Nerve conduit based on HAP/PDLLA/PRGD for peripheral nerve regeneration with sustained release of valproic acid.

The nerve conduits have been developed for nerve defect repair. However, no artificial conduits have obtained comparable results to autografts to bridge the large gaps. A possible reason for this poor performance may be a lack of sustainable neurotrophic support for axonal regrowth. Previous studies suggested nanocomposite conduits can be used as a carrier for valproic acid (VPA), a common drug that can produce effects similar to the neurotrophic factors. Here, we developed the novel bioabsorbable conduits based on hydroxyapatite/poly d-l-lactic acid (PDLLA)/poly{(lactic acid)-co-[(glycolic acid)-alt-(l-lysine)]} with sustained release of VPA. Firstly, the sustained release of VPA in this conduit was examined by high-performance liquid chromatography. Then Schwann cells were treated with the conduit extracts. The cell metabolic activity and proliferation were assayed by 3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2-tetrazolium bromide and bromodeoxyuridine staining. A 10-mm segment of rat sciatic nerve was resected and then repaired, respectively, using the VPA conduit (Group A), the PDLLA conduit (Group B), or the autografts (Group C). Nerve conduction velocities (NCVs), compound muscle action potentials (CMAPs), and histological staining were assayed following the surgery. The cell metabolic activity and proliferation were significantly increased (p < .05) by the extracts from VPA-conduit extract compared to others. NCVs and CMAPs were significantly higher in Groups A and C than Group B (p < .05). The nerve density of Groups A and C was higher than Group B. There was no significant difference between Groups A and C. Taken together, this study suggested the sustained-release VPA conduit promoted peripheral nerve regeneration that was comparable to the autografts. It holds potential for future use in nerve regeneration.

Enhanced model protein adsorption of nanoparticulate hydroxyapatite thin films on silk sericin and fibroin surfaces.

Hydroxyapatite coated metallic implants favorably combine the required biocompatibility with the mechanical properties. As an alternative to the industrial coating method of plasma spraying with inherently potential deleterious effects, sol-gel methods have attracted much attention. In this study, the effects of intermediate silk fibroin and silk sericin layers on the protein adsorption capacity of hydroxyapatite films formed by a particulate sol-gel method were determined experimentally. The preparation of the layered silk protein/hydroxyapatite structures on glass substrates, and the effects of the underlying silk proteins on the topography of the hydroxyapatite coatings were described. The topography of the hydroxyapatite layer fabricated on the silk sericin was such that the hydroxyapatite particles were oriented forming an oriented crystalline surface. The model protein (bovine serum albumin) adsorption increased to 2.62 µg/cm2 on the latter surface as compared to 1.37 µg/cm2 of hydroxyapatite on glass without an intermediate silk sericin layer. The BSA adsorption on glass (blank), glass/c-HAp, glass/m-HAp, glass/sericin/c-HAp, and glass/sericin/m-HAp substrates, reported as decrease in BSA concentration versus contact time.

Difference in release kinetics of unwashed and washed platelet-released supernatants from bone substitute materials: the impact of platelet preparation modalities.

BACKGROUND AND OBJECTIVE: In regenerative dentistry, platelet preparations are applied to stimulate bone healing and periodontal regeneration. Here, we pursue a strategy where bone substitutes are used as carriers for platelet-released supernatants. The mitogenic capacity and release kinetics of loaded bone substitutes were assessed. MATERIAL AND METHODS: Platelet-released supernatants of washed platelets (washed PRS) and platelet-released supernatants of unwashed platelets (unwashed PRS) were lyophilized onto the bone substitutes deproteinized bovine bone mineral, hydroxyapatite and ß-tricalcium phosphate. Scanning electron microscopy images were taken. Supernatants of bone substitutes were collected at hours 1, 3, 6, 24, and 48 and medium was replaced. We evaluated the protein content with the bicinchoninic acid assay and the effect on proliferation using bioassays with human periodontal fibroblasts. Release of growth factors from the loaded bone substitutes was measured based on the platelet-derived growth factor isoform (PDGF-BB) and thrombin immunoassays. Furthermore, we assessed DNA and RNA content of washed PRS and unwashed PRS. RESULTS: Unwashed PRS showed higher total protein concentrations than washed PRS, while the concentration of PDGF-BB, thrombin, DNA, RNA and their mitogenic effect was not significantly different. The bone substitute materials adsorbed protein over time but no significant changes in overall appearance was found. Supernatants collected from unwashed PRS-loaded bone substitute after 1 h induced a potent mitogenic response in periodontal fibroblasts. This pro-mitogenic capacity of the supernatants decreased over the observation period. Supernatants of washed PRS-loaded bone substitutes did not induce a substantial mitogenic effect. Levels of PDGF-BB, thrombin and protein were higher in supernatants of unwashed PRS-loaded bone substitutes than of washed PRS-loaded bone substitutes. CONCLUSION: Bone substitutes loaded with unwashed PRS, but not bone substitutes loaded with washed PRS show continuously declining release kinetics. These data suggest that plasma components in platelet preparations can modify the release kinetics profile.

Cellular Uptake and Delivery-Dependent Effects of Tb3+-Doped Hydroxyapatite Nanorods.

With the increasing interest in hydroxyapatite (HA) nanostructures for use in biomedicine, the systematic evaluation of their potential effects on biological systems is becoming critically important. In this work, we report the in vitro cellular uptake, in vivo tissue distributions and toxicity of Tb3+-doped HA (HA-Tb) after short-, intermediate-, and long-term exposure. Transmission electron microscopy analysis indicated that HA-Tb was taken up by cells via vesicle endocytosis. Cell proliferation and cytotoxicity assay, combined with confocal laser scanning microscopy, indicated excellent cell viability with no changes in cell morphology at the examined doses. Three HA-Tb delivery methods (intraperitoneal, intragastric, and intravenous) resulted in similar time-dependent tissue distributions, while intraperitoneal injection produced the highest bioavailability. HA-Tb initially accumulated in livers and intestines of rats (4 h to one day after administration), then became increasingly distributed in the kidney and bladder (seven days), and finally decreased in all tissues after 30 to 90 days. No histopathological abnormalities or lesions related to treatment with HA-Tb were observed. These results suggest that HA-Tb has minimal in vitro and in vivo toxicity, regardless of the delivery mode, time, and dose. The findings provide a foundation for the design and development of HA for biological applications.

Remediation of lead contaminated soil by biochar-supported nano-hydroxyapatite.

In this study, a high efficiency and low cost biochar-supported nano-hydroxyapatite (nHAP@BC) material was used in the remediation of lead (Pb)-contaminated soil. The remediation effect of nHAP@BC on Pb-contaminated soil was evaluated through batch experiments. The stability, bioaccessibility of Pb in the soil and the change in soil characteristics are discussed. Furthermore, the effects of the amendments on the growth of cabbage mustard seedlings and the accumulation of Pb were studied. The results showed that the immobilization rates of Pb in the soil were 71.9% and 56.8%, respectively, after a 28 day remediation using 8% nHAP and nHAP@BC materials, and the unit immobilization amount of nHAP@BC was 5.6 times that of nHAP, indicating that nHAP@BC can greatly reduce the cost of remediation of Pb in soil. After the nHAP@BC remediation, the residual fraction Pb increased by 61.4%, which greatly reduced the bioaccessibility of Pb in the soil. Moreover, nHAP@BC could effectively reduce the accumulation of Pb in plants by 31.4%. Overall, nHAP@BC can effectively remediate Pb-contaminated soil and accelerate the recovery of soil fertility.

[Interaction between functional nano-hydroxyapatite and cells and the underlying mechanisms].

OBJECTIVE: To explore the interaction between arginine functionalized hydroxyapatite (HAP/Arg) nanoparticles and endothelial cells, and to investigate mechanisms for endocytosis kinetics and endocytosis.
 METHODS: Human umbilical vein endothelial cells (HUVECs) were selected as the research model.Cellular uptake of HAP/Arg nanoparticles were observed by laser scanning confocal microscopy.Average fluorescence intensity of cells after ingestion with different concentrations of HAP/Arg nanoparticles were determined by flow cytometer and atomic force microscopy.
 RESULTS: The HAP/Arg nanoparticles with doped terbium existed in cytoplasm, and most of them distributed around the nucleus area after cellular uptake by HUVECs. Cellular uptake process of HAP/Arg nanoparticles in HUVECs was in a time and concentration dependent manner. 4 h and 50 mg/L was the best condition for uptake. HAP/Arg nanoparticles were easier to be up-taken into the cells than HAP nanoparticles without arginine functionalized.
 CONCLUSION: HAP/Arg nanoparticles are internalized by HUVECs cells through an active transport and energy-dependent endocytosis process, and it is up-taken by cells mainly through caveolin-mediated endocytosis, but the clathrin-dependent endocytic pathway is also involved..

Chimeric Protein Template-Induced Shape Control of Bone Mineral Nanoparticles and Its Impact on Mesenchymal Stem Cell Fate.

Protein-mediated molecular self-assembly has become a powerful strategy to fabricate biomimetic biomaterials with controlled shapes. Here we designed a novel chimeric molecular template made of two proteins, silk fibroin (SF) and albumin (ALB), which serve as a promoter and an inhibitor for hydroxyapatite (HA) formation, respectively, to synthesize HA nanoparticles with controlled shapes. HA nanospheres were produced by the chimeric ALB-SF template, whereas HA nanorods were generated by the SF template alone. The success in controlling the shape of HA nanoparticles allowed us to further study the effect of the shape of HA nanoparticles on the fate of rat mesenchymal stem cells (MSCs). We found that the nanoparticle shape had a crucial impact on the cellular uptake and HA nanospheres were internalized in MSCs at a faster rate. Both HA nanospheres and nanorods showed no significant influence on cell proliferation and migration. However, HA nanospheres significantly promoted the osteoblastic differentiation of MSCs in comparison to HA nanorods. Our work suggests that a chimeric combination of promoter and inhibitor proteins is a promising approach to tuning the shape of nanoparticles. It also sheds new light into the role of the shape of the HA nanoparticles in directing stem cell fate.

Surface Corrosion of Nanoscaled Hydroxyapatite During an In Vivo Experiment.

Hydroxyapatite (HA) is widely used as a bioactive ceramics as it forms a chemical bond with bone. However, the drawback to using this material is its inferior mechanical properties. In this research, surface corrosion and disintegration of nanoscaled HA in a dog were studied, and the mechanism by which phase-pure HA dissolved in vivo was investigated. Biological properties of HA in vivo are affected by the grain-boundary dissolution followed by a surface corrosion and microstructural disintegration. This kind of dissolution process, apparently evidenced at the grain boundary, causes particle generation, which indicates that both long-term bone in-growth and mechanical properties can dramatically deteriorate. Implant dissolution by osteoclasts in vivo is also observed on the surface of hydroxyapatite. Implant surface showed an aggressive corrosion by an osteoclast resorption. Severe and deeper dissolution underwent close to osteoclast resulting in formation of smaller and more round particle shape.

Intrinsically superparamagnetic Fe-hydroxyapatite nanoparticles positively influence osteoblast-like cell behaviour.

BACKGROUND: Superparamagnetic nanoparticles (MNPs) have been progressively explored for their potential in biomedical applications and in particular as a contrast agent for diagnostic imaging, for magnetic drug delivery and more recently for tissue engineering applications. Considering the importance of having safe MNPs for such applications, and the essential role of iron in bone remodelling, this study developed and analysed novel biocompatible and bioreabsorbable superparamagnetic nanoparticles, that avoid the use of poorly tolerated magnetite based nanoparticles, for bone tissue engineering applications. RESULTS: MNPs were obtained by doping hydroxyapatite (HA) with Fe ions, by directly substituting Fe2+ and Fe3+ into the HA structure yielding superparamagnetic bioactive phase. In the current study, we have investigated the effects of increasing concentrations (2000 µg/ml; 1000 µg/ml; 500 µg/ml; 200 µg/ml) of FeHA MNPs in vitro using Saos-2 human osteoblast-like cells cultured for 1, 3 and 7 days with and without the exposure to a static magnetic field of 320 mT. Results demonstrated not only a comparable osteoblast viability and morphology, but increased in cell proliferation, when compared to a commercially available Ha nanoparticles, even with the highest dose used. Furthermore, FeHA MNPs exposure to the static magnetic field resulted in a significant increase in cell proliferation throughout the experimental period, and higher osteoblast activity.In vivo preliminary results demonstrated good biocompatibility of FeHA superparamagnetic material four weeks after implantation into a critical size lesion of the rabbit condyle. CONCLUSIONS: The results of the current study suggest that these novel FeHA MNPs may be particularly relevant for strategies of bone tissue regeneration and open new perspectives for the application of a static magnetic field in a clinical setting of bone replacement, either for diagnostic imaging or magnetic drug delivery.

Effect of fluoride, lesion baseline severity and mineral distribution on lesion progression.

The present study investigated the effects of fluoride (F) concentration, lesion baseline severity (ΔZ(base)) and mineral distribution on lesion progression. Artificial caries lesions were created using three protocols [methylcellulose acid gel (MeC), hydroxyethylcellulose acid gel (HEC), carboxymethylcellulose acid solution (CMC)] and with low and high ΔZ(base) groups by varying demineralization times within protocols. Subsequently, lesions were immersed in a demineralizing solution for 24 h in the presence of 0, 1, 2 or 5 ppm F. Changes in mineral distribution characteristics of caries lesions were studied using transverse microradiography. At baseline, the protocols yielded lesions with three distinctly different mineral distributions. Secondary demineralization revealed differences in F response between and within lesion types. In general, lowΔZ lesions were more responsive to F than highΔZ lesions. LowΔZ MeC lesions showed the greatest range of response among all lesions, whereas highΔZ HEC lesions were almost unaffected by F. Laminations were observed in the presence of F in all but highΔZ HEC and CMC lesions. Changes in mineral distribution effected by F were most pronounced in MeC lesions, with remineralization/mineral redeposition in the original lesion body at the expense of sound enamel beyond the original lesion in a dose-response manner. Both ΔZ(base) and lesion mineral distribution directly impact the F response and the extent of secondary demineralization of caries lesions. Further studies - in situ and on natural white spot lesions - are required to better mimic in vivo caries under laboratory conditions.

The role of surface charge on the uptake and biocompatibility of hydroxyapatite nanoparticles with osteoblast cells.

The objective of this study is to evaluate the effect of hydroxyapatite (HAP) nanoparticles with different surface charges on the cellular uptake behavior and in vitro cell viability and proliferation of MC3T3-E1 cell lines (osteoblast). The nanoparticles' surface charge was varied by surface modification with two carboxylic acids: 12-aminododecanoic acid (positive) and dodecanedioic acid (negative). The untreated HAP nanoparticles and dodecanoic acid modified HAP nanoparticles (neutral) were used as the control. X-ray diffraction (XRD) revealed that surface modifications by the three carboxylic acids did not change the crystal structure of HAP nanoparticles; Fourier transform infrared spectroscopy (FT-IR) confirmed the adsorption and binding of the carboxylic acids on the HAP nanoparticles' surfaces; and zeta potential measurement confirmed that the chemicals successfully modified the surface charge of HAP nanoparticles in water based solution. Transmission electron microscopy (TEM) images showed that positively charged, negatively charged and untreated HAP nanoparticles, with similar size and shape, all penetrated into the cells and cells had more uptake of HAP nanoparticles with positive charge compared to those with negative charge, which might be attributed to the attractive or repulsive interaction between the negatively charged cell membrane and positively/negatively charged HAP nanoparticles. The neutral HAP nanoparticles could not penetrate the cell membrane due to their larger size. MTT assay and LDH assay results indicated that as compared with the polystyrene control, greater cell viability and cell proliferation were measured on MC3T3-E1 cells treated with the three kinds of HAP nanoparticles (neutral, positive, and untreated), among which positively charged HAP nanoparticles showed the strongest improvement for cell viability and cell proliferation. In summary, the surface charge of HAP nanoparticles can be modified to influence the cellular uptake of HAP nanoparticles and the different uptake also influences the behavior of cells. These in vitro results may also provide useful information for investigations of HAP nanoparticle applications in gene delivery and intracellular drug delivery.

Tissue distribution of intravenously administrated hydroxyapatite nanoparticles labeled with 125I.

Hydroxyapatite nanoparticles (HANPs) have been developed for biomedical use due to its extraordinary properties. However, the side effects of HANPs on human body have also been concerned, especially in vivo. Now it is still unknown how about the distribution and biobehavior of HANPs in vivo is, though it's very important for application in biosystem. This study was to establish a new method of 125I radiolabeling on HANPs at 80 nm, investigate the long-term tissue distribution of HANPs quantitatively after intravenously administrated HANPs labeled with 125I and the subcellular distribution in liver and spleen by TEM. The results indicated the labeled HANPs had high stability in vitro, and could accumulate mainly in the liver and spleen and decrease in time dependent manner, but still retain in body for more than 28 days. This stagnation most probably attribute to the endocytosis by macrophages in these tissues. The results implied the radioactive iodine labeling was an effective and sensitive method for tracing and analyzing the distribution of NPs in vivo. Liver and spleen should be the main target organ reached when HANPs were injected into circulation system. Because HANPs could stay in vivo for over one month, the biosafety shouldn't be neglected.

Characterization of the chemically deposited hydroxyapatite coating on a titanium substrate.

Bioactive hydroxyapatite (HA) coating on titanium (Ti) implant can be used as a drug delivery device. A controlled release of drug around the implant requires the incorporation of drug into the coating material during the coating process. HA coating was prepared using a two-step procedure in conditions suitable for simultaneous incorporation of the protein-based drug into the coating material. Monetite coating was deposited on Ti substrate in acidic condition followed by the transformation of the monetite coating to HA. X-ray diffraction (XRD) confirmed the formation of the monetite phase at the first step of the coating preparation, which was transformed into HA at the second step. Fourier transform infrared spectroscopy demonstrated typical bands of a crystallized carbonated HA with A- and B-type substitution, which was confirmed by the XRD refinement of the structural parameters. Scanning electron microscope was used to observe the morphology of monetite and HA coatings. Adhesion of the coatings was measured using a scratch tester. The critical shearing stress was found to be 84.20 ± 1.27 MPa for the monetite coating, and 44.40 ± 2.39 MPa for the HA coating.

Investigation of the influence of TiO2distribution on HA/TiO2composite wetting ability using the dispersant SDBS, high-temperature annealing, and ultrasonication.

The use of composites such as hydroxyapatite (HA)/TiO2in bioapplications has attracted increasing attention in recent years. Herein, for the enhancement wetting ability and biocompatibility, the HA/TiO2composite was subjected to different treatments to improve nanoparticle (NP) distribution and surface energy with an aim of mitigating nanotoxicity concerns. The treatments included ultrasonication, high-temperature annealing, and addition of a dispersant and surfactant, sodium dodecylbenzenesulfonate (SDBS). Contact angle measurement tests revealed the effect of SDBS addition on the distribution of TiO2NPs on the HA surface: a decrease in the contact angle and, thus, an increase in the wetting ability of the HA/TiO2composite were observed. The combination of annealing and SDBS addition treatments allowed for guest TiO2particles to be uniformly distributed on the surface of the host HA particles, showing a rapid conversion from a hydrophobic to superhydrophilic property.In vitroinvestigation suggested that the cell viabilities of annealed HA/TiO2, SDBS-added HA/TiO2, and SDBS-added and annealed HA/TiO2reached 89.7%, 94.7%, and 95.8%, respectively, while those of HA and untreated HA/TiO2were 80.3% and 86.9%, respectively. The modified composites exhibited lower cytotoxicities than the unmodified systems (HA and HA/TiO2). Furthermore, the cell adhesion behavior of the composites was confirmed through actin-4',6-Diamidino-2-phenylindole (DAPI) staining, which showed negligible changes in the cytoskeleton architecture of the cells. This study confirmed that a modified HA/TiO2composite has potential for bioapplications.

Back-scattered electron imaging and elemental analysis of retrieved bone tissue following sinus augmentation with deproteinized bovine bone or biphasic calcium phosphate.

OBJECTIVES: To compare resorption of a synthetic biphasic calcium phosphate (BCP) bone-graft substitute with deproteinized bovine bone (DBB) used for human maxillary sinus augmentation. MATERIALS AND METHODS: Eleven patients underwent bilateral maxillary sinus floor augmentation with DBB in one side and a BCP (40%beta-tricalcium phosphate (beta-TCP) and 60% hydroxyapatite) in the contralateral side. Simultaneously, with the augmentation on each side a microimplant was placed vertically from the top of the alveolar crest penetrating the residual bone and the grafting material. Eight months after initial surgery the microimplants were retrieved with a surrounding bone core. The composition of residual graft material and surrounding bone was analysed by scanning electron microscopy and energy dispersive X-ray spectroscopy. RESULTS: Residual graft material of both types was present as 10-500 mum particles in direct contact with, or completely surrounded by, newly formed bone; smaller particles were also present in non-mineralized tissue. In the case of BCP the bone-graft substitute interface showed evidence of superficial disintegration of particles into individual grains. Median Ca/P ratios (at.%), determined from >200 discreet sites within residual graft particles and adjacent bone, were: DBB: 1.61 (confidence interval [CI] 1.59-1.64); BCP: 1.5 (CI 1.45-1.52); DBB-augmented bone: 1.62 (CI 1.59-1.66); BCP-augmented bone: 1.52 (CI 1.47-1.55); P=0.028 for DBB vs. BCP and DBB- vs. BCP-augmented bone. The reduction in Ca/P ratio for BCP over the healing period is consistent with the dissolution of beta-TCP and reprecipitation on the surface of calcium-deficient hydroxyapatite. CONCLUSION: The beta-TCP component of BCP may be gradually substituted by calcium-deficient hydroxyapatite over the healing period. This process and superficial degranulation of BCP particles may influence the progress of resorption and healing.

Synthesis of mesoporous structured hydroxyapatite particles using yeast cells as the template.

In this study, hydroxyapatite (HAp) particles with mesoporous structure have been synthesized from calcium hydroxide and di-ammonium hydrogen phosphate using yeast cells as the template. The characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectrograph (FTIR), N(2) adsorption-desorption isotherms (NADI), transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used for determination of the particles structure (particle size, structural evolution and morphology). The results show that HAp particles with mesoporous structure could be produced. The size of HAp particles was approximately hundreds of nanometer. The pore width of HAp particles was in the range of 2.0-40 nm and the maximum centered around 4.5 nm.

Hybrid structure in PCL-HAp scaffold resulting from biomimetic apatite growth.

Polymer-ceramic composites are favourite candidates when aiming to replace bone tissue. We present here scaffolds made of polycaprolactone-hydroxyapatite (PCL-HAp) composites, and investigate in vitro mineralisation of the scaffolds in SBF after or without a nucleation treatment. In vitro bioactivity is enhanced by HAp incorporation as well as by nucleation treatment, as demonstrated by simulated body fluid (SBF) mineralization. Surprisingly, we obtained a hybrid interconnected organic-inorganic structure, as a result of micropore invasion by biomimetic apatite, which results in a mechanical strengthening of the material after two weeks of immersion in SBF92. The presented scaffolds, due to their multiple qualities, are expected to be valuable supports for bone tissue engineering.

Tissue response and biodegradation of composite scaffolds prepared from Thai silk fibroin, gelatin and hydroxyapatite.

This work aimed to investigate tissue responses and biodegradation, both in vitro and in vivo, of four types of Bombyx mori Thai silk fibroin based-scaffolds. Thai silk fibroin (SF), conjugated gelatin/Thai silk fibroin (CGSF), hydroxyapatite/Thai silk fibroin (SF4), and hydroxyapatite/conjugated gelatin/Thai silk fibroin (CGSF4) scaffolds were fabricated using salt-porogen leaching, dehydrothermal/chemical crosslinking and an alternate soaking technique for mineralization. In vitro biodegradation in collagenase showed that CGSF scaffolds had the slowest biodegradability, due to the double crosslinking by dehydrothermal and chemical treatments. The hydroxyapatite deposited from alternate soaking separated from the surface of the protein scaffolds when immersed in collagenase. From in vivo biodegradation studies, all scaffolds could still be observed after 12 weeks of implantation in subcutaneous tissue of Wistar rats and also following ISO10993-6: Biological evaluation of medical devices. At 2 and 4 weeks of implantation the four types of Thai silk fibroin based-scaffolds were classified as "non-irritant" to "slight-irritant", compared to Gelfoam(®) (control samples). These natural Thai silk fibroin-based scaffolds may provide suitable biomaterials for clinical applications.

Effects of surface carboxylic acid groups of cerasomes, morphologically stable vesicles having a silica surface, on biomimetic deposition of hydroxyapatite in body fluid conditions.

Biomimetic mineralization of supramolecular scaffolds consisting of biomolecules or their analogues has received much attention recently from the viewpoint of creation of novel biomaterials. This study investigated biomimetic deposition of hydroxyapatite (HAp) on cerasomes, morphologically stable organic-inorganic hybrid vesicles. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction studies revealed that the pristine cerasomes induced heterogeneous nucleation of HAp when they were immersed in 1.5SBF, a solution having 1.5 times higher ion concentration than that of a simulated body fluid (SBF). The HAp deposition was further accelerated when dicarboxylic and monocarboxylic acid groups were displayed on cerasome surfaces. These carboxylic acid groups are expected to enhance calcium ion binding to the cerasome surface, causing an increase of HAp nucleation sites. At lower surface concentrations on the cerasome surface, the dicarboxylic acid group is apparently more effective for HAp deposition than the monocarboxylic acid group. The resultant HAp-cerasome hybrids are useful as biocompatible materials having unique properties deriving from the lipid bilayer structure of the cerasomes.

FGF2-adsorbed macroporous hydroxyapatite bone granules stimulate in vitro osteoblastic gene expression and differentiation.

Hydroxyapatite bone granules with a macroporous structure were produced and then adsorbed with basic fibroblast growth factor (FGF2). The in vitro scaffolding role of the granules in cell population and osteogenic differentiation was investigated. The FGF2-adsorbed porous granules allowed the MC3T3-E1 cells to adhere well and then proliferate actively. While the cell growth level on the FGF2-treated granules was observed to be similar to that on the untreated granules, the expression of genes associated with bone, including collagen type I, alkaline phosphatase, and osteocalcin was significantly upregulated by the FGF2 treatment, particularly at the early stage. Moreover, the production of alkaline phosphatase with prolonged culturing was greatly enhanced on the FGF2-adsorbed granules. Taken together, the FGF2 treatment of the hydroxyapatite granules was effective in the osteogenic development and the FGF2-adsorbed bone granules may be useful in bone regeneration area.