Te Chuan Lee

Biomimetic Bone-Like Apatite Coating on Anodised Titanium in Simulated Body Fluid under UV Irradiation

Low temperature deposition techniques of bioceramics coatings are now being researched and developed to avoid deficiencies inherent in high temperature techniques. Biomimetic coatings is a solution-based method conducted at ambient temperature to deposit bioactive coatings on the surface. The current study aims to investigate the effect of ultraviolet (UV) irradiation on the coating of bone-like apatite on the anodised surface. High purity titanium foils were anodised with an applied voltage of 350 V, current density of 70 mA.cm-2 in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate (CA) for 10 min. After anodic oxidation, UV light treatment was conducted in pH-adjusted distilled water for 12 hours with ultraviolet light A (UVA) irradiation. Subsequently, the UV-treated anodised titanium foils were soaked in SBF for 7 days with/without UVA irradiation. After SBF immersion for 7 days, anodised titanium with combination of UV light treatment and UV irradiation during in vitro testing was fully covered by highly crystalline bone-like apatite at maximal thickness of 2.8 μm. This occurred mainly due to the formation of large amounts of Ti-OH groups which act as nucleation sites for bone-like apatite. This study also revealed that UV irradiation during in vitro testing is superior in promoting growth of bone-like apatite compared to UV light treatment. The suggested mechanism for bone-like apatite formation on anodised titanium under different UV irradiation conditions is illustrated in this article. The findings of this study indicated that biomimetic bone-like apatite coating with assistance of UV irradiation is an effective method in accelerating the formation of bone-like apatite.

Effect of Bath Temperature on Surface Properties of Anodised Titanium for Biomedical Application

Anodic oxidation is an electrochemical method to deposit ceramic coatings on the metals substrate to improve the bioactivity. This study aims to investigate the effect of bath temperature on the surface properties of anodised titanium. High-purity titanium foil was modified by anodising in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The experiments were carried out at 350 V, 30 mA.cm-2 for 10 minutes at different bath temperature (4-100 °C). Field emission scanning electron microscopy (FESEM), glancing angle X-ray diffractometer (GAXRD) and goniometer were used to characterise the surface morphology, mineralogy and wettability of anodised titanium, respectively. The results showed that porosity and crystallinity of surface decreased as increasing of bath temperature. Interestedly, the α-tricalcium phosphate (α-TCP) was deposited on the samples which anodisation at higher bath temperature (≥ 60 °C) and resulted high hydrophilicity behaviour even the surface was found relatively smooth.

Precipitation of Hydroxyapatite on Pure Titanium Substrate via Single Step Anodic Oxidation

Anodic oxidation is an electrochemical method that deposits ceramic coatings on the metal substrates to improve the bioactivity of implant. In this study, a novel approach was proposed to precipitate hydroxyapatite (HAP) directly on the surface of pure titanium through anodic oxidation approach. As part of the proposed approach, a new formulation of electrolyte was introduced, which consists of 0.04 M β-glycerophosphate (β-GP), 0.4 M calcium acetate (CA) and 1.0 M sulphuric acid (H2SO4). The approach herein only requires a single step to precipitate the HAP directly on the surface of titanium through anodisation process within the electrolyte. High purity titanium foils were anodised in 0.04 M β-GP + 0.4 M CA + 1.0 M H2SO4 at 350 V and 70 mA.cm-2 for 10 minutes at varying fractions of mixture volumes of H2SO4 (0-100 vol%). The surface properties of anodised titanium were characterised by using several methods, namely the field emission scanning electron microscopy (FESEM), glancing angle X-ray diffractometer (GAXRD) and goniometer. The outcome of the characterisation showed that the needle-like HAP was precipitated on the titanium, whereby anodising in electrolyte contains 12.5 vol% H2SO4. Combinations of anatase, rutile, titanium, tricalcium phosphate (Ca3O8P2) and calcium diphosphate (Ca2O7P2) elements were detected within the anodised titanium, whereby the anodising in electrolyte contains 50 vol% H2SO4.

Mechanism of Bone like Apatite Formation on Anodised Titanium under UV Irradiation

Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It had been widely used to deposit the ceramic coatings on the metals surface. UV light was used to accelerate the bone-like apatite formation on the anodised titanium in this study. The processing was composed of two steps which were UV light treatment after anodic oxidation, and UV light illumination during simulated body fluid (SBF). This study aims to study the mechanism of bone-like apatite formation on the surface of anodised titanium under UV irradiation. High purity titanium foils were anodised at 350 V, 70 mA.cm in electrolytic solution containing glycerophosphate disodium salt pentahydrate (βGP) and calcium acetate monohydrate (CA) for 10 minutes. UV light treatment was conducted in pH-adjusted distilled water (pH 1) for 12 hours. Next, SBF was carried out by illuminating with UV lamp for 1 week. Anodised titanium foils were characterised by using field emission scanning electron microscopy (FESEM) and fourier transform infrared spectroscopy (FTIR). The results showed that bone-like apatite started to form at concave surface due to the presence of nucleation site. The surface of anodised titanium was fully covered by bone-like apatite after soaking in SBF for 4 days. Denser bone-like apatite was formed after 7 days immersion in SBF. The mechanism of the growth of bone-like apatite was illustrated. The FTIR results showed that carbonated bone-like apatite was formed on the surface on anodised titanium. The result indicated that the anodised titanium in mixture of β-GP + CA possess excellent apatite-forming ability under UV irradiation. Keywords— anodic oxidation, titanium, titanium dioxide, UV irradiation, simulated body fluid, bone-like apatite.

Effect of Ultrasonic Amplitude on Surface Properties of Anodised Titanium for Biomedical Application

Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It is a simple and low cost method to produce bioactive material. This work describes the effect of ultrasonic amplitude on the surface properties of anodised titanium. Specifically, high purity titanium foils were anodised in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate monohydrate (CA) at 350 V and 70 mA.cm-2 for 10 minutes. The ultrasonic amplitude was varied from 20-60 μm. Next, field emission scanning electron microscopy (FESEM) glancing angle X-ray diffractometer (GAXRD) and atomic force microscopy (AFM) were used to characterise the anodised titanium. The results showed that application of sonication is able to remove the entrapped bubbles on the anode surface and enhance the oxidation process. The pores size and surface roughness were increased as increasing of ultrasonic amplitude. At ultrasonic amplitude ≥ 50 μm, rutile TiO2 was formed on the surface of oxide layer. It was found that the sonication is a simple method to improve the surface properties of anodised titanium for implant applications.

Preparation of Bioactive Titanium Film via Anodic Oxidation in Agitation Condition

Anodic oxidation is a well-established surface modification method which combines electric field driven metal and oxygen ion diffusion to produce protective oxide layer on metals. This method has been widely used to modify the surface properties of titanium and its alloy. This present study aims to investigate the effect of agitation speed on the surface properties of anodised titanium. At first, the high purity titanium foils were anodised in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate monohydrate (CA) at 350 V and 30 mA.cm-2 for 10 minutes at different agitations speed (300 rpm - 1500 rpm). Next, surface properties of anodised titanium were characterised by digital single-lens reflex camera (DSLR camera), field emission scanning electron microscopy (FESEM) and glancing angle X-ray diffractometer (GAXRD). At lower agitation speed (≤ 900 rpm), surface of anodised titanium covered by small donut-shaped pores. With increasing of agitation speed (≥ 1100 rpm), the oxide layer became more porous and covered by larger donut-shaped pores. Rutile TiO2 peaks were detected at agitation speed more than 1100 rpm. Agitation condition is believed to be an effective method to enhance the surface properties of anodised titanium for biomedical applications.

UV induced Precipitation of Bone like Apatite on Anodised Titanium in Simulated Body Fluid

Anodic oxidation is an electrochemical method to deposit ceramic coatings on the metals substrate. It has been widely used to modify the surface properties of titanium in order to improve the bioactivity. Recently, photocatalytic activity of biomaterials has attracted great deal of attention. This study aims to investigate the effect of UV irradiation on the precipitation of bone-like apatite in simulated body fluid (SBF). Specifically, the high purity titanium foils were anodised at various voltage (50V-350V) in mixture of βglycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) for 10 minutes. Next, the anodised titanium foils were soaking in SBF for 7 days by illuminating with UVC light (peak wavelength of 254 nm). Field emission scanning electron microscopy (FESEM) and glancing angle X-ray diffractometer (GAXRD) were used to characterise the surface morphology and crystallinity of anodised titanium before and after soaking in SBF. After 7 days, bone-like apatite was covered on the surface of anodised titanium. Interestedly, smooth surface of anodised titanium also covered by bone-like apatite which contradict with the previous findings that concluded smooth surface lack of nucleation site for the growth of bone-like apatite. This finding indicated that •OH groups produced during photocatalysis were the key factor to induce the precipitation of bone-like apatite. The result also showed that novel bioactive material is able to prepare by photocatalysis of anodised titanium in SBF. Keywords— anodic oxidation, titanium, titanium dioxide, UV irradiation, simulated body fluid, bone-like apatite.