Evaluation of the effect of three surface treatments on the biocompatibility of 316L stainless steel using human differentiated cells

Microstructure, wear, and corrosion properties of PEEK-based composite coating incorporating titania- and copper-doped mesoporous bioactive glass nanoparticles

Poor wear- and corrosion-resistance of 316L SS implants are critical problems in orthopedic implants. This study aims to improve the wear- and corrosion-resistance of 316L SS through surface coating. In this study, a bilayer composite coating consisting of polyether ether ketone (PEEK) as the first layer, and titania (TiO2)- and Cu-doped mesoporous bioactive glass nanoparticles (Cu-MBGNs) were deposited as the second layer on a 316L SS via electrophoretic deposition (EPD). Scanning electron microscopy (SEM) images of the bilayer composite coating showed the distribution of TiO2 and Cu-MBGNs within the PEEK matrix. Energy dispersive spectroscopy (EDS) analysis confirmed the presence of TiO2 and Cu-MBGNs in the bilayer composite coating. Fourier transform infrared spectroscopy (FTIR) identified the functional groups attributed to the PEEK, TiO2 and Cu-MBGNs. X-ray diffraction (XRD) analysis confirmed the presence of TiO2 (anatase) and Cu-MBGNs in the bilayer composite coating. The coating exhibited a strong antibacterial effect against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Incorporating TiO2/Cu-MBGNs into the bilayer composite coating significantly modified the surface of 316L SS by improving the wear- and corrosion-resistance. Pin on disc test revealed that the specific wear rate of ∼(0.4570 ± 0.009) × 10-6 mm3 Nm-1 of the PEEK coating decreased to (0.0482 ± 0.007) × 10-6 mm3 Nm-1 on incorporating TiO2/Cu-MBGNs in PEEK coating under a normal load of 10 N in Dulbecco's Modified Eagle Medium (DMEM). Furthermore, electrochemical impedance spectroscopy (EIS) results revealed that the impedance value of the bilayer composite coating remained ∼4.56 × 105 Ω cm2 compared to 8.81 × 103 Ω cm2 of 316L SS after 24 h immersion in phosphate-buffered saline (PBS). Thus, this study demonstrated that the wear- and corrosion-resistance of 316L SS can be improved by incorporating TiO2/Cu-MBGNs in PEEK-based composite coatings for orthopedic applications.

Large-Scale Plasma-Polymerized Hexamethyldisiloxane Thin Films: Role of Interelectrode Distance and Excellent Corrosion Resistance

In comparison to the more traditional anticorrosion thin film coatings, the plasma polymerization approach offered a more efficient, dry, and straightforward procedure that made it possible to create dense films of several hundred nanometers in thickness, which has potential applications in metallic implant materials. In this paper, large-scale plasma polymerized hexamethyldisiloxane (ppHMDSO) thin film coatings were deposited on stainless steel substrates at different electrode distances to improve their corrosion resistance. The physicochemical properties and corrosion resistance of the ppHMDSO thin films as prepared at different electrode distances were characterized and gauged utilizing various characterization means. The results indicate that decreasing electrode distance accelerates monomer fragmentation and increases the oxidation process. The deposition rate and roughness of the ppHMDSO films both decreased as the electrode distance increased, while the carbonaceous group and hydrophobicity of the films enhanced. The ppHMDSO film prepared at an electrode distance of 40 mm obtained excellent elastic recovery and wear resistance and had an improved corrosion resistance, resulting in a reduction of 75% of the original corrosion behavior against the corrosion in Hank's solution. The resulting large-scale ppHMDSO thin film coatings can be further employed in implants for tissue engineering and biomaterials.

Rapid joule heating improves vitrification based cryopreservation

Cryopreservation by vitrification has far-reaching implications. However, rewarming techniques that are rapid and scalable (both in throughput and biosystem size) for low concentrations of cryoprotective agent (CPA) for reduced toxicity are lacking, limiting the potential for translation. Here, we introduce a joule heating-based platform technology, whereby biosystems are rapidly rewarmed by contact with an electrical conductor that is fed a voltage pulse. We demonstrate successful cryopreservation of three model biosystems with thicknesses across three orders of magnitude, including adherent cells (~4 µm), Drosophila melanogaster embryos (~50 µm) and rat kidney slices (~1.2 mm) using low CPA concentrations (2-4 M). Using tunable voltage pulse widths from 10 µs to 100 ms, numerical simulation predicts that warming rates from 5 × 104 to 6 × 108 °C/min can be achieved. Altogether, our results present a general solution to the cryopreservation of a broad spectrum of cellular, organismal and tissue-based biosystems.

Production of scaffold-free cell-based meat using cell sheet technology

In the production of cell-based meat, it is desirable to reduce animal-derived materials as much as possible to meet the challenges of sustainability. Here, we demonstrate the “cell sheet-based meat”: scaffold-free cell-based meat using cell sheet technology and characterize its texture and nutrients. Bovine myoblast cell sheets were prepared using temperature-responsive culture dishes (TRCDs) and 10 stacked cell sheets to fabricate three-dimensional tissue of 1.3–2.7 mm thickness. Hardness was increased by incubation on the TRCD and was further increased by boiling as is characteristic of natural meat. The wet weight percentage of total protein in the cell sheet was about half that of beef. In this method, large-sized items of cell sheet-based meat were also created by simply scaling up the TRCD. This method promises an environment-friendly food product.

Diamond-like Carbon Coatings in the Biomedical Field: Properties, Applications and Future Development

Repairment and replacement of organs and tissues are part of the history of struggle against human diseases, in addition to the research and development (R&D) of drugs. Acquisition and processing of specific substances and physiological signals are very important to understand the effects of pathology and treatment. These depend on the available biomedical materials. The family of diamond-like carbon coatings (DLCs) has been extensively applied in many industrial fields. DLCs have also been demonstrated to be biocompatible, both in vivo and in vitro. In many cases, the performance of biomedical devices can be effectively enhanced by coating them with DLCs, such as vascular stents, prosthetic heart valves and surgical instruments. However, the feasibility of the application of DLC in biomedicine remains under discussion. This review introduces the current state of research and application of DLCs in biomedical devices, their potential application in biosensors and urgent problems to be solved. It will be useful to build a bridge between DLC R&D workers and biomedical workers in order to develop high-performance DLC films/coatings, promote their practical use and develop their potential applications in the biomedical field.

Main Applications and Recent Research Progresses of Additive Manufacturing in Dentistry

In recent ten years, with the fast development of digital and engineering manufacturing technology, additive manufacturing has already been more and more widely used in the field of dentistry, from the first personalized surgical guides to the latest personalized restoration crowns and root implants. In particular, the bioprinting of teeth and tissue is of great potential to realize organ regeneration and finally improve the life quality. In this review paper, we firstly presented the workflow of additive manufacturing technology. Then, we summarized the main applications and recent research progresses of additive manufacturing in dentistry. Lastly, we sketched out some challenges and future directions of additive manufacturing technology in dentistry.

Production, Mechanical Properties and Biomedical Characterization of ZrTi-Based Bulk Metallic Glasses in Comparison with 316L Stainless Steel and Ti6Al4V Alloy

Microstructure, mechanical properties, corrosion resistance, and biocompatibility were studied for rapidly cooled 3 mm rods of Zr₄₀Ti₁₅Cu₁₀Ni₁₀Be₂₅, Zr₅₀Ti₅Cu₁₀Ni₁₀Be₂₅, and Zr₄₀Ti₁₅Cu₁₀Ni₅Si₅Be₂₅ (at.%) alloys, as well as for the reference 316L stainless steel and Ti-based Ti6Al4V alloy. Microstructure investigations confirm that Zr-based bulk metallic samples exhibit a glassy structure with minor fractions of crystalline phases. The nanoindentation tests carried out for all investigated composite materials allowed us to determine the mechanical parameters of individual phases observed in the samples. The instrumental hardness and elastic to total deformation energy ratio for every single phase observed in the manufactured Zr-based materials are higher than for the reference materials (316L stainless steel and Ti6Al4V alloy). A scratch tester used to determine the wear behavior of manufactured samples and reference materials revealed the effect of microstructure on mechanical parameters such as residual depth, friction force, and coefficient of friction. Electrochemical investigations in simulated body fluid performed up to 120 h show better or comparable corrosion resistance of Zr-based bulk metallic glasses in comparison with 316L stainless steel and Ti6Al4V alloy. The fibroblasts viability studies confirm the good biocompatibility of the produced materials. All obtained results show that fabricated biocompatible Zr-based materials are promising candidates for biomedical implants that require enhanced mechanical properties.

In Vitro and In Vivo Characterization of PLLA-316L Stainless Steel Electromechanical Devices for Bone Tissue Engineering-A Preliminary Study

Bone injuries represent a major social and financial impairment, commonly requiring surgical intervention due to a limited healing capacity of the tissue, particularly regarding critical-sized defects and non-union fractures. Regenerative medicine with the application of bone implants has been developing in the past decades towards the manufacturing of appropriate devices. This work intended to evaluate medical 316L stainless steel (SS)-based devices covered by a polymer poly (L-lactic acid) (PLLA) coating for bone lesion mechanical and functional support. SS316L devices were subjected to a previously described silanization process, following a three-layer PLLA film coating. Devices were further characterized and evaluated towards their cytocompatibility and osteogenic potential using human dental pulp stem cells, and biocompatibility via subcutaneous implantation in a rat animal model. Results demonstrated PLLA-SS316L devices to present superior in vitro and in vivo outcomes and suggested the PLLA coating to provide osteo-inductive properties to the device. Overall, this work represents a preliminary study on PLLA-SS316L devices' potential towards bone tissue regenerative techniques, showing promising outcomes for bone lesion support.

Surface Modification of 316L SS Implants by Applying Bioglass/Gelatin/Polycaprolactone Composite Coatings for Biomedical Applications

In this study, various composites of bioglass/gelatin/polycaprolactone (BG/GE/PCL) were produced and coated on the surface of 316L stainless steel (SS) to improve its bioactivity. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were utilized to characterize the specimens. The results showed that bioglass particles were distributed uniformly in the coating. By increasing the wt.% of bioglass in the nanocomposite coatings, the surface roughness and adhesion strength increased. The corrosion behavior of GE/PCL (PCL-10 wt.% gelatin coated on 316L SS) and 3BG/GE/PCL (GE/PCL including 3 wt.% bioglass coated on 316L SS) samples were studied in PBS solution. The results demonstrated that 3BG/GE/PCL sample improved the corrosion resistance drastically compared to the GE/PCL specimen. In vitro bioactivity of samples was examined after soaking the specimens for 7, 14 and 28 days in simulated body fluid (SBF). The results showed a significant apatite formation on the surface of 3BG/GE/PCL samples. The cell viability evaluation was performed using 3- (4, 5-dimethylthiazol-2-yl)-2,5 diphenyltetrazoliumbromide (MTT) tests which confirmed the enhanced cell viability on the surface of 3BG/GE/PCL samples. The in vivo behavior of specimens illustrated no toxicity and inflammatory response and was in a good agreement with the results obtained from the in vitro test.

From Austenitic Stainless Steel to Expanded Austenite-S Phase: Formation, Characteristics and Properties of an Elusive Metastable Phase

Austenitic stainless steels are employed in many industrial fields, due to their excellent corrosion resistance, easy formability and weldability. However, their low hardness, poor tribological properties and the possibility of localized corrosion in specific environments may limit their use. Conventional thermochemical surface treatments, such as nitriding or carburizing, are able to enhance surface hardness, but at the expense of corrosion resistance, owing to the formation of chromium-containing precipitates. An effective alternative is the so called low temperature treatments, which are performed with nitrogen- and/or carbon-containing media at temperatures, at which chromium mobility is low and the formation of precipitates is hindered. As a consequence, interstitial atoms are retained in solid solution in austenite, and a metastable supersaturated phase forms, named expanded austenite or S phase. Since the first studies, dating 1980s, the S phase has demonstrated to have high hardness and good corrosion resistance, but also other interesting properties and an elusive structure. In this review the main studies on the formation and characteristics of S phase are summarized and the results of the more recent research are also discussed. Together with mechanical, fatigue, tribological and corrosion resistance properties of this phase, electric and magnetic properties, wettability and biocompatibility are overviewed.

An innovative occluder for cardiac defect: 3D printing and a biocompatibility research based on self-developed bioabsorbable material-LA-GA-TMC

This study adopted the latest self-developed bioabsorbable material lactide-glycolide-1,3-trimethylene carbonate (LA-GA-TMC) and applied the three-dimensional (3D) printing technique to manufacture the occluder for cardiac septal defects, so as to realize the individualized treatment of cardiac septal defects. At the same time, its biosafety was evaluated, with an aim to establish foundation for futural large-scale animal experiment and clinical trial. The traditional "one-pot synthesis" was modified, and the "two-step synthesis method" was utilized to synthesize the LA-GA-TMC terpolymer at the lactide: glycolide: trimethylene carbonate ratio of 6:1:1.7. Afterward, the synthesized terpolymer was used as the raw material to fabricate the occluder model via using 3D printing technique. Then, its biocompatibility was comprehensively evaluated through cytocompatibility, blood compatibility, and histocompatibility. The occluder made from LA-GA-TMC 3D printing had favorable ductility and recoverability; besides, it possessed the temperature-control feature, and the relative cell proliferation rates in extract liquids at various concentrations were all >70%, suggesting that it had favorable cytocompatibility. Moreover, hemolytic experiment revealed that its hemolytic rate was <5%, dynamic blood coagulation experiment demonstrated that the sample material moderately activated the blood coagulation, and the above findings suggested that it had good blood compatibility. In addition, implanting experiment in vivo revealed that its histocompatibility was superior to the traditional nitinol and the emerging poly-l-lactic acid. It is completely feasible to manufacture the cardiac septal defects occluder based on the novel absorbable material LA-GA-TMC, which has favorable biocompatibility, through 3D printing technique and it possesses broad prospects in large-scale animal experiment and clinical trial.

Surface Modification of Pure Magnesium Mesh for Guided Bone Regeneration: In Vivo Evaluation of Rat Calvarial Defect

Guided bone regeneration is a therapeutic method that uses a barrier membrane to provide space available for new bone formation at sites with insufficient bone volume. Magnesium with excellent biocompatibility and mechanical properties has been considered as a promising biodegradable material for guided bone regeneration; however, the rapid degradation rate in the physiological environment is a problem to be solved. In this study, surface modification of pure magnesium mesh was conducted by plasma electrolytic oxidation and hydrothermal treatment to form a densely protective layer on the Mg substrate. The protective layer mainly consisted of Mg(OH)₂ with the amorphous calcium phosphate. Then, weight loss measurement and Micro-CT imaging were performed after an immersion test in a simulated body fluid. The effect of surface modification of the magnesium mesh on the guided bone regeneration was evaluated through an in vivo test using the rat calvarial defect model. The biodegradation of the magnesium mesh was identified to be significantly retarded. Additionally, the surface modification of Mg also can improve the bone volume and bone density of calvarial defect in comparison with that of the pristine Mg mesh.

The Spatiotemporal Control of Osteoblast Cell Growth, Behavior, and Function Dictated by Nanostructured Stainless Steel Artificial Microenvironments

The successful application of a nanostructured biomaterial as an implant is strongly determined by the nanotopography size triggering the ideal cell response. Here, nanoporous topography on 304L stainless steel substrates was engineered to identify the nanotopography size causing a transition in the cellular characteristics, and accordingly, the design of nanostructured stainless steel surface as orthopedic implants is proposed. A variety of nanopore diameters ranging from 100 to 220 nm were fabricated by one-step electrolysis process and collectively referred to as artificial microenvironments. Control over the nanopore diameter was achieved by varying bias voltage. MG63 osteoblasts were cultured on the nanoporous surfaces for different days. Immunofluorescence (IF) and scanning electron microscopy (SEM) were performed to compare the modulation in cell morphologies and characteristics. Osteoblasts displayed differential growth parameters and distinct transition in cell behavior after nanopore reached a certain diameter. Nanopores with 100-nm diameter promoted cell growth, focal adhesions, cell area, viability, vinculin-stained area, calcium mineralization, and alkaline phosphatase activity. The ability of these nanoporous substrates to differentially modulate the cell behavior and assist in identifying the transition step will be beneficial to biomedical engineers to develop superior implant geometries, triggering an ideal cell response at the cell-nanotopography interface.

Additive manufacturing of titanium alloys in the biomedical field: processes, properties and applications

The mechanical properties and biocompatibility of titanium alloy medical devices and implants produced by additive manufacturing (AM) technologies – in particular, selective laser melting (SLM), electron beam melting (EBM) and laser metal deposition (LMD) – have been investigated by several researchers demonstrating how these innovative processes are able to fulfil medical requirements for clinical applications. This work reviews the advantages given by these technologies, which include the possibility to create porous complex structures to improve osseointegration and mechanical properties (best match with the modulus of elasticity of local bone), to lower processing costs, to produce custom-made implants according to the data for the patient acquired via computed tomography and to reduce waste.

A Method for Collecting Single Cell Suspensions Using an Ultrasonic Pump

The presence of cell aggregates in cell suspensions may reduce cell culture efficiency because they can induce apoptosis and inhibit proliferation. To avoid this problem, this study proposes a novel method for collecting single cell suspensions from culture chambers for subculture using an ultrasonic pump driven by the squeeze film effect. First, we developed a cell culture device consisting of a cell culture substrate with a piezoelectric ceramic disk glued to the back, so that we can elicit resonance vibration of the substrate. A glass pipe is then placed vertically against the cell culture substrate with a slight gap (corresponding to cell diameter) between the pipe and the substrate. By exciting an out-of-plane resonance vibration of the cell culture substrate, we can collect a cell suspension from the cell culture chamber. Since the gap distance between the glass pipe and the cell culture substrate corresponds to cell diameter, the collected cell suspension only contains single cells. We evaluated the capability of the developed cell suspension pumping system and the proliferation of the collected cells with C2C12 myoblast cells. The ratio of single cells in the cell suspension was improved by up to 9.6% compared with that of suspensions collected by the control method (traditional pipetting). Moreover, after cultivating the collected cells for 72 hr, the cells collected by our method proliferated 13.6% more than those collected by the control method. These results suggest that the proposed method has great potential for improving the cultivation efficiency of adhesive cell culture.

In Vitro Adherence of Oral Bacteria to Different Types of Tongue Piercings

The purpose of this work was to verify in vitro adherence of E. corrodens and S. oralis to the surface of tongue piercings made of surgical steel, titanium, Bioplast, and Teflon. For this, 160 piercings were used for the count of Colony Forming Units (CFU) and 32 piercings for analysis under scanning electron microscopy. Of these, 96 (24 of each type) were individually incubated in 5 mL of BHI broth and 50 μL of inoculum at 37°C/24 h. The other 96 piercings formed the control group and were individually incubated in 5 mL of BHI broth at 37°C/24 h. Plates were incubated at 37°C/48 h for counting of CFU/mL and data were submitted to statistical analysis (p value <0.05). For E. corrodens, difference among types of material was observed (p < 0.001) and titanium and surgical steel showed lower bacterial adherence. The adherence of S. oralis differed among piercings, showing lower colonization (p < 0.007) in titanium and surgical steel piercings. The four types of piercings were susceptible to colonization by E. corrodens and S. oralis, and bacterial adhesion was more significant in those made of Bioplast and Teflon. The piercings presented bacterial colonies on their surface, being higher in plastic piercings probably due to their uneven and rough surface.

Improved antifouling properties and selective biofunctionalization of stainless steel by employing heterobifunctional silane-polyethylene glycol overlayers and avidin-biotin technology

A straightforward solution-based method to modify the biofunctionality of stainless steel (SS) using heterobifunctional silane-polyethylene glycol (silane-PEG) overlayers is reported. Reduced nonspecific biofouling of both proteins and bacteria onto SS and further selective biofunctionalization of the modified surface were achieved. According to photoelectron spectroscopy analyses, the silane-PEGs formed less than 10 Å thick overlayers with close to 90% surface coverage and reproducible chemical compositions. Consequently, the surfaces also became more hydrophilic, and the observed non-specific biofouling of proteins was reduced by approximately 70%. In addition, the attachment of E. coli was reduced by more than 65%. Moreover, the potential of the overlayer to be further modified was demonstrated by successfully coupling biotinylated alkaline phosphatase (bAP) to a silane-PEG-biotin overlayer via avidin-biotin bridges. The activity of the immobilized enzyme was shown to be well preserved without compromising the achieved antifouling properties. Overall, the simple solution-based approach enables the tailoring of SS to enhance its activity for biomedical and biotechnological applications.

An exploration of plastic deformation dependence of cell viability and adhesion in metallic implant materials

The relationship between cell viability and adhesion behavior, and micro-deformation mechanisms was investigated on austenitic 316L stainless steel samples, which were subjected to different amounts of plastic strains (5%, 15%, 25%, 35% and 60%) to promote a variety in the slip and twin activities in the microstructure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) revealed that cells most favored the samples with the largest plastic deformation, such that they spread more and formed significant filopodial extensions. Specifically, brain tumor cells seeded on the 35% deformed samples exhibited the best adhesion performance, where a significant slip activity was prevalent, accompanied by considerable slip-twin interactions. Furthermore, maximum viability was exhibited by the cells seeded on the 60% deformed samples, which were particularly designed in a specific geometry that could endure greater strain values. Overall, the current findings open a new venue for the production of metallic implants with enhanced biocompatibility, such that the adhesion and viability of the cells surrounding an implant can be optimized by tailoring the surface relief of the material, which is dictated by the micro-deformation mechanism activities facilitated by plastic deformation imposed by machining.

The effect of CO2 laser beam welded AISI 316L austenitic stainless steel on the viability of fibroblast cells, in vitro

It has been determined by the literature research that there is no clinical study on the in vivo and in vitro interaction of the cells with the laser beam welded joints of AISI 316L biomaterial. It is used as a prosthesis and implant material and that has adequate mechanical properties and corrosion resistance characteristics. Therefore, the interaction of the CO2 laser beam welded samples and samples of the base metal of AISI 316L austenitic stainless steel with L929 fibroblast cells as an element of connective tissue under in vitro conditions has been studied. To study the effect of the base metal and the laser welded test specimens on the viability of the fibroblast cells that act as an element of connective tissues in the body, they were kept in DMEMF-12 medium for 7, 14, 28 days and 18 months. The viability study was experimentally studied using the MTT method for 7, 14, 28 days. In addition, the direct interaction of the fibroblast cells seeded on 6 different plates with the samples was examined with an inverted microscope. The MTT cell viability experiment was repeated on the cells that were in contact with the samples. The statistical relationship was analyzed using a Tukey test for the variance with the GraphPad statistics software. The data regarding metallic ion release were identified with the ICP-MS method after the laser welded and main material samples were kept in cell culture medium for 18 months. The cell viability of the laser welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. However, the laser welded sample's viability of the fibroblast cells has diminished by time during the test period of 14 and 28 days and base metal shows better viability when compared to the laser welded samples. On the other hand, the base metal and the laser welded sample show better cell viability effect when compared to the control group. According to the ICP-MS results of the main material and laser welded samples which were kept in the cell culture medium for 18 months, it was determined that the Fe, Ni and Cr ion concentration released to the cell culture medium from the laser welded test sample was less than that of the main material.

The osteogenic properties of multipotent mesenchymal stromal cells in cultures on TiO₂ sol-gel-derived biomaterial

The biocompatibility of the bone implants is a crucial factor determining the successful tissue regeneration. The aim of this work was to compare cellular behavior and osteogenic properties of rat adipose-derived multipotent stromal cells (ASCs) and bone marrow multipotent stromal cells (BMSCs) cultured on metallic substrate covered with TiO2 sol-gel-derived nanolayer. The morphology, proliferation rate, and osteogenic differentiation potential of both ASCs and BMSCs propagated on the biomaterials were examined. The potential for osteogenic differentiation of ASCs and BMSCs was determined based on the presence of specific markers of osteogenesis, that is, alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OCL). Additionally, the concentration of calcium and phosphorus in extracellular matrix was determined using energy-dispersive X-ray spectroscopy (SEM-EDX). Obtained results showed that TiO2 layer influenced proliferation activity of ASCs, which manifested by shortening of population doubling time and increase of OPN secretion. However, characteristic features of cells morphology and growth pattern of cultures prompted us to conclude that ultrathin TiO2 layer might also enhance osteodifferentiation of BMSCs. Therefore in our opinion, both populations of MSCs should be used for biological evaluation of biomaterials compatibility, such results may enhance the area of investigations related to regenerative medicine.

Surface characteristics, corrosion resistance and MG63 osteoblast-like cells attachment behaviour of nano SiO2–ZrO2 coated 316L stainless steel

Nano ceramic coatings were produced on to 316L SS. MG-63 osteoblast like cells attachments were good for silica containing coatings.

Biofunctional hybrid materials: bimolecular organosilane monolayers on FeCr alloys

Hybrid organic-inorganic interfaces are the key to functionalization of stainless steel (SS). We present a solution-based deposition method for fabricating uniform bimolecular organosilane monolayers on SS and show that their properties and functionalities can be further developed through site-specific biotinylation. We correlate molecular properties of the interface with its reactivity via surface sensitive synchrotron radiation mediated high-resolution photoelectron spectroscopy (HR-PES) and chemical derivatization (CD), and we demonstrate specific bonding of streptavidin proteins to the hybrid interface. The method facilitates efficient growth of uniform bimolecular organosilane monolayers on SS under ambient conditions without the need to prime the SS surface with vacuum-deposited inorganic buffer layers. The obtained insights into molecular bonding, orientation, and behaviour of surface-confined organofunctional silanes on SS enable a new generic approach to functionalization of SS surfaces with versatile nanomolecular organosilane layers.

Dynamic contact angle analysis of protein adsorption on polysaccharide multilayer's films for biomaterial reendothelialization

Atherosclerosis is a major cardiovascular disease. One of the side effects is restenosis. The aim of this work was to study the coating of stents by dextran derivates based polyelectrolyte's multilayer (PEM) films in order to increase endothelialization of injured arterial wall after stent implantation. Films were composed with diethylaminoethyl dextran (DEAE) as polycation and dextran sulphate (DS) as polyanion. One film was composed with 4 bilayers of (DEAE-DS)4 and was labeled D-. The other film was the same as D- but with an added terminal layer of DEAE polycation: (DEAE-DS)4-DEAE (labeled D+). The dynamic adsorption/desorption of proteins on the films were characterized by dynamic contact angle (DCA) and atomic force microscopy (AFM). Human endothelial cell (HUVEC) adhesion and proliferation were quantified and correlated to protein adsorption analyzed by DCA for fibronectin, vitronectin, and bovine serum albumin (BSA). Our results showed that the endothelial cell response was optimal for films composed of DS as external layer. Fibronectin was found to be the only protein to exhibit a reversible change in conformation after desorption test. This behavior was only observed for (DEAE-DS)4 films. (DEAE-DS)4 films could enhance HUVEC proliferation in agreement with fibronectin ability to easily change from conformation.

Biomaterials and design in occlusion devices for cardiac defects: a review

This review examines the biomaterials used in occlusion devices for cardiac defects, and how the choice of these materials is dictated by design. Specifically, the devices used in three major applications, the atrial septal defect, the ventricular septal defect and the patent ductus arteriosus, are examined critically. A number of different devices are available, with varied performance in deployment and sealing. There is no device in any of the three categories that satisfies fully the range of requirements, and all have associated complications. The type and rate of complications are different among different devices. The short-term (immediate) complications are addressed by immediate retrieval. For longer-term complications, most of which can be fatal, currently only surgical retrieval and replacement are possible. Most of these longer-term complications can be alleviated by the use of fully degradable devices, which will eliminate concerns regarding the use of metals inside the heart, and if fully endothelialized, also minimize migration concerns. On the other hand, the lower moduli of currently available biodegradable materials need to be augmented. Improvements in the stiffness required for deployment can be accomplished with the use of fillers, nano- or micro-sized, and an example of this are radiopaque fillers.

Biocompatibility and characterization of a Kolsterised(®) medical grade cobalt-chromium-molybdenum alloy

High failure rates of cobalt-chromium-molybdenum (Co-Cr-Mo) metal-on-metal hip prosthesis were reported by various authors, probably due to the alloy's limited hardness and tribological properties. This thus caused the popularity of the alloy in metal-on-metal hip replacements to decrease due to its poor wear properties when compared with other systems such as ceramic-on-ceramic. S-phase surface engineering has become an industry standard when citing surface hardening of austenitic stainless steels. This hardening process allows the austenitic stainless steel to retain its corrosion resistance, while at the same time also improving its hardness and wear resistance. By coupling S-phase surface engineering, using the proprietary Kolsterising(®) treatment from Bodycote Hardiff GmbH, that is currently being used mainly on stainless steel, with Co-Cr-Mo alloys, an improvement in hardness and tribological characteristics is predicted. The objective of this paper is to analyze the biocompatibility of a Kolsterised(®) Co-Cr-Mo alloy, and to characterize the material surface in order to show the advantages gained by using the Kolsterised(®) material relative to the original untreated alloy, and other materials. This work has been performed on 3 fronts including; Material characterization, "In-vitro" corrosion testing, and Biological testing conforming to BS EN ISO 10993-18:2009 - Biological evaluation of medical devices. Using these techniques, the Kolsterised(®) cobalt-chromium-molybdenum alloys were found to have good biocompatibility and an augmented corrosion resistance when compared with the untreated alloy. The Kolsterised(®) samples also showed a 150% increase in surface hardness over the untreated material thus predicting better wear properties.

Biocompatibility studies of low temperature nitrided and collagen-I coated AISI 316L austenitic stainless steel

The biocompatibility of austenitic stainless steels can be improved by means of surface engineering techniques. In the present research it was investigated if low temperature nitrided AISI 316L austenitic stainless steel may be a suitable substrate for bioactive protein coating consisting of collagen-I. The biocompatibility of surface modified alloy was studied using as experimental model endothelial cells (human umbilical vein endothelial cells) in culture. Low temperature nitriding produces modified surface layers consisting mainly of S phase, the supersaturated interstitial solid solution of nitrogen in the austenite lattice, which allows to enhance surface microhardness and corrosion resistance in PBS solution. The nitriding treatment seems to promote the coating with collagen-I, without chemical coupling agents, in respect of the untreated alloy. For biocompatibility studies, proliferation, lactate dehydrogenase levels and secretion of two metalloproteinases (MMP-2 and MMP-9) were determined. Experimental results suggest that the collagen protection may be favourable for endothelial cell proliferation and for the control of MMP-2 release.

SEM and EDS investigation of a pyrolytic carbon covered C/C composite maxillofacial implant retrieved from the human body after 8 years

The long term effect of the human body on a pyrolytic carbon covered C/C composite maxillofacial implant (CarBulat(Tm)) was investigated by comparing the structure, the surface morphology and composition of an implant retrieved after 8 years to a sterilized, but not implanted one. Although the thickness of the carbon fibres constituting the implants did not change during the 8 year period, the surface of the implant retrieved was covered with a thin surface layer not present on the unimplanted implant. The composition of this layer is identical to the composition of the underlying carbon fibres. Calcium can only be detected on the surface as a trace element implying that the new layer is not formed by bone tissue. Residual soft tissue penetrating the bulk material between the carbon fibre bunches was found on the retrieved implant indicating the importance of the surface morphology in tissue growth and adhering to implants.

Grit blasting of medical stainless steel: implications on its corrosion behavior, ion release and biocompatibility

This study reports on the biocompatibility of 316 LVM steel blasted with small and rounded ZrO(2) particles or larger and angular shaped Al(2)O(3) particles. The effect of blasting on the in vitro corrosion behavior and the associated ion release is also considered. Surface of Al(2)O(3) blasted samples was rougher than that of ZrO(2) blasted samples, which was also manifested by a higher surface area. Compared to the polished alloy, blasted steels exhibited a lower corrosion resistance at the earlier stages of immersion, particularly when using Al(2)O(3) particles. With increasing immersion time, blasted samples experienced an improvement of the corrosion resistance, achieving impedance values typical of passive alloys. Blasting of the alloy led to an increase in Fe release and the leaching of Ni, Mn, Cr and Mo. On all surfaces, ion release is higher during the first 24 h exposure and tends to decrease during the subsequent exposure time. Despite the lower corrosion resistance and higher amount of ions released, blasted alloys exhibit a good biocompatibility, as demonstrated by culturing osteoblastic cells that attached and grew on the surfaces.

Cytocompatibility of medical biomaterials containing nickel by osteoblasts: a systematic literature review

The present review is based on a survey of 21 studies on the cytocompatibility of medical biomaterials containing nickel, as assessed by cell culture of human and animal osteoblasts or osteoblast-like cells. Among the biomaterials evaluated were stainless steel, NiTi alloys, pure Ni, Ti, and other pure metals. The materials were either commercially available, prepared by the authors, or implanted by various techniques to generate a protective layer of oxides, nitrides, acetylides. The observation that the layers significantly reduced the initial release of metal ions and increased cytocompatibility was confirmed in cell culture experiments. Physical and chemical characterization of the materials was performed. This included, e.g., surface characterization (roughness, wettability, corrosion behavior, quantity of released ions, microhardness, and characterization of passivation layer). Cytocompatibility tests of the materials were conducted in the cultures of human or animal osteoblasts and osteoblast-like cells. The following assays were carried out: cell proliferation and viability test, adhesion test, morphology (by fluorescent microscopy or SEM). Also phenotypic and genotypic markers were investigated. In the majority of works, it was found that the most cytocompatible materials were stainless steel and NiTi alloy. Pure Ni was rendered and less cytocompatible. All the papers confirmed that the consequence of the formation of protective layers was in significant increase of cytocompatibility of the materials. This indicates the possible further modifications of the manufacturing process (formation of the passivation layer).

Soft tissue response to titanium dioxide nanotube modified implants

Titanium is widely used clinically, yet little is known regarding the effects of modifying its three-dimensional surface geometry at the nanoscale level. In this project we have explored the in vivo response in terms of nitric oxide scavenging and fibrotic capsule formation to nano-modified titanium implant surfaces. We compared titanium dioxide (TiO(2)) nanotubes with 100 nm diameters fabricated by electrochemical anodization with TiO(2) control surfaces. Significantly lower nitric oxide was observed for the nanostructured surface in solution, suggesting that nanotubes break down nitric oxide. To evaluate the soft tissue response in vivo TiO(2) nanotube and TiO(2) control implants were placed in the rat abdominal wall for 1 and 6 weeks. A reduced fibrotic capsule thickness was observed for the nanotube surfaces for both time points. Significantly lower nitric oxide activity, measured as the presence of nitrotyrosine (P<0.05), was observed on the nanotube surface after 1 week, indicating that the reactive nitrogen species interaction is of importance. The differences observed between the titanium surfaces may be due to the catalytic properties of TiO(2), which are increased by the nanotube structure. These findings may be significant for the interaction between titanium implants in soft tissue as well as bone tissue and provide a mechanism by which to improve future clinical implants.

Evaluation of the biocompatibility of S-phase layers on medical grade austenitic stainless steels

S-phase surface layers were formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C). The presence of the S-phase was confirmed by microscopy, hardness testing, depth-profile analysis of chemical composition and X-ray Diffraction. Attachment and proliferation of mouse osteoblast MC3T3-E1 cells were tested on S-phase and untreated controls and the results demonstrated that all the S-phase layers formed were biocompatible under the conditions used. Cells adhered equally well to all samples but proliferation was enhanced on the treated materials.

Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al-12.6%Si alloy

Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al-12.6%Si alloy for 120 s. The coating consists of the Al(12)(Fe,Cr)(3)Si(2) intermetallic. In vitro corrosion behaviour has been evaluated in the Ringer's solution by means of potentiodynamic curves and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised corrosion with respect to the substrate. XPS analysis suggests that the ennoblement of the pitting potential is due to the formation of a chromium oxyhydroxide containing passive layer. The intermetallic coating shows a good biocompatibility, as demonstrated by culturing human mesenchymal stem cells isolated from bone marrow which attached, grew and differentiated to the osteoblastic lineage to a similar extent on coated and bare steels. In summary, this study proposes a method that generates Ni-free coatings of the stainless steel with useful properties for biomedical applications.

Titanium dioxide nanotubes enhance bone bonding in vivo

Implant topography is critical to the clinical success of bone-anchored implants, yet little is known how nano-modified implant topography affects osseointegration. We investigate the in vivo bone bonding of two titanium implant surfaces: titanium dioxide (TiO(2)) nanotubes and TiO(2) gritblasted surfaces. In previous in vitro studies, the topography of the TiO(2) nanotubes improved osteoblast proliferation and adhesion compared with gritblasted titanium surfaces. After four weeks of implantation in rabbit tibias, pull-out testing indicated that TiO(2) nanotubes significantly improved bone bonding strength by as much as nine-fold compared with TiO(2) gritblasted surfaces. Histological analysis confirmed greater bone-implant contact area, new bone formation, and calcium and phosphorus levels on the nanotube surfaces. It is anticipated that further studies will contribute to a better understanding of the effect of implant nanotopography on in vivo bone formation and bonding strength.

Bactericidal and biocompatible properties of TiN/Ag multilayered films by ion beam assisted deposition

Nanoscale TiN/Ag multilayered films of thickness 500 nm were synthesized on AISI317 stainless steel by ion beam assisted deposition (IBAD) with the modulation period of 4, 5, 6, 7.5, and 12 nm. The bactericidal and biocompatible properties of TiN/Ag multilayered films were investigated through Gram negative E. coli bacteria and L929 cells (mice fibroblast) as well as human umbilical vein endothelial cells (HUVEC). The results show that the TiN/Ag multilayered films with the modulation period of 7.5 nm possess the strongest bactericidal property. The cytotoxicity grade of TiN/Ag multilayered coating with the modulation periods of 7.5 nm, 12 nm is in 0-1 scope, which indicates this film has no cytotoxicity to L929. HUVEC on TiN/Ag multilayered film grows well and shows good cellularity. Auger electronic spectroscopy reveals the relationship between the structure of TiN/Ag multilayered film and the biomedical properties.

The positive influence of electrochemical cyclic potentiodynamic passivation (CPP) of a SS316LS surface on its response to fibronectin and pre-osteoblasts

The influence of an electrochemical surface passivation technique (cyclic potentiodynamic polarization, CPP) on the physico-chemical surface properties of SS316LS and its subsequent response to fibronectin (Fn) and pre-osteoblasts were investigated. Contact angle and zeta-potential measurements showed that the CPP-modified surface is more hydrophilic and more positively charged than the unmodified surface. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to investigate the interaction of Fn with both surfaces. The saturated surface concentration of adsorbed Fn was higher on the CPP-modified surface. As well, significant changes were identified in the secondary structure of Fn adsorbed on both surfaces, in comparison to its native state. This data also indicated a higher degree of Fn unfolding on the CPP-modified surface. Cell studies indicated that the attachment, proliferation and morphology of pre-osteoblasts were significantly improved on the CPP-modified surface, which was attributed to the more open conformation of Fn on the CPP-modified surface. Thus, the CPP surface passivation method was demonstrated to yield a SS316LS surface of enhanced biocompatibility.

Bioreactor design for cornea tissue engineering: Material-cell interactions

Several materials were evaluated for potential use in a bioreactor system for a tissue-engineered cornea. Two types of cytotoxicity tests were performed using human corneal stromal fibroblasts: a 24h cytotoxicity test based on the ASTM standard F813-01 and a 7 days growth inhibition test. It was determined that culture configuration, autoclaving and materials surface preparation were all important factors influencing cell viability. Poly(etheretherketone) and titanium-6Al-4V were found to be the most appropriate materials for use in a corneal bioreactor system. Furthermore, poly(oxymethylene) copolymer and poly(tetrafluoroethlylene) are not safe for use with human corneal fibroblasts after autoclaving.

Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel-titanium alloys: a comparative study with commonly used medical grade materials

Stainless steel and titanium alloys are the most common metallic orthopedic materials. Recently, nickel-titanium (NiTi) shape memory alloys have attracted much attention due to their shape memory effect and super-elasticity. However, this alloy consists of equal amounts of nickel and titanium, and nickel is a well known sensitizer to cause allergy or other deleterious effects in living tissues. Nickel ion leaching is correspondingly worse if the surface corrosion resistance deteriorates. We have therefore modified the NiTi surface by nitrogen plasma immersion ion implantation (PIII). The surface chemistry and corrosion resistance of the implanted samples were studied and compared with those of the untreated NiTi alloys, stainless steel, and Ti-6Al-4V alloy serving as controls. Immersion tests were carried out to investigate the extent of nickel leaching under simulated human body conditions and cytocompatibility tests were conducted using enhanced green fluorescent protein mice osteoblasts. The X-ray photoelectron spectroscopy results reveal that a thin titanium nitride (TiN) layer with higher hardness is formed on the surface after nitrogen PIII. The corrosion resistance of the implanted sample is also superior to that of the untreated NiTi and stainless steel and comparable to that of titanium alloy. The release of nickel ions is significantly reduced compared with the untreated NiTi. The sample with surface TiN exhibits the highest amount of cell proliferation whereas stainless steel fares the worst. Compared with coatings, the plasma-implanted structure does not delaminate as easily and nitrogen PIII is a viable way to improve the properties of NiTi orthopedic implants.

Biocompatibility evaluation of surface-treated AISI 316L austenitic stainless steel in human cell cultures

The effects of AISI 316L austenitic stainless steel, tested in untreated state or subjected to glow-discharge nitriding (at 10 or 20 hPa) and nitriding + post-oxidizing treatments, on human umbilical vein endothelial cells (HUVEC) and on peripheral blood mononuclear cells (PBMC) were evaluated. All the treated samples showed a better corrosion resistance in PBS and higher surface hardness in comparison with the untreated alloy. In HUVEC put in contact for 72 h with the sample types, proliferation and apoptosis decreased and increased, respectively, in the presence of the nitrided + post-oxidized samples, while only slight differences in cytokine (TNF-alpha, IL-6, and TGF-beta1) release were registered. Intercellular adhesion molecule-1 (ICAM-1) increased in HUVEC incubated with all the treated samples, while vascular cell adhesion molecule-1 (VCAM-1) and E-selectin increased in the presence of all the sample types. PBMC incubated for 48 h with the samples showed a decrease in proliferation and an increase in apoptosis in the presence of the untreated samples and the nitrided + post-oxidized ones. All the sample types induced a remarkable increase in TNF-alpha and IL-6 release in PBMC culture medium, while only the untreated sample and the nitrided at 10 hPa induced an increase in ICAM-1 expression. In HUVEC cocultured with PBMC, previously put in contact with the treated AISI 316L samples, increased levels of ICAM-1 were detected. In HUVEC coincubated with the culture medium of PBMC, previously put in contact with the samples under study, a noteworthy increase in ICAM-1, VCAM-1, and E-selectin levels was always registered, with the exception of VCAM-1, which was not affected by the untreated sample. In conclusion, even if the treated samples do not show a marked increase in biocompatibility in comparison with the untreated alloy, their higher corrosion resistance may suggest a better performance as the contact with physiological environment becomes longer.

Cytotoxicity study of plasma-sprayed hydroxyapatite coating on high nitrogen austenitic stainless steels

Stainless steel has been frequently used for temporary implants but its use as permanent implants is restricted due to its low pitting corrosion resistance. Nitrogen additions to these steels improve both mechanical properties and corrosion resistance, particularly the pitting and crevice corrosion resistance. Many reports concerning allergic reactions caused by nickel led to the development of nickel free stainless steel; it has excellent mechanical properties and very high corrosion resistance. On the other hand, stainless steels are biologically tolerated and no chemical bonds are formed between the steel and the bone tissue. Hydroxyapatite coatings deposited on stainless steels improve osseointegration, due their capacity to form chemical bonds (bioactive fixation) with the bone tissue. In this work hydroxyapatite coatings were plasma-sprayed on three austenitic stainless steels: ASTM-F138, ASTM-F1586 and the nickel-free Böhler-P558. The coatings were analyzed by SEM and XDR. The cytotoxicity of the coatings/steels was studied using the neutral red uptake method by quantitative evaluation of cell viability. The three uncoated stainless steels and the hydroxyapatite coated Böhler-P558 did not have any toxic effect on the cell culture. The hydroxyapatite coated ASTM-F138 and ASTM-F1586 stainless steels presented cytotoxicity indexes (IC50%) lower than 50% and high nickel contents in the extracts.