Modulation of human osteoblasts by metal surface chemistry

Microstructure, mechanical properties and osseointegration ability of Ta-20Zr alloy used as dental implant material

The aim of this study was to evaluate the application prospect of a tantalum (Ta) and zirconium (Zr) alloy as a dental implant material. The Ta-20Zr (wt.%) alloy was prepared by powder metallurgy, and its microstructure and mechanical properties were analyzed by standard techniques. The effect of Ta-20Zr alloy on inflammation, bone remodeling and osseointegration was analyzed in rat and rabbit models by biochemical, histological and imaging tests. The Ta-20Zr alloy showed excellent mechanical compatibility with the bone tissue on account of similar elastic modulus (49.2 GPa), thereby avoiding the 'stress shielding effect'. Furthermore, Ta-20Zr alloy enhanced the inflammatory response by promoting secretion of interleukin-6 (IL-6) and IL-10, and facilitated the balance between the M1/M2 macrophage phenotypes. Finally, Ta-20Zr also showed excellent osseointegration and osteogenic ability without any systemic side effects, making it an ideal dental implant material.

Neurotrophin-mimicking peptides at the biointerface with gold respond to copper ion stimuli

The peptide fragments NGF_1-14 and BDNF_1-12, encompassing the N-terminal domains, respectively, of the proteins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) were used in this study for the fabrication of a hybrid gold/peptide biointerface. These peptides mimic the Trk receptor activation of the respective whole protein - with a crucial role played by copper ions - and exhibit, in bulk solution, a pH-dependent capability to complex copper. We demonstrate here the maintenance of peptide-specific responses at different pH values as well as the copper binding also for the adlayers formed upon physisorption at the gold surface. The physicochemical properties, including viscoelastic behavior of the adlayer and competitive vs. synergic interactions in sequential adsorption processes, were addressed both experimentally, by quartz crystal microbalance with dissipation monitoring (QCM-D) and circular dichroism (CD), and theoretically, by molecular dynamics (MD) calculations. Proof-of work biological assays with the neuroblastoma SY-SH5H cell line demonstrated that the developed hybrid Au/peptide nanoplatforms are very promising for implementation in pH- and metal-responsive systems for application in nanomedicine.

Influence of different grained powders and pellets made of Niobium and Ti-42Nb on human cell viability

Nowadays, biomaterials can be used to maintain or replace several functions of the human body if necessary. Titanium and its alloys, i.e. Ti6Al4V are the most common materials (70 to 80%) used for structural orthopedic implants due to their unique combination of good mechanical properties, corrosion resistance and biocompatibility. Addition of β-stabilizers, e.g. niobium, can improve the mechanical properties of such titanium alloys further, simultaneously offering excellent biocompatibility. In this in vitro study, human osteoblasts and fibroblasts were cultured on different niobium specimens (Nb Amperit, Nb Ampertec), Nb sheets and Ti-42Nb (sintered and 3D-printed by selective laser melting, SLM) and compared with forged Ti6Al4V specimens. Furthermore, human osteoblasts were incubated with particulates of the Nb and Ti-42Nb specimens in three concentrations over four and seven days to imitate influence of wear debris. Thereby, the specimens with the roughest surfaces, i.e. Ti-42Nb and Nb Ampertec, revealed excellent and similar results for both cell types concerning cell viability and collagen synthesis superior to forged Ti6Al4V. Examinations with particulate debris disclosed a dose-dependent influence of all powders with Nb Ampertec showing the highest decrease of cell viability and collagen synthesis. Furthermore, interleukin synthesis was only slightly increased for all powders. In summary, Nb Ampertec (sintered Nb) and Ti-42Nb materials seem to be promising alternatives for medical applications compared to common materials like forged or melted Ti6Al4V.

Porous titanium and Ti-35Nb alloy: effects on gene expression of osteoblastic cells derived from human alveolar bone

Tests on titanium alloys that possess low elastic modulus, corrosion resistance and minimal potential toxicity are ongoing. This study aimed to evaluate the behavior of human osteoblastic cells cultured on dense and porous Titanium (Ti) samples comparing to dense and porous Ti-35 Niobium (Ti-35Nb) samples, using gene expression analysis. Scanning electronic microscopy confirmed surface porosity and pore interconnectivity and X-ray diffraction showed titanium beta-phase stabilization in Ti-35Nb alloy. There were no differences in expression of transforming growth factor-β, integrin-β1, alkaline phosphatase, osteopontin, macrophage colony stimulating factor, prostaglandin E synthase, and apolipoprotein E regarding the type of alloy, porosity and experimental period. The experimental period was a significant factor for the markers: bone sialoprotein II and interleukin 6, with expression increasing over time. Porosity diminished Runt-related transcription factor-2 (Runx-2) expression. Cells adhering to the Ti-35Nb alloy showed statistically similar expression to those adhering to commercially pure Ti grade II, for all the markers tested. In conclusion, the molecular mechanisms of interaction between human osteoblasts and the Ti-35Nb alloy follow the principal routes of osseointegration of commercially pure Ti grade II. Porosity impaired the route of transcription factor Runx-2.

The physicochemical/biological properties of porous tantalum and the potential surface modification techniques to improve its clinical application in dental implantology

More rapid restoration and more rigid functionality have been pursued for decades in the field of dental implantology. Under such motivation, porous tantalum has been recently introduced to design a novel type of dental implant. Porous tantalum bears interconnected porous structure with pore size ranging from 300 to 600μm and a porosity of 75-85%. Its elastic modulus (1.3-10GPa) more closely approximates that of natural cortical (12-18GPa) and cancellous bone (0.1-0.5GPa) in comparison with the most commonly used dental materials, such as titanium and titanium alloy (106-115GPa). Porous tantalum is highly corrosion-resistant and biocompatible. It can significantly enhance the proliferation and differentiation of primary osteoblasts derived from elderly people than titanium. Porous tantalum can allow bone ingrowth and establish not only osseointegration but also osseoincorporation, which will significantly enhance the secondary stability of implants in bone tissue. In this review, we summarize the physicochemical, mechanical and biological properties of porous tantalum. We further discuss the performance of current tantalum dental implants and present the methodologies of surface modifications in order to improve their biological performance.

Impact of surface chemistry and topography on the function of antigen presenting cells

The impact of biomaterial surface topography and chemistry on antigen presenting cells’ phenotype and function.

Estudo in vitro da influência do formato e do tratamento de superfície de implantes odontológicos no torque de inserção, resistência ao arrancamento e frequência de ressonância

OBJETIVO: A proposta do estudo foi avaliar a influência do formato e do tratamento de superfície na estabilidade primária de implantes odontológicos, inseridos em diferentes substratos, utilizando-se associação de métodos, como torque de inserção, resistência ao arrancamento e frequência de ressonância. MATERIAL E MÉTODO: Foram utilizados 32 implantes da marca Conexão® (Conexão Sistemas de Prótese Ltda, Arujá, São Paulo, Brasil), sendo: oito cilíndricos com tratamento Porous (CA), oito cilíndricos usinados (MS), oito cilíndricos tratamento duplo Porous (MP) e oito cônicos sem tratamento (CC). Os substratos utilizados para inserção foram: costela de porco; poliuretana Synbone©; poliuretana Nacional® (15, 20, 40 PCF), e madeira. O torque de inserção (TI) foi quantificado utilizando-se um torquímetro digital Kratos®; a força de arrancamento (RA) foi aferida por meio de tração axial, realizada em uma Máquina Universal de Ensaios (Emic® DL-10000), e utilizou-se também análise por meio de frequência de ressonância (RF). Para obtenção dos resultados estatísticos, utilizou-se análise de variância e teste de Tukey (significância de 5%). RESULTADO: Ao analisar o torque de inserção, verificou-se que os implantes com tratamento de superfície não foram diferentes estatisticamente dos usinados, assim como os implantes cilíndricos não tiveram diferença dos cônicos em todos os substratos (p>0,05), com exceção da poliuretana Synbone©. Em relação à resistência ao arrancamento, os implantes tratados e usinados, assim como cônicos e cilíndricos, não tiveram diferença estatística (p>0,05); a análise de frequência de ressonância mostrou que não houve diferença entre os implantes (p>0,05), com exceção da poliuretana Nacional® (20 PCF). CONCLUSÃO: Os formatos e o tratamento de superfície estudados não demonstraram valores significantes quando foram comparados os implantes entre si e, considerando os substratos avaliados, não houve diferença estatística entre os diferentes tipos de implantes.

Magnesium-based bone implants: immunohistochemical analysis of peri-implant osteogenesis by evaluation of osteopontin and osteocalcin expression

The functions of some bone proteins, as osteopontin (OPN) and osteocalcin (OC), have been discovered by the latest studies. This fact suggests the possibility of their immunodetection to characterize peri-implant osteogenesis and implant impact on it. Cylindrical pins of Mg alloys (MgCa0.8, LAE442, ZEK100, LANd442) and titanium alloy (TiAl6V4) were implanted into the tibial medullae of 46 rabbits. Each group was divided regarding to implant duration (3 and 6 months). Bone samples adjacent to the implants were decalcified and treated with routine histological and immunohistochemical protocols using OC and OPN-antibodies. OC was detected in matrix of compact bone, but very rarely in osteoid and bone cells. OPN was detected intracellularly and in osteoid. After 3 months, the highest level of both markers was found in titanium group, followed by LAE442-group. In contrast to LAE442 and TiAl6V4, the other Mg alloys showed increasing levels of OC after 6 months. Lower levels of OP and OC compared to the control group are related to the continuous implant degradation and instability of bone-implant interface in early post-surgical period. Reduced marker's expression in LAE442 and TiAl6V4 groups after 6 months may indicate stabilization of bone-implant interface and completion of peri-implant neo-osteogenesis. Declining characters of OC and OPN expression over the implantation time, as well as their lowest levels in late post-surgical term, suggest a more appropriate biocompatibility of LAE442, which therefore seems to be the most preferable of the tested materials for the use in orthopaedic applications.