Reducing MRI susceptibility artefacts in implants using additively manufactured porous Ti-6Al-4V structures.

Magnetic Resonance Imaging (MRI) is critical in diagnosing post-operative complications following implant surgery and imaging anatomy adjacent to implants. Increasing field strengths and use of gradient-echo sequences have highlighted difficulties from susceptibility artefacts in scan data. Artefacts manifest around metal implants, including those made from titanium alloys, making detection of complications (e.g. bleeding, infection) difficult and hindering imaging of surrounding structures such as the brain or inner ear. Existing research focusses on post-processing and unorthodox scan sequences to better capture data around these devices. This study proposes a complementary up-stream design approach using lightweight structures produced via additive manufacturing (AM). Strategic implant mass reduction presents a potential tool in managing artefacts. Uniform specimens of Ti-6Al-4V structures, including lattices, were produced using the AM process, selective laser melting, with various unit cell designs and relative densities (3.1%-96.7%). Samples, submerged in water, were imaged in a 3T MRI system using clinically relevant sequences. Artefacts were quantified by image analysis revealing a strong linear relationship (RR2 = 0.99) between severity and relative sample density. Likewise, distortion due to slice selection errors showed a squared relationship (RR2 = 0.92) with sample density. Unique artefact features were identified surrounding honeycomb samples suggesting a complex relationship exists for larger unit cells. To demonstrate clinical utility, a honeycomb design was applied to a representative cranioplasty. Analysis revealed 10% artefact reduction compared to traditional solid material illustrating the feasibility of this approach. This study provides a basis to strategically design implants to reduce MRI artefacts and improve post-operative diagnosis capability. STATEMENT OF SIGNIFICANCE: MRI susceptibility artefacts surrounding metal implants present a clinical challenge for the diagnosis of post-operative complications relating to the implant itself or underlying anatomy. In this study for the first time we demonstrate that additive manufacturing may be exploited to create lattice structures that predictably reduce MRI image artefact severity surrounding titanium alloy implants. Specifically, a direct correlation of artefact severity, both total signal loss and distortion, with the relative material density of these functionalised materials has been demonstrated within clinically relevant MRI sequences. This approach opens the door for strategic implant design, utilising this structurally functionalised material, that may improve post-operative patient outcomes and compliments existing efforts in this area which focus on data acquisition and post-processing methods.

Analysis of growth and biofilm formation of bacterial pathogens on frequently used spinal implant materials.

STUDY DESIGN: A microscopy-based investigation of the permissive factors leading towards bacterial adherence on commonly utilized spinal implants. OBJECTIVE: The adherence and subsequent colonization and biofilm formation of bacteria on orthopaedic implants represents one of the most serious problems facing orthopaedic surgeons. Once a biofilm is formed, surgeons may have to resort to implant removal, a strategy that may cause substantial patient morbidity and lead to additional cost to the healthcare system. This problem has been further compounded by the rise of antibiotic-resistant strains of bacterial pathogens. In this study, two commonly encountered bacterial pathogens in surgical site infections (SSI) were characterized for adherence pattern, density, and propagation on five commonly used spinal implant materials via scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results show that bacterial adherence is largely dependent on the microtopographical features observed on the surface of the materials tested. METHODS: Five commonly utilized spinal implant materials were inoculated with two of the most common nosocomial pathogens and visualized via scanning electron microscopy and confocal laser scanning microscopy. RESULTS: Analysis of 90 spinal implant pieces showed that even though no material showed the ability to prevent adherence of both pathogens tested, the presence of surface imperfections and rougher microtopography was found to harbor the most bacterial presence. CONCLUSION: Our data suggests that implants materials with uniform surface and minimal imperfections may reduce the ability of bacterial to adhere to implants. LEVEL OF EVIDENCE: Level I evidence: "Investigation of a diagnostic test".

Microstructure and mechanical properties of additive manufactured porous Ti-33Nb-4Sn scaffolds for orthopaedic applications.

Customized porous titanium alloys have become the emerging materials for orthopaedic implant applications. In this work, diamond and rhombic dodecahedron porous Ti-33Nb-4Sn scaffolds were fabricated by selective laser melting (SLM). The phase, microstructure and defects characteristics were investigated systematically and correlated to the effects of pore structure, unit cell size and processing parameter on the mechanical properties of the scaffolds. Fine ß phase dendrites were obtained in Ti-33Nb-4Sn scaffolds due to the fast solidification velocity in SLM process. The compressive and bending strength of the scaffolds decrease with the decrease of strut size and diamond structures showed both higher compressive and bending strength than the dodecahedron structures. Diamond Ti-33Nb-4Sn scaffold with compressive strength of 76 MPa, bending strength of 127 MPa and elastic modulus of 2.3 GPa was achieved by SLM, revealing the potential of Ti-33Nb-4Sn scaffolds for applications on orthopaedic implant.

Plasma Electrolytic Oxidation of Titanium Implant Surfaces: Microgroove-Structures Improve Cellular Adhesion and Viability.

BACKGROUND/AIM: Plasma electrolytic oxidation (PEO) is an established electrochemical treatment technique that can be used for surface modifications of metal implants. In this study we to treated titanium implants with PEO, to examine the resulting microstructure and to characterize adhesion and viability of cells on the treated surfaces. Our aim was to identify an optimal surface-modification for titanium implants in order to improve soft-tissue integration. MATERIALS AND METHODS: Three surface-variants were generated on titanium alloy Ti6Al4V by PEO-treatment. The elemental composition and the microstructures of the surfaces were characterized using energy dispersive X-ray spectroscopy, scanning electron microscopy and profilometry. In vitro cytocompatibility of the surfaces was assessed by seeding L929 fibroblasts onto them and measuring the adhesion, viability and cytotoxicity of cells by means of live/dead staining, XTT assay and LDH assay. RESULTS: Electron microscopy and profilometry revealed that the PEO-surface variants differed largely in microstructure/topography, porosity and roughness from the untreated control material as well as from one another. Roughness was generally increased after PEO-treatment. In vitro, PEO-treatment led to improved cellular adhesion and viability of cells accompanied by decreased cytotoxicity. CONCLUSION: PEO-treatment provides a promising strategy to improve the integration of titanium implants with surrounding tissues.

Nanoskin® Subcutaneous Implant in Guinea Pigs.

PURPOSE: To evaluate the suitability of Nanoskin, a biomaterial derived from bacterial cellulose, as an alternate material for repairing the posterior lamellae of the eyelids. METHODS: Forty guinea pigs received a fragment of Nanoskin subcutaneously in the dorsal region. The animals received Nanoskin (group 1) or Nanoskin coated with a gelatin layer (group 2). The animals were observed daily for over 7, 30, 90, or 180 days with the subcutaneous implants in place. The animals were euthanized at a designated time and the Nanoskin was removed for histologic, morphometric, and transmission electron microscopy evaluation. RESULTS: The results were similar for both groups. The subcutaneously implanted Nanoskin resulted in good tissue integration, induced mild inflammation, and was surrounded by a delicate pseudocapsule. CONCLUSION: The good tissue integration of Nanoskin in study indicates that it may be a potential material for application as a substitute of posterior eyelid lamellar tissue. Further clinical studies are required to confirm the preliminary outcomes of this experimental study.

Osseointegration of titanium implants anodized with and without fluoride in the electrolyte: a study in rats / Osteo-integración de implantes de titanio anodizado con y sin agregado de fluoruro en el electrolito: estudio en la rata

Based on the hypothesis that fluoride acts as a bone anabolic agent, the aim of this study was to measure in rats the osseointegration of implants (grade II titanium wire, 1 mm diameter, 4 mm long) submitted to anodic oxidation in 2 M phosphoric acid solution (control implants) or b) in 2 M phosphoric acid solution plus 0.2 M NaF (F-modified implants). Chemical composition of the implants surface was assessed by energy-dispersive X-ray spectroscopy. The surface of F-modified implants contained a 2.57% fluorine in weight. Adult male Sprague Dawley rats (300-350 g body weight) received two implants (in the femur and in the tibia, close to the knee) in each hind limb. Control and F-modified implants were inserted in the left and right hind limbs, respectively. Three weeks after surgery, the animals were sacrificed. The undecalcified bones were embedded in methylmetacrylate. Sections were obtained to measure two histomorphometric magnitudes: bone-toimplant contact (BIC) and bone volume in a defined volume of tissue around the implant (BV/TV). BIC was significantly increased on F-modified implants with respect to their controls (57.2%±3.3%, vs. 47.9±3.4, p<0.05). BV/TV did not differ significantly between F-modified and control implants (24.5±2.2% vs. 22.9±1.4, p=0.30). Profiles of the average gray pixel levels of pseudo3D images showed a greater roughness of F-modified implants respect to their controls (p<0.05). The relative contributions of surface roughness and its fluorine content to the osseointegration process requires further research. (AU)

Con la hipótesis de que el ión fluoruro actúa como anabólico sobre las células óseas, el objetivo de este trabajo fue determinar el grado de osteo-integración (en la rata) de implantes (alambre de titanio II, 1 mm de diámetro, 4 mm de largo) anodizados en solución de ácido fosfórico 2 M + NaF 0,2 M (implantes-F) comparados con implantes controles, anodizados en solución de ácido fosfórico 2 M. La composición química de la superficie de los implantes fue evaluada mediante el espectro de dispersión de rayos X producidos durante la observación en el microscopio electrónico de barrido. La superficie de los implantes-F contiene 2.57% de flúor. Ratas macho Sprague-Dawley recibieron dos implantes (en el fémur y en tibia, próximos a la rodilla). Los implantes-F y controles se insertaron en las patas izquierda y derecha respectivamente. En los cortes de hueso sin decalcificación previa se midió el contacto hueso-implante (BIC) y volumen óseo en un volumen definido de tejido (BV/TV). BIC fue significativamente mayor con los Implantes-F respecto de los controles (57,2±3,3% vs. 47,9±3,4, p<0,05). BV/TV no exhibió diferencias significativas entre implantes-F y controles (24,5±2,2% vs. 22,9±1,4, p=0,30). Los perfiles de los niveles de grises de los imágenes pseudo3D de las superficies de los implantes pusieron en evidencia la mayor rugosidad de los implantes-F respecto de los controles (p<0,05). Las contribuciones relativas de la rugosidad y del flúor en el proceso de osteo-integración requieren investigación adicional. (AU)

Novel Bio-functional Magnesium Coating on Porous Ti6Al4V Orthopaedic Implants: In vitro and In vivo Study.

Titanium and its alloys with various porous structures are one of the most important metals used in orthopaedic implants due to favourable properties as replacement for hard tissues. However, surface modification is critical to improve the osteointegration of titanium and its alloys. In this study, a bioactive magnesium coating was successfully fabricated on porous Ti6Al4V by means of arc ion plating, which was proved with fine grain size and high film/substrate adhesion. The surface composition and morphology were characterized by X-ray diffraction and SEM equipped with energy dispersive spectroscopy. Furthermore, the in vitro study of cytotoxicity and proliferation of MC3T3-E1 cells showed that magnesium coated porous Ti6Al4V had suitable degradation and biocompatibility. Moreover, the in vivo studies including fluorescent labelling, micro-computed tomography analysis scan and Van-Gieson staining of histological sections indicated that magnesium coated porous Ti6Al4V could significantly promote bone regeneration in rabbit femoral condylar defects after implantation for 4 and 8 weeks, and has better osteogenesis and osteointegration than the bare porous Ti6Al4V. Therefore, it is expected that this bioactive magnesium coating on porous Ti6Al4V scaffolds with improved osteointegration and osteogenesis functions can be used for orthopedic applications.

Antibacterial effects of the povidone-iodine vacuum impregnation technique in expanded polytetrafluoroethylene augmentation rhinoplasty.

Expanded polytetrafluoroethylene (e-PTFE) is a popular graft material for augmentation rhinoplasty. Gore-Tex and Surgiform are two types of e-PTFE; Surgiform has thicker fibrils and is more compact than Gore-Tex. We conducted an ex vivo study to evaluate the ability of povidone-iodine (PVP-I) vacuum pretreatment to prevent infection with these two types of e-PTFE. Gore-Tex and Surgiform specimens were cut into 2-mm(3) pieces, which were separated into two groups. One group for each e-PTFE was disinfected with vacuum PVP-I impregnation and the other group was not disinfected. Using the pieces of implant material, swabs were obtained from the nasal cavities of 20 healthy adults, and the specimens were incubated on agar plates and viewed by scanning electron microscopy (SEM). We found that PVP-I treatment significantly reduced the bacterial colony counts in both the Gore-Tex and Surgiform groups. In the SEM images, bacterial colonies were observed both inside and outside the untreated Gore-Tex; on the untreated Surgiform, they were found primarily on the surface. Few bacteria were detected in the PVP-I-treated Gore-Tex and Surgiform groups. Our findings suggest that PVP-I pretreatment can reduce the risk of infection associated with e-PTFE.

Toward smart implant synthesis: bonding bioceramics of different resorbability to match bone growth rates.

Craniofacial reconstructive surgery requires a bioactive bone implant capable to provide a gradual resorbability and to adjust to the kinetics of new bone formation during healing. Biomaterials made of calcium phosphate or bioactive glasses are currently available, mainly as bone defect fillers, but it is still required a versatile processing technique to fabricate composition-gradient bioceramics for application as controlled resorption implants. Here it is reported the application of rapid prototyping based on laser cladding to produce three-dimensional bioceramic implants comprising of a calcium phosphate inner core, with moderate in vitro degradation at physiological pH, surrounded by a bioactive glass outer layer of higher degradability. Each component of the implant is validated in terms of chemical and physical properties, and absence of toxicity. Pre-osteoblastic cell adhesion and proliferation assays reveal the adherence and growth of new bone cells on the material. This technique affords implants with gradual-resorbability for restoration of low-load-bearing bone.

Enhanced blood compatibility of metallocene polyethylene subjected to hydrochloric acid treatment for cardiovascular implants.

Blood compatibility of metallocene polyethylene (mPE) was investigated after modifying the surface using hydrochloric acid. Contact angle of the mPE exposed to HCl poses a decrease in its value which indicates increasing wettability and better blood compatibility. Surface of mPE analyzed by using FTIR revealed no significant changes in its functional groups after treatment. Furthermore, scanning electron microscope images supported the increasing wettability through the modifications like pit formations and etching on the acid rendered surface. To evaluate the effect of acid treatment on the coagulation cascade, prothrombin time (PT) and activated partial thromboplastin time (APTT) were measured. Both PT and APTT were delayed significantly (P < 0.05) after 60 min exposure implying improved blood compatibility of the surfaces. Hemolysis assay of the treated surface showed a remarkable decrease in the percentage of lysis of red blood cells when compared with untreated surface. Moreover, platelet adhesion assay demonstrated that HCl exposed surfaces deter the attachment of platelets and thereby reduce the chances of activation of blood coagulation cascade. These results confirmed the enhanced blood compatibility of mPE after HCl exposure which can be utilized for cardiovascular implants like artificial vascular prostheses, implants, and various blood contacting devices.

Effects of dextrose and lipopolysaccharide on the corrosion behavior of a Ti-6Al-4V alloy with a smooth surface or treated with double-acid-etching.

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (α = 0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2 = 0.726, p<0.0001 for the smooth surface; R2 = 0.405, p = 0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections.

Plug surface defects as a late complication of silicone punctal plugs.

PURPOSE: To report 3 cases of punctal plug surface defects as a cause of irritation complicating punctal plug therapy. METHODS: Interventional case series and scanning electron microscopy (SEM) of punctal plugs. RESULTS: Three patients were found to have punctal plug surface defects and local irritation of conjunctiva and inferonasal cornea 9, 40, and 69 months after placement of AquaFlo silicone punctal plugs for the treatment of dry eyes. SEM of the explanted plugs confirmed a defective collarette surface. In addition, unused AquaFlo plugs from different lots examined by SEM showed a rough irregular collarette surface that was not seen in unused plugs of Parasol silicone punctal plugs. DISCUSSION: AquaFlo punctal plugs inherently have surface irregularities when compared with similar plug brands, which we suggest may predispose to plug breakdown over time, leading to mechanical irritation of the adjacent conjunctiva and cornea. This report highlights the local complications by AquaFlo punctal plugs associated with plug surface defects as a complication of punctal plug therapy.

Aneurysm embolization with biologically active coils: an animal study.

OBJECTIVES: Cellular adhesion on the surface of Guglielmi detachable coils (GDC) promotes accelerated occlusion of aneurysms. We hypothesized that coils coated with transforming growth factor beta (TGF-beta) and vascular endothelial growth factor (VEGF) will promote clot organization and endothelial or cellular proliferation to facilitate closure of large experimental aneurysms relative to uncoated GDC coils. METHODS: GDC were inserted either uncoated, coated with albumin, coated with TGF-beta (500 µg/ml) or with VEGF (500 µg/ml) into the ligated common carotid artery of adult male wistar rats for 14 days. Twenty-four adult male Wistar rats (280-300 g) were divided into four groups (n = 6 per group). Subjects were killed 2 weeks after implantation and common carotid artery (CCA) segments were harvested and coils were removed. Arterial tissue was evaluated histopathologically. RESULTS: Significant differences in the proportion of aneurysm luminal area (mm(2)) was shown among Group i (0·22±0·14 SD) and Group ii (0·16±0·8 SD) compared to Group iii (0·04±0·03 SD; P<0·05), and Group iv (0·02±0·02 SD; P<0·05) analyzed 2 weeks postoperatively. Light microscopy showed well organized fibrous tissue formation of epithelial cells and intimal hyperplasia around the coils when using the coated GDC's (Group iii and Group iv). CONCLUSION: The result of this study suggests that the coated GDC with TGF-beta or VEGF appears beneficial in promoting endothelization, clot organization, and cellular tissue integration of the coils.

Three-dimensional structure of laser-modified Ti6Al4V and bone interface revealed with STEM tomography.

The early interaction between an implant's surface and bone is a leading factor for implant success, where multiple surface properties contribute to improved bone anchorage. An important parameter is surface topography, both on the micron and nanoscale. Laser-modification has been performed in the thread valleys of Ti6Al4V screws to alter their surface chemistry and topography to form a nanostructured surface titanium-dioxide. Implants were placed in the rabbit tibia, removed with surrounding bone after 8 weeks, fixated, dried and resin embedded. Focused ion beam milling (FIB) was used to prepare specimens from the resin blocks for transmission electron microscopy (TEM). Z-contrast electron tomography offered the possibility to explore the interfacial structure with high-resolution in three-dimensions. With this technique, collagen fibers of the surrounding bone appear to have been laid down parallel to the implant surface. Accordingly, visualization of the laser-modified interface with nanoscale three-dimensional resolution, as offered by Z-contrast electron tomography, gives new insights into bone bonding mechanisms between roughened titanium-dioxide surfaces and bone.

Evaluation of biological properties of electron beam melted Ti6Al4V implant with biomimetic coating in vitro and in vivo.

BACKGROUND: High strength porous titanium implants are widely used for the reconstruction of craniofacial defects because of their similar mechanical properties to those of bone. The recent introduction of electron beam melting (EBM) technique allows a direct digitally enabled fabrication of patient specific porous titanium implants, whereas both their in vitro and in vivo biological performance need further investigation. METHODS: In the present study, we fabricated porous Ti6Al4V implants with controlled porous structure by EBM process, analyzed their mechanical properties, and conducted the surface modification with biomimetic approach. The bioactivities of EBM porous titanium in vitro and in vivo were evaluated between implants with and without biomimetic apatite coating. RESULTS: The physical property of the porous implants, containing the compressive strength being 163 - 286 MPa and the Young's modulus being 14.5-38.5 GPa, is similar to cortical bone. The in vitro culture of osteoblasts on the porous Ti6Al4V implants has shown a favorable circumstance for cell attachment and proliferation as well as cell morphology and spreading, which were comparable with the implants coating with bone-like apatite. In vivo, histological analysis has obtained a rapid ingrowth of bone tissue from calvarial margins toward the center of bone defect in 12 weeks. We observed similar increasing rate of bone ingrowth and percentage of bone formation within coated and uncoated implants, all of which achieved a successful bridging of the defect in 12 weeks after the implantation. CONCLUSIONS: This study demonstrated that the EBM porous Ti6Al4V implant not only reduced the stress-shielding but also exerted appropriate osteoconductive properties, as well as the apatite coated group. The results opened up the possibility of using purely porous titanium alloy scaffolds to reconstruct specific bone defects in the maxillofacial and orthopedic fields.

Concentración de metales séricos (titanio, cromo y cobalto) en el seguimiento de las artroplastias totales de cadera / Serum metal (titanium, chromium and cobalt) concentrations in the follow-up of total hip arthroplasty

Objetivo: Analizar la degradación de los productos metálicos que constituyen las aleaciones de las prótesis de cadera. Pacientes y método: Se midió, mediante absorción atómica, el titanio, el cromo y el cobalto en la sangre de 58 pacientes con prótesis totales de cadera, compuestas por aleaciones de cromo y cobalto y de titanio, con o sin cementar. Se analizó la evolución de las concentraciones séricas preoperatorias, a los seis y a los 12 meses. Resultados: Encontramos una elevación significativa tras el inicio de la movilización de la articulación, pero sin afectación clínica. Los percentiles 95 de la distribución de concentraciones fueron para el Ti 27 mg/L, Cr 1 mg/L y Co 1,7 mg/L. Conclusión: La elevación de estas concentraciones podría ser indicativa de mal funcionamiento del implante o de desgaste excesivo que podría conducir a toxicidades locales o remotas (AU)

Objective: To analyze the degradation of the metal products contained in hip prosthesis alloys. Patients and method: Atomic absorption measurements were made of the titanium, chromium and cobalt concentrations in the blood of 58 patients with total hip replacement implants made of titanium, chromium and cobalt alloys with or without cementing. The evolution of the serum metal concentrations was assessed based on measurements obtained preoperatively and 6 and 12 months after surgery. Results: A significant increase in serum levels was noted after the start of joint mobilization, though without clinical repercussions. The percentile 95 values of the metal concentration distributions were 27 mg/l for titanium, 1 mg/l in the case of chromium, and 1.7 mg/l for cobalt. Conclusion: The rise in serum metal concentrations could be indicative of poor implant function or excessive wear that in turn could lead to local or disseminated toxicity (AU)

In vitro and in vivo characterization of silk fibroin/gelatin composite scaffolds for liver tissue engineering.

OBJECTIVE: To investigate the cytotoxicity of silk fibroin/gelatin (SF/G) composite scaffolds in vitro as well as their biocompatibility and degradation in vivo. METHODS: The proliferation and relative growth rate of human hepatic QZG cells grown on different blends of two-dimensional (2-D) SF/G scaffolds were assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Flow cytometry was used to evaluate apoptotic rate of QZG cells on different blends of 2-D SF/G scaffolds. The effect of silk protein materials on cell growth was observed by scanning electron microscopy. Three-dimensional (3-D) SF/G scaffolds of three different ratios (diameter 10 mm, thickness 1 mm) were implanted into subcutaneous pockets on male Sprague-Dawley (SD) rats. On the 7th, 14th and 30th day post-implantation, the rats were sacrificed. The scaffold area including the surrounding tissues was retrieved. Hematoxylin and eosin staining was performed for observation under a light microscope. RESULTS: Significant cell attachment and proliferation on the SF/G scaffolds were observed. As the increased gelatin concentration, SF/G scaffolds became more amenable to cell adhesion. After the subcutaneous implantation of the SF/G scaffolds in SD rats, immunological rejection tests showed only slight inflammation, measured by the presence of inflamed cells on day 7 and 14. By day 30, each scaffold had been completely infiltrated and organized by fibroblasts and inflamed cells. The greater the gelatin concentration in the scaffold, the faster the degradation rate. CONCLUSION: Composite SF/G scaffolds are a promising candidate matrix for implantable bio-artificial livers.

Preliminary study of the biomechanical behavior and physical characteristics of tantalum (Ta)-coated prostheses.

BACKGROUND: Use of Ta biomaterials in medicine started in the middle of the last century. The good biocompatibility and chemical stability, and the unique physical characteristics of Ta metal have resulted in many possible developments of Ta biomaterials. METHODS: In this study, histopathological observation, histomorphometric analysis, scanning electron microscope (SEM) observation, energy-dispersive X-ray spectroscopy (EDX) analysis, biomechanical testing, and examination of the coating's mechanical strength have been used to evaluate the value of clinical application of Ta-coated prostheses prepared by a plasma-spraying process. RESULTS: Histopathological observation has demonstrated that the periprosthetic new bone tissues tightly and stably adhere to the Ta coating after the implantation, with no signs of loosening. Early after implantation, there is no significant difference in periprosthetic bone volume and ultimate shear strength between Ta-coated and Ti-coated prostheses (P > 0.05). EDX analysis suggests that the ultimate shear stress does not damage Ta coating. Mechanical strength testing shows that the adhesive strength and Vicker's surface hardness (HV) of the Ta coating are significantly higher than those of the Ti coating (P < 0.01). CONCLUSIONS: Ta coating has good stability and bone biocompatibility; the extraordinary physical characteristics of Ta coating have great significance in maintaining prosthetic stability and surface porosity after implantation.

Pt-Al2O3 interfacial bonding in implantable hermetic feedthroughs: morphology and orientation.

The present work examines the chemistry, microstructure, and crystallography of a Pt-Al(2)O(3) joint used in implantable hermetic feedthrough designs in neural prostheses. Pt was joined to Al(2)O(3) by passing Pt pins through green Al(2)O(3) disks and then sintering in air. This created a Pt-Al(2)O(3) joint that was prepared for the current investigation by gross sectioning and then polishing and sectioning into slices using focused ion beam milling. The slices were examined by scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. Two types of interfaces in the sintered material were identified: Vitreous-bonded Pt-glass-Al(2)O(3) and direct-bonded Pt-Al(2)O(3). In the case of the former, glass formation owing to the presence of glass-forming additives (to enhance densification and suppress grain growth) and consequent wetting of both the Pt and Al(2)O(3) facilitated interfacial bonding. In the case of the latter, the interfacial planes were (002)(Pt) // (022)Al(2)O(3) [rhombohedral] or (002)(Pt) // (022 2)Al(2)O(3) [hexagonal]. The lattice mismatch was calculated to be 11% (based on the calculated d spacings) or 15% (based on the literature d spacings). Both of these suggest the establishment of semicoherent interfaces.

Histological study of graft failure in AlphaCor transplantation.

To report clinical and histopathologic findings in a case of a failed AlphaCor artificial cornea explanted due to corneal stromal melting. We describe the case of a 77-year-old man who received multiple penetrating keratoplasties (PKPs) and subsequent placement of an AlphaCor artificial cornea. Examination showed total corneal infiltration as well as an AlphaCor that was partially dehisced from the host cornea. After explantation, the implant and adjacent host tissue underwent hematoxylin and eosin staining and high-resolution scanning electron microscopy (HR-SEM). Histopathologic analysis of the specimens revealed infiltration of the skirt pores by reactive corneal fibroblasts. Although the AlphaCor implant is an established method of treating multiple failed PKPs, in this case, HR-SEM imaging strongly suggests that the strength of the interface between the implant and corneal tissue is highly dependent on collagen deposition between the pores found in the implant skirt. Collagen deposition then increases the mechanical strength of the cornea-skirt interface.