Biocompatibility of alumina ceramic and polyethylene as materials for pivot bearings of a centrifugal blood pump

Enhancement of the anticoagulant capacity of polyvinyl chloride tubing for cardiopulmonary bypass circuit using aluminum oxide nanoscale coating applied through atomic layer deposition

For cardiopulmonary bypass, the polyvinyl chloride (PVC) circuit which can initiate the activation of platelets and the coagulation cascade after blood cell contacting is the possible detrimental effect. Surface coating of the PVC tubing system can be an effective approach to enhance circuit's hemocompatibility. In this study, aluminum oxide (Al₂ O₃ ) thin films were deposited through thermal atomic layer deposition (T-ALD) or plasma-enhanced ALD (PE-ALD) on PVC samples, and the anticoagulation of the Al₂ O₃ -coated PVC samples was demonstrated. The results revealed that Al₂ O₃ deposition through ALD increased surface roughness, whereas T-ALD had a relative hydrophilicity compared with blank PVC and PE-ALD. Whole blood immersion tests showed that blood clots formed on blank PVC and that a large amount of red blood cells was found on PE-ALD substrates, whereas less blood cells were noted in T-ALD samples. Both T-ALD and PE-ALD Al₂ O₃ films did not cause activation of blood cells, as evidenced in CD3⁺ /CD4⁺ /CD8⁺ , CD61⁺ /CD62P⁺ , and CD45⁺ /CD42b⁺ populations. Analysis of serum coagulation factors showed that a lower amount of prothrombin was absorbed on T-ALD Al₂ O₃ samples than that on blank PVC. For albumin and fibrinogen immersion tests, immunostaining and scanning electron microscopy further revealed that a thin albumin layer was absorbed on T-ALD Al₂ O₃ substrates but not on PVC samples. This study revealed that deposition of Al₂ O₃ films by T-ALD can improve anticoagulation of the PVC tubing system.

Geometric Optimization of an Extracorporeal Centrifugal Blood Pump with an Unshrouded Impeller Concerning Both Hydraulic Performance and Shear Stress

Centrifugal blood pumps have provided a powerful artificial support system for patients with vascular diseases. In the design process, geometrical optimization is usually needed to acquire a more biocompatible model for clinical uses. In the current paper, we propose a method for multi-objective optimization concerning both the hydraulic and the hemolytic performances of the pump based on the near-orthogonal array in which the traditional hemolysis index (HI) is replaced with the maximum scalar shear stress criteria to reduce the computation load. The method is demonstrated with the optimization of an extracorporeal centrifugal blood pump with an unshrouded impeller. CFD studies on the original and nine modified pump models are carried out. The calculated hydraulic performances of the optimized model are also compared against the experiments for validation of the numeric method, with an error of 3.6% at the original design point. The resulting blood pump with low maximum scalar shear stress (132.2 Pa) shows a low degree of calculated HI (1.69 × 10−3).

Nano-porous anodic alumina: fundamentals and applications in tissue engineering

Recently, nanomaterials have been widely utilized in tissue engineering applications due to their unique properties such as the high surface to volume ratio and diversity of morphology and structure. However, most methods used for the fabrication of nanomaterials are rather complicated and costly. Among different nanomaterials, anodic aluminum oxide (AAO) is a great example of nanoporous structures that can easily be engineered by changing the electrolyte type, anodizing potential, current density, temperature, acid concentration and anodizing time. Nanoporous anodic alumina has often been used for mammalian cell culture, biofunctionalization, drug delivery, and biosensing by coating its surface with biocompatible materials. Despite its wide application in tissue engineering, thorough in vivo and in vitro studies of AAO are still required to enhance its biocompatibility and thereby pave the way for its application in tissue replacements. Recognizing this gap, this review article aims to highlight the biomedical potentials of AAO for applications in tissue replacements along with the mechanism of porous structure formation and pore characteristics in terms of fabrication parameters.

Effect of the Compositions on the Biocompatibility of New Alumina-Zirconia-Titania Dental Ceramic Composites

Dental implant biomaterials are expected to be in contact with living tissues, therefore their toxicity and osseointegration ability must be carefully assessed. In the current study, the wettability, cytotoxicity, and genotoxicity of different alumina-zirconia-titania composites were evaluated. The surface wettability determines the biological event cascade in the bioceramic/human living tissues interface. The measured water contact angle indicated that the wettability strongly depends on the ceramic composition. Notwithstanding the contact angle variability, the ceramic surfaces are hydrophilic. The cytotoxicity of human gingival fibroblast cells with materials, evaluated by an (3-(4,5 methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) test, revealed an absence of any cytotoxic effect. A relationship was found between the cell viability and the wettability. It was subsequently deduced that the cell viability increases when the wettability increases. This effect is more pronounced when the titania content is higher. Finally, a comet test was applied as complementary biocompatibility test to detect any changes in fibroblast cell DNA. The results showed that the DNA damage is intimately related to the TiO₂ content. Genotoxicity was mainly attributed to ceramic composites containing 10 wt.% TiO₂. Our research revealed that the newly developed high performance alumina-zirconia-titania ceramic composites contain less than 10 wt.% TiO₂, and display promising surface properties, making them suitable for dental implantology applications.

Synthesis and Electrospinning of Polycaprolactone from an Aluminium-Based Catalyst: Influence of the Ancillary Ligand and Initiators on Catalytic Efficiency and Fibre Structure

In the present study, we investigated the catalytic performance of a 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (MDBP)⁻aluminium complex for the ring-opening polymerisation (ROP) of ε-caprolactone in combination with various alcohols as initiators. Three different alcohols were investigated: 1-adamantanemethanol (A), 1H,1H,2H,2H-perfluoro-1-octanol (F) and isopropanol (I). Samplings of polycaprolactone (PCL) at various reaction times showed a linear increase in the polymer molecular weight with time, with very narrow polydispersity, confirming the living nature of the catalytic system. Scanning electron microscope (SEM) images of electrospun PCL fibre mats produced from 30 wt % dichloromethane/dimethyl sulfoxide solutions showed a high level of surface porosity with a reasonable homogeneity of fibre diameters. The values of the liquid absorption and water contact angle were measured for the electrospun mats, with the F-capped PCL consistently showing absorption values up to three times higher than those of PCL samples capped with the other two alcohols, as well as increased hydrophobicity. The nature of the alcohol can influence the surface hydrophobicity and absorption ability of electrospun fibres, demonstrating the possibility of tailoring material properties through controlled polymerisation.

The effect of ventricular assist device-associated biomaterials on human blood leukocytes

Ventricular assist devices (VADs) are an effective bridging or destination therapy for patients with advanced stage heart failure. These devices remain susceptible to adverse events including infection, bleeding, and thrombus; events linked to the foreign body response. Therefore, the biocompatibility of all biomaterials used is crucial to the success of medical devices. Biomaterials common in VADs-DLC: diamond-like carbon coated stainless steel; Sap: single-crystal sapphire; SiN: silicon nitride; Ti: titanium alloy; and ZTA: zirconia-toughened alumina-were tested for their biocompatibility through incubation with whole human blood for 2 h with mild agitation. Blood was then removed and used for: complete cell counts; leukocyte activation and death, and the production of key inflammatory cytokines. All were compared to time 0 and an un-exposed 2 h sample. Monocyte numbers were lower after exposure to DLC, SiN, and ZTA and monocytes showed evidence of activation with DLC, Sap, and SiN. Neutrophils and lymphocytes were unaffected. This approach allows comprehensive analysis of the potential blood damaging effects of biomaterials. Monocyte activation by DLC, Sap, ZTA, and SiN warrants further investigation linking effects on this cell type to unfavorable inflammatory/thrombogenic responses to VADs and other blood handling devices. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1730-1738, 2018.

Effect of micro-arc oxidation surface modification on the properties of the NiTi shape memory alloy

In this paper, the effects of micro-arc oxidation (MAO) surface modification (alumina coatings) on the phase transformation behavior, shape memory characteristics, in vitro haemocopatibility and cytocompatibility of the biomedical NiTi alloy were investigated respectively by differential scanning calorimetry, bending test, hemolysis ratio test, dynamic blood clotting test, platelet adhesion test and cytotoxicity testing by human osteoblasts (Hobs). The results showed that there were no obvious changes of the phase transformation temperatures and shape memory characteristics of the NiTi alloy after the MAO surface modification and the coating could withstand the thermal shock and volume change caused by martensite-austenite phase transformation. Compared to the uncoated NiTi alloys, the MAO surface modification could effectively improve the haemocopatibility of the coated NiTi alloys by the reduced hemolysis ratio, the prolonged dynamic clotting time and the decreased number of platelet adhesion; and the rough and porous alumina coatings could obviously promote the adherence, spread and proliferation of the Hobs with the significant increase of proliferation number of Hobs adhered on the surface of the coated NiTi alloys (P < 0.05).

Reinforcement of electrospun membranes using nanoscale Al2O3 whiskers for improved tissue scaffolds

Poly(ε-caprolactone) (PCL) is a promising material for tissue engineering applications; however, it can be difficult to create scaffolds with the morphology, hydrophilicity, and mechanical properties necessary to support tissue growth. Typically, pure PCL scaffolds have good cellular adhesion, but somewhat low mechanical properties (elastic modulus and tensile strength). This study addresses these issues by incorporating Al(2)O(3) whiskers as reinforcements within PCL membranes generated by electrospinning. Membranes were prepared with Al(2)O(3) content ranging from 1 to 20 wt % and characterized using XRD, TEM, and SEM to determine composition and morphology. The Al(2)O(3) whiskers were well dispersed within the PCL fibers, and the membranes had a highly porous morphology. The elastic modulus was significantly improved by the well aligned whisker reinforcements as verified by tensile testing. The cell morphology and proliferation studies demonstrate Al(2)O(3) whisker reinforced PCL scaffolds maintained the good biocompatibility. These improvements demonstrate that Al(2)O(3) whisker reinforced PCL scaffolds can be considered as a biocompatible material for tissue engineering and dental applications.

Development of a New Zirconia-Toughened Alumina: Promising Mechanical Properties and Absence of In Vitro Carcinogenicity

High purity alumina as well as zirconia ceramics have been widely used as orthopaedic implant biomaterials and dental devices displaying optimal, but sometimes exclusive, mechanical properties. In order to combine the advantages of alumina and zirconia ceramic materials different types of composites have been developed in which either zirconia is dispersed in an alumina matrix or vice versa. Orthopaedic and dental implant biomaterials are expected to be in contact with living tissues for a long period of time and their long term toxicity must be carefully evaluated. In this study we report the development of a high performance chromia-doped Zirconia Toughened Alumina (ZTA) material which displays promising mechanical properties in terms of hardness, strength and fracture toughness that make it suitable for prosthesis even for small joints. The long-term biocompatibility of this material was also evaluated, mainly in terms of DNA damage, mutagenicity and cancerogenetic potential in mammalian cells. The results obtained suggest that this new ZTA material does not display any long-term carcinogenic effect and it is suitable for biomedical applications from a cancerogenetic point of view. In conclusion, we report the development of a new chromia-doped ZTA material with interesting properties both from a mechanical and a biocompatibility point of view which warrant further studies on its suitability as a candidate biomaterial for orthopaedic implants and dental devices.

Genotoxicity evaluation of locally produced dental porcelain--an in vitro study using the Ames and Comet assays

The aim of this study was to determine the genotoxicity of a locally produced dental porcelain (Universiti Sains Malaysia, Malaysia) using the Ames and Comet assays. In the Ames assay, four genotypic variants of the Salmonella strains (TA98, TA100, TA1537 and TA1535) carrying mutations in several genes were used. The dental porcelain was incubated with these four strains in five different doses both in the presence and absence of metabolic activation (S9) and the result was assessed based on the number of revertant colonies. Concurrently, appropriate positive controls were used so as to validate the test. The average number of revertant colonies per plate treated with locally produced dental porcelain was less than double as compared to that of negative control. In the Comet assay, L929 (CCL-1 ATCC, USA) mouse fibroblast cells were treated with the dental porcelain in three different concentrations along with concurrent negative and positive controls. The tail moment which was used as a measurement of DNA damage was almost equal to that of the negative control, suggesting that the locally produced dental porcelain did not induce any DNA damage. The results indicated that the locally produced dental porcelain is non-genotoxic under the present test conditions.

Biocompatibility of atomic layer-deposited alumina thin films

Presented in this paper is a study of the biocompatibility of an atomic layer-deposited (ALD) alumina (Al2O3) thin film and an ALD hydrophobic coating on standard glass cover slips. The pure ALD alumina coating exhibited a water contact angle of 55 degrees +/- 5 degrees attributed, in part, to a high concentration of -OH groups on the surface. In contrast, the hydrophobic coating (tridecafluoro-1,1,2,2-tetrahydro-octyl-methyl-bis(dimethylamino)silane) had a water contact angle of 108 degrees +/- 2 degrees. Observations using differential interference contrast microscopy on human coronary artery smooth muscle cells showed normal cell proliferation on both the ALD alumina and hydrophobic coatings when compared to cells grown on control substrates. These observations suggested good biocompatibility over a period of 7 days in vitro. Using a colorimetric assay technique to assess cell viability, the cellular response between the three substrates can be differentiated to show that the ALD alumina coating is more biocompatible and that the hydrophobic coating is less biocompatible when compared to the control. These results suggest that patterning a substrate with hydrophilic and hydrophobic groups can control cell growth. This patterning can further enhance the known advantages of ALD alumina, such as conformality and excellent dielectric properties for bio-micro electro mechanical systems (Bio-MEMS) in sensors, actuators, and microfluidics devices.

Biocompatibility: meeting a key functional requirement of next-generation medical devices

The array of polymeric, biologic, metallic, and ceramic biomaterials will be reviewed with respect to their biocompatibility, which has traditionally been viewed as a requirement to develop a safe medical device. With the emergence of combination products, a paradigm shift is occurring that now requires biocompatibility to be designed into the device. In fact, next-generation medical devices will require enhanced biocompatibility by using, for example, pharmacological agents, bioactive coatings, nano-textures, or hybrid systems containing cells that control biologic interactions to have desirable biologic outcomes. The concept of biocompatibility is moving from a "do no harm" mission (i.e., nontoxic, nonantigenic, nonmutagenic, etc.) to one of doing "good," that is, encouraging positive healing responses. These new devices will promote the formation of normal healthy tissue as well as the integration of the device into adjacent tissue. In some contexts, biocompatibility can become a disruptive technology that can change therapeutic paradigms (e.g., drug-coated stents). New database tools to access biocompatibility data of the materials of construction in existing medical devices will facilitate the use of existing and new biomaterials for new medical device designs.

Ten-year NEDO BVAD development program: moving forward to the clinical arena

Since 1995, the Baylor Group has been developing a totally implantable NEDO BVAD system. This 10-year program was completed in March 2005, and preparation for clinical trials is underway. This article summarizes the entire 10-year NEDO program and describes the strategy for clinical trials. The project aimed to achieve: (1) dual centrifugal pumps with the ability of full biventricular support, (2) a compact system implantable into small adults, (3) a totally implantable system with transcutaneous energy transmission system (TETS), (4) a durable system with a lifetime of over 5 years, and (5) a system free of thrombus and with minimal hemolysis. The final goals are to complete preclinical system evaluations and commence the clinical trials in the near future. In vitro studies have demonstrated a pump capacity of over 8.5 l/min and an Index of Hemolysis of <0.004 g/100 l. The pump-bearing life expectancy was over 5 years. To date, eight pumps endured in vivo studies of over 3 months without complications, including thromboembolic events. The in vitro endurance studies of eight pumps are longer than 1 year. There were no mechanical malfunctions or pump failure. A stepwise clinical trial is being planned: Step1, a wearable BVAD/VAD will be clinically studied; Step 2, the BVAD/VAD will be implanted intracorporeally without TETS; and, Step 3, a totally implantable system will be clinically evaluated. The NEDO BVAD system has completed preclinical testing. Clinical trial preparation is underway.

Nanoporous Alumina Membranes for Enhancing Hemodialysis

The nonuniformity of pore size and pore distribution of the current hemodialysis membrane results in low efficiency of uremic solute removal as well as the loss of albumin. By using nanotechnology, an anodic alumina membrane (ceramic membrane) with self-organized nanopore structure was produced. The objective of this study was to fabricate nanoporous alumina membranes and investigate the correlation between various anodization conditions and the pore characteristics in order to find its potential application in artificial kidney/hemodialysis. An aluminum thin film was oxidized in two electrolytes consisting of 3% and 5% sulfuric acid and 2.7% oxalic acid. The applied voltages were 12.5, 15, 17.5, and 20V for sulfuric acid and 20, 30, 40, and 50V for oxalic acid. Pore size and porosity were determined by analyzing Scanning Electron Microscopy (SEM) images and hydraulic conductivity was measured. Results show that pore size increased linearly with voltage. Acid concentration affected pore formation but not pore size and pore distribution. Hydraulic conductivity of the ceramic membrane was higher than that of the polymer dialysis membrane. The optimal formation conditions for self-organized nanopore structure of the ceramic membrane were 12.5-17.5V in 3–5% sulfuric acid at 0°C. Under these conditions, ceramic membranes with pores size of ∼10nm diameter can be produced. In conclusion, we used anodic alumina technology to reliably produce in quantity ceramic membranes with a pore diameter of 10-50nm. Because of more uniform pore size, high porosity, high hydraulic conductivity, and resistance to high temperature, the ceramic membrane has the potential application as a hemodialysis membrane.

Synergistic effects of a novel nanoporous stent coating and tacrolimus on intima proliferation in rabbits

To overcome the problem of in-stent restenosis, the concept of local delivery of antiproliferative or immunosuppressive drugs has been introduced into interventional cardiology. Local drug delivery can be achieved by drug-eluting stents coated with polymer surfaces used for controlled drug release. However, several polymer coatings have shown an induction of inflammatory response and increased neointima formation. In the present study, the effect of a new inorganic ceramic nanoporous aluminum oxide (Al(2)O(3)) coating on neointima proliferation and its suitability as a carrier for the immunosuppressive drug tacrolimus have been investigated. 316 L stainless steel coronary stents were coated with a 500 nm thin nanoporous aluminum oxide layer. This ceramic nanolayer was used as a carrier for tacrolimus. Bare stents (n = 6), ceramic coated stents (n = 6), and ceramic coated stents loaded with 60 (n = 7) and 120 mug (n = 6) tacrolimus were implanted in the common carotid artery of New Zealand rabbits. The ceramic coating caused no significant reduction of neointimal thickness after 28 days. Loading the ceramic stents with tacrolimus led to a significant reduction of neointima thickness by 52% for 60 mug (P = 0.047) and 56% for 120 mug (P = 0.036) as compared to the bare stents. The ceramic coating alone as well as in combination with tacrolimus led to a reduced infiltration of lymphocytes and macrophages in the intima in response to stent implantation. Ceramic coating of coronary stents with a nanoporous layer of aluminum oxide in combination with tacrolimus resulted in a significant reduction in neointima formation and inflammatory response. The synergistic effects of the ceramic coating and tacrolimus suggest that this new approach may have a high potential to translate into clinical benefit.

Biocompatibility of electroactive polymers in tissues

The biocompatibility of ethylene-vinyl acetate copolymer (EVAc), polyethylene (PE), and polyaniline (PANi) films in the emeraldine (EM), nigraniline (NA) and leucoemeraldine (LM) intrinsic oxidation states were assessed through subcutaneous implantation into male Sprague-Dawley rats beneath the dorsal skin, for a period ranging from 19 to 90 weeks. Histological examination, interstitial pressure measurement, and X-ray photoelectron spectroscopy (XPS) were employed to determine the biocompatibility of the polymers. The polymers did not provoke inflammatory responses in the subcutaneous tissues over the entire implantation period. Characteristics features associated with tissue-implant incompatibility were not evident near the implantation. Interstitial pressure was measured to evaluate the development of tissue. Low interstitial pressure readings on the region of implantation confirmed the biocompatibility of these polymer types. The surface composition of the electroactive aniline polymers before and after the implantation was characterized by XPS.