Catalin Popa

Porous c.p. Titanium Using Dextrin as Space Holder for Endosseous Implants

Porous structures are advantageous alternatives to bulk titanium for endosseous implants because the elastic modulus can be adjusted to match that of bone, preventing bone retraction. Porous titanium scaffolds were developed using corn starch dextrin powder with increased granularity to obtain larger pores. Titanium and dextrin powder mixtures in different proportions (15, 25, 35 and 40% dextrin) were die-pressed and sintered under high vacuum. The porosity of the implants was between 21.80 and 37.79%. The surface of porous titanium was characterized by SEM analysis that showed presence of pore sizes over 100 µm for all compacts, except those with 15% dextrin. For samples with 35 and 40% dextrin, the size of pores reached 200–250 µm. X-ray diffraction analysis of titanium samples revealed presence of TiOCN compound with progressive increase with dextrin content. Mechanical characteristics were investigated by compression tests. Osteoblasts adhesion and proliferation was determined by MTT assay and scanning electron microscopy (SEM) analysis. Expression of proteins involved in differentiation and cell adhesion osteopontin (OPN) and intercellular adhesion molecule 1 (ICAM-1) were investigated by immunocytochemical staining. Implants that met both mechanical conditions closest to the bone and improved biocompatibility were samples with 35 and 45% dextrin, recommending their use in bone tissue engineering.

Curcumin delivered through bovine serum albumin/polysaccharides multilayered microcapsules

The aim of the paper is to obtain and characterize k-carrageenan–chitosan dual hydrogel multilayers shell BSA gel microcapsules, as a carrier for curcumin, and as a possible antitumoral agent in biological studies. We used the CaCO3 template to synthesize non-toxic CaCO3/BSA particles as microtemplates by coprecipitating a CaCl2 solution that contains dissolved BSA, with an equimolar Na2CO3 solution. The microcapsules shell is assembled through a layer-by-layer deposition technique of calcium cross-linked k-carrageenan hydrogel alternating with polyelectrolite complex hydrogel formed via electrostatic interactions between k-carrageenan and chitosan. After the removal of CaCO3 through Ca2+ complexation with EDTA, and by a slightly treatment with HCl diluted solution, the BSA core is turned into a BSA gel through a thermal treatment. The BSA gel microcapsules were then loaded with curcumin, through a diffusion process from curcumin ethanolic solution. All the synthesized particles and microcapsules were stucturally characterized by: Fourier Transform Infrared Spectroscopy, UV–Vis Spectrometry, X-ray diffraction, thermal analysis, fluorescence spectroscopy, fluorescence optical microscopy, confocal laser scanning microscopy and scanning electron microscopy. The behavior of curcumin loaded microcapsules in media of different pH (SGF, SIF and PBS) was studied in order to reveal the kinetics and the release profile of curcumin. The in vitro evaluation of the antitumoral activity of encapsulated curcumin microcapsules on HeLa cell line and the primary culture of mesenchymal stem cells is the main reason of the microcapsules synthesis as BSA-based vehicle meant to enhance the biodisponibility of curcumin, whose anti-tumor, anti-oxidant and anti-inflammatory properties are well known.

Comparative in vitro study regarding the biocompatibility of titanium-base composites infiltrated with hydroxyapatite or silicatitanate

BackgroundThe development of novel biomaterials able to control cell activities and direct their fate is warranted for engineering functional bone tissues. Adding bioactive materials can improve new bone formation and better osseointegration. Three types of titanium (Ti) implants were tested for in vitro biocompatibility in this comparative study: Ti6Al7Nb implants with 25% total porosity used as controls, implants infiltrated using a sol–gel method with hydroxyapatite (Ti HA) and silicatitanate (Ti SiO2). The behavior of human osteoblasts was observed in terms of adhesion, cell growth and differentiation.ResultsThe two coating methods have provided different morphological and chemical properties (SEM and EDX analysis). Cell attachment in the first hour was slower on the Ti HA scaffolds when compared to Ti SiO2 and porous uncoated Ti implants. The Alamar blue test and the assessment of total protein content uncovered a peak of metabolic activity at day 8–9 with an advantage for Ti SiO2 implants. Osteoblast differentiation and de novo mineralization, evaluated by osteopontin (OP) expression (ELISA and immnocytochemistry), alkaline phosphatase (ALP) activity, calcium deposition (alizarin red), collagen synthesis (SIRCOL test and immnocytochemical staining) and osteocalcin (OC) expression, highlighted the higher osteoconductive ability of Ti HA implants. Higher soluble collagen levels were found for cells cultured in simple osteogenic differentiation medium on control Ti and Ti SiO2 implants. Osteocalcin (OC), a marker of terminal osteoblastic differentiation, was most strongly expressed in osteoblasts cultivated on Ti SiO2 implants.ConclusionsThe behavior of osteoblasts depends on the type of implant and culture conditions. Ti SiO2 scaffolds sustain osteoblast adhesion and promote differentiation with increased collagen and non-collagenic proteins (OP and OC) production. Ti HA implants have a lower ability to induce cell adhesion and proliferation but an increased capacity to induce early mineralization. Addition of growth factors BMP-2 and TGFβ1 in differentiation medium did not improve the mineralization process. Both types of infiltrates have their advantages and limitations, which can be exploited depending on local conditions of bone lesions that have to be repaired. These limitations can also be offset through methods of functionalization with biomolecules involved in osteogenesis.

Composite PLA scaffolds reinforced with PDO fibers for tissue engineering

Novel composite scaffolds were produced using long continuous bidirectional fibers embedded in an electrospun matrix, with the aim of using them in soft tissue engineering applications. The fibers are of polydioxanone and the matrix of polylactic acid. The novel manufacturing method consists of direct electrospinning performed on both sides of a collector that supports the already arranged fibers. The scaffolds were tested in vitro using 3T3 mouse fibroblasts as-obtained or functionalized with biotin or poly (dopamine). Functionalization did not significantly affect cells attachment, metabolic activity, or proliferation, but poly (dopamine) was proven to be effective in inducing hydrophilicity to the surface.

Selective laser melting of Ti6Al7Nb with hydroxyapatite addition

Purpose – The purpose of this paper was to obtain by means of selective laser melting and then characterize biocomposites of medical-grade Ti6Al7Nb with hydroxyapatite (2 and 5 vol.%) and without hydroxyapatite, as reference. Design/methodology/approach – Rectangular samples were manufactured with the same scanning strategy; the laser power was between 50 W and 200 W. Processed samples were analysed by means of optical microscopy, scanning electron microscopy and microhardness. Findings – The results showed that despite the very short processing times, hydroxyapatite decomposed and interacted with the base Ti6Al7Nb material. The decomposition degree was found to depend on the applied laser power. From the porosity and bulk microstructure point of view, the most appropriate materials for the purposed medical applications were Ti6Al7Nb with hydroxyapatite processed with a laser power of 50 W. Originality/value – The originality of the present work consists in the study of the behaviour and interaction of hy...

Research on the Intermetallic Compounds Formation in a Ni-Ti Alloy Obtained through Powder Metallurgy Specific Methods

NiTi alloys, due to the special properties they posses, good corrosion resistance, biocompatibility, and shape memory, are used successfully in the medical field. The paper presents research concerning the elaboration of the NiTi alloy in the form of spherical shape powder with hollow particles. This type of powder would be the raw material for fabricating light weight products like prosthesis or surgical implants. The aim of the research was to elaborate this type of powder and determine the alloy’s phases in correlation with the need of obtaining a specific particle shape. Along with these aspects it was attempted to form different testing samples through sintering operations.

Complex electronic implants and polymer packaging needs

Implantable and direct contact electronic devices for underpinning complex tissue functions as well as physiological monitoring have the opportunity to revolutionize health care in an ageing population. A major EU-consortium of 25 partners has been developing electronic devices for functional electrical stimulation, glaucoma and CNS pressure monitoring and as cochlear, retinal and urethral implants. A key need, however, is the packaging of such complex devices to enhance tissue biocompatibility, and to protect conducting elements from in vivo corrosion during extended use. Accordingly, we have investigated candidate polymeric barriers as hydration resistant and solute impermeable in interphases to mitigate the major problems of chronic implantation. Materials include silicone rubber, PVC, polyurethane, sulphonated polyetherether sulphone polyether-sulphone (SPEES-PES) and polycarbonate as underlayer and carbon like carbon (DLC), sol-gel modified oxides and Parylene C for top layers. A key strategy is polymer modification through incorporation variously of surfactant (Aliquat 336) and synthetic lipid (isopropyl myristate) to manipulate permeability to water and to low molecular weight solutes. Surface biocompatibility was assessed on the basis of protein film deposition in vitro and by cell viability studies in tissue culture. Polypyrrole deposited on gold coatings was used as a substrate for cell testing. None of the materials tested showed short-term toxicity, though there were substantial differences in hydration. Results with polypyrrole suggest that both electrical conductivity and tissue interfacing to be viable if used as coatings over active electrode components.

SEM Analysis of the Interface of Five Adhesive Systems

The aim of this study was to investigate the interface ultrastructure at dentin and hybrid layer formed by novel adhesives with TiO2 nano-fillers. Nano-fillers have shown outstanding mechanical properties and they are widely used as reinforcing materials associated with polymeric matrices for high performance applications. Twenty extracted non carious human teeth were utilized for evaluation of the bonded interface using scanning electron microscopy. The experiments used four novel adhesives (noted A1, A2, A3, A4). Phosphoric acid (5s, 37%) and a commercial resin composite Herculite XRV (Kerr) filling were used for the surface treatment. The interface was studies using scanning electron microscopy (SEM) using a microscope Inspect F-FEI Company. The experimental results indicated the main benefits and disadvantages of the investigated adhesives systems. SEM of the adhesive dentin interface revealed a HAp (hydroxyapatite) – rich and homogenous hybrid layer. This layer produced a favourable sealing of damaged dentin.

Mesenchymal Stem Cell Response to Surface Altered Porous Ti

This work aims to investigate the influence of surface conditioning of porous Ti for enhancing its biological activity, as assessed by in vitro stem cell testing. Porous Ti samples with an average porosity of 32% were processed by Powder Metallurgy with dextrin as a space holder. The samples were subjected to H2O2 treatment to form an enhanced TiO2 film, followed by a heat treatment at 400°C and 600°C aiming to the crystallization of the as-formed amorphous titanium oxide. Samples characterization was performed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD). The treated surfaces revealed to be made of both anatase and rutile TiO2, with groove–shaped structure and cracks on the surface of the TiO2 film. The intrinsic biocompatibility of the chemically modified porous Ti surfaces was assessed in vitro. In our cell culture tests, stem cells were found to attach and proliferate better on the chemically treated Ti surfaces compared to the control untreated Ti surfaces.

The Influence of Barium Carbonate on the Tribological Characteristics of Some Iron-based Friction Composites

New iron-based composite materials with addition of barium carbonate (2 to 8 wt% barium carbonate) for friction applications are investigated. The tribological behavior of the studied materials was determined by a pin-on-disk method when a cast iron disk was employed. The addition of 2 wt% barium carbonate determined a significant increase of the average friction coefficient. Instead a further increase of barium carbonate content determined a gradual decrease of this parameter. The improvement of wear resistance was marked out for a barium carbonate content of up to 6 wt%. The optimal ratio between the average friction coefficient and the wear rate for the researched Fe-Cu-graphite-Ni-BaCO3 composites was determined for the iron-based material containing 2 wt% barium carbonate. SEM, EDX and XRD analysis marked out a complex structure containing alloyed ferrite, pearlite and carbides, traces of nickel and barium carbonate and free graphite.