Surface In Simulated Body Fluid Research Articles

Eco-friendly synthesis of mesoporous bioactive glass ceramics and functionalization for drug delivery and hard tissue engineering applications

Hard tissue regenerative mesoporous bioactive glass (MBG) has traditionally been synthesized using costly and toxic alkoxysilane agents and harsh conditions. In this study, MBG was synthesized using the cheaper reagent SiO2 by using a co-precipitation approach. The surface properties of MBG ceramic were tailored by functionalizing with amino and carboxylic groups, aiming to develop an efficient drug delivery system for treating bone infections occurring during or after reconstruction surgeries. The amino groups were introduced through a salinization reaction, while the carboxylate groups were added via a chain elongation reaction. The MBG, MBG-NH2, and MBG-NH-COOH were analyzed by using various techniques: x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), scanning electron microscopy and energy-dispersive x-ray spectroscopy. The XRD results confirmed the successful preparation of MBG, and the FTIR results indicated successful functionalization. BET analysis revealed that the prepared samples were mesoporous, and functionalization tuned their surface area and surface properties. Cefixime, an antibiotic, was loaded onto MBG, MBG-NH2, and MBG-NH-COOH to test their drug-carrying capacity. Comparatively, MBG-NH-COOH showed good drug loading and sustained release behavior. The release of the drug followed the Fickian diffusion mechanism. All prepared samples displayed favorable biocompatibility at higher concentration in the Alamar blue assay with MC3T3 cells and exhibited the good potential for hard tissue regeneration, as carbonated hydroxyapatite formed on their surfaces in simulated body fluid.

Long-term antibacterial Ag+-release biomaterials based on anodized Ti6Al4V and silver nanoparticles

There is a need of antibacterial prosthetic devices that can offer long-term protection against infection after implantation. In the present study, a chemical synthesis method is used for the synthesis of silver nanoparticles (Ag NPs) on anodized Ti6Al4V (a Ti alloy with 6 % wt. Al and 4 % wt. V). The reported method for Ag NPs deposition is easy, rapid and provides an optimal coating not only on the surface of TiO2 nanotubes but also inside them, which favors a continued Ag+ release. In contrast to the bibliography, where Ag+ is released within the first 14 days, we report a sustained release until 46 days in simulated body fluid (SBF) which will be helpful to obtain long-term antibacterial prosthetic devices. Anodization charge has been proven to be a key parameter; an 80 C anodizing charge produced materials with higher and more sustained Ag+ release than the 10 C anodizing charge (5,58 mg/L vs. 3,19 mg/L after 46 d, respectively). Electron microscopy characterization showed a uniform distribution of Ag NPs on the surface of both anodic layers. In the case of the 80 C charge, Ag NPs were also located inside the TiO2 nanotubes as observed in the cross-section analysis of the anodic layer. A higher amount of Ag NPs was deposited on the 80 C anodized sample due to a higher surface area and thicker anodic layer (110 nm vs. 80 nm) where NPs could be fixed (as analyzed by Energy Dispersive X-ray) (2,87-fold higher than 10 C anodized sample). The 80 C anodizing charge also produced more bioactive surfaces since the growth of apatite on its surface in SBF was observed, but not in the case of 10 C anodizing charge. The 80 C anodized Ti6Al4V + Ag NPs showed excellent results for antibacterial activity and biofilm formation reduction when tested against Staphylococcus aureus V329 and Staphylococcus epidermidis RP62A strains. A lethality of 99,9 % for both strains was obtained when compared to the Ti6Al4V anodized samples without Ag NPs.

Evaluation of corrosion resistant, antimicrobial and cytocompatible behaviour of cobalt based metallosurfactants self-assembled monolayers on 316L stainless steel surface

The present research is aimed at developing a more economic and ecological way to improve the biocompatibility of medical-grade stainless steel. In order to accomplish the purpose, the 316L stainless steel has been functionalized by depositing self-assembled monolayers (SAMs) of cost-effective Cobalt-based metallosurfactants (CoMS). The fabrication of well-defined SAMs on the surfaces was characterised using FTIR-ATR, spectroscopic ellipsometry and water contact angle measurements. The corrosion stability of functionalized surfaces in simulated body fluid was accessed by various electrochemical and spectroscopic techniques like cyclic potentiodynamic polarisation (CPP), chronoamperometry, electrochemical impedance spectroscopy, FE-SEM, XPS and ICP-MS studies. The metallosurfactant SAMs provided superior corrosion and bacterial protection especially against Gram-negative E. coli bacteria. The cytotoxicity of the SAMs against mouse embryonic fibroblast cell line (NIH-3T3) was assessed by MTT and fluorescent assays. The experimental results reveals that the metallosurfactant SAMs are multifunctional i.e., they enhanced the anticorrosive and anti-bacterial properties of the SS 316L without compromising the cytocompatibility of the surface which make them promising candidates for biomedical applications.

Dental resin composites with improved antibacterial and mineralization properties via incorporating zinc/strontium-doped hydroxyapatite as functional fillers

This study intends to improve the antibacterial and mineralization performance of photocurable dental resin composites (DRCs) to reduce the possibility of repair failure caused by secondary caries. To the end, functionalized hydroxyapatite (HAp), including Zn-doped (Zn/HAp) and Sr-doped HAp (Sr/HAp), were added into the bisphenol A glycidyl methacrylate and triethylene glycol dimethacrylate mixture, providing the DRCs with antibacterial and mineralization capacity, respectively. By controlling the total amount of inorganic filler at 70 wt%, these HAp powders were introduced into the resin matrix with barium glass powder (BaGP), while the ratios of HAp to aGP varied from 0:70 to 8:62. And the 8 wt% of HAp could be pure HAp, Zn/HAp, Sr/HAp, or Zn/HAp +Sr/HAp in different ratios (i.e. 2:6, 4:4, 6:2). Though the fillers varied, the obtained DRCs displayed similar micro-morphology, flexural strength (∼110 MPa) and modulus (∼7 GPa), and Vickers hardness (∼65). When the doping amounts of Sr2+/Zn2+ reached 15 mol% of Ca2+ in the Sr/HAp and Zn/HAp, the DRCs displayed a high antibacterial activity by killing ∼95% Staphylococcus aureus, and induced rich mineral deposition on surface in simulated body fluid. The incorporation of the Zn/HAp and Sr/HAp into the DRCs did not cause significant cytotoxicity, with L929 fibroblasts remaining >99% viability as cultured in extracts made from the DRCs. Therein, the DRC preparations containing both Zn/HAp and Sr/HAp have achieved improvements in both the biomineralization and antibacterial performance, as well as, having sufficient mechanical properties and excellent biocompatibility for dental restoration.

CaO-B2O3-SiO2 glass fibers for wound healing

It was reported by Jung and Day in 2011 that a cotton-like glass fiber pad made of borate glass 13-93B3 demonstrated a remarkable wound healing effect. It was approved for sale as a novel wound dressing in the management of acute and chronic wounds in 2016. However, the detailed mechanism of its wound healing effect has not been reported. In the present study, glass fibers of different composition in the system CaO-B2O3-SiO2 were prepared and their in vitro properties investigated to determine the role of the constituent components in wound healing. Fine glass fibers that were 0.6–2.0 μm in diameter were obtained by a melt blown method. However, these fibers were accompanied by small glass beads because of the low viscosity of the glass melts. 13-93B3 glass released an appreciable amount of borate and calcium ions into simulated body fluid (SBF). The amounts of these released ions decreased with partial replacement of the B2O3 in 13-93B3 with SiO2. The addition of large amounts of the borate and calcium ions into the culture medium decreased the viability of the L929 fibroblasts. Partial replacement of the B2O3 in 13-93B3 with SiO2 induced the formation of an apatite-like phase amenable to the adsorption of biological components on its surface in SBF. The wound healing effect of these glass fibers of different composition is worth examining in future animal experiments.

A strontium and amorphous calcium phosphate dipped premixed injectable calcium silicate-based ceramic for dental root canal sealing

A type of strontium and amorphous calcium phosphate dipped premixed injectable tricalcium silicate-based dental root canal sealer was developed as the following protocols. A powder mixture containing tricalcium silicate, strontium carbonate (6, 8, 10, and 12 wt%), zirconia (20 wt%), calcium chloride (6 wt%), and amorphous calcium phosphate (ACP) (5 wt%) was mixed with liquid polyethylene glycol 400 (PEG 400) at a liquid-to-powder ratio of 0.5 mL/g and mechanically ground using a planetary ball to obtain the premixed injectable calcium silicate-based sealer. The sealer’s physicochemical property and cytocompatibility were evaluated in vitro. Quantitative data were expressed as mean ± standard deviation, and Student's t-test or a one-way analysis of variance (ANOVA) test were carried out at significant differences with P < 0.05. All the sealer groups had suitable flowability (21.3–33.3 mm, n = 3), setting time (241.87 ± 32.72–299.00 ± 26.05 min, n = 8) and radiopacity basically according to ISO 6876-2012 standard. The pH value generally stabilized between 10 and 12 (n = 5) when the sealer was immersed into deionized water or phosphate buffered solution. The sealing property of root canal sealer was evaluated by dye penetration, 6% strontium groups had the best root canal sealing property among all the groups (1.21 ± 0.17–5.75 ± 0.97) mm, n = 10, P < 0.05). 6% strontium groups bonded together to the dental root canal wall, penetrated the dentinal tubule to occlude the dentinal tubules, formed calcium–silicate–hydrate (C–S–H) network structure, induced a layer of nano hydroxyapatite crystal grown on its surface in simulated body fluid (SBF), showing good biomineralization activity. It also had osteogenic differentiation activity cultured with rat bone marrow mesenchymal stem cells (n = 5, P < 0.05). This sealer provided a potential new filling material for root canal therapy and has promising application prospects.

Reactivity of Titanium Dental Implant Surfaces in Simulated Body Fluid.

Osseointegration of titanium (Ti) implants in bone is crucial for dental implant treatment. Bacterial challenge possibly leading to peri-implantitis threatens long-term success. For the improvement of osseointegration, an understanding of materials and tissue intervention is needed. This in vitro study analyzed changes of different implant surfaces exposed to simulated body fluid (SBF). Implants were analyzed by scanning electron microscopy/X-ray photoelectron spectroscopy. Supernatants (SNs) were assessed using inductively coupled plasma-mass spectrometry (ICP-MS). Additional calcium (Ca) and phosphate (P) crystals developed (Hank's buffered salt solution (HBSS)) on implants with layered surfaces. ICP of SN demonstrated a decreased Ca/P ratio. After incubation with human serum (HS), layers appeared flattened containing <1% Ca/P. The etched/machined implants showed the formation of a surface transformation layer or coating consisting of crystalline Ca/P precipitations and a decrease in the Ca/P ratio in the supernatant. Incubation in HS induced noncrystalline coverage, and increased Ti/Ca/P was detected in supernatants. HBSS induced crystals on surfaces of modified implants and crystalline covers on nonmodified implants containing Ca/P. The serum did not show the development of HA-like structures but showed dissolving effects. Titanium surfaces show completely altered behavior when incubated in serum-containing SBF.

A novel cost-effective approach to fabricate diopside bioceramics: A promising ceramics for orthopedic applications

The objective of the present study is to prepare low temperature diopside (CaMgSi2O6) ceramics from natural waste (Rice husk ash & eggshells) and study the physico-mechanical and in vitro biological properties. X-ray powder diffraction (XRD), thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), Fourier transforms infrared (FTIR) and energy-dispersive spectrometry (EDS) were used to assess the crystalline phase, thermal behavior, microstructure, functional groups and composition, respectively. Degradation as well as mechanical stability was studied by testing the weight loss and compressive strength in dynamic mode of simulated body fluid (SBF) according to ISO 10993-14. The bioactivity of diopside samples was tested by means of ability and rate of apatite mineralization on the surface in static mode of SBF. Cytocompatibility by human osteoblast-like cells and their proliferation were studied using MTT assay. Results revealed that the pure phase of diopside was successfully attained at significantly low temperature (800 °C) with good mechanical properties, which were nearly similar to that of human cortical bone, and with enhanced mechanical stability. Diopside ceramics possessed apatite growth on its surface in SBF and exhibits excellent biocompatibility with MG-63 cells. These results suggested that prepared diopside can be a cost-effective bioceramics for potential orthopedic applications.

The Effect of Material Surface Microstructure on the Enhancement of Bone-Bonding Ability of a Hydroxyapatite-Implant by Low-Intensity Pulsed Ultrasound (LIPUS)

Excellent firm bonding between the biomaterials and bone tissue (osseointegration and osteo-conductivity) has been desired for the stability in vivo of dental implants and artificial joints. Much has been learned about this concept, which has led to significant improvements in the design and surface modification of implants in the field of implant dentistry, orthopedic surgery. We have already reported that low-intensity pulsed ultrasound (LIPUS) irradiation can accelerate the bone bonding ability of the bio-conductive materials such as bioactive titanium and hydroxyapatite implant. However, it is still unclear whether the LIPUS could have same effect to different types of the bioactive-materials. Therefore, in this study, the differences of bone-like hydroxyapatite formation on some kind of hydroxyapatite surface in simulated body fluid (SBF) under the LIPUS irradiation were investigated. Two kinds of hydroxyapatite samples immersed in SBF was exposed to ultrasound waves, the bone-like apatite on the surface was analyzed by Scanning electron microscopy and X-ray diffraction. As a result, the enhancement of hydroxyapatite formation on the surface by LIPUS was confirmed, the initial epitaxial nucleation and crystal growth of apatite depended on crystal structure of the surface of matrix materials.

Multifunctional halloysite nanotube based composite coatings on titanium as metal implant for orthopedic applications

The development of orthopedic implant materials which promote osseointegration and reduce bacterial infection has gained considerable attention to avoid long-term complications in the biomedical industry. Present study reports the electrodeposition of strontium-halloysite nanotubes (Sr-Hal)/lanthanum, cerium substituted hydroxyapatite (La,Ce-HAP) composite coatings on titanium surface with varying Sr-Hal concentration at 1, 2 and 3 wt%. Their physicochemical and morphological characterizations were performed. The mechanical properties of the coatings were evaluated using adhesion and microhardness tests and from the obtained results it was found that, the incorporation of Sr-Hal improved the mechanical properties of the composite coatings. The electrochemical assessment of composite coated Ti surfaces in simulated body fluid (SBF) solution was investigated using polarization measurements. The anti-corrosion properties of the Sr-Hal/La,Ce-HAP composite coated Ti with 3 wt% Sr-Hal was found to be excellent compared to the other wt% of Sr-Hal incorporated in the composite. The antibacterial, anti-cancer and cell viability study of Sr-Hal/La,Ce-HAP composite coatings and their results reveal the bactericidal effect, osteosarcoma cell growth impediment and higher number of viable cells respectively. As a whole, all the studies exposed that the Sr-Hal/La,Ce-HAP composite coatings on Ti has improved the mechanical, anticorrosion and biocompatible performance indicating the Sr-Hal/La,Ce-HAP composite coated titanium is a prospective implant material for orthopedic applications.

Three-Dimensional Printed Porous Titanium Screw with Bioactive Surface Modification for Bone–Tendon Healing: A Rabbit Animal Model

The interference screw fixation method is used to secure a graft in the tibial tunnel during anterior cruciate ligament reconstruction surgery. However, several complications have been reported, such as biodegradable screw breakage, inflammatory or foreign body reaction, tunnel enlargement, and delayed graft healing. Using additive manufacturing (AM) technology, we developed a titanium alloy (Ti6Al4V) interference screw with chemically calcium phosphate surface modification technology to improve bone integration in the tibial tunnel. After chemical and heat treatment, the titanium screw formed a dense apatite layer on the metal surface in simulated body fluid. Twenty-seven New Zealand white rabbits were randomly divided into control and additive manufactured (AMD) screw groups. The long digital extensor tendon was detached and translated into a tibial plateau tunnel (diameter: 2.0 mm) and transfixed with an interference screw while the paw was in dorsiflexion. Biomechanical analyses, histological analyses, and an imaging study were performed at 1, 3, and 6 months. The biomechanical test showed that the ultimate pull-out load failure was significantly higher in the AMD screw group in all tested periods. Micro-computed tomography analyses revealed early woven bone formation in the AMD screw group at 1 and 3 months. In conclusion, AMD screws with bioactive surface modification improved bone ingrowth and enhanced biomechanical performance in a rabbit model.

Microstructure and bioactivity of a cold sprayed rough/porous Ta coating on Ti6Al4V substrate

To improve the bioactivity and biocompatibility of titanium implants, a rough/porous tantalum (Ta) coating was firstly prepared on Ti6Al4V substrate by cold spraying. The results indicated that the surface of Ta coating is extremely rough with lots of visible holes, because of poor deposition quality. Microstructure and microhardness results showed that different layers appeared in the inner and outer parts of coatings, corresponding to porosity, due to lack of subsequent compaction. The simulated body fluid (SBF) soaking test showed that spherical apatite sediments were mineralized on rough/porous surface in SBF after 2–4 weeks, which demonstrated that the cold sprayed Ta coating had good bioactivity. This was mainly attributed to the rough/porous surface of Ta coating obtained by cold spraying, which is conducive to the heterogeneous nucleation of apatite on it.

Fabrication of Porous Bone Scaffolds Using Alginate and Bioactive Glass.

Porous composite scaffold using an alginate and bioactive glass ICIE16M was synthesized by a simple freeze-drying technique. The scaffold was characterized using compression testing, Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), X-ray microtomography (XMT) and scanning electron microscopy (SEM). The bioactivity of the scaffold was evaluated by its ability to form apatite on its surface in simulated body fluid (SBF). The data collected showed evidence that the novel material produced had an appropriate pore size for osteoconduction, with an average pore size of 110 µm and maximum pore size of 309 µm. Statistical analysis confirmed that the glass filler significantly (p < 0.05) increased the collapse yield of the scaffolds compared with pure alginate scaffolds. The ICIE16M glass had an amorphous structure, favorable for bioactivity.

Nanodiamonds for improving lubrication of titanium surfaces in simulated body fluid

Hip implants are often made from titanium or titanium-based alloys. However, wear during the operation inside the human body is a key source of implant failure and adverse health effects. We propose new insight on the lubrication of titanium components. Addition of small amounts (less than 0.2 wt%) of nanodiamonds (NDs) to simulated body fluid promotes a substantial improvement in friction (3 times reduction) and wear (up to 2 orders of magnitude wear reduction) behavior of the titanium surfaces. Interestingly, the amount of NDs needed for improvement of friction and wear characteristics is critically dependent on the applied loads. With higher contact loads, larger concentrations of NDs are needed for better friction and wear reduction. Analysis of the wear track formed during sliding indicates the formation of a carbon-rich tribolayer which improves tribological properties of the contacting surfaces. Our results suggest that the carbon layer is formed from the nanodiamonds embedding in the top layer of titanium.

A new strategy for developing chitosan conversion coating on magnesium substrates for orthopedic implants

Chitosan as a natural biopolymer was immobilized and chelating-deposited with and without bioactive glass (BG) onto Mg substrates by means of a chemical conversion process at 75 °C to provide anti-corrosion properties, good adhesion and biocompatibility. The aim of the present work was to integrate the surface of biodegradable Mg as a part of the corrosion resistant coating via metal-chitosan complexation process.The surface morphology and composition of the coatings were characterized by Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The results provided evidence of the formation of a chitosan coating as well as its chelating reaction and immobilization on magnesium by a chemical conversion process. The non-alkalization of the chitosan solution was ascribed to the protective layer of Mg (II)-chitosan complex, which inhibits the further migration of Mg ions. The in vitro bioactivity of both chitosan (CHI)-coated and chitosan/BG (CHI/BG)-coated surfaces in simulated body fluid (SBF) proved the complete retention of chitosan and BG on the magnesium substrates. The XRD analysis of the (CHI/BG) coating after 2 weeks immersion in SBF showed mainly the formation of magnesium hydrogen phosphate hexahydrate and undetected amorphous (Ca, Mg) phosphate. The present study represents a novel attempt to modify the surface of Mg by a simple, one-step chemical conversion treatment in chitosan to form a Mg (II)-chitosan complex layer. Mechanisms for the Mg-chitosan complexation process and for the coating bioactivity behavior in SBF were discussed.

Orthopaedic bioactive glass/chitosan composites coated 316L stainless steel by green electrophoretic co-deposition

Single-step electrophoretic co-deposition (EPD) technique was used to enhance the bioactivity of the 316L stainless steel (316L SS) surface by bioactive glass/chitosan composite coatings. Two modified glass compositions of Bioglass® by the addition of boron were utilized to prepare such composite layers, and the Bioglass® was synthesized for comparison. Different EPD coating factors were studied. Namely, voltage, time, glass powder, and chitosan concentrations, to obtain crack-free and good adhesive coatings. The achieved surfaces were characterized by SEM/EDX, TGA, XRD and FTIR and their wettability and roughness were investigated. The in vitro bioactivity of the coated metals was compared in simulated body fluid (SBF) and Dulbecco's modified eagle medium (DMEM) for up to 15days. The electrochemical corrosion behavior of the coated metals was evaluated using potentiodynamic polarisation and impedance techniques in the two biological solutions SBF and DMEM at 37°C. The results showed that the achieved coatings were uniform, homogenous and crack-free with desirable thickness. Moreover, the coating layers were exhibited by very high wettability, and their roughness values ranged from 170±18 to 234±17μm. The in vitro bioactivities proved that the coating layers represented a better ability to form hydroxyapatite crystals on their surfaces in SBF than in DMEM. The corrosion resistance of 316L SS was improved by the bioactive composite coatings.

Employing the cyclophosphate to accelerate the degradation of nano-hydroxyapatite/poly(amino acid) (n-HA/PAA) composite materials

Owing to the good degradability and biocompatibility of polyphosphoesters (PPEs), the aim of the current study was to investigate a novel degradable composite of nano-hydroxyapatite/poly(amino acid) (n-HA/PAA) with cyclophosphate (CPE) via in situ melting polymerization to improve the degradation of n-HA/PAA. The structure of each composite was characterized via Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The degradation properties were studied in terms of the weight loss and pH in a phosphate-buffered saline (PBS) solution, while the surface morphology was examined using a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) after soaking the surface in simulated body fluid (SBF). The cell proliferation, cell adhesion, and alkaline phosphatase (ALP) activity were used for the analysis of cytocompatibility. The weight loss results showed that the n-HA/PAA composite was 9.98 wt%, weighed after soaking in the PBS solution for 12 weeks, whereas the nano-hydroxyapatite/polyphosphoester-amino acid (n-HA/PPE-AA) composite was 46.94 wt%. The pH of the composites was in a suitable range between 6.64 to 7.06 and finally stabilized at 7.39. The SEM and EDS results revealed the formation of an apatite-like layer on the surface of the n-HA/PPE-AA composites after soaking in SBF for one week. The cell counting Kit 8 (CCK-8) assay of the cell culture in the leaching liquid of the n-HA/PPE-AA composites exhibited non-cytotoxicity and high-proliferation, and the cell adhesion showed the well spreading and normal phenotype extension of the cells on the n-HA/PPE-AA composites surface. Concurrently, the co-culture results of the composites and cells confirmed that the n-HA/PPE-AA composites exhibited a higher ALP activity. In summary, the results demonstrated that the n-HA/PPE-AA composites had a controllable degradation property, good bioactivity, and cytocompatibility.

Optimization of Oxidation Temperature for Commercially Pure Titanium to Achieve Improved Corrosion Resistance

Thermal oxidation of commercially pure titanium (cp-Ti) was carried out at different temperatures, ranging from 200 to 900 °C to achieve optimum corrosion resistance of the thermally treated surface in simulated body fluid. Scanning electron microscopy, x-ray diffraction, Raman spectroscopy and electrochemical impedance spectroscopy techniques were used to characterize the oxides and assess their protective properties exposed in the test electrolyte. Maximum resistance toward corrosion was observed for samples oxidized at 500 °C. This was attributed to the formation of a composite layer of oxides at this temperature comprising Ti2O3 (titanium sesquioxide), anatase and rutile phases of TiO2 on the surface of cp-Ti. Formation of an intact and pore-free oxide-substrate interface also improved its corrosion resistance.

Quantitative Analysis of Apatite Formation on Titanium and Zirconia in a Simulated Body Fluid Solution Using the Quartz Crystal Microbalance Method

The bone-bonding ability of a material is evaluated by examining apatite formation on its surface in simulated body fluid (SBF). Partially stabilized zirconia (ZrO2) is currently attractive as an alternative to titanium (Ti) implants; however, no quantitative analysis of apatite formation between Ti and ZrO2 in SBF has been reported. In the present study, we quantitatively evaluated apatite formation onto Ti or ZrO2 in SBF using the 27 MHz quartz crystal microbalance method (QCM). In the QCM measurements, apatite formation was detected as a frequency decrease in the Ti or ZrO2 sensor. Frequency decreases were observed at around 1 hour for Ti and at around 2 hours for the ZrO2 sensor after the injection of SBF. This revealed that the Ti sensor showed faster apatite formation than ZrO2. There was no significant difference in the amounts of apatite formation between the Ti and ZrO2 sensors after 24 hours of apatite formation in SBF. In conclusion, the present quantitative study using QCM revealed that apatite formation on the Ti surface in the SBF was obviously faster than that on the ZrO2 surface. Faster apatite formation may predict faster initiation of bone formation on Ti compared with ZrO2.

Bovine Serum Albumin Adsorption onto Hydroxyapatite and Biphasic Calcium Phosphate Ceramic Granules

Calcium phosphate ceramics are one of the most studied biomaterials for bone substitution and regeneration. Bioactivity is one of the most important properties for these materials and it can be evaluated by adsorption of proteins and by hydroxyapatite formation on the surface in simulated body fluid (SBF). The aim of this work was to evaluate the bioactivity of ceramic granules with various hydroxyapatite (HAp) and beta tricalcium phosphate (β-TCP) ratios by adsorption of bovine serum albumin (BSA) in SBF and phosphate saline buffer (PBS) solution. The highest adsorption capacity in both solutions was observed for biphasic calcium phosphate sample with HAp/β-TCP ratio 50/50 but the lowest – for sample 10/90. The adsorption capacity of all samples was more than 2 times higher in SBF media than in PBS. The possibility of hydroxyapatite formation was evaluated by changes of Ca2+ concentration in SBF. After 5 days of incubation at 37oC all samples showed a decrease in Ca2+ concentration.