Cell-extracellular matrix interaction and physico-chemical characteristics of titanium surfaces depend on the roughness of the material

Anti-TLR4 biological response to titanium nitride-coated dental implants: anti-inflammatory response and extracellular matrix synthesis

Osteointegration is a key process during dental implant placement and is related to titanium surface topography. Implant coating and surface modification methods ameliorate the bone production and the osteogenic process. The current work aimed at evaluating the biological outcomes of two different surfaces of dental implants, machined and titanium nitride (TiN) coated, at an inflammation level using an in vitro model of human periodontal ligament stem cells. The TLR4/MyD88/NF-κB p65/NLRP3 pathway induced by the Porphyromonas gingivalis lipopolysaccharide was studied by means of gene- and protein-level expression. Moreover, the expression of vimentin, vinculin, and fibronectin was evaluated to investigate their effects on the cell adhesion and extracellular matrix deposition. The results of the present study suggest that TiN-coated titanium disks may modulate inflammation by the suppression of the TLR4/MyD88/NF-κB p65/NLRP3 pathway and accelerate extracellular matrix apposition.

Antibacterial Biomaterial Based on Bioglass Modified with Copper for Implants Coating

Biofilm-related implant infections pose a substantial threat to patients, leading to inflammation in the surrounding tissue, and often resulting in implant loss and the necessity for additional surgeries. Overcoming this implantology challenge is crucial to ensure the success and durability of implants. This study shows the development of antibacterial materials for implant coatings by incorporating copper into 45S5 Bioglass^®. By combining the regenerative properties of Bioglass^® with the antimicrobial effects of copper, this material has the potential to prevent infections, enhance osseointegration and improve the long-term success of implants. Bioglasses modified with various concentrations of CuO (from 0 to 8 mol%) were prepared with the melt-quenching technique. Structural analysis using Raman and FTIR spectroscopies did not reveal significant alterations in the bioglasses structure with the addition of Cu. The antibacterial activity of the samples was assessed against Gram-positive and Gram-negative bacteria, and the results demonstrated significant inhibition of bacterial growth for the bioglass with 0.5 mol% of CuO. Cell viability studies indicated that the samples modified with up to 4 mol% of CuO maintained good cytocompatibility with the Saos-2 cell line at extract concentrations up to 25 mg/mL. Furthermore, the bioactivity assessment demonstrated the formation of a calcium phosphate (CaP)-rich layer on the surfaces of all bioglasses within 24 h. Our findings show that the inclusion of copper in the bioglass offers a significant enhancement in its potential as a coating material for implants, resulting in notable advancements in both antibacterial efficacy and osteointegration properties.

Relevant Aspects of Titanium Topography for Osteoblastic Adhesion and Inhibition of Bacterial Colonization

The influence of the surface topography of dental implants has been studied to optimize titanium surfaces in order to improve osseointegration. Different techniques can be used to obtain rough titanium, however, their effect on wettability, surface energy, as well as bacterial and cell adhesion and differentiation has not been studied deeply. Two-hundred disks made of grade 4 titanium were subjected to different treatments: machined titanium (MACH), acid-attacked titanium (AE), titanium sprayed with abrasive alumina particles under pressure (GBLAST), and titanium that has been treated with GBLAST and then subjected to AE (GBLAST + AE). The roughness of the different treatments was determined by confocal microscopy, and the wettability was determined by the sessile drop technique; then, the surface energy of each treatment was calculated. Osteoblast-like cells (SaOs-2) were cultured, and alkaline phosphatase was determined using a colorimetric test. Likewise, bacterial strains S. gordonii, S. oralis, A. viscosus, and E. faecalis were cultured, and proliferation on the different surfaces was determined. It could be observed that the roughness of the GBLAST and GBLAS + AE was higher, at 1.99 and 2.13 μm of Ra, with respect to the AE and MACH samples, which were 0.35 and 0.20 μm, respectively. The abrasive treated surfaces showed lower hydrophilicity but lower surface energy. Significant differences could be seen at 21 days between SaOS-2 osteoblastic cell adhesion for the blasted ones and higher osteocalcin levels. However, no significant differences in terms of bacterial proliferation were observed between the four surfaces studied, demonstrating the insensitivity of bacteria to topography. These results may help in the search for the best topographies for osteoblast behavior and for the inhibition of bacterial colonization.

Osteoblastic Cell Behavior and Gene Expression Related to Bone Metabolism on Different Titanium Surfaces

The surface topography of titanium dental implants has a great influence on osseointegration. In this work, we try to determine the osteoblastic behavior and gene expression of cells with different titanium surfaces and relate them to the physicochemical properties of the surface. For this purpose, we have used commercial titanium discs of grade 3: as-received corresponds to machined titanium without any surface treatment (MA), chemically acid etched (AE), treated via sand blasting with Al₂O₃ particles (SB) and a sand-blasting treatment with acid etching (SB+AE). The surfaces have been observed using scanning electron microscopy (SEM) and the roughness, wettability and surface energy with dispersive and polar components have been characterized. Osteoblastic cultures were performed with SaOS-2 osteoblastic cells determining cell viability as well as alkaline phosphatase levels for 3 and 21 days, and osteoblastic gene expression was determined. The roughness values of the MA discs was 0.02 μm, which increases to 0.3 μm with acid attack and becomes the maximum for the sand-blasted samples, reaching values of 1.2 μm for SB and SB+AE. The hydrophilic behavior of the MA and AE samples with contact angles of 63° and 65° is superior to that of the rougher samples, being 75° for SB and 82° for SB+AE. In all cases, they show good hydrophilicity. GB and GB+AE surfaces present a higher polar component in the surface energy values, 11.96 and 13.18 mJ/m², respectively, than AE and MA, 6.64 and 9.79 mJ/m², respectively. The osteoblastic cell viability values at three days do not show statistically significant differences between the four surfaces. However, the viability of the SB and SB+AE surfaces at 21 days is much higher than that of the AE and MA samples. From the alkaline phosphatase studies, higher values were observed for those treated with sand blasting with and without acid etching compared to the other two surfaces, indicating a greater activity in osteoblastic differentiation. In all cases except in the Osterix (Ostx) -osteoblast-specific transcription factor-a decrease in gene expression is observed in relation to the MA samples (control). The most important increase was observed for the SB+AE condition. A decrease in the gene expression of Osteoprotegerine (OPG), Runt-related transcription factor 2 (Runx2), Receptor Activator of NF-κB Ligand (RANKL) and Alkaline Phosphatase (Alp) genes was observed in the AE surface.

Engineered Biomimetic Membranes for Organ-on-a-Chip

Organ-on-a-chip (OOC) systems are engineered nanobiosystems to mimic the physiochemical environment of a specific organ in the body. Among various components of OOC systems, biomimetic membranes have been regarded as one of the most important key components to develop controllable biomimetic bioanalysis systems. Here, we review the preparation and characterization of biomimetic membranes in comparison with the features of the extracellular matrix. After that, we review and discuss the latest applications of engineered biomimetic membranes to fabricate various organs on a chip, such as liver, kidney, intestine, lung, skin, heart, vasculature and blood vessels, brain, and multiorgans with perspectives for further biomedical applications.

Human osteoblasts response to different dental implant abutment materials: An in-vitro study

OBJECTIVES

This study aimed to investigate human osteoblasts (HOB) response towards different dental implant abutment materials.

METHODS

Five dental implant abutment materials were investigated: (1) titanium (Ti), (2) titanium coated nitride (TiN), (3) cobalt chromium (CoCr), (4) zirconia (ZrO₂), and (5) modified polyether ether ketone (m-PEEK). HOBs were cultured, expanded, and seeded according to the supplier's protocol (PromoCell, UK). Cell proliferation and cytotoxicity were evaluated at days 1, 3, 5, and 10 using Alamar Blue (alamarBlue) and lactate dehydrogenase (LDH) colorimetric assays. Data were analysed via two-way ANOVA, one-way ANOVA and Tukey's post hoc test (significance was determined as p < 0.05 for all tests).

RESULTS

All the investigated materials showed high and comparable initial proliferation activities apart from ZrO₂ (46.92%), with P% of 79.91%, 68.77%, 73.20%, and 65.46% for Ti, TiN, CoCr, and m-PEEK, respectively. At day 10, all materials exhibited comparable and lower P% than day 1 apart from TiN (70.90%) with P% of 30.22%, 40.64%, 37.27%, and 50.65% for Ti, CoCr, ZrO₂, and m-PEEK, respectively. The cytotoxic effect of the investigated materials was generally low throughout the whole experiment. At day 10, the cytotoxicity % was 7.63%, 0.21%, 13.30%, 5.32%, 8.60% for Ti, TiN, CoCr, ZrO₂, and m-PEEK. The Two-way ANOVA and Tukey's Multiple Comparison Method highlighted significant material and time effects on cell proliferation and cytotoxicity, and a significant interaction (p < 0.0001) between the tested materials. Notably, TiN and m-PEEK showed improved HOB proliferation activity and cytotoxic levels than the other investigated materials. In addition, a non-significant negative correlation between viability and cytotoxicity was found for all tested materials. Ti (p = 0.07), TiN (p = 0.28), CoCr (p = 0.15), ZrO₂ (p = 0.17), and m-PEEK (p = 0.12).

SIGNIFICANCE

All the investigated materials showed excellent biocompatibility properties with more promising results for the newly introduced TiN and m-PEEK as alternatives to the traditionally used dental implant and abutment materials.

Effects of Titanium Implant Surface Topology on Bone Cell Attachment and Proliferation in vitro

Purpose

Titanium is commonly used for implants because of its corrosion resistance and osseointegration capability. It is well known that surface topology affects the response of bone tissue towards implants. In vivo studies have shown that in weeks or months, bone tissue bonds more efficiently to titanium implants with rough surfaces compared to smooth surfaces. In addition, stimulating early endosseous integration increases the long-term stability of bone-implants and hence their clinical outcome. Here, we evaluated the response of human MG-63 osteoblast-like cells to flat and solid, compared to rough and porous surface topologies in vitro 1–6 days post seeding. We compared the morphology, proliferation, and attachment of cells onto three smooth surfaces: tissue culture (TC) plastic or microscope cover glasses, machined polyether-ether-ketone (PEEK), and machined solid titanium, to cells on a highly porous (average R_a 22.94 μm) plasma-sprayed titanium surface (composite Ti-PEEK spine implants).

Methods

We used immuno-fluorescence (IF) and scanning electron microscopy (SEM), as well as Live/Dead and WST-1 cell proliferation assays.

Results

SEM analyses confirmed the rough topology of the titanium implant surface, compared to the smooth surface of PEEK, solid titanium, TC plastic and cover glasses. In addition, SEM analyses revealed that MG-63 cells seeded onto smooth surfaces (solid titanium, PEEK) adopted a flat, planar morphology, while cells on the rough titanium surface adopted an elongated morphology with numerous filopodial and lamellipodial extensions interacting with the substrate. Finally, IF analyses of focal adhesions (vinculin, focal adhesion kinase), as well as proliferation assays indicate that MG-63 cells adhere less and proliferate at a slower rate on the rough than on a smooth titanium surface.

Conclusion

These observations suggest that bone-forming osteoblasts adhere less strongly and proliferate slower on rough compared to smooth titanium surfaces, likely promoting cell differentiation, which is in agreement with other porous implant materials.

Into the Tissues: Extracellular Matrix and Its Artificial Substitutes: Cell Signalling Mechanisms

The existence of orderly structures, such as tissues and organs is made possible by cell adhesion, i.e., the process by which cells attach to neighbouring cells and a supporting substance in the form of the extracellular matrix. The extracellular matrix is a three-dimensional structure composed of collagens, elastin, and various proteoglycans and glycoproteins. It is a storehouse for multiple signalling factors. Cells are informed of their correct connection to the matrix via receptors. Tissue disruption often prevents the natural reconstitution of the matrix. The use of appropriate implants is then required. This review is a compilation of crucial information on the structural and functional features of the extracellular matrix and the complex mechanisms of cell–cell connectivity. The possibilities of regenerating damaged tissues using an artificial matrix substitute are described, detailing the host response to the implant. An important issue is the surface properties of such an implant and the possibilities of their modification.

DNA/Magnetic Nanoparticles Composite to Attenuate Glass Surface Nanotopography for Enhanced Mesenchymal Stem Cell Differentiation

Mesenchymal stem cells (MSCs) have extensive pluripotent potential to differentiate into various cell types, and thus they are an important tool for regenerative medicine and biomedical research. In this work, the differentiation of hTERT-transduced adipose-derived MSCs (hMSCs) into chondrocytes, adipocytes and osteoblasts on substrates with nanotopography generated by magnetic iron oxide nanoparticles (MNPs) and DNA was investigated. Citrate-stabilized MNPs were synthesized by the chemical co-precipitation method and sized around 10 nm according to microscopy studies. It was shown that MNPs@DNA coatings induced chondrogenesis and osteogenesis in hTERT-transduced MSCs. The cells had normal morphology and distribution of actin filaments. An increase in the concentration of magnetic nanoparticles resulted in a higher surface roughness and reduced the adhesion of cells to the substrate. A glass substrate modified with magnetic nanoparticles and DNA induced active chondrogenesis of hTERT-transduced MSC in a twice-diluted differentiation-inducing growth medium, suggesting the possible use of nanostructured MNPs@DNA coatings to obtain differentiated cells at a reduced level of growth factors.

Titanium Substratum Roughness as a Determinant of Human Gingival Fibroblast Fibronectin and α-Smooth Muscle Actin Expression

The most appropriate surface treatment to enhance gingival connective tissue formation on the abutment of dental implants remains undefined, with healing associated with a scar-like response. We have previously shown that topographies with an arithmetic average of the absolute profile height deviations (R_a) = 4.0 induces an anti-fibrotic phenotype in human gingival fibroblasts (HGFs) by causing nascent adhesion formation. With bacterial colonization considerations, we hypothesized that a lower R_a could be identified that would alter adhesion stability and promote a matrix remodeling phenotype. Focal adhesions (FAs) area decreased with increasing roughness, although no differences in cell attachment or proliferation were observed. Alpha smooth muscle actin (α-SMA) protein levels were significantly reduced on R_a = 3.0 and 4.0 vs. 0.1 (p < 0.05), with incorporation of α-SMA into stress fibers most prominent on R_a = 0.1. Fibronectin protein levels were reduced on 3.0 and 4.0 vs. 0.1 (p < 0.05), and R_a = 1.5 and deeper significantly altered fibronectin deposition. Addition of exogenous TGF-β3 increased HGF adhesion size on 0.1 surfaces, but not on any other topography. We conclude that R_a = 1.5 is sufficient to reduce adhesion size and inhibit α-SMA incorporation into stress fibers in HGFs, but 3.0 is required in the presence of exogenous TGF-β3. Our findings have implications for inhibiting fibrotic tissue formation surrounding percutaneous devices such as dental implants.

NUMERICAL APPROACH TO QUANTIFY AND CHARACTERIZE INTERFACE MECHANICAL BEHAVIOR BETWEEN THIN LAYER SUBSTRATE AND BIOLOGICAL TISSUES

In this paper, we investigate the behavior of biological tissues (skin) coupled to a substrate (sensor) based on a numerical model taking into account the relationship between strain/stress components at the interface. Based on this study, we understand and quantify the most appropriate biomechanical factors in order to optimize sensor/biological tissue interface conditions. A micromechanical description based on a mathematical formulation has been developed to evaluate the biomechanical behavior provided by a 2D viscoelastic model of Kelvin–Voigt. The results show a spatio-temporal law of tissue motion highlighting the need for an optimized interface for reliable data transmission in the case of connected device in a dynamic movement or in the manufacturing of intelligent and reactive prosthesis device.

Surface roughness of titanium disks influences the adhesion, proliferation and differentiation of osteogenic properties derived from human

PURPOSE

The aim of this study was to investigate the response of osteogenic cell lineage and gingival fibroblastic cells to different surface treatments of grade IV commercially pure Titanium (cpTi) disks.

MATERIAL AND METHODS

Grade IV cpTi disks with different surfaces were produced: machined (M), sandblasting (B), sandblasting and acid subtraction (NP), and hydrophilic treatment (ACQ). Surface microtopography characteristics and chemical composition were investigated by scanning electron microscopy (SEM) and energy dispersive x-ray spectrometry (EDS). Adhesion and proliferation of SC-EHAD (human surgically-created early healing alveolar defects) and HGF-1 (human gingival fibroblasts) on Ti disks were investigated at 24 and 48 h, and osteogenic differentiation and mineralization were evaluated by assessing alkaline phosphatase (ALP) activity and alizarin red staining, respectively.

RESULTS

No significant differences were found among the various surface treatments for all surface roughness parameters, except for skewness of the assessed profile (Rsk) favoring M (p = 0.035 ANOVA). M disks showed a slightly higher (p > 0.05; Kruskal-Wallis/Dunn) adhesion of HGF-1 (89.43 ± 9.13%) than SC-EHAD cells (57.11 ± 17.72%). ACQ showed a significantly higher percentage of SC-EHAD (100%) than HGF-1 (69.67 ± 13.97%) cells adhered at 24 h. SC-EHAD cells expressed increased ALP activity in osteogenic medium at M (213%) and NP (235.04%) surfaces, but higher mineralization activity on ACQ (54.94 ± 4.80%) at 14 days.

CONCLUSION

These findings suggest that surface treatment influences the chemical composition and the adhesion and differentiation of osteogenic cells in vitro.

CLINICAL RELEVANCE

Hydrophilic surface treatment of grade IV cpTi disks influences osteogenic cell adhesion and differentiation, which might enhance osseointegration.

Achievements in the Topographic Design of Commercial Titanium Dental Implants: Towards Anti-Peri-Implantitis Surfaces

Titanium and its alloys constitute the gold standard materials for oral implantology in which their performance is mainly conditioned by their osseointegration capacity in the host's bone. We aim to provide an overview of the advances in surface modification of commercial dental implants analyzing and comparing the osseointegration capacity and the clinical outcome exhibited by different surfaces. Besides, the development of peri-implantitis constitutes one of the most common causes of implant loss due to bacteria colonization. Thus, a synergic response from industry and materials scientists is needed to provide reliable technical and commercial solutions to this issue. The second part of the review focuses on an update of the recent findings toward the development of new materials with osteogenic and antibacterial capacity that are most likely to be marketed, and their correlation with implant geometry, biomechanical behavior, biomaterials features, and clinical outcomes.

Flat and microstructured polymeric membranes in organs-on-chips

In recent years, organs-on-chips (OOCs) have been developed to meet the desire for more realistic in vitro cell culture models. These systems introduce microfluidics, mechanical stretch and other physiological stimuli to in vitro models, thereby significantly enhancing their descriptive power. In most OOCs, porous polymeric membranes are used as substrates for cell culture. The polymeric material, morphology and shape of these membranes are often suboptimal, despite their importance for achieving ideal cell functionality such as cell-cell interaction and differentiation. The currently used membranes are flat and thus do not account for the shape and surface morphology of a tissue. Moreover, the polymers used for fabrication of these membranes often lack relevant characteristics, such as mechanical properties matching the tissue to be developed and/or cytocompatibility. Recently, innovative techniques have been reported for fabrication of porous membranes with suitable porosity, shape and surface morphology matching the requirements of OOCs. In this paper, we review the state of the art for developing these membranes and discuss their application in OOCs.

Establishment of a Numerical Model to Design an Electro-Stimulating System for a Porcine Mandibular Critical Size Defect

Electrical stimulation is a promising therapeutic approach for the regeneration of large bone defects. Innovative electrically stimulating implants for critical size defects in the lower jaw are under development and need to be optimized in silico and tested in vivo prior to application. In this context, numerical modelling and simulation are useful tools in the design process. In this study, a numerical model of an electrically stimulated minipig mandible was established to find optimal stimulation parameters that allow for a maximum area of beneficially stimulated tissue. Finite-element simulations were performed to determine the stimulation impact of the proposed implant design and to optimize the electric field distribution resulting from sinusoidal low-frequency ( f = 20 Hz ) electric stimulation. Optimal stimulation parameters of the electrode length h el = 25 m m and the stimulation potential φ stim = 0.5 V were determined. These parameter sets shall be applied in future in vivo validation studies. Furthermore, our results suggest that changing tissue properties during the course of the healing process might make a feedback-controlled stimulation system necessary.

Effect of plasma-nitrided titanium surfaces on the differentiation of pre-osteoblastic cells

A titanium surface nitrided by plasma contains nitrogen ions that guarantee resistance to corrosion and biocompatibility. Despite this, no descriptions concerning the influence of the expression of cell adhesion proteins and their influence on osteogenic cell differentiation are available. Thus, the present study aimed to assess the response of murine pre-osteoblastic cells (MC3T3-E1) cultured on nitrided titanium surfaces. Pre-osteoblastic cells were grown on polished titanium discs, used as controls, and on previously characterized plasma-nitrided titanium discs. Cells from both groups were submitted to the MTT cell viability test. The expressions of α5, α2, and β1 integrin were assessed by flow cytometry and immunofluorescence, while osteocalcin expression was assessed by flow cytometry. The nitrided surface presented higher α2 and β1 integrin expressions, as well as osteocalcin expression, when compared to the polished surface, with no alterations in cell viability. These findings seem to suggest that the plasma nitriding treatment produces a titanium surface with the potential for effective in vitro osseointegration.

Photochemical Surface Modification of Titanium Dioxide Nanotube-Coated Surfaces by Ag-Hydroxyapatite Compositions

Silver-hydroxyapatite coatings prepared from Ag3PO4 microcrystals have been deposited on titanium dioxide nanotubes supported by titanium disks by photodecomposition of predeposited Ag3PO4 microcrystals or their coprecipitate with hydroxyapatite. The SEM-EDS characterization has confirmed excellent film uniformity and consistent deposition over the surface, which is essential for improving osseointegration of tunable antibacterial bone implants.

Experimental study on the biocompatibility of keratoprosthesis with improved titanium implant

AIM

To investigate whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) implant biointegration, ultimately to decrease the risk of implant-associated complications.

METHODS

The modified titanium implant was designed and prepared for artificial cornea. The titanium implant was treated with sandblasting and hydroxyapatite coating by acid-base two-step method. Surface was analyzed by scanning electron microscopy (SEM), KPro implants coated with HAp and KPro implant sandblasted were implanted in rabbits. Tissue adhesion to the implant was assessed and compared to an unmodified implant by histopathology (HE), transmission electron microscopy (TEM) and SEM.

RESULTS

SEM demonstrated successful deposition of HAp on titanium implant sandblasted (HA/SB-Ti). The hydroxyapatite coatings caused enhancement of keratocyte proliferation compared with unmodified implant surfaces. HAp coating significantly increased adhesion forces. HAp coating of implants reduced the inflammatory response around the KPro implants in vivo.

CONCLUSION

HAp-coated surfaces for use in titanium KPro implant greatly enhanced adherence of the titanium KPro implant in the rabbit cornea.

The Surface Anodization of Titanium Dental Implants Improves Blood Clot Formation Followed by Osseointegration

The anodization of titanium dental implant influences the biologic processes of osseointegration. 34 grit-blasted and acid-etched titanium specimens were used to evaluate micro- and nano-roughness (Ra), contact angle (θ) and blood clot extension (bce). 17 samples were anodized (test) while the remaining were used as control. The bce, was measured using 10 µL of human blood left in contact with titanium for 5 min at room temperature. The micro- and nano-scale Ra were measured under CLSM and AFM, respectively, while the θ was analyzed using the sessile drop technique. The bone-implant contact (BIC) rate was measured on two narrow implants retrieved for fracture. bce was 42.5 (±22) for test and 26.6% (±13)% for control group (p = 0.049). The micro-Ra was 6.0 (±1.5) for the test and 5.8 (±1.8) µm for control group (p > 0.05). The θ was 98.5° (±18.7°) for test and 103° (±15.2°) for control group (p > 0.05). The nano-Ra was 286 (±40) for the test and 226 (±40) nm for control group (p < 0.05). The BIC rate was 52.5 (±2.1) for test and 34.5% (±2.1%) for control implant (p = 0.014). (Conclusions) The titanium anodized surface significantly increases blood clot retention, significantly increases nano-roughness, and favors osseointegration. When placing dental implants in poor bone quality sites or with immediate loading protocol anodized Ti6Al4V dental implants should be preferred.

Emphasizing the role of surface chemistry on hydrophobicity and cell adhesion behavior of polydimethylsiloxane/TiO2 nanocomposite films

Improving the bioinertness of materials is of great importance for developing biomedical devices that contact human tissues. The main goal of this study was to establish correlations among surface morphology, roughness and chemistry with hydrophobicity and cell adhesion in polydimethylsiloxane (PDMS) nanocomposites loaded with titanium dioxide (TiO₂) nanoparticles. Firstly, wettability results showed that the nanocomposite loaded with 30 wt.% of TiO₂ exhibited a superhydrophobic behavior; however, the morphology and roughness analysis proved that there was no discernible difference between the surface structures of samples loaded with 20 and 30 wt.% of nanoparticles. Both cell culture and MTT assay experiments showed that, despite the similarity between the surface structures, the sample loaded with 30 wt.% nanoparticles exhibits the greatest reduction in the cell viability (80%) as compared with the pure PDMS film. According to the X-ray photoelectron spectroscopy results, the remarkable reduction in cell viability of the superhydrophobic sample could be majorly attributed to the role of surface chemistry. The obtained results emphasize the importance of adjusting the surface properties especially surface chemistry to gain the optimum cell adhesion behavior.

Simple fabrication of rough halloysite nanotubes coatings by thermal spraying for high performance tumor cells capture

Here, we reported a fast, low-cost, and effective fabrication method of large-area and rough halloysite nanotubes (HNTs) coatings by thermal spraying of HNTs ethanol dispersions. A uniform HNTs coating with high transparence is achieved with tailorable surface roughness and thickness. Compared with normal cells, the tumor cells can be captured effectively with high capture yield by the HNTs coatings (expect HeLa cells), which is attributed to the enhanced topographic interactions between HNTs coating and cancer cells. HNTs coating formed from 2.5% ethanol dispersions shows the highest tumor cells capture yeild (90%), which is related to the appropriate roughness and anti-EpCAM conjugation. The capture yield of HNTs coating towards MCF-7 cells can be further improved to 93% within 2h under dynamic shear using a peristaltic pump. The capture yield increases with the incubation time, and the flow rate with 1.25mL/min leads to the maximum capture yield. The HNTs coatings are also effective for capture of tumor cells spiked in artificial blood samples and blood samples from patients with metastatic breast cancer. More than 90% targeted MCF-7 cells and very small amounts of white blood cells are captured by the anti-EpCAM conjugated HNTs coatings from a blood sample. HNTs are further loaded anticancer drug doxorubicin (DOX) and then thermally sprayed into coatings. The MCF-7 cells captured on DOX loaded HNTs coating display significant membrane rupture characteristic and only 3% cell viability after 16h. The high capture efficiency of tumor cells by HNTs coating fabricated by the thermal spraying method makes them show promising applications in clinical circulating tumor cells capture for early diagnosis and monitoring of cancer patients. The high killing ability of the DOX loaded HNTs coating can also be designed as an implantable therapeutic device for preventing tumor metastasis.

Control of dental-derived induced pluripotent stem cells through modified surfaces for dental application

OBJECTIVE

The aim of this study is to investigate the behaviour of iPSc derived from dental stem cells in terms of initial adhesion, differentiation potential on differently surface-treated titanium disc.

MATERIALS AND METHODS

iPSc derived from human gingival fibroblasts (hGFs) were established using 4-reprogramming factors transduction with Sendai virus. The hGF-iPSc established in this study exhibited the morphology and growth properties similar to human embryonic stem (ES) cells and expressed pluripotency makers. Alkaline Phosphatase (AP) staining, Embryoid Body (EB) formation and in vitro differentiation and karyotyping further confirmed pluripotency of hGF-iPSc. Then, hGF-iPSc were cultured on machined- and Sandblasted and acid etched (SLA)-treated titanium discs with osteogenic induction medium and their morphological as well as quantitative changes according to different surface types were investigated using Alizrin Red S staining, Scanning electron microscopy (SEM), Flow cytometry and RT-PCR.

RESULTS

Time-dependent and surface-dependent morphological changes as well as quantitative change in osteogenic differentiation of hGF-iPSc were identified and osteogenic gene expression of hGF-iPSc cultured on SLA-treated titanium disc found to be greater than machined titanium disc, suggesting the fate of hGF-iPSc may be determined by the characteristics of surface to which hGF-iPSc first adhere.

CONCLUSIONS

iPSc derived from dental stem cell can be one of the most promising and practical cell sources for personalized regenerative dentistry and their morphological change as well as quantitative change in osteogenic differentiation according to different surface types may be further utilized for future clinical application incorporated with dental implant.

Proliferation, behavior, and differentiation of osteoblasts on surfaces of different microroughness

OBJECTIVES

Titanium surface roughness is recognized as an important parameter influencing osseointegration. However, studies concerning the effect of well-defined surface topographies of titanium surfaces on osteoblasts have been limited in scope. In the present study we have investigated how Ti surfaces of different micrometer-scale roughness influence proliferation, migration, and differentiation of osteoblasts in-vitro.

METHODS

Titanium replicas with surface roughnesses (Ra) of approximately 0, 1, 2, and 4μm were produced and MG-63 osteoblasts were cultured on these surfaces for up to 5 days. The effect of surface micrometer-scale roughness on proliferation, migration in time-lapse microscopy experiments, as well as the expression of alkaline phosphatase, osteocalcin, vascular-endothelial growth factor (VEGF), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-B ligand (RANKL) were investigated.

RESULTS

Proliferation of MG-63 cells was found to decrease gradually with increasing surface roughness. However, the highest expression of alkaline phosphatase, osteocalcin and VEGF was observed on surfaces with Ra values of approximately 1 and 2μm. Further increase in surface roughness resulted in decreased expression of all investigated parameters. The cell migration speed measured in time-lapse microscopy experiments was significantly lower on surfaces with a Ra value of about 4μm, compared to those with lower roughness. No significant effect of surface roughness on the expression of OPG and RANKL was observed.

SIGNIFICANCE

Thus, surfaces with intermediate Ra roughness values of 1-2μm seem to be optimal for osteoblast differentiation. Neither proliferation nor differentiation of osteoblasts appears to be supported by surfaces with higher or lower Ra values.

3D Printed scaffolds with bactericidal activity aimed for bone tissue regeneration

Nowadays, the incidence of bone disorders has steeply ascended and it is expected to double in the next decade, especially due to the ageing of the worldwide population. Bone defects and fractures lead to reduced patient's quality of life. Autografts, allografts and xenografts have been used to overcome different types of bone injuries, although limited availability, immune rejection or implant failure demand the development of new bone replacements. Moreover, the bacterial colonization of bone substitutes is the main cause of implant rejection. To vanquish these drawbacks, researchers from tissue engineering area are currently using computer-aided design models or medical data to produce 3D scaffolds by Rapid Prototyping (RP). Herein, Tricalcium phosphate (TCP)/Sodium Alginate (SA) scaffolds were produced using RP and subsequently functionalized with silver nanoparticles (AgNPs) through two different incorporation methods. The obtained results revealed that the composite scaffolds produced by direct incorporation of AgNPs are the most suitable for being used in bone tissue regeneration since they present appropriate mechanical properties, biocompatibility and bactericidal activity.

Relevant aspects in the surface properties in titanium dental implants for the cellular viability

Roughness and topographical features are the most relevant of the surface properties for a dental implant for its osseointegration. For that reason, we studied the four surfaces more used in titanium dental implants: machined, sandblasted, acid etching and sandblasted plus acid etching. The roughness and wettability (contact angle and surface free energy) was studied by means 3D-interferometric microscope and sessile drop method. Normal human gingival fibroblasts (HGF) were obtained from small oral mucosa biopsies and were used for cell cultures. To analyze cell integrity, we first quantified the total amount of DNA and LDH released from dead cells to the culture medium. Then, LIVE/DEAD assay was used as a combined method assessing cell integrity and metabolism. All experiments were carried out on each cell type cultured on each Ti material for 24h, 48h and 72h. To evaluate the in vivo cell adhesion capability of each Ti surface, the four types of discs were grafted subcutaneously in 5 Wistar rats. Sandblasted surfaces were significantly rougher than acid etching and machined. Wettability and surface free energy decrease when the roughness increases in sand blasted samples. This fact favors the protein adsorption. The DNA released by cells cultured on the four Ti surfaces did not differ from that of positive control cells (p>0.05). The number of cells per area was significantly lower (p<0.05) in the sand-blasted surface than in the machined and surface for both cell types (7±2 cells for HGF and 10±5 cells for SAOS-2). The surface of the machined-type discs grafted in vivo had a very small area occupied by cells and/or connective tissue (3.5%), whereas 36.6% of the sandblasted plus acid etching surface, 75.9% of sandblasted discs and 59.6% of acid etching discs was covered with cells and connective tissue. Cells cultured on rougher surfaces tended to exhibit attributes of more differentiated osteoblasts than cells cultured on smoother surfaces. These surface properties justify that the sandblasted implants is able to significantly increase bone contact and bone growth with very good osseointegration results in vivo.

A histological study of mineralised tissue formation around implants with 3D culture of HMS0014 cells in Cellmatrix Type I-A collagen gel scaffold in vitro

We cultured HMS0014 Yub621b cells within a 3D collagen gel scaffold (Cellmatrix Type I-A) and aimed to study the fate and contribution of human bone-derived mesenchymal stem cells (MSCs) in the guided bone regeneration(GBR)-engineered tissue which has developed around the titanium (Ti) test dental implant (IP) in vitro. The light microscopy (LM) and transmission electron microscopy (TEM) results of the peri-IP tissue indicated that collagen fibrils of the Cellmatrix Type I-A gel were accumulated and fabricated to provide a 3D meshwork for proliferation and differentiation of the HMS0014 cells in the top (cell) layer; mineralisation of the GBR tissue had commenced since day 1 and became markedly deposited between days 7 and 14 of the experiment. TEM observation revealed sedimentation of cement line at the periphery of the interwoven Cellmatrix fibres and fibrils in the ECM scaffold of the GBR tissue; matrix vesicle-mediated and appositional collagen-mediated mineralisation were identified in the peri-IP ECM scaffold. The fine structure study of the plurimorphic osteoblast(Ob)-like osteogeneic cells demonstrated numerous membranous organelles related with vesicular trafficking, secretion and endocytosis in the cytoplasm; well-developed cytoskeleton networks and intercellular junctional complexes were also observed. The specimens on fluorescence immunohistochemistry (IHC) by confocal laser-scanning microscopy (LSM) showed the expression of LC3 and Cx43 associated with autophagic-lysosomal degeneration pathway and signal conduction mediated with gap junctions (GJS) in maintaining tissue homeostasis of the Ob-like cells which grew and degenerated in the 3D scaffold. Results from this in vitro study suggest that Ob-like HMS0014 cells actively regulate turnover of the peri-IP ECM to recapitulate the development and formation of osteoid tissue-engineered material which might contribute to augment osseointegration around the dental implant.

Assessment of human gingival fibroblast interaction with dental implant abutment materials

The biocompatibility of dental implant abutment materials depends on numerous factors including the nature of the material, its chemical composition, roughness, texture, hydrophilicity and surface charge. The aim of the present study was to compare the viability and adhesion strength of human gingival fibroblasts (HGFs) grown on several dental materials used in implant prosthodontics. Surfaces of the tested materials were assessed using an optical imaging profiler. For material toxicity and cellular adhesion evaluation, primary human gingival fibroblast cells were used. To evaluate the strength of cellular adhesion, gingival fibroblasts were cultured on the tested materials and subjected to lateral shear forces by applying 300 and 500 rpm shaking intensities. Focal adhesion kinase (FAK) expression and phosphorylation in cells grown on the specimens were registered by cell-based ELISA. There was a tendency of fibroblast adhesion strength to decrease in the following order: sandblasted titanium, polished titanium, sandblasted zirconium oxide, polished zirconium oxide, gold-alloy, chrome-cobalt alloy. Higher levels of total as well as phospho-FAK protein were registered in HGFs grown on roughened titanium. Material type and surface processing technique have an impact on gingival fibroblast interaction with dental implant abutment materials.

Enhanced biological performance on nano-microstructured surfaces assembled by SrTiO3 cubic nanocrystals

Controlling protein adsorption on material surfaces can offer significant opportunities in terms of engineering the material–cell interactions.

The effect of physical and chemical cues on hepatocellular function and morphology

Physical topographical features and/or chemical stimuli to the extracellular matrix (ECM) provide essential cues that manipulate cell functions. From the physical point of view, contoured nanostructures are very important for cell behavior in general, and for cellular functions. From the chemical point of view, ECM proteins containing an RGD sequence are known to alter cell functions. In this study, the influence of integrated physical and chemical cues on a liver cell line (HepG2) was investigated. To mimic the physical cues provided by the ECM, amorphous TiO2 nanogratings with specific dimensional and geometrical characteristics (nanogratings 90 nm wide and 150 nm apart) were fabricated. To mimic the chemical cues provided by the ECM, the TiO2 inorganic film was modified by immobilization of the RGD motif. The hepatic cell line morphological and functional changes induced by simultaneously combining these diversified cues were investigated, including cellular alignment and the expression of different functional proteins. The combination of nanopatterns and surface modification with RGD induced cellular alignment and expression of functional proteins, indicating that physical and chemical cues are important factors for optimizing hepatocyte function.

Fibrin clot extension on zirconia surface for dental implants: a quantitative in vitro study

PURPOSE

The surface chemical and physical properties of materials used for implants have a major influence on blood clot organization. This study aims to evaluate the blood clot extension (bce) on zirconia and titanium. bce was measured in association to surface roughness (Ra) and static contact angle (θ).

MATERIALS AND METHODS

Forty disk-shaped samples of sandblasted yttria tetragonal zirconia polycrystal (sb-YTZP), machined titanium (m-Ti), and sandblasted, high-temperature, acid-etched titanium (p-Ti) were used in the present study. About 0.2 mL of human blood, immediately dropped onto the specimen's surface and left in contact for 5 minutes at room temperature, was used to measure the bce. Specimens were observed under confocal scanning laser and scanning electron microscopes.

RESULTS

The bce (mean × 10(7)  ± standard deviation [SD] × 10(6)  μm(2) ) was 2.97 ± 6.68 for m-Ti, 5.64 ± 6.83 for p-Ti, and 3.61 ± 7.67 for sb-YTZP. p-Ti samples showed a significantly higher bce. Ra (mean ± SD [μm]) was 0.56 ± 0.7 for m-Ti, 3.78 ± 0.8 for p-Ti, and 2.68 ± 0.6 for sb-YTZP. The difference was not significant between sb-YTZP and p-Ti. θ (mean ± SD) was 55.6 ± 5.6 for m-Ti, 48.7 ± 2.8 for sb-YTZP, and 38.0 ± 2.2 for p-Ti. The difference was not significant between m-Ti and sb-YTZP.

CONCLUSIONS

The sb-YTZP demonstrated a significantly lesser amount of bce compared with p-Ti specimens, notwithstanding that any significant difference was present between Ra and θ.

Impact of plasma chemistry versus titanium surface topography on osteoblast orientation

Topographical and chemical modifications of biomaterial surfaces both influence tissue physiology, but unfortunately little knowledge exists as to their combined effect. There are many indications that rough surfaces positively influence osteoblast behavior. Having determined previously that a positively charged, smooth titanium surface boosts osteoblast adhesion, we wanted to investigate the combined effects of topography and chemistry and elucidate which of these properties is dominant. Polished, machined and corundum-blasted titanium of increasing microroughness was additionally coated with plasma-polymerized allylamine (PPAAm). Collagen I was then immobilized using polyethylene glycol diacid and glutar dialdehyde. On all PPAAm-modified surfaces (i) adhesion of human MG-63 osteoblastic cells increased significantly in combination with roughness, (ii) cells resemble the underlying structure and melt with the surface, and (iii) cells overcome the restrictions of a grooved surface and spread out over a large area as indicated by actin staining. Interestingly, the cellular effects of the plasma-chemical surface modification are predominant over surface topography, especially in the initial phase. Collagen I, although it is the gold standard, does not improve surface adhesion features comparably.

Orthopedics and biofilm--what do we know? A review

Bacteria have been found to grow predominantly in biofilms. The initial stage includes the attachment of bacteria to the substratum. Bacterial growth and division then leads to the colonization of the surrounding area and the formation of the biofilm. The environment in a biofilm is not homogeneous; the bacteria in a multispecies biofilm are not randomly distributed, but rather are organized to best meet their needs.

Although there is an initial understanding on the mechanisms of biofilm-associated antimicrobial resistance, this topic is still under investigation. A variety of approaches are being explored to overcome biofilm-associated antimicrobial resistance. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.

Automatic Actin Filament Quantification of Osteoblasts and Their Morphometric Analysis on Microtextured Silicon-Titanium Arrays

Microtexturing of implant surfaces is of major relevance in the endeavor to improve biorelevant implant designs. In order to elucidate the role of biomaterial’s topography on cell physiology, obtaining quantitative correlations between cellular behavior and distinct microarchitectural properties is in great demand. Until now, the microscopically observed reorganization of the cytoskeleton on structured biomaterials has been difficult to convert into data. We used geometrically microtextured silicon-titanium arrays as a model system. Samples were prepared by deep reactive-ion etching of silicon wafers, resulting in rectangular grooves (width and height: 2 µm) and cubic pillars (pillar dimensions: 2 × 2 × 5 and 5 × 5 × 5 µm); finally sputter-coated with 100 nm titanium. We focused on the morphometric analysis of MG-63 osteoblasts, including a quantification of the actin cytoskeleton. By means of our novel software FilaQuant, especially developed for automatic actin filament recognition, we were first able to quantify the alterations of the actin network dependent on the microtexture of a material surface. The cells’ actin fibers were significantly reduced in length on the pillared surfaces versus the grooved array (4–5 fold) and completely reorganized on the micropillars, but without altering the orientation of cells. Our morpho-functional approach opens new possibilities for the data correlation of cell-material interactions.

Effect of blasting treatment and Fn coating on MG63 adhesion and differentiation on titanium: a gene expression study using real-time RT-PCR

Biomaterial surface properties, via alterations in the adsorbed protein layer, and the presence of specific functional groups can influence integrin binding specificity, thereby modulating cell adhesion and differentiation processes. The adsorption of fibronectin, a protein directly involved in osteoblast adhesion to the extracellular matrix, has been related to different physical and chemical properties of biomaterial surfaces. This study used blasting particles of different sizes and chemical compositions to evaluate the response of MG63 osteoblast-like cells on smooth and blasted titanium surfaces, with and without fibronectin coatings, by means of real-time reverse transcription-polymerase chain reaction (qRT-PCR) assays. This response included (a) expression of the α(5), α(v) and α(3) integrin subunits, which can bind to fibronectin through the RGD binding site, and (b) expression of alkaline phosphatase (ALP) and osteocalcin (OC) as cell-differentiation markers. ALP activity and synthesis of OC were also tested. Cells on SiC-blasted Ti surfaces expressed higher amounts of the α(5) mRNA gene than cells on Al(2)O(3)-blasted Ti surfaces. This may be related to the fact that SiC-blasted surfaces adsorbed higher amounts of fibronectin due to their higher surface free energy and therefore provided a higher number of specific cell-binding sites. Fn-coated Ti surfaces decreased α(5) mRNA gene expression, by favoring the formation of other integrins involved in adhesion over α(5)β(1). The changes in α(5) mRNA expression induced by the presence of fibronectin coatings may moreover influence the osteoblast differentiation pathway, as fibronectin coatings on Ti surfaces also decreased both ALP mRNA expression and ALP activity after 14 and 21 days of cell culture.

Label-Free Biosensors for Cell Biology

Label-free biosensors for studying cell biology have finally come of age. Recent developments have advanced the biosensors from low throughput and high maintenance research tools to high throughput and low maintenance screening platforms. In parallel, the biosensors have evolved from an analytical tool solely for molecular interaction analysis to powerful platforms for studying cell biology at the whole cell level. This paper presents historical development, detection principles, and applications in cell biology of label-free biosensors. Future perspectives are also discussed.

Cell interaction with nanopatterned surface of implants

Metals such as titanium and alloys are commonly used for manufacturing orthopedic and dental implants because their surface properties provide a biocompatible interface with peri-implant tissues. Strategies for modifying the nature of this interface frequently involve changes to the surface at the nanometer level, thereby affecting protein adsorption, cell-substrate interactions and tissue development. Recent methods to control these biological interactions at the nanometer scale on the surface of implants are reviewed. Future strategies to control peri-implant tissue healing are also discussed.

Relative influence of surface topography and surface chemistry on cell response to bone implant materials. Part 2: Biological aspects

A current medical challenge is the replacement of tissue which can be thought of in terms of bone tissue engineering approaches. The key problem in bone tissue engineering lies in associating bone stem cells with material supports or scaffolds that can be implanted in a patient. Beside bone tissue engineering approaches, these types of materials are used daily in orthopaedics and dental practice as permanent or transitory implants such as ceramic bone filling materials or metallic prostheses. Consequently, it is essential to better understand how bone cells interact with materials. For several years, the current authors and others have developed in vitro studies in order to elucidate the mechanisms underlying the response of human bone cells to implant surfaces. This paper reviews the current state of knowledge and proposes future directions for research in this domain.

Statistical approach of chemistry and topography effect on human osteoblast adhesion

Our objective in this work was to determine statistically the relative influence of surface topography and surface chemistry of metallic substrates on long-term adhesion of human bone cell quantified by the adhesion power (AP). Pure titanium, titanium alloy, and stainless steel substrates were processed with electro-erosion, sandblasting, or polishing giving various morphologies and amplitudes. The surface chemistry was characterized by X-ray photoelectron spectroscopy (XPS) associated with an extensive analysis of surface topography. The statistical analysis demonstrated that the effect on AP of the material composition was not significant. More, no correlation was found between AP and the surface element concentrations determined by XPS demonstrating that the surface chemistry was not an influencing parameter for long-term adhesion. In the same way, the roughness amplitude, independently of the process, had no influence on AP, meaning that roughness amplitude is not an intrinsic parameter of long-term adhesion. On the contrary, the elaboration process alone had a significant effect on AP. For a same surface elaboration process, the number of inflexion points, or G parameter, was the most pertinent roughness parameter for describing the topography influence on long-term adhesion. Thus, more the inflexion points, more the discontinuities, higher the long-term adhesion.

Design of novel three-phase PCL/TZ-HA biomaterials for use in bone regeneration applications

The design of bioactive scaffold materials able to guide cellular processes involved in new-tissue genesis is key determinant in bone tissue engineering. The aim of this study was the design and characterization of novel multi-phase biomaterials to be processed for the fabrication of 3D porous scaffolds able to provide a temporary biocompatible substrate for mesenchymal stem cells (MSCs) adhesion, proliferation and osteogenic differentiation. The biomaterials were prepared by blending poly(epsilon-caprolactone) (PCL) with thermoplastic zein (TZ), a thermoplastic material obtained by de novo thermoplasticization of zein. Furthermore, to bioactivate the scaffolds, microparticles of osteoconductive hydroxyapatite (HA) were dispersed within the organic phases. Results demonstrated that materials and formulations strongly affected the micro-structural properties and hydrophilicity of the scaffolds and, therefore, had a pivotal role in guiding cell/scaffold interaction. In particular, if compared to neat PCL, PCL-HA composite and PCL/TZ blend, the three-phase PCL/TZ-HA showed improved MSCs adhesion, proliferation and osteogenic differentiation capability, thus demonstrating potential for bone regeneration.

Effect of Surface Wettability and Topography on the Adhesion of Osteosarcoma Cells on Plasma-modified Polystyrene

Biomaterials interact with the biological environment at their surface, making accurate biophysical characterization of the surface crucially important for understanding subsequent biological effects. In this study, the surface of polystyrene (PS) was systematically altered in order to determine the effect of plasma treatment and surface roughness on cell adhesion and spreading. Surfaces with water contact angle from hydrophilic (12°) to superhydrophobic (155°) were obtained through a combination of modifying surface roughness ( Ra), the deposition of siloxane coatings and the fluorination of the PS surface. Ra values in the range of 19—2365 nm were obtained by grinding the PS surface. The nanometer-thick siloxane coatings were deposited using an atmospheric pressure plasma system, while the fluorination of the PS was carried out using a low-pressure radio frequency (RF) plasma. The siloxane coatings were obtained using a liquid poly(dimethylsiloxane) precursor that was nebulized into helium or helium/oxygen plasmas. Water contact angles in the range of 12—122° were obtained with these coatings. Cell adhesion studies were carried out using human MG63 osteosarcoma cells. It was observed that higher polymer surface roughness enhanced cell adhesion, but had a negative effect on cell spreading. Optimum cell adhesion was observed at ∼64° for the siloxane coatings, with a decrease in adhesion observed for the more hydrophilic and hydrophobic coatings. This decrease in cell adhesion with an increase in hydrophobicity was also observed for the fluorinated PS surfaces with water contact angles in the range of 110—155°.