Surface modification strategies to improve titanium hemocompatibility: a comprehensive review

Targeting the Contact Pathway of Coagulation for the Prevention and Management of Medical Device-Associated Thrombosis

Hemorrhage remains a major complication of anticoagulants, with bleeding leading to serious and even life-threatening outcomes in rare settings. Currently available anticoagulants target either multiple coagulation factors or specifically coagulation factor (F) Xa or thrombin; however, inhibiting these pathways universally impairs hemostasis. Bleeding complications are especially salient in the medically complex population who benefit from medical devices. Extracorporeal devices-such as extracorporeal membrane oxygenation, hemodialysis, and cardiac bypass-require anticoagulation for optimal use. Nonetheless, bleeding complications are common, and with certain devices, highly morbid. Likewise, pharmacologic prophylaxis to prevent thrombosis is not commonly used with many medical devices like central venous catheters due to high rates of bleeding. The contact pathway members FXI, FXII, and prekallikrein serve as a nexus, connecting biomaterial surface-mediated thrombin generation and inflammation, and may represent safe, druggable targets to improve medical device hemocompatibility and thrombogenicity. Recent in vivo and clinical data suggest that selectively targeting the contact pathway of coagulation through the inhibition of FXI and FXII can reduce the incidence of medical device-associated thrombotic events, and potentially systemic inflammation, without impairing hemostasis. In the following review, we will outline the current in vivo and clinical data encompassing the mechanism of action of drugs targeting the contact pathway. This new class of inhibitors has the potential to herald a new era of effective and low-risk anticoagulation for the management of patients requiring the use of medical devices.

Nanocarbon-Polymer Composites for Next-Generation Breast Implant Materials

Most breast implants currently used in both reconstructive and cosmetic surgery have a silicone outer shell, which, despite much progress, remains susceptible to mechanical failure, infection, and foreign body response. This study shows that the durability and biocompatibility of breast implant-grade silicone can be enhanced by incorporating carbon nanomaterials of sp2 and sp3 hybridization into the polymer matrix and onto its surface. Plasma treatment of the implant surface can be used to modify platelet adhesion and activation to prevent thrombosis, postoperative infection, and inflammation disorders. The addition of 0.8% graphene flakes resulted in an increase in mechanical strength by 64% and rupture strength by around 77% when compared to pure silicone, whereas when nanodiamond (ND) was used as the additive, the mechanical strength was increased by 19.4% and rupture strength by 37.5%. Composites with a partially embedded surface layer of either graphene or ND showed superior antimicrobial activity and biocompatibility compared to pure silicone. All composite materials were able to sustain the attachment and growth of human dermal fibroblast, with the preferred growth noted on ND-coated surfaces when compared to graphene-coated surfaces. Exposure of these materials to hydrogen plasma for 5, 10, and 20 s led to substantially reduced platelet attachment on the surfaces. Hydrogen-treated pure silicone showed a decrease in platelet attachment for samples treated for 5-20 s, whereas silicone composite showed an almost threefold decrease in platelet attachment for the same plasma treatment times. The absence of platelet activation on the surface of composite materials suggests a significant improvement in hemocompatibility of the material.

"Synergistic anticoagulant and endothelial regeneration strategy" based on mussel-inspired phospholipid copolymer coating and bioactive zeolitic imidazolate frameworks-90 to maintain the patency of CoCr stent

Given the risks of poor patient compliance and bleeding associated with current dual antiplatelet therapies, it is urgent to develop the next generation of cardiovascular stents with anticoagulation and rapid endothelialization capabilities. Inspired by the prominent bioactivity and bioavailability of zeolitic imidazolate framework-90 (ZIF-90) in driving endothelial cell (EC) morphogenesis, this research proposes a "synergistic anticoagulant and endothelial regeneration strategy" depending on mussel-inspired phospholipid copolymer (MIPC) and ZIF-90. Depending on the copolymerization of the catechol with dopamine (Dopa) monomers, Dopa/MIPC coating was immobilized on the surface of CoCr via a one-pot process for resisting the initial thrombosis induced by platelets and fibrinogen. Meanwhile, ZIF-90 was loaded on the coating via coordination effect, aiming to accelerate the proliferation and migration of ECs. Compared with CoCr, the well-designed CoCr-Dopa/MIPC@ZIF-90 not only reduced fibrinogen adhesion by approximately 40 % and platelet adhesion by almost 55 %, but also promoted the proliferation and migration of ECs significantly in vitro. Furthermore, the blood flow velocity of CoCr-Dopa/MIPC@ZIF-90 stent was similar to natural aorta and ECs coverage on it was greatly strengthened after 30 days in a rat aorta vascular stent implantation model. Collectively, CoCr-Dopa/MIPC@ZIF-90 exhibited obvious superiority in reducing the formation of thrombus and promoting endothelial regeneration, which might meet the high requirement for the next generation of vascular stent.

Bio-Inspired Micro- and Nano-Scale Surface Features Produced by Femtosecond Laser-Texturing Enhance TiZr-Implant Osseointegration

Surface design plays a critical role in determining the integration of dental implants with bone tissue. Femtosecond laser-texturing has emerged as a breakthrough technology offering excellent uniformity and reproducibility in implant surface features. However, when compared to state-of-the-art sandblasted and acid-etched surfaces, laser-textured surface designs typically underperform in terms of osseointegration. This study investigates the capacity of a bio-inspired femtosecond laser-textured surface design to enhance osseointegration compared to state-of-the-art sandblasted & acid-etched surfaces. Laser-texturing facilitates the production of an organized trabeculae-like microarchitecture with superimposed nano-scale laser-induced periodic surface structures on both 2D and 3D samples of titanium-zirconium-alloy. Following a boiling treatment to modify the surface chemistry, improving wettability to a contact angle of 10°, laser-textured surfaces enhance fibrin network formation when in contact with human whole blood, comparable to state-of-the-art surfaces. In vitro experiments demonstrate that laser-textured surfaces significantly outperform state-of-the-art surfaces with a 2.5-fold higher level of mineralization by bone progenitor cells after 28 days of culture. Furthermore, in vivo evaluations reveal superior biomechanical integration of laser-textured surfaces after 28 days of implantation. Notably, during abiological pull-out tests, laser-textured surfaces exhibit comparable performance, suggesting that the observed enhanced osseointegration is primarily driven by the biological response to the surface.

Facile engineering of interactive double network hydrogels for heart valve regeneration

Regenerative heart valve prostheses are essential for treating valvular heart disease, which requested interactive materials that can adapt to the tissue remodeling process. Such materials typically involves intricate designs with multiple active components, limiting their translational potential. This study introduces a facile method to engineer interactive materials for heart valve regeneration using 1,1'-thiocarbonyldiimidazole (TCDI) chemistry. TCDI crosslinking forms cleavable thiourea and thiocarbamate linkages which could gradually release H2S during degradation, therefore regulates the immune microenvironment and accelerates tissue remodeling. By employing this approach, a double network hydrogel was formed on decellularized heart valves (DHVs), showcasing robust anti-calcification and anti-thrombosis properties post fatigue testing. Post-implantation, the DHVs could adaptively degrade during recellularization, releasing H2S to further support tissue regeneration. Therefore, the comprehensive endothelial cell coverage and notable extracellular matrix remodeling could be clearly observed. This accessible and integrated strategy effectively overcomes various limitations of bioprosthetic valves, showing promise as an attractive approach for immune modulation of biomaterials.

3D-printed surfaces of titanium implant: the fibroblasts response

Ti-6Al-4V (wt%) is the most widely used titanium alloy and its additive manufactured (or 3D printed) parts with near net-shape have provided great advantages for biomedical applications. While the impact of surface roughness on the biocompatibility of 3D-printed Ti-6Al-4V part is recognized, further exploration is needed to fully understand this complex relationship. Hence, this study presents a comprehensive evaluation of as-printed Ti-6Al-4V structures, both with and without surface texturing, with particular focus on the fibroblast response. Alongside a flat surface, or as-printed surface, two different types of surface textures: diamond texture and diamond crystal texture, were meticulously designed and printed through laser powder bed fusion (LPBF). The viability, cell adhesion, and morphology of human and murine fibroblasts seeded on the surface patterns was investigated, as well as the distribution of extracellular matrix (ECM) proteins (collagen I, fibronectin). The results demonstrated that the as-fabricated surface morphologies did not impact fibroblast viability, however, a reduced density of human fibroblasts was observed on the diamond texture surface, likely owing to the upright strut structure preventing cell adhesion. Interestingly, spreading of the human, but not murine, fibroblasts was limited by the remaining partially-sintered powders. The relative intensity of ECM protein signals was unaffected, however, ECM protein distribution across the surfaces was also altered. Thus, the as-printed substrates, particularly with diamond crystal struts, present a promising avenue for the cost-effective and efficient fabrication of Ti-6Al-4V components for medical applications in the future.

Characterizing thrombus adhesion strength on common cardiovascular device materials

Thrombus formation in blood-contacting medical devices is a major concern in the medical device industry, limiting the clinical efficacy of these devices. Further, a locally formed clot within the device has the potential to detach from the surface, posing a risk of embolization. Clot embolization from blood-contacting cardiovascular devices can result in serious complications like acute ischemic stroke and myocardial infarction. Therefore, clot embolization associated with device-induced thrombosis can be life-threatening and requires an enhanced fundamental understanding of embolization characteristics to come up with advanced intervention strategies. Therefore, this work aims to investigate the adhesive characteristics of blood clots on common biocompatible materials used in various cardiovascular devices. This study focuses on characterizing the adhesion strength of blood clots on materials such as polytetrafluoroethylene (PTFE), polyurethane (PU), polyether ether ketone (PEEK), nitinol, and titanium, frequently used in medical devices. In addition, the effect of incubation time on clot adhesion is explored. Results from this work demonstrated strongest clot adhesion to titanium with 3 h of incubation resulting in 1.06 ± 0.20 kPa detachment stresses. The clot adhesion strength on titanium was 51.5% higher than PEEK, 35.9% higher than PTFE, 63.1% higher than PU, and 35.4% higher than nitinol. Further, adhesion strength increases with incubation time for all materials. The percentage increase in detachment stress over incubation time (ranging from 30 min to 3 h) for polymers ranged from at least 108.75% (PEEK), 140.74% (PU), to 151.61% (PTFE). Whereas, for metallic surfaces, the percentage rise ranged from 70.21% (nitinol) to 89.28% (titanium). Confocal fluorescence imaging of clot remnants on the material surfaces revealed a well-bounded platelet-fibrin network at the residual region, representing a comparatively higher adhesive region than the non-residual zone of the surface.

Osteointegration of Ti Bone Implants: A Study on How Surface Parameters Control the Foreign Body Response

The integration of titanium (Ti)-based implants with bone is limited, resulting in implant failure. This lack of osteointegration is due to the foreign body response (FBR) that occurs after the implantation of biodevices. The process begins with protein adsorption, which is governed by implant surface properties, e.g., chemistry, charge, wettability, and/or topography. The distribution and composition of the protein layer in turn influence the recruitment, differentiation, and modulation of immune and bone cells. The subsequent events that occur at the bone-material interface will ultimately determine whether the implant is encapsulated or will integrate with bone. Despite the numerous studies evaluating the influence of surface properties in the various stages of the FBR, the factors that affect tissue-material interactions are often studied in isolation or in small correlations due to the technical challenges involved in assessing them in vitro or in vivo. Consequently, the influence of protein conformation on the Ti bone implant surface design remains an unresolved research question. The objective of this review is to comprehensively evaluate the existing literature on the effect of surface parameters of Ti and its alloys in the stages of FBR, with a particular focus on protein adsorption and osteoimmunomodulation. This evaluation aims to systematically describe these effects on bone formation.

Effects of collagen modification on the osteogenic performance of different surface-modified titanium samples in vitro

OBJECTIVES

The aim of this study was to evaluate the effects of collagen modification on the osteogenic performance of different surface-modified titanium, including alkaline etching, alkaline etching followed by silanization, and alkaline etching followed by dopamine modification. The proliferation, adhesion, and osteogenic differentiation abilities of MC3T3-E1 cells on the surfaces with collagen modification were analyzed and compared.

METHODS

Collagen was immobilized on the surfaces of pure titanium (Ti-C), alkaline-etched titanium (Ti-Na-C), alkaline-etched and silanized titanium (Ti-A-C), and alkaline-etched and dopamine-modified titanium (Ti-D-C), with pure titanium (Ti) as the control group. The surface morphology was observed by scanning electron microscopy (SEM), and the surface elemental composition was analyzed by X-ray photoelectron spectroscopy (XPS). Contact angle measurements were conducted to evaluate the hydrophilicity of the surfaces. MC3T3-E1 cells were cultured on the surfaces, and their proliferation, adhesion, and osteogenic differentiation abilities were assessed using CCK-8 assay, laser scanning confocal microscope, alkaline phosphatase (ALP) staining, Alizarin red staining and quantitative analysis, as well as real-time quantitative polymerase chain reaction (RT-qPCR) to evaluate the mRNA expression levels of osteogenic-related genes, including ALP, typeⅠcollagen (COL-1), osteocalcin (OCN), osteopontin (OPN).

RESULTS

SEM and XPS results confirmed the successful immobilization of collagen on the titanium surfaces, with the Ti-Na-C group exhibiting a higher amount of collagen modification. Contact angle measurements showed improved hydrophilicity of the surfaces after collagen modification. CCK-8 results indicated good compatibility of the materials with MC3T3-E1, with enhanced cell proliferation on the collagen-modified surfaces. Cell fluorescence staining revealed better cell spreading on the collagen-modified surfaces, and ALP and Alizarin red staining results suggested that the Ti-Na-C group exhibited the best osteogenic performance, with significantly higher absorbance values in the Alizarin red quantification analysis. RT-qPCR analysis showed that the Ti-Na-C group had the highest expression of the osteogenic-related gene OPN.

CONCLUSIONS

Among the different collagen modification approaches employed in this study, collagen modification on alkaline-etched titanium surfaces showed the most conducive effects on MC3T3-E1 cell adhesion, spreading, proliferation, and osteogenic differentiation. This approach can be considered as the optimal collagen modification strategy for enhancing osteogenesis on titanium surfaces.

Titania (TiO2) nanotube surfaces doped with zinc and strontium for improved cell compatibility

Titanium-based orthopedic implants are gaining popularity in recent years due to their excellent biocompatibility, superior corrosion resistance and lightweight properties. However, these implants often fail to perform effectively due to poor osseointegration. Nanosurface modification approaches may help to resolve this problem. In this work, TiO2 nanotube (NT) arrays were fabricated on commercially available pure titanium (Ti) surfaces by anodization and annealing. Then, zinc (Zn) and strontium (Sr), important for cell signaling, were doped on the NT surface by hydrothermal treatment. This very simple method of Zn and Sr doping takes less time and energy compared to other complicated techniques. Different surface characterization tools such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), static water contact angle, X-ray diffraction (XRD) and nanoindentation techniques were used to evaluate the modified surfaces. Then, adipose derived stem cells (ADSCs) were cultured with the surfaces to evaluate cell adhesion, proliferation, and growth on the surfaces. After that, the cells were differentiated towards osteogenic lineage to evaluate alkaline phosphatase (ALP) activity, osteocalcin expression, and calcium phosphate mineralization. Results indicate that NT surfaces doped with Zn and Sr had significantly enhanced ADSC adhesion, proliferation, growth, and osteogenic differentiation compared to an unmodified surface, thus confirming the enhanced performance of these surfaces.

Biophysical studies of modified PVC sheet based on sunflower oil for antistatic and blood bags applications

In this work, the surface of polyvinyl chloride PVC sheet was modified by blending it with sunflower seed oil SSO to obtain PVC sheet/SSO films of ratios 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 (v/v)% using the solution casting method. Various techniques were used to characterize the prepared films, besides the use of hemolysis assays and blood clot formation tests. FTIR spectra revealed that there was a good interaction between the PVC sheet and the oil. The dielectric measurement indicated that SSO addition enhanced the dielectric properties of the sheet. The study of dielectric relaxation times confirmed the interaction between SSO and the sheet. DC conductivity increased to 6 × 10-6 S/m, so it could be applied in antistatic applications. Also, SSO addition increased the value of the thermal stability. According to SEM micrographs, the film was roughened at a ratio of 60/40 and smoothed out at 50/50. This behavior was confirmed with roughness and contact angle measurement results, in which the film of ratio 60/40 had the highest value equal to (72.03°) and then decreased at 50/50 to (59.62°). These results were confirmed by XRD measurement as the crystallinity increased at the film ratio of 60/40 and decreased again at 50/50. Also, the ratio of 60/40 demonstrated a large decrease in thrombus weights along with a slight increase in hemolysis, which is within the acceptable range and has a high degree of biocompatibility, so this concentration is recommended to be used in blood bags applications.

Evaluation of bioactivity and antibacterial properties of Ti6Al4V-based green biocomposite implant encompassing TiO2 nanotube arrays and garlic extract

This study involved the incorporation of an antibacterial garlic extract into titanium oxide nanotubes (TNTs) formed via the anodization of Ti6Al4V implants. The garlic extract, obtained through low-temperature extraction aided by ultrasound waves, was loaded into the nanotubes. The presence of the nanotubes was confirmed through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were used to investigate the presence of bioactive compounds, particularly sulfur compounds responsible for garlic's antibacterial effects. The impact of loading two concentrations (0.1 and 0.2 g per milliliter) of garlic extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria was examined. Results indicated a decrease in the growth range of S. aureus from 109 to 106 (CFU/ml) and E. coli from 1011 to 109 (CFU/ml) upon treatment. Additionally, cell adhesion and viability tests conducted on MG63 cells revealed an 8% increase in cell viability with the 0.1 g per milliliter concentration and a 35% decrease with the 0.2 g per milliliter concentration of garlic extract after 72 h of incubation (They have been evaluated by Microculture tetrazolium (MTT) assay). GC-MS analysis identified the presence of diethyl phthalate compounds in the garlic extract, suggesting a potential correlation with cellular toxicity observed in the sample with the higher concentration (0.2 g per milliliter) of garlic extract. Overall, the TNTs loaded with 0.1 g per milliliter of garlic extract simultaneously demonstrated antibacterial activity, cell viability, adhesion, and growth enhancement.

An osteoinductive surface by adhesive bone morphogenetic protein-2 prepared using the bioorthogonal approach for tight binding of titanium with bone

Inorganic biomaterials are used in various orthopedic and dental implants. Nevertheless, they cause clinical issues such as loosening of implants and patient morbidity. Therefore, inspired by mussel adhesive proteins, we aimed to design an adhesive and dimer-forming highly active bone morphogenetic protein-2 (BMP-2) using bioorthogonal chemistry, in which recombinant DNA technology was combined with enzymatic modifications, to achieve long-term osseointegration with titanium. The prepared BMP-2 exhibited substantially higher binding activity than wild-type BMP-2, while the adhered BMP-2 was more active than soluble BMP-2. Therefore, the adhesive BMP-2 was immobilized onto titanium wires and screws and implanted into rat bones, and long-term osteogenesis was evaluated. Adhesive BMP-2 promoted the mechanical binding of titanium to bones, enabling efficient bone regeneration and effective stabilization of implants. Thus, such adhesive biosignaling proteins can be used in regenerative medicine.

Enhancing Titanium Disk Performance through In-Pack Cold Atmospheric Plasma Treatment

While titanium dental implants have already been clinically established, ongoing research is continuously being conducted to advance the fields of osseointegration and bacterial resistance, seeking further improvements in these areas. In this study, we introduce an innovative method for treating titanium surfaces within tightly sealed packaging. Specifically, titanium discs, enclosed in surgical-grade packaging, underwent treatment using cold atmospheric plasma (CAP). The surfaces were thoroughly characterized in terms of wettability, crystalline structure, and chemical composition. Hemocompatibility analyses were conducted using blood diluted in sodium citrate (1:9) exposed to titanium discs for 30 min inside a CO2 incubator at 37 °C. Subsequently, various blood parameters were evaluated, including prothrombin time (PT), activated partial thromboplastin time (APTT), and platelet adhesion. Microbiological analyses were also performed using Pseudomonas aeruginosa (ATCC 27853) for 4 h at 37 °C. The treatment with CAP Jet resulted in a reduction in contact angle without causing any changes in the crystalline structure. No statistically significant differences were observed in the blood parameters. The plasma-treated samples exhibited lower PT and APTT values compared to those of the control group. The surfaces treated with CAP Jet showed increased platelet activation, platelet density, and thrombus formation when compared with the untreated samples. Moreover, the treated surfaces demonstrated lower bacterial colony formation compared with other surfaces.

Influence of titanium nanoscale surface roughness on fibrinogen and albumin protein adsorption kinetics and platelet responses

Biomaterials with nanoscale topography have been increasingly investigated for medical device applications to improve tissue-material interactions. This study assessed the impact of nanoengineered titanium surface domain sizes on early biological responses that can significantly affect tissue interactions. Nanostructured titanium coatings with distinct nanoscale surface roughness were deposited on quartz crystal microbalance with dissipation (QCM-D) sensors by physical vapor deposition. Physico-chemical characterization was conducted to assess nanoscale surface roughness, nano-topographical morphology, wettability, and atomic composition. The results demonstrated increased projected surface area and hydrophilicity with increasing nanoscale surface roughness. The adsorption properties of albumin and fibrinogen, two major plasma proteins that readily encounter implanted surfaces, on the nanostructured surfaces were measured using QCM-D. Significant differences in the amounts and viscoelastic properties of adsorbed proteins were observed, dependent on the surface roughness, protein type, protein concentration, and protein binding affinity. The impact of protein adsorption on subsequent biological responses was also examined using qualitative and quantitative in vitro evaluation of human platelet adhesion, aggregation, and activation. Qualitative platelet morphology assessment indicated increased platelet activation/aggregation on titanium surfaces with increased roughness. These data suggest that nanoscale differences in titanium surface roughness influence biological responses that may affect implant integration.

Surface modification strategies for improved hemocompatibility of polymeric materials: a comprehensive review

Polymeric biomaterials are a widely used class of materials due to their versatile properties. However, as with all other types of materials used for biomaterials, polymers also have to interact with blood. When blood comes into contact with any foreign body, it initiates a cascade which leads to platelet activation and blood coagulation. The implant surface also has to encounter a thromboinflammatory response which makes the implant integrity vulnerable, this leads to blood coagulation on the implant and obstructs it from performing its function. Hence, the surface plays a pivotal role in the design and application of biomaterials. In particular, the surface properties of biomaterials are responsible for biocompatibility with biological systems and hemocompatibility. This review provides a report on recent advances in the field of surface modification approaches for improved hemocompatibility. We focus on the surface properties of polysaccharides, proteins, and synthetic polymers. The blood coagulation cascade has been discussed and blood - material surface interactions have also been explained. The interactions of blood proteins and cells with polymeric material surfaces have been discussed. Moreover, the benefits as well as drawbacks of blood coagulation on the implant surface for wound healing purposes have also been studied. Surface modifications implemented by other researchers to enhance as well as prevent blood coagulation have also been analyzed.

A nitric oxide-catalytically generating carboxymethyl chitosan/sodium alginate hydrogel coating mimicking endothelium function for improving the biocompatibility

Thanks to their outstanding mechanical properties and corrosion resistance in physiological environments, titanium and its alloys are broadly explored in the field of intravascular devices. However, the biocompatibility is insufficient, causing thrombus formation and even implantation failure. In this study, inspired by the functions of endothelial glycocalyx and the NO-releasing of endothelial cells (ECs), a biomimetic coating (TNTA-Se) with three-dimensional gel-like structures and NO-catalytically generating ability was constructed on the titanium surface. To this end, the titanium alloy was firstly anodized and then annealed to form nanotube structures imitating the three-dimensional villous of glycocalyx, followed by the preparation of the Cu2+-loaded polydopamine intermediate layer for the immobilization of carboxymethyl chitosan and sodium alginate to form the hydrogel structure. Finally, an organoselenium compound (selenocystamine) as an active catalyst was covalently immobilized on the surface to develop a bioactive coating mimicking endothelial function with NO-generating activity. The surface morphologies and chemical structures of the biomimetic coating were characterized by scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and the results indicated that the NO-catalytically generating hydrogel coating was successfully constructed. The results of water contact angle and protein adsorption suggested that the TNTA-Se coating exhibited excellent hydrophilicity, the promotion of bovine serum albumin (BSA) adsorption while the inhibition of fibrinogen (FIB) adsorption. Upon the addition of NO donor S-nitroso glutathione (GSNO) and reducing agent glutathione (GSH), the surface (TNTA-NO) displayed excellent blood compatibility and cytocompatibility to ECs. Compared with other surfaces, the TNTA-NO coating can not only further promote BSA adsorption and inhibit the adhesion and activation of platelets as well as hemolysis, but also significantly enhance ECs adhesion and proliferation and up-regulate VEGF and NO expression of ECs. The current study demonstrated that the NO-catalytically generating hydrogel coating on the titanium alloy can mimic the glycocalyx structure and endothelium function to catalyze a large number of NO donors in human blood to produce NO, and thus simultaneously enhance the surface hemocompatibility and endothelialization, representing a promising strategy for long-term cardiovascular implants of titanium-based devices.

Modification of titanium orthopedic implants with bioactive glass: a systematic review of in vivo and in vitro studies

Bioactive glasses (BGs) are ideal biomaterials in the field of bio-restoration due to their excellent biocompatibility. Titanium alloys are widely used as a bone graft substitute material because of their excellent corrosion resistance and mechanical properties; however, their biological inertness makes them prone to clinical failure. Surface modification of titanium alloys with bioactive glass can effectively combine the superior mechanical properties of the substrate with the biological properties of the coating material. In this review, the relevant articles published from 2013 to the present were searched in four databases, namely, Web of Science, PubMed, Embase, and Scopus, and after screening, 49 studies were included. We systematically reviewed the basic information and the study types of the included studies, which comprise in vitro experiments, animal tests, and clinical trials. In addition, we summarized the applied coating technologies, which include pulsed laser deposition (PLD), electrophoretic deposition, dip coating, and magnetron sputtering deposition. The superior biocompatibility of the materials in terms of cytotoxicity, cell activity, hemocompatibility, anti-inflammatory properties, bioactivity, and their good bioactivity in terms of osseointegration, osteogenesis, angiogenesis, and soft tissue adhesion are discussed. We also analyzed the advantages of the existing materials and the prospects for further research. Even though the current research status is not extensive enough, it is still believed that BG-coated Ti implants have great clinical application prospects.

Polysaccharide-Based Coatings as Drug Delivery Systems

Therapeutic polysaccharide-based coatings have recently emerged as versatile strategies to transform a conventional medical implant into a drug delivery system. However, the translation of these polysaccharide-based coatings into the clinic as drug delivery systems still requires a deeper understanding of their drug degradation/release profiles. This claim is supported by little or no data. In this review paper, a comprehensive description of the benefits and challenges generated by the polysaccharide-based coatings is provided. Moreover, the latest advances made towards the application of the most important representative coatings based on polysaccharide types for drug delivery are debated. Furthermore, suggestions/recommendations for future research to speed up the transition of polysaccharide-based drug delivery systems from the laboratory testing to clinical applications are given.

Fabrication of CO-releasing surface to enhance the blood compatibility and endothelialization of TiO2 nanotubes on titanium surface

Although the construction of nanotube arrays with the micro-nano structures on the titanium surfaces has demonstrated a great promise in the field of blood-contacting materials and devices, the limited surface hemocompatibility and delayed endothelial healing should be further improved. Carbon monoxide (CO) gas signaling molecule within the physiological concentrations has excellent anticoagulation and the ability to promote endothelial growth, exhibiting the great potential for the blood-contact biomaterials, especially the cardiovascular devices. In this study, the regular titanium dioxide nanotube arrays were firstly prepared in situ on the titanium surface by anodic oxidation, followed by the immobilization of the complex of sodium alginate/carboxymethyl chitosan (SA/CS) on the self-assembled modified nanotube surface, the CO-releasing molecule (CORM-401) was finally grafted onto the surface to create a CO-releasing bioactive surface to enhance the biocompatibility. The results of scanning electron microscopy (SEM), X-ray energy dispersion spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) revealed that the CO-releasing molecules were successfully immobilized on the surface. The modified nanotube arrays not only exhibited excellent hydrophilicity but also could slowly release CO gas molecules, and the amount of CO release increased when cysteine was added. Furthermore, the nanotube array can promote albumin adsorption while inhibit fibrinogen adsorption to some extent, demonstrating its selective albumin adsorption; although this effect was somewhat reduced by the introduction of CORM-401, it can be significantly enhanced by the catalytic release of CO. The results of hemocompatibility and endothelial cell growth behaviors showed that, as compared with the CORM-401 modified sample, although the SA/CS-modified sample had better biocompatibility, in the case of cysteine-catalyzed CO release, the released CO could not only reduce the platelet adhesion and activation as well as hemolysis rate, but also promote endothelial cell adhesion and proliferation as well as vascular endothelial growth factor (VEGF) and nitric oxide (NO) expression. As a result, the research of the present study demonstrated that the releasing CO from TiO₂ nanotubes can simultaneously enhance the surface hemocompatibility and endothelialization, which could open a new route to enhance the biocompatibility of the blood-contacting materials and devices, such as the artificial heart valve and cardiovascular stents.

Zinc (Zn) Doping by Hydrothermal and Alkaline Heat-Treatment Methods on Titania Nanotube Arrays for Enhanced Antibacterial Activity

Titanium (Ti) is a popular biomaterial for orthopedic implant applications due to its superior mechanical properties such as corrosion resistance and low modulus of elasticity. However, around 10% of these implants fail annually due to bacterial infection and poor osseointegration, resulting in severe pain and suffering for the patients. To improve their performance, nanoscale surface modification approaches and doping of trace elements on the surfaces can be utilized which may help in improving cell adhesion for better osseointegration while reducing bacterial infection. In this work, at first, titania (TiO₂) nanotube arrays (NT) were fabricated on commercially available pure Ti surfaces via anodization. Then zinc (Zn) doping was conducted following two distinct methods: hydrothermal and alkaline heat treatment. Scanning electron microscopic (SEM) images of the prepared surfaces revealed unique surface morphologies, while energy dispersive X-ray spectroscopy (EDS) revealed Zn distribution on the surfaces. Contact angle measurements indicated that NT surfaces were superhydrophilic. X-ray photoelectron spectroscopy (XPS) provided the relative amount of Zn on the surfaces and indicated that hydrothermally treated surfaces had more Zn compared to the alkaline heat-treated surfaces. X-ray crystallography (XRD) and nanoindentation techniques provided the crystal structure and mechanical properties of the surfaces. While testing with adipose-derived stem cells (ADSC), the surfaces showed no apparent cytotoxicity to the cells. Finally, bacteria adhesion and morphology were evaluated on the surfaces after 6 h and 24 h of incubation. From the results, it was confirmed that NT surfaces doped with Zn drastically reduced bacteria adhesion compared to the Ti control. Zn-doped NT surfaces thus offer a potential platform for orthopedic implant application.

Chitosan Hydrogel as Tissue Engineering Scaffolds for Vascular Regeneration Applications

Chitosan hydrogels have a wide range of applications in tissue engineering scaffolds, mainly due to the advantages of their chemical and physical properties. This review focuses on the application of chitosan hydrogels in tissue engineering scaffolds for vascular regeneration. We have mainly introduced these following aspects: advantages and progress of chitosan hydrogels in vascular regeneration hydrogels and the modification of chitosan hydrogels to improve the application in vascular regeneration. Finally, this paper discusses the prospects of chitosan hydrogels for vascular regeneration.

Improved Hemocompatibility on Superhemophobic Micro-Nano-Structured Titanium Surfaces

Blood-contacting titanium-based implants such as endovascular stents and heart valve casings are prone to blood clotting due to improper interactions at the surface level. In complement, the current clinical demand for cardiovascular implants is at a new apex. Hence, there is a crucial necessity to fabricate an implant with optimal mechanical properties and improved blood compatibility, while simultaneously interacting differentially with cells and other microbial agents. The present study intends to develop a superhydrophobic implant surface with the novel micro-nano topography, developed using a facile thermochemical process. The surface topography, apparent contact angle, and crystal structure are characterized on different surfaces. The hemo/blood compatibility on different surfaces is assessed by evaluating hemolysis, fibrinogen adsorption, cell adhesion and identification, thrombin generation, complement activation, and whole blood clotting kinetics. The results indicate that the super-hemo/hydrophobic micro-nano titanium surface improved hemocompatibility by significantly reducing fibrinogen adsorption, platelet adhesion, and leukocyte adhesion. Thus, the developed surface has high potential to be used as an implant. Further studies are directed towards analyzing the mechanisms causing the improved hemocompatibility of micro/nano surface features under dynamic in vitro and in vivo conditions.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Extracting Mural and Volumetric Growth Patterns of Platelet Aggregates on Engineered Surfaces by Use of an Entity Tracking Algorithm

Thrombosis is a major complication that can occur in both blood-contacting devices and regions and in regions of vascular damage. Microfluidic devices are popular templates to model various thrombogenic settings and to assess conditions that lead to bulk channel occlusion. However, area-averaged measurements miss the opportunity to extract real-time information on thrombus evolution and early dynamics of thrombus formation and propagation, which result in late-stage bulk channel occlusion. To clarify these dynamics, we have developed a standalone tracking algorithm that uses consecutive image connectivity and minimal centroid distance mappings to uniquely index all appearing thrombi in fluorescence time-lapse videos http://links.lww.com/ASAIO/A887 , and http://links.lww.com/ASAIO/A888 . This leads to measurements of all individual aggregates that can in turn be studied as ensembles. We applied tracking to fluorescence time-lapse videos http://links.lww.com/ASAIO/A887 , and http://links.lww.com/ASAIO/A888 of thrombosis across both collagen-functionalized substrate and across the surface of a roughened titanium alloy (Ti6Al4V) at a shear rate of 4000 s -1 . When comparing ensemble-averaged measurements to area-averaged metrics, we unveil immediate, steady thrombus growth at early phases on collagen surfaces and unstable thrombus attachment to roughened Ti6Al4V surfaces on Ti6Al4V surfaces. Additionally, we introduce tracked thrombus eccentricity and fluorescence intensity as additional volumetric measures of thrombus growth that relate back to the primary thrombosis mechanism at play. This work advocates for the complementation of surface macrostate metrics with characteristic thrombus microstate growth patterns to accurately predict critical thrombosis events.

Role of chitosan in titanium coatings. trends and new generations of coatings

Survival studies of dental implants currently reach high figures. However, considering that the recipients are middle-aged individuals with associated pathologies, research is focused on achieving bioactive surfaces that ensure osseointegration. Chitosan is a biocompatible, degradable polysaccharide with antimicrobial and anti-inflammatory properties, capable of inducing increased growth and fixation of osteoblasts around chitosan-coated titanium. Certain chemical modifications to its structure have been shown to enhance its antibacterial activity and osteoinductive properties and it is generally believed that chitosan-coated dental implants may have enhanced osseointegration capabilities and are likely to become a commercial option in the future. Our review provided an overview of the current concepts and theories of osseointegration and current titanium dental implant surfaces and coatings, with a special focus on the in vivo investigation of chitosan-coated implants and a current perspective on the future of titanium dental implant coatings.

Enhanced antibacterial properties on superhydrophobic micro-nano structured titanium surface

Micro/nano scale surface modifications of titanium based orthopedic and cardiovascular implants has shown to augment biocompatibility. However, bacterial infection remains a serious concern for implant failure, aggravated by increasing antibiotic resistance and over usage of antibiotics. Bacteria cell adhesion on implant surface leads to colonization and biofilm formation resulting in morbidity and mortality. Hence, there is a need to develop new implant surfaces with high antibacterial properties. Recent developments have shown that superhydrophobic surfaces prevent protein and bacteria cell adhesion. In this study, a thermochemical treatment was used modify the surface properties for high efficacy antibacterial activity on titanium surface. The modification led to a micro-nano surface topography and upon modification with polyethylene glycol (PEG) and silane the surfaces were superhydrophilic and superhydrophobic, respectively. The modified surfaces were characterized for morphology, wettability, chemistry, corrosion resistance and surface charge. The antibacterial capability was characterized with Staphylococcus aureus and Escherichia coli by evaluating the bacteria cell inhibition, adhesion kinetics, and biofilm formation. The results indicated that the superhydrophobic micro-nano structured titanium surface reduced bacteria cell adhesion significantly (>90%) and prevented biofilm formation compared to the unmodified titanium surface after 24 h of incubation.