Effects of adhesion molecules on the behavior of osteoblast-like cells and normal human fibroblasts on different titanium surfaces

Protein absorption on titanium surfaces treated with a high-power laser: A systematic review

STATEMENT OF PROBLEM

The surface of titanium dental implants treated with a high-power laser has been reported to favor osseointegration, mainly by altering protein uptake. Despite the large number of articles that address the topic, the heterogeneity of methodologies and results makes an understanding of the treatment's benefits difficult, and a systematic review is needed.

PURPOSE

The purpose of this systematic review was to further the knowledge on protein uptake on titanium surfaces that have undergone treatment with a high-power laser.

MATERIAL AND METHODS

This review followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines and was registered with the Open Science Framework (OSF) (osf.io/gcbna). Searches were performed in PubMed, Scopus, Web of Science, Embase, and Google Scholar databases. The articles were selected in 2 steps by 2 independent reviewers according to the previously selected eligibility criteria. The risk of bias was analyzed by using the Joanna Briggs Institute (JBI)-adapted quasi-experimental study evaluation tool.

RESULTS

The studies addressed have shown that applying a high-power laser to the implant surface, depending on its settings, generates topographical changes that can optimize the protein absorption process and thus accelerate the other biological processes.

CONCLUSIONS

The studies identified in this systematic review showed that surface treatment with a high-power laser represents a promising technique with a positive influence on protein uptake and osseointegration.

Synergistic Enhancement of Protein Recruitment and Retention via Implant Surface Microtopography and Superhydrophilicity in a Computational Fluid Dynamics Model

The exact mechanisms by which implant surface properties govern osseointegration are incompletely understood. To gain insights into this process, we examined alterations in protein and blood recruitment around screw implants with different surface topographies and wettability using a computational fluid dynamics (CFD) model. Compared with a smooth surface, a microrough implant surface reduced protein infiltration from the outer zone to the implant thread and interface zones by over two-fold. However, the microrough implant surface slowed blood flow in the interface zone by four-fold. As a result, compared with the smooth surface, the microrough surface doubled the protein recruitment/retention index, defined as the mass of proteins present in the area per unit time. Converting implant surfaces from hydrophobic to superhydrophilic increased the mass of protein infiltration 2-3 times and slowed down blood flow by up to two-fold in the implant vicinity for both smooth and microrough surfaces. The protein recruitment/retention index was highest at the implant interface when the implant surface was superhydrophilic and microrough. Thus, this study demonstrates distinct control of the mass and speed of protein and blood flow through implant surface topography, wettability, and their combination, significantly altering the efficiency of protein recruitment. Although microrough surfaces showed both positive and negative impacts on protein recruitment over smooth surfaces, superhydrophilicity was consistently positive regardless of surface topography.

Comparison of Osseointegration in Novel Laser-Textured and SLA Implants

Background

Osseointegration is defined as the direct structural and functional connection between neo-formed bone and dental implants. Among the parameters suggested to predominantly influencing the establishment of a successful osseointegration is the quality of the implant surface, which may enhance the strength and speed of this biomechanical process.

Objective

The purpose of this study was to evaluate the ability of a novel laser-treated surface, compared to sandblasted, large-grit, acid-etched (SLA) surfaces, to enhance and accelerate implant integration in delayed implant placement.Methods: Thirty patients with two missing posterior teeth were enrolled in this study. Each patient received, at a randomly allocated site, an implant with a conventional SLA surface, and at a second site, an implant with laser-textured surface. A total of 60 tissue-level implants were subsequently placed. Implant stability (ISQ) was measured using resonance frequency analysis (RFA). ISQ was assessed at baseline (T0), 8 weeks (T1), and 12 weeks (T2) following implant placement. Results: There was a statistical difference in implant stability between laser-textured and SLA group at 12 weeks postoperatively. Implant stabilization showed a successful osseointegration with both surface types.

Conclusion

Both laser and SLA surface treatments had positive impacts on implant stabilization following delayed placement. Laser-treated surfaces presented higher values of osseointegration at 3 months postoperatively.

Mechanical removal of biofilm on titanium discs: An in vitro study

The objective of this in vitro study was to evaluate surface cleanness and cytocompatibility following mechanical instrumentation of biofilm-contaminated titanium surfaces. Titanium discs (non-modified [Ti(s)] and shot-blasted surfaces [Ti(r)]) contaminated with Streptococcus gordonii were instrumented using four different techniques: (i) gauze soaked in saline (GS), (ii) ultra-sonic device (US), (iii) rotating nickel-titanium brush (TiB), or (iv) air-polishing device (AP). Non-contaminated, untreated titanium disks were used as controls (C). Residual deposits and cytocompatibility for osteoblast-like cells were evaluated using scanning electron microscopy, immunofluorescence, and reverse transcriptase polymerase chain reaction. While the number of residual bacteria on Ti(s) discs was close to 0 in all treatment groups, significantly higher mean numbers of residual bacteria were observed on Ti(r) discs for GS (152.7 ± 75.7) and TiB (33.5 ± 22.2) than for US (0) and AP (0). Instrumentation with US resulted in deposition of foreign material (mean area% of foreign material: 3.0 ± 3.6% and 10.8 ± 9.6% for Ti(s) and Ti(r) discs, respectively). AP was the most effective decontamination procedure in reducing bacteria without depositing residual foreign material on Ti(r) discs. TiB and AP were superior methods in restoring cytocompatibility, although no method of mechanical decontamination resulted in pristine levels of cytocompatibility.

The Role of Instrumentation in the Healing Process of Spinal Tuberculosis: An Experimental Study

Introduction: Tuberculosis is still commonly found in many developing countries. Spinal tuberculosis can cause vertebral deformity and neurological disorders. It was discovered thousands years ago and its management was aimed to eradicate infection and maintain the integrity of the vertebrae. Previously, the management of spinal TB was using drugs and external stabilization. Surgical techniques were developed afterwards to clean the infected vertebral segment. Because of the vertebral deformity remained inevitable and had impacts on neurological disorders, new paradigm had been developed by using instrumentation to stabilize the deformity of infected vertebral segment and to restore and maintain neurological function. TGF-β has a major role in angiogenesis in bone healing process. Spinal TB instrumentation uses metal devices composed of ions and particles that can interact each other so it could produce physical and chemical energy that is transmitted to the vertebrae. The energy is expected to enhance the biomolecular and biocellular activity of the body's immune cells so the healing process could be better. Methods: An experimental study was carried out on New Zealand Rabbits which were given TB H37Rv strain infection in the vertebral body. Samples were divided into five groups namely control rabbits, infected rabbits without intervention, infected rabbits treated by instrumentation, infected rabbits given anti-tuberculosis drugs and infected rabbits treated by instrumentation and given drugs. Then the cytokine levels of TGF-β were evaluated and compared. Results: The results showed a significant TGF- β level increase in infected rabbits given drugs alone and instrumentation alone compared to infected rabbits without intervention. There was a significant TGF- β increase in infected rabbits given drugs and treated by instrumentation compared to control rabbits and rabbits who received drugs only. Conclusions: Instrumentation can improve the healing process in spinal tuberculosis by increasing the body's cytokine levels.

Induced Biological Response in Contact with Ag-and Cu-Doped Carbon Coatings for Potential Orthopedic Applications

Silver and copper as additives of various biomaterials have been reported as the potential solutions for biomedicine applications, mostly because of inducing bactericidal effects. The application of those admixtures in diamond-like carbon (DLC) coatings may be desirable for orthopedic implants. In the present manuscript, the biological effect of coatings with up to about 7 at.% and 14 at.% of, respectively, Cu and Ag is compared. The morphology, chemical structure, and composition of films deposited on AISI 316LVM and Ti6Al7Nb is characterized. The live/dead analysis conducted with Escherichia coli shows a higher bactericidal potential of silver than copper. Although the Cu-doped coatings can positively affect the proliferation of Saos-2 and EA.hy926 cell lines, the results of XTT test are on the verge of 70% of viability. Biological effect of silver on EA.hy926 cell lines is negative but that admixture ensures high proliferation of osteoblasts in contact with coatings deposited on titanium alloy (over 20% better than for substrate material). In that case, the viability is reaching about 85% for Ag-doped coatings on AISI 316LVM and 75% on Ti6Al7Nb. The results indicate that for the sake of bactericidal coatings that may promote osteointegration, the candidates are DLC with silver content no higher than 10 at.%.

Reliability of new poly (lactic-co-glycolic acid) membranes treated with oxygen plasma plus silicon dioxide layers for pre-prosthetic guided bone regeneration processes

BACKGROUND

The use of cold plasmas may improve the surface roughness of poly(lactic-co-glycolic) acid (PLGA) membranes, which may stimulate the adhesion of osteogenic mediators and cells, thus accelerating the biodegradation of the barriers. Moreover, the incorporation of metallic-oxide particles to the surface of these membranes may enhance their osteoinductive capacity. Therefore, the aim of this paper was to evaluate the reliability of a new PLGA membrane after being treated with oxygen plasma (PO2) plus silicon dioxide (SiO2) layers for guided bone regeneration (GBR) processes.

MATERIAL AND METHODS

Circumferential bone defects (diameter: 11 mm; depth: 3 mm) were created on the top of eight experimentation rabbits' skulls and were randomly covered with: (1) PLGA membranes (control), or (2) PLGA/PO2/SiO2 barriers. The animals were euthanized two months afterwards. A micromorphologic study was then performed using ROI (region of interest) colour analysis. Percentage of new bone formation, length of mineralised bone, concentration of osteoclasts, and intensity of ostheosynthetic activity were assessed and compared with those of the original bone tissue. The Kruskal-Wallis test was applied for between-group com Asignificance level of a=0.05 was considered.

RESULTS

The PLGA/PO2/SiO2 membranes achieved the significantly highest new bone formation, length of mineralised bone, concentration of osteoclasts, and ostheosynthetic activity. The percentage of regenerated bone supplied by the new membranes was similar to that of the original bone tissue. Unlike what happened in the control group, PLGA/PO2/SiO2 membranes predominantly showed bone layers in advanced stages of formation.

CONCLUSIONS

The addition of SiO2 layers to PLGA membranes pre-treated with PO2 improves their bone-regeneration potential. Although further research is necessary to corroborate these conclusions in humans, this could be a promising strategy to rebuild the bone architecture prior to rehabilitate edentulous areas.

In vivo comparative model of oxygen plasma and nanocomposite particles on PLGA membranes for guided bone regeneration processes to be applied in pre-prosthetic surgery: a pilot study

OBJECTIVES

To evaluate the bone regeneration potential of a new membrane fabricated with polyglycolide acid (PLGA) after being treated with oxygen plasma (PO2), and/or being functionalized with silicon dioxide (SiO2) or titanium dioxide (TiO2) nanoparticles.

METHODS

Bone defects (5 mm 3 mm) were produced on the top of 3 experimentation rabbits’ skulls and were covered with variously modified PLGA scaffolds. After the animals were sacrificed, neoformed bone (%), mineralized bone (mm), bone resorption (%), osteoclasts/mm2, and intensity of osteosynthetic activity, were assessed under microscope.

RESULTS

The following groups were formed depending on the type of membrane: PLGA (control); PLGA/PO2; PLGA/SiO2; PLGA/TiO2; PLGA/PO2/SiO2; and PLGA/PO2/TiO2. The histological sections showed bone layers in advanced stages of formation. The highest percentages of neoformed bone corresponded to PLGA/PO2/SiO2 membranes (59.07%; p = 0.31) followed by PLGA/PO2 barriers (50.27%). The controls showed the lowest mineralization (13.89 mm; p = 0.24). PLGA/TiO2 scaffolds exhibited the least bone resorption (4.45%; p = 0.77) and osteoclasts/ mm2 (1.58; p = 0.86). PLGA/SiO2 and PLGA/TiO2 membranes stimulated the maximum osteosynthetic activity.

CONCLUSIONS

The treatment of PLGA barriers with PO2 increased bone regeneration in rabbits. When comparing the effect of PO2/SiO2 and PO2/TiO2, higher percentages of neoformed bone were encountered after silicon-dioxide coating.

CLINICAL SIGNIFICANCE

The incorporation of SiO2 nanoparticles onto PO2-treated PLGA membranes was the most promising technique out of those investigated to promote bone formation in rabbits. The addition of SiO2 or TiO2 layers to PLGA substrates may stimulate the osteosynthetic activity, which might be useful to restore bone dimensions in preparation for naturally appearing dental prostheses.

The effect of different collagen modifications for titanium and titanium nitrite surfaces on functions of gingival fibroblasts

OBJECTIVES

Targeted modifications of the bulk implant surfaces using bioactive agents provide a promising tool for improvement of the long-term bony and soft tissue integration of dental implants. In this study, we assessed the cellular responses of primary human gingival fibroblasts (HGF) to different surface modifications of titanium (Ti) and titanium nitride (TiN) alloys with type I collagen or cyclic-RGDfK-peptide in order to define a modification improving long-term implants in dental medicine.

MATERIALS AND METHODS

Employing Ti and TiN implants, we compared the performance of simple dip coating and anodic immobilization of type I collagen that provided collagen layers of two different thicknesses. HGF were seeded on the different coated implants, and adhesion, proliferation, and gene expression were analyzed.

RESULTS

Although there were no strong differences in initial cell adhesion between the groups at 2 and 4 hours, we found that all surface modifications induced higher proliferation rates as compared to the unmodified controls. Consistently, gene expression levels of cell adhesion markers (focal adhesion kinase (FAK), integrin beta1, and vinculin), cell differentiation markers (FGFR1, TGFb-R1), extracellular protein markers (type I collagen, vimentin), and cytoskeletal protein marker aktinin-1 were consistently higher in all surface modification groups at two different time points of investigation as compared to the unmodified controls.

CONCLUSION

Our results indicate that simple dip coating of Ti and TiN with collagen is sufficient to induce in vitro cellular responses that are comparable to those of more reliable coating methods like anodic adsorption, chemical cross-linking, or RGD coating. TiN alloys do not possess any positive or adverse effects on HGF.

CLINICAL RELEVANCE

Our results demonstrate a simple, yet effective, method for collagen coating on titanium implants to improve the long term integration and stability of dental implants.

'Pre-prosthetic use of poly(lactic-co-glycolic acid) membranes treated with oxygen plasma and TiO2 nanocomposite particles for guided bone regeneration processes'

OBJECTIVES

Guided bone regeneration (GBR) processes are frequently necessary to achieve appropriate substrates before the restoration of edentulous areas. This study aimed to evaluate the bone regeneration reliability of a new poly-lactic-co-glycolic acid (PLGA) membrane after treatment with oxygen plasma (PO2) and titanium dioxide (TiO2) composite nanoparticles.

METHODS

Circumferential bone defects (diameter: 10mm; depth: 3mm) were created on the parietal bones of eight experimentation rabbits and were randomly covered with control membranes (Group 1: PLGA) or experimental membranes (Group 2: PLGA/PO2/TiO2). The animals were euthanized two months afterwards, and a morphologic study was then performed under microscope using ROI (region of interest) colour analysis. Percentage of new bone formation, length of mineralised bone formed in the grown defects, concentration of osteoclasts, and intensity of osteosynthetic activity were assessed. Comparisons among the groups and with the original bone tissue were made using the Kruskal-Wallis test. The level of significance was set in advance at a=0.05.

RESULTS

The experimental group recorded higher values for new bone formation, mineralised bone length, and osteoclast concentration; this group also registered the highest osteosynthetic activity. Bone layers in advanced formation stages and low proportions of immature tissue were observed in the study group.

CONCLUSIONS

The functionalised membranes showed the best efficacy for bone regeneration.

CLINICAL SIGNIFICANCE

The addition of TiO2 nanoparticles onto PLGA/PO2 membranes for GBR processes may be a promising technique to restore bone dimensions and anatomic contours as a prerequisite to well-supported and natural-appearing prosthetic rehabilitations.

Effects of pico-to-nanometer-thin TiO2 coating on the biological properties of microroughened titanium

The independent, genuine role of surface chemistry in the biological properties of titanium is unknown. Although microtopography has been established as a standard surface feature in osseous titanium implants, unfavorable behavior and reactions of osteogenic cells are still observed on the surfaces. To further enhance the biological properties of microfeatured titanium surfaces, this study tested the hypotheses that (1) the surface chemistry of microroughened titanium surfaces can be controllably varied by coating with a very thin layer of TiO(2), without altering the existing topographical and roughness features; and (2) the change in the surface chemistry affects the biological properties of the titanium substrates. Using a slow-rate sputter deposition of molten TiO(2) nanoparticles, acid-etched microroughened titanium surfaces were coated with a TiO(2) layer of 300-pm to 6.3-nm thickness that increased the surface oxygen levels without altering the existing microtopography. The attachment, spreading behavior, and proliferation of osteoblasts, which are considered to be significantly impaired on microroughened surfaces compared with relatively smooth surfaces, were considerably increased on TiO(2)-coated microroughened surfaces. The rate of osteoblastic differentiation was represented by the increased levels of alkaline phosphatase activity and mineral deposition as well as by the upregulated expression of bone-related genes. These biological effects were exponentially correlated with the thickness of TiO(2) and surface oxygen percentage, implying that even a picometer-thin TiO(2) coating is effective in rapidly increasing the biological property of titanium followed by an additional mild increase or plateau induced by a nanometer-thick coating. These data suggest that a super-thin TiO(2) coating of pico-to-nanometer thickness enhances the biological properties of the proven microroughened titanium surfaces by controllably and exclusively modulating their surface chemistry while preserving the existing surface morphology. The improvements in proliferation and differentiation of osteoblasts attained by this chemical modification is of great significance, providing a new insight into how to develop new implant surfaces for better osseointegration, based on the established microtopographic surfaces.

The effect of a laminin-5-derived peptide coated onto chitin microfibers on re-epithelialization in early-stage wound healing

Considerable effort has been directed towards regenerating defective tissues using tissue-engineering methods. Recently, peptides have been recognized as a valuable scientific tool in the field of tissue-engineering. The PPFLMLLKGSTR motif of the human laminin-5 alpha3 chain has been previously reported to promote keratinocyte survival; however, the in vivo effects of the PPFLMLLKGSTR motif have not yet been studied. These studies raised the hypothesis that a laminin-5-derived peptide can promote wound healing by accelerating re-epithelialization in vivo. To examine this hypothesis, we applied chitin microfibrous matrices coated with the PPFLMLLKGSTR motif in both rat and rabbit full-thickness cutaneous wound models. Compared with vehicle-treated and peptide-treated cutaneous wounds, the application significantly promoted early-stage wound healing by accelerating re-epithelialization, notably reduced inflammatory cell infiltration, and prominently enhanced fibroblast proliferation. These findings support our hypothesis that the PPFLMLLKGSTR motif acts as a very effective wound healing accelerator by enhancing re-epithelialization.

Understanding organic film behavior on alloy and metal oxides

Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides, namely nickel, chromium, molybdenum, manganese, iron, and titanium, were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid, and octadecylsulfonic acid on these substrates were examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy, and matrix-assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation.

Zirconia: Established facts and perspectives for a biomaterial in dental implantology

Currently, zirconia is widely used in biomedical area as a material for prosthetic devices because of its good mechanical and chemical properties. Largely employed in clinical area for total hip replacement, zirconia ceramics (ZrO(2)) are becoming a prevalent biomaterial in dentistry and dental implantology. Although titanium is used in dental implantology currently, there is a trend to develop new ceramic-based implants as an alternative to monolithic titanium. This article reviews the evolution and development of zirconia through data published between 1963 and January 2008 in English language. Articles were identified via a MEDLINE search using the following keywords: zirconia, zirconia/biocompatibility, zirconia/osseointegration, zirconia/periointegration, zirconia/review, and zirconia/bacterial adhesion or colonization. This review of the literature aims at highlighting and discussing zirconia properties in biological systems for their future use in dental implantology. In conclusion, zirconia with its interesting microstructural properties has been confirmed to be a material of choice for the "new generation" of implants, thanks to its biocompatibility, osseoconductivity, tendency to reduce plaque accumulation, and interaction with soft tissues, which leads to periointegration. However, scientific studies are promptly needed to fulfill gaps like long-term clinical evaluations of "all zirconia implants," currently leading to propose an alternative use of "hybrid systems" (i.e., titanium screw with zirconia collar) and also bacterial colonization of zirconia. Moreover, there is a permanent need for consistent information about topography and chemistry of zirconia allowing easier cross-product comparisons of clinical devices.

Coating of polyurethane scaffolds with collagen: comparison of coating and cross-linking techniques

Collagen has been coated successfully onto numerous hydrophilic polymer scaffolds to improve cell adhesion. Due to the hydrophobic nature of thermoplastic polyurethane (TPU), coating with aqueous collagen solution is problematic for such scaffolds. This study facilitated the coating of TPU with collagen and compared cross-linking and coating techniques. Three different cross-linking methods were compared. Both thermal and glutaraldehyde methods showed proof of cross-linking; however glutaraldehyde seemed to be superior to the other methods. The use of human urine as a wetting agent and the chemical glutaraldehyde had no effect on a cytotoxicity test performed by means of a WST-1 assay with a fibroblastic cell line. Three different coating techniques for porous TPU scaffolds were also investigated: ultrasound, pressurized air and injection. Of these, injection performed best. This method facilitated a coating of 100% of the porous scaffolds examined, which was verified by staining, FTIR and SEM.

The effect of superficial chemistry of titanium on osteoblastic function

The surface topography and chemistry of titanium are postulated to be two major factors that affect the osseointegration capacity of titanium implants. However, it is extremely difficult to control one factor without changing the other, which prevents the isolation of the genuine effect of one factor. This study aimed to determine whether surface chemistry of titanium alone affects osteoblastic function. Two different titanium surfaces were prepared by sputter depositioning of titanium (Ti; 99.99% purity) or titanium dioxide (TiO2; 99.99% purity) (50-nm thick for each) onto machined commercially pure titanium disks. Rat bone marrow-derived osteoblastic cells were cultured on each of the two surfaces. TiO2 surface showed 4.4 times higher elemental oxygen concentration and higher water wettability than Ti surface. Scanning electron microscopic and atomic force microscopic examination revealed no differences in surface topography and roughness values between the two surfaces. The cell proliferated more on TiO2 than on Ti by up to 60%. Although the expression of collagen I gene increased more rapidly on TiO2 at early culture stage of day 3, the late stage marker genes for osteoblastic differentiation, including osteopontin and osteocalcin, were not modulated between the two cultures. The alkaline phosphatase positive area and mineralized nodule area were approximately two times larger on TiO2 than on Ti. In conclusion, titanium materials having different superficial chemistry, that is, titanium or titanium dioxide, may exert different biological capacity of osteoblasts; titanium dioxide may induce superior osteoconduction, primarily because of the increased osteoblastic proliferation.

Modification of the titan surface with photoreactive gelatin to regulate cell attachment

Titan (TiO2) was modified with photoreactive gelatin in order to regulate the attachment of cells. Photoreactive gelatin, which was synthesized by the coupling reaction of gelatin with N-(4-azidobenzoyloxy) succinimide, was immobilized onto the n-octadecyltrimethoxysilane (ODS)-TiO2 or TiO2 surface by ultraviolet irradiation both in the absence and presence of a photo mask. In the absence of a photo mask, the modified titan surface was analyzed by measuring water contact angles and X-ray photoelectron spectroscopy (XPS). The result showed that ODS hydrophobilized the titan surface, and that the immobilization of gelatin affected the surface's hydrophilicity. XPS shows that titan was covered with organic material, including ODS and gelatin. With the photo mask in place, micropatterning of the gelatin was performed. This pattern was confirmed by optical microscopy and time-of-flight secondary ion-mass spectroscopy (TOF-SIMS). Monkey COS-7 epithelial cells were cultured on the unpattern- and pattern-immobilized plate. A significantly higher degree of cell attachment was found on the photoreactive gelatin-immobilized regions than on those that were not immobilized. It was concluded that the cellular pattern on titan was regulated by immobilized photoreactive gelatin.

Concave pit-containing scaffold surfaces improve stem cell-derived osteoblast performance and lead to significant bone tissue formation

Background

Scaffold surface features are thought to be important regulators of stem cell performance and endurance in tissue engineering applications, but details about these fundamental aspects of stem cell biology remain largely unclear.

Methodology and Findings

In the present study, smooth clinical-grade lactide-coglyolic acid 85:15 (PLGA) scaffolds were carved as membranes and treated with NMP (N-metil-pyrrolidone) to create controlled subtractive pits or microcavities. Scanning electron and confocal microscopy revealed that the NMP-treated membranes contained: (i) large microcavities of 80–120 µm in diameter and 40–100 µm in depth, which we termed primary; and (ii) smaller microcavities of 10–20 µm in diameter and 3–10 µm in depth located within the primary cavities, which we termed secondary. We asked whether a microcavity-rich scaffold had distinct bone-forming capabilities compared to a smooth one. To do so, mesenchymal stem cells derived from human dental pulp were seeded onto the two types of scaffold and monitored over time for cytoarchitectural characteristics, differentiation status and production of important factors, including bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF). We found that the microcavity-rich scaffold enhanced cell adhesion: the cells created intimate contact with secondary microcavities and were polarized. These cytological responses were not seen with the smooth-surface scaffold. Moreover, cells on the microcavity-rich scaffold released larger amounts of BMP-2 and VEGF into the culture medium and expressed higher alkaline phosphatase activity. When this type of scaffold was transplanted into rats, superior bone formation was elicited compared to cells seeded on the smooth scaffold.

Conclusion

In conclusion, surface microcavities appear to support a more vigorous osteogenic response of stem cells and should be used in the design of therapeutic substrates to improve bone repair and bioengineering applications in the future.

Cell/surface interactions and adhesion on Ti-6Al-4V: Effects of surface texture

This paper presents the results of an experimental study of the effects of surface texture on the interactions between human osteo-sarcoma (HOS) cells and Ti-6Al-4V. These include the Ti-6Al-4V with polished (smooth); Al(2)O(3) blasted (rough); and laser micro-grooved geometries with controlled spacings and depths. Immuno-fluorescence staining of adhesion proteins (actin and vinculin) was used to study the spreading and adhesion of HOS cells in 2 day culture experiments. Quantitative measures of adhesion were also obtained using an enzymatic detachment assay. The results are discussed within the context of existing theories of cell adhesion. The implications of the results are also examined for the design of textured surfaces in biomedical systems.

Scaffold's surface geometry significantly affects human stem cell bone tissue engineering

In this study, we have observed dental pulp stem cells (SBP-DPSCs) performances on different scaffolds, such as PLGA 85:15, hydroxyapatite chips (HA) and titanium. Stem cells were challenged with each engineered surface, either in plane cultures or in a rotating apparatus, for a month. Gingival fibroblasts were used as controls. Results showed that stem cells exerted a different response, depending on the different type of textured surface: in fact, microconcavities significantly affected SBP-DPSC differentiation into osteoblasts, both temporally and quantitatively, with respect to the other textured surfaces. Actually, stem cells challenged with concave surfaces differentiated quicker and showed nuclear polarity, an index of secretion, cellular activity and matrix formation. Moreover, bone-specific proteins were significantly expressed and the obtained bone tissue was of significant thickness. Thus, cells cultured on the concave textured surface had better cell-scaffold interactions and were induced to secrete factors that, due to their autocrine effects, quickly lead to osteodifferentiation, bone tissue formation, and vascularization. The worst cell performance was obtained using convex surfaces, due to the scarce cell proliferation on to the scaffold and the poor matrix secretion. In conclusion, this study stresses that for a suitable and successful bone tissue reconstruction the surface texture is of paramount importance.

Regenerated Silk Fibroin Nanofibers: Water Vapor-Induced Structural Changes and Their Effects on the Behavior of Normal Human Cells

Nanofibrous non-woven matrices were prepared by electrospinning a regenerated silk fibroin (SF) solution, and the structural changes of SF nanofibers treated with water vapor were investigated using time-resolved IR and (13)C CP/MAS NMR spectroscopy. Conformational transitions of SF from random coil to beta-sheet structures were induced by water vapor treatment and were strongly dependent on the treatment time and temperature. Water vapor treatment provided a useful means of stabilizing the SF nanofiber matrices, resulting in the formation of matrices with a decreased solubility in water and increased mechanical strength. The adhesion and spreading of both normal human keratinocytes and fibroblasts onto the SF nanofiber matrices were also investigated, and the water vapor-treated SF nanofiber matrices showed good cellular compatibility, in comparison with traditional methanol-treated ones. This approach to controlling the conformational changes of SF nanofibers by water vapor treatment may be useful in the design and tailoring of novel materials for biomedical applications, including wound dressings and scaffolds for tissue engineering.