Recombinant fibronectin fragment III8-10/polylactic acid hybrid nanofibers enhance the bioactivity of titanium surface.

AIM: To develop a nanofiber (NF)-based biomimetic coating on titanium (Ti) that mimics the complex spatiotemporal organization of the extracellular matrix (ECM). MATERIALS & METHODS: Recombinant cell attachment site (CAS) of fibronectin type III8-10 domain was co-electrospun with polylactic acid (PLA) and covalently bound on polished Ti discs. Osteoblast-like SaOS-2 cells were used to evaluate their complex bioactivity. RESULTS: A significant increase of cell spreading was found on CAS/PLA hybrid NFs, followed by control pure PLA NFs and bare Ti discs. Cell proliferation showed similar trend being about twice higher on CAS/PLA NFs. The significantly increased ALP activity at day 21 indicated an enhanced differentiation of SaOS-2 cells. CONCLUSION: Coating of Ti implants with hybrid CAS/PLA NFs may improve significantly their osseointegration potential.

Towards the cell-instructive bactericidal substrate: exploring the combination of nanotopographical features and integrin selective synthetic ligands.

Engineering the interface between biomaterials and tissues is important to increase implant lifetime and avoid failures and revision surgeries. Permanent devices should enhance attachment and differentiation of stem cells, responsible for injured tissue repair, and simultaneously discourage bacterial colonization; this represents a major challenge. To take first steps towards such a multifunctional surface we propose merging topographical and biochemical cues on the surface of a clinically relevant material such as titanium. In detail, our strategy combines antibacterial nanotopographical features with integrin selective synthetic ligands that can rescue the adhesive capacity of the surfaces and instruct mesenchymal stem cell (MSC) response. To this end, a smooth substrate and two different high aspect ratio topographies have been produced and coated either with an αvß3-selective peptidomimetic, an α5ß1-selective peptidomimetic, or an RGD/PHSRN peptidic molecule. Results showed that antibacterial effects of the substrates could be maintained when tested on pathogenic Pseudomonas aeruginosa. Further, functionalization increased MSC adhesion to the surfaces and the αvß3-selective peptidomimetic-coated nanotopographies promoted osteogenesis. Such a dual physicochemical approach to achieve multifunctional surfaces represents a first step in the design of novel cell-instructive biomaterial surfaces.

Evaluation of bone loss in antibacterial coated dental implants: An experimental study in dogs.

The aim of this study was to evaluate the in vivo effect of antibacterial modified dental implants in the first stages of peri-implantitis. Thirty dental implants were inserted in the mandibular premolar sites of 5 beagle dogs. Sites were randomly assigned to Ti (untreated implants, 10units), Ti_Ag (silver electrodeposition treatment, 10units), and Ti_TSP (silanization treatment, 10units). Coated implants were characterized by scanning electron microscopy, interferometry and X-ray photoelectron spectroscopy. Two months after implant insertion, experimental peri-implantitis was initiated by ligature placement. Ligatures were removed 2months later, and plaque formation was allowed for 2 additional months. Clinical and radiographic analyses were performed during the study. Implant-tissue samples were prepared for micro computed tomography, backscattered scanning electron microscopy, histomorphometric and histological analyses and ion release measurements. X-ray, SEM and histology images showed that vertical bone resorption in treated implants was lower than in the control group (P<0.05). This effect is likely due to the capacity of the treatments to reduce bacteria colonization on the implant surface. Histological analysis suggested an increase of peri-implant bone formation on silanized implants. However, the short post-ligature period was not enough to detect differences in clinical parameters among implant groups. Within the limits of this study, antibacterial surface treatments have a positive effect against bone resorption induced by peri-implantitis.

Anhydride-functional silane immobilized onto titanium surfaces induces osteoblast cell differentiation and reduces bacterial adhesion and biofilm formation.

Bacterial infection in dental implants along with osseointegration failure usually leads to loss of the device. Bioactive molecules with antibacterial properties can be attached to titanium surfaces with anchoring molecules such as silanes, preventing biofilm formation and improving osseointegration. Properties of silanes as molecular binders have been thoroughly studied, but research on the biological effects of these coatings is scarce. The aim of the present study was to determine the in vitro cell response and antibacterial effects of triethoxysilypropyl succinic anhydride (TESPSA) silane anchored on titanium surfaces. X-ray photoelectron spectroscopy confirmed a successful silanization. The silanized surfaces showed no cytotoxic effects. Gene expression analyses of Sarcoma Osteogenic (SaOS-2) osteoblast-like cells cultured on TESPSA silanized surfaces reported a remarkable increase of biochemical markers related to induction of osteoblastic cell differentiation. A manifest decrease of bacterial adhesion and biofilm formation at early stages was observed on treated substrates, while favoring cell adhesion and spreading in bacteria-cell co-cultures. Surfaces treated with TESPSA could enhance a biological sealing on implant surfaces against bacteria colonization of underlying tissues. Furthermore, it can be an effective anchoring platform of biomolecules on titanium surfaces with improved osteoblastic differentiation and antibacterial properties.

Installing multifunctionality on titanium with RGD-decorated polyurethane-polyurea roxithromycin loaded nanoparticles: toward new osseointegrative therapies.

A novel class of polyurethane-polyurea nanoparticles (PUUa NPs) to install multifunctionality on biomaterials is presented. Biofunctionalization of titanium with roxithromycin loaded RGD-decorated PUUa NPs results in an outstanding improvement of osteoblast adhesion and strong suppression of bacterial attachment. This strategy represents a powerful approach to enhance the osseointegration of implant materials.

Antibacterial coatings on titanium surfaces: a comparison study between in vitro single-species and multispecies biofilm.

Dental plaque is a biofilm that causes dental caries, gingivitis, and periodontitis. Most of the studies in antibacterial coatings have been conducted by in vitro single-species biofilm formation, but oral biofilm involves more than 700 different bacterial species that are able to interact. Therefore, new studies are focused on in vitro multispecies biofilm models that mimic in vivo biofilms. The aim of the present work was to study different antibacterial coatings onto titanium surfaces and evaluate the in vitro antimicrobial properties of the surfaces on two different bacterial species and an oral biofilm. The lactate dehydrogenase assay determined that treated samples did not affect fibroblast viability. In addition, the viability of microorganisms on modified samples was evaluated by a LIVE/DEAD BacLight bacterial viability kit. Although a decrease in viable bacteria onto treated samples was obtained, the results showed differences in effectiveness when single-biofilm and oral plaque were tested. It confirms, as we expected, the distinct sensitivities that bacterial strains have. Thus, this multispecies biofilms model holds a great potential to assess antibacterial properties onto samples for dental purposes.

Mimicking bone extracellular matrix: integrin-binding peptidomimetics enhance osteoblast-like cells adhesion, proliferation, and differentiation on titanium.

Interaction between the surface of implants and biological tissues is a key aspect of biomaterials research. Apart from fulfilling the non-toxicity and structural requirements, synthetic materials are asked to direct cell response, offering engineered cues that provide specific instructions to cells. This work explores the functionalization of titanium with integrin-binding peptidomimetics as a novel and powerful strategy to improve the adhesion, proliferation and differentiation of osteoblast-like cells to implant materials. Such biomimetic strategy aims at targeting integrins αvß3 and α5ß1, which are highly expressed on osteoblasts and are essential for many fundamental functions in bone tissue development. The successful grafting of the bioactive molecules on titanium is proven by contact angle measurements, X-ray photoelectron spectroscopy and fluorescent labeling. Early attachment and spreading of cells are statistically enhanced by both peptidomimetics compared to unmodified titanium, reaching values of cell adhesion comparable to those obtained with full-length extracellular matrix proteins. Moreover, an increase in alkaline phosphatase activity, and statistically higher cell proliferation and mineralization are observed on surfaces coated with the peptidomimetics. This study shows an unprecedented biological activity for low-molecular-weight ligands on titanium, and gives striking evidence of the potential of these molecules to foster bone regeneration on implant materials.

Antibacterial properties of hLf1-11 peptide onto titanium surfaces: a comparison study between silanization and surface initiated polymerization.

Dental implant failure can be associated with infections that develop into peri-implantitis. In order to reduce biofilm formation, several strategies focusing on the use of antimicrobial peptides (AMPs) have been studied. To covalently immobilize these molecules onto metallic substrates, several techniques have been developed, including silanization and polymer brush prepared by surface-initiated atom transfer radical polymerization (ATRP), with varied peptide binding yield and antibacterial performance. The aim of the present study was to compare the efficiency of these methods to immobilize the lactoferrin-derived hLf1-11 antibacterial peptide onto titanium, and evaluate their antibacterial activity in vitro. Smooth titanium samples were coated with hLf1-11 peptide under three different conditions: silanization with 3-aminopropyltriethoxysilane (APTES), and polymer brush based coatings with two different silanes. Peptide presence was determined by X-ray photoelectron spectroscopy, and the mechanical stability of the coatings was studied under ultrasonication. The LDH assays confirmed that HFFs viability and proliferation were no affected by the treatments. The in vitro antibacterial properties of the modified surfaces were tested with two oral strains (Streptococcus sanguinis and Lactobacillus salivarius) showing an outstanding reduction. A higher decrease in bacterial attachment was noticed when samples were modified by ATRP methods compared to silanization. This effect is likely due to the capacity to immobilize more peptide on the surfaces using polymer brushes and the nonfouling nature of polymer PDMA segment.

Silver deposition on titanium surface by electrochemical anodizing process reduces bacterial adhesion of Streptococcus sanguinis and Lactobacillus salivarius.

OBJECTIVES: The aim of this study was to determine the antibacterial properties of silver-doped titanium surfaces prepared with a novel electrochemical anodizing process. MATERIAL AND METHODS: Titanium samples were anodized with a pulsed process in a solution of silver nitrate and sodium thiosulphate at room temperature with stirring. Samples were processed with different electrolyte concentrations and treatment cycles to improve silver deposition. Physicochemical properties were determined by X-ray photoelectron spectroscopy, contact angle measurements, white-light interferometry, and scanning electron microscopy. Cellular cytotoxicity in human fibroblasts was studied with lactate dehydrogenase assays. The in vitro effect of treated surfaces on two oral bacteria strains (Streptococcus sanguinis and Lactobacillus salivarius) was studied with viable bacterial adhesion measurements and growth curve assays. Nonparametric statistical Kruskal-Wallis and Mann-Whitney U-tests were used for multiple and paired comparisons, respectively. Post hoc Spearman's correlation tests were calculated to check the dependence between bacteria adhesion and surface properties. RESULTS: X-ray photoelectron spectroscopy results confirmed the presence of silver on treated samples and showed that treatments with higher silver nitrate concentration and more cycles increased the silver deposition on titanium surface. No negative effects in fibroblast cell viability were detected and a significant reduction on bacterial adhesion in vitro was achieved in silver-treated samples compared with control titanium. CONCLUSIONS: Silver deposition on titanium with a novel electrochemical anodizing process produced surfaces with significant antibacterial properties in vitro without negative effects on cell viability.

Covalent immobilization of hLf1-11 peptide on a titanium surface reduces bacterial adhesion and biofilm formation.

Bacterial infection represents a major cause of implant failure in dentistry. A common approach to overcoming this issue and treating peri-implant infection consists in the use of antibiotics. However, the rise of multidrug-resistant bacteria poses serious concerns to this strategy. A promising alternative is the use of antimicrobial peptides due to their broad-spectrum activity against bacteria and reduced bacterial resistance responses. The aim of the present study was to determine the in vitro antibacterial activity of the human lactoferrin-derived peptide hLf1-11 anchored to titanium surfaces. To this end, titanium samples were functionalized with the hLf1-11 peptide either by silanization methods or physical adsorption. X-ray photoelectron spectroscopy analyses confirmed the successful covalent attachment of the hLf1-11 peptide onto titanium surfaces. Lactate dehydrogenase assay determined that hLf1-11 peptide did not affect fibroblast viability. An outstanding reduction in the adhesion and early stages of biofilm formation of Streptococcus sanguinis and Lactobacillus salivarius was observed on the biofunctionalized surfaces compared to control non-treated samples. Furthermore, samples coated with the hLf1-11 peptide inhibited the early stages of bacterial growth. Thus, this strategy holds great potential to develop antimicrobial biomaterials for dental applications.

A low elastic modulus Ti-Nb-Hf alloy bioactivated with an elastin-like protein-based polymer enhances osteoblast cell adhesion and spreading.

ß-type titanium alloys with low Young's modulus are desirable to reduce stress shielding effect and enhance bone remodeling for implants used to substitute failed hard tissue. For biomaterials application, the surface bioactivity is necessary to achieve optimal osseointegration. In the previous work, the low elastic modulus (43 GPa) Ti-25Nb-16Hf (wt %) alloy was mechanically and microstructurally characterized. In the present work, the biological behavior of Ti-25Nb-16Hf was studied. The biological response was improved by surface modification. The metal surface was modified by oxygen plasma and subsequently silanized with 3-chloropropyl(triethoxy)silane for covalent immobilization of the elastin-like polymer. The elastin-like polymer employed exhibits RGD bioactive motives inspired to the extracellular matrix in order to improve cell adhesion and spreading. Upon modification, the achieved surface presented different physical and chemical properties, such as surface energy and chemical composition. Subsequently, osteoblast adhesion, cell numbers, and differentiation studies were performed to correlate surface properties and cell response. The general tendency was that the higher surface energy the higher cell adhesion. Furthermore, cell culture and immunofluorescence microscopy images demonstrated that RGD-modified surfaces improved adhesion and spreading of the osteoblast cell type.

Influence of the height of the external hexagon and surface treatment on fatigue life of commercially pure titanium dental implants.

PURPOSE: This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants. MATERIALS AND METHODS: Electropolished commercially pure titanium dental implants (seven implants per group) with three different external hexagon heights (0.6, 1.2, and 1.8 mm) and implants with the highest external hexagon height (1.8 mm) and different surface treatments (electropolishing, grit blasting with aluminium oxide, and acid etching with sulfuric acid) were tested to evaluate their mechanical fatigue life. To do so, 10-Hz triangular flexural load cycles were applied at 37 degrees C in artificial saliva, and the number of load cycles until implant fracture was determined. Tolerances of the hexagon/abutment fit and implant surface roughness were analyzed by scanning electron microscopy and light interferometry. Transmission electron microscopy and electron diffraction analyses of titanium hydrides were performed. RESULTS: First, the fatigue life of implants with the highest hexagon (8,683 +/- 978 load cycles) was more than double that of the implants with the shortest hexagons (3,654 +/- 789 load cycles) (P < .02). Second, the grit-blasted implants had the longest fatigue life of the tested materials (21,393 +/- 2,356 load cycles), which was significantly greater than that of the other surfaces (P < .001). The compressive surface residual stresses induced when blasting titanium are responsible for this superior mechanical response. Third, precipitation of titanium hydrides in grain boundaries of titanium caused by hydrogen adsorption from the acid solution deteriorates the fatigue life of acid-etched titanium dental implants. These implants had the shortest fatigue life (P < .05). CONCLUSIONS: The fatigue life of threaded root-form dental implants varies with the height of the external hexagon and/or the surface treatment of the implant. An external hexagon height of 1.8 mm and/or a blasting treatment appear to significantly increase fatigue life of dental implants.

The concept of brain death did not evolve to benefit organ transplants.

Although it is commonly believed that the concept of brain death (BD) was developed to benefit organ transplants, it evolved independently. Transplantation owed its development to advances in surgery and immunosuppressive treatment; BD owed its origin to the development of intensive care. The first autotransplant was achieved in the early 1900s, when studies of increased intracranial pressure causing respiratory arrest with preserved heartbeat were reported. Between 1902 and 1950, the BD concept was supported by the discovery of EEG, Crile's definition of death, the use of EEG to demonstrate abolition of brain potentials after ischaemia, and Crafoord's statement that death was due to cessation of blood flow. Transplantation saw the first xenotransplant in humans and the first unsuccessful kidney transplant from a cadaver. In the 1950s, circulatory arrest in coma was identified by angiography, and the death of the nervous system and coma dépassé were described. Murray performed the first successful kidney transplant. In the 1960s, the BD concept and organ transplants were instantly linked when the first kidney transplant using a brain-dead donor was performed; Schwab proposed to use EEG in BD; the Harvard Committee report and the Sydney Declaration appeared; the first successful kidney, lung and pancreas transplants using cadaveric (not brain-dead) donors were achieved; Barnard performed the first human heart transplant. This historical review demonstrates that the BD concept and organ transplantation arose separately and advanced in parallel, and only began to progress together in the late 1960s. Therefore, the BD concept did not evolve to benefit transplantation.

Experimental evaluation of a new layered prosthesis exhibiting a low tensile modulus of elasticity: long-term integration response within the rat abdominal wall.

The use of a new type of prosthesis, Bard Composix (BC), constructed of two layers of polypropylene mesh (PP) and one layer of expanded polytetrafluoroethylene (ePTFE), could provide a good solution for hernia repair when both minimal adhesions and maximum collagenous infiltration are necessary. We experimentally evaluated long-term stability of this composite. In 15 Sprague-Dawley rats, a full thickness defect was created in the anterior abdominal wall and repaired with BC. Studies were performed over implantation intervals of 2, 4, and 6 months in strips obtained from the prosthesis-host tissue interfaces. Light microscopy, environmental scanning electron microscopy (ESEM), immunohistochemistry, and tensiometry were used. Overall findings provide evidence that PP and ePTFE association renders the alloy well suited for hernia repair, promoting a robust and durable alloplast-soft tissue union. At all points studied, the patch was well tolerated and meshes did not shrink, come loose, or migrate. Neovascularization continued 6 months after implantation. Ex vivo mechanical characterization demonstrated that the primary advantage of the new device stems from a low modulus of elasticity, a property that can be exploited to enhance mechanical load transfer from prosthetic materials to the relatively frail surrounding tissues. After implantation, adequate tensile strength and a low modulus of elasticity were detected in the restored zone, conferring great adaptability to the abdominal wall. In conclusion, the BC layered prosthesis proved suitable for implantation in abdominal wall defects, exhibiting favorable biocompatibility and integration with minimal side effects.