Hydroxyapatite-collagen Composite Research Articles

Study on Anhydrous Proton Conduction in Imidazole–Collagen Composite

Recently, hydrogen-fuel cells have attracted attention as an environmentally friendly next-generation energy device. Very recently, biomaterials such as collagen and chitin have realized proton conductivity via water bridges under humidity condition, and the fabrication of fuel cells using biomaterials is possible. However, the fuel cell electrolyte via water has demerits, such as the complication of fuel cell instruments and the operating temperature limit. Therefore, fuel cell electrolytes without humidified conditions are desired. In the present work, we have synthesized an anhydrous proton conductor using imidazole and collagen, which are biomaterials, and investigated the anhydrous proton conductivity in imidazole–collagen composites. It was found that an imidazole–collagen composite is a high-proton conductor above 10−3 S/m and above 200 °C without the humidified condition compared with other anhydrous bio-proton conductors such as the hydroxyapatite–collagen composite. Moreover, the motional narrowing of the 1H-NMR line width reveals that the proton conductivity is realized in the temperature region from 120 to 200 °C. In addition, the DTA measurement and the impedance analyses reveal that the imidazole–collagen composite film undergoes the phase transition at 120 °C. Furthermore, the proton conductivity in the imidazole–collagen composite strongly depends on n, which is the imidazole concentration per collagen molecule and takes a maximum at n = 2.0. In addition, the proton conductivity perpendicular to the collagen fiber is approximately ten times higher than that parallel to the collagen fiber. From these results, it can be deduced that the proton conductivity in the imidazole–collagen composite is caused by breaking and rearranging the hydrogen bonds of the collagen side chain with the imidazole molecule formed between the collagen fibers.

Local Suppression Effect of Paclitaxel-Impregnated Hydroxyapatite/Collagen on Breast Cancer Bone Metastasis in a Rat Model

Introduction Breast cancer is one of the most frequent primary tumors that cause spinal metastases. Metastasis consequences impair both the patient's overall prognosis and quality of life. We previously developed a porous hydroxyapatite collagen composite (HAp/Col) as an osteoconductive scaffold. HAp/Col is a commercially available artificial bone that is frequently utilized in spinal fusion. Because of its high absorbance capacity, HAp/Col is regarded as a good chemical carrier. Methods This study investigated the effect of local administration of paclitaxel combined with HAp/Col scaffold on breast cancer metastasis. High-performance liquid chromatography was used to assess the in vitro release of paclitaxel from HAp/Col. In an in vivo rat model, the inhibitory effects of paclitaxel-impregnated scaffolds on local osteogenesis was examined, and then the local suppression effects on metastatic cancer were investigated. Results In vitro testing revealed that roughly 30% of the paclitaxel was released within 96 hours. Paclitaxel-impregnated HAp/Col inhibited local osteogenesis for the first 8 weeks in a rat femur. However, at 12 weeks following surgery, this negative effect appeared to have subsided. In the metastatic model, all rats in the control group reached the humane endpoint 14 days after surgery. On the other hand, the average time to the endpoint in the paclitaxel group was 26.5 days, which was substantially longer than that in the control group. Long-term survivors treated with paclitaxel had no remaining tumor cells in the femoral bone, and osteogenesis was seen surrounding the HAp/Col. Conclusions Paclitaxel-impregnated HAp/Col reduced local tumor development and extended the time to the target endpoint in rats with metastases from breast cancer. This study shows that local implantation of paclitaxel-impregnated HAp/Col may be a viable therapeutic option for the management of breast cancer metastases.

Evaluation of Autologous Bone Marrow Concentrate along with Hydroxyapatite-collagen for Management of Long Bone Fracture in Canines

Background: Fractures are a major concern in Veterinary orthopedic surgery because they are often complicated into non unions. The present study was planned to evaluate the fracture healing by using hydroxyapatite-collagen (HAp-Col) as a bone graft substitute and autologous bone marrow concentrate, after the internal fixation by titanium elastic pin. Method: The present work was conducted on 12 clinical cases of dogs having diaphyseal fracture of long bones. In group I (6 animals) fractures were immobilized by an internal fixation technique. In group II fracture was immobilized as in group I with use of autologous bone marrow concentrate along with Hydroxyapatite-collagen at the fracture site. The weight bearing and the progress of fracture healing were recorded. Result: Study showed early weight bearing and no observable lameness in group II as compared to group I animals. Fracture union was earlier and with minimum periosteal callus formation in one animal, five animals at 45 days and 60 days respectively while in group I fracture healing was observed in one animal, two animals at 60 day and 90 days respectively. On basis of result, it is concluded that Hydroxyapatite-collagen composite can be used as along with autolologus bone marrow concentrate as alternative therapy to bone graft in clinical cases to enhance the fracture healing. The use of autogenous and allogenic bone graft having some advantages which is overcome by this present technique.

Biocompatibility and osteoconductivity of scaffold porous composite collagen–hydroxyapatite based coral for bone regeneration

AbstractThe synthesis of collagen–hydroxyapatite composites has been carried out, and the biocompatibility and osteoconductivity properties have been tested. This research was conducted to determine the ability of hydroxyapatite–collagen composites to support the bone growth through the graft surface. Hydroxyapatite used in this study was synthesized from coral with a purity of 96.6%, while collagen was extracted from the chicken claw. The process of forming a scaffold of collagen–hydroxyapatite composites was carried out using the freeze-drying method at −80°C for 4 h. The biocompatibility characteristics of the sample through the cytotoxicity tests showed that the percentage of viable cells in collagen–hydroxyapatite biocomposite was 108.2%, which is higher than the percentage of viable cells of hydroxyapatite or collagen material. When the viable cell is above 100%, collagen–hydroxyapatite composites have excellent osteoconductivity as a material for bone regeneration.

Hydroxyapatite-Collagen Composite Made from Coral and Chicken Claws for Bone Implant Application

Synthesis of porous hydroxyapatite-collagen composites for bone implant applications has been carried out. Hydroxyapatite synthesized from coral by the precipitation method, while Collagen synthesized from chicken claws. Collagen formation was carried out by freeze-dry technique with variations in freezing time of 2, 4 and 6 hours at -80 ° C. The next process was by drying in a lyophilizer. Characterization of samples was carried out using Fourier Transform Infra Red (FTIR), Scanning Electron Microscopy (SEM), compressive strength test and cytotoxicity test with Microtetrazolium (MTT) assay. FTIR results proved that collagen uptake and hydroxyapatite combine chemically. This is indicated by the absorption of functional groups that did not coincide between collagen and hydroxyapatite functional groups with composites. SEM observations showed that the largest pore size was obtained at freezing for 2 hours which was 774 μm and the smallest in freezing for 6 hours was 640 μm. This pore size was an important parameter of the bone implant because it played a role in the osteoinductive process. The composite compressive strength test results for freezing 2 hours, 4 hours and 6 hours respectively was 737 KPa, 842 KPa and 707.7 KPa. The results of the cytotoxicity test with MTT showed the percentage of cell viability above 100%. This means that the Hydroxyapatite-collagen composite is non-toxic. So, the sample formed has qualified as a bone implant candidate.

Promising Biomolecules.

The osteochondral defect (OD) comprises the articular cartilage and its subchondral bone. The treatment of these lesions remains as one of the most problematic clinical issues, since these defects include different tissues, requiring distinct healing approaches. Among the growing applications of regenerative medicine, clinical articular cartilage repair has been used for two decades, and it is an effective example of translational medicine; one of the most used cell-based repair strategies includes implantation of autologous cells in degradable scaffolds such as alginate, agarose, collagen, chitosan, chondroitin sulfate, cellulose, silk fibroin, hyaluronic acid, and gelatin, among others. Concerning the repair of osteochondral defects, tissue engineering and regenerative medicine started to design single- or bi-phased scaffold constructs, often containing hydroxyapatite-collagen composites, usually used as a bone substitute. Biomolecules such as natural and synthetic have been explored to recreate the cartilage-bone interface through multilayered biomimetic scaffolds. In this chapter, a succinct description about the most relevant natural and synthetic biomolecules used on cartilage and bone repair, describing the procedures to obtain these biomolecules, their chemical structure, common modifications to improve its characteristics, and also their application in the biomedical fields, is given.

Experimental study on advanced bone regeneration by BMP-7 derived-peptide chitosan nanometer hydroxyapatite collagen biomimetic composite

Objective: To investigate the effect of BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composite on repairing rat critical-sized cranial defects. Methods: The chitosan nanometer hydroxyapatite collagen composite was prepared and the microcosmic appearance of the composite was observed by scanning electron microscope. The BMP-7 derived-peptide was introduced into the composite by vacuum adsorption. The released peptide content from the scaffold was detected using high performance liquid chromatography at different set times. Critical-sized cranial defects were created on both sides of the parietal bone in 24 adult Sprague-Dawley rats. The BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composites were implanted on the right side as experimental group and the left side was implanted with chitosan nanometer hydroxyapatite biomimetic collagen composites alone as control group. The rats of both groups were killed in batch respectively after 6 and 12 weeks. Macroscopic observation, three-dimensional reconstruction of computed tomography (CT) and histological observation were performed on these samples. Results: The results of scanning electron microscope showed that the surface of the scaffold was porous. The releasing character of BMP-7 derived-peptide belonged to slow release. The result of animal experiment showed that the BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composite could more effectively promote the repair of cranial bone defects comparing with the chitosan nanometer hydroxyapatite biomimetic collagen composite alone. The difference was statistically significant ( p < .05). Conclusions: The BMP-7 derived-peptide chitosan nanometer hydroxyapatite collagen biomimetic composite can effectively promote bone regeneration of bone defects. The composite is a kind of ideal scaffold material for bone tissue engineering.

Experimental study on advanced bone regeneration by BMP-7 derived-peptide chitosan nanometer hydroxyapatite collagen biomimetic composite

Objective: To investigate the effect of BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composite on repairing rat critical-sized cranial defects. Methods: The chitosan nanometer hydroxyapatite collagen composite was prepared and the microcosmic appearance of the composite was observed by scanning electron microscope. The BMP-7 derived-peptide was introduced into the composite by vacuum adsorption. The released peptide content from the scaffold was detected using high performance liquid chromatography at different set times. Critical-sized cranial defects were created on both sides of the parietal bone in 24 adult Sprague-Dawley rats. The BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composites were implanted on the right side as experimental group and the left side was implanted with chitosan nanometer hydroxyapatite biomimetic collagen composites alone as control group. The rats of both groups were killed in batch respectively after 6 and 12 weeks. Macroscopic observation, three-dimensional reconstruction of computed tomography (CT) and histological observation were performed on these samples. Results: The results of scanning electron microscope showed that the surface of the scaffold was porous. The releasing character of BMP-7 derived-peptide belonged to slow release. The result of animal experiment showed that the BMP-7 derived-peptide chitosan nanometer hydroxyapatite biomimetic collagen composite could more effectively promote the repair of cranial bone defects comparing with the chitosan nanometer hydroxyapatite biomimetic collagen composite alone. The difference was statistically significant ( p < .05). Conclusions: The BMP-7 derived-peptide chitosan nanometer hydroxyapatite collagen biomimetic composite can effectively promote bone regeneration of bone defects. The composite is a kind of ideal scaffold material for bone tissue engineering.

Shearing in a Biomimetic Apatite-Protein Composite: Molecular Dynamics of Slip Zone Formation, Plastic Flow and Backcreep Mechanisms

We report molecular dynamics simulations of shear in a biomimetic hydroxyapatite-collagen composite. Our model exhibits elastic properties fully dominated by the inorganic component. However, beyond the elastic regime the biomolecules along with the hierarchical nature of the composite account for the formation of structure-inherent slip zones. These accommodate shear without compromising the overall structure and lead to the sliding of intrinsically defined rods at roughly constant restoring force. Upon releasing load, rod displacement is reversible and backcreep is observed as gradual ionic rearrangement in the slip zone, subjected to an activation barrier.

Hydroxyapatite-collagen composites. Part I: can the decrease of the interactions between the two components be a physicochemical component of osteoporosis in aged bone?

The interactions of Type I acid soluble collagen (Col) with both carbonate-free hydroxyapatite (HA(1100)) and carbonate-rich one (CHA) were investigated. The aim was to ascertain whether the increase of bone CO(3) (2-) with ageing could relate to the disease known as osteoporosis. HA(1100)-Col and CHA-Col composites with various ratios were prepared and examined. Scanning electron microscopy and differential scanning calorimetry showed a stronger adhesion of the Col matrix to the granules of HA(1100) than to those of CHA. FT-IR spectroscopy showed that with HA(1100) both multiple hydrogen bonds of Col peptide -NH groups with HA PO(4) (3-), and electrochemical interactions between Col peptide -C=O groups and HA Ca(2+) were present. In the presence of CO(3) (2-), the interactions between -NH and phosphate were diminished, and Ca(2+) interacted more strongly with CO(3) (2-) than with peptide -C=O, so causing a separation between the two components of the bone extra-cellular matrix. The results obtained strengthen the hypothesis that the substitution of PO(4) (3-) ions by CO(3) (2-) ions in the HA lattice might be a significant component of osteoporosis, although further investigation is needed.

Effects of increased collagen-matrix density on the mechanical properties and in vivo absorbability of hydroxyapatite–collagen composites as artificial bone materials

The aim of this study was to evaluate the effects of increased collagen-matrix density on the mechanical properties and in vivo absorbability of porous hydroxyapatite (HAp)–collagen composites as artificial bone materials. Seven types of porous HAp–collagen composites were prepared from HAp nanocrystals and dense collagen fibrils. Their densities and HAp/collagen weight ratios ranged from 122 to 331 mg cm−3 and from 20/80 to 80/20, respectively. The flexural modulus and strength increased with an increase in density, reaching 2.46 ± 0.48 and 0.651 ± 0.103 MPa, respectively. The porous composites with a higher collagen-matrix density exhibited much higher mechanical properties at the same densities, suggesting that increasing the collagen-matrix density is an effective way of improving the mechanical properties. It was also suggested that other structural factors in addition to collagen-matrix density are required to achieve bone-like mechanical properties. The in vivo absorbability of the composites was investigated in bone defects of rabbit femurs, demonstrating that the absorption rate decreased with increases in the composite density. An exhaustive increase in density is probably limited by decreases in absorbability as artificial bones.

Histologic study of incorporation and resorption of a bone cement–collagen composite: an in vivo study in the minipig

Calcium phosphates are clinically established as bone defect fillers. They have the capability of osseoconduction and are characterized by a slow resorption process. The present study evaluated the suitability of a newly developed calcium phosphate cement modified with collagen type I. The modified cement paste was inserted in differently designed defects of 10 minipigs. Further, an alveolar ridge augmentation was performed, applying the cement paste. The cement hardened in situ during the operation, forming a hydroxyapatite collagen composite. Animals were sacrificed after 1, 3, 6, 12, and 18 months. The tissue integration and resorption process was then evaluated using nondecalcified microsections. All animals were evaluated for histology. The implanted material showed osseoconductive characteristics. Resorption started from the edge of the defect zone, and bone substitution followed rapidly. Twelve months after placement of the cement, complete remodeling was observed. It can be concluded that the applied hydroxyapatite-collagen cement composite shows good resorption and bone integration.

Wear characteristic and biocompatibility of some hydroxyapatite–collagen composite acetabular cups

Both HDPE and UHMWPE have long been used successfully as socket materials in hip-joint replacements. Recently, however there are concerns over the adverse biological responses due to the wear debris of these polymers. Although a good deal of work to improve the performance of these polymers has been carried out a need still exists for an implant material with improved biocompatibility and mechanical properties. Hydroxyapatite–collagen composites have been prepared by precipitation of calcium phosphate on collagen in the past but very few of these attempts considered the mechanical strength of the composites that suits their realistic uses as implant material. Present work is an attempt to develop hybrid composites of hydroxyapatite–collagen–hyaluronic acid or gelatin with sufficient adherence to both hard and soft tissues and also with good cohesive strength leading to improved mechanical and biological properties. It was possible to prepare acetabular cups of the newly developed composites by compression moulding for tests on a hip-joint simulator. Pin specimens for tests on a pin-on-disc apparatus were also moulded with these composites. Tests with the acetabular cups and pin specimens indicate that some of the newly developed materials offer wear resistance comparable to those of the presently used socket materials. Biocompatibility tests with these materials show that their haemolysis counts are well below the acceptable range. Hydroxyapatite–collagen composites with 10% hyaluronic acid offer suitable mechanical strengths, good friction and wear characteristics and acceptable level of haemolysis and therefore the composite may be considered to be a potential socket material of future generation.

Biomimetic porous scaffolds with high elasticity made from mineralized collagen—An animal study

Histological investigations of a new hydroxyapatite-collagen composite material were carried out to evaluate its possible suitability as a bone substitute. The three-dimensional scaffolds made from biomimetically mineralized collagen exhibit an interconnecting pore structure and elastic mechanical properties. They were implanted into the subcutaneous tissue and bone defects made in the femur of rats and harvested with the surrounding tissue at 1, 2, 4, 8, and 12 weeks after surgery. The materials implanted in the subcutaneous tissue were covered by fibrous connective tissue with a slight inflammatory response, and many foreign-body giant cells were observed on the surface of the scaffolds. Most of the material implanted in the subcutaneous tissue was resorbed at 8 weeks by phagocytosis. In the bone defects, new bone formation was observed on the surface of the material at 1 week. New bone increased with time, and osteoclasts were seen on the surface of the scaffolds at 2 weeks. Resorption and replacement by new bone of many parts of the materials implanted in the femur were observed by 12 weeks. These responses occurred faster than those of other hydroxyapatite-collagen composites. The results suggested that the new biomimetically mineralized collagen scaffolds were suitable as an implant material for bone-tissue reconstruction.

Stability and cellular responses to fluorapatite–collagen composites

Fluorapatite (FA)–collagen composites were synthesized via a biomimetic coprecipitation method in order to improve the structural stability and cellular responses. Different amounts of ammonium fluoride (NH 4F), acting as a fluorine source for FA, were added to the precipitation of the composites. The precipitated composites were freeze-dried and isostatically pressed in a dense body. The added fluorine was incorporated nearly fully into the apatite structure (fluoridation), and a near stoichiometric FA–collagen composite was obtained with complete fluoridation. The freeze-dried composites had a typical biomimetic network, consisting of collagen fibers and precipitates of nano-sized apatite crystals. The human osteoblast-like cells on the FA–collagen composites exhibited significantly higher proliferation and differentiation (according to alkaline phosphatase activity) than those on the hydroxyapatite–collagen composite. These enhanced osteoblastic cell responses were attributed to the fluorine release and the reduced dissolution rate.

Hydroxyapatite–collagen–hyaluronic acid composite

The new composite biomaterial made from hydroxyapatite and collagen conjugated with hyaluronic acid has been studied. The structure evaluation of the composite showed more dense arrangement due to the formation of collagen–hyaluronic acid conjugate, and particles of inorganic component are closely anchored in the structure. Mechanical properties and model swelling of this composite are compared with properties of hydroxyapatite–collagen composite of similar material without hyaluronic acid. Higher cohesivity of the new biomaterial can give new possibilities for application as bone implant material. The test of contact cytotoxicity showed a very good biocompatibility of the biomaterial.

Management of the atrophic anterior maxilla by combined hydroxyapatite augmentation and vestibuloplasty: A pilot study

A technique is described to overcome the problem of the grossly resorbed maxillary alveolus and improve denture wear, by combining augmentation and increased soft tissue cover of the alveolar ridge. Manipulation and placement of the hydroxyapatite was facilitated by use of a hydroxyapatite/collagen composite (HAC) block. The procedure has been carried out in ten patients where extensive resorption contraindicated the use of permucosal implants. Six cases have been followed up for 2 to 3 years. After some initial compaction of HAC the improvement in ridge height has been maintained and long term improvement in denture function obtained.

The temperature dependence of the deformation of bone

The deformation characteristics of compact bone have been measured as a function of temperature in the range from −58 to 90°C. At temperatures below 25°C elastic, anelastic and plastic contributions to the strain could be distinguished. The Young's modulus increased as the temperature was reduced, while the nonelastic component was approximately independent of temperature. An interpretation of these results is made in terms of an idealised hydroxyapatite-collagen composite. At temperatures higher than 50°C the deformation was compounded by non-equilibrium recovery and an irreversible change in the structure of bone.