Improved Osteoblast Adhesion Research Articles

Plasma-Enabled Graphene Quantum Dot Hydrogel-Magnesium Composites as Bioactive Scaffolds for In Vivo Bone Defect Repair.

Bioactive and mechanically stable metal-based scaffolds are commonly used for bone defect repair. However, conventional metal-based scaffolds induce nonuniform cell growth, limiting damaged tissue restoration. Here, we develop a plasma nanotechnology-enhanced graphene quantum dot (GQD) hydrogel-magnesium (Mg) composite scaffold for functional bone defect repair by integrating a bioresource-derived nitrogen-doped GQD (NGQD) hydrogel into the Mg ZK60 alloy. Each scaffold component brings major synergistic advantages over the current alloy-based state of the art, including (1) mechanical support of the cortical bone and calcium deposition by the released Mg2+ during degradation; (2) enhanced uptake, migration, and distribution of osteoblasts by the porous hydrogel; and (3) improved osteoblast adhesion and proliferation, osteogenesis, and mineralization by the NGQDs in the hydrogel. Through an in vivo study, the hybrid scaffold with the much enhanced osteogenic ability induced by the above synergy promotes a more rapid, uniform, and directional bone growth across the hydrogel channel, compared with the control Mg-based scaffold. This work provides insights into the design of multifunctional hybrid scaffolds, which can be applied in other areas well beyond the demonstrated bone defect repair.

Magnesium (Mg2 +), Strontium (Sr2 +), and Zinc (Zn2 +) Co-substituted Bone Cements Based on Nano-hydroxyapatite/Monetite for Bone Regeneration.

New bone cement type that combines Sr2 + /Mg2 + or Sr2 + /Zn2 + co-substituted nano-hydroxyapatite (n-HAs) with calcium phosphate dibasic and chitosan/gelatin polymers was developed to increase adhesion and cellular response. The cements were physicochemically described and tested in vitro using cell cultures. All cements exhibited quite hydrophilic and had high washout resistance. Cement releases Ca2 + , Mg2 + , Sr2 + , and Zn2 + in concentrations that are suitable for osteoblast proliferation and development. All of the cements stimulated cell proliferation in fibroblasts, endothelial cells, and osteoblasts, were non-cytotoxic, and produced apatite. Cements containing co-substituted n-HAs had excellent cytocompatibility, which improved osteoblast adhesion and cell proliferation. These cements had osteoinductive potential, stimulating extracellular matrix (ECM) mineralization and differentiation of MC3T3-E1 cells by increasing ALP and NO production. The ions Ca2 + , Mg2 + , Zn2 + , and Sr2 + appear to cooperate in promoting osteoblast function. The C3 cement (HA-SrMg5%), which was made up of n-HA co-substituted with 5mol% Sr and 5mol% Mg, showed exceptional osteoinductive capacity in terms of bone regeneration, indicating that this new bone cement could be a promising material for bone replacement.

On-Growth and In-Growth Osseointegration Enhancement in PM Porous Ti-Scaffolds by Two Different Bioactivation Strategies: Alkali Thermochemical Treatment and RGD Peptide Coating.

A lack of primary stability and osteointegration in metallic implants may result in implant loosening and failure. Adding porosity to metallic implants reduces the stress shielding effect and improves implant performance, allowing the surrounding bone tissue to grow into the scaffold. However, a bioactive surface is needed to stimulate implant osteointegration and improve mechanical stability. In this study, porous titanium implants were produced via powder sintering to create different porous diameters and open interconnectivity. Two strategies were used to generate a bioactive surface on the metallic foams: (1) an inorganic alkali thermochemical treatment, (2) grafting a cell adhesive tripeptide (RGD). RGD peptides exhibit an affinity for integrins expressed by osteoblasts, and have been reported to improve osteoblast adhesion, whereas the thermochemical treatment is known to improve titanium implant osseointegration upon implantation. Bioactivated scaffolds and control samples were implanted into the tibiae of rabbits to analyze the effect of these two strategies in vivo regarding bone tissue regeneration through interconnected porosity. Histomorphometric evaluation was performed at 4 and 12 weeks after implantation. Bone-to-implant contact (BIC) and bone in-growth and on-growth were evaluated in different regions of interest (ROIs) inside and outside the implant. The results of this study show that after a long-term postoperative period, the RGD-coated samples presented higher quantification values of quantified newly formed bone tissue in the implant’s outer area. However, the total analyzed bone in-growth was observed to be slightly greater in the scaffolds treated with alkali thermochemical treatment. These results suggest that both strategies contribute to enhancing porous metallic implant stability and osteointegration, and a combination of both strategies might be worth pursuing.

Mussel-Inspired Gold Nanoparticle and PLGA/L-Lysine-g-Graphene Oxide Composite Scaffolds for Bone Defect Repair.

PurposeInsufficient biological activity heavily restricts the application and development of biodegradable bone implants. Functional modification of bone implants is critical to improve osseointegration and bone regeneration.MethodsIn this study, L-lysine functionalized graphene oxide (Lys-g-GO) nanoparticles and polydopamine-assisted gold nanoparticle (AuNPs-PDA) coatings were applied to improve the biological function of PLGA scaffold materials. The effects of Lys-g-GO nanoparticles and AuNPs-PDA functionalized coatings on the physicochemical properties of PLGA scaffolds were detected with scanning electron microscopy (SEM), contact angle measurement, and mechanical testing instruments. In vitro, the effects of composite scaffolds on MC3T3-E1 cell proliferation, adhesion, and osteogenic differentiation were studied. Finally, a radial defect model was used to assess the effect of composite scaffolds on bone defect healing.ResultsThe prepared AuNPs-PDA@PLGA/Lys-g-GO composite scaffolds exhibited excellent mechanical strength, hydrophilicity and antibacterial properties. In vitro, this composite scaffold can significantly improve osteoblast adhesion, proliferation, osteogenic differentiation, calcium deposition, and other cell behaviour. In vivo, this composite scaffold can significantly promote the new bone formation and collagen deposition in the radial defect site and presented good biocompatibility.ConclusionThe combination of bioactive nanoparticles and surface coatings shows considerable potential to enhance the osseointegration of bone implants.

Fabrication and characterization of superficially modified porous dental implants

Abstract Stress-shielding and loosening compromise the success of dental implants under real-life service conditions. This work evaluates the mechanical behavior of superficially modified porous titanium dental implants fabricated by two different routes: conventional powder-metallurgy and space-holder techniques. A novel, feasible and repetitive protocol of micro-milling of the implant thread (before sintering), as well as surface modification treatments (after sintering) are also implemented. The discussion is conducted in terms of the influence of porosity and surface roughness on the stiffness and yield strength of implants. The macro-pores concentrate stress locally, and, at the same time, they could act as a barrier to the propagation of micro-cracks. Higher rugosity was observed for virgin implants obtained with spacer particles. Concerning superficially modified implants, while bioglass 1393 was the most effective coating due to its greater infiltration and adhesion capacity, chemical etching could improve osteoblast adhesion because modifies the roughness of the implant surface.

Development of functionally graded porous titanium/silk fibroin composite scaffold for bone repair

A composite scaffold comprising a silk fibroin (SF) sponge on functionally graded titanium (FG-Ti) was developed. The FG-Ti showed a radial graded structure similar to native long bone and better mechanical properties than those of homogeneous porous Ti with the same porosity. The microstructure of the composite scaffold was observed using scanning electron microscopy. The SF sponge filled in FG-Ti exhibited interconnected pore architecture, which could provide a suitable environment for cell attachment. The in vitro biocompatibility of the composite scaffolds was investigated using rat osteoblastic cells. Compared to FG-Ti, composite scaffolds exhibited an improved osteoblast adhesion and proliferation. These results suggest that the composite scaffold is a good candidate as a bone repair scaffold.

Nanolamellar Tantalum Interfaces in the Osteoblast Adhesion.

The design of topographically patterned surfaces is considered to be a preferable approach for influencing cellular behavior in a controllable manner, in particular to improve the osteogenic ability of bone regeneration. In this study, we fabricated nanolamellar tantalum (Ta) surfaces with lamellar wall thicknesses of 40 and 70 nm. The cells attached to nanolamellar Ta surfaces exhibited higher protein adsorption and expression of β1 integrin, as compared to the nonstructured bulk Ta, which facilitated the initial cell attachment and spreading. We thus, as expected, observed significantly enhanced osteoblast adhesion, growth, and alkaline phosphatase activity on nanolamellar Ta surfaces. However, the beneficial effects of nanolamellar structures on osteogenesis became weaker as the lamellar wall thickness increased. The interaction between cells and Ta surfaces was examined through adhesion forces using atomic force microscopy. Our findings indicated that the Ta surface with a lamellar wall thickness of 40 nm exhibited the strongest stimulatory effect. The observed strongest adhesion force between the cell-attached tip and the Ta surface with a 40 nm thick lamellar wall encouraged the much stronger binding of cells with the surface and thus well-attached, -stretched, and -grown cells. We attributed this to the increase in the available contact area of cells with the thinner nanolamellar Ta surface. The increased contact area allowed the enhancement of the cell surface interaction strength and, thus, improved osteoblast adhesion. This study suggests that the thin nanolamellar topography shows immense potential in improving the clinical performance of dental and orthopedic implants.

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.

PLGA film/Titanium nanotubues as a sustained growth factor releasing system for dental implants.

Ti-based implants sometimes fail to integrate with surrounding bone tissue due to insufficiency of new bone formation and surface bonding. To overcome this problem, this research focused on establishing a sustained bone growth factor delivery system by applying anodized TiO2 nanotube arrays and PLGA film on the titanium implant surface. TiO2 nanotube arrays were made by anodic oxidation method, and were then filled with rhBMP2 by vacuum freeze-drying. Next, PLGA was deposition on the surface of this material. The designed system was characterized, pharmacokinetic release rate of rhBMP2 was determined. Adhesion, proliferation, and differentiation activity of osteoblasts cultured on the new surfaces and traditional titanium surfaced were compared. SEM showed that a surface of TiO2 nanotube arrays were successfully generated. PLGA membranes of 50 nm, 250 nm, 800 nm thickness were successfully deposited on the surfaces of TiO2 nanotube layers by using 1%, 3%, 10% PLGA solutions. PLGA film of 250 nm thickness showed ideally controlled release of rhBMP2, lasting for 4 weeks. Furthermore, 250 nm thickness PLGA film improved osteoblast adhesion, proliferation, and levels of alkaline phosphatase. In conclusion, the PLGA film / TiO2 nanotube growth factor delivery system can effectively sustain the release of rhBMP-2, and promote proliferation and differentiation of MC3T3-E1 osteoblasts.

Ophiopogonin D improves osteointegration of titanium alloy implants under diabetic conditions by inhibition of ROS overproduction via Wnt/β-catenin signaling pathway

A high failure rate of titanium implants in diabetic patients has been indicated in clinical evidences. Excessive oxidative stress at the bone-implant interface plays an important role in the impaired osteointegration under diabetic conditions. While the underlying mechanisms remain unknown and the targeted treatments are urgently needed. Ophiopogonin D (OP-D), isolated from Chinese herbal Radix Ophiopogon japonicus, is generally reported to be a potent antioxidant agent. In the present study, we hypothesized that OP-D exerted promotive effects on osteointegration against oxidative stress, and investigated the underlying mechanisms associated with alteration of Wnt/β-catenin signaling pathway. Rabbit osteoblasts incubated on titanium alloy implant were co-cultured with normal serum (NS), diabetic serum (DS), DS + OP-D, DS + NAC (a potent ROS inhibitor) and DS + OP-D + Dkk1 (a Wnt inhibitor) for examinations of osteoblast behaviors. For in vivo study, titanium alloy implants were implanted into the femoral condyle defects on diabetic rabbits. Results demonstrated that diabetes-induced oxidative stress resulted in osteoblast dysfunctions and apoptotic injury at the bone-implant interface, concomitant with the inactivation of Wnt/β-catenin signaling. Importantly, OP-D administration attenuated oxidative stress, directly reactivating Wnt/β-catenin signaling. Osteoblast dysfunctions were thus reversed as evidenced by improved osteoblast adhesion, proliferation and differentiation, and ameliorated apoptotic injury, exerting similar effects to NAC treatment. In addition, the positive effects afforded by OP-D were confirmed by improved osteointegration and oetogenesis within the titanium alloy implants in vivo by Micro-CT and histological analyses. Furthermore, the pro-osteogenic effects of OP-D were almost completely abolished by the Wnt inhibitor Dkk1. These results demonstrated, for the first time, OP-D administration alleviated the damaged osteointegration of titanium alloy implants under diabetic conditions by means of inhibiting oxidative stress via a Wnt/β-catenin-dependent mechanism. The OP-D administration would become a reliable treatment strategy for implant failure therapy in diabetics due to the optimal anti-oxidative and pro-osteogenic properties.

Multifuctional Nanofilm for Stimulating Bone Cell Attachment, Proliferation and Preventing Bacterial Colonization

Osseointegration and infection prevention are of great importance for the long-term success of bone-in-contact implants. In this study, we developed multi-drug loaded polypeptide nanofilms on orthopedic implant models for potential enhanced osseointegration and improved infection prevention. RGD, a cell-adhesive ligand, transforming growth factor beta 1 (TGF-β1), a growth factor, and gentamicin, a common antibiotic, were successfully incorporated into one single polypeptide nanofilm. On one hand, the incorporation of Arg-Gly-Asp (RGD) within polypeptide nanofilms significantly improved osteoblast cell adhesion, proliferation, and viability. The incorporation of TGF-β1 led to enhanced osteoblast cell proliferation at day 5 and improved cell viability as well. However, polypeptide nanofilms with RGD or a combination of RGD and TGF also promoted bacterial growth after 2 days. On the other hand, the incorporation of gentamicin resulted in anticipated antimicrobial properties against Staphylococcus aureus (S. aureus). However, the incorporation of gentamicin alone had reduced cell adhesion and proliferation. By combining RGD and TGF with gentamicin within a single nanofilm, an ideal surface with overall improved osteoblast adhesion, proliferation, viability, and antibacterial properties was able to be achieved. The developed multi-drug loaded polypeptide nanofilms may provide a promising means for not only enhancing tissue integration but also simultaneously reducing bacterial infection.

Investigating the effect of picosecond laser texturing on microstructure and biofunctionalization of titanium alloy

Laser processing technique has been an effective method to enhance the medical implant’s biocompatibility through forming specific textures on titanium alloy implant surface. In this paper, a 1064nm pulsed picosecond laser on TC4 titanium alloy implant samples was conducted to obtain optimal parameters for well-structured textures, controllable micro-grooves and improved osteoblast adhesion and proliferation. Picosecond laser technique is generally characterized by the high flexibility and advanced properties, which could make structural features including topography quality and detailed dimensions expediently improved and changed by adjusting laser processing parameters. To obtain the optimal laser processing parameters for desired microstructures, orthogonal experiments and related SEM, EDS and SPM analysis were conducted under various laser powers, repetition frequencies, scan speeds and scan numbers. Thus, the correlation between picosecond laser processing parameters and its corresponding microstructure feature of the micro-grooves was established. In addition, the immunofluorescence detection of cell actin cytoskeleton shows that structured textures can promote cell adhesion and play an important role in cell contact guidance.

Biological responses to M13 bacteriophage modified titanium surfaces in vitro.

In vivo, the bone and immune cells share a common microenvironment, and are being affected by similar cytokines, signaling molecules, transcription factors and membrane receptors. Ideal implants should cause positive biological response, including adequate and appropriate inflammatory reaction, well-balanced bone formation and absorption. Phage-based materials have showed great potential in tissue engineering application. However, at present it is unknown what inflammation response will happen to this kind of materials. A good understanding of the immune response possibly induced by phage-based materials is needed. This work studied the osteoimmunomodulation property of phage films on titanium surface, involving inflammatory response, osteogenic activity and biomineralization ability. It provides more understanding of the phage-based materials and contributes to their future application in tissue engineering.

Promotion of osteointegration under diabetic conditions by tantalum coating-based surface modification on 3-dimensional printed porous titanium implants

Clinical evidence indicates a high failure rate for titanium implants (TiI) in diabetic patients, involving the overproduction of reactive oxygen species (ROS) at the implant/bone interface. Tantalum coating on titanium (TaTi) has exerted better tissue integration properties than TiI, but its biological performance under diabetic conditions remains elusive. To investigate whether TaTi may ameliorate diabetes-induced implant destabilization and the underlying mechanisms, primary rabbit osteoblasts cultured on 3-dimensional printed TiI and TaTi were exposed to normal serum (NS), diabetic serum (DS), DS+NAC (a potent ROS inhibitor), and DS+SB203580 (a specific p38 MAPK inhibitor). An in vivo study was performed on diabetic sheep implanted with TiI or TaTi. Diabetes induced mitochondrial-derived ROS overproduction and caused cellular dysfunction and apoptosis, together with the activation of p38 MAPK in osteoblasts on TiI surface. Importantly, TaTi significantly attenuated ROS production and p38 MAPK phosphorylation and exerted more osseointegrative cell behavior than TiI, as shown by improved osteoblast adhesion, increased cell proliferation and differentiation and decreased apoptosis. These results were confirmed in vivo by the enhanced bone healing efficacy of TaTi. Moreover, treatment with NAC or SB203580 on TiI not only inhibited the activation of p38 MAPK but also improved cell function and alleviated apoptotic injury, whereas TaTi combined with NAC or SB203580 failed to further improve osteoblast functional recovery compared with TaTi alone. These results demonstrated that the tantalum coating markedly improved diabetes-induced impaired osteogenesis of TiI, which may be attributed to the suppression of the ROS-mediated p38 MAPK pathway.

Chitosan scaffold modified with D-(+) raffinose and enriched with thiol-modified gelatin for improved osteoblast adhesion

The aim of the present study was to investigate whether chitosan-based scaffolds modified with D-(+) raffinose and enriched with thiol-modified gelatin could selectively improve osteoblast adhesion and proliferation.2, 3 and 4.5% chitosan films were prepared. Chitosan suitability for tissue engineering was confirmed by protein adsorption assay. Scaffolds were incubated with a 2.5 mg ml−1 BSA solution and the decrease of protein content in the supernatants was measured by spectrophotometry.Chitosan films were then enriched with thiol-modified gelatin and their ability to bind BSA was also measured.Then, 2% chitosan discs with or without thiol-modified gelatin were used as culture substrates for MC3T3-E1 cells. After 72 h cells were stained with trypan blue or with calcein AM and propidium iodide for morphology, viability and proliferation assays. Moreover, cell viability was measured at 48, 72, 96 and 168 h to obtain a growth curve.Chitosan films efficiently bound and retained BSA proportionally to the concentration of chitosan discs. The amount of protein retained was higher on chitosan enriched with thiol-modified gelatin.Moreover, chitosan discs allowed the adhesion and the viability of cells, but inhibited their proliferation. The functionalization of chitosan with thiol-modified gelatin enhanced cell spreading and proliferation.Our data confirm that chitosan is a suitable material for tissue engineering. Moreover, our data show that the enrichment of chitosan with thiol-modified gelatin enhances its biological properties.

A novel composite scaffold consisted of porous titanium and chitosan sponge for load-bearing applications: Fabrication, characterization and cellular activity

Abstract A novel composite scaffold consisting of porous Ti part filled with chitosan/HA sponge was fabricated using a combination of electron beam melting and freeze-drying. The mechanical properties of porous Ti with porosities of ∼60–75% were examined via compressive test. The compression strength values of the samples were ranged from 86.35 (±12.68) – 180.21 (±10.26) MPa and stiffness values were of 2.23 (±0.68) – 5.48 (±0.54) GPa. The microstructure of composite scaffold was characterized using scanning electron microscopy. The chitosan/HA sponge filled in Ti part exhibited highly porous and well-interconnected pore architecture, which is produced to accommodate cells without the need to meet mechanical requirements. The in vitro biocompatibility of the composite scaffolds was investigated using rat osteoblasts. Compared with pure Ti part, composite scaffolds exhibited higher biological activity, such as an improved osteoblast adhesion and morphology, increased proliferation and alkaline phosphatase (ALP) activity. These results suggest that the composite scaffold is potentially useful as a biomedical scaffold for bone repair in load-bearing sites.

Advanced biopolymer-coated drug-releasing titania nanotubes (TNTs) implants with simultaneously enhanced osteoblast adhesion and antibacterial properties

Here, we report on the development of advanced biopolymer-coated drug-releasing implants based on titanium (Ti) featuring titania nanotubes (TNTs) on its surface. These TNT arrays were fabricated on the Ti surface by electrochemical anodization, followed by the loading and release of a model antibiotic drug, gentamicin. The osteoblastic adhesion and antibacterial properties of these TNT–Ti samples are significantly improved by loading antibacterial payloads inside the nanotubes and modifying their surface with two biopolymer coatings (PLGA and chitosan). The improved osteoblast adhesion and antibacterial properties of these drug-releasing TNT–Ti samples are confirmed by the adhesion and proliferation studies of osteoblasts and model Gram-positive bacteria (Staphylococcus epidermidis). The adhesion of these cells on TNT–Ti samples is monitored by fluorescence and scanning electron microscopies. Results reveal the ability of these biopolymer-coated drug-releasing TNT–Ti substrates to promote osteoblast adhesion and proliferation, while effectively preventing bacterial colonization by impeding their proliferation and biofilm formation. The proposed approach could overcome inherent problems associated with bacterial infections on Ti-based implants, simultaneously enabling the development of orthopedic implants with enhanced and synergistic antibacterial functionalities and bone cell promotion.

Improved Osteoblast and Chondrocyte Adhesion and Viability by Surface-Modified Ti6Al4V Alloy with Anodized TiO₂ Nanotubes Using a Super-Oxidative Solution.

Titanium (Ti) and its alloys are amongst the most commonly-used biomaterials in orthopedic and dental applications. The Ti-aluminum-vanadium alloy (Ti6Al4V) is widely used as a biomaterial for these applications by virtue of its favorable properties, such as high tensile strength, good biocompatibility and excellent corrosion resistance. TiO2 nanotube (NTs) layers formed by anodization on Ti6Al4V alloy have been shown to improve osteoblast adhesion and function when compared to non-anodized material. In his study, NTs were grown on a Ti6Al4V alloy by anodic oxidation for 5 min using a super-oxidative aqueous solution, and their in vitro biocompatibility was investigated in pig periosteal osteoblasts and cartilage chondrocytes. Scanning electron microscopy (SEM), energy dispersion X-ray analysis (EDX) and atomic force microscopy (AFM) were used to characterize the materials. Cell morphology was analyzed by SEM and AFM. Cell viability was examined by fluorescence microscopy. Cell adhesion was evaluated by nuclei staining and cell number quantification by fluorescence microscopy. The average diameter of the NTs was 80 nm. The results demonstrate improved cell adhesion and viability at Day 1 and Day 3 of cell growth on the nanostructured material as compared to the non-anodized alloy. In conclusion, this study evidences the suitability of NTs grown on Ti6Al4V alloy using a super-oxidative water and a short anodization process to enhance the adhesion and viability of osteoblasts and chondrocytes. The results warrant further investigation for its use as medical implant materials.

Osseointegration of chitosan coated porous titanium alloy implant by reactive oxygen species-mediated activation of the PI3K/AKT pathway under diabetic conditions

Chitosan coated porous titanium alloy implant (CTI) is demonstrated a promising approach to improve osseointegration capacity of pure porous titanium alloy implant (TI). Since chitosan has been demonstrated to exhibit antioxidant activity, we propose CTI may ameliorate the ROS overproduction, thus reverse the poor osseointegration under diabetic conditions, and investigate the underlying mechanisms. Primary rat osteoblasts incubated on the TI and the CTI were subjected to normal serum (NS), diabetic serum (DS), DS + NAC (a potent ROS inhibitor) and DS + LY294002 (a PI3K/AKT-specific inhibitor). In vivo study was performed on diabetic sheep implanted with TI or CTI into the bone defects on crista iliaca. Results showed that diabetes-induced ROS overproduction led to osteoblast dysfunction and apoptosis, concomitant with the inhibition of AKT in osteoblasts on the TI substrate. While CTI stimulated AKT phosphorylation through ROS attenuation, thus reversed osteoblast dysfunction evidenced by improved osteoblast adhesion, increased proliferation and ALP activity, and decreased cytotoxicity and apoptotic rate, which exerted same effect to NAC treatment on the TI. These effects were further confirmed by the improved osseointegration within the CTI in vivo evidenced by Micro-CT and histological examinations. In addition, the aforementioned promotive effects afforded by CTI were abolished by blocking PI3K/AKT pathway with addition of LY294002. These results demonstrate that the chitosan coating markedly ameliorates diabetes-induced impaired bio-performance of TI via ROS-mediated reactivation of PI3K/AKT pathway, which elicits a new surface functionalization strategy for better clinical performance of titanium implant in diabetic patients.

Tuning cell adhesion on titanium with osteogenic rosette nanotubes

Self-assembled rosette nanotubes (RNTs), obtained from a twin G∧C base functionalized with lysine-arginine-serine-arginine [KRSR-(G∧C)(2)], were designed and investigated as bioactive coatings on titanium. These results were compared to RNTs derived from Lysine-G∧C (K-G∧C), Arg-Gly-Asp-G∧C (RGD-G∧C), and aminobutane-(G∧C)(2) [AB-(G∧C)(2)]. The results from this study revealed that these materials had excellent cytocompatibility properties as they enhanced osteoblast (bone forming cell) adhesion when coated on titanium. In particular, KRSR and RGD functionalized RNTs coated on titanium promoted the greatest osteoblast densities relative to untreated titanium. Furthermore, KRSR functionalized RNTs selectively improved osteoblast adhesion relative to fibroblast (soft-tissue forming cell) and endothelial (cells that line the vascular) cell adhesion. In contrast with these results, RNTs obtained from an unfunctionalized twin base [AB-(G∧C)(2)], RGD-G∧C co-assembled with K-G∧C and K-G∧C significantly enhanced endothelial cell attachment, which may find applications in the vascularization of newly formed bone tissue. In summary, these studies suggest that the surface of orthopedic implant materials (such as titanium) could be tailored to promote selective cell adhesion using biologically-inspired nanotubular structures functionalized with osteogenic compounds.