Electrophoretic deposition of chitosan reinforced graphene oxide-hydroxyapatite on the anodized titanium to improve biological and electrochemical characteristics

Application of loaded graphene oxide biomaterials in the repair and treatment of bone defects

Addressing bone defects is a complex medical challenge that involves dealing with various skeletal conditions, including fractures, osteoporosis (OP), bone tumours, and bone infection defects. Despite the availability of multiple conventional treatments for these skeletal conditions, numerous limitations and unresolved issues persist. As a solution, advancements in biomedical materials have recently resulted in novel therapeutic concepts. As an emerging biomaterial for bone defect treatment, graphene oxide (GO) in particular has gained substantial attention from researchers due to its potential applications and prospects. In other words, GO scaffolds have demonstrated remarkable potential for bone defect treatment. Furthermore, GO-loaded biomaterials can promote osteoblast adhesion, proliferation, and differentiation while stimulating bone matrix deposition and formation. Given their favourable biocompatibility and osteoinductive capabilities, these materials offer a novel therapeutic avenue for bone tissue regeneration and repair. This comprehensive review systematically outlines GO scaffolds' diverse roles and potential applications in bone defect treatment.

Application of advanced surface modification techniques in titanium-based implants: latest strategies for enhanced antibacterial properties and osseointegration

Titanium-based implants, renowned for their excellent mechanical properties, corrosion resistance, and biocompatibility, have found widespread application as premier implant materials in the medical field. However, as bioinert materials, they often face challenges such as implant failure caused by bacterial infections and inadequate osseointegration post-implantation. Thus, to address these issues, researchers have developed various surface modification techniques to enhance the surface properties and bioactivity of titanium-based implants. This review aims to outline several key surface modification methods for titanium-based implants, including acid etching, sol-gel method, chemical vapor deposition, electrochemical techniques, layer-by-layer self-assembly, and chemical grafting. It briefly summarizes the advantages, limitations, and potential applications of these technologies, presenting readers with a comprehensive perspective on the latest advances and trends in the surface modification of titanium-based implants.

Engineering Wet-Resistant and Osteogenic Nanocomposite Adhesive to Control Bleeding and Infection after Median Sternotomy

Median sternotomy surgery stands as one of the prevailing strategies in cardiac surgery. In this study, the cutting-edge bone adhesive is designed, inspired by the impressive adhesive properties found in mussels and sandcastle worms. This work has created an osteogenic nanocomposite coacervate adhesive by integrating a cellulose-polyphosphodopamide interpenetrating network, quaternized chitosan, and zinc, gallium-doped hydroxyapatite nanoparticles. This adhesive is characterized by robust catechol-metal coordination which effectively adheres to both hard and soft tissues with a maximum adhesive strength of 900 ± 38 kPa on the sheep sternum bone, surpassing that of commercial bone adhesives. The release of zinc and gallium cations from nanocomposite adhesives and quaternized chitosan matrix imparts remarkable antibacterial properties and promotes rapid blood coagulation, in vitro and ex vivo. It is also proved that this nanocomposite adhesive exhibits significant in vitro bioactivity, stable degradability, biocompatibility, and osteogenic ability. Furthermore, the capacity of nanocomposite coacervate to adhere to bone tissue and support osteogenesis contributes to the successful healing of a sternum bone defect in a rabbit model in vivo. In summary, these nanocomposite coacervate adhesives with promising characteristics are expected to provide solutions to clinical issues faced during median sternotomy surgery.

The effect of silver nanoparticles on biological and corrosion behavior of electrophoretically deposited hydroxyapatite film on Ti6Al4V

Surface modification of titanium and its alloys has been seriously considered by researchers to improve their biological behaviors, in the past few decades. In present research, hydroxyapatite (HA) based composite coatings with different concentrations of 0, 2, 4, and 6 wt% of silver (Ag) nanoparticles were electrophoretically deposited (EPD) on anodized and non-anodized Ti6Al4V, using a direct current at a voltage of 30 V for 10 min at room temperature. The specimens were then characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The cell adhesion images and cell viability results showed that HA-Ag composite coatings significantly promoted the biocompatibility of samples compared with the non-anodized and anodized Ti6Al4V. The viabilities of Mg-63 cells on HA-4%Ag coating and bi-layer coating (HA-4%Ag on anodized specimen) were approximately 91% and they were considered as the best coatings in term of biocompatibility. On the other hand, the antibacterial assessments demonstrated that HA-6%Ag coating had the best antibacterial performance compared with other samples. Furthermore, Tafel polarization curves indicated that corrosion resistance of the bi-layer coating was higher than those of the other specimens. The polarization resistance of this coating was about 7 times more than that of theTi6Al4V alloy.

Nanostructured Coatings Based on Graphene Oxide for the Management of Periprosthetic Infections

To modulate the bioactivity and boost the therapeutic outcome of implantable metallic devices, biodegradable coatings based on polylactide (PLA) and graphene oxide nanosheets (nGOs) loaded with Zinforo™ (Zin) have been proposed in this study as innovative alternatives for the local management of biofilm-associated periprosthetic infections. Using a modified Hummers protocol, high-purity and ultra-thin nGOs have been obtained, as evidenced by X-ray diffraction (XRD) and transmission electron microscopy (TEM) investigations. The matrix-assisted pulsed laser evaporation (MAPLE) technique has been successfully employed to obtain the PLA-nGO-Zin coatings. The stoichiometric and uniform transfer was revealed by infrared microscopy (IRM) and scanning electron microscopy (SEM) studies. In vitro evaluation, performed on fresh blood samples, has shown the excellent hemocompatibility of PLA-nGO-Zin-coated samples (with a hemolytic index of 1.15%), together with their anti-inflammatory ability. Moreover, the PLA-nGO-Zin coatings significantly inhibited the development of mature bacterial biofilms, inducing important anti-biofilm efficiency in the as-coated samples. The herein-reported results evidence the promising potential of PLA-nGO-Zin coatings to be used for the biocompatible and antimicrobial surface modification of metallic implants.

Electrophoretically deposited titanium and its alloys in biomedical engineering: Recent progress and remaining challenges

Over the past decade, titanium implants have gained popularity as the number of performed implantation operations has significantly increased. There are a number of methods for modifying the surface of biomaterials, which are aimed at extending the life of titanium implants. The developments in this field in recent years have required a comprehensive discussion of all the properties of electrophoretically deposited coatings on titanium and its alloys, taking into account their bioactivity. The development that took place in this field in recent years required a comprehensive discussion of all the properties of coatings electrophoretically deposited on titanium and its alloys, with particular emphasis on their bioactivity. Herein, we attempt to assess the influence of the electrophoretic deposition (EPD) process parameters on these coatings' biological and mechanical properties. Particular attention has been addressed to the in-vitro and in-vivo studies conducted hitherto. We have seen an increased interest in using titanium alloys without the addition of toxic compounds and gaps in the EPD field such as the uncommon endeavors to develop a "Design of experiments" approach as well as the lack of assessment of the surface free energy and detailed topography of electrophoretically deposited coatings. The exact correlation of coating properties with EPD process parameters still seems explicitly not understood, necessitating more future investigations. Ipso facto, the exact mechanism of particle agglomeration and Hamaker's law need to be fathomable.

Morphology-Dependent Immunomodulatory Coating of Hydroxyapatite/PEO for Magnesium-Based Bone Implants

One of the most critical issues concerning orthopedic implants is the risk of chronic inflammation, which poses a threat to the bone healing process. Osteo-immunomodulation plays a pivotal role in implant technology by influencing proinflammatory and anti-inflammatory responses, ultimately promoting bone healing. This study aims to investigate the morphology-dependent osteo-immunomodulatory properties of a hydroxyapatite (HA)/plasma electrolytic oxidation (PEO)-coated WE43 alloy. In this context, following the PEO process with various operational parameters (duty cycles of 50-40, 50-20, 70-40%, and frequencies of 0.5, 0.8, and 1 kHz), a layer of HA was applied as the top coating using a straightforward hot-dip process. The results revealed the formation of the PEO layer with distinct morphologies and pore sizes, depending on the operational parameters. Specifically, a uniform PEO coating with small pore sizes (5.2-5.3 μm) led to the creation of plate-like HA particles, while a random-like HA structure formed on nonuniform surfaces with large pores (7.0-11.1 μm) of PEO. Moreover, it was observed that the plate-like HA coating exhibited higher adhesion strength than the random one (classified as class 2 vs class 3 based on cross-cut standards). Furthermore, electrochemical impedance spectroscopy (EIS) and polarization studies confirmed a substantial increase in the polarization resistance (680 kΩ) and total impedance (48 559.6 Ω) for the plate-like HA/PEO as compared to the substrate (an increase of 1511-fold and 311-fold, respectively) and the random HA/PEO samples (an increase of 85-fold and 18-fold, respectively). In addition, compared to random HA coatings, there was a significant enhancement in the viability (150% control vs 96% control), proliferation, and differentiation of MG63 cells when exposed to plate-like HA coatings. Moreover, surface morphology and chemistry pronouncedly impacted macrophages' viability, morphology, and phenotype. Notably, plate-like HA coatings resulted in a higher upregulation of BMP-2 and TGF-β than proinflammatory cytokines (IL-6 and M-CSF), indicating a polarization of macrophage type 1 (M1) toward type 2 (M2). In summary, the bilayer HA/PEO coating exhibited remarkable osteo-immunomodulatory activity, making it highly appealing for use in bone implant applications.

Investigation of physical, mechanical and biological properties of polyhydroxybutyrate-chitosan/graphene oxide nanocomposite scaffolds for bone tissue engineering applications

Mechanical properties appropriate to native tissues, as an essential component in bone tissue engineering scaffolds, plays a significant role in tissue formation. In the current study, Poly-3 hydroxybutyrate-chitosan (PC) scaffolds reinforced with graphene oxide (GO) were made by the electrospinning method. The addition of GO led to a decrease in fibers diameter, an increase in thermal capacity and an improvement in the surface hydrophilicity of nanocomposite scaffolds. A significant increase in the mechanical properties of PC/GO (PCG) nanocomposite scaffolds was achieved due to the inherent strength of GO as well as its uniform dispersion throughout the polymeric matrix owing to hydrogen bonding and polar interactions. Also, lower biological degradation of the scaffolds (~30% in 100 days) due to the presence of GO provides essential mechanical support for bone regeneration. In addition, the bioactivity results showed that GO reinforcement significantly increases the biomineralization on the surface of the scaffolds. Evaluating cell adhesion and proliferation, as well as ALP activity of MG-63 cells on PC and PCG scaffolds indicated the positive effect of GO on scaffolds' biocompatibility. Overall, the improvement of physicochemical, mechanical, and biological properties of GO-reinforced scaffolds shows the potential of PCG nanocomposite scaffolds for bone tissue engineering.

Can Graphene Pave the Way to Successful Periodontal and Dental Prosthetic Treatments? A Narrative Review

Graphene, as a promising material, holds the potential to significantly enhance the field of dental practices. Incorporating graphene into dental materials imparts enhanced strength and durability, while graphene-based nanocomposites offer the prospect of innovative solutions such as antimicrobial dental implants or scaffolds. Ongoing research into graphene-based dental adhesives and composites also suggests their capacity to improve the quality and reliability of dental restorations. This narrative review aims to provide an up-to-date overview of the application of graphene derivatives in the dental domain, with a particular focus on their application in prosthodontics and periodontics. It is important to acknowledge that further research and development are imperative to fully explore the potential of graphene and ensure its safe use in dental practices.

Chitosan-Based Antibacterial Films for Biomedical and Food Applications

Antibacterial chitosan films, versatile and eco-friendly materials, have garnered significant attention in both the food industry and medicine due to their unique properties, including biodegradability, biocompatibility, and antimicrobial activity. This review delves into the various types of chitosan films and their distinct applications. The categories of films discussed span from pure chitosan films to those enhanced with additives such as metal nanoparticles, metal oxide nanoparticles, graphene, fullerene and its derivatives, and plant extracts. Each type of film is examined in terms of its synthesis methods and unique properties, establishing a clear understanding of its potential utility. In the food industry, these films have shown promise in extending shelf life and maintaining food quality. In the medical field, they have been utilized for wound dressings, drug delivery systems, and as antibacterial coatings for medical devices. The review further suggests that the incorporation of different additives can significantly enhance the antibacterial properties of chitosan films. While the potential of antibacterial chitosan films is vast, the review underscores the need for future research focused on optimizing synthesis methods, understanding structure-property relationships, and rigorous evaluation of safety, biocompatibility, and long-term stability in real-world applications.

Review on Biomedical Advances of Hybrid Nanocomposite Biopolymeric Materials

Hybrid materials are classified as one of the most highly important topics that have been of great interest to many researchers in recent decades. There are many species that can fall under this category, one of the most important of which contain biopolymeric materials as a matrix and are additionally reinforced by different types of carbon sources. Such materials are characterized by many diverse properties in a variety industrial and applied fields but especially in the field of biomedical applications. The biopolymeric materials that fall under this label are divided into natural biopolymers, which include chitosan, cellulose, and gelatin, and industrial or synthetic polymers, which include polycaprolactone, polyurethane, and conducting polymers of variable chemical structures. Furthermore, there are many types of carbon nanomaterials that are used as enhancers in the chemical synthesis of these materials as reinforcement agents, which include carbon nanotubes, graphene, and fullerene. This research investigates natural biopolymers, which can be composed of carbon materials, and the educational and medical applications that have been developed for them in recent years. These applications include tissue engineering, scaffold bones, and drug delivery systems.

Graphene/hydroxyapatite coating deposit on titanium alloys for implant application

Titanium (Ti) implants are widely used in medicine. Meanwhile, surface modification of Ti can strengthen the osseointegration of implants. In this study, we modified Ti implant surfaces, which was coated with GO, HA, HA-2wt%GO and HA-5wt%GO via electrophoresis deposition, to investigate their mechanisms and biological activity. Uncoated Ti was used as the control. Further, we examined the biological behavior and osteogenic performance of mouse bone marrow mesenchymal stem cells (BMSCs) cultured on coatings in vitro. We found that the HA-GO nanocomposite coating improved the roughness and hydrophilicity of the Ti surface. Compared with the uncoated Ti or Ti modified by HA or GO alone, cell adhesion and diffusion were enhanced on HA-GO-modified Ti surfaces. In addition, the proliferation and osteogenic differentiation of BMSCs in vitro were significantly improved on HA-GO-modified surfaces, whereas osteogenesis-related gene expression and alkaline phosphatase activity were slightly enhanced. Furthermore, we noted that bone regeneration was improved in the HA-2wt%GO group in vivo. Thus, the HA-2wt%GO nanocomposite coating might have potential applications in the field of dental implants.

The design, construction and application of graphene family composite nanocoating on dental metal surface

Enhancement of the biological and mechanical properties of dental metals is important for accommodation with therapeutic schemes in different stomatological disciplines. Nanocoatings based on graphene family nanomaterials (GFNs) improve the topological structure and physicochemical properties of metal surfaces, endowing them with new properties while maintaining inherent mechanical properties. Nano-composite coatings, composed of GFNs with one or more type of polymer, metal, oxide, and inorganic nonmetallic compound, offer more matching modification schemes to meet multifunctional oral treatment requirements (e.g., anti-bacterial and anti-corrosive activity, osteogenesis and angiogenesis). This review describes recent progress in the development of GFN composite nanocoatings for the modification of dental metals, focus on biological effects in clinical settings. Underlying molecular mechanisms, critical modification schemes, and technical innovation in preparation methods are also discussed. The key parameters of GFN composite nanocoating surface modification are summarized according to effects on cellular responses and antibacterial activity. This review provides a theoretical reference for the optimization of the biological effects and application of GFN composite nanocoatings for dental metals, and the promotion of the environmentally friendly large-scale production of high-quality multifunctional GFN-based nanocoatings in the field of oral science.

Effect of Olibanum Extract/Graphene Oxide on Differentiation of Bone Marrow Mesenchymal Stem Cells into Neuron-Like Cells on Freeze Dried Scaffolds

BACKGROUND

One of the challenges in using stem cells to neural repair is to induce their differentiation into neurons and lack of glial formation.

OBJECTIVES

Mesenchymal stem cells have revealed great potential for neural reorganization and renewal by taking advantage of differentiation capabilities. Here we explored the potential use of olibanum extract in freeze-dried scaffolds for induction of stem cells differentiation.

MATERIALS AND METHODS

In this study, gelatin/ collagen/olibanum/ graphene oxide (GEL/COL/OL/GO) freeze-dried scaffolds were synthesized and then adult rat bone marrow mesenchymal stem cells (BMMSCs) were seeded on scaffolds. The viability of cells was evaluated using MTT test on days 1, 3 and 5. The morphology of the cells seeded on scaffolds was studied using SEM and specific protein expression detected by immunohistochemical analysis. Real-time PCR was applied to detect the expression of Chat, Pax6, Hb-9, Nestin, Islet-1, and neurofilament-H (NF-H). The data were analyzed using Tukey test and one-way ANOVA and the means difference was considered significant at P<0.05, P<0.01, and P<0.001.

RESULTS

Showed that the pore size is increased in GEL/COL/OL/GO scaffolds compared with GO-free scaffolds and higher attachment and proliferation of BMMSCs on GEL/COL/OL /1.5% GO scaffolds compared to GEL/COL/OL/3% GO scaffolds. The cell viability results after 5 days of incubation showed the significant biocompatibility of GEL/COL/OL /1.5% GO freeze-dried scaffold. The results of immunohistochemical and PCR analysis revealed positive role of GEL/COL/OL/1.5% GO scaffolds in upregulation of neuron-specific markers.

CONCLUSION

These results reveal the great potential of GEL/COL/OL/GO scaffolds for nerve regeneration. Our data suggested that both OL extract and GO can regulate the MSCs differentiation into neurons.

Corrosion, mechanical and bioactivity properties of HA-CNT nanocomposite coating on anodized Ti6Al4V alloy

Hydroxyapatite-carbon nanotubes (HA-CNTs) nanocomposite coating was applied by electrophoretic method on anodized Ti alloy to investigate its stability in simulated body fluid (SBF). The biocoating was characterized by using scanning electron microscope (SEM) for microstructure, X-ray diffraction (XRD) for crystallography. The effect of CNTs concentration on the coating properties was also investigated and found out that CNTs up to 5% has various improving effect on the system. It increased corrosion resistance and adhesion of the coating to the substrate and decreased the number of cracks on the coating. The results of the in vitro test showed that the cell viability increased with increasing the concentration of CNTs to 3 wt.% CNTs. Graphical abstract.

Biomedical applications of chitosan-graphene oxide nanocomposites

Chitosan (CS) and graphene oxide (GO) nanocomposites have received wide attention in biomedical fields due to the synergistic effect between CS which has excellent biological characteristics and GO which owns great physicochemical, mechanical, and optical properties. Nanocomposites based on CS and GO can be fabricated into a variety of forms, such as nanoparticles, hydrogels, scaffolds, films, and nanofibers. Thanks to the ease of functionalization, the performance of these nanocomposites in different forms can be further improved by introducing other functional polymers, nanoparticles, or growth factors. With this background, the current review summarizes the latest developments of CS-GO nanocomposites in different forms and compositions in biomedical applications including drug and biomacromolecules delivery, wound healing, bone tissue engineering, and biosensors. Future improving directions and challenges for clinical practice are proposed as well.

Dual Synergistic Effects of MgO-GO Fillers on Degradation Behavior, Biocompatibility and Antibacterial Activities of Chitosan Coated Mg Alloy

The aim of this work was to establish and characterize chitosan/graphene oxide- magnesium oxide (CS/GO-MgO) nanocomposite coatings on biodegradable magnesium-zinc-cerium (Mg-Zn-Ce) alloy. In comparison to that of pure CS coatings, all composite coatings encapsulating GO-MgO had better adhesion strength to the Mg-Zn-Ce alloy substrate. The result depicted that the co-encapsulation of GO-MgO into the CS layer leads to diminish of contact angle value and hence escalates the hydrophilic characteristic of coated Mg alloy. The electrochemical test demonstrated that the CS/GO-MgO coatings significantly increased the corrosion resistance because of the synergistic effect of the GO and MgO inside the CS coating. The composite coating escalated cell viability and cell differentiation, according to cytocompatibility tests due to the presence of GO and MgO within the CS. The inclusion of GO-MgO in CS film, on the other hand, accelerates the formation of hydroxyapatite (HA) during 14 days immersion in SBF. Immersion results, including weight loss and hydrogen evolution tests, presented that CS/GO-MgO coating enables a considerably reduced degradation rate of Mg-Zn-Ce alloy when compared to the bare alloy. In terms of antibacterial-inhibition properties, the GO-MgO/CS coatings on Mg substrates showed antibacterial activity against Escherichia coli (E. coli), with a large inhibition area around the specimens, particularly for the coating containing a higher concentration of GO-MgO. Bacterial growth was not inhibited by the bare Mg alloy samples. The CS/GO-MgO composite coating is regarded as a great film to enhance the corrosion resistance, bioactivity, and antibacterial performance of Mg alloy implants.

GO-based antibacterial composites: Application and design strategies

Graphene oxide (GO), for its unique structure with high biocompatibility and designability, is widely used in the antibacterial field. Various strategies have been designed to fabricate GO-based composites with antibacterial properties. This review summarized these strategies, divided them into three types and interpreted their antibacterial mechanisms: (i) "GO*/non-GO" type in which GO acts as the single antibacterial core, (ii) "GO*/non-GO*" type in which GO and non-GO components function synergistically as dual antibacterial cores, (iii) "GO/non-GO*" type in which non-GO acts as the single antibacterial core, while GO component plays a supportive, not a dominant role in antibiosis. Besides, the fields suiting their applications and factors influencing their antibacterial properties were analyzed. Finally, the limitations and prospects in the current researches were discussed. In summary, GO-based composites have revolutionized antibacterial strategies. This review may serve as a reference to inspire further research on GO-based antibacterial composites.

A state-of-the-art review of the fabrication and characteristics of titanium and its alloys for biomedical applications

Abstract

Commercially pure titanium and titanium alloys have been among the most commonly used materials for biomedical applications since the 1950s. Due to the excellent mechanical tribological properties, corrosion resistance, biocompatibility, and antibacterial properties of titanium, it is getting much attention as a biomaterial for implants. Furthermore, titanium promotes osseointegration without any additional adhesives by physically bonding with the living bone at the implant site. These properties are crucial for producing high-strength metallic alloys for biomedical applications. Titanium alloys are manufactured into the three types of α, β, and α + β. The scientific and clinical understanding of titanium and its potential applications, especially in the biomedical field, are still in the early stages. This review aims to establish a credible platform for the current and future roles of titanium in biomedicine. We first explore the developmental history of titanium. Then, we review the recent advancement of the utility of titanium in diverse biomedical areas, its functional properties, mechanisms of biocompatibility, host tissue responses, and various relevant antimicrobial strategies. Future research will be directed toward advanced manufacturing technologies, such as powder-based additive manufacturing, electron beam melting and laser melting deposition, as well as analyzing the effects of alloying elements on the biocompatibility, corrosion resistance, and mechanical properties of titanium. Moreover, the role of titania nanotubes in regenerative medicine and nanomedicine applications, such as localized drug delivery system, immunomodulatory agents, antibacterial agents, and hemocompatibility, is investigated, and the paper concludes with the future outlook of titanium alloys as biomaterials.

Graphic abstract

Physicochemical and Biological Properties of Graphene-Oxide-Coated Metallic Materials

In this article, we present graphene oxide (produced by a modified Hummers' method) coatings obtained using two different methods: electrophoretic deposition on 316L stainless steel and chemical modification of the surface of gold applied to the steel. The coating properties were characterized by microscopic and spectrometric techniques. The contact angle was also determined, ranging from 50° to 70°. Our results indicated that GO coatings on steel and gold were not toxic towards L929 cells in a direct cell adhesion test-on all tested materials, it was possible to observe the growth of L929 cells during 48 h of culture. The lack of toxic effect on cells was also confirmed in two viability tests, XTT and MTT. For most of the tested materials, the cell viability was above 70%. They showed that the stability of the coating is the crucial factor for such GO coatings, and prove that GO in the form of coating is non-toxic; however, it can show toxicity if detached from the surface. The obtained materials also did not show any hemolytic properties, as the percentage of hemolysis was on the level of the negative control, which is very promising in the light of future potential applications.

Evolution of anodised titanium for implant applications

Anodised titanium has a long history as a coating structure for implants due to its bioactive and ossified surface, which promotes rapid bone integration. In response to the growing literature on anodised titanium, this article is the first to revisit the evolution of anodised titanium as an implant coating. The review reports the process and mechanisms for the engineering of distinctive anodised titanium structures, the significant factors influencing the mechanisms of its formation, bioactivity, as well as recent pre- and post-surface treatments proposed to improve the performance of anodised titanium. The review then broadens the discussion to include future functional trends of anodised titanium, ranging from the provision of higher surface energy interactions in the design of biocomposite coatings (template stencil interface for mechanical interlock) to techniques for measuring the bone-to-implant contact (BIC), each with their own challenges. Overall, this paper provides up-to-date information on the impacts of the structure and function of anodised titanium as an implant coating in vitro and in/ex vivo tests, as well as the four key future challenges that are important for its clinical translations, namely (i) techniques to enhance the mechanical stability and (ii) testing techniques to measure the mechanical stability of anodised titanium, (iii) real-time/in-situ detection methods for surface reactions, and (iv) cost-effectiveness for anodised titanium and its safety as a bone implant coating.

Analysis of the Calcium Phosphate-Based Hybrid Layer Formed on a Ti-6Al-7Nb Alloy to Enhance the Ossseointegration Process

This paper reports on hybrid, bioactive ceramic Ca-P-based coating formation on a Ti-6Al-7Nb alloy substrate to enhance the osseointegration process. The Ti alloy was anodized in a Ca₃(PO₄)₂ suspension and then the additional layer was formed by the sol-gel technique to obtain a mixture of the calcium phosphate compounds. The oxide layer was porous and additional ceramic particles were formed after sol-gel treatment (scanning electron microscopy analysis coupled with energy-dispersive x-ray spectroscopy). The ceramic particles were formed on some parts of the oxide layer and did not completely fill the pores. The layer thickness of the anodized Ti alloy was comprised between 3.01 and 5.03 µm and increased to 7.52–12.30 µm after the formation of an additional layer. Post-treatment of the anodized Ti alloys caused a decrease in surface roughness, and the layer became strongly hydrophilic. Crystalline phase analysis (X-ray diffraction, XRD) showed that the hybrid layer was composed of TiO₂ (anatase), Ca₃(PO₄)₂, Ca₁₀(PO₄)₆(OH)₂ and a partially amorphous phase; thus, the layer was also analyzed by Raman spectroscopy. The hybrid layer showed worse adhesion to the substrate than the anodized layer only; however, the coating was not brittle, and the first delamination of the layer was determined at 1.84 ± 0.11 N during scratch-test measurement. The hybrid coating was favorable for collagen type I and lactoferrin adsorption, strongly influencing the proliferation of osteoblast-like MG-63 cells. The coatings were cytocompatible and may find applications in formation of the functional layers on long-term implants’ surface after.

Fabrication and Characterization of Ag-Sr-Substituted Hydroxyapatite/Chitosan Coatings Deposited via Electrophoretic Deposition: A Design of Experiment Study

In this study, silver-strontium-doped hydroxyapatite (AgSr-HA)/chitosan composite coatings were deposited on a 316L stainless steel (SS) substrate via electrophoretic deposition (EPD). The Taguchi design of experiment (DoE) approach was used to optimize the EPD parameters such as the applied voltage, interelectrode spacing, and deposition time. Furthermore, the concentration of AgSr-HA particles in the suspension was also optimized via the DoE approach. DoE results demonstrated that the "homogeneous" coatings were obtained at the deposition time of 7 min, deposition voltage of 20 V, and at a concentration of 5 g/L AgSr-HA particles in the suspension. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), antibacterial studies, contact angle, and roughness measurements were performed to characterize the optimized coatings. SEM images confirmed the deposition of chitosan/AgSr-HA on the SS substrate. The wettability studies indicated the hydrophilic nature of the chitosan/AgSr-HA composite coatings, which confirmed that the developed coatings are suitable for biomedical applications, e.g., orthopedics. The average surface roughness of the chitosan/AgSr-HA composite coatings was in a suitable range used to attach the bone marrow stromal cells. Chitosan/AgSr-HA composite coatings showed an effective antibacterial effect against Gram-positive and Gram-negative bacteria. Moreover, the coatings developed apatite crystals on their surface upon immersion in simulated body fluid.

Influence of Two-Stage Anodization on Properties of the Oxide Coatings on the Ti–13Nb–13Zr Alloy

The increasing demand for titanium and its alloys used for implants results in the need for innovative surface treatments that may both increase corrosion resistance and biocompatibility and demonstrate antibacterial protection at no cytotoxicity. The purpose of this research was to characterize the effect of two-stage anodization—performed for 30 min in phosphoric acid—in the presence of hydrofluoric acid in the second stage. Scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, glow discharge optical emission spectroscopy, nanoindentation and nano-scratch tests, potentiodynamic corrosion studies, and water contact angle measurements were performed to characterize microstructure, mechanical, chemical and physical properties. The biologic examinations were carried out to determine the cytotoxicity and antibacterial effects of oxide coatings. The research results demonstrate that two-stage oxidation affects several features and, in particular, improves mechanical and chemical behavior. The processes influencing the formation and properties of the oxide coating are discussed.

The non-viral vectors and main methods of loading siRNA onto the titanium implants and their application

Surface modification of titanium implants by siRNA is quite efficient for improving implant osseointegration. Loading siRNA onto their surface is a crucial factor for siRNA-functionalized implants to realize their biological function. Direct binding of siRNA to implants has low siRNA binding and releasing rate, so usually it needs to be mediated by vectors. Polymeric, nonmaterial-mediated and lipid-based vectors are types of non-viral vectors which are commonly used for delivering siRNA. Three major methods of loading process, namely simple physical adsorption, layer-by-layer assembly and electrodeposition, are also summarized. A brief introduction, the basic principle and the general procedure of each method are included. The loading efficiency, which can be measured both qualitatively and quantitatively, together with gene knockdown efficiency, cytotoxicity assay and osteogenesis of the three methods are compared. A good many applications in osteogenesis have also been described in this review.

Three-Dimensional Printing Constructs Based on the Chitosan for Tissue Regeneration: State of the Art, Developing Directions and Prospect Trends

Chitosan (CS) has gained particular attention in biomedical applications due to its biocompatibility, antibacterial feature, and biodegradability. Hence, many studies have focused on the manufacturing of CS films, scaffolds, particulate, and inks via different production methods. Nowadays, with the possibility of the precise adjustment of porosity size and shape, fiber size, suitable interconnectivity of pores, and creation of patient-specific constructs, 3D printing has overcome the limitations of many traditional manufacturing methods. Therefore, the fabrication of 3D printed CS scaffolds can lead to promising advances in tissue engineering and regenerative medicine. A review of additive manufacturing types, CS-based printed constructs, their usages as biomaterials, advantages, and drawbacks can open doors to optimize CS-based constructions for biomedical applications. The latest technological issues and upcoming capabilities of 3D printing with CS-based biopolymers for different applications are also discussed. This review article will act as a roadmap aiming to investigate chitosan as a new feedstock concerning various 3D printing approaches which may be employed in biomedical fields. In fact, the combination of 3D printing and CS-based biopolymers is extremely appealing particularly with regard to certain clinical purposes. Complications of 3D printing coupled with the challenges associated with materials should be recognized to help make this method feasible for wider clinical requirements. This strategy is currently gaining substantial attention in terms of several industrial biomedical products. In this review, the key 3D printing approaches along with revealing historical background are initially presented, and ultimately, the applications of different 3D printing techniques for fabricating chitosan constructs will be discussed. The recognition of essential complications and technical problems related to numerous 3D printing techniques and CS-based biopolymer choices according to clinical requirements is crucial. A comprehensive investigation will be required to encounter those challenges and to completely understand the possibilities of 3D printing in the foreseeable future.

Surface Characterization of Electro-Assisted Titanium Implants: A Multi-Technique Approach

The understanding of chemical-physical, morphological, and mechanical properties of polymer coatings is a crucial preliminary step for further biological evaluation of the processes occurring on the coatings' surface. Several studies have demonstrated how surface properties play a key role in the interactions between biomolecules (e.g., proteins, cells, extracellular matrix, and biological fluids) and titanium, such as chemical composition (investigated by means of XPS, TOF-SIMS, and ATR-FTIR), morphology (SEM-EDX), roughness (AFM), thickness (Ellipsometry), wettability (CA), solution-surface interactions (QCM-D), and mechanical features (hardness, elastic modulus, adhesion, and fatigue strength). In this review, we report an overview of the main analytical and mechanical methods commonly used to characterize polymer-based coatings deposited on titanium implants by electro-assisted techniques. A description of the relevance and shortcomings of each technique is described, in order to provide suitable information for the design and characterization of advanced coatings or for the optimization of the existing ones.

Molecularly imprinted electrochemical sensor based on polypyrrole/dopamine@graphene incorporated with surface molecularly imprinted polymers thin film for recognition of olaquindox

In this paper, an advanced molecularly imprinted electrochemical sensor (MIECS) based on electropolymerized olaquindox (OLA) surface molecularly imprinted polymer thin film on a modified glassy carbon electrode (GCE) was developed for the detection of OLA. It was fabricated by coating dopamine@graphene (DGr) on GCE, then electropolymerizing pyrrole (Py) and molecularly imprinted polymers (MIPs). Graphene (Gr) was introduced for improving conductivity and sensitivity. Dopamine (DA) was used for dispersion and adhesion of Gr. Polypyrrole (PPy) could fix DGr and enhance the current response evidently. The established sensor could selectively recognize OLA but not the analogs of OLA. Some essential parameters controlling the performance of the developed sensor were investigated and optimized. Under optimal conditions, the linear relationship between the current intensity and OLA concentration was obtained from 50 nmol L^-1 to 500 nmol L^-1 with a limit of detection (LOD) of 7.5 nmol L^-1. Analytical results of OLA based on the developed MIECS for fish and feedstuffs showed a good agreement with the results based on high performance liquid chromatography (HPLC).

Electrophoretic deposition of Bioactive glass - Chitosan nanocomposite coatings on Ti-6Al-4V for orthopedic applications

Chitosan-Bioactive glass (CS-BG) nanocomposite coatings were developed on the Ti-6Al-4 V alloy to investigate the effect of the BG content on the adhesion strength, bioactivity, bio-corrosion, wettability and roughness. For this purpose, BG nanoparticles were synthesized using a sol-gel process. Three nanocomposite coatings with different concentrations of BG (0.5, 1 and 1.5 g/L) were fabricated through cathodic electrophoretic deposition (EPD). The surface morphology and composition of the coatings revealed the formation of compact coatings with a uniform distribution of BG nanoparticles. Increasing the BG content enhanced the deposition rate of CS-BG nanocomposite coatings and raised the coating thickness. Moreover, the CS-BG coating containing 1.5 g/L BG showed the best corrosion performance owing to the more uniform distribution of BG nanoparticles and its higher thickness. Also, increasing the BG concentration improved the adhesion strength, raised the roughness, and promoted wettability. Further, in-vitro bioactivity evaluation of the coated and uncoated specimens in SBF revealed that the formation of bone-like apatite was significantly encouraged on the surface of CS-BG coatings, as compared to the Ti-6Al-4 V uncoated sample. So, the apatite-forming ability of the coatings was improved by increasing the BG content. For in vitro investigation, osteoblast-like cell line MG63 were cultured on Ti-6Al-4 V substrate coated with CS-BG and cellular behavior was evaluated. Results demonstrated good cell attachment with no significant levels of cytotoxicity during 5 days of culture. Therefore, the electrophoretic deposition of the CS-1.5 g/L BG coating could successfully enhance the adhesion strength, bioactivity, corrosion and cellular performance of the substrate.