In vitro response of osteoblast-like and odontoblast-like cells to unsubstituted and substituted apatites

Effect of Hydroxyapatite Nanoparticles and Nitrogen Plasma Treatment on Osteoblast Biological Behaviors of 3D-Printed HDPE Scaffold for Bone Tissue Regeneration Applications

The need for the repair of bone defects has been increasing due to various causes of loss of skeletal tissue. High density polyethylenes (HDPE) have been used as bone substitutes due to their excellent biocompatibility and mechanical strength. In the present study, we investigated the preosteoblast cell proliferation and differentiation on the adding nano-hydroxyapatite (n-HAp) particles into HDPE scaffold and treating HDPE/n-HAp scaffolds with nitrogen (N₂) plasma. The three-dimensional (3D) HDPE/n-HAp scaffolds were prepared by fused modeling deposition 3D printer. The HDPE/n-HAp was blended with 10 wt% of n-HAp particle. The scaffold surface was reactive ion etched with nitrogen plasma to improve the preosteoblast biological response in vitro. After N₂ plasma treatment, surfaces characterizations were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The proliferation and differentiation of preosteoblast (MC3T3-E1) cells were evaluated by MTT assay and alkaline phosphatase (ALP) activity. The incorporation of n-HAp particles and N₂ plasma surface treatment showed the improvement of biological responses of MC3T3-E1 cells in the HDPE scaffolds.

In vivo efficacy of calcium phosphate-based synthetic-bone-mineral on bone loss resulting from estrogen and mineral deficiencies

Osteopenia and osteoporosis affect over 40 million US adults 50 years and older. Both diseases are strongly influenced by estrogen and nutritional-mineral deficiencies. This study investigates the efficacy of orally delivered synthetic-bone-mineral (SBM), a newly developed calcium phosphate based biomaterial, on reversing bone loss induced by these two critical deficiencies. Thirty 3-month-old female rats were randomly allocated to either control-sham surgery on normal diet; or one of the four experimental groups: Sham surgery on a low mineral diet (LMD), ovariectomized (OVX) on LMD, OVX on LMD with SBM with/without fluoride (F). The rats were sacrificed after 6 months, at 9-month-old. After 6 months, although all groups lost bone mineral density relative to controls, the supplemented OVX rats showed higher bone mineral density than their unsupplemented counterparts. The 2 SBM supplemented groups improved bone loading capacity by 28.1 and 35.4% compared to the OVX LMD group. Bones from supplemented rats exhibited higher inorganic/organic ratios. The addition of F did not have a significant influence on bone loss. Our findings suggest that SBM supplement is effective in maintaining bone health and offsetting the deleterious effects of estrogen and/or mineral deficiencies on bone density, microarchitecture, and strength.

Impact of calcium aluminate cement with additives on dental pulp-derived cells

Calcium aluminate cement (CAC) has been highlighted as a promising alternative for endodontic use aiming at periapical tissue repair. However, its effects on dental pulp cells have been poorly explored. Objective: This study assessed the impact of calcium chloride (CaCl₂) and bismuth oxide (Bi2O₃) or zinc oxide (ZnO) additives on odontoblast cell response to CAC. Methodology: MDPC-23 cells were exposed for up to 14 d: 1) CAC with 2.8% CaCl₂ and 25% ZnO (CACz); 2) CAC with 2.8% CaCl₂ and 25% Bi₂O₃ (CACb); 3) CAC with 10% CaCl₂ and 25% Bi₂O₃ (CACb+); or 4) mineral trioxide aggregate (MTA), placed on inserts. Non-exposed cultures served as control. Cell morphology, cell viability, gene expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), and dentin matrix protein 1 (DMP-1), ALP activity, and extracellular matrix mineralization were evaluated. Data were compared using ANOVA (α=5%). Results: Lower cell density was detected only for MTA and CACb+ compared with Control, with areas showing reduced cell spreading. Cell viability was similar among groups at days one and three (p>0.05). CACb+ and MTA showed the lowest cell viability values at day seven (p>0.05). CACb and CACb+ promoted higher ALP and BSP expression compared with CACz (p<0.05); despite that, all cements supported ALP activity. Matrix mineralization were enhanced in CACb+ and MTA. Conclusion: In conclusion, CAC with Bi₂O₃, but not with ZnO, supported the expression of odontoblastic phenotype, but only the composition with 10% CaCl₂ promoted mineralized matrix formation, rendering it suitable for dentin-pulp complex repair.

In Vitro and In Vivo Characterization of N-Acetyl-L-Cysteine Loaded Beta-Tricalcium Phosphate Scaffolds

Beta-tricalcium phosphate bioceramics are widely used as bone replacement scaffolds in bone tissue engineering. The purpose of this study is to develop beta-tricalcium phosphate scaffold with the optimum mechanical properties and porosity and to identify the effect of N-acetyl-L-cysteine loaded to beta-tricalcium phosphate scaffold on the enhancement of biocompatibility. The various interconnected porous scaffolds were fabricated using slurries containing various concentrations of beta-tricalcium phosphate and different coating times by replica method using polyurethane foam as a passing material. It was confirmed that the scaffold of 40 w/v% beta-tricalcium phosphate with three coating times had optimum microstructure and mechanical properties for bone tissue engineering application. The various concentration of N-acetyl-L-cysteine was loaded on 40 w/v% beta-tricalcium phosphate scaffold. Scaffold group loaded 5 mM N-acetyl-L-cysteine showed the best viability of MC3T3-E1 preosteoblastic cells in the water-soluble tetrazolium salt assay test.

Effect of a dietary supplement on peri-implant bone strength in a rat model of osteoporosis

PURPOSE

Osteoporosis contributes to impaired bone regeneration and remodeling through an imbalance of osteoblastic and osteoclastic activity, and can delay peri-implant bone formation after dental implant surgery, resulting in a prolonged treatment period. It poses several difficulties for individuals with large edentulous areas, and decreases their quality of life. Consequently, prompt postoperative placement of the final prosthesis is very important clinically. Peri-implant bone formation may be enhanced by systemic approaches, such as the use of osteoporosis supplements, to promote bone metabolism. We aimed to confirm whether intake of synthetic bone mineral (SBM), a supplement developed for osteoporosis, could effectively accelerate peri-implant bone formation in a rat model of osteoporosis.

METHODS

Thirty-six 7-week-old ovariectomized female Wistar rats were randomly assigned to receive a standardized diet with or without SBM (Diet with SBM group and Diet without SBM group, respectively; n=18 for both). The rats underwent implant surgery at 9 weeks of age under general anesthesia. The main outcome measures, bone mineral density (BMD) and pull-out strength of the implant from the femur, were compared at 2 and 4 weeks after implantation using the Mann-Whitney U test.

RESULTS

Pull-out strength and BMD in the Diet with SBM group were significantly greater than those in the Diet without SBM group at 2 and 4 weeks after implantation.

CONCLUSIONS

This study demonstrated that SBM could be effective in accelerating peri-implant bone formation in osteoporosis.

Improved Bone Micro Architecture Healing Time after Implant Surgery in an Ovariectomized Rat

The present animal study investigated whether oral intake of synthetic bone mineral (SBM) improves peri-implant bone formation and bone micro architecture (BMA). SBM was used as an intervention experimental diet and AIN-93M was used as a control. The SBM was prepared by mixing dicalcium phosphate dihydrate (CaHPO4·2H2O) and magnesium and zinc chlorides (MgCl2 and ZnCl2, respectively), and hydrolyzed in double-distilled water containing dissolved potassium carbonate and sodium fluoride. All rats were randomly allocated into one of two groups: a control group was fed without SBM (n = 18) or an experimental group was fed with SBM (n = 18), at seven weeks old. At 9 weeks old, all rats underwent implant surgery on their femurs under general anesthesia. The implant was inserted into the insertion socket prepared at rats' femur to a depth of 2.5 mm by using a drill at 500 rpm. Nine rats in each group were randomly selected and euthanized at 2 weeks after implantation. The remaining nine rats in each group continued their diets, and were euthanized in the same manner at 4 weeks after implantation. The femur, including the implant, was removed from the body and implant was pulled out by an Instron universal testing machine. After the implant removal, BMA was evaluated by bone surface ratio (BS/BV), bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular number (TbN), trabecular star volume (Vtr), and micro-CT images. BS/BV, BV/TV, TbTh and Vtr were significantly greater in the rats were fed with SBM than those were fed without SBM at 2 and 4 weeks after implantation (P < 0.05). The present results revealed that SBM improves the peri-implant formation and BMA, prominent with trabecular bone structure. The effect of SBM to improve secondary stability of the implant, and shortening the treatment period should be investigated in the future study.

Potential for acceleration of bone formation after implant surgery by using a dietary supplement: an animal study

Dental implant treatment is an effective modality to restore lost aesthetic and masticatory functions. However, healing after implant surgery takes at least 3-6 months. This prolonged healing period poses several difficulties for individuals with a large edentulous area and decreases their quality of life. Consequently, shortening the healing period and accelerating final prosthesis placement after surgery is very clinically important. Peri-implant bone formation may be enhanced by systemic approaches, such as the use of osteoporosis supplements, to promote bone metabolism. To confirm whether intake of a supplement developed for osteoporosis, synthetic bone mineral (SBM), was effective in accelerating peri-implant bone formation as part of the healing process after implantation. Twenty-four 5-week-old female Wistar rats were randomly assigned to receive a standardised diet without (control group, n = 12) or with SBM (n = 12). The rats had implant surgery at 8 weeks of age under general anaesthesia. The main outcome measures were bone mineral density (BMD) and pull-out strength in the implant and femur, which were compared between the groups at 2 and 4 weeks after implantation using the Mann-Whitney U test. BMD was significantly greater in the SBM group at 2 and 4 weeks after implantation compared to the control group. Pull-out strength was significantly greater in the SBM groups at 2 and 4 weeks after implantation compared to the control group. This study demonstrated that SBM could be effective in accelerating peri-implant bone formation during the healing period after implantation.

The performance of dental pulp stem cells on nanofibrous PCL/gelatin/nHA scaffolds

The aim of current study is to investigate the in vitro and in vivo behavior of dental pulp stem cells (DPSCs) seeded on electrospun poly(epsilon-caprolactone) (PCL)/gelatin scaffolds with or without the addition of nano-hydroxyapatite (nHA). For the in vitro evaluation, DNA content, alkaline phosphatase (ALP) activity and osteocalcin (OC) measurement showed that the scaffolds supported DPSC adhesion, proliferation, and odontoblastic differentiation. Moreover, the presence of nHA upregulated ALP activity and promoted OC expression. Real-time PCR data confirmed these results. SEM micrographs qualitatively confirmed the proliferation and mineralization characteristics of DPSCs on both scaffolds. Subsequently, both scaffolds seeded with DPSCs were subcutaneously implanted into immunocompromised nude mice. Scaffolds with nHA but without cells were implanted as control. Histological evaluation revealed that all implants were surrounded by a thin fibrous tissue capsule without any adverse effects. The cell/scaffold composites showed obvious in vivo hard tissue formation, but there was no sign of tissue ingrowth. Further, the combination of nHA in scaffolds did upregulate the expression of specific odontogenic genes. In conclusion, the incorporation of nHA in nanofibers indeed enhanced DPSCs differentiation towards an odontoblast-like phenotype in vitro and in vivo.

Effect of Fluoride-substituted Apatite on In Vivo Bone Formation

Biological apatites are characterized by the presence of minor constituents such as magnesium (Mg), chloride (Cl), or fluoride (F) ions. These ions affect cell proliferation and osteoblastic differentiation during bone tissue formation. F-substituted apatites are being explored as potential bonegraft materials. The aim of the present study is to investigate the mechanism of bone formation induced by fluoride-substituted apatite (FAp) by analyzing the effect of FAp on the process of in vivo bone formation. FAps containing different F concentrations ( l-FAp: 0.48wt%, m-FAp: 0.91wt%, h-FAp: 2.23wt%) and calcium-deficient apatite (CDA), as positive control, were implanted in rat tibia and bone formation was evaluated by histological examination, immuhistochemistry, in situ hybridization and tartrate-resistant acid phosphatase examinations. The results showed that l-FAp, m-FAp, h-FAp, and CDA biomaterials allowed migration of macrophages, attachment, proliferation, and phenotypic expression of bone cells leading to new bone formation in direct apposition to the particles. However, the l-FAp preparation allowed faster bone conduction compared to the other experimental materials. These results suggest that FAp with low F concentration may be an efficient bonegraft material for dental and medical application.

Characterization and cytocompatibility of surface modified polyamide66

The chemical modification of polyamide66 (PA66) membrane by graft polymerization with methacrylic acid (MAA) was initiated under ultraviolet light. Subsequently, covalent immobilization of bioactive surface was obtained by coupling gelatin to the MAA graft chains with the aid of a water-soluble carbodiimide (WSC). The existence of carboxyl groups grafted on PA66 surface was verified quantitatively by UV-vis spectroscopy. The chemical composition, surface topography, and wettability were investigated by Fourier transform infrared (FTIR) technique, X-ray photoelectron spectroscopy, atomic force microscopy, and water contact angle (WCA) measurement. Results showed that the WCA changed from the original value of 67.5 degrees to the minimum value of 30 degrees after grafting with PMAA. Original PA66 displayed a smooth surface morphology [root mean square (RMS) roughness was around 16 nm]. The modified PA66 surface exhibited an increase in roughness (RMS roughness around 21 nm). Simultaneously, the original and modified PA66 membranes were cultured with MG63 cells to investigate their cytocompatibility. The in vitro biological evaluation demonstrated that the immobilization of gelatin on PA66 membrane acted as a good template for the attachment and proliferation of cells. Also, the less toxic reagents and the moderate reaction conditions involved will be very helpful for the introduction of functional groups onto polymer surface.

Simultaneous incorporation of carbonate and fluoride in synthetic apatites: Effect on crystallographic and physico-chemical properties

The mineral in bone is an impure hydroxyapatite, with carbonate as the chief minor substituent. Fluoride has been shown to stimulate osteoblastic activity and inhibit osteoclastic resorption in vitro. CO(3)- and F-substituted apatite (CFA) has been considered as potential bone graft material for orthopedic and dental applications. The objective of this study was to determine the effects of simultaneously incorporated CO(3) and F on the crystallographic physico-chemical properties of apatite. The results showed that increasing CO(3) and Na content in apatites with relatively constant F concentration caused a decrease in crystallite size and an increase in the extent of calcium release; increasing F content in apatites with relatively constant CO(3) concentration caused an increase in crystallite size and a decrease in the extent of Ca release. These findings suggest that CFAs as bone graft materials of desired solubility can be prepared by manipulating the relative concentrations of CO(3) and F incorporated in the apatite.

Mechanical and in vitro performance of 13-93 bioactive glass scaffolds prepared by a polymer foam replication technique

A polymer foam replication technique was used to prepare porous scaffolds of 13-93 bioactive glass with a microstructure similar to that of human trabecular bone. The scaffolds, with a porosity of 85+/-2% and pore size of 100-500 microm, had a compressive strength of 11+/-1 MPa, and an elastic modulus of 3.0+/-0.5 GPa, approximately equal to the highest values reported for human trabecular bone. The strength was also considerably higher than the values reported for polymeric, bioactive glass-ceramic and hydroxyapatite constructs prepared by the same technique and with the equivalent level of porosity. The in vitro bioactivity of the scaffolds was observed by the conversion of the glass surface to a nanostructured hydroxyapatite layer within 7 days in simulated body fluid at 37 degrees C. Protein and MTT assays of in vitro cell cultures showed an excellent ability of the scaffolds to support the proliferation of MC3T3-E1 preosteoblastic cells, both on the surface and in the interior of the porous constructs. Scanning electron microscopy showed cells with a closely adhering, well-spread morphology and a continuous increase in cell density on the scaffolds during 6 days of culture. The results indicate that the 13-93 bioactive glass scaffolds could be applied to bone repair and regeneration.

In vitro investigation of orthopedic titanium-coated and brushite-coated surfaces using human osteoblasts in the presence of gentamycin

Anti-infective coatings have been developed to protect the surfaces of cementless implants from bacterial colonization that is known to be a prerequisite for device-related infection. The aim of this study is to investigate the effect of brushite-coated arthroplasty surfaces on human osteoblasts and to evaluate the impact of concomitant exposure to gentamycin. We cultured human osteoblasts (hFOB 1.19) on brushite-coated and uncoated titanium alloy in the presence of gentamycin and analyzed cell function and vitality. Our results show that brushite-coated titanium alloy surfaces supported the function of osteoblasts and the expression of extracellular matrix even in the presence of highly dosed gentamycin. Brushite-coated titanium alloy surfaces supported osteogenic function, indicating that this coating could enhance implant osteointegration in vivo. Concomitant exposure to gentamycin slightly decreased osteoblastic activity in vitro, suggesting that there might also be negative effects in vivo. However, in vivo studies are necessary to validate these in vitro findings.

MC3T3-E1 cell adhesion to hydroxyapatite with adsorbed bone sialoprotein, bone osteopontin, and bovine serum albumin

Native bone tissue is composed of a complex matrix of collagen, non-collagenous proteins, and hydroxyapatite (HAP). Bone sialoprotein (BSP) and bone osteopontin (OPN) are members of the non-collagenous protein family termed the SIBLING (small integrin-binding ligand, N-linked glycoproteins) proteins, which are primarily found in mineralized tissues. Previously, OPN was shown to exhibit a preferential orientation for MC3T3-E1 cell adhesion when it was specifically bound to collagen, while the MC3T3-E1 cell adhesion was shown to be dependant on the conformational flexibility of BSP specifically bound to collagen. Additionally, OPN was shown to play a greater role than BSP for cell binding to collagen. In this work, the orientations and conformations of BSP and OPN specifically bound to HAP are probed under similar conditions. Radiolabeled adsorption isotherms were obtained for BSP and OPN on HAP formed from a simulated body fluid, and the results show that HAP has the capacity to bind significantly more BSP than OPN. An in vitro MC3T3-E1 cell adhesion assay was then performed to compare the cell binding ability of adsorbed BSP and OPN specifically bound to HAP. It was found that there is a preference for cell binding to HAP with adsorbed BSP as compared to OPN, but not to a statistically significant level. However, the maximum cell binding was observed on HAP substrates with adsorbed heat denatured bovine serum albumin (BSA). The influence of BSA on cell binding was shown to be concentration dependant and it is believed that the adsorbed BSA modulates the proliferation state of the bound cells.

Influence of recovering collagen with bioactive glass on osteoblast behavior

Bioactive ceramics have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, and metabolic activity of rat primary osteoblasts in contact with four different samples: type I collagen, bioactive glass-coated collagen (GC), and both samples submitted to immersion for 5 days in a simulated body fluid. The bioactive glass coating was obtained from a sol-gel process. The cell viability, the alkaline phosphate, the collagen secretion, and the nitric oxide production by osteoblast were measured after 72 h of incubation in the presence of the samples. The GC that was immersed for 5 days in a simulated body fluid solution showed an increase in osteoblast viability and proliferation when it was compared with control and the other samples.

Physico-chemical-mechanical and in vitro biological properties of calcium phosphate cements with doped amorphous calcium phosphates

Calcium phosphate cements (CPCs) are successfully used as bone substitutes in dentistry and orthopaedic applications. This study investigated the physico-chemical-mechanical properties of and in vitro biological properties (cell response) of CPCs prepared with amorphous calcium carbonate phosphate (ACCP) doped with magnesium (ACCP-Mg), zinc (ACCp-Zn) or fluoride (ACCP-F) ions. The experimental CPC consisted of alpha-TCP, doped ACCP, and MPCM powders as matrix and biphasic calcium phosphate (BCP) granules. X-ray diffraction analysis showed that the matrix converted to apatite with poor crystallinity (reflecting small crystal size) after setting for 24 h, while BCP remained apparently unchanged. Cements with ACCP-F (F-CPC) had shorter setting times and greater compressive strength compared to cements with ACCP-Mg (Mg-CPC) or ACCP-Zn (Zn-CPC). Scanning electron microscopy (SEM) showed that crystals set on Mg-CPC and Zn-CPC were smaller compared to those on F-CPC. The total porosity of Mg-CPC was greater compared to Zn-CPC or F-CPC. Osteoblast-like cells, MC3T3-E1, remained viable and maintained their ability to express alkaline phosphatase in contact with the CPCs with doped ACCPs.