Biomedical subjects

Jonathan C Knowles

Publications and source records attributed to Jonathan C Knowles.

At least 19 recordsLinked to original sources

PubMed2006

The biaxial flexural strength and fatigue property of Lava Y-TZP dental ceramic.

OBJECTIVES: The development of yttrium oxide partially stabilized zirconia (Y-TZP) has allowed the use of ceramic in load-bearing sites. The aim of this study was to evaluate and compare the biaxial flexural strength, hardness and fatigue life of colored and uncolored zirconia in the LAVAtrade mark system. MATERIALS AND METHODS: Eight groups (n=30) of standardized disc specimens (15mmx1.3mm) were used to examine the biaxial flexural strength (ISO 6872 standard) using a Dartec HC10 Fatigue Tester (Zwick Ltd., UK) and Vickers hardness was also measured. The uncolored, FS4, FS7 groups were also submitted to dynamic fatigue testing to produce stress-number curves. The strength reliability was analyzed using Weibull distribution. RESULTS: All groups had a mean biaxial flexural strength, hardness and Weibull modulus (m) of approximately 1100MPa, 1300HV and 9.8-12.9, respectively. One-way analysis of variance (ANOVA) showed no significant difference in biaxial flexural strength among the eight groups (p>0.05). Two-way ANOVA showed no significant differences in hardness values among groups except FS1 and FS5 which had significantly higher hardness values than FS4 and FS7 (p<0.001) and FS5 also had a higher hardness value than FS3 (p<0.05). Additionally, uncolored, FS4 and FS7 survived at 5x10(5) cycles at a stress level in the range of 60-65% of the mean biaxial flexural strength. CONCLUSION: There was no difference in flexural strength of uncolored and colored Y-TZP ceramic. The fatigue limit of uncolored, FS4 and FS7 zirconia may be defined as lying between 60 and 65% of the stress to failure.

Analysis of Variance↗

PubMed2006

Initial responses of human osteoblasts to sol-gel modified titanium with hydroxyapatite and titania composition.

Sol-gel thin films of hydroxyapatite (HA) and titania (TiO(2)) have received a great deal of attention in the area of bioactive surface modification of titanium (Ti) implants. Sol-gel coatings were developed on Ti substrates of pure HA and TiO(2) and two composite forms, HA+10% TiO(2) and HA+20% TiO(2), and the biological properties of the coatings were evaluated. All the coating layers exhibited thin and homogeneous structures and phase-pure compositions (either HA or TiO(2)). Primary human osteoblast cells showed good attachment, spreading and proliferation on all the sol-gel coated surfaces, with enhanced cell numbers on all the coated surfaces relative to uncoated Ti control at day 1, as observed by MTT assay and scanning electron microscopy. Cell attachment rates were also enhanced on the pure HA coating relative to control Ti. The pure HA and HA+10% TiO(2) composite coating furthermore enhanced proliferation of osteoblasts at 4 days. Moreover, the gene expression level of several osteogenic markers including bone sialoprotein and osteopontin, as measured by RT-PCR at 24h, was shown to vary according to coating composition. These findings suggest that human primary bone cells show marked and rapid early functional changes in response to HA and TiO(2) sol-gel coatings on Ti.

Cell Proliferation↗

PubMed2006

Surface characterisation of various bone cements prepared with functionalised methacrylates/bioactive ceramics in relation to HOB behaviour.

This study reports the relationship between the biocompatibility and surface properties of experimental bone cements. The effect of hydroxyapatite (HA) or alpha-tri-calcium phosphate (alpha-TCP) incorporated into bone cements prepared with methyl methacrylate as base monomer and either methacrylic acid or diethyl amino ethyl methacrylate (DEAEMA) as comonomers was investigated. The in vitro biocompatibility of these composite cements was assessed in terms of the interaction of primary human osteoblasts grown on the materials over a period of 5 days and compared with a control surface. These results were related to the surface properties investigated through a number of techniques, namely Fourier transform infrared, contact angle measurements, X-ray photoelectron spectroscopy and energy dispersive analysis of X-rays. Complementary techniques of thermal analysis and ion chromatography were also performed. Biocompatibility results showed that the addition of alpha-TCP improves biocompatibility regardless of comonomer type. This is in contrast to HA-based cements where cell proliferation was significantly lower. Surface characterisations showed that structural integrity of the materials was maintained in the presence of the acid and base comonomers, and water contact angles were reduced particularly in DEAEMA containing materials. Furthermore, ion chromatography confirmed higher Ca2+ and PO4(3-) ion release by both types of ceramics, particularly for those containing DEAEMA. In conclusion, the incorporation of acidic and basic comonomers to either HA or alpha-TCP ceramics containing bone cements can have differential effects upon the attachment and proliferation of bone cells in vitro. Moreover, those cements consisting of alpha-TCP and containing DEAEMA comonomer indicated the most favourable biocompatibility.

Biocompatible Materials↗

PubMed2005

The nucleation and crystallization of fine grained leucite glass-ceramics for dental applications.

OBJECTIVES: The aims of the study were to control the nucleation and crystal growth of selected aluminosilicate glass powders, to produce uniform leucite glass-ceramic microstructures consisting of fine (<1000 nm) grained leucite crystals. METHODS: A starting glass composition of wt%; 64.2% SiO(2), 16.1% Al(2)O(3), 10.9% K(2)O, 4.3% Na(2)O, 1.7% CaO, 0.5% LiO(2) and 0.4% TiO(2) was heated in an electric furnace and later quenched to produce glasses. The glass powders were ball milled to two different particle sizes and heat-treated using one and two-step crystallization heat treatments. Dta, Xrd, and Sem analyses was used to characterise and explore the crystallization kinetics of the glasses. RESULTS: Selected heat treatments of the glass powders produced a uniform distribution of fine tetragonal leucite crystals (mean+/-S.D.) 0.1+/-0.2 microm(2) in the glassy matrix, with minimal matrix microcraking in the glass-ceramics produced. The addition of a two-step heat treatment increased the leucite volume fraction in all instances. SIGNIFICANCE: Selected crystallization heat treatments and powder particle sizes were used to control the leucite crystal size, distribution and volume fraction, in order to produce uniformly distributed ultra fine grained tetragonal leucite glass-ceramics for dental applications.

Aluminum Silicates↗

PubMed2005

Sol-gel-modified titanium with hydroxyapatite thin films and effect on osteoblast-like cell responses.

Titanium (Ti) surface was coated with hydroxyapatite (HA) films via the sol-gel method. The coating properties, such as crystallinity and surface roughness, were controlled and their effects on the osteoblast-like cell responses were investigated. The film crystallinity was controlled with different heat treatment temperatures (400, 500, and 600 degrees C): Also the surface roughness was changed by using different heating rates (1 and 50 degrees C/min). The obtained sol-gel films had a dense and homogeneous structure with a thickness about 1 mum. The film heat-treated at higher temperature had enhanced crystallinity (600>500>>400 degrees C), while retaining similar surface roughness. When heat-treated rapidly (50 degrees C/min), the film became quite rough, with roughness parameters being much higher (4-6 times) than that obtained at a low heating rate (1 degrees C/min). The dissolution rate of the film decreased with increasing crystallinity (400>>500>600 degrees C), and the rougher film had slightly higher dissolution rate. The attachment, proliferation, and differentiation behaviors of human osteosarcoma HOS TE85 cells were affected by the properties of the films. On the films with higher crystallinity (heat treated over 500 degrees C), the cells attached and proliferated well and expressed alkaline phosphatase (ALP) and osteocalcin (OC) to a higher degree as compared to the poorly crystallized film (heat treated at 400 degrees C). On the rough film, the cell attachment was enhanced, but the ALP and OC expression levels were similar as compared to the smooth films.

Cell Line↗

PubMed2005

Influence of casting methods on marginal and internal discrepancies of complete cast crowns.

The relationship between the application of die-spacer prior to wax pattern fabrication and metal removal from the inner surface of the casting on marginal and internal discrepancies of complete cast crowns was evaluated. One hundred and twenty complete crowns were cast with palladium-silver alloy melted by gas-oxygen torch or electrical resistance and cast with a centrifuge casting machine. After casting, the crowns were seated on each type of different marginal configuration dies (90-degree shoulder, 20-degree beveled shoulder, and 45-degree chamfered shoulder) with a static load of 90 N during 1 min. Evaluation of the marginal fit of the specimens was made using a digital micrometer. The crowns were embedded in acrylic resin and longitudinally sectioned to verify the internal discrepancy that occurred in lateral and occlusal interfaces with a digital micrometer. The data were submitted to ANOVA and Tukey's test with a significance level of 5%. The best marginal and inner fits were obtained with the gas-oxygen torch source. The 45-degree chamfered shoulder showed the best marginal and inner fit, and better internal relief was obtained in the crowns abraded with 50 microm Al2O3 particles.

Analysis of Variance↗

PubMed2005

Mechanical performance and osteoblast-like cell responses of fluorine-substituted hydroxyapatite and zirconia dense composite.

A fluorine-substituted hydroxyapatite (FHA) and zirconia (ZrO(2)) dense composite (50:50 by volume) was fabricated, and its feasibility for hard tissue applications was investigated in terms of its mechanical properties and osteoblast-like cell (MG63) responses in vitro. The incorporation of fluorine into the hydroxyapatite (HA) structure was highly effective in producing a completely dense apatite-ZrO(2) composite through a pressureless sintering route, by preventing the thermal degradation of the apatite and ZrO(2). The resultant FHA-ZrO(2) dense composite had excellent mechanical properties, such as flexural strength (310 MPa), fracture toughness (3.4 MPam(1/2)), hardness (10 GPa), and elastic modulus (160 GPa). The flexural strength and fracture toughness of the composite showed a noticeable improvement by a factor of approximately 4 with respect to the pure apatites (HA and FHA). The MG63 cellular responses to the composite were assessed in terms of the cell proliferation (cell number and [(3)H]-thymidine incorporation) and differentiation (alkaline phosphatase activity, osteocalcin, and collagen production). The cells on the FHA-ZrO(2) composite spread and grew well, and proliferated actively during the culture period. The expression of alkaline phosphatase, osteocalcin, and collagen by the cells on the composite showed a similar trend to that on the pure apatites, although slight down-regulations were observed, implying that the FHA-ZrO(2) 50:50 composite retains the osteoblastic functionality and traits of the pure HA ceramics to a high degree. This finding, in conjunction with the considerable improvements in mechanical properties, supports the extended use of this composite for hard tissue applications.

Biocompatible Materials↗

PubMed2005

Hydroxyapatite and gelatin composite foams processed via novel freeze-drying and crosslinking for use as temporary hard tissue scaffolds.

Hydroxyapatite (HA) and gelatin composites were fabricated in a foam type via a novel freeze-drying and crosslinking technique. The morphological and mechanical properties of and in vitro cellular responses to the foams were investigated. The HA powder was added at up to 30 wt % into the gelatin solution, and the mixtures were freeze-dried and further crosslinked. The pure gelatin foam had a well-developed pore configuration with porosity and pore size of approximately 90% and 400-500 microm, respectively. With HA addition, the porosity decreased and pore shape became more irregular. The HA particulates, in sizes of about 2-5 microm, were distributed within the gelatin network homogeneously and made the framework surface rougher. All the foams had high water absorption capacities, showing typical hydrogel characteristics, even though the HA addition decreased the degree of water absorption. The HA addition made the foam much stronger and stiffer (i.e., with increasing HA amount the foams sustained higher compressive stress and had higher elastic modulus in both dry and wet states). The osteoblast-like human osteosarcoma cells spread and grew actively on all the foams. The cell proliferation rate, quantified indirectly on the cells cultured on Ti discs coated with gelatin and gelatin-HA composites using MTT assay, exhibited an up-regulation with gelatin coating compared with bare Ti substrate, but a slight decrease on the composite coatings. However, the alkaline phosphatase activities expressed by the cells cultured on composites foams as well as their coatings on Ti discs were significantly enhanced compared with those on pure gelatin foam and coating. These findings suggest that the gelatin-HA composite foams have great potential for use as hard tissue regeneration scaffolds.

Animals↗

PubMed2005

Hydroxyapatite and titania sol-gel composite coatings on titanium for hard tissue implants; mechanical and in vitro biological performance.

Hydroxyapatite (HA) composites with titania (TiO2) up to 30 mol % were coated on a titanium (Ti) substrate by a sol-gel route, and the mechanical and biological properties of the coating systems were evaluated. Using polymeric precursors, highly stable HA and TiO2 sols were prepared prior to making composite sols and coatings. Coatings were produced under a controlled spinning and heat treatment process. Pure phases of HA and TiO2 were well developed on the composites after heat treatment above 450 degrees C. The HA-TiO2 composite coating layers were homogeneous and highly dense with a thickness of about 800-900 nm. The adhesion strength of the coating layers with respect to Ti substrate increased with increasing the TiO2 addition. The highest strength obtained was as high as 56 MPa, with an improvement of about 50% when compared to pure HA (37 MPa). The osteoblast-like cells grew and spread actively on all the composite coatings. The proliferation and alkaline phosphatase (ALP) activity of the cells grown on the composite coatings were much higher than those on bare Ti, and even comparable to those on pure HA coating. Notably, the HA-20% TiO2 composite coating showed a significantly higher proliferation and ALP expression compared to bare Ti (p < 0.05). These findings suggest that the sol-gel-derived HA-TiO2 composite coatings possess excellent properties for hard tissue applications from the mechanical and biological perspective.

Alkaline Phosphatase↗

PubMed2005

Degradation and drug release of phosphate glass/polycaprolactone biological composites for hard-tissue regeneration.

Phosphate-based glass (P-glass) and poly(epsilon-caprolactone) (PCL) composites were fabricated in a sheet form by solvent extraction and thermal pressing methods, and the antibiotic drug Vancomycin was loaded within the composites for use as a hard-tissue regenerative. The degradation and drug-release rate of the composites in vitro were tailored by modifying the glass composition: 0.45 P(2)O(5)-x CaO-(0.55-x)Na(2)O, where x=0.2, 0.3, 0.4, and 0.5. Compared to pure PCL, all the P-glass/PCL composites degraded to a higher degree, and the composite with lower-CaO glass showed a higher material loss. This was attributed mainly to the dissolution of the glass component. The glass dissolution also increased the degradation of PCL component in the composites. The Vancomycin release from the composites was strongly dependent on the glass composition. Drug release in pure PCL was initially abrupt and flattened out over a prolonged period. However, glass/PCL composites (particularly in the glass containing higher-CaO) exhibited a reduced initial burst and a higher release rate later. Preliminary cell tests on the extracts from the glass/PCL composites showed favorable cell proliferation, but the level was dependent on the ionic concentration of the extracts. The cell proliferation on the diluted extracts from the composite with higher-CaO glass was significantly higher than that on the blank culture dish. These observations confirmed that the P-glass/PCL composites are potentially applicable for use as hard-tissue regeneration and wound-healing materials because of their controlled degradation and drug-release profile as well as enhanced cell viability.

Biocompatible Materials↗

PubMed2005

Porous scaffolds of gelatin-hydroxyapatite nanocomposites obtained by biomimetic approach: characterization and antibiotic drug release.

Gelatin-hydroxyapatite (HA) nanocomposite porous scaffolds were fabricated biomimetically, and their feasibility as a drug-delivery carrier for tissue-regeneration and wound-healing treatments was addressed. The composite sols were prepared by the precipitation of HA up to 30 wt % within a gelatin solution with the use of calcium and phosphate precursors, and the porous scaffold was obtained by casting the sols and further freeze drying. The obtained bodies were crosslinked with carbodiimide derivatives to retain chemical and thermal integrity. The apatite precipitates were observed to be a poorly crystallized carbonate-substituted HA. The nanocomposite scaffolds had porosities of approximately 89-92% and exhibited a bimodal pore distribution, that is, the macropores (approximately 300-500 microm) of the framework structure, and micropores (approximately 0.5-1 microm) formed on the framework surface. Transmission electron microscopy (TEM) observation revealed the precipitation of highly elongated HA nanocrystals on the gelatin network. The well-developed porous structure and organized nanocomposite configurations were in marked contrast to the directly mixed gelatin-HA powder conventional composites. For drug-release tests, tetracycline, an antibiotic drug, was entrapped within the scaffold, and the drug-release profile was examined with processing parameters, such as HA amount in gelatin, crosslinking degree, and initial drug addition. The drug entrapment decreased with increasing HA amount, but increased with increasing crosslinking degree and initial drug addition. The crosslinking of the gelatin was the prerequisite to sustaining and controlling the drug releases. Compared to pure gelatin, the gelatin-HA nanocomposites had lower drug releases, because of their lower water uptake and degradation. All the nanocomposite scaffolds released drugs in proportion to the initial drug addition, suggesting their capacity to deliver drugs in a controlled manner. Based on the findings of the well-developed morphological feature and controlled drug-release profile, the gelatin-HA nanocomposite porous scaffolds are suggested to be potentially useful for hard-tissue regeneration.

Anti-Bacterial Agents↗

PubMed2005

Hydroxyapatite porous scaffold engineered with biological polymer hybrid coating for antibiotic Vancomycin release.

The purpose of this study is to improve hydroxyapatite (HA) porous scaffolds via coating with biological polymer-HA hybrids for use as wound healing and tissue regeneration. Highly porous HA scaffolds, fabricated by a polyurethane foam reticulate method, were coated with hybrid coating solution, consisting of poly(epsilon-caprolactone) (PCL), HA powders, and the antibiotic Vancomycin. The PCL to HA ratio was fixed at 1.5 and the drug amounts were varied [drug/(PCL + HA) = 0.02 and 0.04]. For the purpose of comparison, bare HA scaffold without the hybrid coating layer was also loaded with Vancomycin via an immersion-adsorption method. The hybrid coating structure and morphology were observed with Fourier transformed infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The effects of the hybrid coating on the compressive mechanical properties and the in vitro drug release of the scaffolds were investigated in comparison with bare HA scaffold. The PCL-HA hybrid coating altered the scaffold pore structure slightly, resulting in thicker stems and reduced porosity. With the hybrid coating, the HA scaffold responded to an applied compressive stress more effectively without showing a brittle failure. This was attributed to the shielding and covering of the framework surface by the coating layer. The encapsulated drugs within the coated scaffold was released in a highly sustained manner as compared to the rapid release of drugs directly adsorbed on the pure HA scaffold. These findings suggest that the coated HA scaffolds expand their applicability in hard tissue regeneration and wound healing substitutes delivering bioactive molecules.

Anti-Bacterial Agents↗

PubMed2005

Effect of glass composition on the degradation properties and ion release characteristics of phosphate glass--polycaprolactone composites.

A series of polycaprolactone and ternary-based (Na(2)O)(0.55-x)(CaO)(x)(P(2)O(5))(0.45) glass composites were created, each containing 20% volume percentage of glass with various calcium compositions. A short-term degradation study was carried out to investigate the physical and ion release behaviour of these composites, utilising analytical techniques such as dynamical mechanical analysis, and ion chromatography. All the composites experienced significant loss of weight and stiffness throughout the study, with the 24 mol% calcium composites losing the greatest amount of weight and stiffness. The pH profile of the aqueous solutions in which the composites were placed were initially acidic, but began to neutralise mid-way through the study, with the 36 mol% solution achieving the most acidic conditions. The ion release behaviour mirrored the mass loss behaviour of the glass component of the composites. The cations (sodium and calcium ions) release was comparable with the initial stages of composite mass degradation, both of which exhibited almost immediate release when placed into solution. The 24 mol% composites underwent rapid rates of cation release, while the 36 mol% experienced the slowest rates of release. By contrast, anion (phosphates and polyphosphates) release showed a dissimilar trend, with rapid release of the P(2)O(7) and P(3)O(10) occurring during the first few hours in solution, whilst the P(3)O(9) structure released steadily during the first 48 h in solution. Finally, PO(4) release was at a constant rate over the duration of the study, releasing up to 300 ppm from the 32 and 36 mol% samples by the end of 200 h. To summarise, these results show that by combining phosphate glasses with biodegradable polymer, it is possible to create composites whose rate of degradation can be controlled to meet the needs of their end application.

Absorbable Implants↗

PubMed2005

Effect of fluoridation of hydroxyapatite in hydroxyapatite-polycaprolactone composites on osteoblast activity.

Fluorine was administered to a system of hydroxyapatite (HA)/polycaprolactone (PCL) ceramic-polymer bioactive composites for applications as hard tissue regeneratives. The HA was fluoridated at different levels (5%, 25%, 50% and 75%) in order to produce the fluor-hydroxyapatite (FHA)/PCL composites. The osteoblastic cellular responses to the composites were examined in terms of the cell attachment, proliferation and differentiation as well as the expression of bone-associated genes. The amount of fluorine released from the composites was controlled by changing the degree of fluoridation, and the cellular responses were strongly influenced by the level of fluoridation. The MG63 cells on the FHA-PCL attached and proliferated at a similar level to those on HA-PCL. However, the fluoridation of HA increased significantly the alkaline phosphatase (ALP) activity and osteocalcin (OC) production by the cells on the composites, which was measured by an enzymatic assay. Moreover, the gene expression level of ALP and OC in the cells was up regulated on the FHA-PCL, which was confirmed semi-quantitatively by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. These findings on the fluorine-administered biological composites (FHA-PCL) suggested that fluorine plays a significant role in stimulating the bone derived cellular activity, and the FHA-PCL composites have high potential for use as hard tissue regeneratives.

Body Fluids↗

PubMed2005

The crystallization of an aluminosilicate glass in the K2O-Al2O3-SiO2 system.

OBJECTIVES: The aims of the study were to explore the nucleation and crystallization kinetics of an aluminosilicate glass in K2O-Al2O3-SiO2 system and to characterize it. OBJECTIVES: A starting glass composition of wt%; 64.2% SiO2, 16.1% Al2O3, 10.9% K2O, 4.3% Na2O, 1.7% CaO, 0.5% LiO and 0.4% TiO2 was heated in an electric furnace and later quenched to produce glasses. The glass powders were heat treated using differing heat treatment schedules and quenched. Dta, Xrd, Eds and Sem analyses were used to characterize and explore the crystallization kinetics of the glasses. RESULTS: Phase separation of the glasses was identified and characterized in the glasses. Tetragonal leucite, cubic leucite and sanadine glass-ceramics were produced. Fine leucite crystals (1 microm2) were crystallized with minimal matrix microcracking. SIGNIFICANCE: Amorphous phase separation appeared to be an important precursor to nucleation and crystal growth in the alkali aluminosilicate glasses explored. It was possible to control the crystallization of tetragonal leucite and sanidine phases by selected heat treatment of glass powders and monoliths, resulting in the production of fine grained tetragonal leucite glass-ceramics.

Aluminum Oxide↗

PubMed2004

Hydroxyapatite and fluor-hydroxyapatite layered film on titanium processed by a sol-gel route for hard-tissue implants.

A double-layered coating, consisting of a hydroxyapatite (HA) outer film and a fluor-hydroxyapatite (FHA) inner film, was produced on a Ti substrate by a sol-gel route to improve the biocompatibility and functionality of the system. Dissolution behavior of and in vitro cellular responses to the layered film were investigated. Calcium nitrate and triethyl phosphite were used for calcium and phosphate precursors, respectively, and ammonium fluoride was added as a fluorine-ion source for FHA. The FHA layer was deposited on Ti by spin coating and subsequent heat treatment at 550 degrees C for 30 min in air, and then the HA layer was laid down over the FHA-coated Ti under the same conditions. After heat treatment, characteristic apatite structures and phases were developed on both FHA and HA films. The cross-section view of the HA/FHA film clearly showed a double-layered structure on Ti with each layer approximately 0.6-0.8-microm thickness. The coating layer was highly uniform and dense, and adhered to Ti substrate strongly with an adhesion strength of about 40 MPa. The in vitro solubility of the HA/FHA layered film in a physiological solution was between that of HA and FHA pure film, and the dissolution profile was quite biphasic, that is, an initial rapid period and a slowdown with increasing time, reflecting the gradient solubility of the fast HA outer structure/slow FHA inner structure. The human osteoblast-like HOS TE85 cells cultured on the HA/FHA layered film attached, spread, and grew favorably. The proliferation rate of the cells on the layered film was significantly higher (considered at p < 0.05 for n = 6) than that on Ti substrate and was similar to that on pure HA film. The alkaline phosphatase (ALP) activity and osteocalcin (OC) produced by the cells on the layered film were significantly higher (considered at p < 0.05 for n = 6) than those on Ti substrate. Moreover, the ALP and OC levels of cells on the layered film showed the trends of HA outer/FHA inner structure with respect to culture period, that is, HA initially and FHA later. These observations suggest that the HA/FHA layered film on Ti obtained by a sol-gel route possesses gradient functionality in terms of solubility and cellular responses, and find that those parameters can be tailored for specific use in hard-tissue implants.

Biocompatible Materials↗

PubMed2004

Effect of biphasic calcium phosphates on drug release and biological and mechanical properties of poly(epsilon-caprolactone) composite membranes.

Poly(epsilon-caprolactone) (PCL) and biphasic calcium phosphate (CaP) composite membranes were prepared for use in tissue regeneration by a novel solvent casting-pressing method. An antibiotic drug, tetracycline hydrochloride (TCH), was entrapped within the membranes to investigate the efficacy of the material as a drug delivery system. The CaP powders were varied in amount (0-50 wt %) and in powder characteristics by heat treating at different temperatures, and their effects on the mechanical and biological properties and drug release of the membranes were examined. With CaP addition up to 30 wt %, the elastic modulus of the membranes was enhanced much due to the rigidity of CaP. While the tensile strength and elongation rate decreased gradually with CaP addition because the CaP powders acted as a failure source. The osteoblast-like cells cultured on the CaP-PCL composite membranes exhibited significant improvements in proliferation and alkaline phosphatase (ALP) activity compared to pure PCL and culture plastic control, indicating excellent cell viability and functional activity. The TCH drugs were released from the PCL and CaP-PCL membranes in a similar fashion; an initial burst followed by a reduced release rate. The initial burst effect diminished much by the addition of CaP powders. The CaP addition increased the drug release rate after an initial period, and this was attributed to the high water uptake capacity and dissolution of the CaP containing membranes. Compared to the composite membranes containing heat-treated CaP powders, those with as-precipitated ones had higher dissolution and drug releases. These observations on mechanical properties and cellular responses as well as on drug release profiles suggested that the CaP-PCL composite membranes are potentially applicable to tissue regeneration and drug delivery system.

Animals↗

PubMed2004

Hard-tissue-engineered zirconia porous scaffolds with hydroxyapatite sol-gel and slurry coatings.

A zirconia (ZrO(2)) porous scaffold was coated with a gradient apatite layer to induce osteoconductivity with the use of a combination of sol-gel and powder slurry methods. The ZrO(2) was used to impart mechanical strength and the apatite layer was coated for functional biocompatibility. The coating layer, from the outside in, was composed of sol-gel hydroxyapatite (HA)/slurry HA/slurry FA. The sol-gel coating powder had a lower crystallinity than the slurry coating powder. The sol-gel HA coating over the HA/FA slurry coating layer made the surface very smooth. The sol-gel coating over the slurry coating layer enhanced the bonding strength up to 33 MPa. The dissolution rate of the sol-gel/slurry coating layer was much higher than that of the slurry coating. Moreover, the rate could be controlled by altering the heat-treatment temperature of the sol-gel HA layer. The MG63 cells cultured on these materials grew and spread in a different manner, depending on the coating layer. However, the proliferation rates of the cells on both coating systems were not much different.

Biocompatible Materials↗