Key Engineering Materials Vols. 330-332

Abstract: Protein adsorption is driven by various interactions. The contribution of surface charge to bovine serum albumin (BSA) adsorption on hydroxyapatite (HA) ceramic was investigated by adjusting the liquid environment in which the solid particles dispersed. Zeta potentials of HA and the adsorption of BSA on the surface were tested as a function of pH, ionic strength, Ca2+ and PO4 3- concentrations in the aqueous solutions, and the results showed that both of them were greatly affected by those experimental variations. Besides, the amount of adsorbed BSA was related to the variation of zeta potential of HA, as could be well understood in terms of electrostatic interactions.

Abstract: Heparin is covalently immobilized onto the surface of anatase TiO2 film using the bifunctional linking reagent, APTES (3-Aminopropyltriethoxylsilane), which can be bonded to the film by reaction between ethoxyl of the linking reagent and hydroxyl of the film. Compared to the control, the immobilization is enhanced by phosphoric acid chemical pre-adsorption on the film for there is more hydroxyl group present. Platelets deposited to heparinized surface showed only minor spreading and aggregation. The results of this study suggest that heparin immobilization to anatase TiO2 films via phosphoric acid interface may improve the in vivo blood compatibility.

Abstract: The aim of this study was to compare the plasma protein adsorptive property of the natural hydroxyapatite (HA) and the synthesized HA to human albumin (Alb), fibrinogen (Fib) and immunoglobulin G (IgG). Different methods such as reflectometry interference spectroscopy (RIfS) measuring, Fourier transform infrared spectroscopy (FTIR) analysis and weighing assessment were used to measure the adsorbed amount of Alb, Fib and IgG on the natural HA and the synthesized HA. To compare the adsorptive property of protein adsorbed on these two kinds of materials, the ratio of Alb/Fib (RA/F) and the ratio of Alb/IgG (RA/I) were calculated. The results from all three methods showed that the values of RA/F and RA/I obtained with natural HA were smaller than those obtained with synthesized HA, that indicated that the natural HA adsorbed more human fibrinogen than human albumin and thas it would enhance blood coagulation and in favor of bone repairing.

Abstract: O-doped Diamond-Like carbon (O-DLC) films were prepared by direct magnetic filtered cathodic vacuum arc deposition (DC-MFCVAD) under different O2 gas flow at room temperature (R.T.). Raman spectra were used to characterize structure of films. The wettabilities of the O-DLC films also were investigated by contact angle measurements using four common liquids. For studying films’ interaction with blood, platelet adhesion experiment in vitro was done to characterize anticoagulant property of the O- DLC films from an aspect. Furthermore, ultraviolet spectrophotometer was employed to measure the optical band gap of the synthesized films. All of the results showed that O-DLC films have good anticoagulant property, oxygen doping can prevent graphite-like tendency of DLC films and increase band gap in a way, this kind of film materials may be become a new candidated biomaterials.

Abstract: Crystalline hydroxyapatite (HA) and 0.8 wt.% silicon-substituted HA (SiHA) thin films were produced using magnetron co-sputtering. These films were subjected to contact angle measurements and in vitro cell culture study using human osteoblast-like (HOB) cells. A wettability study showed that SiHA has a lower contact angle, and thus is more hydrophilic in nature, as compared to HA. Consequently, enhanced cell growth was observed on SiHA at all time-points. Furthermore, distinct and well-developed actin filaments could be seen within HOB cells on SiHA. Thus, this work demonstrated that the surface properties of the coating may be modified by the substitution of Si into the HA structure.

Abstract: The effect of Mn on the protein adsorption of calcium phosphate coatings is investigated in this work. Mn containing β-tricalcium phosphate (Mn-TCP) is first prepared through a coprecipitation based methods. Then Mn-TCP is dispersed into the fluoridated hydroxyapatite (FHA) precursor sol. Mn-TCP/FHA biphasic coatings are prepared with these sols. After cell culture, it is found the amount of protein adsorbed on the coatings following this rule: Mn-TCP/FHA > β-TCP/FHA > FHA. That is ascribed to two reasons: a) Ca and PO4 releasing can promote the activity of cells; b) Mn releasing promotes protein activation even at quite low concentration.

Abstract: This study is to investigate the effect of PAM on protein adsorption and osteoblastic cells adhesion to HA bioceramics. PAM was immobilized on the surface of HA bioceramics for bone scaffold by chelating. The outermost layer of the specimens was analyzed by XPS and FT-IR. The protein adsorption test was performed using the 10% bovine calf serum absorbed on the specimens in vitro. The osteoblastic cells were inoculated and cultured on the scaffolds. SEM, MTT test and ALP activity test evaluated the cell attachment, proliferation and activity on the scaffolds. Characteristic peaks in XPS and FT-IR spectra indicated PAM being immobilized on the surface of the bioceramics. PAGE and 2-D DIGE results indicated that HA absorbed more acidic proteins, while PAM-HA absorbed more basic and neutral proteins.The cell culture test indicated that the cells actively proliferated on the scaffolds. There was no significant difference between the ALP activity of the cells cultured for 1d, 3d, 5d and 7d on PAM-HA and that of the controls. PAM had no obvious effect on the cytocompatibility of HA, and PAM-HA bioceramics could be used as bone scaffold with potential ability to improve osteogenesis.

Abstract: Ammonia implanted silicon was performed by using plasma immersion ion implantation (PIII) to form a silicon nitride films. Blood compatibility of the prepared samples was investigated by platelets adhesion testing. It showed less activation i.e. lower thrombosis risks occurs on the prepared silicon nitride films than control silicon sample. The enhanced blood compatibility of the material is attributed to the modified surface properties such as hydrophilicity from thermodynamic adsorption perspective, which is related to surface chemical bonding states achieved by PIII process.

Abstract: The aim of present work was to study the interaction between human plasma protein-albumin (Alb) and immunoglobulin G (IgG) and the surfaces of two kinds of diamond-like carbon (DLC-A and DLC-B) and titanium (Ti) film. Fourier transform infrared spectroscopy (FTIR) was used to perform both quantity investigation and secondary structure analysis of above two proteins adsorbed on material surfaces. A modified Coomassie brilliant blue (CBB) protein assay was also used to study the amount of adsorbed proteins. The result of FTIR quantitative evaluation shows that the ratio of adsorbed Alb to IgG (RA/I) on three kinds of material surface has an order: DLC-A > DLC-B > Ti, which is coincide with the result from CBB protein assay. The result of secondary structure analysis shows that the conformation of Alb and IgG changes in a largest degree after adsorbed on Ti and a smallest degree on DLC-A surface. Both the results indicate that the anti-thrombogenicity of DLC-A seems to be the best and Ti is the worst.

Abstract: Hydroxyapatite based biomaterials were prepared by a spark plasma sintering technology. The human limb-derived osteoblasts were cultured on the various biomaterial surfaces (HA, RF21, 1SiHA and 5SiHA) for up to two weeks to investigate the cellular behaviors. The bone gammacarboxyglutamic protein or osteocalcin in the medium were determined at different periods of cell culture. The results indicated that a combined effect of bioceramic surface composition and surface morphology had influenced the osteoblast behaviors. The amount of osteocalcin in the medium increased in the initial periods of culture but decreased in the late periods of culture.