Biomedical subjects

Chuanxian Ding

Publications and source records attributed to Chuanxian Ding.

15 recordsLinked to original sources

PubMed2006

Hydrogen plasma surface activation of silicon for biomedical applications.

Silicon has gradually been recognized to be an essential trace element in the normal metabolism of higher animals, and the role of silicon in the human body has aroused interests in the biomedical community. In fact, the interactions between silicon-based devices and the human body such as biosensors and microelectromechanical systems (MEMS) often suffer from poor biocompatibility. In this work, hydrogen plasma immersion ion implantation (H-PIII) is conducted to improve the bioactivity or bone conductivity of silicon. In order to investigate the formation mechanism of bone-like apatite on the surface of the hydrogen implanted silicon wafer, two comparative experiments, hydrogenation and argon bombardment, are performed. The H-PIII sample exhibits an amorphous surface consisting of Si-H bonds. After immersion in simulated body fluids, a negatively charged surface containing the functional group ([triple bond]Si-O-) is produced and bone-like apatite is observed to nucleate and grow on the surface. The surface of the H-PIII silicon wafer favors the adhesion and growth of osteoblast cells and good cytocompatibility may be inferred.

Biomedical Engineering↗

PubMed2006

Bioactivity and cytocompatibility of zirconia (ZrO(2)) films fabricated by cathodic arc deposition.

Zirconium oxide thin films were fabricated on silicon wafers using a filtered cathodic arc system in concert with oxygen plasma. The structure and phase composition of the zirconium oxide thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). The bioactivity was assessed by investigating the formation of apatite on the film surface after soaking in simulated body fluids. Bone marrow mesenchymal stem cells (BMMSC) were used to further evaluate the cytocompatibility of the materials. The results indicate that the films are composed of stoichiometric ZrO(2) and the composition is quite uniform throughout the thickness. Bone-like apatite can be formed on the surface of the ZrO(2) thin film in our SBF immersion experiments, suggesting that the surface is bioactive. The outermost layer of the ZrO(2) thin film comprises nano-sized particles that can be identified by AFM images taken on the thin film surface and TEM micrographs obtained from the interface between the ZrO(2) thin film and apatite layer. The nanostructured surface is believed to be the key factor that apatite is induced to precipitate on the surface. Bone marrow mesenchymal stem cells are observed to grow and proliferate in good states on the film surface. Our results show that ZrO(2) thin films fabricated by cathodic arc deposition exhibit favorable bioactivity and cytocompatibility.

Animals↗

PubMed2005

Acid-induced bioactive titania surface.

Nano- and conventional-TiO(2) powders were deposited onto titanium alloy using atmospheric plasma spraying technology. As-sprayed titania coatings were treated by H(2)SO(4) and HCl solutions at room temperature for 24 h, and the bioactivity was evaluated by simulated body fluid tests. Measured X-ray diffraction patterns indicated that as-sprayed titania coatings obtained from both nano and conventional powders were composed of primary rutile as well as a small quantity of anatase and Ti(3)O(5). The surface of as-sprayed coatings prepared from the conventional powder was rougher than that from nanopowder. After immersion in simulated body fluid for 2 weeks, both acid-treated nano- and titania coatings have induced carbonate-containing hydroxyapatite to form on the surfaces. However, this phenomenon did not appear on the surface of as-sprayed nano- and conventional-titania coatings. The results obtained indicated that the bioactivity of plasma sprayed titania coatings was improved by the acid treatment and had nothing to do with phase composition and particle size of the original TiO(2) powders.

Coated Materials, Biocompatible↗

PubMed2005

Effect of hydroxyapatite coating crystallinity on dissolution and osseointegration in vivo.

Hydroxyapatite (HA) coating with different crystallinities were deposited by plasma spraying and vapor-flame treatment process. Their crystallinities are about 55 and 98%, respectively. These coatings were implanted in cortical bone, muscle, and marrow of dogs. The dissolution and osseointegration behavior were evaluated by scanning electron microscope (SEM) observation histological analysis. The results obtained indicated that after implanted in muscle, a bone-like apatite layer was formed on the surface of as-sprayed coating, which was not observed on the surface of the treated coating. The as-sprayed coating has the ability to induce new bone formation on its surface after implanted in marrow. In contrast, the treated coating displays a limited bone bioactivity. The vapor-flame process diminishes the short-term osseointegration properties of the HA coating, but no significant affection was found after three months implantation. Either in muscle or in cortical bone, treated coating exhibits higher stability than the as-sprayed coating, in some conditions.

Animals↗

PubMed2005

Early apatite deposition and osteoblast growth on plasma-sprayed dicalcium silicate coating.

Dicalcium silicate coating was deposited onto a Ti-6Al-4V substrate using plasma-spraying technology. The coating was immersed in simulated body fluid (SBF) for 1, 3, 6, 12, 24, and 48 h to investigate early apatite formation on the coating. Osteoblasts were also seeded onto the surface of the dicalcium silicate coating to evaluate its biocompatibility. Cold field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry were used to evaluate the morphologies and determine the chemical composition of the coatings. The surface structural changes caused by immersion in SBF were analyzed using thin-film X-ray diffraction. After the dicalcium silicate coating was soaked in SBF solution 1-6 h, two types of particles containing calcium and phosphorus were formed on the surface. One type consisted of relatively larger particles (P1) precipitated on the surface of the coating from the precursor cluster formed in the SBF solution. The second type was composed of particles (P2) nucleated on the surface of the coating. With increasing immersion time, the particles coalesced to form a surface Ca-P layer. The Ca-P layer was composed of amorphous calcium phosphate that was not transformed to crystalline apatite until the immersion time in SBF exceeded 24 h. The formation mechanism of the Ca-P layer and apatite on the surface of the coating is believed to be involved in the formation of the Si 3-ring active surface site with negative charge. The cell-seeding test revealed that osteoblasts grew and proliferated very well on the surface of the dicalcium silicate coating.

Animals↗

PubMed2005

In vivo evaluation of plasma-sprayed titanium coating after alkali modification.

In this paper, plasma-sprayed titanium coatings were modified by alkali treatment. The changes in chemical composition and structure of coatings were examined by SEM and AES. The results obtained indicated that a net-like microscopic texture feature, which was full of the interconnected fine porosity, appeared on the surface of alkali-modified titanium coatings. The surface chemical composition was also altered by alkali modification. A sodium titanate compound was formed on the surface of the titanium coating and replaced the native passivating oxide layer. Its thickness was measured as about 150 nm which was about 10 times of that of the as-sprayed coating. The bone bonding ability of titanium coatings were investigated using a canine model. The histological examination and SEM observation demonstrated that more new bone was formed on the surface of alkali-modified implants and grew more rapidly into the porosity. The alkali-modified implants were found to appose directly to the surrounding bone. In contrast, a gap was observed at the interface between the as-sprayed implants and bone. The push-out test showed that alkali-modified implants had a higher shear strength than as-sprayed implants after 1 month of implantation. An interfacial layer, containing Ti, Ca and P, was found to form at the interface between bone and the alkali-modified implant by EDS analysis.

Alloys↗

PubMed2005

In vivo evaluation of plasma-sprayed wollastonite coating.

Wollastonite coatings were prepared by plasma spraying. The bioactivity of wollastonite coatings was investigated in vivo by implanting in dog's muscle, cortical bone and marrow, respectively. The behaviour of bone tissue around wollastonite coatings were examined by histological and SEM observation. After 1 month in the muscle, a bone-like apatite layer was found to form on the surface of the wollastonite coating. When implanted in cortical bone, histological observation demonstrated that bone tissue could extend and grow along the surface of the wollastonite coating. The coating bonded directly to the bone without any fibrous tissue, indicating good biocompatibility and bone conductivity. SEM and EDS analysis revealed that bone did not bond to wollastonite coating directly, but through a Ca/P layer. This suggested that the formation of bone-like apatite layer was very important for bonding to the bone tissue. The amount of bone-implant contact was also measured. Wollastonite coating was shown to stimulate more bone formation on its surface than titanium coating after implantation for 1 month, enhancing the short-term osseointegration properties of implant. The test in marrow indicated that wollastonite coatings could induce new bone formation on their surface showing good bone inductivity property.

Animals↗

PubMed2005

Improvement of surface bioactivity on titanium by water and hydrogen plasma immersion ion implantation.

We have investigated the surface bioactivity of titanium after water and hydrogen plasma immersion ion implantation. Plasma immersion ion implantation (PIII) excels in the surface treatment of components possessing a complicated shape such as medical implants. In addition, water and hydrogen PIII has been extensively studied as a method to fabricate silicon-on-insulator (SOI) substrates in the semiconductor industry and so it is relatively straightforward to transfer the technology to the biomedical field. In our investigation, water and hydrogen were plasma-implanted into titanium sequentially. Our objective is that water PIII introduces near-surface damages that trap hydrogen implanted in the subsequent step to improve the surface bioactivity while the desirable bulk properties of the materials are not compromised. Ti-OH functional groups can be detected on the (H(2)O+H(2))-implanted titanium surface by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. After incubation in simulated body fluids (SBF) for cytocompatibililty evaluation in vitro, bone-like hydroxyapatite was found to precipitate on the (H(2)O+H(2)) implanted samples while no apatite was found on titanium samples plasma implanted with water or hydrogen alone. Human osteoblast cells were cultured on the (H(2)O+H(2))-implanted titanium surface and they exhibited good adhesion and growth. Our results suggest a practical means to improve the surface bioactivity and cytocompatibility of medical implants made of titanium.

Biocompatible Materials↗

PubMed2005

Plasma-treated nanostructured TiO(2) surface supporting biomimetic growth of apatite.

Although some types of TiO(2) powders and gel-derived films can exhibit bioactivity, plasma-sprayed TiO(2) coatings are always bioinert, thereby hampering wider applications in bone implants. We have successfully produced a bioactive nanostructured TiO(2) surface with grain size smaller than 50 nm using nanoparticle plasma spraying followed by hydrogen plasma immersion ion implantation (PIII). The hydrogen PIII nano-TiO(2) coating can induce bone-like apatite formation on its surface after immersion in a simulated body fluid. In contrast, apatite cannot form on either the as-sprayed TiO(2) surfaces (both <50 nm grain size and >50 nm grain size) or hydrogen-implanted TiO(2) with grain size larger than 50 nm. Hence, both a hydrogenated surface that gives rise to negatively charged functional groups on the surface and small grain size (<50 nm) that enhances surface adsorption are crucial to the growth of apatite. Introduction of surface bioactivity to plasma-sprayed TiO(2) coatings, which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys, makes them more superior than many current biomedical coatings.

Apatites↗

PubMed2004

Mechanism of apatite formation on wollastonite coatings in simulated body fluids.

The formation mechanism of apatite on the surface of wollastonite coating was examined. Plasma-sprayed wollastonite coatings were soaked in a lactic acid solution (pH=2.4) to result in the dissolution of calcium from the coating to form silanol (triple bond Si-OH) on the surface. Some calcium-drained samples were soaked in a trimethanol aminomethane solution (pH=10) for 24h to create a negatively charged surface with the functional group (triple bond Si-O(-)). These samples before and after treatment in a trimethanol aminomethane solution were immersed in simulated body fluids (SBF) to investigate the precipitation of apatite on the coating surface. The results indicate that the increase of calcium in the SBF solution is not the critical factor affecting the precipitation of apatite on the surface of the wollastonite coating and the apatite can only form on a negatively charged surface with the functional group (triple bond Si-O(-)). The mechanism of apatite formation on the wollastonite coating is proposed. After the wollastonite coatings are immersed into the SBF, calcium ions initially exchange with H(+) leading to the formation of silanol (triple bond Si-OH) on the surface of the layer and increase in the pH value at the coating-SBF interface. Consequently, a negatively charged surface with the functional group (triple bond Si-O(-)) forms on the surface. Due to the negatively charged surface, Ca(2+) ions in the SBF solution are attracted to the interface between the coating and solution, thereby increasing the ionic activity of the apatite at the interface to the extent that apatite precipitates on the coating surface.

Apatites↗

PubMed2004

Biomimetic growth of apatite on hydrogen-implanted silicon.

Hydrogen in silicon has been widely applied in semiconductor fields. In this paper, the application of hydrogen-implanted silicon wafer in biomedical fields was explored by investigating its bioactivity. Hydrogen implanted silicon wafers were prepared using plasma immersion ion implantation. The surface structures of the 1.4 x 10(17) cm(-2) hydrogen-implanted silicon wafers were investigated using atomic force microscopy and transmission electron microscopy (TEM). The hydrogen depth profiles were acquired by SIMS and the crystal quality of the as-implanted silicon was studied by channeling Rutherford backscattering spectrometry (RBS). The bioactivity of the implanted silicon was evaluated using the biomimetic growth of apatite on its surface after it was soaked in simulated body fluid for a period of time. The TEM, SIMS and RBS results indicate the formation of an amorphous hydrogenated silicon (a-Si:Hx) layer has been formed on the surface of the hydrogen-implanted silicon wafer. After immersion in SBF for 14 days, bone-like apatite is observed to nucleate and grow on the surface. With longer soaking time, more apatite appeared on the surface of the hydrogen implanted silicon but our control experiments did not reveal any apatite formation on the surface of the un-implanted silicon wafer, hydrogenated crystalline silicon wafer (with hydrogen, but no amorphous surface), or argon-implanted silicon wafer (amorphous surface but without hydrogen). Our results indicated that the bioactivity of silicon wafer can be improved after hydrogen implantation and the formation of the amorphous hydrogenated silicon (a-Si:Hx) surface also plays a synergistic role to improve the bioactivity.

Alpha Particles↗

PubMed2004

In vivo evaluation of plasma sprayed hydroxyapatite coatings having different crystallinity.

In this paper, hydroxyapatite (HA) coatings having the crystallinities of 56% and 98% were deposited by the plasma spraying and vapor-flame treatment process. The phase composition and crystallinity of the coatings were investigated by X-ray diffraction and infrared spectra. The dissolution behavior of the coatings in tris-buffer solutions was examined. The results obtained indicated that the coating having the high crystallinity showed the lower dissolution as compared to the low crystallinity coating. The bone bonding ability of HA coatings were observed in vivo by implanted in dog's femur. After 3 months implantation, the high crystallinity coating showed the higher shear strengths and remained integrated, whereas the separation of the coating fragments was clearly observed in the coating having low crystallinity.

Animals↗

PubMed2002

Reactivity of plasma-sprayed wollastonite coating in simulated body fluid.

We incubated wollastonite coatings prepared with plasma spraying in simulated body fluids for different periods to investigate the reactivity. The surface structures of wollastonite coatings immersed in simulated body fluids were analyzed with scanning electron microscopy, Auger electron spectroscopy, and transmission electron microscopy. The results showed a carbonate-containing hydroxyapatite layer formed on the surface of a plasma-sprayed wollastonite coating soaked in simulated body fluids, and a silica-rich layer appeared on the surface of the coating before the formation of the carbonate-containing hydroxyapatite layer. The formation mechanism of apatite on the coating surface could be explained in terms of the ionic exchange between H(+) within simulated body fluids and Ca(2+) in the coating, which resulted in an increase in the ionic activity product of the apatite in simulated body fluids and provided a specific surface with a lower interface energy to the formation of apatite nuclei.

Biocompatible Materials↗

PubMed2002

Bioactivity of plasma sprayed dicalcium silicate coatings.

Dicalcium silicate coatings on titanium alloys substrates were prepared by plasma spraying and immersed in simulated body fluids for a period of time to investigate the nucleation and growth of apatite on the surface of the coatings. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of dicalcium silicate coatings before and after immersion in simulated body fluid. The plasma sprayed dicalcium silicate coating was bonding tightly to the substrate. The coating was mainly composed of beta-Ca2SiO4 and glassy phase. A dense carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the plasma sprayed dicalcium silicate coating soaked in SBF solution for 2 days. In addition, a silica-rich layer was also observed between CHA layer and coatings. With an increase in the immersion time, the CHA layer gradually became thicker. The results obtained indicated that the plasma sprayed dicalcium silicate coating possesses excellent bioactivity.

Apatites↗

PubMed2002

Plasma sprayed wollastonite/TiO2 composite coatings on titanium alloys.

Wollastonite/TiO2 composite coatings were prepared using plasma spraying technology onto Ti-6Al-4V substrate. The composite coatings exhibit obvious lamellar structure with alternating wollastonite coating and TiO2 coating. No obvious cracks exist on the interface between coatings and substrate. In the case of composite coatings, the primarily crystalline phases of the coatings are wollastonite and rutile, indicating wollastonite and TiO2 did not react during plasma spraying process. Some of rutile in the powders transforms into anatase due to plasma spraying. The mean bond strength of the composite coatings is higher than 30 MPa. The Vickers microhardness of coatings increase with the increase in the content of TiO2. Wollastonite/TiO2 composite coatings were soaked in simulated body fluid to examine their bioactivity. Carbonate-containing hydroxyapatite (CHA) layer was formed on the surface of the wollastonite and W7T3 coatings soaked in simulated body fluid, while was not formed on the surface of the TiO2 and W3T7 coatings after immersion. In addition, a rich-silica layer appeared at the interface of CHA and wollastonite and W7T3 coatings. In order to investigate the cytocompatibility of the coatings, osteoblast was seeded onto the surface of the coatings. The scanning electron microscopy observation showed that the addition of wollastonite promote the proliferation of osteoblast. It is enough to prove that the wollastonite and wollastonite/TiO2 composite coatings possess excellent cytocompatibility.

Alloys↗