Apatite/amelogenin coating on titanium promotes osteogenic gene expression

Amelogenin-Derived Peptides in Bone Regeneration: A Systematic Review

Amelogenins are enamel matrix proteins currently used to treat bone defects in periodontal surgery. Recent studies have highlighted the relevance of amelogenin-derived peptides, named LRAP, TRAP, SP, and C11, in bone tissue engineering. Interestingly, these peptides seem to maintain or even improve the biological activity of the full-length protein, which has received attention in the field of bone regeneration. In this article, the authors combined a systematic and a narrative review. The former is focused on the existing scientific evidence on LRAP, TRAP, SP, and C11's ability to induce the production of mineralized extracellular matrix, while the latter is concentrated on the structure and function of amelogenin and amelogenin-derived peptides. Overall, the collected data suggest that LRAP and SP are able to induce stromal stem cell differentiation towards osteoblastic phenotypes; specifically, SP seems to be more reliable in bone regenerative approaches due to its osteoinduction and the absence of immunogenicity. However, even if some evidence is convincing, the limited number of studies and the scarcity of in vivo studies force us to wait for further investigations before drawing a solid final statement on the real potential of amelogenin-derived peptides in bone tissue engineering.

Positive Effects of Three-Dimensional Collagen-Based Matrices on the Behavior of Osteoprogenitors

Recent research has demonstrated that reinforced three-dimensional (3D) collagen matrices can provide a stable scaffold for restoring the lost volume of a deficient alveolar bone. In the present study, we aimed to comparatively investigate the migratory, adhesive, proliferative, and differentiation potential of mesenchymal stromal ST2 and pre-osteoblastic MC3T3-E1 cells in response to four 3D collagen-based matrices. Dried acellular dermal matrix (DADM), hydrated acellular dermal matrix (HADM), non-crosslinked collagen matrix (NCM), and crosslinked collagen matrix (CCM) did all enhance the motility of the osteoprogenitor cells. Compared to DADM and NCM, HADM and CCM triggered stronger migratory response. While cells grown on DADM and NCM demonstrated proliferative rates comparable to control cells grown in the absence of a biomaterial, cells grown on HADM and CCM proliferated significantly faster. The pro-proliferative effects of the two matrices were supported by upregulated expression of genes regulating cell division. Increased expression of genes encoding the adhesive molecules fibronectin, vinculin, CD44 antigen, and the intracellular adhesive molecule-1 was detected in cells grown on each of the scaffolds, suggesting excellent adhesive properties of the investigated biomaterials. In contrast to genes encoding the bone matrix proteins collagen type I (Col1a1) and osteopontin (Spp1) induced by all matrices, the expression of the osteogenic differentiation markers Runx2, Alpl, Dlx5, Ibsp, Bglap2, and Phex was significantly increased in cells grown on HADM and CCM only. Short/clinically relevant pre-coating of the 3D biomaterials with enamel matrix derivative (EMD) or recombinant bone morphogenetic protein-2 (rBMP-2) significantly boosted the osteogenic differentiation of both osteoprogenitor lines on all matrices, including DADM and NCM, indicating that EMD and BMP-2 retained their biological activity after being released from the matrices. Whereas EMD triggered the expression of all osteogenesis-related genes, rBMP-2 upregulated early, intermediate, and late osteogenic differentiation markers except for Col1a1 and Spp1. Altogether, our results support favorable influence of HADM and CCM on the recruitment, growth, and osteogenic differentiation of the osteoprogenitor cell types. Furthermore, our data strongly support the biofunctionalization of the collagen-based matrices with EMD or rBMP-2 as a potential treatment modality for bone defects in the clinical practice.

Effects of UV Treatment on Ceria-Stabilized Zirconia/Alumina Nanocomposite (NANOZR)

Nanostructured zirconia/alumina composite (NANOZR) has been explored as a suitable material for fabricating implants for patients with metal allergy. In this study, we examined the effect of UV treatment on the NANOZR surface. The experimental group was UV-treated NANOZR and the control group was untreated NANOZR. Observation of the surface of the UV-treated materials revealed no mechanical or structural change; however, the carbon content on the material surface was reduced, and the material surface displayed superhydrophilicity. Further, the effects of the UV-induced superhydrophilic properties of NANOZR plates on the adhesion behavior of various cells were investigated. Treatment of the NANOZR surface was found to facilitate protein adsorption onto it. An in vitro evaluation using rat bone marrow cells, human vascular endothelial cells, and rat periodontal ligament cells revealed high levels of adhesion in the experimental group. In addition, it was clarified that the NANOZR surface forms active oxygen and suppresses the generation of oxidative stress. Overall, the study results suggested that UV-treated NANOZR is useful as a new ceramic implant material.

Adjunctive use of enamel matrix derivatives to porcine-derived xenograft for the treatment of one-wall intrabony defects: Two-year longitudinal results of a randomized controlled clinical trial

Background

The purpose of this study was to evaluate the potential advantages of adjunctive use of enamel matrix protein derivative (EMD) in combination with demineralized porcine bone matrix (DPBM) for the treatment of one‐wall intrabony defects in the molar regions, in comparison with the use of DPBM alone, through a randomized controlled clinical trial.

Methods

Forty‐two participants were randomly assigned to two groups: one where DPBM with the adjunctive use of EMD (test group, n = 20) was applied and the other without EMD (control group, n = 22). Changes in the clinical and radiographic parameters from baseline at 6, 12, and 24 months were measured (probing pocket depth, clinical attachment loss, defect depth, and defect width). Postoperative discomfort (severity/duration of pain and swelling) and early soft tissue wound healing (dehiscence/fenestration, persistent swelling, spontaneous bleeding, and ulceration) were also assessed.

Results

Both treatment modalities, with and without EMD, resulted in significant improvement of clinical and radiographic outcomes without any severe adverse events. However, no statistically significant differences in any of the measured parameters were found when the two groups were compared. Early wound healing outcomes and the severity of swelling did not differ between the groups, but the severity of pain (P = 0.046), duration (P = 0.033), and swelling (P = 0.022) were significantly lower in the test group.

Conclusions

DPBM has been verified for biocompatibility and can be used as a scaffold to enhance the clinical and radiographic outcomes of periodontal regeneration of one‐wall intrabony defects. In particular, the adjunctive use of EMD significantly reduced the postoperative discomfort.

Comparative assessment of anterior maxillary alveolar ridge preservation with and without adjunctive use of enamel matrix derivative: A randomized clinical trial

OBJECTIVES

The aim of this randomized, controlled, parallel-arm study was to evaluate the (a) radiographic bone dimensional changes, (b) postoperative discomfort, and (c) early soft tissue wound healing outcomes, following extraction of maxillary anterior teeth (central and lateral incisors) and treatment with alveolar ridge preservation (ARP) with and without the adjunctive use of enamel matrix derivative (EMD).

METHODS

Thirty extraction sockets were randomly assigned to two groups: deproteinized bovine bone mineral with 10% collagen covered with collagen membrane with the adjunctive use of EMD (test group) and without EMD (control group). Bone dimensional changes were measured using cone beam computed tomography at 3 and 5 months after ARP. The severity and duration of pain and swelling were evaluated using self-reported questionnaires, and soft tissue wound healing outcomes were assessed clinically. Chi-square tests and t tests were conducted to compare differences between the two groups.

RESULTS

Radiographic and clinical analyses showed no significant differences in horizontal and vertical bone dimensional changes and soft tissue wound healing outcomes (including spontaneous bleeding, persistent swelling, and ulceration) between the two groups. There were no significant differences in the severity of pain and swelling between the two groups, but the durations of pain (difference [df] = 1.20, 95% CI = 0.33-2.06; p = .008) and swelling (df = 1.06, 95% CI = 0.11-2.01; p = .029) were significantly reduced in the test group.

CONCLUSION

Alveolar ridge preservation with the adjunctive use of EMD reduced the durations of postoperative pain and swelling following maxillary anterior teeth extraction.

The change of surface charge by lithium ion coating enhances protein adsorption on titanium

Surface charge is one of the essential physicochemical properties of titanium surfaces for extracellular protein adsorption. Titanium surfaces are generally electronegatively charged at physiological pH. Typical cellular adhesive proteins and cell membranes are also negatively charged. Therefore, there are no direct electric interactions between proteins and titanium surfaces at physiological pH. The objective of this study was to determine how different electrical charges on titanium surfaces affect protein adsorption. Commercially pure grade-2 titanium disks, 19 mm in diameter and 1.5 mm in thickness, having acid-etched micro-roughed surfaces, were prepared. Electropositive charge was supplied by soaking in LiOH solution at concentrations of 0.05, 0.1, 0.25, 0.5, and 1.0 M. After LiOH treatment, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. The zeta potential, isoelectric point, and wettability of titanium surfaces were measured. The adsorption levels of proteins, including albumin, laminin, and fibronectin, were evaluated. Osteoblastic cell attachment level was also determined. Incorporation of Li was detected in the oxide layer of titanium without surface morphological modification. The zeta potential was shifted up and the isoelectric point was increased from 3.94 to 5.63 by LiOH treatment. Long-term super-hydrophilicity was also obtained on Li-treated surfaces. The adsorption of albumin and laminin increased with increasing concentration of LiOH treatment solution, whereas fibronectin adsorption was highest upon treatment with 0.25 M. The osteoblastic cell attachment level was shown to be dependent on the amount of fibronectin adsorbed. In conclusion, LiOH treatment enhances biological adhesion on titanium with an increase in surface charge and hydrophilicity. This study suggests that modifying the surface charge provides a direct protein-to-materials interaction and the optimal application of Li should be investigated further.

255-nm Light-emitting Diode Kills Enterococcus faecalis and Induces the Production of Cellular Biomarkers in Human Embryonic Palatal Mesenchyme Cells and Gingival Fibroblasts

INTRODUCTION

The successful treatment of infected or inflamed endodontic tissues requires chemomechanical debridement of the canal spaces and proper sealing of the coronal and apical canal openings. Only a few methods are available to further disinfect areas or initiate regeneration of local tissues. In this study, we assessed the ability of 255-nm and 405-nm light-emitting diode (LED) treatment to kill planktonic cultures of Enterococcus faecalis and induce the production of cellular biomarkers related to endodontic tissue regeneration.

METHODS

We determined the antimicrobial effects of 255-nm and 405-nm LED treatment on E. faecalis and the effects of 255-nm and 405-nm LED treatment on the production of osteoinductive, angiogenic, proliferative, and proinflammatory biomarkers from human embryonic palatal mesenchyme (HEPM) cells and gingival fibroblasts.

RESULTS

We showed that 255-nm LED but not 405-nm LED treatment killed E. faecalis; the 255-nm LED and sodium hypochlorite more efficiently killed E. faecalis; neither 255-nm nor 405-nm LED treatment affected the viability of HEPM cells and gingival fibroblasts; and 255-nm LED treatment, alone or in combination with 405-nm LED treatment, of HEPM cells and gingival fibroblasts induced the production of biomarkers related to endodontic tissue regeneration.

CONCLUSIONS

The results of this study suggest a new treatment modality using short periods of 255-nm LED treatment as an adjunct to chemomechanical debridement for the disinfection of inflamed sites and the production of biomarkers related to endodontic tissue regeneration.

Effect of Amelogenin Coating of a Nano-Modified Titanium Surface on Bioactivity

The interactions between implants and host tissues depend on several factors. In particular, a growing body of evidence has demonstrated that the surface texture of an implant influences the response of the surrounding cells. The purpose of this study is to develop new implant materials aiming at the regeneration of periodontal tissues as well as hard tissues by coating nano-modified titanium with amelogenin, which is one of the main proteins contained in Emdogain®. We confirmed by quartz crystal microbalance evaluation that amelogenin is easy to adsorb onto the nano-modified titanium surface as a coating. Scanning electron microscopy, scanning probe microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses confirmed that amelogenin coated the nano-modified titanium surface following alkali-treatment. In vitro evaluation using rat bone marrow and periodontal ligament cells revealed that the initial adhesion of both cell types and the induction of hard tissue differentiation such as cementum were improved by amelogenin coating. Additionally, the formation of new bone in implanted surrounding tissues was observed in in vivo evaluation using rat femurs. Together, these results suggest that this material may serve as a new implant material with the potential to play a major role in the advancement of clinical dentistry.

Kaempferol-immobilized titanium dioxide promotes formation of new bone: effects of loading methods on bone marrow stromal cell differentiation in vivo and in vitro

Background

Surface modification of titanium dioxide (TiO₂) implants promotes bone formation and shortens the osseointegration period. Kaempferol is a flavonoid that has the capacity to promote osteogenic differentiation in bone marrow stromal cells. The aim of this study was to promote bone formation around kaempferol immobilized on TiO₂ implants.

Methods

There were four experimental groups. Alkali-treated TiO₂ samples (implants and discs) were used as a control and immersed in Dulbecco's phosphate-buffered saline (DPBS) (Al-Ti). For the coprecipitation sample (Al-cK), the control samples were immersed in DPBS containing 50 µg kaempferol/100% ethanol. For the adsorption sample (Al-aK), 50 µg kaempferol/100% ethanol was dropped onto control samples. The surface topography of the TiO₂ implants was observed by scanning electron microscopy with energy-dispersive X-ray spectroscopy, and a release assay was performed. For in vitro experiments, rat bone marrow stromal cells (rBMSCs) were cultured on each of the TiO₂ samples to analyze cell proliferation, alkaline phosphatase activity, calcium deposition, and osteogenic differentiation. For in vivo experiments, TiO₂ implants placed on rat femur bones were analyzed for bone-implant contact by histological methods.

Results

Kaempferol was detected on the surface of Al-cK and Al-aK. The results of the in vitro study showed that rBMSCs cultured on Al-cK and Al-aK promoted alkaline phosphatase activity, calcium deposition, and osteogenic differentiation. The in vivo histological analysis revealed that Al-cK and Al-aK stimulated new bone formation around implants.

Conclusion

TiO₂ implant-immobilized kaempferol may be an effective tool for bone regeneration around dental implants.

Behavior of Human Osteoblast Cells Cultured on Titanium Discs in Relation to Surface Roughness and Presence of Melatonin

The aim of this work was to observe the behavior of osteoblast cells cultured in vitro on titanium discs in relation to disc surface roughness and the addition of melatonin to the culture medium. MG63 osteoblast cells were cultivated on 120 Grade 5 Ti divided into three groups: Group E, treated with dual acid etch; Group EP, treated with dual acid etch and calcium phosphate; and Group M, machined. Surface roughness was examined under a laser scanning confocal microscope (CLSM) and scanning electron microscopy (SEM). The proliferation and morphology of cells were determined under fluorescence microscopy and SEM. Messenger ribonucleic acid (mRNA) of different genes related to osteoblastic differentiation was quantified by means of real-time quantitative polymerase chain reaction (RT-PCR) assay. The greatest surface roughness was found in Group EP (Ra 0.354 µm), followed by Group E (Ra 0.266 µm), and Group M (Ra 0.131 µm), with statistically significant differences between the groups (p < 0.001). In the presence of melatonin a trend to a higher cell proliferation was observed in all groups although significant differences were only found in Group M (p = 0.0079). Among the genes studied, a significant increase in phosphate-regulating neutral endopeptidase, X-linked (PHEX) expression was observed in cells cultured on EP discs. The addition of melatonin increased osteoblast cell proliferation and differentiation, and may favor the osseointegration of dental implants.

A new application of cell-free bone regeneration: immobilizing stem cells from human exfoliated deciduous teeth-conditioned medium onto titanium implants using atmospheric pressure plasma treatment

Introduction

Surface modification of titanium (Ti) implants promotes bone formation and shortens the osseointegration period. The aim of this study was to promote bone regeneration and stability around implants using atmospheric pressure plasma (APP) pretreatment. This was followed by immobilization of stem cells from human exfoliated deciduous teeth-conditioned medium (SHED-CM) on the Ti implant surface.

Methods

Ti samples (implants, discs, powder) were treated with APP for 30 seconds. Subsequently, these were immobilized on the treated Ti surface, soaked and agitated in phosphate-buffered saline or SHED-CM for 24 hours at 37 °C. The surface topography of the Ti implants was observed using scanning electron microscopy with energy dispersive X-ray spectroscopy. In vivo experiments using Ti implants placed on canine femur bone were then conducted to permit histological analysis at the bone-implant boundary. For the in vitro experiments, protein assays (SDS-PAGE, Bradford assay, liquid chromatography-ion trap mass spectrometry) and canine bone marrow stromal cell (cBMSC) attachment assays were performed using Ti discs or powder.

Results

In the in vitro study, treatment of Ti implant surfaces with SHED-CM led to calcium phosphate and extracellular matrix protein immobilization. APP pretreatment increased the amount of SHED-CM immobilized on Ti powder, and contributed to increased cBMSC attachment on Ti discs. In the in vivo study, histological analysis revealed that the Ti implants treated with APP and SHED-CM stimulated new bone formation around implants.

Conclusions

Implant device APP pretreatment followed by SHED-CM immobilization may be an effective application to facilitate bone regeneration around dental implants.

Leucine-rich amelogenin peptide (LRAP) as a surface primer for biomimetic remineralization of superficial enamel defects: An in vitro study

This study was carried out to obtain more information about the assembly of hydroxyapatite bundles formed in the presence of Leucine-Rich Amelogenin Peptide (LRAP) and to evaluate its effect on the remineralization of enamel defects through a biomimetic approach. One or 2 mg/mL LRAP solutions containing 2.5 mM of Ca(+2) and 1.5 mM phosphate were prepared (pH = 7.2) and stored at 37 °C for 24 h. The products of the reaction were studied using atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Vickers surface microhardness recovery (SMR%) of acid-etched bovine enamel, with or without LRAP surface treatment, were calculated to evaluate the influence of peptide on the lesion remineralization. Distilled water and 1 or 2 mg/mL LRAP solution (pH = 7.2) were applied on the lesions and the specimens were incubated in mineralization solution (2.5mM Ca(+2) , 1.5mM PO4 (-3) , pH = 7.2) for 24 h. One-way ANOVA and Tukey's multi-comparison tests were used for statistical analysis. The pattern of enamel surface repair was studied using FE-SEM. AFM showed the formation of highly organized hierarchical structures, composed of hydroxyapatite (HA) crystals, similar to the dental enamel microstructure. ANOVA procedure showed significant effect of peptide treatment on the calculated SMR% (p < 0.001). Tukey's test revealed that peptide treated groups had significantly higher values of SMR%. In conclusion, LRAP is able to regulate the formation of HA and enhances the remineralization of acid-etched enamel as a surface treatment agent.

Immobilizing osteogenic growth peptide with and without fibronectin on a titanium surface: effects of loading methods on mesenchymal stem cell differentiation

In this study, to improve the osseointegration of implants, osteogenic growth peptide (OGP) and fibronectin (FN) were loaded within mineral, which was formed on titanium, through adsorption and coprecipitation methods. The release profiles of OGP loaded by either adsorption or coprecipitation and the effects of the loading methods to immobilize OGP with and without FN on rat mesenchymal stem cell (rMSC) osteogenic differentiation were studied. The coprecipitation approach slightly reduced the initial burst release, while the adsorption approach provided a more sustained release. Dual loading of OGP and FN further improved cell attachments compared with either OGP or FN alone. Dually loaded OGP and FN also had a positive impact on rMSC proliferation and osteogenic differentiation. The difference in methods of loading OGP with and without FN also had some effects on osteogenic differentiation. Compared with coprecipitated OGP alone, adsorbed OGP enhanced later differentiation, such as osteocalcin secretion and matrix mineralization. Simultaneously adsorbed OGP and FN led to higher proliferation and higher osteogenic differentiation in both early and late stages compared with sequentially loaded OGP and FN. rMSC culture clearly indicated that simultaneously adsorbed OGP and FN could improve osseointegration, and this treatment represents a potential method for effective surface modification of dental and orthopedic implants.

A preliminary study on amelogenin-loaded electrospun scaffolds

Amelogenin is a major enamel matrix protein onto which developing enamel forms. In the realm of tissue engineering, amelogenin has been studied and applied to periodontal and wound healing applications. This study introduces the first attempts of incorporating amelogenin within an electrospun scaffold. Amelogenin was extracted from porcine unerupted tooth buds and electrospun with poly(glycolic acid) and poly(ϵ-caprolactone). Protein release kinetics, mechanical properties, fiber diameter, mineralization potential, and cell adhesion properties of the amelogenin-blended scaffolds were studied and compared to the electrospun poly(glycolic acid) and poly(ϵ-caprolactone) controls. Electrospun scaffolds loaded with amelogenin were incubated in phosphate buffer saline. Protein quantification and morphological and mechanical analyses were conducted on the degraded scaffolds, and the incubated phosphate buffer saline was also tested for protein content. Fresh scaffolds were incubated overnight in conventional simulated body fluid to evaluate mineralization potential of the incorporated electrospun amelogenin. Human dermal fibroblasts were seeded onto scaffolds, incubated overnight, cryosectioned, and stained with 4′,6-diamidino-2-phenylindole to determine cellular adhesive properties. The incorporation of 5 mg/mL amelogenin into electrospun scaffolds improved mechanical properties (in poly(ϵ-caprolactone) scaffolds), increased fiber mineralization (in poly(glycolic acid) scaffolds), and improved human dermal fibroblast adhesion (in poly(ϵ-caprolactone) scaffolds). The presented results suggest that amelogenin can be used for multiple tissue engineering applications in the form of an additive to an electrospun scaffold.

Identification of novel amelogenin-binding proteins by proteomics analysis

Emdogain (enamel matrix derivative, EMD) is well recognized in periodontology. It is used in periodontal surgery to regenerate cementum, periodontal ligament, and alveolar bone. However, the precise molecular mechanisms underlying periodontal regeneration are still unclear. In this study, we investigated the proteins bound to amelogenin, which are suggested to play a pivotal role in promoting periodontal tissue regeneration. To identify new molecules that interact with amelogenin and are involved in osteoblast activation, we employed coupling affinity chromatography with proteomic analysis in fractionated SaOS-2 osteoblastic cell lysate. In SaOS-2 cells, many of the amelogenin-interacting proteins in the cytoplasm were mainly cytoskeletal proteins and several chaperone molecules of heat shock protein 70 (HSP70) family. On the other hand, the proteomic profiles of amelogenin-interacting proteins in the membrane fraction of the cell extracts were quite different from those of the cytosolic-fraction. They were mainly endoplasmic reticulum (ER)-associated proteins, with lesser quantities of mitochondrial proteins and nucleoprotein. Among the identified amelogenin-interacting proteins, we validated the biological interaction of amelogenin with glucose-regulated protein 78 (Grp78/Bip), which was identified in both cytosolic and membrane-enriched fractions. Confocal co-localization experiment strongly suggested that Grp78/Bip could be an amelogenin receptor candidate. Further biological evaluations were examined by Grp78/Bip knockdown analysis with and without amelogenin. Within the limits of the present study, the interaction of amelogenin with Grp78/Bip contributed to cell proliferation, rather than correlate with the osteogenic differentiation in SaOS-2 cells. Although the biological significance of other interactions are not yet explored, these findings suggest that the differential effects of amelogenin-derived osteoblast activation could be of potential clinical significance for understanding the cellular and molecular bases of amelogenin-induced periodontal tissue regeneration.

Effect of Emdogain enamel matrix derivative and BMP-2 on the gene expression and mineralized nodule formation of alveolar bone proper-derived stem/progenitor cells

The objective of this study was to evaluate the effect of Emdogain (Enamel Matrix Derivative, EMD) and Bone Morphogenetic Protein-2 (BMP-2), either solely or in combination, on the gene expression and mineralized nodule formation of alveolar bone proper-derived stem/progenitor cells. Stem/progenitor cells were isolated from human alveolar bone proper, magnetically sorted using STRO-1 antibodies, characterized flowcytometrically for their surface markers' expression, and examined for colony formation and multilineage differentiation potential. Subsequently, cells were treated over three weeks with 100 μg/ml Emdogain (EMD-Group), or 100 ng/ml BMP-2 (BMP-Group), or a combination of 100 ng/ml BMP-2 and 100 μg/ml Emdogain (BMP/EMD-Group). Unstimulated stem/progenitor cells (MACS(+)-Group) and osteoblasts (OB-Group) served as controls. Osteogenic gene expression was analyzed using RTq-PCR after 1, 2 and 3 weeks (N = 3/group). Mineralized nodule formation was evaluated by Alizarin-Red staining. BMP and EMD up-regulated the osteogenic gene expression. The BMP Group showed significantly higher expression of Collagen-I, III, and V, Alkaline phosphatase and Osteonectin compared to MACS(+)- and OB-Group (p < 0.05; Two-way ANOVA/Bonferroni) with no mineralized nodule formation. Under in-vitro conditions, Emdogain and BMP-2 up-regulate the osteogenic gene expression of stem/progenitor cells. The combination of BMP-2 and Emdogain showed no additive effect and would not be recommended for a combined clinical stimulation.

Histological comparison of healing following tooth extraction with ridge preservation using enamel matrix derivatives versus Bio-Oss Collagen: a pilot study

The goal of the present clinical study was to evaluate new bone formation in human extraction sockets augmented with enamel matrix derivatives (EMD) and Bio-Oss Collagen. Patients with symmetrical single-rooted teeth in the bilateral quadrants of the upper jaw condemned for extraction participated in this study. Following extraction, the sockets (20 sockets) were randomly augmented using either EMD or Bio-Oss Collagen. After 3 months of healing, bone biopsies were obtained and prepared for histological analyses. Dental implants were then placed. Implant stability quotient (ISQ) readings were obtained for each implant at the time of surgery and at 1 and 3 months postoperatively. The mean new bone formation was 34.57 ± 25.67% in the EMD sites and 28.80 ± 16.14% in the Bio-Oss Collagen sites. There was no significant difference between the groups. The ISQ values were significantly higher for the implants placed in the EMD sites at the first and third months, but no significant differences were observed in the ISQ values for the implants placed in the Bio-Oss Collagen sites. The augmentation of the extraction sockets with EMD or Bio-Oss Collagen leads to similar behaviour in bone regeneration.

Micro- and nanoscale technologies for tissue engineering and drug discovery applications

Micro- and nanoscale technologies are emerging as powerful enabling tools for tissue engineering and drug discovery. In tissue engineering, micro- and nanotechnologies can be used to fabricate biomimetic scaffolds with increased complexity and vascularization. Furthermore, these technologies can be used to control the cellular microenvironment (i.e., cell-cell, cell-matrix and cell-soluble factor interactions) in a reproducible manner and with high temporal and spatial resolution. In drug discovery, miniaturized platforms based on micro- and nanotechnology can be used to precisely control the fluid flow, enable high-throughput screening, and minimize sample or reagent volumes. In addition, these systems enhance reproducibility and significantly reduce reaction times. This paper reviews the recent developments in the field of micro- and nanoscale technology and gives examples of their tissue engineering and drug discovery applications.

Titania-polymeric powder coatings with nano-topography support enhanced human mesenchymal cell responses

Titanium implant osseointegration is dependent on the cellular response to surface modifications and coatings. Titania-enriched nanocomposite polymeric resin coatings were prepared through the application of advanced ultrafine powder coating technology. Their surfaces were readily modified to create nano-rough (<100 nm) surface nano-topographies that supported human embryonic palatal mesenchymal cell responses. Energy dispersive x-ray spectroscopy confirmed continuous and homogenous coatings with a similar composition and even distribution of titanium. Scanning electron microscopy (SEM) showed complex micro-topographies, and atomic force microscopy revealed intricate nanofeatures and surface roughness. Cell counts, mitochondrial enzyme activity reduction of yellow 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to dark purple, SEM, and inverted fluorescence microscopy showed a marked increase in cell attachment, spreading, proliferation, and metabolic activity on the nanostructured surfaces. Reverse Transcription- Polymerase Chain Reaction (RT-PCR) analysis showed that type I collagen and Runx2 expression were induced, and Alizarin red staining showed that mineral deposits were abundant in the cell cultures grown on nanosurfaces. This enhancement in human mesenchymal cell attachment, growth, and osteogenesis were attributed to the nanosized surface topographies, roughness, and moderate wetting characteristics of the coatings. Their dimensional similarity to naturally occurring matrix proteins and crystals, coupled with their increased surface area for protein adsorption, may have facilitated the response. Therefore, this application of ultrafine powder coating technology affords highly biocompatible surfaces that can be readily modified to accentuate the cellular response.

Effects of amelogenin on proliferation, differentiation, and mineralization of rat bone marrow mesenchymal stem cells in vitro

The aim of this study was to clarify the function of amelogenin, the major protein of enamel matrix derivative, on the proliferation, differentiation, and mineralization of cultured rat bone marrow stem cells (BMSCs), toward the establishment of future bone regenerative therapies. No differences in the morphology of BMSCs or in cell numbers were found between amelogenin addition and additive-free groups. The promotion of ALPase activity and the formation of mineralized nodules were detected at an early stage in amelogenin addition group. In quantitative real-time RT-PCR, mRNA expression of osteopontin, osteonectin, and type I collagen was promoted for 0.5 hours and 24 hours by addition of amelogenin. The mRNA expression of osteocalcin and DMP-1 was also stimulated for 24 hours and 0.5 hours, respectively, in amelogenin addition group. These findings clearly indicate that amelogenin promoted the differentiation and mineralization of rat BMSCs but did not affect cell proliferation or cell morphology.

Premature osteoblast clustering by enamel matrix proteins induces osteoblast differentiation through up-regulation of connexin 43 and N-cadherin

In recent years, enamel matrix derivative (EMD) has garnered much interest in the dental field for its apparent bioactivity that stimulates regeneration of periodontal tissues including periodontal ligament, cementum and alveolar bone. Despite its widespread use, the underlying cellular mechanisms remain unclear and an understanding of its biological interactions could identify new strategies for tissue engineering. Previous in vitro research has demonstrated that EMD promotes premature osteoblast clustering at early time points. The aim of the present study was to evaluate the influence of cell clustering on vital osteoblast cell-cell communication and adhesion molecules, connexin 43 (cx43) and N-cadherin (N-cad) as assessed by immunofluorescence imaging, real-time PCR and Western blot analysis. In addition, differentiation markers of osteoblasts were quantified using alkaline phosphatase, osteocalcin and von Kossa staining. EMD significantly increased the expression of connexin 43 and N-cadherin at early time points ranging from 2 to 5 days. Protein expression was localized to cell membranes when compared to control groups. Alkaline phosphatase activity was also significantly increased on EMD-coated samples at 3, 5 and 7 days post seeding. Interestingly, higher activity was localized to cell cluster regions. There was a 3 fold increase in osteocalcin and bone sialoprotein mRNA levels for osteoblasts cultured on EMD-coated culture dishes. Moreover, EMD significantly increased extracellular mineral deposition in cell clusters as assessed through von Kossa staining at 5, 7, 10 and 14 days post seeding. We conclude that EMD up-regulates the expression of vital osteoblast cell-cell communication and adhesion molecules, which enhances the differentiation and mineralization activity of osteoblasts. These findings provide further support for the clinical evidence that EMD increases the speed and quality of new bone formation in vivo.

Signal molecules-calcium phosphate coprecipitation and its biomedical application as a functional coating

In this review, the current knowledge of signal molecules-calcium phosphate coprecipitation and its biomedical application as a functional coating are described. Although signal molecules regulate a variety of cellular processes, it is difficult to sustain the regulation activity for a long term when the signal molecules are only injected in a free form. The signal molecules-calcium phosphate coprecipitation on a substrate surface is a very promising process to achieve sustained regulation activity of the signal molecules by controlled and localized delivery of the signal molecules to specific body sites (implantation sites). However, the significance of immobilizing signal molecules with calcium phosphate coatings and their biomedical application are not systematically illustrated. For this purpose, the presently existing coprecipitation methods and strategies on biomedical application are summarized and discussed.

Preparation, release profiles and antibacterial properties of vancomycin-loaded Ca-P coating titanium alloy plate

The aim of the study was to explore the feasibility of the Ca-P coating titanium alloy plate to be used as the vancomycin drug-delivery system by biomimetic coating technology. Through the X-ray diffraction study, the main components of the coatings were identified as octocalcium phosphate. The in vitro vancomycin release, bacteriostasis activity to Staphylococcus aureus (S. aureus), the scanning electron microscope (SEM) image and osteoblast adhesion and proliferation test of vancomycin-loaded Ca-P coating plate were evaluated. The bacteriostatic activity of the vancomycin-loaded Ca-P coating plate showed a continuous drug release and had an inhibitory effect on the growth of the S. aureus. In vitro osteoblast culture results showed that the Ca-P coating plate loaded with or without the vancomycin both obviously promoted the osteoblast attachment. It was suggested that the vancomycin-loaded Ca-P coating may be compounded in the surface of the internal fixators to reduce the incidence of the implant-associated infection.

Biomimetic coatings for bone tissue engineering of critical-sized defects

The repair of critical-sized bone defects is still challenging in the fields of implantology, maxillofacial surgery and orthopaedics. Current therapies such as autografts and allografts are associated with various limitations. Cytokine-based bone tissue engineering has been attracting increasing attention. Bone-inducing agents have been locally injected to stimulate the native bone-formation activity, but without much success. The reason is that these drugs must be delivered slowly and at a low concentration to be effective. This then mimics the natural method of cytokine release. For this purpose, a suitable vehicle was developed, the so-called biomimetic coating, which can be deposited on metal implants as well as on biomaterials. Materials that are currently used to fill bony defects cannot by themselves trigger bone formation. Therefore, biological functionalization of such materials by the biomimetic method resulted in a novel biomimetic coating onto different biomaterials. Bone morphogenetic protein 2 (BMP-2)-incorporated biomimetic coating can be a solution for a large bone defect repair in the fields of dental implantology, maxillofacial surgery and orthopaedics. Here, we review the performance of the biomimetic coating both in vitro and in vivo.

Orthopedic coating materials: considerations and applications

The host response to titanium and its alloys is not always favorable, as a fibrous layer may form at the skeletal tissue-device interface, causing aseptic loosening. Therefore, a great deal of current orthopedic research is focused on developing implants with improved osseointegration properties in order to increase their clinical success. Promising new studies have been reported regarding coating the currently available implants with various coating materials and techniques so as to improve the long-term stability of implants. This article will discuss various coating materials developed, their advantages and disadvantages as coating materials and their biological performance.

Incorporation of bovine serum albumin into biomimetic coatings on titanium with high loading efficacy and its release behavior

Bovine serum albumin (BSA) was employed as a model protein to study its loading efficiency into a calcium phosphate (CaP) coating on titanium substrates. It is found that the protein loading efficiency can be adjusted by varying the specific configurations of the coating system such as simulated body fluid (SBF) volume, solution height and container selection for the SBF. A BSA loading efficiency as high as 90% was achieved when the ratio of the substrate surface area to modified SBF (m-SBF) volume was as high as 0.072. The release of BSA from the biomimetic coatings was also investigated in vitro. A sustained release was achieved although a large quantity of BSA was still trapped in the coating after 15 days of immersion in a phosphate buffer solution. A much faster release rate would be expected when the coating is implanted in vivo due to the active involvement of osteoclast cells and enzymes.

Proliferation and differentiation of MC3T3-E1 cells on calcium phosphate/chitosan coatings

The incorporation of chitosan into electro-deposited calcium phosphate (CaP) coatings increases bone marrow stromal cell attachment. We hypothesized that such electrodeposited CaP/chitosan coatings can also enhance the proliferative ability and differentiation potential of osteoblasts. To verify this hypothesis, we cultured osteoblast-like MC3T3-E1 cells on these CaP coatings. It was found that MC3T3-E1 cells cultured on the electrodeposited CaP/chitosan coatings had cell proliferation rates higher than those on the electrodeposited CaP coatings. At the same time, both alkaline phosphatase activity and collagen expression were increased, and both bone sialoprotein and osteocalcin genes were up-regulated when MC3T3-E1 cells were cultured on the electrodeposited CaP/chitosan coatings. Additionally, within the range of selected chitosan concentrations in solution, no significant difference was found between the CaP/chitosan coatings. Our results suggest that the electrodeposited CaP/chitosan coatings are favorable to the proliferation and differentiation of MC3T3-E1 cells, which may endow them with great potential for future applications.

Effect of chlorhexidine digluconate on different cell types: a molecular and ultrastructural investigation

Although several studies have shown that chlorhexidine digluconate (CHX) has bactericidal activity against periodontal pathogens and exerts toxic effects on periodontal tissues, few have been directed to evaluate the mechanisms underlying its adverse effects on these tissues. Therefore, the aim of the present study was to investigate the in vitro cytotoxicity of CHX on cells that could represent common targets for its action in the surgical procedures for the treatment of periodontitis and peri-implantitis and to elucidate its mechanisms of action. Osteoblastic, endothelial and fibroblastic cell lines were exposed to various concentrations of CHX for different times and assayed for cell viability and cell death. Also analysis of mitochondrial membrane potential, intracellular Ca2+ mobilization and reactive oxygen species (ROS) generation were done in parallel, to correlate CHX-induced cell damage with alterations in key parameters of cell homeostasis. CHX affected cell viability in a dose and time-dependent manners, particularly in osteoblasts. Its toxic effect consisted in the induction of apoptotic and autophagic/necrotic cell deaths and involved disturbance of mitochondrial function, intracellular Ca2+ increase and oxidative stress. These data suggest that CHX is highly cytotoxic in vitro and invite to a more cautioned use of the antiseptic in the oral surgical procedures.