Sharif Digital Repository

Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication... 

Hydroxyapatite-Graphene Nanocomposite coatings were formed on Ti-6Al-4V alloy by Plasma electrolytic oxidation. PEO electrolyte contains calcium acetate and calcium glycerophosphate. The effect of adding graphene to PEO electrolyte on the corrosion, mechanical, and biocompatibility properties of the coating investigated. Before adding graphene to the electrolyte, working parameters such as voltage, current density, process time were optimized using scanning electron microscopy (SEM), potentiodynamic polarization test, and thickness measurement. Examination of the coating morphology showed that due to thermal stresses, surface cracks formed at Voltages above 350 V. The results of the... 

At the first stage, chitosan-hydroxyapatite-multiwalled carbon nanotube (CH-HA-MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on Ti6Al4V and 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. At the second stage, effect of pH and MWCNT content of the suspension on corrosion behavior and mechanism of deposition were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)... 

The present study is work on fabrication and characterization of a chitosan/ gelatin/ Mg substituted hydroxyapatite nano composite scaffold for bone tissue engineering. At the first step pure and Mg-substituted hydroxyapatite (HA) (Ca10-xMgx(PO4) 6OH2) nano-hexagonal rods with 14–45 nmdiameter.for this, calcium nitrate, magnesium phosphate hydrate and potassium dihydrogenphosphate were used as precursors for Ca, Mg, and P, respectively. Calculated amounts of magnesium ions (Mg+2) especially from 0 to 8% (molar ratio) were incorporated as substituted into the calcium sol solution. Deionized water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH= 9.... 

Plasma electrolyte oxidation process is one of the surface coating methods which is recommended to use as a surface preparation before applying the final coating on magnesium alloys due to its unique properties such as excellent adhesion.The aim of this study was to create an oxide layer on the AZ91 substrate and after optimizing the PEO coating conditions and choosing the best coating in order to increase adhesion and corrosion resistance, the composite coating of graphene oxide, hydroxyapatite and chitosan was applied by electrophoretic method. After studying the morphology of PEO oxide coating at current densities of 0.25, 0.35, 0.4, 0.5 and 0.6 amp/cm2 during times of 5 and 8 minutes, it... 

Bone scaffolds are used to regenerate bone tissue and accelerate bone healing, for this purpose, an attempt was made to prepare biocompatible, biodegradable, low toxicity and non-allergenic scaffolds to help increase osteogenesis and improve bone infections. A porous multi-component composite of chitosan, hydroxyapatite, graphene oxide functionalized with silver was made to make the desired scaffolds. At first, graphene oxide was functionalized by silver ions using silver nitrate. The structure of silver graphene oxide nanocomposite was confirmed by scanning electron microscope (SEM), Fourier infrared spectroscopy (FT-IR), and ultraviolet (UV-Visible) spectroscopy. In the next step, a... 

Zirconia toughened alumina (ZTA) Nanocomposites were prepared using nano sized Zirconia (ZrO2) powders doped with 3% mol of yttria (Y2O3) nanopowders and the sintering behavior at different temperature (1450 °C, 1550 °C and 1650 °C) were studied. The ZTA composite with different amount of partially stabilized Zirconia (PSZ)(5, 10, 15 and 20% mol) were prepared via axial pressing and then sintered to achieve maximum densification. After that phase changes of the samples were monitored. SEM was used for microstructural study and hardness and fracture toughness were determined by means of Vickers indentation. X-ray diffraction pattern showed that at constant composition, tetragonal zirconia... 

Synthetic polymers have a high capacity to provide and manufacture the pieces used in tissue engineering. However, optimizing the biocompatibility, bioresorbableility and mechanical properties simultaneous with processability of material is complicated and requires a lot of effort at designing different parts of the system. On the other hand, due to existence of secondary bonds (such as metal-ligand coordination or hydrogen bond) supramolecular polymers are able to respond to some stimuli such as temperature, pH, or pressure, which is important in terms of dynamic nature of interaction between the living cells and the external matrix of cell. Recently there have been extensive studies on... 

Hydroxyapatite is the most substantial inorganic constituent of bone tissue which displays splendid biocompability and bioactivity. Nevertheless, its mechanical properties is not utmost appropriate for a bone substitutes. Therefore, it is used to improve the mechanical properties of polymer matrix composite scaffolds. In the present work polycaprolactone as a polymeric matrix was employed to fabricate hydroxyapatite-polycaprolactone biocomposite scaffolds via in situ route. Solvothermal method was employed to synthesize in situ hydroxyapatite in polymer matrix. Porous scaffolds were fabricated via freeze-drying/porogen leaching. Physical, mechanical (compressive module and compressive... 

This work describes the effect of hydroxyapatite with different morphology including nanorods and whisker on the properties of hydroxyapatite/polycaprolactone (HA/PCL) composite. Biodegradable polymer/Hydroxyapatite (HA) composites with the morphology of nanorods and whisker of (HA) as bone replacement scaffolds are synthesized by sol-gel and hydrothermal methods, respectively with a Ca/P ratio of 1.67 and 20:80 (HA/PCL).The crystallization behavior and porosity of HA/PCL composite are studied by scanning electron microscope and X-Ray diffraction. The response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic... 

Hydroxyapatite (HA) is the most substantial mineral constituent of a bone which displays splendid biocompatibility and bioactivity properties. Nevertheless, its mechanical property is not utmost appropriate for a bone substitution. Therefore, a composite consist of HA and a biodegradable polymer is usually prepared to generate an apt bone scaffold. In the present work polycaprolactone (PCL), a newly remarkable biocompatible and biodegradable polymer, was employed as a matrix and hydroxyapatite nanoparticles and nanorods were used as a reinforcement element of the composite. HA/PCL nanocomposites were synthesized by three new in-situ sol-gel processes using a diverse range of phosphorus and... 

In this study effect of various mullite contents, as reinforcement phase, on phase combination, fracture surface and mechanical propertiese of hydroxyapatite- mullite composite has been investigated.
The used hydroxyapatite powder was synthesized through acid- base route and further calcination. XRD results demonstrated partially decomposition of HA in to β- TCP and CaO during the calcination. SEM image of the prepared HA powder showed that they were spherical and agglomarated.
The mixed HA with various amounts of the ball- milled mullite (10- 40 wt%)were pressed and sintered at 1350°C for 2h. Dominant phase in all composite samplese after sintering was Ca9Al(PO4)7.
Phase... 

With the increase in the average age of the world's population, osteoporosis is a worldwide incidence. This disease, along with natural disasters, are important factors in the occurrence of fractures in various bones of the body. One of the methods for solving this problem and replacing with broken body bones is the use of metal implants with hydroxyapatite-based coatings. One of the common problems with using implants in the body is the infection in the adjacent parts of the implant. To overcome this problem, several studies have been carried out on the use of hydroxyapatite coatings with metal ions or antibacterial oxide compounds. In the present study, the influence of factors such as the... 

The aim of this project is to load analgesic drug; Paracetamol on dental implant. The implant is titanium alloy (Ti-6Al-4V). There are two kinds of samples of anodized and HA coated onto anodized. They are in the shape of the sheets in this study. The electrodeposition and anodization carried out in order to treat the two samples. Nanotubes were formed during anodic oxidation of the samples in the 1M Ammonium sulfate (NH₄)₂SO4 and 5wt% Ammonium fluoride NH4F electrolyte. They are expected to play role of carrier for the model drug; paracetamol. The results showed that HA anodized Ti-6-4 has the ability to hold higher amounts of drug and also can keep the drug for a longer time than the... 

Metallic implants are useful in dental and orthopedic applications. Bio coating is necessary to improve bio-compatibility and bio-activation of metallic implants. For this goal, HA is the most important material. In this research, the goal is to improve bio-compatibility of St. St 316 by coating HA, HA-ZrO2, HA-TiO2, HA-ZrO2-TiO2 using combination of electrodeposition and electrophoretic methods. To form HA, calcium and phosphor salt solution was used then ZrO2- TiO2 nanoparticles was added to solution. In order to analyst the coatings different tests were done. Thickness analysis, XRD, FT-IR, FE-SEM and EDS, bonding Strength, Polarization test, bio-compatibility and surface roughness... 

In this project, a ceramic biocompatible coating was applied on Titanium which is included Hydroxyapatite by AC Plasma Electrolyte Oxidation method. First, coating was performed in 5 different solutions and various duration in 500mA/Cm2 as a current density. Then, by microscopic and macroscopic images and size of porosity and also thickness of coat, 3 solutions were chosen for adding nanoparticles: Solution 1 which includes NaH2PO4 and Ca(CH3COO)2 , Solution 3 which includes Ca(CH3COO)2 and Na-Beta G and Solution 4 which includes Ca(H2PO4)2, HMP, NA2(EDTA) and Ca(CH3COO)2 . Also the time 10 minutes was chose as a appropriate time. The average of the porosities size in solution 1 was about... 

In this study, biocompatible ceramic coating, containing hydroxyapatite particles (HA), was successfully created by AC anodizing, on the surface of commercially pure titanium grades 2. Coating process basically consisted of three methods. In Method 1, samples were anodized in a salty electrolyte containing calcium – phosphate base and in method 2 samples were anodized as initial process, following cathodic polarisation deposition of HA particles. Finally in method 3, samples were anodized in an electrolyte containing of HA particles suspension.Parameters such as current density and time of anodizing process, in first procedure, and time of cathodic deposition process in second procedure, and... 

There are many techniques that have been used to create hydroxyapatite nanoparticles coating on nanotubes. Electrophoretic deposition (EPD) is one of the methods that has advantages of short formation time, needs simple apparatus, little restriction of the shape of substrate, no requirement for binder burnout as the green coating contains few or no organics. In the research, first, titanium dioxide nanotubes were fabricated by anodic oxidation. Anodizing voltage effect on the morphology of nanotubes was evaluated. SEM images was shown that in the anodizing voltage 20V, nanotubes were the most regular. Then, Hydroxyapatite nanoparticles has been deposited onto nanotublar TiO2 by... 

Hydroxyapatite (HA) is an attractive biomaterial due to its close chemical composition to bone and teeth. However, HA is brittle and has low strength under bearing loads, resulting in limition for orthopedic and dental applications. Two creative approaches have been developed to overcome this problem, using bioactive HA as coatings on metallic implants or as ceramic/metal composites. Carbon nanotubes (CNT) possess excellent mechanical properties to play the role as reinforcement for imparting strength and toughness to brittle hydroxyapatite (HA) bioceramic coating. Moreover, The addition of TiO2 to HA coatings has attracted considerable attention, since TiO2 is capable of increasing the... 

In the present study, the acrylated polyurethane/nanohydroxyapatite (APU/n-HAp) nanocomposites were fabricated for use in bone tissue regeneration. The APU was synthesized based on poly(ε-caprolactone) diol (PCL), aliphatic 1,6- hexamethylene diisocyanate (HDI) and hydroxyethyl methyl acrylate (HEMA). The effect of HAp nanoparticles on the physicochemical properties of APU was evaluated. The APU/n-HAp nanocomposites were characterized using X-ray diffraction (XRD), dynamic mechanical thermal analyses (DMTA), scanning electron microscopy (SEM) and mechanical tests including tensile strength and elongation at break. The increase in physical properties achieved by incorporation of n-HAp...