Effect of Octacalcium-Phosphate-Modified Micro/Nanostructured Titania Surfaces on Osteoblast Response

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Osteogenic differentiation and proliferation potentials of human bone marrow and umbilical cord-derived mesenchymal stem cells on the 3D-printed hydroxyapatite scaffolds

Mesenchymal stem cells (MSCs) are a promising candidate for bone repair. However, the maintenance of MSCs injected into the bone injury site remains inefficient. A potential approach is to develop a bone-liked platform that incorporates MSCs into a biocompatible 3D scaffold to facilitate bone grafting into the desired location. Bone tissue engineering is a multistep process that requires optimizing several variables, including the source of cells, osteogenic stimulation factors, and scaffold properties. This study aims to evaluate the proliferation and osteogenic differentiation potentials of MSCs cultured on 2 types of 3D-printed hydroxyapatite, including a 3D-printed HA and biomimetic calcium phosphate-coated 3D-printed HA. MSCs from bone marrow (BM-MSCs) and umbilical cord (UC-MSCs) were cultured on the 3D-printed HA and coated 3D-printed HA. Scanning electron microscopy and immunofluorescence staining were used to examine the characteristics and the attachment of MSCs to the scaffolds. Additionally, the cell proliferation was monitored, and the ability of cells to differentiate into osteoblast was assessed using alkaline phosphatase (ALP) activity and osteogenic gene expression. The BM-MSCs and UC-MSCs attached to a plastic culture plate with a spindle-shaped morphology exhibited an immunophenotype consistent with the characteristics of MSCs. Both MSC types could attach and survive on the 3D-printed HA and coated 3D-printed HA scaffolds. The MSCs cultured on these scaffolds displayed sufficient osteoblastic differentiation capacity, as evidenced by increased ALP activity and the expression of osteogenic genes and proteins compared to the control. Interestingly, MSCs grown on coated 3D-printed HA exhibited a higher ALP activity and osteogenic gene expression than those cultured on the 3D-printed HA. The finding indicated that BM-MSCs and UC-MSCs cultured on the 3D-printed HA and coated 3D-printed HA scaffolds could proliferate and differentiate into osteoblasts. Thus, the HA scaffolds could provide a suitable and favorable environment for the 3D culture of MSCs in bone tissue engineering. Additionally, biomimetic coating with octacalcium phosphate may improve the biocompatibility of the bone regeneration scaffold.

Metal Ion Augmented Mussel Inspired Polydopamine Immobilized 3D Printed Osteoconductive Scaffolds for Accelerated Bone Tissue Regeneration

Critical bone defects with a sluggish rate of auto-osteoconduction and imperfect reconstruction are motivators for the development of an alternate innovative approach for the regeneration of bone. Tissue engineering for bone regeneration signifies an advanced way to overcome this problem by creating an additional bone tissue substitute. Among different fabrication techniques, the 3D printing technique is obviously the most efficient and advanced way to fabricate an osteoconductive scaffold with a controlled porous structure. In the current article, the polycarbonate and polyester diol based polyurethane-urea (P12) was synthesized and 3D porous nanohybrid scaffolds (P12/TP-nHA) were fabricated using the 3D printing technique by incorporating the osteoconductive nanomaterial titanium phosphate adorned nanohydroxyapatite (TP-nHA). To improve the bioactivity, the surface of the fabricated scaffolds was modified with the immobilized biomolecule polydopamine (PDA) at room temperature. XPS study as well as the measurement of surface wettability confirmed the higher amount of PDA immobilization on TP-nHA incorporated nanohybrid scaffolds through the dative bone formation between the vacant d orbital of the incorporated titanium ion and the lone pair electron of the catechol group of dopamine. The incorporated titanium phosphate (TP) increased the tensile strength (53.1%) and elongation at break (96.8%) of the nanohybrid composite as compared to pristine P12. Moreover, the TP incorporated nanohybrid scaffold with calcium and phosphate moieties and a higher amount of immobilized active biomolecule improved the in vitro bioactivity, including the cell viability, cell proliferation, and osteogenic gene expression using hMSCs, of the fabricated nanohybrid scaffolds. A rat tibia defect model depicted that the TP incorporated nanohybrid scaffold with immobilized PDA enhanced the in vivo bone regeneration ability compared to the control sample without revealing any organ toxicity signifying the superior osteogenic bioactivity. Thus, a TP augmented polydopamine immobilized polyurethane-urea based nanohybrid 3D printed scaffold with improved physicochemical properties and osteogenic bioactivity could be utilized as an excellent advanced material for bone regeneration substitute.

Drug infused Al2O3-bioactive glass coatings toward the cure of orthopedic infection

A unique implant coated substrate with dual-drug-eluting system exhibiting antibacterial, anti-inflammatory, and bone regenerative capacity has been fabricated using spray pyrolysis deposition (SPD) method. Bioglass (BG) and BG-alumina (BG-Al) composites coatings with different concentrations of Al incorporated on BG network over the Cp-Ti substrate were fabricated using SPD technique. Phase purity of BG and BG-Al composites were analyzed by XRD in which Na₂Ca₂Si₃O₉ and β-Na₂Ca₄(PO₄)₂SiO₄) and Na_7.15(Al_7.2Si_8.8O₃₂) phases were formed. Surface morphology of the coated substrates was analyzed by SEM. Uniformity of the coatings were evaluated by surface profilometer and the uniform distribution the nanoparticles were confirmed with Elemental mapping. Systematically, each apatite layer formation on coated substrate was confirmed by immersing the samples for 1, 3, and 7 days in simulated body fluid and the needle-like structure was characterized using SEM. Cumulative release of Tetracycline hydrochloride (Tet) antibiotic and Dexamethasone (Dex) anti-inflammatory drug-loaded BG-Al and BG-Al composite-coated substrate were studied for 24 h. Antibacterial activity of the coated substrates were evaluated by time-dependent growth inhibition and minimal inhibitory concentration (MIC) assays in which BG-Al and BG-Al composite loaded with Tet showed considerable growth inhibition against S. aureus. Osteoblast-like cells (MG-63) exhibited profound proliferation with no cytotoxic effects which was due to release of Dex drug-coated substrates. Thus, surface modification of Cp-Ti substrate with BG, BG-Al composites coatings loaded with Tet and Dex drug can be considered for post-operative orthopedic implant infection application.

Osteoporotic bone recovery by a bamboo-structured bioceramic with controlled release of hydroxyapatite nanoparticles

While most bone defects can be repaired spontaneously, the healing process can be complicated due to insufficient bone regeneration when osteoporosis occurs. Synthetic materials that intrinsically stimulate bone formation without inclusion of exogenous cells or growth factors represent a highly desirable alternative to current grafting strategies for the management of osteoporotic defects. Herein, we developed a series of hydroxyapatite bioceramics composed of a microwhiskered scaffold (wHA) reinforced with multiple layers of releasable hydroxyapatite nanoparticles (nHA). These novel bioceramics (nwHA) are tunable to optimize the loading amount of nHA for osteoporotic bone formation. The utility of nwHA bioceramics for the proliferation or differentiation of osteoporotic osteoblasts in vitro is demonstrated. A much more compelling response is seen when bioceramics are implanted in critical-sized femur defects in osteoporotic rats, as nwHA bioceramics promote significantly higher bone regeneration and delay adjacent bone loss. Moreover, the nwHA bioceramics loaded with a moderate amount of nHA can induce new bone formation with a higher degree of ossification and homogenization. Two types of osteogenesis inside the nwHA bioceramic pores were discovered for the first time, depending on the direction of growth of the new bone. The current study recommends that these tailored hybrid micro/nanostructured bioceramics represent promising candidates for osteoporotic bone repair.

Surface Properties of Octacalcium Phosphate Nanocrystals Are Crucial for Their Bioactivities

The fundamental structure-biofunction relationship of calcium phosphates (CaPs) remains unclear despite their clinical successes as important biomaterials. Herein, a series of CaP coatings with gradual change of topography and crystallinity is constructed by electrochemical deposition, and the roles of the two basic physicochemical properties are scrutinized for further understanding the mechanism behind the superior bioactivities of octacalcium phosphate (OCP). We observe a distinct modulation on cell proliferation on the prepared CaP coatings for different cells. The magnitude of the modulation seems to depend on the cellular size, and the effect is attributed mainly to the microstructure of the coatings. On the other hand, the crystallinity manifests its significance for the osteogenic property of the OCP coatings. Further transmission electron microscopy analysis and density functional theory calculations reveal a surface rich in HPO₄ ^2- for the high-crystalline OCP nanocrystals. The results highlight that the nanocrystal surface properties of the OCP coatings, including the periodic structure and the HPO₄ ^2- composition, may play significant roles surpassing the ion release effect in determining its osteogenic property, probably via surface spatial and/or chemical recognitions. The present findings shed light on the fundamental understanding of the structure-biofunction relationship for CaP biomaterials.

Octacalcium Phosphate Bone Substitute (Bontree®): From Basic Research to Clinical Case Study

Bone grafts used in alveolar bone regeneration can be categorized into autografts, allografts, xenografts, and synthetic bones, depending on their origin. The purpose of this study was to evaluate the effect of a commercialized octacalcium phosphate (OCP)-based synthetic bone substitute material (Bontree®) in vitro, in vivo, and in clinical cases. Material characterization of Bontree® granules (0.5 mm and 1.0 mm) using scanning electron microscopy and X-ray diffraction showed that both 0.5 mm and 1.0 mm Bontree® granules were uniformly composed mainly of OCP. The receptor activator of NF-κB ligand (RANKL) and alkaline phosphatase (ALP) activities of MG63 cells were assessed and used to compare Bontree® with a commercial biphasic calcium phosphate ceramic (MBCP+TM). Compared with MBCP+TM, Bontree® suppressed RANKL and increased ALP activity. A rabbit tibia model used to examine the effects of granule size of Bontree® grafts showed that 1.0 mm Bontree® granules had a higher new bone formation ability than 0.5 mm Bontree® granules. Three clinical cases using Bontree® for ridge or sinus augmentation are described. All eight implants in the three patients showed a 100% success rate after 1 year of functional loading. This basic research and clinical application demonstrated the safety and efficacy of Bontree® for bone regeneration.

Coherent surface structure induces unique epitaxial overgrowth of metastable octacalcium phosphate on stable hydroxyapatite at critical fluoride concentration

The phase transformation from soluble calcium phosphates to less-soluble hydroxyapatite (HAP) is a thermodynamically natural route. This process is irreversible, and effective use of poorly reactive HAP to repair teeth that have no cellular metabolism remains challenging. However, this thermodynamically controlled transformation may apparently be reversed through the fast nucleation and growth of metastable phases, leading to a reactive HAP surface. Here, the assembled HAP-nanorod phase is demonstrated to change into the metastable octacalcium phosphate (OCP) phase in a calcium phosphate solution containing 0.8 ppm fluoride. Grown OCPs display parallel surface streaks and their 11¯0 and 00l (l: odd) electron-diffraction spots are often not visible. The streaked, elongated OCP gradually grows into large plates with flat surfaces that exhibit an intense11¯0 spot. Crystal-structure models reveal that the unique epitaxial overgrowth of OCP on HAP occurs since both materials share coherent {100} faces, resulting in the distinctive disappearance of 11¯0 and 00l OCP spots. A polysynthetic twin model that reliably explains this disappearance is proposed for the growth of OCP. This apparent reverse phase transformation produces hybrid calcium phosphates consisting of HAP cores and highly reactive outer OCP layers that are promising for the repair of dentin caries. STATEMENT OF SIGNIFICANCE: This paper demonstrates important and interesting finding regarding formation of calcium phosphates in relation to their crystal structures. We first show that hydroxyapatite (HAP), the major constituent of human teeth and bone, can reversely change to its precursor, octacalcium phosphate (OCP), contrary to thermodynamic-stability rule. This apparent reverse phase transformation occurs through sharing the coherent {100} faces of both materials under controlled fluoride concentration. Nanoscale similarity of two crystal surfaces enables structurally shared epitaxial overgrowth of OCP on HAP aided by faster growth rate of OCP than that of HAP. This reaction produces hybrid crystal consisting of outer OCP and core HAP, that has not been known before and is able to be applied to dentin caries repair.

Hydroxyapatite-modified micro/nanostructured titania surfaces with different crystalline phases for osteoblast regulation

Surface structures and physicochemical properties critically influence osseointegration of titanium (Ti) implants. Previous studies have shown that the surface with both micro- and nanoscale roughness may provide multiple features comparable to cell dimensions and thus efficiently regulate cell-material interaction. However, less attention has been made to further optimize the physicochemical properties (e.g., crystalline phase) and to further improve the bioactivity of micro/nanostructured surfaces. Herein, micro/nanostructured titania surfaces with different crystalline phases (amorphous, anatase and anatase/rutile) were prepared and hydroxyapatite (HA) nanorods were deposited onto the as-prepared surfaces by a spin-assisted layer-by-layer assembly method without greatly altering the initial multi-scale morphology and wettability. The effects of crystalline phase, chemical composition and wettability on osteoblast response were investigated. It is noted that all the micro/nanostructured surfaces with/without HA modification presented superamphiphilic. The activities of MC3T3-E1 cells suggested that the proliferation trend on the micro/nanostructured surfaces was greatly influenced by different crystalline phases, and the highest proliferation rate was obtained on the anatase/rutile surface, followed by the anatase; but the cell differentiation and extracellular matrix mineralization were almost the same among them. After ultrathin HA modification on the micro/nanostructured surfaces with different crystalline phases, it exhibited similar proliferation trend as the original surfaces; however, the cell differentiation and extracellular matrix mineralization were significantly improved. The results indicate that the introduction of ultrathin HA to the micro/nanostructured surfaces with optimized crystalline phase benefits cell proliferation, differentiation and maturation, which suggests a favorable biomimetic microenvironment and provides the potential for enhanced implant osseointegration in vivo.

β-Tricalcium phosphate contained beaded-fiber scaffolds characterized by high early osteoinductive activity for vascularized bone regeneration

The calcium phosphate component and surface topology of a scaffold are considered the two main factors that influence osteogenic differentiation. This research reports a one-step but effective scaffold preparation method that can regulate the morphology of nanofibers and control the distribution and release behavior of calcium phosphate nanoparticles (CaPs). Two beaded-on-string CaPs-loaded electrospun scaffolds (PT7.5 and PT4.5) with composite microstructures of microbeads and nanofibers were fabricated by adjusting the concentration of the electrospinning solution. The presence of the composite microstructure was conducive to the surface exposure and sustained release of bioactive components, which in turn could significantly promote the biomineralization and protein adsorption of the scaffold. A study of the human umbilical vein endothelial cells (HUVECs) and rat-bone marrow-derived mesenchymal stem cells (rBMSCs) revealed that cells cultured on scaffolds with composite microstructures (especially PT4.5) could enhance tube formation of the HUVECs and osteogenic differentiation of rBMSCs. The PT4.5 with significantly different microbead and nanofiber sizes presented the high potential to improve the early osteoinductive activity and angiogenesis of the CaPs-loaded electrospun scaffold and expand its advantage in bone regeneration.

New insights into bioactivity of ceria-stabilized zirconia: Direct bonding to bone-like hydroxyapatite at nanoscale

Osseointegration resulting from biomineralization means tight bone-implant attachment, which is clinically essential for successful dental implant treatment. The osseointegration ability of ceria-stabilized zirconia, a promising implant material, has been questionable and is unclear despite its clinical use due to zirconia's bioinert nature. The purpose of this research was to investigate the osseointegration ability of ceria-stabilized zirconia by clarifying its bioactivity. Here we show that ceria-stabilized zirconia is highly bioactive, contrary to the general consensus. Transmission electron microscopy observation revealed that the zirconia nanocrystals of a ceria-stabilized zirconia substrate directly bonded to osteoblastic cell-precipitated hydroxyapatite crystals at lattice fringe scale. This bonding was achieved without chemical treatment of the substrate surface before use. Hydroxyapatite crystals exhibited a morphology of flexible nanofibers less than 10 nm wide with nanometer-thick plates filling the spaces between nanofibers. Elemental analysis of the hydroxyapatites showed that they contained alkaline metal cations (Na, Mg, and K) as minor elements and that their average Ca/P atomic % ratio was ~1.40, similar to those of bone apatite. High bioactivity of ceria-stabilized zirconia resulted in direct bonding to bone-like hydroxyapatite, suggesting nanoscale direct osseointegration with bone in vivo that contributes to improving the success rate of dental implant treatment.

Hydrophilic titanium surface modulates early stages of osseointegration in osteoporosis

OBJECTIVE

Using a mouse osteoporotic model, this study aimed to determine the influence of hydrophilic titanium surfaces on gene expression and bone formation during the osseointegration process.

BACKGROUND

Based on the previous evidence, it is plausible to assume that osteoporotic bone has a different potential of bone healing. Therefore, implant surface modification study that aims at enhancing bone formation to further improve short- and long-term clinical outcomes in osteoporosis is necessary.

MATERIAL AND METHODS

Fifty female, 3-month-old mice were included in this study. Osteoporosis was induced by ovariectomy (OVX, test group) in 25 mice. The further 25 mice had ovaries exposed but not removed (SHAM, control group). Seven weeks following the ovariectomy procedures, one customized implant (0.7 × 8 mm) of each surface was placed in each femur for both groups. Implants had either a hydrophobic surface (SAE) or a hydrophilic treatment surface (SAE-HD). Calcium (Ca) and phosphorus (P) content was measured by energy-dispersive X-ray spectroscopy (EDS) after 7 days. The femurs were analyzed for bone-to-implant contact (BIC) and bone volume fraction (BV) by nano-computed tomography (nano-CT) after 14 and 28 days. Same specimens were further submitted to histological analysis. Additionally, after 3 and 7 days, implants were removed and cells were collected around the implant to access gene expression profile of key osteogenic (Runx2, Alp, Sp7, Bsp, Sost, Ocn) and inflammatory genes (IL-1β, IL-10, Tnf-α, and Nos2) by qRT-PCR assay. Statistical analysis was performed by ANOVA and paired t test with significance at P < .05.

RESULTS

The amount of Ca and P deposited on the surface due to the mineralization process was higher for SAE-HD compared to SAE on the intra-group analysis. Nano-CT and histology revealed more BV and BIC for SAE-HD in SHAM and OVX groups compared to SAE. Analysis in OVX group showed that most genes (ie, ALP, Runx2) involved in the bone morphogenetic protein (BMP) signaling were significantly activated in the hydrophilic treatment.

CONCLUSION

Both surfaces were able to modulate bone responses toward osteoblast differentiation. SAE-HD presented a faster response in terms of bone formation and osteogenic gene expression compared to SAE. Hydrophilic surface in situations of osteoporosis seems to provide additional benefits in the early stages of osseointegration.

Construction of Biomimetic Natural Wood Hierarchical Porous-Structure Bioceramic with Micro/Nanowhisker Coating to Modulate Cellular Behavior and Osteoinductive Activity

Scaffolds with a biomimetic hierarchy micro/nanoscale pores play an important role in bone tissue regeneration. In this study, multilevel porous calcium phosphate (CaP) bioceramic orthopedic implants were constructed to mimic the micro/nanostructural hierarchy in natural wood. The biomimetic hierarchical porous scaffolds were fabricated by combining three-dimensional (3D) printing technology and hydrothermal treatment. The first-level macropores (∼100-600 μm) for promoting bone tissue ingrowth were precisely designed using a set of 3D printing parameters. The second-level micro/nanoscale pores (∼100-10,000 nm) in the scaffolds were obtained by hydrothermal treatment to promote nutrient/metabolite transportation. Micro- and nanoscale-sized pores in the scaffolds were recognized as in situ formation of whiskers, where the shape, diameter, and length of whiskers were modulated by adjusting the components of calcium phosphate ceramics and hydrothermal treatment parameters. These biomimetic natural wood-like hierarchical structured scaffolds demonstrated unique physical and biological properties. Hydrophilicity and the protein adsorption rate were characterized in these scaffolds. In vitro studies have identified micro/nanowhisker coating as potent modulators of cellular behavior through the onset of focal adhesion formation. In addition, histological results indicate that biomimetic scaffolds with porous natural wood hierarchical pores exhibited good osteoinductive activity. In conclusion, these findings combined suggested that micro/nanowhisker coating is a critical factor to modulate cellular behavior and osteoinductive activity.

Electrospun poly(3-hydroxybutyrate-co-4-hydroxybutyrate) /Octacalcium phosphate Nanofibrous membranes for effective guided bone regeneration

Membranes used in guided bone regeneration (GBR) are required to exhibit high mechanical strength, biocompatibility, biodegradation, osteogenic and osteoinductive potential. In our study, poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P(3HB-co-4HB))/octacalcium phosphate (OCP) (P(3HB-co-4HB)/OCP) nanofibrous membranes were fabricated by electrospinning with two different P(3HB-co-4HB) to OCP ratios (P(3HB-co-4HB):OCP = 95:5 wt% and 90:10 wt%, termed P(3HB-co-4HB)/OCP(5)and P(3HB-co-4HB)/OCP (10), respectively) for GBR. The developed P(3HB-co-4HB)/OCP nanofibrous membranes were analysed for their osteogenic and osteoinductive properties using mesenchymal stem cells (MSCs) in vitro and in a calvarial bone defect rat model. The composite P(3HB-co-4HB)/OCP nanofibrous membranes showed decreased fibre size and enhanced tensile strength compared with those of P(3HB-co-4HB) nanofibrous membranes. In the in vitro studies, the P(3HB-co-4HB)/OCP membranes facilitated cell growth and osteoblastic differentiation of MSCs and were superior to P(3HB-co-4HB) membranes. After covered on the calvarial bone defects, P(3HB-co-4HB)/OCP membranes facilitated greater neobone formation than P(3HB-co-4HB) membranes did, as the result of histological evaluation and micro-CT analysis with higher bone volume/total volume (BV/TV) ratio and bone mineral density (BMD). P(3HB-co-4HB)/OCP(10) membranes with higher OCP content showed greater stiffness and osteoinductivity than P(3HB-co-4HB)/OCP (5)membranes, demonstrating the role of OCP in the composite membranes. These results indicated that electrospun P(3HB-co-4HB)/OCP nanofibrous membranes hold promise for the clinical application of GBR.

Modulation of the mechanosensing of mesenchymal stem cells by laser-induced patterning for the acceleration of tissue reconstruction through the Wnt/β-catenin signaling pathway activation

Growing evidence suggests that the physical microenvironment can guide cell fate. However, cells sense cues from the adjacent physical microenvironment over a limited distance. In the present study, murine mesenchymal stem cells (MSCs) and murine preosteoblastic cells (MC3T3-E1) behaviors are regulated by the cell-material interface using ordered-micro and disordered-nano patterned structures on Ti implants. The optimal bone formation structure is a stable wave (horizontal direction: ridge, 2.7 µm; grooves, 5.3 µm; and vertical direction: distance, 700 µm) with the appropriate density of nano-branches (6.0 per µm²). The repeated waves provide cells with directional guidance, and the disordered branches influence cell geometry by providing different spacing and density nanostructure. And micro-nano patterned structure can provide biophysical cues to direct cell phenotype development, including cell size, shape, and orientation, to influence cellular processes including survival, growth, and differentiation. Thus, the overlaid isotropic and anisotropic cues, ordered-micro and disordered-nano patterned structures, could transfer further and alter cell shape and induce nuclear orientation by activating Wnt/β-catenin signaling to promote integrin α5, integrin β1, cadherin 2, Runx2, Opn, and Ocn. That canonical Wnt signaling inhibitor dickkopf1 further demonstrates osteogenic differentiation induced by ordered-micro and disordered-nano patterned structures, which is related to Wnt/β-catenin signaling. Our findings show the role of ordered microstructures and disordered nanostructures in modulating stem cell differentiation with potential medical applications. STATEMENT OF SIGNIFICANCE: It remains a challenge to modify poor osteogenic and osteoconductive properties of titanium alloy bases on the inherent poverty of titanium. We demonstrate that ordered microtopography and disordered nano topography pattern structure could lead to osteogenic differentiation in vitro and bone regeneration in vivo. Furthermore, the pattern structure is created through selective laser melting and alkali heat. And the structure only takes advantage of titanium itself and does not bring in active film, such as hydroxyapatite. On the other hand, we find that cell shape and orientation show angle-orientation tendency due to the polarity, which involves with mechanical signal created via patterned structure. Meanwhile, the Wnt/Ca²⁺ signaling pathway is activated.

Promoted Osteoconduction of Polyurethane-Urea Based 3D Nanohybrid Scaffold through Nanohydroxyapatite Adorned Hierarchical Titanium Phosphate

The lack of optimal physiological properties, bacterial colonization, and auto-osteoinduction, are the foremost issues of orthopedic implantations. In terms of bone healing, many researchers have reported the release of additional growth factors of the implanted biomaterials to accelerate the bone regeneration process. However, the additional growth factor may cause side effects such as contagion, nerve pain, and the formation of ectopic bone. Thus, the design of an osteoconductive scaffold having excellent biocompatibility, appropriate physicomechanical properties, and promoted auto osteoinductivity with antibacterial activity is greatly desired. In this study, 2D rodlike nanohydroxyapatite (nHA) adorned titanium phosphate (TP) with a flowerlike morphology was synthesized by a hydrothermal precipitation reaction. The nanohybrid material (nHA-TP) was incorporated into the synthesized polycaprolactone diol and spermine based thermoplastic polyurethane-urea (PUU) via in situ technique followed by salt leaching to fabricate the macroporous 3D polymer nanohybrid scaffold (PUU/nHA-TP). Structure explication of PUU was performed by NMR spectroscopy. The synthesized nanohybrid scaffold with 1% nHA-TP showed 67% increase of tensile strength and 18% improved modulus compared to the pristine PUU via formation of H-bonding or dative bonds between the metal and the amide linkage of the polyurethane or polyurea. In vitro study showing improved cell viability and proliferation of the seeded cell revealed the superior osteoconductivity of the nanohybrid scaffold. Most importantly, the in vivo experiments revealed a significant amount of bone regeneration in the nanohybrid scaffold implanted tibial site compared to the pristine scaffold without any toxic effect. Introduction of the minute amount of titanium phosphate within the adorned nHA promotes the osteoconductivity significantly by the capability of forming coordinate bonds of the titanium ion. Depending on the mechanical, physicochemical, in vitro characteristics, and in vivo osteoconductivity, the PUU/nHA-TP nanohybrid scaffold has great potential as an alternative biomaterial in bone tissue regeneration application.

Effect of the Wnt signal-RANKL/OPG axis on the enhanced osteogenic integration of a lithium incorporated surface

Bone remolding involves the formation of new bone by osteoblasts and the absorption of old bones by osteoclasts. Due to the vital role of osteoblasts and osteoclasts during bone regeneration, it might be feasible to promote osseointegration around the titanium implants by stimulating osteoblasts and inhibiting osteoclasts by modifying the surfaces of the implants. Lithium is used in the treatment of psychiatric patients, and it may be associated with osteogenesis. In this study, lithium was incorporated with sandblasted, large-grit and acid-etched titanium implants via a hydrothermal treatment. In vitro, the nano-scale surface enhanced the adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs). Moreover, the SLA-Li surface displayed a negative effect on the process of osteoclastogenesis. Further mechanism analysis indicated that the canonical Wnt/β-catenin signaling pathway was activated according to the results of RT-PCR and western blotting. More importantly, the RANKL/OPG signaling axis was also involved in these effects on the SLA-Li surface. The experiments in vivo proved that the SLA-Li surface could induce the bone formation and osseointegration during the early osseointegration after the dental implant surgery. These results suggested that bone homeostasis could be manipulated by an SLA-Li surface, which implied that this new surface might serve as a promising material for clinical application in the future.

A hydrogenated black TiO2 coating with excellent effects for photothermal therapy of bone tumor and bone regeneration

The clinical treatment of bone tumors usually brings about residual tumor cells and large bone defects after tumor removal surgery. To solve this problem, it is imperative to develop a novel implant with bi-functions for eliminating the residual tumor cells and repairing bone defects. In this study, hydrogenated black TiO₂ (H-TiO₂) coating with hierarchical micro/nano-topographies is fabricated by induction suspension plasma spraying (ISPS). The fabricated H-TiO₂ coating possessed excellent and controllable photothermal effect in inhibiting the tumor growth under 808 nm NIR laser irradiation in vitro and in vivo. The hierarchical hybrid micro/nano-structured surface and Ti-OH groups improved the adhesion, proliferation, differentiation and osteogenic gene expressions of rat bone mesenchymal stem cells (rBMSCs). These results demonstrate that the H-TiO₂ coating may be a promising implant material for the treatment of bone tumors and bone regeneration.

Healing of osteoporotic bone defects by micro-/nano-structured calcium phosphate bioceramics

The micro-/nano-structured calcium phosphate bioceramic exhibited a higher new bone substitution rate in an osteoporotic bone defect rat model.

Improved osteoblast adhesion and osseointegration on TiO2 nanotubes surface with hydroxyapatite coating

To improve initial osteoblast adhesion and subsequent osseointegration, TiO₂ nanotubes layer was constructed on the titanium (Ti) surface by anodic oxidation (AO), with an additional hydroxyapatite (HA) coating to form the AO/HA surface. Tests on in vitro cellular activity displayed that the AO surface, especially the AO/HA surface, promoted initial adhesion, proliferation and differentiation of osteoblast cells. The modified AO and AO/HA surfaces further presented an up-regulated gene expression of osteogenic and adhesion markers collagen type 1 (COL), osteopontin (OPN), osteocalcin (OCN) and vinculin. In addition, in vivo experiments with a rat model demonstrated that the AO surface, particularly the AO/HA surface, achieved earlier osseointegration and a superior bone bonding ability compared with Ti. Our study shed light on a synergistic role played by nanotopography and HA in promoting osteoblast adhesion, proliferation, differentiation and osseointegration, thus suggesting a promising method for better modifying the implant surface.

Loading icariin on titanium surfaces by phase-transited lysozyme priming and layer-by-layer self-assembly of hyaluronic acid/chitosan to improve surface osteogenesis ability

Purpose

Icariin (ICA) is one of the main active constituents of Herba Epimedii for improving osteogenesis. It is necessary to create a simple and efficient method to load ICA onto the surface of titanium (Ti) implant. The purpose of this study was to establish a local ICA delivery system via a layer-by-layer (LbL) self-assembly system on phase-transited lysozyme (PTL)-primed Ti surface.

Materials and methods

A PTL nanofilm was first firmly coated on the pristine Ti. Then, the ICA-loaded hyaluronic acid/chitosan (HA/CS) multilayer was applied via the LbL system to form the HA/CS-ICA surface. This established HA/CS-ICA surface was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The ICA release pattern of the HA/CS-ICA surface was also examined. MC3T3-E1 osteoblast culture test and a rat model were used to evaluate the effects of the HA/CS-ICA surface in vitro and in vivo.

Results

SEM, XPS and contact angle measurement demonstrated successful fabrication of the HA/CS-ICA surface. The HA/CS-ICA surfaces with different ICA concentrations revealed a controlled release profile of ICA during a 2-week monitoring span. Osteoblasts grown on the coated substrates displayed higher adhesion, viability, proliferation and ALP activity than those on the polished Ti surface. Furthermore, in vivo histological evaluation revealed much obvious bone formation in the ICA-coated group by histological staining and double fluorescent labeling at 2 weeks after implantation.

Conclusion

The present study demonstrated that ICA-immobilized HA/CS multilayer on the PTL-primed Ti surface had a sustained release pattern of ICA which could promote the osteogenesis of osteoblasts in vitro and improve early osseointegration in vivo. This study provides a novel method for creating a sustained ICA delivery system to improve osteoblast response and osseointegration.

Synergistic effects of titania nanotubes and silicon to enhance the osteogenic activity

In this study, titania nanotubes (TNTs) incorporating silicon (Si) were formed on Ti disks using anodization and electron beam evaporation (EBE) technology to improve the osteogenic activity. The amount of Si was exquisitely adjusted by controlling the duration of EBE to optimize the biofunctionality. As the Si was incorporated, the samples exhibited hydrophilic surfaces. Long lasting and controllable Si release was observed from the EBE-modified samples without cytotoxicity. Moreover, initial cell adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells were evaluated. The results showed a notable enhancement of spreading, osteogenesis and differentiation of cells on silicon-coated TNTs (Si-TNTs). In particular, samples with highest amount of silicon (∼5.93% Si) displayed greatest augmentation of ALP activity, osteogenic-related gene expression and mineralization compared to the others in the present study. It was indicated that the modification with TNTs and appropriated Si content resulted in enhanced osteoblastic spreading, proliferation and differentiation, and therefore has the potential for future applications in the field of orthopedics.

Bacterial Inhibition and Osteoblast Adhesion on Ti Alloy Surfaces Modified by Poly(PEGMA- r-Phosmer) Coating

We have synthesized and immobilized PEGMA₅₀₀-Phosmer to Ti6Al4V surfaces by a simple procedure to reduce bacteria-associated infection without degrading the cell response. Adhered bacteria coverage was lessened to 1% on polymer-coated surfaces when exposed to Escherichia coli, Staphylococcus epidermidis, and Streptococcus mutans. Moreover, PEGMA₅₀₀-Phosmer and homoPhosmer coatings presented better responses to MC3T3-E1 preosteoblast cells when compared with the results for PEGMA₂₀₀₀-Phosmer-coated and raw Ti alloy surfaces. The behavior of balancing bacterial inhibition and cell attraction of the PEGMA₅₀₀-Phosmer coating was explained by the grafted phosphate groups, with an appropriate PEG brush length facilitating greater levels of calcium deposition and further fibronectin adsorption when compared with that of the raw Ti alloy surface.

Role of Osteogenic Coatings on Implant Surfaces in Promoting Bone-To-Implant Contact in Experimental Osteoporosis: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the role of osteogenic coatings (placement of a thin film of organic and inorganic osteoinductive and osteoproliferative materials) on implant surfaces in augmenting bone-to-implant contact (BIC) in osteoporotic bone.

DATA SOURCES

To answer the focused question "Do osteogenic coatings on implant surfaces increase BIC in osteoporotic bone?" PubMed/MEDLINE, EMBASE, ISI Web of Knowledge, Scopus, and Google-Scholar databases were searched till June 2017 using different combinations of the following key words: bone-to-implant contact, coating, implant surface, osseointegration, and osteoporosis. Letters to the Editor, review articles, case-reports/case-series, and commentaries were excluded.

RESULTS

Six animal studies were included, in which osteoporosis was induced by bilateral ovariectomy. In all studies, implant surface roughness was increased by various osteogenic surface coatings including alumina, hydroxyapatite, calcium phosphate, and zoledronic acid. Five studies showed that bone volume and BIC are significantly higher around implants with coated surfaces than noncoated implants. In 1 study, there was no difference in BIC around coated and noncoated implants.

CONCLUSION

Although experimental studies have shown that osteogenic coatings are effective in enhancing BIC, their clinical relevance requires further investigations.

Does incorporating collagen and chondroitin sulfate matrix in implant surfaces enhance osseointegration? A systematic review and meta-analysis

Implant surface modification has been used to improve osseointegration. However, evidence regarding improved new bone formation (NBF) and osseointegration with the use of collagen-chondroitin sulfate (CS) matrix coated implants remains unclear. The aim of this study was to assess the efficacy of collagen-CS matrix coating on the osseointegration of implants. The focused question was "Does the incorporation of collagen-CS matrix in implant surfaces influence osseointegration?" To answer the question, indexed databases were searched up to July 2017 using various combinations of the key words "collagen", "chondroitin sulfate", "osseointegration", and "implants". The initial literature search identified 497 articles, of which 18 reporting experimental studies fulfilled the inclusion criteria. Thirteen of the studies included (72%) reported that implants coated with a collagen-CS matrix presented higher NBF, bone-to-implant contact, and/or bone volume density. The strength of this observation was supported by meta-analysis results. Nevertheless, the results should be interpreted with caution due to the lack of standardization regarding the dosage formulation of collagen-CS, short-term follow-up, and lack of assessment of confounders. On experimental grounds, the incorporation of collagen-CS matrix into implant surfaces appears to promote osseointegration. From a clinical perspective, the results from animal models support phase I studies in healthy humans.

Human adipose stem cells induced to osteogenic differentiation by an innovative collagen/hydroxylapatite hybrid scaffold

Novel biomaterials are of paramount importance for bone regrowth. In this study, we investigated human adipose stem cells (hASCs) for osteogenic, osteoconductivity, and osteoinductivity effects of an innovative collagen/hydroxylapatite hybrid scaffold. In hASCs that were grown on this scaffold, osteogenic genes were analyzed for their expression profiles, together with adhesion and extracellular matrix genes. In hASC integrins, basement membrane constituents and collagens were up-regulated, together with cell proliferation. In addition, expression of osteopontin and activated focal adhesion kinase was studied at the protein level. Our in vitro data indicate that hASCs, together with hybrid biomaterial, is an important model of study to investigate in vitro bone induction.-Mazzoni, E., D'Agostino, A., Manfrini, M., Maniero, S., Puozzo, A., Bassi, E., Marsico, S., Fortini, C., Trevisiol, L., Patergnani, S., Tognon, M. Human adipose stem cells induced to osteogenic differentiation by an innovative collagen/hydroxylapatite hybrid scaffold.

Structural modification of titanium surface by octacalcium phosphate via Pulsed Laser Deposition and chemical treatment

In the present study, the Pulsed Laser Deposition (PLD) technique was applied to coat titanium for orthopaedic and dental implant applications. Calcium carbonate (CC) was used as starting coating material. The deposited CC films were transformed into octacalcium phosphate (OCP) by chemical treatments. The results of X-ray diffraction (XRD), Raman, Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) studies revealed that the final OCP thin films are formed on the titanium surface. Human myofibroblasts from peripheral vessels and the primary bone marrow mesenchymal stromal cells (BMMSs) were cultured on the investigated materials. It was shown that all the investigated samples had no short-term toxic effects on cells. The rate of division of myofibroblast cells growing on the surface and saturated BMMSs concentration for the OCP coating were about two times faster than of cells growing on the CC films.

Biological and Mechanical Effects of Micro-Nanostructured Titanium Surface on an Osteoblastic Cell Line In vitro and Osteointegration In vivo

Hybrid micro-nanostructure implant surface was produced on titanium (Ti) surface by acid etching and anodic oxidation to improve the biological and mechanical properties. The biological properties of the micro-nanostructure were investigated by simulated body fluid (SBF) soaking test and MC3T3-E1 cell co-culture experiment. The cell proliferation, spreading, and bone sialoprotein (BSP) gene expression were examined by MTT, SEM, and reverse transcription-polymerase chain reaction (RT-PCR), respectively. In addition, the mechanical properties were evaluated by instrumented nanoindentation test and friction-wear test. Furthermore, the effect of the micro-nanostructure surface on implant osteointegration was examined by in vivo experiment. The results showed that the formation of bone-like apatite was accelerated on the micro-nanostructured Ti surface after immersion in simulated body fluid, and the proliferation, spreading, and BSP gene expression of the MC3T3-E1 cells were also upregulated on the modified surface. The micro-nanostructured Ti surface displayed decreased friction coefficient, stiffness value, and Young's modulus which were much closer to those of the cortical bone, compared to the polished Ti surface. This suggested much better mechanical match to the surrounding bone tissue of the micro-nanostructured Ti surface. Furthermore, the in vivo animal experiment showed that after implantation in the rat femora, the micro-nanostructure surface displayed higher bonding strength between bone tissues and implant; hematoxylin and eosin (H&E) staining suggested that much compact osteoid tissue was observed at the interface of Micro-nano-Ti-bone than polished Ti-bone interface after implantation. Based on these results mentioned above, it was concluded that the improved biological and mechanical properties of the micro-nanostructure endowed Ti surface with good biocompatibility and better osteointegration, implying the enlarged application of the micro-nanostructure surface Ti implants in future.

Rapamycin/sodium hyaluronate binding on nano-hydroxyapatite coated titanium surface improves MC3T3-E1 osteogenesis

Endosseous titanium (Ti) implant failure due to poor biocompatibility of implant surface remains a major problem for osseointegration. Improving the topography of Ti surface may enhance osseointegration, however, the mechanism remains unknown. To investigate the effect of modified Ti surface on osteogenesis, we loaded rapamycin (RA) onto nano-hydroxyapatite (HAp) coated Ti surface which was acid-etched, alkali-heated and HAp coated sequentially. Sodium hyaluronate (SH) was employed as an intermediate layer for the load of RA, and a steady release rate of RA was maintained. Cell vitality of MC3T3-E1 was assessed by MTT. Osteogenesis of MC3T3-E1 on this modified Ti surface was evaluated by alkaline phosphatase (ALP) activity, mineralization and related osteogenesis genes osteocalcin (OCN), osteopontin (OPN), Collagen-I and Runx2. The result revealed that RA/SH-loaded nano-HAp Ti surface was innocent for cell vitality and even more beneficial for cell osteogenesis in vitro. Furthermore, osteogenesis of MC3T3-E1 showed significant association with the mammalian target of rapamycin (mTOR) phosphorylation by RA, which required further study about the mechanism. The approach to this modified Ti surface presented in this paper has high research value for the development of Ti-based implant.

Nanoparticle-Programmed Surface for Drug Release and Cell Regulation via Reversible Hybridization Reaction

A surface directly connects the bulk of a material to its surroundings. The ability to dynamically regulate the surface without affecting the bulk of a material holds great potential for new applications. The purpose of this work was to demonstrate that the surface can be dynamically changed using nanoparticles and oligonucleotides (ODNs) in a reversible and reiterative manner. A dual-functional nanogel was synthesized as the model of nanoparticles using miniemulsion polymerization and click chemistry. The nanogel can not only adsorb drugs for sustained drug release but also bind a surface functionalized with complementary ODNs. Importantly, hybridization reaction and ODN degradation can drive reversible and reiterative nanogel binding to the surface for dynamic change, which in principle is unlimited. Moreover, nanogel-mediated dynamic change offers the surface with the drug-releasing function for inhibiting the growth of surrounding cells. Because nanogels can be replaced by any functional nanoparticles with a diverse array of properties, nanoparticle-programmed surface change constitutes a promising platform for various applications such as drug delivery and stent implantation.

Nanoparticles in β-tricalcium phosphate substrate enhance modulation of structure and composition of an octacalcium phosphate grown layer

Nanoparticles in the β-TCP substrate enhance structural modulation of an OCP grown layer.

Antibacterial and cytocompatible AgNPs constructed with the assistance of Mefp-1 for orthopaedic implants

For the first time, Mefp-1 coating has been used in surface antibacterial and biocompatible modifications based on its multifunctionality.

Does Local Ibandronate and/or Pamidronate Delivery Enhance Osseointegration? A Systematic Review

PURPOSE

To our knowledge from indexed literature, the present study is the first one to systematically review the influence of local delivery of pamidronate (PAM) and/or ibandronate (IBA) on osseointegration enhancement. The aim of the present systematic review was to assess the efficacy of IBA and/or PAM local delivery (topically or coating on implants surfaces) in promoting osseointegration.

MATERIALS AND METHODS

To address the focused question, "Does local IBA and/or PAM delivery enhances osseointegration?," indexed databases were searched without time or language restrictions up to and including May 2016 using various combinations of the following keywords: "pamidronate," "ibandronate," "bisphosphonates," "osseointegration," and "topical administration." Letters to the Editor, historic reviews, commentaries, case series, and case reports were excluded.

RESULTS

Fifteen studies were included. Fourteen studies were performed in animals and 2 were clinical trials. One study reported an experimental model and a clinical trial in the same publication. Results from 12 experimental studies and 2 clinical studies reported improved biomechanical properties and/or osseointegration around implants with PAM and/or IBA. Two experimental studies showed that PAM and/or IBA did not improve osseointegration.

CONCLUSIONS

On experimental grounds, local IBA and/or PAM delivery seems to enhance osseointegration; however, from a clinical perspective, further randomized control trials are needed to assess the effectiveness of IBA and PAM in promoting osseointegration around dental implants.

Micro-Nanostructured Polyaniline Assembled in Cellulose Matrix via Interfacial Polymerization for Applications in Nerve Regeneration

Conducting polymers have emerged as frontrunners to be alternatives for nerve regeneration, showing a possibility of the application of polyaniline (PANI) as the nerve guidance conduit. In the present work, the cellulose hydrogel was used as template to in situ synthesize PANI via the limited interfacial polymerization method, leading to one conductive side in the polymer. PANI sub-micrometer dendritic particles with mean diameter of ∼300 nm consisting of the PANI nanofibers and nanoparticles were uniformly assembled into the cellulose matrix. The hydrophobic PANI nanoparticles were immobilized in the hydrophilic cellulose via the phytic acid as "bridge" at presence of water through hydrogen bonding interaction. The PANI/cellulose composite hydrogels exhibited good mechanical properties and biocompatibility as well as excellent guiding capacity for the sciatic nerve regeneration of adult Sprague-Dawley rats without any extra treatment. On the basis of the fact that the pure cellulose hydrogel was an inert material for the neural repair, PANI played an indispensable role on the peripheral nerve regeneration. The hierarchical micro-nanostructure and electrical conductivity of PANI could remarkably induce the adhesion and guiding extension of neurons, showing its great potential in biomedical materials.

A facile construction of gradient micro-patterned OCP coatings on medical titanium for high throughput evaluation of biocompatibility

A facile construction of gradient micro-patterned octacalcium phosphate (OCP) coatings on titanium was developed for high-throughput screening of biocompatibility and bioactivity.