Titanium surface hydrophilicity enhances platelet activation

Surface topography modulates initial platelet adhesion to titanium substrata

The clinical success of implanted biomaterials such as dental implants is largely determined by the molecular signaling that occurs at the tissue-implant interface. The modification of surface topography is a widely-employed strategy for optimizing tissue integration with dental implants. However, little is known regarding the direct, cellular-level effects of substratum topography on platelet signaling and adhesion, despite these cells being the first to encounter the implant surface during surgical placement. Here we compared platelet adhesion and secretion on four (4) different titanium surfaces, notably, the modifications applied to commercially available dental implants: smooth (S) titanium; acid-etched (AE), sandblasted (SB) and a combined acid-etching/sandblasting procedure (SLA). Platelets were isolated from human blood, washed, and seeded on to the 4 test surfaces; platelet adhesion was quantified by microscopy. In addition, the secretion of critical molecules stored in platelet granules (platelet factor 4, PF4; soluble P-selectin, sCD62P; transforming growth factor-beta1, TGF-β1; platelet-derived growth factor-AB, PDGF-AB) was measured by enzyme-linked immunosorbent assay (ELISA) analysis of the supernatants. There was greater platelet adhesion to the rougher AE and SB surfaces, however, the concentration of the secreted growth factors was comparable on all surfaces. We conclude that while surface topography can be engineered to modulate initial platelet adhesion, granule secretion is likely regulated as a separate and independent process.

The role of dendritic cells in the immunomodulation to implanted biomaterials

Considering the substantial role played by dendritic cells (DCs) in the immune system to bridge innate and adaptive immunity, studies on DC-mediated immunity toward biomaterials principally center on their adjuvant effects in facilitating the adaptive immunity of codelivered antigens. However, the effect of the intrinsic properties of biomaterials on dendritic cells has not been clarified. Recently, researchers have begun to investigate and found that biomaterials that are nonadjuvant could also regulate the immune function of DCs and thus affect subsequent tissue regeneration. In the case of proteins adsorbed onto biomaterial surfaces, their intrinsic properties can direct their orientation and conformation, forming “biomaterial-associated molecular patterns (BAMPs)”. Thus, in this review, we focused on the intrinsic physiochemical properties of biomaterials in the absence of antigens that affect DC immune function and summarized the underlying signaling pathways. Moreover, we preliminarily clarified the specific composition of BAMPs and the interplay between some key molecules and DCs, such as heat shock proteins (HSPs) and high mobility group box 1 (HMGB1). This review provides a new direction for future biomaterial design, through which modulation of host immune responses is applicable to tissue engineering and immunotherapy.

Canonical Wnt signaling enhances pro-inflammatory response to titanium by macrophages

Biomaterial characteristics like surface roughness and wettability can determine the phenotype of macrophages following implantation. We have demonstrated that inhibiting Wnt ligand secretion abolishes macrophage polarization in vitro and in vivo; however, the role of canonical Wnt signaling in macrophage activation in response to physical and chemical biomaterial cues is unknown. The aim of this study was to understand whether canonical Wnt signaling affects the response of macrophages to titanium (Ti) surface roughness or wettability in vitro and in vivo. Activating canonical Wnt signaling increased expression of toll-like receptors and interleukin receptors and secreted pro-inflammatory cytokines and reduced anti-inflammatory cytokines on Ti, regardless of surface properties. Inhibiting canonical Wnt signaling reduced pro-inflammatory cytokines on all Ti surfaces and increased anti-inflammatory cytokines on rough or rough-hydrophilic Ti. In vivo, activating canonical Wnt signaling increased total macrophages, pro-inflammatory macrophages, and T cells and decreased anti-inflammatory macrophages on both smooth and rough-hydrophilic implants. Functionally, canonical Wnt activation increases pro-inflammatory macrophage response to cell and cell-extracellular matrix lysates. These results demonstrate that activating canonical Wnt signaling primes macrophages to a pro-inflammatory phenotype that affects their response to Ti implants in vitro and in vivo.

Osseointegration of a New, Ultrahydrophilic and Nanostructured Dental Implant Surface: A Comparative In Vivo Study

This study compared the osseointegration of acid-etched, ultrahydrophilic, micro- and nanostructured implant surfaces (ANU) with non-ultra-hydrophilic, microstructured (SA) and non-ultrahydrophilic, micro- and nanostructured implant surfaces (AN) in vivo. Fifty-four implants (n = 18 per group) were bilaterally inserted into the proximal tibia of New Zealand rabbits (n = 27). After 1, 2, and 4 weeks, bone-implant contact (BIC, %) in the cortical (cBIC) and spongious bone (sBIC), bone chamber ingrowth (BChI, %), and the supra-crestal, subperiosteal amount of newly formed bone, called percentage of linear bone fill (PLF, %), were analyzed. After one week, cBIC was significantly higher for AN and ANU when compared to SA (p = 0.01 and p = 0.005). PLF was significantly increased for ANU when compared to AN and SA (p = 0.022 and p = 0.025). After 2 weeks, cBIC was significantly higher in SA when compared to AN (p = 0.039) and after 4 weeks, no significant differences in any of the measured parameters were found anymore. Ultrahydrophilic implants initially improved osseointegration when compared to their non-ultrahydrophilic counterparts. In accordance, ultrahydrophilic implants might be appropriate in cases with a necessity for an accelerated and improved osseointegration, such as in critical size alveolar defects or an affected bone turnover.

Greater Osseointegration Potential with Nanostructured Surfaces on TiZr: Accelerated vs. Real-Time Ageing

Surface chemistry and nanotopography of dental implants can have a substantial impact on osseointegration. The aim of this investigation was to evaluate the effects of surface chemistry and nanotopography on the osseointegration of titanium-zirconium (TiZr; Roxolid^®) discs, using a biomechanical pull-out model in rabbits. Two discs each were placed in both the right and left tibiae of 16 rabbits. Five groups of sandblasted acid etched (SLA) discs were tested: (1) hydrophobic without nanostructures (dry/micro) (n = 13); (2) hydrophobic with nanostructures, accelerated aged (dry/nano/AA) (n = 12); (3) hydrophilic without nanostructures (wet/micro) (n = 13); (4) hydrophilic with nanostructures, accelerated aged (wet/nano/AA; SLActive^®) (n = 13); (5) hydrophilic with nanostructures, real-time aged (wet/nano/RTA). The animals were sacrificed after four weeks and the biomechanical pull-out force required to remove the discs was evaluated. Adjusted mean pull-out force was greatest for group wet/nano/RTA (64.5 ± 17.7 N) and lowest for group dry/micro (33.8 ± 10.7 N). Multivariate mixed model analysis showed that the pull-out force was significantly greater for all other disc types compared to the dry/micro group. Surface chemistry and topography both had a significant effect on pull-out force (p < 0.0001 for both), but the effect of the interaction between chemistry and topography was not significant (p = 0.1056). The introduction of nanostructures on the TiZr surface significantly increases osseointegration. The introduction of hydrophilicity to the TiZr implant surface significantly increases the capacity for osseointegration, irrespective of the presence or absence of nanotopography.

Biological responses of human bone mesenchymal stem cells to Ti and TiZr implant materials

BACKGROUND

Titanium-zirconium alloy (TiZr1317) is a new material used for biological implants. There are several studies on the effects of TiZr implants on the biological characteristics of human bone mesenchymal stem cells (hBMSCs).

PURPOSE

The purpose of this study was to investigate the biological responses of hBMSCs to implant holes affected by the physicochemical properties of oral implants (Ti_SLA , Ti_SLActive , TiZr_SLA , and TiZr_SLActive ).

MATERIALS AND METHODS

Grade 4 Ti and TiZr (13-17% Zr) substrates were modified by sand-blasted large-grit acid-etched (SLA) or hydrophilic sand-blasted large-grit acid-etched (SLActive), resulting in four types of surface with complex microstructures corresponding to the commercially-available implants SLA, RoxolidSLA, SLActive, and RoxolidSLActive (Institute Straumann AG, Basel, Switzerland). Physicochemical properties were detected and the biological responses of hBMSCs were observed.

RESULTS

Surface morphology characterization by scanning electron microscopy and atomic force microscopy revealed differences between the four groups. SLA_ctive had higher surface energy/wettability than SLA, indicating that increased surface energy/wettability can promote the absorption of osteogenic proteins and enhance osseointegration. hBMSCs seeded on SLActive substrates exhibited better performance in terms of cell attachment, proliferation and osteoblastic differentiation than cells seeded on SLA.

CONCLUSION

Because of their more suitable physicochemical properties, Ti_SLActive and TiZr_SLActive materials demonstrated more pronounced effects on the biological responses of hBMSCs compared with Ti_SLA and TiZr_SLA .

A Clinical and Radiographic Evaluation of Resonance Frequency Analysis of Sand Blasted Acid Etched (SAE) and Chemical Modified Sae Dental Implants

Aims and Objective:

Chemically modified and sandblasted acid-etched (SAE) mechanism leads to wettability of surfaces of dental implants which helps in osseointegration. The present study was conducted to determine the implant stability quotient (ISQ) of SAE and SAE chemically modified dental implants.

Materials and Methods:

The present study was conducted on 210 patients with 120 males and 90 females. Dental implants (Adin) with SAE (Group A) and SAE chemically modified (Group B) were inserted in patients. RFA was done immediately after implant insertion and after 1 week, 2 weeks, 6 weeks, 10 weeks, and 14 weeks. Results were statistically evaluated using SPSS Statistics for Windows, Version 21.0, IBM Corp., Armonk, NY, USA.

Results:

Maximum patients were in the age group of 25–35 years (males – 65, females – 48), followed by 35–45 years (males – 40, females – 32) and 45–55 years (males – 15, females – 10). Maximum dental implants were given in the right side (88) in males than females (56). On the left side, maximum implants were given in females (62) than males (56). Maximum RFA value of 86.2 and minimum value of 44.6 were observed in SAE dental implants (A). The maximum mean RFA value in chemically modified implants SAE (B) was 89.4 and minimum was 32.5.

Conclusion:

It was observed that surface treatment of dental implants shows higher implant–bone osseointegration. There is fastest osseointegration in implants with hydrophilic surfaces than those with SAE surfaces. ISQ was higher than 75 in both groups, which indicate higher implant stability.

Effects of Surface Nanotopography and Calcium Chemistry of Titanium Bone Implants on Early Blood Platelet and Macrophage Cell Function

Early responses of blood platelets and immunoinflammatory cells (macrophages) to titanium (Ti) bone implants affect the subsequent biological healing of implants by modulating early tissue healing-microenvironments via the formation of temporary fibrin matrix scaffolds for stem cell migration and production of growth factors and cytokines. This study investigated the effects of nanoscale surface topography and calcium ion (Ca²⁺) modification of Ti surfaces on biocompatibility regulated by blood platelets and macrophages, for the future surface design of Ti bone implants with enhanced early osteogenic capacity. A nanostructured Ti surface with or without Ca²⁺ enrichment was prepared using the hydrothermal treatment. Immediate and early functions of platelets and macrophages modulated by modified Ti surfaces were investigated by morphological observation of platelet spreading and fibrin matrix formation, platelet growth factor release, immunostaining of macrophage phenotypes, and macrophage inflammatory cytokine production. The results showed that surface nanoscale topographical modification of Ti promotes blood platelet activation and suppresses the inflammatory response of macrophages. In addition, surface chemistry modifications with Ca²⁺ enhanced the platelet response-modulating function of the nanostructured Ti surface, which accelerated immediate fibrin matrix formation and platelet-derived growth factor-AB release. Thus, nanotopographical and Ca²⁺ modifications of implant surfaces are expected to be effective approaches that favor the initial phase of wound healing around the Ti bone implants through positive modulation of immediate blood platelet function and early macrophage immunoinflammatory response.

A facile novel fluorocarbon copolymer solution coating process for improving platelet compatibility of titanium

Titanium (Ti) and its alloys possess mechanical properties that are desirable in many biomedical applications compared to other metals. Furthermore, the native metal oxide layer that prevents further oxidation is also known to be biocompatible. However, clinical findings have shown that titanium and its alloys are prone to adverse bioreactions such as platelet adhesion and activation which could lead to thrombogenic complications. It has been found that surfaces modified with fluorocarbons could reduce the degree of both platelet adhesion and activation. Nevertheless, direct fluorocarbon deposition onto titanium substrates would require significant technical efforts. Instead, this research utilized a facile coating process with novel copolymers containing 2,2,2-trifluoroethyl methacrylate (TFEMA) and vinylphosphonic acid (VPA) to modify the titanium surface, giving the surface lower surface energy and higher hydrophobicity, significantly reducing the thrombus formation while exhibiting good cytocompatibility. The anchorage group, phosphonic acid provided by VPA, can be covalently bound to the oxide surface of titanium metal. Via free radical polymerization, VPA and TFEMA formed copolymers with different hydrophobicity were then used to modify titanium substrates, on which a series of surface characterization, in vitro platelet adhesion tests, and cytotoxicity assays were performed. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) confirmed the synthesis of the copolymers and the modification of Ti substrates. The platelet adhesion tests showed significantly reduced amount of adherent platelets on certain copolymer-modified Ti substrates with low degrees of activation. The in vitro cytotoxicity assays further highlighted that the modifications conducted on Ti does not induce cytotoxicity.

Effect of crystalline phase changes in titania (TiO2) nanotube coatings on platelet adhesion and activation

OBJECTIVE

To explore the relationship between various crystalline phases of titania (TiO₂) nanotube (TNT) coatings and platelet adhesion and activation.

METHODS

TNT coatings were fabricated on pure titanium foils by anodization and then randomly divided into four groups. Three groups were annealed at 350°C, 450°C and 550°C in order to obtain different crystalline phases. The remaining group was not annealed and served as the control group. X-ray diffraction (XRD) was used to define the crystalline phases of different groups. Surface morphology, elemental composition, surface roughness, and contact angles were measured by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), laser scanning confocal microscopy (LSCM) and contact angle analysis, respectively. Platelets were cultured on the TNT coatings for 30min and 60min to assess the number, viability, distribution, and morphology of the adhered platelets. CD62P fluorescence expression and the amount of released platelet-derived growth factor (PDGF) were detected to evaluate platelet activation.

RESULTS

The un-annealed TNT coatings were amorphous and part of TNT converted to anatase after the 350°C annealing treatment. The quantity of anatase increased upon annealing at 450°C and transformed to rutile at 550°C. Nanotubes of all four groups maintained a well-ordered structure, but the wall thickness of the nanotubes increased from (11.874±1.660) nm for the un-annealed TNTs to (26.126±2.130) nm for the 550°C annealed TNTs. The surface roughness of the 550°C annealed TNT coatings was the lowest and the water contact angle was the largest at (28.117±1.182) °. The number and viability of adhered platelets after 30min and 60min were the highest on TNT coatings annealed at 450°C. LSCM and SEM images revealed that the platelets that adhered on the 450°C annealed TNT coatings aggregated, transformed, and spread most obviously. CD62P fluorescence expression results showed that the platelets on the 350°C and 450°C annealed TNT coating groups expressed the strongest fluorescence, followed by platelets on the 550°C annealed group and the un-annealed group. The quantity of released PDGF was highest for the 450°C annealed group at (4719±86) pg/mL, and lowest for the un-annealed group at (4241±74) pg/mL.

CONCLUSION

Crystalline TNT coatings encourage improved platelet adhesion and activation over amprphous analogues. The TNT coatings annealed at 450°C resulted in the most improved platelet behavior. The TNT crystalline phase was the predominant influencing factor in platelet adhesion and activation.

Improvement of Cr-Co-Mo Membrane Surface Used as Barrier for Bone Regeneration through UV Photofunctionalization: An In Vitro Study

Although there are several studies of the ultraviolet (UV) light-mediated photofunctionalization of titanium for use as implant material, the underlying mechanism is not fully understood. However, the results of in vitro and in vivo studies are very encouraging. The use of UV photofunctionalization as a surface treatment on other implant materials, as the Cr-Co-Mo alloy, has not been explored in depth. Using sandblasted Cr-Co-Mo discs, the surface photofunctionalization was studied for ultraviolet A (UVA, 365 nm) and ultraviolet C (UVC, 254 nm), and the surfaces were evaluated for their ability to sustain hydroxyapatite crystal growth through incubation in simulated body fluid for a seven-day period. The variation of the pre- and post-irradiation contact angle and surface composition was determined through the quantification of the weight percentage of Ca and P crystals by the EDAX ZAF method (EDS). Statistically significant differences (p < 0.05) were found for samples irradiated with UVA over 48 h, corresponding with hydrophilic surfaces, and the same result was found for samples exposed to 3 h of UVC. Superhydrophilic surfaces were found in samples irradiated for 12, 24 and 48 h with UVC. The decrease in the carbon content is related with the increase in the surface content of Ca and P, and vice versa over the Cr-Co-Mo surfaces.

Resonance frequency analysis of dental implants placed at the posterior maxilla varying the surface treatment only: A randomized clinical trial

BACKGROUND

Chemical modifications of the dental implant surface that improve the wettability result in a faster and better osseointegration.

PURPOSE

The aim of this randomized clinical trial was to evaluate the implant stability quotient (ISQ) of implants with similar designs, treated with 2 surfaces, sandblasted acid-etched (SAE) and hydrophilic SAE, within the initial 16 weeks of healing.

MATERIAL AND METHODS

A total of 64 implants (32 SAE-control group and 32 modified SAE-test group) with the same design, length, and diameter (conical and compressive, 4.3 × 10 mm) were inserted into the posterior maxillae of 21 patients partially edentulous. The ISQ values were collected at post-surgery (T0), 1 week (T1), 2 weeks (T2), 3 weeks (T3), 5 weeks (T4), 8 weeks (T5), 12 weeks (T6), and 16 weeks (T7).

RESULTS

None of the implants failed. Test group presented ISQ values higher than the control group (ANOVA-P < .01) from T5 to T7. When comparing groups regarding the amount of time required to achieve ISQ ≥ 70 as a reference, there was a statistically significant difference (cox regression-P < .01), and a hazard ratio of 2.24 (CI 1.62-3.11). At the 1-year follow-up, there was a drop out of 1 patient, and 2 implants were no longer evaluated. Survival rate for both groups was 100% at the 1-year follow-up.

CONCLUSIONS

The current study suggests that implants with hydrophilic surface (modified SAE) integrate faster than implants with SAE surface. The stability gain of the test group was 2.24 times faster than the control group after 5 weeks of evaluation at the posterior region of the edentulous maxillae.

Effects of alkaline treatment for fibroblastic adhesion on titanium

Background:

The surface energy of titanium (Ti) implants is very important when determining hydrophilicity or hydrophobicity, which is vital in osseointegration. The purpose of this study was to determine how Ti plates with an alkaline treatment (NaOH) affect the adhesion and proliferation of human periodontal ligament fibroblasts (HPLF).

Materials and Methods:

In vitro experimental study was carried out. Type 1 commercially pure Ti plates were analyzed with atomic force microscopy to evaluate surface roughness. The plates were treated ultrasonically with NaOH at 5 M (pH 13.7) for 45 s. HPLF previously established from periodontal tissue was inoculated on the treated Ti plates. The adhered and proliferated viable cell numbers were determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method for 60 min and 24 h, respectively. The data were analyzed using Kruskal–Wallis tests and multiple comparisons of the Mann–Whitney U-test,P value was fixed at 0.05.

Results:

The mean roughness values equaled 0.04 μm with an almost flat surface and some grooves. The alkaline treatment of Ti plates caused significantly (P < 0.05) more pronounced HPLF adhesion and proliferation compared to untreated Ti plates.

Conclusion:

The treatment of Ti plates with NaOH enhances cell adhesion and the proliferation of HPLF cells. Clinically, the alkaline treatment of Ti-based implants could be an option to improve and accelerate osseointegration.

Effects of Surface Conditions of Titanium Dental Implants on Bacterial Adhesion

OBJECTIVE

The study is to evaluate the effect of surface roughness of titanium implants on bacterial adhesion and then to investigate the efficacy of the three cleaning treatments for bacterial removal in titanium surfaces.

BACKGROUND DATA

Although surface debridement is the basic element for treatment of peri-implantitis to reduce bacterial adhesion, adjunctive therapies such as antiseptics and laser debridement have been proposed to improve the nonsurgical treatment options of the peri-implant infection.

METHODS

Titanium specimens were divided into five groups: No. 1200 grit sandpaper polishing (Grit), 50 μm (SB50), 100 μm (SB100), and 250 μm Al2O3 sandblasting (SB250), and sandblasting, large-grit, and acid-etching (SLA). Surface roughness (Ra), contact angle, and surface morphology were examined. The subsequent adhesion of Escherichia coli on the different substrates was assayed. After 8 h of bacterial culture, three different cleaning treatments, including plastic curettage, air-powder abrasive system, and Er:YAG laser debridement, were applied on the specimens.

RESULTS

The Ra value changed from the lower value of 0.2 μm for the Grit group to the significantly higher value of 2.7 μm for the SB250 group, indicating a significant difference from the SLA group (2.0 μm). The average contact angle of SLA (101°) was significantly higher than the other groups. No significant difference in E. coli bacterial adhesion was found among the all roughened groups, except the SB50 and SB250 groups at 12 h of culture. The use of three cleaning treatments did not induce significant surface alterations. However, the E. coli adhesion was significantly reduced in the air-powder abrasive system and laser debridement in comparison with that treated with the plastic curettage.

CONCLUSIONS

Laser debridement could be a useful cleaning method for peri-implantitis therapy.

Topographic Cues Reveal Two Distinct Spreading Mechanisms in Blood Platelets

Blood platelets are instrumental in blood clotting and are thus heavily involved in early wound closure. After adhering to a substrate they spread by forming protrusions like lamellipodia and filopodia. However, the interaction of these protrusions with the physical environment of platelets while spreading is not fully understood. Here we dynamically image platelets during this spreading process and compare their behavior on smooth and on structured substrates. In particular we analyze the temporal evolution of the spread area, the cell morphology and the dynamics of individual filopodia. Interestingly, the topographic cues enable us to distinguish two spreading mechanisms, one that is based on numerous persistent filopodia and one that rather involves lamellipodia. Filopodia-driven spreading coincides with a strong response of platelet morphology to the substrate topography during spreading, whereas lamellipodia-driven spreading does not. Thus, we quantify different degrees of filopodia formation in platelets and the influence of filopodia in spreading on structured substrates.

Enhanced differentiation of human osteoblasts on Ti surfaces pre-treated with human whole blood

Early and effective integration of a metal implant into bone tissue is of crucial importance for its long-term stability. While different material properties including surface roughness and wettability but also initial blood-implant surface interaction are known to influence this osseointegration, implications of the latter process are still poorly understood. In this study, early interaction between blood and the implant surface and how this affects the mechanism of osseointegration were investigated. For this, blood coagulation on a micro-roughened hydrophobic titanium (Ti) surface (SLA-H(phob)) and on a hydrophilic micro-roughened Ti surface with nanostructures (SLActive-H(phil)NS), as well as the effects of whole human blood pre-incubation of these two surfaces on the differentiation potential of primary human bone cells (HBC) was assessed. Interestingly, pre-incubation with blood resulted in a dense fibrin network over the entire surface on SLActive-H(phil)NS but only in single patches of fibrin and small isolated fibre complexes on SLA-H(phob). On SLActive-H(phil)NS, the number of HBCs attaching to the fibrin network was greatly increased and the cells displayed enhanced cell contact to the fibrin network. Notably, HBCs displayed increased expression of the osteogenic marker proteins alkaline phosphatase and collagen-I when cultivated on both surfaces upon blood pre-incubation. Additionally, blood pre-treatment promoted an earlier and enhanced mineralization of HBCs cultivated on SLActive-H(phil)NS compared to SLA-H(phob). The results presented in this study therefore suggest that blood pre-incubation of implant surfaces mimics a more physiological situation, eventually providing a more predictive in vitro model for the evaluation of novel bone implant surfaces.