore size modulates in vitro osteogenesis of bone marrow mesenchymal stem cells in fibronectin/gelatin coated silk fibroin scaffolds

Porous scaffolds have been widely used for bone tissue engineering (BTE), and the pore structure of scaffolds plays an important role in osteogenesis. Silk fibroin (SF) is a favorable biomaterial for BTE due to its excellent mechanical property, biocompatibility, and biodegradation, but the lack of cell attachment sites in SF chemical structure resulted in poor cell-material interactions. In this study, SF scaffolds were coated with fibronectin/gelatin (Fn/G) to improve cell adhesion. Furthermore, the effect of pore size in Fn/G coated SF scaffolds on osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were investigated in vitro. Scaffolds with average pore diameters of 384.52, 275.23, and 173.8 μm were prepared by salt leaching method, labelled as Large, Medium, and Small group. Porcine BMSCs were seeded on scaffolds and cultured in osteogenic medium for 21 days to evaluate cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, gene expression of osteogenic markers, and histological performance. The results showed Fn/G coating effectively improved cell adhesion on SF scaffolds. Cell metabolic rate in each group increased significantly with time, but there was no statistical difference at each time point among the three groups. On day 21, ALP/DNA and calcium/DNA in the Small group were significantly higher than those in the Large group. Among the three pore sizes, the Small group showed higher mRNA expression of COl I on day 7, OPN on day 14, and OCN on day 21. Immunohistochemical staining on day 21 showed that Col I and OCN in Small group were more highly expressed. In conclusion, the Fn/G coated SF scaffolds with a mean pore diameter of 173.8 μm was optimal for osteogenic differentiation of BMSC in vitro.

Surface Modifications of Titanium Aluminium Vanadium Improve Biocompatibility and Osteogenic Differentiation Potential

Osteogenic cells are strongly influenced in their behaviour by the surface properties of orthopaedic implant materials. Mesenchymal stem and progenitor cells (MSPCs) migrate to the bone–implant interface, adhere to the material surface, proliferate and subsequently differentiate into osteoblasts, which are responsible for the formation of the bone matrix. Five surface topographies on titanium aluminium vanadium (TiAl₆V₄) were engineered to investigate biocompatibility and adhesion potential of human osteoblasts and the changes in osteogenic differentiation of MSPCs. Elemental analysis of TiAl₆V₄ discs coated with titanium nitride (TiN), silver (Ag), roughened surface, and pure titanium (cpTi) surface was analysed using energy-dispersive X-ray spectroscopy and scanning electron microscopy. In vitro cell viability, cytotoxicity, adhesion behaviour, and osteogenic differentiation potential were measured via CellTiter-Glo, CytoTox, ELISA, Luminex^® technology, and RT-PCR respectively. The Ag coating reduced the growth of osteoblasts, whereas the viability of MSPCs increased significantly. The roughened and the cpTi surface improved the viability of all cell types. The additive coatings of the TiAl₆V₄ alloy improved the adhesion of osteoblasts and MSPCs. With regard to the osteogenic differentiation potential, an enhanced effect has been demonstrated, especially in the case of roughened and cpTi coatings.

Enhancing Osseointegration of TC4 Alloy by Surficial Activation Through Biomineralization Method

Titanium (Ti) alloys have been applied to biomedical implants for a long time. Although Ti alloys are biocompatible, efforts have been continuously made to improve their bone conductivity and osteogenesis for enhancing their performance. Silk fibroin (SF) is a natural biomaterial with excellent biomedical and mechanical properties, and hydroxyapatite (HAP) nanocomposites derived from SF are promising for producing “artificial bone” owing to their biomedical applicability and strong mechanical functions. Therefore, we built an SF coating on the surface of Ti–6Al–4V alloy, and then the incubated SF-coated Ti alloy were immersed in simulated body fluid to induce mineral deposition of HAP on the alloys. The results from Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) analysis, and Attenuated Total Reflection–Fourier Transform Infrared Spectroscopy (ATR–FTIR) confirmed the deposition of a mineral layer on the SF film surface. The proliferation, adhesion, and differentiation of MG-63 were tested, along with the BMP-2, COX-2, and OPG expression and protein content in the MG-63. Both Ti + SF and Ti + SF + HAP groups exhibited significantly better performance than a control Ti group with regard to the cell adhesion, cell proliferation, and protein expression. Furthermore, the hybrid layer comprising HAP and SF delivered more significant improvement of the osseointegration than the SF alone. It is hoped that the proposed methods can be used for constructing modified surfaces on Ti alloys, as they endowed the implants with good osteogenic potential.

Silk-Based Materials for Hard Tissue Engineering

Hard tissues, e.g., bone, are mechanically stiff and, most typically, mineralized. To design scaffolds for hard tissue regeneration, mechanical, physico-chemical and biological cues must align with those found in the natural tissue. Combining these aspects poses challenges for material and construct design. Silk-based materials are promising for bone tissue regeneration as they fulfill several of such necessary requirements, and they are non-toxic and biodegradable. They can be processed into a variety of morphologies such as hydrogels, particles and fibers and can be mineralized. Therefore, silk-based materials are versatile candidates for biomedical applications in the field of hard tissue engineering. This review summarizes silk-based approaches for mineralized tissue replacements, and how to find the balance between sufficient material stiffness upon mineralization and cell survival upon attachment as well as nutrient supply.

A multifunctional silk coating on additively manufactured porous titanium to prevent implant-associated infection and stimulate bone regeneration

Despite tremendous progress in the design and manufacturing of metallic implants, they do not outlive the patient. To illustrate, more than half of hip replacements will fail, mainly due to implant infection and loosening. Surface engineering approaches and, in particular, coatings can facilitate implant bio-functionality via the recruitment of more host cells for new bone formation and inhibition of bacterial colonization. Here, we used electrophoretic deposition to apply a silk fibroin solution consisting of tricalcium phosphate (TCP) and vancomycin as a coating on the surface of additively-manufactured porous titanium. Furthermore, the surface properties of the coatings developed and the release kinetics of the vancomycin were studied to evaluate the applied coating. The in vitro antibacterial behavior of the multifunctional coating, as well as the cell viability and osteogenic differentiation of the MC3T3-E1 cell line were extensively studied. The biomaterials developed exhibited an antibacterial behavior with a reduction of up to four orders of magnitude in both planktonic and adherent bacteria for 6 h and 1 d. A live-dead assay, the Alamar Blue activity, the DNA content, and cytoskeleton staining demonstrated a significant increase in the cell density of the coated groups versus the as-manufactured ones. The significantly enhanced calcium deposition and the increase in mineralization for the groups with TCP after 21 and 28 d, respectively, demonstrate upregulation of the MC3T3 cells' osteogenic differentiation. Our results collectively show that the multifunctional coating studied here can be potentially used to develop a new generation of orthopedic implants.

Nanointeraction: The profound influence of nanostructured and nano-drug delivery biomedical implant surfaces on cell behavior

Nanostructured surfaces feature promising biological properties on biomaterials attracting large interest at basic research, implant industry development, and bioengineering applications. Thou, nanoscale interactions at a molecular and cellular level are not yet completely understood and its biological and clinical implications need to be further elucidated. As follows, the aim of this comprehensive review was to evaluate nanostructured surfaces at biomedical implants focusing on surface development, nanostructuration, and nanoengineered drug delivery systems that can induce specific cell interactions in all relevant aspects of biological, reparative, anti-bacterial, anti-inflammatory and clinical processes. The methods and the physio-chemical properties involved in nanotopography performance, the main cellular characteristics involved at surface/cell interaction, and a summary of results and outlooks reported in studies applying nanostructured surfaces and nano-drug delivery systems is presented. The future prospects and commercial translation of this developing field, particularly concerning multifunctional nanostructured surfaces and its clinical implications are further discussed. At a cellular level, nanostructured biomedical implant surfaces can enhance osteogenesis by targeting osteoblasts, osteocytes, and mesenchymal cells, stimulate fibroblast/epithelial cells proliferation and adherence, inhibit bacterial cell proliferation and biofilm accumulation, and act as immune-modulating surfaces targeting macrophages and reducing pro-inflammatory cytokine expression. Moreover, several methodological options to create drug-delivery systems on metallic implant surfaces are available, however, the clinical translation is yet incomplete. The efficiency of which nanostructured/nano-delivery surfaces may target specific cell interactions and favor clinical outcomes needs to be further elucidated in pre-clinical and clinical studies, along with engineering solutions for commercial translation and approval of controlling agencies.

Silk Fibroin-Based Hybrid Nanostructured Coatings for Titanium Implantable Surfaces Modification

This study proposes the development of new architectures that combine nanostructured titanium surface and biodegradable polymers as a promising approach to achieve a better performance after bioactive agent incorporation. The silk fibroin protein that was extracted from silkworm Bombyx mori cocoons is important due to the remarkable characteristics, such as biocompatibility, good mechanical properties, adjustable degradation and drug stabilizing capabilities. The titanium substrate was firstly nanostructurated with TiO2 nanotubes and then coated with silk fibroin using electrospinning and electrochemical deposition. The deposited silk film ability to become a bioactive implant coating with antibacterial properties after the encapsulation of the active agents such as CeO2 was investigated. Important features of the new implant coating were analysed: surface properties, electrochemical stability in physiological simulated electrolytes, and antibacterial action against Escherichia coli. The obtained results indicate that silk fibroin bioactive layers are a potential candidate for regenerative medicine.