Antimicrobial passive coatings for titanium dental implants

Poster apresentado no 2º Workshop AC-PMME (da Área Científica de Projecto Mecânico e Materiais Estruturais). Instituto Superior Técnico, Lisboa, 14 de Setembro de 2016N/

About the sterilization of chitosan hydrogel nanoparticles

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 particular, hydrogel nanoparticles (HNP) associate the distinctive features of hydrogels (high water uptake capacity, biocompatibility) with the advantages of being possible to tailor its physicochemical properties at nano-scale to increase solubility, immunocompatibility and cellular uptake. In order to be safe, HNP for biomedical applications, such as injectable or ophthalmic formulations, must be sterile. Literature is very scarce with respect to sterilization effects on nanostructured systems, and even more in what concerns HNP. This work aims to evaluate the effect and effectiveness of different sterilization methods on chitosan (CS) hydrogel nanoparticles. In addition to conventional methods (steam autoclave and gamma irradiation), a recent ozone-based method of sterilization was also tested. A model chitosan-tripolyphosphate (TPP) hydrogel nanoparticles (CS-HNP), with a broad spectrum of possible applications was produced and sterilized in the absence and in the presence of protective sugars (glucose and mannitol). Properties like size, zeta potential, absorbance, morphology, chemical structure and cytotoxicity were evaluated. It was found that the CS-HNP degrade by autoclaving and that sugars have no protective effect. Concerning gamma irradiation, the formation of agglomerates was observed, compromising the suspension stability. However, the nanoparticles resistance increases considerably in the presence of the sugars. Ozone sterilization did not lead to significant physical adverse effects, however, slight toxicity signs were observed, contrarily to gamma irradiation where no detectable changes on cells were found. Ozonation in the presence of sugars avoided cytotoxicity. Nevertheless, some chemical alterations were observed in the nanoparticles.info:eu-repo/semantics/publishedVersio

Entrevista sobre boas práticas em pregão eletrônico e SRP com o professor da ENAP Vinicius Martins

Na vigésima nona entrevista exclusiva para a Comunidade de Compras Públicas da Escola Nacional de Administração Pública (Enap), o professor da ENAP Vinicius Martins falou sobre boas práticas em pregão eletrônico e SRP. As perguntas foram elaboradas pelo professor da ENAP Rogério Colaço.5 páginasLogística e Compras Pública

Chemically crosslinked PVA hydrogels for cartilage substitution

Abstract in proceedings of the Fourth International Congress of CiiEM: Health, Well-Being and Ageing in the 21st Century, held at Egas Moniz’ University Campus in Monte de Caparica, Almada, from 3–5 June 2019.This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.info:eu-repo/semantics/publishedVersio

New Protic Ionic Liquids as Potential Additives to Lubricate Si-Based MEMS/NEMS

Funding Information: The work was financed by the Portuguese Foundation for Science and Technology (FCT) through the projects UIDB/00100/2020, UIDP/00100/2020 and IMS-LA/P/0056/2020 and through the PhD grant SFRH/BD/140079/2018 from Mariana Donato. Additionally, this work was financed by national funds from FCT in the scope of the projects UIDB/50022/2020 (IDMEC/LAETA) and LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication—i3N. Publisher Copyright: © 2023 by the authors.The motivation for this work was to develop new protic ionic liquids (PILs) as additives for the lubrication of micro and nanoelectromechanical systems (MEMS and NEMS). Ten PILs based on the combination of methylimidazolium ([MIMH]), 4-picolinium ([4-picH]), pyridinium ([PyrH]), 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium ([DBUH]) and tetramethylguanidinium ([TMGH]) cations with hydrogen sulfate([HSO4]) and mesylate ([MeSO3]) anions were tested as additives in polyethylene glycol (PEG200) to lubricate steel/silicon and silicon/silicon contacts. The best additive was [4-picH][HSO4], which adsorbed strongly on the Si surface, leading to a protective film that reduced wear by up to 15 times compared to PEG200.publishersversionpublishe

Diffusion-based design of multi-layered ophthalmic lenses for controlled drug release

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 parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses.info:eu-repo/semantics/publishedVersio

Chitosan nanogels for biomedical applications: choosing a suitable sterilization method

Poster presented at the 10th World Biomaterials Congress. Montreal, Canada, 17-22 May 2016N/

About the effect of eye blinking on drug release from pHEMA-based hydrogels: an in vitro study

"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 several potential advantages as compared with collyria. The main objective of this work is to study the effect of repetitive load and friction cycles caused by the eye blinking, on the drug release from hydrogels used in SCLs which, as far as we know, was never investigated before. Two poly-2-hydroxyethylmethacrylate based hydrogels, pHEMA-T and pHEMA-UV, were used as model materials. Levofloxaxin was chosen as model drug. The hydrogels were fully characterized in what concerns structural and physicochemical properties. PHEMA-UV revealed some superficial porosity and a lower short range order than PHEMA-T. We observe that the load and friction cycles enhanced the drug release from pHEMAUV hydrogels. The application of a simple mathematical model, which takes into account the drug dilution caused by the tear flow, showed that the enhancement of the drug release caused by blinking on this hydrogel may be relevant in in vivo conditions. Conversely, the more sustained drug release from pHEMA-T is not affected by load and friction cycles. The conclusion is that, depending on the physicochemical and microstructural characteristics of the hydrogels, blinking is a factor that may affect the amount of drug delivered to the eye by SCLs and should thus be considered.

Controlled drug delivery from ophthalmic lenses

Poster apresentado no Ciência 2016 – Encontro com a Ciência e Tecnologia em Portugal. Centro de Congressos de Lisboa, 4-6 julho 2016N/

Ocular drug delivery from contact lenses: mimetizing the hydrodynamic conditions of the eye

Poster presented at the 4th Congress on Innovation in Drug Delivery Site-Specific Drug Delivery (IDD2016). Antibes-Juan-les-Pins, France, 25-28 September 2016N/