One-step fabrication of high-performance graphene composites from graphite solution for bio-scaffolds and flexible strain sensors.

Graphene composites possess great application potential in various fields including flexible electrodes, wearable sensors and biomedical devices owing to their excellent mechanical and electrical properties. However, it remains challenging to fabricate graphene composites-based devices with high consistency due to the gradual aggression effect of graphene during fabrication process. Herein, we propose a method for one-step fabricating graphene/polymer composite-based devices from graphite/polymer solution by using electrohydrodynamic (EHD) printing with the Weissenberg effect (EPWE). Taylor-Couette flows with high shearing speed were generated to exfoliate high-quality graphene with a rotating steel microneedle coaxially set in a spinneret tube. The effects of the rotating speed of the needle, spinneret size and precursor ingredients on the graphene concentration were discussed. As a proof of concept, EPWE was used to successfully fabricate graphene/polycaprolactone (PCL) bio-scaffolds with good biocompatibility and graphene/thermoplastic polyurethane strain sensor for detecting human motions with a maximum gauge factor more than 2400 from 40% to 50% strain. As such, this method sheds a new light on one-stepin situfabrication of graphene/polymer composite-based devices from graphite solution with low cost.

Developing a reliable and valid competency model for assistant dentists in China.

BACKGROUND: The shortage of dentists is one of the various medical-resource problems found around the world. More and more countries are improving the provision of oral services by training dental therapists and hygienists. In China, they are called assistant dentists, and they supplement dental services, but thus far, no research has been conducted on the competence of this group. OBJECTIVE: The purpose of this study was to establish a competency model for Chinese assistant dentists. This model can provide a more scientific basis for the education, training, and evaluation of these professionals, as well as provide a reference for the capacity of dental therapists in various countries. METHODS: We established a system of competency characteristics using theoretical analysis and focus group discussions, after which we established an initial competency model by consulting a Delphi panel of 29 experts. Finally, we collected data from 1389 assistant dentists from 14 provinces in China, and the reliability and validity of the model were confirmed by factor analysis of this data. RESULTS: After three rounds of Delphi panels, the competency model came to include seven ability levels and 50 indicators. In exploratory-factor analysis, three indicators were eliminated, and the questionnaire could explain 68.41 % of total variance. In confirmatory-factor analysis, the established model and data fit well (goodness-of-fit index [GFI] = 0.914, root mean square error of approximation [RMSEA] = 0.047). The results showed that the entire model has good reliability and validity. CONCLUSIONS: Our competency model for dental assistants in China includes seven elements. This is consistent with the current health situation in China, and it has distinct Chinese characteristics. Some of our findings, like those reported in other countries with dental therapists, offer ideas for other developing countries.

Effect of graphene-oxide-modified osteon-like concentric microgrooved surface on the osteoclastic differentiation of macrophages.

OBJECTIVES: This study aimed to investigate the effect of new biomimetic micro/nano surfaces on the osteoclastic differentiation of RAW264.7 macrophages by simulating natural osteons for the design of concentric circular structures and modifying graphene oxide (GO). METHODS: The groups were divided into smooth titanium surface group (SS), concentric microgrooved titanium surface group (CMS), and microgroove modified with GO group (GO-CMS). The physicochemical properties of the material surfaces were studied using scanning electron microscopy (SEM), contact-angle measurement, atomic force microscopy, X-ray photoelectron spectroscopy analysis, and Raman spectroscopy. The effect of the modified material surface on the cell biological behavior of RAW264.7 was investigated by cell-activity assay, SEM, and laser confocal microscopy. The effect on the osteoclastic differentiation of macrophages was investiga-ted by tartrate-resistant acid phosphatase (TRAP) immunofluorescence staining and quantitative real-time polymerase chain reaction (qRT-PCR) experiments. RESULTS: Macrophages were arranged in concentric circles along the microgrooves, and after modification with GO, the oxygen-containing groups on the surface of the material increased and hydrophilicity increased. Osteoclasts in the GO-CMS group were small in size and number and had the lowest TRAP expression. Although it promoted the proliferation of macrophages in the GO-CMS group, the expression of osteoclastic differentiation-related genes was lower than that in the SS group, and the difference was statistically significant (P<0.05). CONCLUSIONS: Concentric circular microgrooves restricted the fusion of osteoclasts and the formation of sealing zones. Osteomimetic concentric microgrooves modified with GO inhibited the osteoclastic differentiation of RAW 264.7 macrophages.

Graphene Oxide-Modified Concentric Microgrooved Titanium Surfaces for the Dual Effects of Osteogenesis and Antiosteoclastogenesis.

Surface modification is an effective method to resolve the biocompatibility, mechanical, and functional issues of various titanium implant materials. Therefore, many researchers have modified the implant surface to promote the osseointegration of the implant and improve the implant survival rate. In this study, we used photolithography to construct concentric microgrooves with widths of 10 µm and depths of 10 µm, to produce an osteon-mimetic concentric microgrooved titanium surface that was further modified with graphene oxide by silanization (GO-CMS). The modified surface had great biocompatibility and promoted the proliferation of bone marrow-derived mesenchymal stem cells (BMSCs) and RAW264.7 macrophages. The concentric microgrooves on the titanium surface guided cell migration, altered actin cytoskeleton, and caused the cells to arrange in concentric circles. The titanium surface of the GO-modified osteon-mimetic concentric microgrooves promoted the osteogenic differentiation of BMSCs and inhibited the osteoclastogenic differentiation of RAW264.7 cells. Subsequently, we constructed an indirect coculture system and found that RAW264.7 cells cultured on a GO-CMS material surface in a BMSC-conditioned medium (BCM) decreased receptor activator of nuclear factor-κB ligand (RANKL) secretion and increased OPG secretion and also that the BCM inhibited osteoclastogenic differentiation. Additionally, the secretion of OSM increased in BMSCs cultured in RAW264.7-conditioned medium (RCM) in the GO-CMS group, which in turn promoted the osteogenic differentiation of BMSCs. In conclusion, the titanium surface of GO-modified osteon-mimetic concentric microgrooves had dual effects of osteogenesis and antiosteoclastogenesis under single and coculture conditions, which is beneficial for implant osseointegration and is a promising method for the future direction of surface modifications of implants.

Biofunctionalization of Microgroove Surfaces with Antibacterial Nanocoatings.

OBJECTIVES: To investigate the physical properties of the modified microgroove (MG) and antibacterial nanocoated surfaces. In addition, the biological interactions of the modified surfaces with human gingival fibroblasts (HGFs) and the antibacterial activity of the surfaces against Porphyromonas gingivalis were studied. METHODS: The titanium nitride (TiN) and silver (Ag) coatings were deposited onto the smooth and MG surfaces using magnetron sputtering. A smooth titanium surface (Ti-S) was used as the control. The physicochemical properties including surface morphology, roughness, and hydrophilicity were characterized using scanning electron microscopy, atomic force microscopy, and an optical contact angle analyzer. The "contact guidance" morphology was assessed using confocal laser scanning microscopy. Cell proliferation was analyzed using the Cell Counting Kit-8 assay. The expression level of the main focal adhesion-related structural protein vinculin was compared using quantitative reverse transcription PCR and Western blotting. The antibacterial activity against P. gingivalis was evaluated using the LIVE/DEAD BacLight™ Bacterial Viability Kit. RESULTS: The Ag and TiN antibacterial nanocoatings were successfully deposited onto the smooth and MG surfaces using magnetron sputtering technology. TiN coating on a grooved surface (TiN-MG) resulted in less nanoroughness and greater surface hydrophilicity than Ag coating on a smooth surface (Ag-S), which was more hydrophobic. Cell proliferation and expression of vinculin were higher on the TiN-MG surface than on the Ag-coated surfaces. Ag-coated surfaces showed the strongest antibacterial activity, followed by TiN-coated surfaces. CONCLUSION: Nano-Ag coating resulted in good antimicrobial activity; however, the biocompatibility was questionable. TiN nanocoating on an MG surface showed antibacterial properties with an optimal biocompatibility and maintained the "contact guidance" effects for HGFs.

[Comparative study on contact guidance activity of human gingival fibroblasts on microgroove surfaces].

OBJECTIVE: To compared the difference in contact guidance activity among microgroove surfaces with different sizes of human gingival fibroblast (HGF), with the hope of providing basis for size selection of microgroove for transmucosal part of dental implant. METHODS: Basing on the size of HGF, microgroove titanium surfaces were fabricated by photolithography with parallel grooves: 15, 30 or 60 µm in width and 5 or 10 µm in depth. The groups that used different microgroove surfaces were denoted as T15/5, T15/10, T30/5, T30/10, T60/5, and T60/10. Group T0 (the control meanwhile was a sputter of titanium on a simple planar silicon substrate). The morphology that HGF arranged along the groove was analyzed by immunofluorescence staining. Difference in contact guidance activity was quantitatively compared basing on the consistency of nucleus arrangement and deformation ratio. RESULTS: Microgroove groups had significantly higher consistency of nucleus arrangement and deformation ratio compared to the control group, with T60/10 had the highest consistency of 0.937±0.024, and T15/5 had the lowest consistency of 0.660±0.016 and T60/10 had the highest deformation ratio of 3.555±0.205, and T15/5 had the lowest deformation ratio of 1.819±0.011. CONCLUSIONS: Microgroove surfaces of all the different sizes show contact guidance activity on HGF, and the contact guidance activity increases with the increase of width and depth.

[Effects of morphology of the microgroove titanium surface on expression of vinculin in human gingival fibroblasts].

PURPOSE: To investigate the effects of morphology of the microgroove surface on the expression of vinculin in human gingival fibroblasts, with the hope of providing basis for size selection of microgroove for transmucosal part of dental implants. METHODS: Microgroove titanium surfaces were fabricated by photolithography with parallel grooves: 15 µm, 30 µm or 60 µm in width and 5 µm or 10 µm in depth. The groups that used different microgroove surfaces were denoted as T15/5, T15/10, T30/5, T30/10, T60/5, and T60/10. Smooth titanium surfaces (T0) were used as controls. Surface topography was detected. HGFs were cultured on the microgroove surfaces. Morphology of vinculin was analyzed using CLSM. Expression level of vinculin was compared among different groups by real-time PCR and Western blotting. SPSS17.0 software package was used for statistical analysis. RESTULTS: Immunofluorescence staining revealed increase of green vinculin fluorescent spots as the increase of microgroove width, while T60 group had the highest mRNA and protein expression and T15 group had the lowest. Microgroove depth had no effect on the expression of vinculin under the same width. CONCLUSIONS: Morphology of microgroove surface has effect on the expression of vinculin, and the morphology of microgroove surface in T60 group is the best size for the transmucosal part in terms of expression of vinculin protein expression.

Increased Mesenchymal Stem Cell Response and Decreased Staphylococcus aureus Adhesion on Titania Nanotubes without Pharmaceuticals.

Titanium (Ti) implants with enhanced biocompatibility and antibacterial property are highly desirable and characterized by improved success rates. In this study, titania nanotubes (TNTs) with various tube diameters were fabricated on Ti surfaces through electrochemical anodization at 10, 30, and 60 V (denoted as NT10, NT30, and NT60, resp.). Ti was also investigated and used as a control. NT10 with a diameter of 30 nm could promote the adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs) without noticeable differentiation. NT30 with a diameter of 100 nm could support the adhesion and proliferation of BMSCs and induce osteogenesis. NT60 with a diameter of 200 nm demonstrated the best ability to promote cell spreading and osteogenic differentiation; however, it clearly impaired cell adhesion and proliferation. As the tube diameter increased, bacterial adhesion on the TNTs decreased and reached the lowest value on NT60. Therefore, NT30 without pharmaceuticals could be used to increase mesenchymal stem cell response and decrease Staphylococcus aureus adhesion and thus should be further studied for improving the efficacy of Ti-based orthopedic implants.

Antibacterial Effects and Biocompatibility of Titania Nanotubes with Octenidine Dihydrochloride/Poly(lactic-co-glycolic acid).

Titanium (Ti) implants with long-term antibacterial ability and good biocompatibility are highly desirable materials that can be used to prevent implant-associated infections. In this study, titania nanotubes (TNTs) were synthesized on Ti surfaces through electrochemical anodization. Octenidine dihydrochloride (OCT)/poly(lactic-co-glycolic acid) (PLGA) was infiltrated into TNTs using a simple solvent-casting technique. OCT/PLGA-TNTs demonstrated sustained drug release and maintained the characteristic hollow structures of TNTs. TNTs (200 nm in diameter) alone exhibited slight antibacterial effect and good osteogenic activity but also evidently impaired adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs). OCT/PLGA-TNTs (100 nm in diameter) supported BMSC adhesion and proliferation and showed good osteogenesis-inducing ability. OCT/PLGA-TNTs also exhibited good long-term antibacterial ability within the observation period of 7 d. The synthesized drug carrier with relatively long-term antibacterial ability and enhanced excellent biocompatibility demonstrated significant potential in bone implant applications.

Biofunctionalization of microgroove titanium surfaces with an antimicrobial peptide to enhance their bactericidal activity and cytocompatibility.

A firm peri-implant soft tissue seal is important for the long-term survival of dental implants, which demands the properties of antibacterial and cytocompatibility of the implant surfaces. In this study, GL13K, a cationic antimicrobial peptide, was immobilized onto microgroove surfaces which were 60 µm in width and 10 µm in depth, and the modified surfaces improved both the properties of antibacterial and cytocompatibility. The method of silanization was used to immobilize the antimicrobial peptide GL13K, which was confirmed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle measurement. Then the mechanical stability of the coatings was confirmed by ultrasonication. In vitro antibacterial tests confirmed bactericidal activity against Porphyromonas gingivalis without inhibiting its adhesion. In vitro cytocompatibility tests also confirmed that adhesion at later phase and proliferation of HGFs were greater (P<0.01) on the GL13K-modified microgroove surfaces than on the non-treated microgroove surfaces, and both of them were greater than on the smooth surfaces. The phenomenon of the contact guidance, which is cell growth aligned along the microgrooves, was maintained. Overall, this study developed a promising bi-functional surface that combined the physical and chemical properties to promote cytocompatibility and antibacterial activity simultaneously.

Proteomic analysis of the effect of extracellular calcium ions on human mesenchymal stem cells: Implications for bone tissue engineering.

Human mesenchymal stem cells-bone marrow (BM-hMSCs) are considered as the most suitable seed cells for bone tissue engineering. Calcium ions (Ca(2+)) forms an important component of a number of commercial bone substitutes and support materials. For efficient bone tissue engineering, it is crucial to explore the effect of extracellular Ca(2+) on the growth and differentiation of BM-hMSCs, and to understand their molecular mechanisms. Therefore, in the present study, BM-hMSCs were cultivated in serum free growth medium or serum free growth medium with additional 4 or 6mM Ca(2+) for 3weeks, following which, the proliferation and osteoblastic differentiation of these cells were evaluated. Differentially expressed proteins were established using iTRAQ labeling coupled with nano-LC-MS/MS. Our data revealed that Ca(2+) significantly promoted the proliferation of BM-hMSCs in the early stage. Furthermore, Ca(2+) showed osteoinduction properties. MAPKs signaling pathway might participate in the osteogenic differentiation of BM-hMSCs caused by Ca(2+). Certain newly found proteins could be potentially important for the osteogenic differentiation of BM-hMSCs and may be associated with osteogenesis.

Effect of 3D microgroove surface topography on plasma and cellular fibronectin of human gingival fibroblasts.

OBJECTIVES: Fibronectin (FN), an extracellular matrix (ECM) glycoprotein, is a key factor in the compatibility of dental implant materials. Our objective was to determine the optimal dimensions of microgrooves in the transmucosal part of a dental implant, for optimal absorption of plasma FN and expression of cellular FN by human gingival fibroblasts (HGFs). METHODS: Microgroove titanium surfaces were fabricated by photolithography with parallel grooves: 15µm, 30µm, or 60µm in width and 5µm or 10µm in depth. Smooth titanium surfaces were used as controls. Surface hydrophilicity, plasma FN adsorption and cellular FN expression by HGFs were measured for both microgroove and control samples. RESULTS: We found that narrower and deeper microgrooves amplified surface hydrophobicity. A 15-µm wide microgroove was the most hydrophobic surface and a 60-µm wide microgroove was the most hydrophilic. The latter had more expression of cellular FN than any other surface, but less absorption of plasma FN than 15-µm wide microgrooves. Variation in microgroove depth did not appear to effect FN absorption or expression unless the groove was narrow (∼15 or 30µm). In those instances, the shallower depths resulted in greater expression of cellular FN. CONCLUSIONS: Our microgrooves improved expression of cellular FN, which functionally compensated for plasma FN. A microgroove width of 60µm and depth of 5 or 10µm appears to be optimal for the transmucosal part of the dental implant.