Rogerio Colaço

Instituto Superior Técnico, Lisbon, Portugal · Mechanical Engineering

Osteochondral (OC) defects combine damage to cartilage and subchondral bone, posing a significant challenge to their repair due to the dissimilar characteristics and regenerative capabilities between the two tissues. Here, we propose novel OC bilayer composites, drawing inspiration from corresponding biological tissues and using a combination of si...

Calcium phosphate cements (CPCs) have been increasingly used as synthetic bone substitutes for repair and regeneration of bone defects given their biocompatibility, resemblance to bone and malleability. Moreover, their use as local antibiotic delivery systems is of main interest against bone infections, avoiding the adverse effects of high dosages...

Leucite and zirconia are commonly used in the production of prosthetic dental materials. Leucite presents attractive optical properties but low toughness and wear resistance, which limits its use. Zirconia has much higher toughness, but due to aesthetic reasons and ageing issues, needs to be glass veneered. Chipping of such veneer is usually respon...

Introduction Polyvinyl alcohol (PVA) hydrogels have been considered very promising materials for the replacement of cartilage tissues due to their biocompatibility, chemical resistance, swelling capacity, and tribological behaviour [1,2]. However, their mechanical properties are still far from those of articular cartilage. In the present work, some...

Introduction Cartilage damage is an important concern because of the tissue's limited ability to repair itself [1 Karuppal R. Current concepts in the articular cartilage repair and regeneration. J Orthop. 2017;14:A1–3.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar],2 Oliveira AS, Seidi O, Ribeiro N, et al. Tribomechanical comparison bet...

Introduction Teeth whitening is a highly demanded aesthetic dental procedure to remove teeth stains and get a whiter and perfect smile. This type of treatment is usually performed by the application on the teeth surface of hydrogen or carbamide peroxides which diffuse through the external layer of the teeth, enamel [1 Santos LF, Torres CR, Caneppel...

Introduction Calcium phosphate cements (CPCs) have been widely used for bone defect´s filling given their excellent biocompatibility, osteoconduction ability and ease of manipulation [1 Zhang J, Liu W, Schnitzler V, et al. Calcium phosphate cements for bone substitution: chemistry, handling and mechanical properties. Acta Biomater. 2014;10(3):1035–...

The effect of 30% H2O2 solutions with different pH (2, 4 and 6) on the wear of human dental enamel was studied. Additionally, the whitening efficiency and changes in hardness and morphology were evaluated. The enamel tribological response was accessed through two different approaches: ball-on-plate and atomic force microscopy (AFM), the later follo...

Wear of nanoelectromechanical systems (NEMS)/microelectromechanical systems (MEMS) involves a limited number of superficial atomic layers. In larger components, where tolerances and surface roughness are usually quite small, wear also occurs essentially in a narrow near-surface region, with not more than few hundreds nanometres. Therefore, in gener...

This study aims to evaluate the tribological performance of the pair human teeth/robocasted zirconia, with a special focus on the enamel wear mechanisms. Zirconia pieces produced by robocasting (RC) and unidirectional compression (UC) were compared in terms of crystalline structure, density, porosity, hardness and toughness. Chewing simulation test...

The present study has the objective of evaluating the effect of lysozyme on the tribological response of the Ti6Al4V/zirconia interface. For that, reciprocating pin-on-plate wear tests of balls of Ti6Al4V against plates of zirconia are performed in artificial saliva, with and without the addition of the lysozyme. The results are compared with those...

The effect of the sequential implantation of C⁺ and Ti⁺ ions on the microstructure and tribophysical properties of smooth crystalline silicon surfaces (c-Si) is evaluated. Microstructural characterization of the samples was performed by scanning electron microscopy, grazing incidence X-ray diffraction and by Rutherford backscattering spectrometry....

Objectives: The main goal of this work is to evaluate the suitability of nanostructured zirconia pieces obtained by robocasting additive manufacturing (AM), for dental applications. Methods: The density, crystalline structure, morphology/porosity, surface roughness, hardness, toughness, wettability and biocompatibility of the produced samples we...

This work aims to understand the effect of dilute hydrogen peroxide (H2O2) solutions, used in dental whitening treatments, on the nanostructure of type I collagen fibers. Using this approach, collagen fibers were exposed to 1%, 3% and 5% H2O2 solutions, and the changes in their nanostructure were analyzed by combining topographical and phase-shift...

Purpose To investigate the possibility of using acrylic intraocular lenses (IOLs) to ensure a controlled and sustained release of moxifloxacin (MXF), an antibiotic that is commonly used in endophthalmitis prophylaxis after cataract surgery. Setting Academic, industrial and clinical partners from Portugal, Belgium, Iceland and United States. Desig...

In this work, the effect of the exposure to acids that are usually present in the mouth environment on the tribological behavior of restorative dental microcomposites is evaluated. A commercial microcomposite widely used in dentistry (Filtek Z250) and a strong and a week acid that are part of the mouth environment (hydrochloric and lactic acid, res...

Topical administration of both antibiotic and non-steroidal anti-inflammatory drugs after cataract removal surgery is usually recommended to avoid infection and inflammatory process development. In this work, a HEMA/MMA based hydrogel was developed as a platform for simultaneous release of an antibiotic (moxifloxacin) and a non-steroidal anti-infla...

Introduction: The best treatment currently available for severe joint disease is total joint replacement by a prosthesis, which involves biocompatible metal alloys articulating against a metal, ceramic or polyethylene part. These devices often fail due to wear of the polymer by the harder counterface, which may cause inflammation, osteolysis and co...

Loosening and fracture of implanted dental crowns is a consequence of relative micromovements between the zirconia abutment and the titanium alloy of the implant, in a biochemical aggressive environment. Thus, it is important to establish the in vitro tribological testing conditions that better mimics such environment. The present work aims to eval...

Although contact lenses are promising platforms for ocular drug delivery and have been extensively studied for that purpose, the influence of sterilization methods on these systems remains barely investigated. In this work, a silicone-based hydrogel was produced and loaded with different ophthalmic drugs: levofloxacin, chlorhexidine, diclofenac and...

Drug loaded intraocular lenses have been proposed as an alternative to the conventional post-cataract removal prophylaxis through topical drug administration, since the drug or combination of drugs released from the lenses are delivered directly to the target site. In this work, a mathematical model to estimate the concentration of drug released fr...

The aim of the present work was to contribute for a deeper understanding of the intermolecular interactions present in ionic liquid (IL) tribofilms through the comparative study of the ILs behavior at water and at silica surfaces. Three hydrophobic ILs were investigated at the air/water interface (Langmuir trough) and at the water/silica interface...

Pastes of calcium silicate binders with low CaO/SiO2 (C/S) ratio with an overall C/S molar ratio of 1.1 were produced by mixing these materials with water or with an aqueous solution of Na2SiO3. Both types of pastes (non-activated and Na2SiO3 activated) were analysed using X-ray diffraction (XRD) and high-resolution transmission electron microscopy...

A quasi‐amorphous low‐calcium‐silicate hydraulic binder, with an overall CaO/SiO2 (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3%wt alkalis (either NaOH, Na2CO3 or Na2SiO3). The evolution of the hydration processes of the samples were monitored by compressive strength testing...

Despite the beneficial properties and outstanding potential of hydrogels for biomedical applications, several unmet challenges must be overcome, especially regarding to their known sensitivity to conventional sterilization methods. It is crucial for any biomaterial to withstand an efficient sterilization to obtain approval from regulatory organizat...

In recent years, with the development of micro/nanoelectromechanical systems (MEMS/NEMS), the demand for efficient lubricants of silicon surfaces intensified. Although the use of ionic liquids (ILs) as additives to base oils in the lubrication of steel/steel or other types of metal/ metal tribological pairs has been investigated, the number of stud...

It is shown that the activation of C/S=1.1 amorphous clinkers with Na2SiO3 opens an alternative path in the search for low-CO2 hydraulic binders. After hydration these new amorphous binders present CSH with a Tobermorite-like structure, and the setting reaction is developed with a very low reaction heat development.

The effects of sterilization methods on the intrinsic properties of drug delivery systems (DDS) remains understudied, which ends up delaying the development of new and more effective therapeutic devices. This fact becomes even more critical when considering hydrogel-based DDS, since the presence of water in the structure can lead to alterations in...

Intraocular lenses (IOLs) present an alternative for extended, local drug delivery in the prevention of post-operative acute endophthalmitis. In the present work, we modified the surface of a hydrophilic acrylic material, used for manufacturing of IOLs, through plasma-assisted grafting copolymerization of 2-acrylamido-2-methylpropane sulfonic acid...

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Sterilization of hydrogels is challenging due to their often reported sensitivity to conventional methods involving heat or radiation. Although aseptic manufacturing is a possibility, terminal sterilization is safer in biological terms, leading to a higher overall efficiency, and thus should be used whenever it is possible.

In the last years, nanostructured biomaterials have raised a great interest as platforms for delivery of drugs, genes, imaging agents and for tissue engineering applications. In particu- lar, hydrogel nanoparticles (HNP) associate the distinctive features of hydrogels (high water uptake capacity, biocompatibility) with the advantages of being possi...

Cytotoxicity. Cytotoxicity test data. (PDF)

ZetaSizer Statistical. Size, PDI and Zeta Potential statistical data. (XLSX)

ZetaSizer Data. Size, PDI and Zeta Potential data. (XLSX)

Transmittance. UV-Vis spectral data. (XLSX)

The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the par...

Experimental results obtained from drug release experiments. (XLSX)

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Introduction: Medical devices related infections contribute greatly to the increasing costs on health care systems around the world. Continued improvements in low-temperature sterilization systems, capable of demising the risk of infection and inflammation are needed. Ozone gas sterilization is emerging as an effective, low cost, safe and environme...

Ionic liquids (ILs) have been recently considered as potentially adequate lubricants for microelectromechanical and nanoelectromechanical systems (MEMS/NEMS) due to the specific features of these silicon based miniaturized devices. Aiming at the optimization of the lubrication of MEMS/NEMS, new ILs resulting from the combination of sulfur-containin...

Currently, most in vitro drug release studies for ophthalmic applications are carried out in static sink conditions. Although this procedure is simple and useful to make comparative studies, it does not describe adequately the drug release kinetics in the eye, considering the small tear volume and flow rates found in vivo. In this work, a microflui...

In this article, liposome-based coatings aiming to control drug release from therapeutic soft contact lenses (SCLs) materials are analyzed. A PHEMA based hydrogel material loaded with levofloxacin is used as model system for this research. The coatings are formed by polyelectrolyte layers containing liposomes of 1,2-dimyristoyl-sn-glycero-3-phospho...

In the present work, we present a study of the effect of Fe+ ion implantation on the tribological response at nanoscale contact lengths of crystalline silicon (c-Si) surfaces. (100) silicon wafers were implanted with Fe+ at a fluence of 2 x 10(17) cm(-2), followed by annealing treatments at temperatures of 800 degrees C and 1000 degrees C. After mi...

Symptoms of bacterial and fungal keratitis are typically treated through the frequent application of antibiotic and antifungal eye drops. The high frequency of half hourly or hourly eye drop administration required to treat these indications is tedious and could reduce compliance. Here, we combine in vitro experiments with a mathematical model to d...

http://www.frontiersin.org/10.3389/conf.FBIOE.2016.01.01046/event_abstract

Steel began to be used intensively in civil construction in the first quarter of the nineteenth century. By the end of this century, steel was commonly used as reinforcing material in concrete structures, increasing resistance to levels that the fragile Portland cement could not support by itself. The use of steel as a structural material in civil...

The relative motion between the zirconia abutment and the titanium implant in the presence of saliva might lead to tribocorrosion and consequently metal ion release and ion contamination of peri -implant tissues. In order to study this issue tribocorrosion, tests were performed in open circuit potential (OCP) and during anodic polarization in two d...

This chapter is a revised version of the text “Surface damage mechanisms: from nano and microcontacts to wear of materials” published in 2007 Meyer’s and Gnecco’s book “Fundamentals of Friction and Wear on the Nanoscale” [1].

The goal of our research was to investigate the possibility of using drug loaded intra-ocular lenses (IOLs) as an alternative to topical antibiotic usually prescribed after cataract surgery.

The irritation/discomfort associated with the use of contact lenses (CLs) is often related to the eyelid-lens friction. Although the use of such devices is widespread, the information about the influence of the lacrimal fluid biomolecules on the tribological behaviour of the CLs hydrogels is scarce. In this work, we investigated the effect of the p...

Self-lubricant behaviour of copper-carbon nanocomposites: An electron microscopy and atomic force microscopy study - Volume 21 Issue S6 - D. Silva, J. Jeremias, D. Nunes, J.B. Correia, K. Hanada, R. Colaço, P.A. Carvalho

1 0 0> Si wafers were dual implanted at room temperature with Fe + C and Ti + C with fluences of 2 × 1017 cm-2. The samples were annealed in vacuum at 800 °C and 1000 °C respectively, and characterized in scanning electron microscope (FEG-SEM), grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS). The scanning elec...

Single and dual ion implantation of c:Si with Fe+ and C+: microstructural characterization - Volume 21 Issue S6 - B. Nunes, E. Alves, R. Colaço

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Thirteen different cement-clinker crystalline phases present in the lime-silica-alumina system have been systematically modeled using a simple and general force field. The results were validated using experimental density and structural data. Six amorphous phases (corresponding to calcium/silicon ratios corresponding to belite, rankinite, wollaston...

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Novel ionic liquids (ILs) based on methylpyridinium cations combined with tetrafluoroborate and dicyanamide anions have been developed. These ILs were evaluated in terms of their surface tension and contact angles as well as tribological performance against steel and poly(tetrafluoroethylene) (PTFE) comparing with imidazolium and phosphonium based...

The development of new ophthalmic drug delivery systems capable of increasing the residence time of drugs in the eye and improve its bioavailability relatively to eyedrops has been object of intense research in recent years. Several studies have shown that drug-loaded therapeutic soft contact lenses (SCLs) constitute a promising approach, with seve...

Although the plasma technology has long been applied to treat contact lenses, the effect of this treatment on the performance of drug-loaded contact lenses is still unclear. The objective of this work is to study the effect of nitrogen plasma treatment on two drug-loaded polymeric formulations which previously demonstrated to be suitable for therap...

In the present work two types of polymers were investigated as drug releasing contact lens materials: a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone hydrogel. The silicone hydrogel resulted from the addition of TRIS, a hydrophobic monomer containing silicon (3-tris(trimethylsilyloxy)silylpropyl 2-methylprop-2-enoate), to pHEM...

Silicon wafers were implanted with iron ions at different fluences (from 5 x 10(15) up to 2 x 10(17) cm(-2)), followed by annealing treatments at temperatures from 550 degrees C to 1000 degrees C, aiming at evaluating the nanomechanical response of the samples and its relation with the microstructural features and characteristics of the modified la...

The uptake of water vapor by ionic liquids (ILs) has been studied by various research groups, but there is little knowledge on how liquid confinement affects the process of moisture absorption. In this work, several imidazolium-based ILs deposited on quartz crystals were used as water vapor sensors in a high sensitivity quartz-crystal microbalance...

A microstructure refined to the nanometer scale improves mechanical strength. However, ultra-fine grain metals exhibit low thermal stability, even at moderate temperatures [1], requiring the presence of particle dispersions to delay coarsening by grain boundary pinning. In addition, the concept of a composite can be applied to the context of nanost...

The high lateral resolution imaging and its technical versatility in property evaluation, together with the relatively straightforward characterization of viable biological structures in liquid media, render the AFM an unrivaled instrument in the definition of novel structural–functional relationships in bioengi- neering domains. This chapter provi...